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Large salt accumulations as a consequence of hydrothermal processes associated with ‘Wilson cycles’: A review, Part 2: Application of a new salt-forming model on selected cases

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The new hydrothermal salt model predicts that salt may accumulate in the sub-surface by hydrothermal circulation of seawater and brines in locations of high heat-flow. Such conditions are primarily found along tectonic plate boundaries, with processes of subduction and rifting, associated with the Wilson cycles. Modern knowledge of the physicochemical and thermodynamic properties of salt solutions at elevated pressures and temperatures, allows numerical modeling of fluid behavior at relevant conditions in the deep crust. This modeling shows how seawater that migrates down towards hot magma bodies in a rift situation (e.g. in the Red Sea) is subject to phase transitions, where low-saline (distilled) water vapor migrates out of the system, while still saltier brine continues to migrate further down towards the heat source, until solid salt precipitates. Similarly, in a subduction situation, the seawater confined in the subducting oceanic plate is subjected to an ever increasing pressure and temperature during the descent towards the mantle, which leads to similar phase behavior of the brine as in the rifting situation. The salts forming in the deep of a subduction zone are not readily transported up to the surface due to thick overburden of mantle- and crustal rocks. Hence, much of the salt formed during subduction remains hidden from human observation in the roots of the mountains. The formation of solid salt is therefore an inevitable process associated with the Wilson cycles, even without solar evaporation. Recent observations of thick carpets of mobile salt slurries on the Red Sea floor (Salt Flows) and huge accumulations of salts in the subsea/subsurface (Salt Walls and Salt Ridges), associated with topographic lows (Deeps), suggest that the Red Sea currently produces new volumes of brines and solid salts underground. The different solubilities of sea salts lead to a refining of the salt types. When reaching the seafloor, the warm brines are cooled down in brine pools, eventually becoming oversaturated with salts, which results in precipitation onto the seafloor. The dense brine layers protect seafloor salts from re-dissolution by normal seawater. Magmatic and volcanic processes associated with hydrothermal activity, e.g. connected to the subduction under the Andes Mountains are associated with enormous deposits of salts. The brines are transported hydrothermally up from the subduction zone and are venting out at 3500–4000 m above sea level. At the surface, the brines evaporate in the dry climate, which is also protecting the salt from re-dissolution. The brine feeding the hydrothermal systems above the subduction zone originates from dewatering of the subducting slabs. This water is causing fractional melting of the mantle wedge above, initiating volcanism. The hydrothermal water is also transporting salts to the surface, thus, explaining the close relationship between some types of volcanism and salt accumulations. It is assumed that this new understanding of hydrothermal salt formation will have a profound impact on interpretation of geological phenomena involving salt and salt formation, including the early development and behavior of salt basins.
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M. Hovland et al. Marine and Petroleum Geology xxx (2018) xxx-xxx
1. Introduction
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KI8EJGFIK LJL8CCP ?P;IFK?<ID8C GIF:<JJ<J KF 9I@E> K?< J8CKJ KF JFD< F9
J<IM89C< GFJ@K@FE 8J N<CC 8J ;<<G =8LCKJ K?8K 8I< FG<E <EFL>? KF =8:@C@
K8K< K?@J KI8EJGFIK
2.1. Oceanic - continental subduction and salts, the Andean subduction
zone
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F= 9FIFE 8E; C@K?@LD D8B< K?<J< J8CK ;<GFJ@KJ <M<E DFI< @EK<I<JK@E>
"FN N<I< K?< J8CKJ 9IFL>?K LG K?<I< 8E; N?8K GIF:<JJ<J :8LJ< K?< <E
I@:?D<EK F= 9FIFE 8E; C@K?@LD
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D@KJ JKI<K:?@E> LG KF 8IFLE; D 89FM< J<8 C<M<C ::FI;@E> KF &8D9
 .?< E;<J 'FLEK8@EJ 8I< 9L@CK 9P KNF ;@JK@E:K GIF:<JJ<J @E
K?< <8JK 9<E<8K? K?< 8JK<IE FI;@CC<I8 K?< :ILJK ?8J 9<<E ;FD@E8EKCP
K?@:B<E<; 9P JHL<<Q@E> D8B@E> K?< DFLEK8@EJ 8E; K?<@I IFFKJ #E K?<
N<JK 9<E<8K? K?< 1<JK<IE FI;@CC<I8 9FK? K?< JHL<<Q@E> F= FC; :ILJK
8E; K?< 8;;@K@FE F= DFCK<E IF:B =IFD K?< D8EKC< ?8J 9<<E 8 J@>E@=@:8EK
:8LJ< KF K?@J K?@:B<E@E>K K?< JL9;L:K@FE KI<E:? K?< J<;@D<EKJ 8I<
><E<I8CCP J:I8G<; FV 8E; G@C<; LG KF =FID 8E 8::I<K@FE8IP N<;><
0FC:8E@JD @J 8 :FDDFE =<8KLI< 89FM< JL9;L:K@FE QFE<J 8K GC8K< K<:
KFE@: 9FLE;8I@<J N?<I< F:<8E@: :ILJK @J ;<J:<E;@E> LE;<I :FEK@E<EK8C
:ILJK -KI8KFMFC:8EF<J 8I< :?8I8:K<I@Q<; 9P JK<<G GIFTC<J 8E; G<I@F;@:
<OGCFJ@M< <ILGK@FEJ ;L< KF ?@>? M@J:FJ@KP C8M8J F= 8E;<J@K@: :FDGFJ@
K@FE .?< ?@>? M@J:FJ@KP @J :8LJ<; 9P I<C8K@M<CP ?@>? J@C@:8 :FEK<EKJ 
N<@>?KG<I:<EK -@)X @E K?< C8M8 .?< MFC:8E@JD @J @E@K@8K<; 9P K?< I<
C<8J< F= N8K<I =IFD K?< JL9;L:K@E> GC8K< N?@:? CFN<IJ K?< D<CK@E> GF@EK
F= K?< FM<ICP@E> D8EKC< IF:B  G8IK@8C D<CK@E> F::LIJ N?@:? GIF;L:<J
D8>D8 K?8K I@J<J ;L< KF CFN<I ;<EJ@KP K?8E K?< JLIIFLE;@E> IF:BJ  @>
 @E "FMC8E; <K 8C 
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K?<I GIF:<JJ<J .?@J N8K<I @J @E K?< =FID F= =I<< N8K<I 9I@E< :IPJK8C
N8K<I 8E; ?P;IFOPC >IFLGJ 8JJF:@8K<; N@K? D@E<I8CJ C@B< :C8PJ 8E; J<I
G<EK@E@K<J 1?<E K?@J D8>D8 I@J<J K?IFL>? K?< :ILJK DFI< J@C@:8 I@:?
IF:BJ 8I< D@O@E> @EKF K?< D8>D8 GIF;L:@E> K?< 8E;<J@K@: :FDGFJ@K@FE
K?8K :?8I8:K<I@Q<J K?@J MFC:8E@: I<>@FE 1?<E K?< D8>D8 I<8:?<J K?<
JLI=8:< K?< CFN<I<; GI<JJLI< 8CCFNJ K?< MFC8K@C<J :FETE<; @E K?< C8M8 KF
<J:8G< @E 8 I8G@; JFD<K@D<J <OGCFJ@M< D8EE<I .?< D8@E MFC8K@C<J 8I<
N8K<I M8GFI 8E; )X 9LK FK?<I >8J<J 8I< 8CJF :FDDFE C@B< -)X "X-
CX (X "< I 8E; ,E .?< <OGCFJ@M< <ILGK@FEJ :I<8K< 8 C8E;J:8G< ;FD
@E8K<; 9P ?8I;<E<; C8M8 8E; MFC:8E@: 8J? KLV &8D9 
@>  @CCLJKI8K<J K?< <==<:KJ F= JL9;L:K@E> JC89 ;@G>I8;@<EK N@K?
F::LII<E:< F= 8:K@M< MFC:8EF<J 1?<I< K?< ;FNE>F@E> JC89 @J ;@GG@E>
JK<<GCP <> ° K?<I< 8I< 8:K@M< MFC:8EF<J 8E; 9CF:B =8LCK LGC@=K
8::FI;@E> KF !LKJ:?<I <K 8C   #E 8;;@K@FE N< TE; K?8K
K?< @E:I<8J<; ?<8KUFN 8E; F::LII<E:< F= M<IK@:8C =I8:KLI@E> 8E; =8LCK
@E> C<8;J KF JLI=8:< J8CK ;<GFJ@K@FE DFJK ;I8D8K@:8CCP @CCLJKI8K<; 9P K?<
GI<J<E:< F= -8C8I ;< /PLE@ K?< C8I><JK J8CK C8B< FE 8IK? J<<E 8J K?<
N?@K< G8K:? -;/ FE K?< C<=K D8G F= @> 
8J<; FE :FE;L:K@M@KP D<8JLI<D<EKJ &8LDFE@<I <K 8C  <JK@
D8K<; K?< MFCLD< F= 9I@E<J @E K?< IF:BJ 9<E<8K? FE< F= K?< E;<8E
JKI8KFMFC:8EF<J K?< /KLILE:L MFC:8EF FE K?< FC@M@8E CK@GC8EF .?<
GFIFJ@KP N8J <JK@D8K<; KF 8GGIFO@D8K<CP  F= K?< KFK8C IF:B MFC
LD< 8DFLEK@E> KF 8 9I@E< MFCLD< F=  D@CC@FE :L9@: BD 9<E<8K? K?@J
MFC:8EF 8CFE< .?< MFC:8EF @J CF:8K<; JFLK? F= &8B< /PLE@  @> 
UNCORRECTED PROOF
M. Hovland et al. Marine and Petroleum Geology xxx (2018) xxx-xxx
Fig. 1. Left )VJ?FI< 8E; FEJ?FI< JLI=8:< KFGF>I8G?P F= G8IKJ F= K?< E;<J JL9;L:K@FE QFE< .?< KNF 9IFB<E C@E<J ;<C@D@K8K< K?< I<>@FE F= K?< CK@GC8EF N?<I< K?< JL9;L:K@FE JC89 J@EBJ
8K 8E 8E>C< F= °FI DFI< .F K?< JFLK? 8E; EFIK? F= K?<J< C@E<J K?< JL9;L:K@FE JC89 @J D<I<CP U8K N@K? 8E 8E>C< F= C<JJ K?8E ° -;/ -8C8I ;< /PLE@ &. &8B< .@K@:8:8 $ , $L8E
<IE8E;<Q ,@;>< (,  (8Q:8 ,@;>< '8G GIF;L:<; N@K? !<F'8G8GG 8E; !FF>C< 8IK? Right -@DGC@T<; D8G F= -FLK? D<I@:8 @CCLJKI8K@E> K?< F::LII<E:< F= ?@JKFI@:8CCP 8:K@M< MFC
:8EF<J TCC<; 8E; FG<E I<; KI@8E>C<J (FK< K?< KNF 8I<8J F= U8K JL9;L:K@FE - N@K?FLK ?@JKFI@:8CCP 8:K@M< MFC:8E@JD ' 48E; ( 48I< K?< '<E;8ñ8 8E; K?< (8Q:8 8LCK 4FE<J
I<JG<:K@M<CP D<EK@FE<; @E K?< K<OK 8E; @E FK?<I T>LI<J .?< >I<<E I<:K8E>C< J?FNJ K?< FLKC@E< F= K?< C<=K @D8>< '8G 98J<; FE -@DB@E 8E; -@<9<C  -<< K<OK =FI =LIK?<I ;@J:LJJ@FE
 FI @EK<IGI<K8K@FE F= K?< I<=<I<E:<J KF :FCFI @E K?@J T>LI< C<><E; K?< I<8;<I @J I<=<II<; KF K?< 1<9 M<IJ@FE F= K?@J 8IK@:C<
::FI;@E> KF %8N8DFKF <K 8C  K?< N8K<I @E K?< C8M8 @J :?8I
8:K<I@Q<; 9P ?8M@E> ?@>? J8C@E@KP @E K?< FI;<I F=  N<@>?KG<I:<EK .?<P
8CJF GF@EK FLK K?8K J8C@E< UL@;J ?8M< K?< :8G8:@KP F= C<8:?@E> DFI< D<K
8CJ =IFD K?< ?FJK IF:B K?8E GLI< N8K<I N?@:? ?8J 8E @DG8:K FE K?<
:?<D@JKIP F= 9FK? 9I@E<J 8E; IF:BJ %8N8DFKF <K 8C 
J K?< JL9;L:K@E> 9I@E<J8KLI8K<; F:<8E@: JC89 DFM<J ;FNEN8I;J
K?< GI<JJLI< 8E; K<DG<I8KLI< @E:I<8J<J :FEK@ELFLJCP 8E; K?< K<:KFE@:
8E; UL@; GI<JJLI<J @E;L:< =8LCK@E> 8E; =I8:KLI@E> F= K?< FM<I9LI;<E
K?LJ 8CCFN@E> KI8EJ=<I F= UL@;J 9I@E<J =IFD K?< F:<8E@: JC89 KF K?<
C@K?FJG?<I< LGG<I D8EKC< 4<CCD<I <K 8C  @> @E "FMC8E; <K
8C  K 89FLK BD ;<GK? K?< K<DG<I8KLI< F= K?< LGG<I G8IK F=
K?< JC89 ?8J @E:I<8J<; KF DFI< K?8E ° K?< K<DG<I8KLI< N?<I< J<8
N8K<I 9<:FD<J JLG<I:I@K@:8C 8E; G?8J< :?8E><J K8B< GC8:< N@K? K?< =FI
D8K@FE F= JLG<I:I@K@:8C N8K<I M8GFI ;<EJ@KP  >:DXW GI<:@G@K8K@FE
F= JFC@; J8CK 8E; ?@>?<I ;<EJ@KP 9I@E<J .?< CFN ;<EJ@KP N8K<I M8GFI 8E;
C@HL@; N8K<I N@CC D@>I8K< LGN8I;J KF><K?<I N@K? DFCK<E IF:BJ 8E; @E@K@
8K< ?P;IFK?<ID8C GIF:<JJ<J 8E; MFC:8E@JD -L:? M<IK@:8C KI8EJGFIK JPJ
K<DJ =FI ?P;IFK?<ID8C UL@;J ?8M< 9<<E ;F:LD<EK<; 9P D<J?<J F= :<
D<EK<; M<@EJ @E <IF;<; QFE<J F= K?< E;<J ,FHL<K <K 8C  LI
K?<I ;FNE 8K <M<E ?@>?<I K<DG<I8KLI<J 8E; GI<JJLI<J K?< J8CK @E K?<
9I@E< :FETE<; @E K?< JC89 N@CC GI<:@G@K8K< 8J JFC@; J8CK 8E; =FCCFN K?<
JL9;L:K@E> JC89 ;<<G<I ;FNE @EKF K?< D8EKC< *8IK@:LC8K< JFC@; J8CK D8P
8CJF D@O @EKF K?< D8>D8 89FM< K?< F:<8E@: JC89 KF 9<:FD< G8IK F= K?<
MFC:8E@: IF:BJ
2.1.1. Flat subduction beneath parts of the Andes
 :CL< KF LE;<IJK8E;@E> K?< F::LII<E:<J F= ?P;IFK?<ID8C J8CKJ @E
K?< E;<8E 'FLEK8@EJ @J K?< :FE:<GK F= U8K 8E; JK<<G JL9;L:K@FE #E
K?< I<>@FEJ F= JK<<G JL9;L:K@FE K?< F:<8E@: JC89 ;<J:<E;J KFN8I;J K?<
D8EKC< 8K 8E 8E>C< F= ° N?@C< K?< F:<8E@: JC89J K?8K LE;<I>F U8K
JL9;L:K@FE ;<J:<E; KF 8 ;<GK? F= 8IFLE;  BD 9<=FI< K?<P =FCCFN 8
JL9?FI@QFEK8C G8K? !LKJ:?<I <K 8C  #E K?@J C8KK<I J@KL8K@FE K?<
JPJK<D @J :FFC<; 8E; EF IF:B D<CK@E> K8B<J GC8:< @E K?< LGG<I :FEK8:K
QFE< 9<KN<<E K?< JC89 8E; K?< :FEK@E<EK8C C@K?FJG?<I< ?<E:< EF @E@K@8
K@FE F= MFC:8E@JD .?@J <==<:K KF><K?<I N@K? K?< JKI<E>K?<E@E> F= K?< LG
G<I C@K?FJG?<I< @J 8CJF @DG<;@E> K?< ;<M<CFGD<EK F= ?P;IFK?<ID8C :@I:L
C8K@FE F= 9I@E<J FEJ<HL<EKCP EF J@>E@=@:8EK MFCLD<J F= J8CK =FID8K@FE
8I< F9J<IM<; @E K?< 8I<8J F= U8K JL9;L:K@FE
#E @>  K?< =I<J?N8K<I &8B< .@K@:8:8 @J J<<E EFIK? F= -8C8I ;<
/PLE@ @E K?< 8I<8 :?8I8:K<I@Q<; 9P U8K JL9;L:K@FE <IIF:8C 8E;
<IE8E;<Q  (F MFC:8E@JD 8E; DL:? C<JJ ?P;IFK?<ID8C 8:K@M@KP
@J J<<E N@K?@E K?< GI<:@G@K8K@FE:8K:?D<EK 8I<8 F= &8B< .@K@:8:8 :
:FI;@E> KF <IIF:8C 8E; <IE8E;<Q  U8K JL9;L:K@FE F= K?< *8:@T:
(8Q:8 GC8K< F::LIJ 9<KN<<E °- 8E; °- 8CFE> K?< EFIK?<IE 8E; :<E
KI8C I<>@FEJ F= *<IL FM<I 8 I<>@FE D<8JLI@E>  × BDX .?@J 8I<8
@J 8JJF:@8K<; N@K? CFN C<M<CJ F= J<@JD@: 8:K@M@KP 8K ;<GK?J 9<KN<<E 
8E; BD
@>  #CCLJKI8K<J ?FN K?< JL9;L:K@E> JC89 8CK<IJ @KJ ;@G 8::FI;@E>
KF 9LFP8E:P 8E; FK?<I G8I8D<K<IJ 8::FI;@E> KF !LKJ:?<I <K 8C 
.?< G<IJG<:K@M< JB<K:? @CCLJKI8K<J K?< ><FD<KIP F= K?< (8Q:8 *C8K<
8E; K?< KNF 9LFP8EK I@;><J <8:? ?FC;@E> LG 8  BD CFE> J<:K@FE F= K?<
JL9;L:K@E> (8Q:8 *C8K< N@K? 8 J8> @E 9<KN<<E <:8LJ< K?<I< @J 8 JK<<GCP
;@GG@E> JC89 E<OK KF K?< (8Q:8 8LCK 4FE< K?<I< @J 8CJF <OKI8 ?<8K 8E;
UL@;J UFN@E> KF K?< JLI=8:< :8LJ@E> J8CK ;<GFJ@KJ FE K?< :LII<EK <8IK?
JLI=8:< 89FM< K?@J CF:8K@FE
.?< U8K JL9;L:K@FE KI8EJ@K@FEJ @EKF JK<<G JL9;L:K@FE FE K?< <8JK<IE
J@;< F= K?< E;<J !LKJ:?<I <K 8C  .?8K @J N?P N< TE; MFC:8EF<J
?FK JGI@E>J 8E; J8C8IJ @E (FIK?<IE I><EK@E8 <JG<:@8CCP @E K?< I<>@FE
9<KN<<E -8EK@8>F ;<C JK<IF 8E; 8K8D8I:8 @E K?< EFIK? 8E; FI;F98
@E K?< JFLK?
-@D@C8ICP U8K JL9;L:K@FE F= K?< (8Q:8 GC8K< 8CJF F::LIJ =LIK?<I
JFLK? 9<E<8K? :<EKI8CEFIK?<IE ?@C< 9<KN<<E °- 8E; °- FM<I
8 I<>@FE D<8JLI@E> BD× BDX N?@:? @J 8CJF 8JJF:@8K<; N@K?
CFN J<@JD@: 8:K@M@KP #E K?@J 8I<8 K?<I< @J FECP D@EFI MFC:8E@: 8:K@M@KP
UNCORRECTED PROOF
M. Hovland et al. Marine and Petroleum Geology xxx (2018) xxx-xxx
Fig. 2. #CCLJKI8K@FE F= JK<<G 8E; U8K JL9;L:K@FE @E K?< E;<J DF;@T<; =IFD !LKJ:?<I <K 8C  .?< G<IJG<:K@M< JB<K:? @CCLJKI8K<J K?< GIFGFJ<; DF;<C M@<N CFFB@E> N<JK N@K? K?<
(8Q:8 *C8K< 8E; K?< KNF 9LFP8EK I@;><J <8:? ?FC;@E> LG 8  BD CFE> J<:K@FE F= K?< JL9;L:K@E> (8Q:8 *C8K< N@K? 8 J8> @E 9<KN<<E
<IIF:8C 8E; <IE8E;<Q  .?< I<>@FE 9<KN<<E K?<J< KNF QFE<J
F= U8K JL9;L:K@FE @J N?<I< K?< CK@GC8EF * I<>@FE @J CF:8K<; N?@:?
8CJF @E:CL;<J -8C8I ;< /PLE@ ::FI;@E> KF @I;  K?<I< 8I< J<M<I8C
:FDG<CC@E> I<8JFEJKF ;<J@>E8K< K?< I<>@FEJ EFIK? 8E; JFLK? F= K?< C
K@GC8EF 8J FIF><EJ N@K? U8K JL9;L:K@FE )E< F= K?<J< I<8JFEJ @J K?8K
#= K?<J< U8EB@E> I<>@FEJ N<I< I@>@; G8IKJ F= - -FLK? D<I@:8 K?<E
K?<I< NFLC; E<:<JJ8I@CP 9< KI8EJ=FID FI KI8EJK<EJ@FE8C 9FLE;8I@<J 9<
KN<<E * 8E; - KF 9FK? K?< EFIK?N<JK 8E; JFLK? F= * 9LK EF J@>E F=
JL:? 9FLE;8I@<J @J J<<E @E K?< J<@JD@:@KP FI ><FCF>P@I; 
@> @CCLJKI8K<J ?FN U8K JL9;L:K@FE JFLK? F= °- KI8EJC8K<J @EKF
JK<<G JL9;L:K@FE 8IFLE; BD @EC8E; 8::FI;@E> KF !LKJ:?<I <K 8C
 .?< KI8EJ=FID8K@FE KF 8 JK<<GCP ;@GG@E> JC89 ?8J :FEJ<HL<E:<J
=FI  K?< ?<8KUFN 8E; 9<:8LJ< F= 8JJF:@8K<; CF:8C 9CF:B=8LCK LGC@=K
 8M8@C89C< M<IK@:8C :FE;L@KJ 8CFE> =8LCKJ =FI UL@;J KF D@>I8K< LG KF
JLI=8:< ::FI;@E> KF !LKJ:?<I <K 8C  .?< K?<ID8C <==<:K @J 9<JK
@CCLJKI8K<; 9P ?<8K UFN F9J<IM8K@FEJ =IFD *<IL 8E; FC@M@8 "@>? ?<8K
UFN F= D1DX @J GI<J<EK 89FM< K?< JK<<G JC89 @E FC@M@8 FN
@E> KF K?< LE;<ICP@E> 8JK?<EFJG?<I< N?<I<8J 89FM< K?< *<IL U8K JC89
N?<I< K?< 8JK?<EFJG?<I< @J 89J<EK CFN =FI<8I:M8CL<J F=  D1
DX 8I< F9J<IM<; LG KF BD =IFD K?< KI<E:?
#E @>  @K :8E 9< J<<E K?8K K?< J8CK G8EJ 8I< CF:8K<; N?<I< K?< U8K
JL9;L:K@FE KI8EJC8K<J @EKF JK<<G JL9;L:K@FE 8::FI;@E> KF K?< DF;<C F=
!LKJ:?<I <K 8C  .F K?< N<JK F= K?@J CF:8K@FE K?<I< 8I< EF 8:K@M<
MFC:8EF<J 8E; EF J8C8IJ FI J8C@E8J F= J@>E@=@:8E:< )E< GFJJ@9@C@KP @J
K?< I8@E J?8;FN <==<:K I<C8K<; KF K?< ?@>? 8CK@KL;< F= K?< E;<8E 'FLE
K8@EJ N?@:? :FEJK@KLK<J 8 98II@<I =FI ?LD@;@KP C8E;N8I;J F= K?< DFLE
K8@E :?8@E :FE:<EKI8K@E> K?< ?LD@;@KP F:<8EN8I;J F= K?< ?@>? 8CK@KL;<J
CK<IE8K@M<CP K?<I< @J 8 GFJJ@9@C@KP K?8K MFC:8E@:I<C8K<; 9I@E<J @E K?<
JL9JLI=8:< F::LI FECP N?<I< =8LCKJ :FDDLE@:8K< :FE:<EKI8K<; 9I@E<J KF
K?< JLI=8:< N?<I< K?< N8K<I @J <M8GFI8K<; 8E; J8CKJ 8I< GI<:@G@K8K<;
LIK?<IDFI< @E 8>I<<D<EK N@K? !LKJ:?<IJ ;@8>I8D  @>  K?<I<
@J <M@;<E:< F= JLI=8:< ;@JILGK@FE N?<I< K?< J8C@E8J F::LI .?<P JL>><JK
K?8K K?< F9J<IM<; JLI=8:< ;@JILGK@FE N?<I< K?< JC89 @J ;@GG@E> JK<<GCP @J
:8LJ<; 9P KI8EJ:LII<EK =8LCK@E> 8E; 9CF:B =8LCK LGC@=K@E>!LKJ:?<I <K
8C 
.F K?< <8JK F= K?< J8C@E8J @J 8 C8I>< =I<J? N8K<I C8B< EFK 8==<:K<; 9P
K?< ?P;IFK?<ID8C GIF:<JJ<J .?@J @E;@:8K<J K?8K UL@;J :8LJ@E> K?< J8C@E8J
8I< <D@KK@E> 8K K?< JLI=8:< FECP N?<I< K?< JC89 @J JK<<GCP ;@GG@E> J<<
8CJF GI<M@FLJ T>LI< -@D@C8ICP =LIK?<I EFIK? .F K?< <8JK F= &8B< .@K@
:8:8  @>  N?<I< K?< JC89 @J JK<<GCP ;@GG@E> J<M<I8C G<:LC@8ICP CFFB
@E> 8CB8C@E< C8B<J F::LI .?<P 8I< CF:8K<; 8K K?< I@>?K ;@JK8E:< =IFD
K?< KI<E:? .?@J I<>@FE ?FN<M<I ;F<J EFK ?8M< K?< 8I@; :FE;@K@FEJ F=
K?< 8I<8 J?FNE @E @>  8E; K?<I<=FI< 8EP ?P;IFK?<ID8C J8CKJ 8;;<;
KF K?< JLI=8:< NFLC; C@B<CP 9< ;@CLK<; 9P D<K<FI@: N8K<I @E K?< C8B<J
2.1.1.1. Mantle processes evidenced by helium anomalies .?< ?<C@LD
C<8B8>< =IFD K?< JL9JLI=8:< :8E 9< LJ<; 8J 8 KFFC KF =FCCFN D8EKC<8J
JF:@8K<; GIF:<JJ<J @E K?< ;<<G .?< I8K@F F= X"< KF X"< @J 8IFLE; 
D@CC@FE @E K?< 8IK?J :ILJK  D@CC@FE @E K?< 8KDFJG?<I< 8E;  D@C
C@FE @E K?< D8EKC< &8D9  ;<J:I@9<J 8E <8JKN<JK GIFTC< 8:IFJJ
K?< E;<J JK8IK@E> FLK N@K? M<IP CFN GIFGFIK@FEJ F= X"< 8K K?< *8:@T:
:F8JK @E;@:8K@E> K?8K K?< :ILJK @J K?< JFLI:< F= K?< ?<C@LD 1?<E 8G
Fig. 3. #CCLJKI8K@FE F= K?< KI8EJ@K@FE =IFD U8K JL9;L:K@FE KF JK<<G JL9;L:K@FE CF:8K<; 89FLK BD =IFD K?< JL9;L:K@FE KI<E:? DF;@T<; =IFD @>  @E !LKJ:?<I <K 8C  .?@J
JC89 :FET>LI8K@FE F::LIJ KF K?< EFIK? <8JK F= -@<II8J *8DG<8E8J 8IFLE; °–°- @E K?< E;<J (FK< K?< JLI=8:< ;@JILGK@FE 8E; ;<<GJ<8K<; =8LCKJ 89FM< K?< JK<<G<E@E> JC89
UNCORRECTED PROOF
M. Hovland et al. Marine and Petroleum Geology xxx (2018) xxx-xxx
Fig. 4. -8K<CC@K< @D8>< =IFD K?< 8I<8 F= -FLK? D<I@:8 @CCLJKI8K<; @E @>  89FM< <KN<<E  BD 8E;  BD =IFD K?< JL9;L:K@FE KI<E:? 8E; 9<KN<<E °8E; °- J<M<I8C J8CKG8EJ
8I< M@J@9C< -&-8C@E8 &8 EK@>L8 -!-8C@E8J !I8E;<J óI;F98 -;' -8C@E8J ;< '8:8J@E 8E; *;C- *8DG8 ;< C8J -8C@E8J <:8LJ< K?<I< 8I< EF J@>E@=@:8EK J8C@E8J KF K?< N<JK F=
-& @E K?< EFIK? 8E; -;' @E K?< JFLK? @K @J C@B<CP K?8K K?< JK<<GCP ;@GG@E> GFIK@FE F= K?< JC89 @J JK@DLC8K@E> K?< =FID8K@FE F= K?<J< J8C@E8J 8J ;@J:LJJ<; @E K?< K<OK #D8>< GIF;L:<; N@K?
!FF>C<8IK?
GIF8:?@E> K?< MFC:8EF<J F= K?< 1<JK<IE FI;@CC<I8 K?< ?<C@LD >8J 9<
:FD<J I@:?<I @E X"< @E;@:8K@E> D8EKC< JFLI:<; >8J FM<I  F= K?< ?<
C@LD GIF;L:<; 9P K?< MFC:8EF<J 8E; ?FK JGI@E>J 8JJF:@8K<; N@K? K?< MFC
:8EF<J @J K?LJ :FD@E> =IFD K?< D8EKC< &8D9 
LIK?<IDFI< 8 J@>E@=@:8EK 8DFLEK F= K?< ?<C@LD >8J <D@KK@E> =IFD
?FK JGI@E>J @E K?< CK@GC8EF 8E; N<JK<IE D8I>@E F= K?< 8JK<IE
FI;@CC<I8 LG KF BD <8JK F= K?< >I<8K :?8@E F= MFC:8EF<J N8J 8CJF
JFLI:<; =IFD D8EKC< IF:BJ &8D9  .?@J @E;@:8K<J D8EKC<N8K<I
@EK<I8:K@FEJ @E 8 M8JK I<>@FE LE;<I K?< E;<J 'FLEK8@EJ 8J 8 I<JLCK
F= ;<N8K<I@E> F= K?< JL9;L:K@FE JC89J 8J @CCLJKI8K<; 9P 4<CCD<I <K 8C
  @> @E "FMC8E; <K 8C  .?< N8K<ID8EKC< @EK<I8:K@FE
;I@M<J K?< ?P;IFK?<ID8C GIF:<JJ<J K?8K D8E@=<JK K?<DJ<CM<J FE K?< JLI
=8:< N@K? MFC:8E@JD 8E; K?< M<EK@E> F= JK<8D 8E; ?FK JGI@E>J @JJL@E>
9I@E<J @EKF K?< J8CK C8B<J
2.1.2. Accumulation and re>ning of salts
IFD K?< 89FM< <M@;<E:< 8E; I<8JFE@E> @K @J :FE:CL;<; K?8K K?< ?P
;IFK?<ID8C <G@K?<ID8C 9I@E<J @JJL@E> =IFD K?< 8IK<J@8E JGI@E>J 8I< K?<
JFLI:<J F= K?< ?L>< D8JJ<J F= J8CKJ ;<GFJ@K<; @E K?< E;<J 'FLEK8@EJ
*@I8AEF  4<CCD<I <K 8C  .?< ;I@M@E> =FI:<J 8I< ;<<GCP ><E
<I8K<; FM<IGI<JJLI<; UL@;J 8JJF:@8K<; N@K? ;<N8K<I@E> F= K?< JL9;L:K
@E> F:<8E@: :ILJK 8E; K?< I<JLCK@E> MFC:8E@: 8:K@M@KP @E K?< 8I<8
.?< <O:<JJ F= JF;@LD 8E; :?CFI@;< J<<E @E .89C<  =FI J@O F= K?< D8
AFI J8CK 8::LDLC8K@FEJ @E K?< <EKI8C E;<J :C<8ICP GF@EKJ 8K 8 D8I@E<
FI@>@E F= K?< J8CK ;<GFJ@KJ .?< DFJK I<8JFE89C< <OGC8E8K@FE =FI K?< ;<
GFJ@K@FE F= K?<J< J8CKJ 8K DFI< K?8E  D 8CK@KL;< @J ?P;IFK?<ID8C
KI8EJGFIK8K@FE =IFD K?< JL9;L:K@FE QFE< 8JJF:@8K<; N@K? MFC:8E@JD
.?< TE8C G?8J< F= :FE:<EKI8K@E> K?< 9I@E<J @EKF JFC@; J8CKJ @J ;L< KF ;IP
@E> FLK @E 8 GI<M8@C@E> ;IP :C@D8K< .?@J ;IP :C@D8K< @J 8CJF GIFK<:K@E>
K?< J8CK =IFD 9<@E> N8J?<; FLK .89C<  J?FNJ K?8K GFK8JJ@LD 8E; D8>
E<J@LD M8CL<J 8I< 8CJF DL:? KFF ?@>? :FDG8I<; KF J<8N8K<I 8E; JF @J
JLCG?8K< .?<J< ?@>? M8CL<J KF><K?<I N@K? ?@>? :FEK<EKJ F= 9FIFE 8E;
C@K?@LD 8I< K<CC@E> 8 JKFIP 89FLK J8CK I<TE@E> 8E; N8K<IIF:B @EK<I8:
K@FEJ JK8IK@E> N@K? J<8N8K<I 9IFL>?K ;FNE @E K?< JL9;L:K@FE QFE<
8I<=LC <O8D@E8K@FE F= K?< JLI=8:< F= -8C8I ;< /PLE@ 8:KL8CCP J?FNJ
K?8K K?<I< 8I< K?FLJ8E;J F= J<<G8>< =<8KLI<J FE K?< J8CK G8E JLI=8:<
J<<E 8J :FE:<EKI@: JKIL:KLI<J <8:? I<GI<J<EK@E> GF@EKJFLI:<J F= 8IK<
J@8E 9I@E< UFN  @>  $L;; 8E; "FMC8E;  .?<J< =<8KLI<J @E;@
:8K< K?8K K?< J8CK C8B< @J 9<@E> =<; 9P 8IK<J@8E 9I@E<J =IFD 9<CFN N?@:?
<M<EKL8CCP ;IP FLK 9P <M8GFI8K@FE @E K?< 8I@; :C@D8K< C<8M@E> K?<@I J8CK
:FEK<EKJ FE K?< 9FKKFD F= K?< C8B<
1?<E K?< 8IK<J@8E 9I@E<J :FEK8@E DFI< K?8E FE< KPG< F= J8CK N@K? ;@=
=<I<EK JFCL9@C@K@<J 8K K?< GI<M8@C@E> K<DG<I8KLI<J F= K?< C8B< K?< C<JJ
JFCL9C< J8CK N@CC GI<:@G@K8K< TIJK N?@C< K?< DFJK JFCL9C< J8CK N@CC GI<:@G
@K8K< C8JK K?LJ :8LJ@E> 8 I<TE@E> 8E; C8P<I@E> F= K?< ;<GFJ@K<; J8CKJ
<:8LJ< K?< 8J:<E;@E> UL@;J 8I< G8JJ@E> K?IFL>? @EK<IM8CJ N@K? ;<
:I<8J@E> K<DG<I8KLI<J 8E; GI<JJLI<J N?@:? ;<K<ID@E< K?< JFCL9@C@KP F=
K?< J8CKJ I<TE@E> F= J8CKJ @J <OG<:K<; KF 9< 8 :FEK@ELFLJ GIF:<JJ =IFD
Table 1
?<D@:8C 8E8CPJ<J @E GGD F= J<C<:K<; 9I@E<J =IFD -8C8IJ @E K?< :<EKI8C E;<J -F;@LD :?CFI@;< @J K?< ;FD@E8EK J8CK GF@EK@E> KF 8 D8I@E< FI@>@E F= K?< <M8GFI@K<J .?< <M8GFI@K<J 8I<
JKIFE>CP <EI@:?<; @E &@K?@LD 8E; FIFE I@:BJ<E  18II<E 
K8:8D8 /PLE@ "'L<IKF <C,@E:FE DG<O8 J:FK8E
C      
-)X      
")X   E; E;  
X)X      
&@      
(8      
%      
'>      
8      
.-      
UNCORRECTED PROOF
M. Hovland et al. Marine and Petroleum Geology xxx (2018) xxx-xxx
Fig. 5. Left (LD<IFLJ J<<G8>< =<8KLI<J 8I< =FLE; @E K?< :<EKI8C GFIK@FE F= &8B< /PLE@ I<; I<:K8E>C< .?< MFC:8EF J<<E KF K?< EFIK? @J K?< ;FID8EK .LELG MFC:8EF 8CJF @D8><; @E @> 
Right .?<I< 8I< 8K C<8JK KNF KPG<J F= =<8KLI<J JD8CC GF:BD8IBJ FI :@I:LC8I ;<GI<JJ@FEJ 8E; C8I><I <CC@GK@:8C :FE:<EKI@: @DGI@EKJ .?<P GIF989CP I<JLCK =IFD GLCJ8K@E> J<<G8>< F= 9I@E<J
N?@:? GI<:@G@K8K< J@DLCK8E<FLJCP C<8M@E> 8 :FE:<EKI@: G8KK<IE FK? @D8><J GIF;L:<; N@K? !FF>C<8IK?  FI @EK<IGI<K8K@FE F= K?< I<=<I<E:<J KF :FCFI @E K?@J T>LI< C<><E; K?< I<8;<I @J
I<=<II<; KF K?< 1<9 M<IJ@FE F= K?@J 8IK@:C<
Fig. 6. Left *<IJG<:K@M< @D8>< F= .LELG MFC:8EF CF:8K<; FE K?< EFIK?<IE <;>< F= -8C8I ;< /PLE@  @>  C<=K @D8>< .?< C8B< 8E; MFC:8EF @J M@<N<; =IFD 8E <C<M8K@FE F= BD Right
EC8I><; ;<K8@C =IFD K?< =FFK F= .LELG MFC:8EF .?< @D8>< :C<8ICP J?FNJ K?8K N8K<I @J ;I8@E@E> =IFD JGI@E>J 8IK<J@8E <G@K?<ID8C N8K<I 9CL< 8E; P<CCFN 8IIFNJ 8K K?< =FFK F= K?< MFC:8EF
#D8>< GIF;L:<; N@K? !FF>C<8IK?  FI @EK<IGI<K8K@FE F= K?< I<=<I<E:<J KF :FCFI @E K?@J T>LI< C<><E; K?< I<8;<I @J I<=<II<; KF K?< 1<9 M<IJ@FE F= K?@J 8IK@:C<
K?< JL9;L:K@FE QFE< 8E; LG KF K?< JLI=8:< #K @J K?<I<=FI< <OG<:K<; K?8K
C8I>< 8::LDLC8K@FEJ F= 9I@E<J 8E; J8CKJ 8I< ?@;;<E @E K?< IF:B :FCLDE
9<CFN K?< M@J@9C< J8CK 8::LDLC8K@FEJ FE K?< JLI=8:<
#E @>  K?< EFIK?<IE G8IK F= -8C8I ;< /PLE@ @J J<<E KF><K?<I N@K?
K?< ;FID8EK .LELG MFC:8EF .?< JLDD@K F= K?@J MFC:8EF @J 8K  D
N?<I<8J K?< J8CK C8B< @J 8K 8E <C<M8K@FE F= D .?<P 8CC ;I8@E @EKF
-8C8I ;< /PLE@ 8E; :FEKI@9LK< KF K?< 8::LDLC8K@FE F= 9I@E<J 8E; J8CKJ
CJF GF:BD8IBJ @< J?8CCFN :@I:LC8I ;<GI<JJ@FEJ 8I< J<<E .?<P @E;@
:8K< GLCJ8K@E> 8IK<J@8E :FE;@K@FEJ @E K?< >IFLE;N8K<I F= K?< 8I<8 $L;;
8E; "FMC8E;  .?< @D8>< :C<8ICP @E;@:8K<J 8E 8IK<J@8E >IFLE;N8
K<I JPJK<D 8CFE> K?< 98J< F= .LELG MFC:8EF 8E; GIF989CP 8CJF 8CFE> K?<
98J< F= K?< FK?<I MFC:8E@: JKIL:KLI<J JLIIFLE;@E> -8C8I ;< /PLE@
2.1.3. Lithium and boron salts
CFEJF  GIFM@;<; 8 K?FIFL>? I<M@<N F= K?< FI@>@E F= K?< C8I><
9FI8K< ;<GFJ@KJ @E I><EK@E8 8E; ?< <JG<:@8CCP 8;;I<JJ<; K?< <E;FI?<@:
CK@GC8EF*LE8 GC8K<8L 8K <C<M8K@FEJ 8M<I8>@E> D  @>  .?<
*LE8 GC8K<8L 8I<8 N?<I< K?< 9FI;<IJ F= I><EK@E8 FC@M@8 8E; ?@C<
D<<K 8E; 8I< 9FLE;<; 9P K?< -8C8I ;< K8:8D8 K?< -8C8I ;< /PLE@ 8E;
K?< -8C8I ;< "FD9I< 'L<IKF @J F=K<E I<=<II<; KF 8J K?< &@K?@LD .I@8E
>C<8E; K?< K?I<< :FLEKI@<J D<EK@FE<; 8I< K?< &@K?@LD J
FIFE  8E; C@K?@LD &@ 8I< MFC8K@C< 8E; DF9@C< <C<D<EKJ F:
:LII@E> D8@ECP @E CFN :FE:<EKI8K@FEJ 8E; ?@>?CP ;@JG<IJ<; @E E8KLI<
18II<E  -<8N8K<I :FEK8@EJ GGD  8E;  GGD &@ N?@C< K?<
8IK?J :ILJK :FEK8@EJ GGD 8E;  GGD &@ 9P N<@>?K FIFE
@J DFJKCP =FLE; @E E8KLI< 8J =LCCP FO@;@Q<; 9FI8K<J N?@C< C@K?@LD @J
8CJF =FLE; @E JFD< J@C@:8K< D@E<I8CJ <> JGF;LD<E< G<K8C@K< C<G@;F
C@K< 8E; ?<:KFI@K< #E K?< E;<J 'FLEK8@EJ K?< C8I><JK 8::LDLC8K@FEJ F=
C@K?@LD J8CKJ 8I< =FLE; @E -8C8I ;< /PLE@ I><EK@E8 8E; <J@<IKF ;<
K8:8D8 ?@C<  @>  .?< C@K?@LD :FEK<EKJ 8M<I8><J GGD @E K?<
:<EKI8C QFE< F= K?< K8:8D8 ;<GFJ@KJ 18II<E  I@:BJ<E <K 8C

::FI;@E> KF 18II<E  K?< D8@E @EUFNJ KF K?<J< J8C8IJ 8I<
;I8@E8>< N8K<I =IFD K?< MFC:8E@: =FID8K@FEJ F= K?< E;<8E "@>?C8E;J
<8JK F= K?< 98J@E 8E; K?8K K?< J8CKJ @E K?@J 9I@E< FI@>@E8K< 9FK? =IFD
N<8K?<I@E> F= MFC:8E@: IF:BJ D8@ECP % &@ '>  8E; C<8:?@E> F= 8E
:@<EK .<IK@8IP <M8GFI@K<J N@K? 8 DFK?<I J8CKC8P<I 9<E<8K? K?< MFC
:8E@: =FID8K@FEJ GIFM@;@E> (8 8 C -)X KF K?< DFJK J8C@E< @EUFN
N8K<IJ 18II<E 
"FN<M<I K?<I< @J <M<IP I<8JFE KF 9<C@<M< K?8K K?< .<IK@8IP <M8GFI
@K<J DFK?<I J8CK K?8K 8::LDLC8K<; @E K?@J 8I<8 N<I< ;<GFJ@K<; 9P K?<
J8D< GIF:<JJ<J 8J 8K K?< GI<J<EK @< 9P ?P;IFK?<ID8C GIF:<JJ<J ;I@M<E
9P K?< JL9;L:K@FE F= F:<8E@: :ILJK 8E; K?< 8JJF:@8K<; MFC:8E@JD .?@J @J
8CJF :FETID<; 9P 8 JKL;P F= -K<@ED<KQ  N?F @EM<JK@>8K<; 8 GC8P8
C8B< 8K <8JK<IE *LE8 °–°- N@K? I<JG<:K KF 9FIFE 8E; C@K?@LD
@E I<J@;L8C 9I@E<J =<<; N8K<IJ 8E; JFCLK@FEJ =IFD N<8K?<I<; IF:BJ .?<
I<JLCKJ F= ?@J 8E8CPQ<J 8I< K?8K I<J@;L8C 9I@E<J =IFD K?< GC8P8 C8B< :FE
K8@E LG KF D>C F= 9FIFE 8E;  D>C F= C@K?@LD .?< DFJK @D
GFIK8EK JLGGC@<I F= K?<J< <C<D<EKJ KF K?< C8B< &8J LII8J ,@M<I :FE
K8@EJ D>C 9FIFE 8E; D>C C@K?@LD "@J :FE:CLJ@FEJ 8I<'FJK F=
K?< C@K?@LD @EGLK KF K?< 98J@E @J C@B<CP ><E<I8K<; 9P GI<J<EK ><FK?<ID8C
JFLI:<J I8K?<I K?8E 9P N<8K?<I@E> 8E; C<8:?@E> F= @>E@D9I@K<J 8E; GCL
KFE@: IF:BJ-K<@ED<KQ 
.?< <EI@:?D<EK GIF:<JJ<J K?8K 8I< I<JGFEJ@9C< =FI K?< C8I>< <EI@:?
D<EKJ F= C@K?@LD 8E; 9FIFE @E K?<J< J8CK 8::LDLC8K@FEJ ?8J 9<<E 8
CFE>;@J:LJJ<; :FELE;ILD "FN<M<I <OG<I@D<EK8C NFIB 9P FJK8C <K
8C  J?<; JFD< C@>?K FE GFJJ@9C< D<:?8E@JDJ 9P J?FN@E> K?8K
9FK?  8E; &@ 9<?8M< 8J @E:FDG8K@9C< <C<D<EKJ @E 98J8CK@: D8>D8J
.?< K<ID @E:FDG8K@9C< <C<D<EKI<=<IJ KF <C<D<EKJ N@K? C8I>< @FE@: ;@
8D<K<I 8E;FI ?@>? :?8I><J K?8K TK GFFICP @EKF K?< :8K@FE J@K<J F= K?<
D@E<I8CJ N?<I< K?<P DFJK :FDDFECP F::LI .?@J @J :8LJ@E> K?<D KF
UNCORRECTED PROOF
M. Hovland et al. Marine and Petroleum Geology xxx (2018) xxx-xxx
Fig. 7. -8C8I ;< *8JKFJ !I8E;<J *LE8 8I<8 ?@C< J?FN@E> @E;LJKI@8C GIF;L:K@FE F= J8CKJ FE K?< J8C8I *IF;L:<; N@K? !FF>C<8IK?
DFI< <8J@CP G8IK@K@FE @EKF K?< DFCK<E G?8J< F= 8 IF:B FI @EKF 8 N8
K<IG?8J< @= K?8K @J 8M8@C89C< FI K?@J I<8JFE 9FK?  8E; &@ 8I< DFI<
<8J@CP C<8M@E> K?< JL9;L:K@FE JC89 <@K?<I N@K?@E K?< N8K<IG?8J< 8E;
FI K?< DFCK<E IF:B F= K?< ?8E>@E> N8CC 89FM< K?< F:<8E@: JC89 FJK8C
<K 8C  :FE:CL;< K?8K FK?  8E; &@ 8I< GIF989CP JKI@GG<; FV
=IFD 8 C@K?FJG?<I@: JC89 ;LI@E> JL9;L:K@FEI<C8K<; D<K8DFIG?@JD 8E;
8I< K?LJ EFK @EMFCM<; @E ;<<G D8EKC< I<:P:C@E>
.?@J :FE:CLJ@FE @J 98J<; FE <OG<I@D<EK8C NFIB K?8K J?FN<; K?8K
C@K?@LD N8J JKI@GG<; FV =IFD K?< 98J8CK 9P D8>D8K@: UL@;J 8K K<DG<I8
KLI<J 89FM< X° FJK8C <K 8C  FEJ<HL<EKCP  8E; &@ =IFD K?<
JL9;L:K@E> JC89 N@CC K<E; KF D@>I8K< LGN8I;J N@K? K?< N8K<I 8E; >8J<J
=IFD K?< JL9;L:K@FE QFE< 8E; K?@J ?FK N8K<I N@CC 8CJF @EK<I8:K N@K? K?<
IF:BJ 8CFE> K?< D@>I8K@FE IFLK< 8E; C<8:? FLK DFI<  8E; &@ @E :FE;L@KJ
F= K?< 8J:<EK KF K?< JLI=8:<
LIK?<IDFI< K?< MFC:8E@: <ILGK@FEJ F= 8E;<J@K@: C8M8 ;<J:I@9<;
89FM< :I<8K< 89LE;8EK MFC:8E@: 8J? N?@:? ?8J 8 M<IP ?@>? JG<:@T: JLI
=8:< 8I<8 =FI <OK<EJ@M< @EK<I8:K@FE N@K? K?< ?P;IFK?<ID8C >IFLE; N8
K<I .?@J >IFLE; N8K<I J<<DJ KF 9< 8IK<J@8E GLCJ8K@E> @E K?< 8I<8J F=
J8CK ;<GFJ@K@FE <8I@E> @E D@E; 8CJF K?8K K?< ?FK ?P;IFK?<ID8C8IK<J@8E
>IFLE;N8K<I <> X° ?8J 8 C8I>< :8G8:@KP KF JKI@G FV 9FK?  8E;
&@ =IFD K?< MFC:8E@: 8J? 8E; C8M8J @K I<GI<J<EKJ 8E <=T:@<EK :FEM<PFI
=FI K?<J< KNF JG<:@<J KF K?< J8CK C8B<J FJK8C <K 8C 
,?PFC@K?@: D8>D8 @J BEFNE KF :FEK8@E DFI<  8E; &@ K?8E 8E;<J@K@:
98J8CK 8J<; FE K?@J =8:K ,<KK@> <K 8C  JL>><JK<; K?8K I<C8K@M<CP
?@>?<I :FE:<EKI8K@FEJ F= &@ 8E;  @E 9I@E<J =IFD K?< JFLK? <E; F= -8C8I
;< /PLE@ E<8I K?< DFLK? F= K?< ,@F !I8E;< ;< &@G<Q N<I< JFLI:<;
=IFD I<:<EK I?PFC@K?@: MFC:8E@: IF:BJ -?8N <K 8C  8E; -?8N 8E;
-KLI:?@F  ?8M< 8CJF ;<DFEJKI8K<; K?8K 9FK?  8E; &@ 8I< C@B<CP KF
9< ;<GC<K<; =IFD I?PFC@K?@: IF:BJ 9P ?FK N8K<I UFN @E K?< ;<<G<I :ILJK
8E; KF 9< <EI@:?<; @E K?< LGG<I :ILJK
.?LJ K?< D8@E JFLI:<J F= K?< 9FIFE 8E; C@K?@LD J8CKJ @E K?< E;<J
'FLEK8@EJ 8I< JL>><JK<; KF 9< 9I@E<J =IFD K?< F:<8E@: JL9;L:K@FE JC89
.?<J< ?FK 9I@E<J 8I< C<8:?@E> 9FIFE 8E; C@K?@LD =IFD D8EKC< IF:BJ 8E;
MFC:8E@: IF:BJ @E K?< FM<I9LI;<E .?< :?CFI@;<J JLC=8K<J 8E; :8I9FE8
:<FLJ J8CKJ @E K?< ?FK JGI@E>J K?8K =<<; K?< J8CK C8B<J 8I< JL>><JK<; KF
?8M< K?< J8D< FI@>@E .?< ?P;IFK?<ID8C GIF:<JJ<J ?8M< 9<<E FE>F@E>
=IFD K?< FEJ<K F= K?< F:<8E@: JL9;L:K@FE @< ;LI@E> K?< <EK@I< 9L@C;LG
F= K?< E;<8E 'FLEK8@EJ JK8IK@E> @E K?< $LI8JJ@: CFEJF  CFEJF
8E; ,@J8:?<I  <EJFE <K 8C 
.?LJ @K :8E 9< :FE:CL;<; K?8K ;<<GJ<8K<; ?P;IFK?<ID8C GIF:<JJ<J
8JJF:@8K<; N@K? 8:K@M< FI;@CC<I8E 8I: MFC:8E@JD 8E; 8JJF:@8K<; ?P
;IFK?<ID8C 8:K@M@KP ?8M< GIF;L:<; DFJK F= K?< M@J@9C< J8CK 8::LDLC8
K@FEJ @E K?< E;<8E 'FLEK8@EJ @E:CL;@E> K?< C@K?@LD 8E; 9FIFE J8CKJ
2.1.4. Hidden salts of the Andes and other subduction zones
.?< E;<8E 'FLEK8@EJ I<GI<J<EK K?< CFE><JK :FEK@E<EK8C DFLEK8@E
I8E>< @E K?< NFIC; BD CFE> 8E; 8I<  BD N@;< @E K?<
:<EKI8C G8IK .?< FIF><EP @E@K@8K<; @E K?< $LI8JJ@: G<I@F; 9LK :ILJK8C
K?@:B<E@E> F= K?< FM<II@;@E> GC8K< JK8IK<; @E K?< /GG<I I<K8:<FLJ
N@K? D8IB<; GLCJ<J @E F:<E< 8E; (<F><E< N@K? I<8II8E><D<EKJ F=
K?< FIF><EP .?< :FEM<I><E:< M<CF:@KP @J M<IP LE:<IK8@E 9LK M8CL<J F=
DDPIXW 8I< <JK@D8K<; :I<8K@E> 8 KI<E:?G<IG<E;@:LC8I J?FIK<E@E>
F= BD '8IK@EF; <K 8C  .?< FEJ<K F= U8K JL9;L:K@FEJ
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J<8N8K<I ?8M< 9IFL>?K @DD<EJ< MFCLD<J F= 9I@E<J 8E; J8CK ;FNE @EKF
K?< JL9;L:K@FE QFE< .?< @E@K@8K@FE F= ?P;IFK?<ID8C UFN 8E; MFC:8E
@JD 89FM< K?< JL9;L:K@FE JC89 ?8M< KI8EJGFIK<; J@>E@=@:8EK MFCLD<J F=
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JD8CC =I8:K@FE F= K?< KFK8C J8CK MFCLD< ?@;@E> @E K?< JL9;L:K@FE QFE< (FK
8CC F= K?< DF9@C@Q<; J8CK ?8J I<8:?<; KF K?< JLI=8:< 8E; @K @J K?<I<=FI<
C@B<CP K?8K M<IP C8I>< MFCLD<J F= J8CKJ 8E; 9I@E<J 8I< JK@CC ?@;@E> @E K?<
IF:B MFCLD<J 89FM< K?< JL9;L:K@FE QFE< N?@:? ?8M< LG KF  GFIFJ@KP
&8LDFE@<I <K 8C 
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FCF>@:8C 8E; ?P;IF><FCF>@:8C GIF:<JJ<J 8E; N?<E K?<P 8I< GI<J<IM<; 9P
8 GI<M8@C@E> ;IP :C@D8K< )ECP ><FG?PJ@:8C D<8JLI<D<EKJ C@B< K?< :FE
;L:K@M@KP D<8JLI<D<EKJ F= &8LDFE@<I <K 8C  :8E GIFM@;< ?@EKJ
89FLK JL:? ?@;;<E ;<GFJ@KJ F= J8CKJ 8E; 9I@E<
2.2. Other types of subduction
LI@E> JL9;L:K@FE GIF:<JJ<J K?< ;<EJ@KP F= K?< JC89 ;<K<ID@E<J
N?<K?<I @K N@CC JL9;L:K FI EFK #DGFIK8EK @JJL<J @E K?@J GIF:<JJ 8I< K?<
;<EJ@KP F= K?< F:<8E@: :ILJK N@K? @KJ CF8; F= J<;@D<EKJ K?< ;<EJ@KP
F= 8EP D@:IF:FEK@E<EKJ 8E; K?< ;<EJ@KP 8E; :FDG<K<E:< F= K?< :FCC@;
@E> :FEK@E<EK <> !LKJ:?<I <K 8C  LI@E> :FCC@J@FE8C JL9;L:
K@FE C@B< @E K?< CGJ FI "@D8C8P8J J<;@D<EKJ 8E; C<JJ ;<EJ< IF:BJ 8I<
:FDDFECP GLJ?<; FE KFG ;LI@E> K?< FIF><E<J@J =FID@E> 8::I<K@FE8IP
UNCORRECTED PROOF
M. Hovland et al. Marine and Petroleum Geology xxx (2018) xxx-xxx
N<;><J :?8I8:K<I@JK@: E8GG<J 8E; DFLEK8@EJ 89FM< K?< JL9;L:K@E> JC89
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KF K?< @E:FD@E> JC89 .?< K?@:BE<JJ 8E; :FDGFJ@K@FE F= K?@J IF:B G8:B
8>< FE KFG F= K?< JL9;L:K@E> JC89 ?8J :FEJ<HL<E:<J =FI K?< C8K<I 9<?8M
@FI F= 9I@E<J 8E; J8CKJ =FID<; ;LI@E> JL9;L:K@FE -8CKJ K?8K 8I< =FID@E>
@EJ@;< 8E; 8IFLE; K?< JL9;L:K@E> JC89 D8P 9< ;<<GCP 9LI@<; 8E; 8EP
J8CK N@CC K?<I<=FI< ?8M< KF D@>I8K< K?IFL>? C8I>< 9F;@<J F= IF:BJ KF <D
8E8K< FEKF K?< JLI=8:< #E K?< "@D8C8P8J 8E; K?< CGJ J8CKJ 8I< <E:FLE
K<I<; K?8K N<I< G8IK F= K?< J<;@D<EKJ N@K?@E K?< GI<<O@JK@E> 98J@EJ GI@FI
KF K?< :FCC@J@FE .?@J J8CK J?FNJ 8CC K?< :FDDFE J@>EJ F= ;<=FID8K@FE 8J
8 I<JLCK F= K?< FIF><E<J@J
"FN<M<I ;<<G ;FNE @E <M<IP B@E; F= JL9;L:K@FE QFE< N@K? F:<8E@:
:ILJK K?<IDF;PE8D@:J K<CCJ LJ K?8K K?<I< 8I< C@B<CP ?@;;<E J8CKJ =FID<;
@EJ@;< 8E; 8IFLE; K?< JL9;L:K@E> JC89 LI@E> C8K<I I@=K@E> FC; JLKLI<
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:ILJK8C JKI<JJ JL:? J8CKJ D8P 9< I<DF9@C@Q<; 8E; 9<:FD< M@J@9C< 8E;
D8P 8CJF D@O N@K? E<NCP =FID<; J8CK 1@K?@E JL:? 8E 8I<8 K?< :?IFEFC
F>P F= J8CK =FID8K@FE @J K?<I<=FI< M@IKL8CCP @DGFJJ@9C< KF ;<K<ID@E<
N@K?FLK BEFN@E> K?< K<:KFE@: ?@JKFIP F= K?8K 8I<8
.?@J @J @CCLJKI8K<; 9P K?< "@D8C8P8E FIF><E<J@J @E @>  .?< DFLE
K8@E 9L@C;@E> N8J ;FD@E8K<; 9P K?ILJK@E> F= E8GG<J :FDGFJ<; F= D8I@E<
J<;@D<EK8IP IF:BJ =IFD K?< .<K?PJ ):<8E LG @EKF K?< DFLEK8@E :?8@E
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LJKI8C@8E :FCC@;@E> K<:KFE@: GC8K<J N<I< :FDGFJ<; F= CFN ;<EJ@KP :FE
K@E<EK8C IF:BJ .?< J<;@D<EK8IP IF:BJ @E K?< E8GG<J 8CJF @E:CL;<; J8CKJ
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N@K? K?< FK?<I J<;@D<EK8IP IF:BJ
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8IFLE; K?< FC; JL9;L:K<; JC89 8I< :LII<EKCP 9<@E> KI8EJGFIK<; KF K?<
JLI=8:< ;L< KF K?< FG<E =8LCKJ @E K?< GLCC8G8IK 98J@E FE KFG F= K?< JC89
N@K?@E K?< <8; -<8 8I<8 -<< 8CJF *8IK  F= K?@J GL9C@:8K@FE "FMC8E; <K
8C 
3. Oceanic-oceanic subduction and salts
3.1. Some characteristics of the Mediterranean Ridge subduction zone
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8IFLE; K?< JL9;L:K@E> JC89 CK?FL>? FE< D@>?K K?@EB K?8K J8CKJ FE K?<
J<89<; 8I< DFI< <OGFJ<; KF ;@JJFCLK@FE K?8E J8CKJ FE K?< JLI=8:< K?@J
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I<=<I<E:< KF K?< conceptual element F= J8CK I<TE@E>
3.2. Submarine brine lakes at the Mediterranean Ridge
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N?@:? ;@JK@E>L@J?<J @K =IFD FK?<I 8::I<K@FE8IP :FDGC<O<J @J K?< GI<J
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J<;@D<EKJ 8K 8 ;<GK? F= 8 =<N ?LE;I<; D<K<IJ 9<E<8K? K?< J<8 9<;
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
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@J 8JJF:@8K<; N@K? K?< D8I@E< JL9;L:K@FE K?8K =FIDJ K?< '<;@K<II8E<8E
,@;>< :FDGC<O 8J ;@J:LJJ<; 9P "FMC8E; <K 8C  J<< K?<@I @>J
8E;  .?< ?P;IFK?<ID8C E8KLI< F= K?<J< 9I@E<J @J JLGGFIK<; 9P K?<
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:FEJ@JK@E> F= =8LCKJ 8E; =I8:KLI<J K?8K G<E<KI8K< ;<<G @EKF K?< :ILJK 8E;
 :FEK@EL<J LG K?IFL>? C8P<IJ F= <M8GFI@K<J .?@J @J 8CJF @E;@:8K<; 9P
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3.2.1. Discovery basin
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K<I GIFTC<J ;<DFEJKI8K< K?8K K?@J 9I@E< ;@JJFCM<J J<;@D<EK8IP :8C:@K< KF
Fig. 8. #CCLJKI8K@FE F= K?< :FCC@J@FE QFE< 9<KN<<E #E;@8 8E; .@9<K Left #CCLJKI8K@FE F= K?< ;I@=K@E> G8K? F= #E;@8 .?< =8JK EFIK?N8I;J DFM@E> #E;@8E 8E; LJKI8C@8E K<:KFE@: GC8K<J :CFJ<;
K?< .<K?PJ ):<8E 89FLK  D@CC@FE P<8IJ 8>F FK? GC8K<J N<I< :FDGFJ<; F= CFN ;<EJ@KP :FEK@E<EK8C :ILJK I<JLCK@E> @E 8 DFLEK8@E 9L@C;@E> ;FD@E8K<; 9P K?ILJK@E> F= E8GG<J :FEJ@JK@E>
F= D8I@E< J<;@D<EK8IP IF:BJ @E:CL;@E> J8CK =IFD K?< 8E:@<EK F:<8E Right .?< :FCC@J@FE F= #E;@8 8E; .@9<K 8E; K?< FIF><E<J@J F= "@D8C8P8 .?< JLKLI< QFE< N?<I< E<N I@=K@E> D@>?K K8B<
GC8:< @J @E;@:8K<; 'F;@T<; =IFD @CCLJKI8K@FE 9P -FEA8 &<PM8 *8J8;<E8 @KP FCC<>< J<< ?KKG><FG?@C<E<K&<JJFEJ*C8K<.<:KFE@:J*C8K<.<:KFE@:J7?KDC
UNCORRECTED PROOF
M. Hovland et al. Marine and Petroleum Geology xxx (2018) xxx-xxx
Fig. 9. Left  J@;< J:8E JFE8I @D8>< F= K?< J<8UFFI FM<I K?< &K8C8EK< I@E< GFFC 98J@E 8;A8:<EK KF K?< '<;@K<II8E<8E ,@;>< 1FF;J@;< <K 8C  * I@E< GFE; Right :?FJFLE;<I
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=IFD 18CCD8EE <K 8C  .?< TIJK JKI@B@E> F9J<IM8K@FE @J K?8K (8
@E  @J I<;L:<; KF FECP  G<I :<EK KF K?8K F= J<8N8K<I N?@C< C @J @E
:I<8J<; E<8ICP  K@D<J FK? % 8E; '> @E  8I< 8IFLE;  K@D<J ?@>?<I
K?8E @E K?< J<8N8K<I E <OGC8E8K@FE KF K?@J :8E 9< C@EB<; KF K?< M8I@FLJ
JFCL9@C@K@<J F= K?< J<8 J8CKJ 8K ?@>?<I K<DG<I8KLI< @< K?< JFCL9@C@KP F=
GFK8JJ@LD 8E; D8>E<J@LD :?CFI@;<J @J D8EP K@D<J ?@>?<I K?8E K?8K F=
JF;@LD :?CFI@;< 8K ?@>?<I K<DG<I8KLI<J P 8JJLD@E> K?8K EFID8C J<8
N8K<I N8J @E@K@8CCP =<<;@E> K?< ?P;IFK?<ID8C JPJK<D K?<J< ;8K8 @E;@
:8K< K?8K JF;@LD :?CFI@;< ?8C@K< @J GI<:@G@K8K<; N@K?@E K?< ?P;IFK?<I
D8C JPJK<D N?@C< K?< DFI< JFCL9C< :?CFI@;<J 8E; JLC=8K<J 8I< M<EK@E>
LG @EKF K?<  9I@E< GFE;
.?@J @J 8E 8CK<IE8K@M< <OGC8E8K@FE KF K?8K F= 18CCD8EE <K 8C 
N?F JL>><JK<; ?P;IFK?<ID8C C<8:?@E> F= '<JJ@E@8E 9@J:?F=@K< 8J K?<
JFLI:< =FI K?< D8>E<J@LD :?CFI@;< GIFM@;<; K?8K 9@J:?F=@K< @J GI<J<EK @E
K?< ?P;IFK?<ID8C JPJK<D LK K?<E N< ?8M< K?< E<OK HL<JK@FE ?FN N8J
K?< '<JJ@E@8E 9@J:?F=@K< =FID<; @E K?< TIJK GC8:< 18J K?8K 8CJF =FID<;
9P ?P;IFK?<ID8C GIF:<JJ<J
EFK?<I JKI@B@E> F9J<IM8K@FE @J K?< CFN G" F= K?<  9I@E<  G" F=
 @J =8I 9<CFN K?< JK89@C@KP C@D@K F= :8I9FE8K<J 8K G"  8K 8D9@<EK
:FE;@K@FEJ 8E; <OGC8@EJ N?P :8I9FE8K<J 8I< ;@JJFCM<; @E K?< J<;@D<EKJ
18CCD8EE <K 8C  .?< ;@JJFCLK@FE F= :8I9FE8K<J @J 9LV<I@E> K?<
GFI< N8K<I KF ?@>?<I G" N?<I< E<N :8I9FE8K<J :8E :IPJK8CC@Q< &<8:?
@E> F= 9@J:?F=@K< ;F<J EFK <OGC8@E K?< CFN G" F= K?< 9I@E<
-<;@D<EKJ @E K?< 98J@E 8I< ;8IB:FCFI<; ?<D@G<C8>@: DL;J N@K?
9@F><E@: FG8C@E< FFQ< 8E; 89LE;8EK FI>8E@: :8I9FE 18CCD8EE <K 8C
Table 2
FDGFJ@K@FE F= @J:FM<IP 8J@E 9I@E< :FDG8I<; KF EFID8C J<8N8K<I DFCB> N8K<I .?<
G" M8CL< F= K?< 9I@E< @J M<IP CFN :FDG8I<; KF J<8N8K<I
-G<:@<J 9I@E< J<8N8K<I
(8  
%  
8  
'>  
C  
-)X  
G"  
 -L:? FI>8E@: DL;J 8I< GI<J<IM<; @E K?< ?PG<IJ8C@E< 8E; 8EFO@:
9I@E< GFE; N?@:? 8CJF TKJ N@K? 8 ?P;IFK?<ID8C FI@>@E F= K?< 9I@E<
4. Early stage continental rifting and salts
.?<I< @J FECP FE< KIL< :FEK@E<EK8C I@=K@E> :LII<EKCP 8:K@M< FE 8IK?
K?< 8JK =I@:8E ,@=K , CK?FL>? K?<I< 8I< KI8EJ=FID =8LCKI<C8K<;
J8CK 98J@EJ JL:? 8J K?< <8; -<8 I@=K QFE< 9I@<UP ;@J:LJJ<; @E *8IK 
"FMC8E; <K 8C  FECP K?< , @J @E:CL;<; ?<I<@E
4.1. The East African rift (EAR) and salt
, ILEJ =FI FM<I BD @E 8 DFI<FIC<JJ (- ;@I<:K@FE =IFD
K?< =8I KI@GC< ALE:K@FE 8 ?FK JGFKD8EKC< GCLD< KF K?< 'FQ8D9@HL<
?8EE<C '@;N8P 8CFE> K?< <8JK<IE 9I8E:? F= , @J K?< (FIK? .8E
Q8E@8E @M<I><E:< 4FE< (. N?@:? C@EBJ K?< I@=K N@K? K?< %@C@D8E
A8IF MFC:8E@: 8I<8 =LIK?<I KF K?< <8JK 1?<I< K?< <8JK<IE 9I8E:? F= ,
D8B<J K?@J C@EB K?<I< 8I< ;@JK@E:K 8E; LE@HL< MFC:8E@: 8E; UL@;I<
C8K<; =<8KLI<J @E:CL;@E> K?< 8CB8C@E< C8B<J (8KIFE 8E; '8>8;@ K?< C8I><
(>FIF>FIF I8K<I 8E; K?< :8I9FE8K@K< MFC:8EF )C FE@PF &<E>8@ 8B<I
<K 8C 
.?< ?@>? K<DG<I8KLI< ><FK?<ID8C JPJK<DJ 8CFE> K?< 8JK<IE 9I8E:?
F= K?< , 8I< :CFJ<CP I<C8K<; KF K?< MFC:8E@: :<EK<IJ N?@C< K?< 1<JK<IE
9I8E:? F= K?< I@=K @J :?8I8:K<I@Q<; 9P J<;@D<EK 8E; C8B< TCC<; >I89<EJ
8E; I<JKI@:K<; MFC:8E@JD -8<DLE;JJFE 
'8E8 <K 8C  ?8M< DF;<CC<; K?< JFLI:< F= K?< (. MFC:8E@:
IF:BJ 8E; @;<EK@T<; @K KF 9< D<K8JFD8K@Q<; JL9:FEK@E<EK8C C@K?FJG?<I@:
D8EKC< FEK@E<EK8C C@K?FJG?<I< LE;<I>F<J JL9JK8EK@8C DF;@T:8K@FE
9FK? ;LI@E> K?< I@=K@E> GIF:<JJ 8E; 8J 8 I<JGFEJ< KF K?< @DG8:K F= 8 I@J
@E> K?<ID8C 8EFD8CP JL:? 8J 8 D8EKC< GCLD< .?< GI<J<E:< F= 8 D8E
KC< GCLD< :8E JKIFE>CP @EUL<E:< K?< :?<D@:8C :FDGFJ@K@FE F= K?< C8M8J
<ILGK<;'8E8 <K 8C 
.?< (>FIF>FIF I8K<I @J 89FLK BD @E ;@8D<K<I  D ;<<G  @>J
 8E;  8E; ?8J ELD<IFLJ 9I@E< JGI@E>J N?@:? :FEKI@9LK< KF D8B@E>
K?< 8I<8 <OKI<D<CP =<IK@C< 8E; K?LJ 8 ?L9 =FI GC8EKJ 8E; 8E@D8CJ
4.2. Alkaline lakes and salts
::FI;@E> KF 18II<E  K?< 8CB8C@E< &8B< '8>8;@ &8B< (8
KIFE 8E; FK?<I C8B<J @E K?< , JPJK<D 8I< :?8I8:K<I@Q<; 9P J<8JFE8C
=I<J?<E@E> ?@>? GIF;L:K@M@KP C<M<CJ 8E; 9I@>?K I<; N8K<IJ  @>  .?<
:FCFI :FD<J =IFD ?8CF8CB8C@G?@C@: 8I:?8<8 EFK :P8EF98:K<I@8 .?< 8I
:?8<8C JG<:@<J 9<CFE> KF K?< ><E<I8 Natronacoccus, Natronobacterium,
Natrialba, Halorubrum, Natronorubrum 8E; Natronomonas N?@:? 8CC F:
:LI @E K?< 9I@E<J F= &8B< '8>8;@ 8E; &8B< (8KIFE .?@J 9@FK8 UFLI@J?<J
@E K?< C8B< :<EK<I 9I@E<J N?<I< KIFE8?8C@K< J8KLI8K@FE GI<M8@CJ N@K?
G" LG KF  .?@J ?@>? 8CB8C@E@KP D8P @E;@:8K< K?8K K?< ?P;IFK?<ID8C
UNCORRECTED PROOF
M. Hovland et al. Marine and Petroleum Geology xxx (2018) xxx-xxx
Fig. 10. -?8;<; I<C@<= D8G F= K?< :<EKI8C I<>@FE F= K?< <8JK<IE 9I8E:? F= K?< 8JK =I@:8E
,@=K , N@K? K?< (>FIF>FIF I8K<I (: K?< )C F@EPF &<E>8@ :8I9FE8K@K< MFC:8EF
)& 8E; &8B< (8KIFE &( '8G GIF;L:<; LJ@E> K?< '8I@E< !<FJ:@<E:< 8K8 -PJK<D
!<FD8G8GGFI>
GIF:<JJ<J I<JGFEJ@9C< D8P 9< I<C8K@M<CP CFNK<DG<I8KLI< <> J<IG<E
K@E@Q8K@FEI<C8K<;
,<>@FE8CCP J8C@E@K@<J @E K?< <8JK =I@:8E I@=K M8CC<P C8B<J I8E>< =IFD
8IFLE; KFK8C J8CKJ NM @E K?< DFI< EFIK?<ICP C8B<J F>F
I@8 (8BLIL CD<EK<@K8 8E; -FE8:?@ KF KIFE8 8E; ?8C@K< J8KLI8K@FE
 @E C8B<J KF K?< JFLK? '8>8;@ 8E; (8KIFE  :FD9@E8K@FE F=
?@>? 8D9@<EK K<DG<I8KLI< ?@>? C@>?K @EK<EJ@KP 8E; 8 :FEK@ELFLJ I<JLG
GCP F= )X D8B<J K?<J< JF;8 C8B<J 8DFE>JK K?< ?@>?<JK @E K?< NFIC;
@E K<IDJ F= J<8JFE8C GC8EBKFE@: 9@FD8JJ !I8EK <K 8C  8E; 8CJF
GC8:<J K?<D 8DFE> K?< NFIC;J DFJK GIF;L:K@M< <:FJPJK<DJ '<C8:B 8E;
%@C?8D 18II<E 
L< KF K?<@I F9M@FLJ 8JJF:@8K@FE N@K? <OK<EJ@FE8C I@=K@E> ?@>?KF
M<IP?@>? ?<8KUFN ELD<IFLJ =LD8IFC<J ?FK JGI@E>J 8E; 8:K@M< MFC
:8E@: =<8KLI<J K?<I< :8E 9< EF ;FL9K K?8K K?< J8CKJ GIF;L:<; @E K?@J
EFED8I@E< <EM@IFED<EK @J ><FK?<ID8CCP 8E; ?P;IFK?<ID8CCP GIF;L:<;
8E; D8P <M<E 9< I<C8K<; KF J<IG<EK@E@Q8K@FE 8K ;<GK? <> -:I@98EF <K
8C 
1?<I<8J DFJK C8M8J @E K?< NFIC; 8I< I@:? @E J@C@:8K< D@E<I8CJ )C
F@EPF &<E>8@ @J 8 JF;8 MFC:8EF@JJL@E> :8I9FE8K@K< DFI<FIC<JJ ;<
MF@; F= J@C@:8K<J .?< :8I9FE8K@K< MFC:8EF<J 8CJF JL>><JK K?8K D8EKC<
GCLD<J DLJK 9< 8:K@M<CP =FID@E> 9<CFN :FEK@E<EK8C :ILJK .?< @JFKFG<
J@>E8KLI<J =FLE; @E D8EP :8I9FE8K@K<J ?8M< 9<<E 8KKI@9LK<; KF @EMFCM<
D<EK F= I<:P:C<; G<I?8GJ 8><; C@D<JKFE< FI FK?<I :8I9FE8K<I@:? D8K<
I@8C ;LI@E> GCLD< 8:K@M@KP FI ><E<I8K@FE F= D8>D8J =IFD ;<<G D8EKC<
D8K<I@8C <EI@:?<; @E )X <EKI8@E<; N@K?@E 8 GCLD<<CC 8E; .@CKFE

.?< )C F@EPF &<E>8@ C8M8 @J I@:? @E K?< I8I< JF;@LD 8E; GFK8JJ@LD
:8I9FE8K< D@E<I8CJ EP<I<I@K< 8E; >I<>FIP@K< L< KF K?@J LELJL8C :FD
GFJ@K@FE K?< C8M8 <ILGKJ 8K I<C8K@M<CP CFN K<DG<I8KLI<J F= 8GGIFO@D8K<CP
° 8 K<DG<I8KLI< JF CFN K?8K K?< DFCK<E C8M8 8GG<8IJ 9C8:B @E JLE
C@>?K I8K?<I K?8E ?8M@E> K?< I<; >CFN :FDDFE KF DFJK C8M8J #K @J 8CJF
:?8I8:K<I@Q<; 9P ?8M@E> DL:? CFN<I M@J:FJ@KP K?8E J@C@:8K< C8M8J F=K<E
C<JJ M@J:FLJ K?8E N8K<I .?< JF;@LD 8E; GFK8JJ@LD :8I9FE8K< D@E<I8CJ
F= K?< C8M8J <ILGK<; 8K )C F@EPF &<E>8@ 8I< LEJK89C< 8K K?< 8IK?J JLI
=8:< 8E; JLJ:<GK@9C< KF I8G@; N<8K?<I@E> HL@:BCP KLIE@E> =IFD 9C8:B KF
>I<P @E :FCFI .?< I<JLCK@E> MFC:8E@: C8E;J:8G< @J K?<I<=FI< ;@==<I<EK
=IFD 8EP C8E;J:8G< =FID<; 9P J@C@:8K< C8M8J
::FI;@E> KF LIB< <K 8C  K?< F::LII<E:< F= :8I9FE8K@K<J @J
N@KE<JJ F= M<IP FC; JLKLI<J K?8K D8P ?8M< <OG<I@<E:<; J<M<I8C 1@CJFE
:P:C<J N@K? 8::LDLC8K@FE F= C8I>< MFCLD<J F= ;<<GJ<8K<; <OFK@:D@E
<I8CJ =FID<; 9P GIF:<JJ<J N@K?@E K?< JL9;L:K@FE QFE< 8CJF @E FLI M@<N
@EMFCM@E> ?L>< 8DFLEKJ F= D8I@E< J8CKJ
, @J 8 :FEK@E<EK8C I@=K N@K?FLK :FEK8:K N@K? K?< F:<8E .IFE8 8E;
:8I9FE8:<FLJ J8CKJ 8I< ;FD@E8K@E> @E K?< JFLK?<IE G8IK F= K?< ,
N?@C< :?CFI@;<J ;FD@E8K< @E K?< EFIK?<IE G8IK .?@J :8E 9< <OGC8@E<;
9P M8I@FLJ JFLI:<J F= ?@;;<E J8CKJ@E K?< ?P;IFK?<ID8C JPJK<DJ F= K?<
I@=K .?< :8I9FE8K@K<J 8JJF:@8K<; N@K? )C F@EPF &<E>8@ 8I< 8CJF 8 G8IK
F= K?< JFLK?<IE JPJK<D F= K?< I@=K
4.3. Salt deposits in Danakil, Afar
8ICP <OGCFI8K@FE @E K?< =8I 8I<8 9P "LK:?@EJFE 8E; E><CJ 
I<JLCK<; @E K?< ;@J:FM<IP F= K?@:B J<HL<E:<J F= *C<@JKF:<E<'@F:<E<
J8CKJ .?<P ;<J:I@9< JFD< F= K?<@I TE;@E>J 9P “… K?< 8E8B@C <GI<J
J@FE 8E; K?< JLIIFLE;@E> I<>@FE F= K?< =8I :FEK8@E K?@:B J<HL<E:<J F=
*C<@JKF:<E<'@F:<E< J8CK N@K? 8K C<8JK  D F= <M8GFI@K< ?8M@E> 8::L
DLC8K<; 9<E<8K? K?< J8CK G8E F= (FIK?<IE 8E8B@C .?@J J<HL<E:< 8CJF
@E:CL;<J C8K<I8CCP :FEK@ELFLJ ?FI@QFEJ F= :8IE8CC@K< I8E>@E> =IFD  D
KF D @E K?@:BE<JJ @E 8JJF:@8K@FE N@K? K?< ?P;IFLJ J8CK 9@J:?F=@K<
D @E K?@:BE<JJ F::LII@E> 8K ;<GK?J I8E>@E> =IFD  D KF  D
9<CFN K?< JLI=8:< 8J :FETID<; 9P 9FI<?FC< ;8K8"LK:?@EJFE 8E;
E><CJ 
<:8LJ< F= K?< <OKI<D< 8I@;@KP F= K?@J I<>@FE JFD< GI@JK@E< 8EFD
8CFLJ J8CK=FID8K@FEJ 8E; 8CJF K?< :CFJ< I<C8K@FEJ?@G 9<KN<<E J8CK J<
HL<E:<J 8E; K?< "FCF:<E< 8><; !8;8 C< MFC:8EF N<I< EFK<; 9P K?<
<8ICP <OGCFI8K@FE@JKJ 1<JK F= !8;8 C< MFC:8EF 8 J8CK ;FD< D8@ECP
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J8CK U8KJ ×BD CF:8K<; EFIK? F= &8B< 8J<C<  BD EFIK? F= K?<
M<IP 8:K@M< IK8 C< MFC:8EF @E K?< EFIK?<IE =8I I<>@FE F= K?@FG@8
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<C<M8K@FE F= D 9<CFN J<8 C<M<C "< ;<J:I@9<J JFD< F= K?< JKIL:KLI<J
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J8CK GI<:@G@K8K<; =IFD ?FK JGI@E>J …” .8C9FK  @> 
*<I?8GJ K?< DFJK @EKI@>L@E> =<8KLI< ?< ;@J:LJJ<J @J K?< JF:8CC<;
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
UNCORRECTED PROOF
M. Hovland et al. Marine and Petroleum Geology xxx (2018) xxx-xxx
Fig. 11. Upper image !FF>C< 8IK? J8K<CC@K< M@<N F= K?< :<EKI8C I<>@FE F= K?< <8JK<IE 9I8E:? F= K?< 8JK =I@:8E ,@=K &(&8B< (8KIFE 8E; K?< JD8CC I<; I<:K8E>C< @E K?< C8B< @J K?<
CF:8K@FE F= K?< @D8>< 9<CFN Bottom image <K8@C<; M@<N F= 8 GFIK@FE F= &8B< (8KIFE E<8I @KJ N<JK<IE 9FI;<I .?@J <CC@GK@:8C N?@K< JKIL:KLI< N@K? :FE:<EKI@: C8P<IJ FE 8 98:B>IFLE;
F= I<; J8CKJ I<GI<J<EKJ 8 JL9JLI=8:< JGI@E> N?@:? @J K?< JFLI:< F= K?< GI<:@G@K8K<; J8CKJ #KJ :<EK<I I@J<J 89FLK  D 89FM< K?< JLIIFLE;@E> I<; J8CK #D8>< GIF;L:<; N@K? !FF>C< 8IK?
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DF;<C 8E; J8K@J=P J<M<I8C F= K?< Conceptual Elements >@M<E @E K?< #EKIF
;L:K@FE <> Thermo- and ?uid-dynamicsSolubility and precipitation of
saltsRe>ning of saltsSalt preservation 8E; Hidden salts
5. Continental rifting and salts
(LD<IFLJ I@=KI<C8K<; J8CK 98J@EJ 8I< BEFNE NFIC;N@;< 8E; JFD<
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
UNCORRECTED PROOF
M. Hovland et al. Marine and Petroleum Geology xxx (2018) xxx-xxx
Fig. 12. .?< Gada Ale J8CK @EK<IC8P<I<; C8M8 MFC:8EF Left D8G DF;@T<; =IFD 8I9<I@ 8E; 08I<K  Right !FF>C< 8IK? @D8>< F= !8;8 C< ,<; 8IIFNJ D8IB - J8CK ;FD< N@K?
@EK<I:8C8K<; C8M8 !!8;8 C< MFC:8EF .?< >I<<E JHL8I< @E K?< C<=K @D8>< J?FNJ K?< CF:8K@FE F= K?< I@>?K @D8><  FI @EK<IGI<K8K@FE F= K?< I<=<I<E:<J KF :FCFI @E K?@J T>LI< C<><E; K?<
I<8;<I @J I<=<II<; KF K?< 1<9 M<IJ@FE F= K?@J 8IK@:C<
Fig. 13. Left 8 :FE:<GKL8C ><FGIFTC< K?IFL>? &8B< 8J<C< EFK KF J:8C< 98J<; FE .8C9FK  8E; "FMC8E; <K 8C 8 J?FN@E> ?FN J8CK :8E 9< GIF;L:<; 8::FI;@E> KF K?< ?P
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CF:8C J8CK 8::LDLC8K@FEJ <> JL:? 8J J?FNE =FI K?< !8;8 C< MFC:8EF @> 
5.1. Geologic history of the red sea area
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5.2. The rifting of the red sea
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C@EB<; KNF M<IP 8:K@M< MFC:8E@: :<EK<IJ CF:8K<; 89FLK  BD 8G8IK
FE< @E EFIK?<IE >PGK GIF;L:@E> LG KF BDX F= MFC:8E@: D8K<I@8C
8E; FE< @E 3<D<E F= BDX @E K?< JFLK? J<< 8CJF @> 
.?@J @J 8CJF @E 8>I<<D<EK N@K? F:?I8E  N?F JK8K<J K?8K E
<G@JF;< F= ;@B< @EKILJ@FE ;8K<; 8K  '8 @J I<:FI;<; 8CFE> K?< <E
K@I< C<E>K? F= K?< ,<; -<8 8E; K?< I89@8E D8I>@E .?@J <G@JF;< N8J

UNCORRECTED PROOF
M. Hovland et al. Marine and Petroleum Geology xxx (2018) xxx-xxx
Fig. 14.  -B<K:? F= 8 ><FCF>@:8C GIFTC< DF;@T<; =IFD .8C9FK  ?@J @>  #K J?FNJ K?< JG<:K8:LC8I J8CK MFC:8EF<J 8K 8CCFC @E K?< 8E8B@C ;<GI<JJ@FE ."- :K@M< KFN<IJ F=
?P;IFK?<ID8C J8CK  "-8J@E UFFI<; 9P ?P;IFK?<ID8C J8CKJ " <8; ?P;IFK?<ID8C :FE<.8C9FKJ K<ID@EFCF>P  -8K<CC@K< @D8>< F= K?< 8CCFC 8I<8 8E; G8IKJ F= &8B< 8J<C<
J8CK G8EC8B< .?< P<CCFN C@E< 1 J?FNJ K?< CF:8K@FE F= GIFTC< @E  'F;@T<; =IFD .8C9FK   -L>><JK<; '<>8GFCP>FE8C :FEM<:K@FE :<CCJ.8C9FK  8JJF:@8K<; N@K?
LGN<CC@E> 8E; J<<G8>< =<8KLI<J FE &8B< 8J<C< 8E; 8K K?< 8CCFC J8CK DFLEK8@EJ DF;@T<; =IFD .8C9FK   FI @EK<IGI<K8K@FE F= K?< I<=<I<E:<J KF :FCFI @E K?@J T>LI< C<><E; K?< I<8;<I
@J I<=<II<; KF K?< 1<9 M<IJ@FE F= K?@J 8IK@:C<
DFI< @EK<EJ< @E K?< JFLK?<IE ,<; -<8 8E; N8J K?<I< 8::FDG8E@<; @E
GC8:<J 9P @EKILJ@FE F= GCLKFE@: 9F;@<J F= >I8E@K< KF >899IF@: :FDGFJ@
K@FE.?@J @J 8CJF N?<I< K?< TIJK F:<8E@Q8K@FE @E K?< ,<; -<8 JK8IK<;
5.3. Salt formation in the red sea
::FI;@E> KF FE8KK@ <K 8C  K?< J8CK @E K?< ,<; -<8 ?8GG<E<;
KF 8::LDLC8K< 8J =FCCFNJ M8GFI@K< ;<GFJ@K@FE KFFB GC8:< K?IFL>?
FLK K?< <EK@I< ,<; -<8 98J@E JK8IK@E> 8K 8IFLE;  '8 @E K?< '@;
;C<'@F:<E< -<II8M8CC@8E 8E; I<8:?@E> 8 K?@:BE<JJ F= K?FLJ8E;J F= D<
K<IJ '@K:?<CC <K 8C  FJNFIK?  "8C@K< 8E; 8E?P;I@K<>PG
JLD N<I< K?< D8@E D@E<I8C G?8J<J K?<P 8I< CF:8CCP @EK<I9<;;<; N@K?
J8E;JKFE<J 8E; J?8C<J 8J N<CC 8J N@K? :8I9FE8K< GC8K=FID ;<GFJ@KJ
@E;@:8K@E> @EK<IM8CJ F= EFID8C D8I@E< ;<GFJ@K@FE E; 8::FI;@E> KF
L>LJK@E <K 8C  .?< J<;@D<EK :FM<I :FEJ@JKJ F= '@F:<E< <M8GFI
@K<J 8E; PFLE><I G<C8>@: :8I9FE8K< FFQ< N@K? C8I>< K?@:BE<JJ<J F= LG KF
BD <> !@I;C<I 8E; 1?@KD8IJ?  -<8IC< 8E; ,FJJ  !@I;C<I
 FEK@E<EK8C 9I<8BLG 8E; J<8UFFI JGI<8;@E> :8LJ<; K?< ;@JILG
K@FE F= K?<J< <M8GFI@K<J N?@:? @E JFD< GC8:<J ?8M< 9<<E J?FNE KF UFN
KFN8I; K?< ;<<G<I 8O@8C I@=K @E K?< =FID F= J8CK >C8:@<IJ BEFNE 8J JL9
D8I@E< E8D8B@<IJ !@I;C<I  '@K:?<CC <K 8C 
#E 8 I<:<EK JKL;P 98J<; FE I<U<:K@FE J<@JD@: ;8K8 '@K:?<CC <K 8C
 ?8M< I<8:?<; K?< =FCCFN@E> :FE:CLJ@FEJ 98J<; FE :FEM<EK@FE8C
@EK<IGI<K8K@FE F= K?< -I<U<:KFIK?< @E=<II<; KFG F= <M8GFI@K<J I<U<:
KFI J K?< <M8GFI@K<J :8EEFK ?8M< 9<<E ;<GFJ@K<; 89FM< J<8 C<M<C
K?<P GIFM@;< 8 :FEJKI8@EK FE K?< JL9J@;<E:< @E K?< =FCCFN@E> ;@J:LJ
J@FEJ” “J@;< =IFD ;@8G@IJ K?< LGG<I C<M<CJ F= K?< - I<U<:K@FE :FEJ@J
K<EKCP C@< J?8CCFN<I K?8E  D9JC 5D<KI<J 9<CFN J<8 C<M<C6 #E K?<
EFIK?<IE ,<; -<8 - =FIDJ 8 D ;<<G ;<GI<JJ@FE 8C@>E<; N@K? K?<
I@=K” “1< JL>><JK K?8K K?< <M8GFI@K<J FI@>@E8CCP ?8; 8 U8K ?FI@QFEK8C
JLI=8:< 8K K?< <E; F= K?< '@F:<E< 8E; ?8M< JL9J<HL<EKCP 9<<E ;@JKFIK<;
9P @JFJK8K@: <==<:KJ 8E; 8O@8C I@=K@E> N?@:? @E KLIE GIFDFK<; <M8GFI@K<
UFN8>< )V8O@J <M8GFI@K< ;<GI<JJ@FEJ :FII<JGFE; N@K? UFNJ @;<EK@T<;
N@K? DLCK@9<8D JFE8I LIK?<IDFI< 8:IFJJI@=K CFNJ @E FL>L<I >I8M
@KP 8EFD8C@<J I<GI<J<EK M8CC<PJ @E K?< LE;<ICP@E> 98J<D<EK .?< FV8O@J
<M8GFI@K< ;<GI<JJ@FEJ FM<IC@< K?FJ< M8CC<PJ 8J NFLC; 9< <OG<:K<; @=
?8CFB@E<K@: DFM<D<EKJ N<I< >I<8K<JK N?<I< K?< <M8GFI@K<J 8I< CF:8CCP
K?@:B C<8;@E> KF ;<U8K@FE F= K?< <M8GFI@K< JLI=8:<'@K:?<CC <K 8C

.?< E8KLI< F= K?< :ILJK @E K?< :<EKI8C ,<; -<8 N8J ;@J:LJJ<; 9P
'@K:?<CC 8E; *8IB  N?F JL>><JK K?8K @K @J F= F:<8E@: :ILJK8C :FD
GFJ@K@FE .?@J @E=<I<E:< @J 98J<; G8IKCP FE K?< @EK<IGI<K8K@FE F= =I<<8@I
>I8M@KP ;8K8 9P -8E;N<CC <K 8C  8E; F= JLIT:@8C J@;< J:8E JFE8I
;8K8 @E K?< :<EKI8C ,<; -<8 '@K:?<CC 8E; L>LJK@E  .?< >I8M
@KP T<C; J?FNJ D8EP C@E<8I =<8KLI<J :IFJJ@E> K?< :<EKI8C ,<; -<8 @E ;@
I<:K@FEJ JL9G8I8CC<C N@K? K?< GC8K< JGI<8;@E> ;@I<:K@FE .?<J< 8I< J@D
@C8I DFIG?FCF>@:8CCP @E >I8M@KP ;8K8 KF JCFNJGI<8;@E> D@;F:<8E I@;><
JGI<8;@E> :<EK<IJ” “#= :FII<:K D8>E<K@: 8EFD8C@<J D8P 9< 8KK<EL8K<;
8J 8 :FEJ<HL<E:< F= >I<8K<I ;<GK? F= K?< :ILJK 8JJF:@8K<; N@K? K?< CF8;
@E> 9P K?< <M8GFI@K<J N?@:? I<8:? J<M<I8C BD @E K?@:BE<JJ 8N8P =IFD
K?< 8O@J @E J<@JD@: ;8K8'@K:?<CC 8E; L>LJK@E 
.?< JL>><JK@FE 9P '@K:?<CC <K 8C  K?8K K?< <M8GFI@K<J FI@>@
E8CCP ?8; 8 U8K ?FI@QFEK8C JLI=8:< 8K K?< <E; F= K?< '@F:<E<D8P EFK

UNCORRECTED PROOF
M. Hovland et al. Marine and Petroleum Geology xxx (2018) xxx-xxx
Fig. 15. !<FCF>@:8C D8G F= K?< ,<; -<8 8I<8 N?<I< K?< FLKC@E< F= K?< I89@8E (L9@8E
-?@<C; (- @J :C<8ICP J<<E .?< D8@E GCLKFE@: 8E; MFC:8E@: LE@KJ JLIIFLE;@E> K?< ,<; -<8
8I< C@JK<; @E K?< D8G C<><E; 8E; 8I< >@M<E 8J (<FGIFK<IFQF@: KF 8D9I@8E
'8 GCLKFE@: IPF><E@8E 8E; ;@8:8I8E '8 J<;@D<EK8IP 8E; MFC:8EFJ<;@
D<EK8IP *8C<F><E< '8 MFC:8E@: +L8K<IE8IP '8 MFC:8E@: '8G DF;
@T<; =IFD )E< !<FCF>P?KKGGFIK8CFE<><FCF>PFI>)E<><FCF>P!CF98C  FI @EK<I
GI<K8K@FE F= K?< I<=<I<E:<J KF :FCFI @E K?@J T>LI< C<><E; K?< I<8;<I @J I<=<II<; KF K?< 1<9
M<IJ@FE F= K?@J 8IK@:C<
9< :FII<:K @= K?< ;<GFJ@K@FE F= J8CK N8J 8 I<JLCK F= ?P;IFK?<ID8C 8:K@M
@KP 8E; K<:KFE@: GIF:<JJ<J @E K?< TIJK GC8:< .?< @JFJK8K@: <==<:KJ F= J8CK
;<GFJ@KJ D8P 8CJF 9< @EK<IGI<K<; ;@==<I<EKCP #= 8 D8JJ F= <M8GFI@K<J @J
CF8;<; FEKF 8 CF:8C 8I<8 F= K?< F:<8E@: :ILJK K?< :ILJK N@CC JL9J@;<
KF D8@EK8@E @JFJK8K@: 98C8E:< "FN<M<I K?< JL9J@;<E:< N@CC 9< C@D@K<;
8E; JCFN ;L< KF K?< CFN ;<EJ@KP F= J8CK <>  >:DXW M<IJLJ 
>:DXW =FI K?< LE;<ICP@E> D8EKC< D8JJ<J
E 8CK<IE8K@M< <OGC8E8K@FE 9P K?< ?P;IFK?<ID8C J8CK DF;<C @J K?8K
J8CK @J KI8EJGFIK<; LGN8I;J =IFD K?< ;<<G 9P ?P;IFK?<ID8C UFN 8E; ;<
GFJ@K<; 8J JFC@; J8CK FEKF K?< J<8UFFI LGFE :FFC@E> @E GFE;J F= ?@>?;<E
J@KP 9I@E<J .?< I<DFM8C F= J8CK =IFD 9<CFN N@CC :8LJ< 8 J@DLCK8E<FLJ
JL9J@;<E:< F= K?< J<8UFFI KF D8@EK8@E D8JJ 98C8E:<  K<:KFE@: JHL<<Q
@E>F= J8CK JCLII@<J FI ;L:K@C< J8CK =IFD K?< ;<<G =8LCKJ 8JJF:@8K<; N@K?
?P;IFK?<ID8C UFN LG @EKF K?< 98J@E N@CC @E;L:< 8 J@D@C8I <==<:K KF D8@E
K8@E D8JJ 98C8E:<
5.4. Salt-cored ridges in half-grabens, northern red sea
#E K?< EFIK?<IE ,<; -<8 '8IK 8E; ,FJJ  ;<J:I@9<; ELD<I
FLJ ;@8G@IJF::LII@E> @E N8K<I ;<GK?J I8E>@E> =IFD  KF  D
"FMC8E; <K 8C  .?<P 8I< KPG@:8CCP <CFE>8K<; 8KK8@E@E> C<E>K?J
<O:<<;@E> BD 8E; N@;K?J F= BD 8E; K?<P 8I< <@K?<I <OGFJ<; FI
:FM<I<; 9P LG KF FE< BD F= J<;@D<EKJ .?<J< ;@8G@IJ:FDDFECP ?8M<
=FID<; <@K?<I 8CFE> K?< 9FLE;8IP =8LCKJ F= ?8C=>I89<EJ =FID<; 9P <O
K<EJ@FE8C I@=K@E> FI @EJ@;< K?< I@=K UFFIJ )E< F= K?< DFJK GIFEFLE:<;
GFJ@K@M< =<8KLI<J @J D N@;< 8E; I@J<J 8K C<8JK  D 89FM< K?< J<;
@D<EK:FM<I<; J<89<;
-FD< ;@8G@IJ8I< 8CJF KFGG<; 9P E<>8K@M< :FCC8GJ<JKIL:KLI<J FE<
F= N?@:? D<8JLI<J BD 8:IFJJ 8E; D @E ;<GK? '8IK 8E; ,FJJ
 @EK<IGI<K<; K?<J< KF I<GI<J<EK J8CK ;@JJFCLK@FE G@KJ "FMC8E; <K
8C  @EK<IGI<K<; K?<J< I@;><J 8E; ;@8G@IJKF I<GI<J<EK GI@D8IP
J8CK @EA<:K@K<J 8E; <OKI8;@K<J @< ?P;IFK?<ID8C 8E; K<:KFE@: =<8KLI<J
.?LJ K?< @EK<IGI<K8K@FE F= K?<J< E<>8K@M<JKIL:KLI<J FE KFG F= K?<
;@8G@IJ8I< K?8K ?P;IFK?<ID8C M<EK@E> @J FE>F@E> N@K? ;<GFJ@K@FE F=
J8CKJ 8IFLE; K?< FG<E@E> F= K?< M<EKJ @< K?< FGGFJ@K< F= ;@JJFCLK@FE
.?@J D<8EJ K?8K K?< 8::LDLC8K@FE F= J8CK E<8I K?< J<89<; @J 8E FE>F@E>
GIF:<JJ 8J @J 8CJF <M@;<E:<; @E K?< =FCCFN@E> F9J<IM8K@FEJ 8E; =<8KLI<J
5.5. Red Sea Deeps
CFE> K?< :<EK<I F= K?< BD CFE> ,<; -<8 K?<I< 8I< DFI<
K?8E  CF:8C <<GJ,8JLC <K 8C  L>LJK@E <K 8C  
.?<J< 8:K@M< JGI<8;@E> :<EK<IJ '@K:?<CC <K 8C  ?FJK ?P;IFK?<I
D8C :@I:LC8K@FE :<CCJ 8E; JFD< F= K?< ;<<G<JK KIFL>?J :FEK8@E ?FK 9I@E<J
?I?8I;K 8E; "ü9J:?<I  "FN<M<I K?< <O8:K CF:8K@FEJ F= K?< ?P
;IFK?<ID8C M<EKJ K?8K =<<; K?< 9I@E< GFE;J 8I< JK@CC EFK BEFNE 9<:8LJ<
K?< 9I@E< JGI<8;J FM<I K?< <EK@I< 9FKKFD F= K?< 98J@EIFFBJ <K 8C
 .?I<< F= K?< ,<; -<8 <<GJ KC8EK@J ## <<G .?<K@J <<G 8E;
'898?@JJ <<G 8I< :?FJ<E KF ;@J:LJJ K?< ?P;IFK?<ID8C GIF:<JJ<J 8E;
J8CK ;<GFJ@K@FE @E K?< ,@=K 9<:8LJ< K?<J< <<GJ 8I< N<CC :?8I8:K<I@Q<;
9P I<:<EK ;8K8
5.5.1. The Atlantis II deep
::FI;@E> KF EJ:?LKQ  .?< KC8EK@J ## <<G @J FE< F= K?<
DFJK I<D8IB89C< J<8UFFI J<KK@E>J F= K?< GC8E<K #K @J K?< C8I><JK BEFNE
GI<J<EK;8P JL9D8I@E< ?P;IFK?<ID8C <EM@IFED<EKJ :FEJ@JK@E> F= 8
BDX KFGF>I8G?@: ;<GI<JJ@FE CF:8K<; @E K?< 8O@8C KIFL>? F= K?< ,<;
-<8 8K  D ;<GK? .?< ;<GI<JJ@FE KI8GJ ?FK 8E; ;<EJ< 9I@E<J =<; 9P
?P;IFK?<ID8C UL@;J K?< JFLI:< F= N?@:? ?8M< EFK P<K 9<<E J8DGC<;
 @> 
Fig. 16.  J?8;<;I<C@<= 98K?PD<KIP D8G F= K?< KC8EK@J ## 8E; @J:FM<IP <<GJ DF;@T<;
=IFD L>LJK@E <K 8C  .?< KNF I<; ;FKJ D8IB<; 8E; 8I< K?< CF:8K@FEJ F=
K?< KNF J@K<J ;I@CC<; 9P -* <<G -<8 I@CC@E> *IFA<:K &<>  @E  .?< 9CL<KFE<;
:<EKI8C 8I<8 @E;@:8K<J K?< I<>@FE N?@:? @J ;<MF@; F= UFN@E> J8CK <M@;<E:<; 9P UFNC@E<J
FE K?< JLI=8:< F= K?< JC@;@E> G@EB J8CK J<< 8CJF E<OK @D8>< @>   FI @EK<IGI<K8K@FE
F= K?< I<=<I<E:<J KF :FCFI @E K?@J T>LI< C<><E; K?< I<8;<I @J I<=<II<; KF K?< 1<9 M<IJ@FE F=
K?@J 8IK@:C<

UNCORRECTED PROOF
M. Hovland et al. Marine and Petroleum Geology xxx (2018) xxx-xxx
.?< TIJK 8:KL8C ?<8KUFN <JK@D8K<J @E K?< ,<; -<8 <<GJ N<I< ;FE<
9P EJ:?LKQ <K 8C  8E; N<I< :8C:LC8K<; KF 9<KN<<E  8E;
D1DX .?<P 8CJF EFK<; K?8K K?< I8E>< F= ?<8KUFN M8CL<J :FI
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<<GJ @E K?< ,<; -<8 LE;<I>F JK8><J F= ?<8K@E> <> 9P J@>E@=@:8EK ?P
;IFK?<ID8C 9I@E< ;@J:?8I>< 8CK<IE8K@E> N@K? HL@<K G<I@F;J :?8I8:K<I@Q<;
9P :FFC@E> EJ:?LKQ <K 8C  .?LJ @K @J <OG<:K<; K?8K K?< KI8EJ@
K@FE =IFD K?< :FEK@E<EK8C I@=K@E> JK8>< KF K?< F:<8E@: :ILJK8C JK8>< D8P
9< <HL@M8C<EK KF N?8K (FIKFE <K 8C  I<=<I KF 8J incipient/intrusive
oceanic crust .?<@I ELD<I@:8C DF;<C GI<;@:KJ K?8K @K @J @E K?@J JK8>< K?8K
J8CK @J =FID@E> 8E; TCC@E> K?< I@=K98J@E @E 8 M<IP I8G@; GIF:<JJ <>
JK8>< 8E; @E @>  *8IK  "FMC8E; <K 8C 
::FI;@E> KF K?< ?P;IFK?<ID8C J8CK DF;<C JL:? G<I@F;J N@K? D8J
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J8CKJ N@CC @E;L:< ;I8D8K@: JL9J@;<E:< 8E; J<8UFFI :FCC8GJ<  @>J 
8E; 
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@EJ@;< 8E; 8;A8:<EK KF K?< KC8EK@J ## <<G K?<I< N8J 8 EFK89C< 8C
K?FL>? C@D@K<; JLIM<P :FE;L:K<; @E  FN<I  .?@J :IL@J<
N8J ILE N@K? K?< M<JJ<C ,0 ):<8ELJ8E; @K ;@J:FM<I<; J<<G8>< F=
9I@E<J E8D<; K?< ):<8ELJ -<<G 8CFE> K?< N<JK<IE N8CC F= K?< :<EKI8C
I@=K M8CC<P "<I< 8K D ;<GK? K?< 8D9@<EK J<8N8K<I K<DG<I8KLI<
N8J ° 8E; K?< K<DG<I8KLI< F= K?< ):<8ELJ J<<G N8K<I N8J °
FN<I  ;A8:<EK KF K?< ):<8ELJ -<<G K?<P 8CJF ;@J:FM<I<; JFD<
;@==LJ@M< J<<GJ K J<M<I8C GFJ@K@FEJ 8 K?@:B C8P<I F= JC@>?KCP N8ID
J8C@E< N8K<I N8J F9J<IM<; 8K K?< 9FKKFD LII<EK D<8JLI<D<EKJ @E;@
:8K< K?8K K?<J< K?@E ;<EJ< C8P<IJ N<I< UFN@E> ;FNEJCFG< .?@J JL>><JKJ
K?8K ;<EJ< 9I@EP N8K<I @J J<<G@E> FLK F= K?< N8CCJ F= K?< I@=K M8CC<P 8E;
UFN@E> ;FNE K?< N8CCJFN<I 
EJ:?LKQ  ;@J:LJJ<; K?< :FDGFJ@K@FE F= K?< 9I@E< @E K?< K
C8EK@J ## <<G .?< J8KLI8K@FE @E;@:<J I<M<8C K?8K K?< 9I@E< @J LE;<IJ8K
LI8K<; N@K? I<JG<:K KF ?8C@K< >PGJLD 8E; 8E?P;I@K< 8K @E J@KL K<DG<I8
KLI< 'FEE@E 8E; ,8D9FQ  EJ:?LKQ <K 8C  JL>><JK@E> K?8K
K?< D8AFI J8CK :FE:<EKI8K@FEJ 8I< EFK :FEKIFCC<; 9P @E J@KL <HL@C@9I@LD F=
K?< 9I@E< GFFC N@K? I<JG<:K KF J8CK D@E<I8CJ .?< 9I@E< @J :CFJ< KF <HL@C@9
I@LD N@K? ?8C@K< 8K 8 K<DG<I8KLI< :CFJ< KF K?8K F= ,<; -<8 9FKKFD N8K<I
° N?@:? JLGGFIKJ K?< ?PGFK?<J@J K?8K K?< J8C@E@KP F= K?< @E:FD@E>
9I@E< ?8J 9<<E I<8:?<; K?IFL>? <HL@C@9I@LD N@K? <M8GFI@K< D@E<I8CJ 8K
J<8N8K<I K<DG<I8KLI< 9<=FI< ?<8K@E> F= K?< JFCLK@FE K?IFL>? =I8:KLI<;
,<; -<8 98J8CK@: :ILJKEJ:?LKQ 
E 8CK<IE8K@M< @EK<IGI<K8K@FE F= K?<J< F9J<IM8K@FEJ @J K?8K ?P;IFK?<I
D8C 9I@E<J J8KLI8K<; N@K? J8CKJ 8K ?@>?<I K<DG<I8KLI<J @E K?< ;<<G D8P
GI<:@G@K8K< J8CKJ C@B< ?8C@K< LGFE :FFC@E> ;LI@E> K?< 8J:<EK 8E; 8K K?<
J<8UFFI @= EFK ;@CLK<; 9P CFN;<EJ@KP 9I@E< "FN<M<I ?@>?JFCL9@C@KP
J8CKJ N@CC EFK GI<:@G@K8K< 8E; D8@EK8@E ?@>? J8C@E@KP @E K?< 9I@E<J 8K K?<
9FKKFD F= K?< <<G .?@J @J G8IK@:LC8ICP K?< :8J< N@K? K?< ?@>?CP JFCL9C<
D8>E<J@LD 8E; GFK8JJ@LD :?CFI@;<J K?8K 8CCFNJ K?<D KF JK8P @E JFCLK@FE
@E K?< 9I@E< GFE; FI KF <J:8G< N?<E ?8C@K< GI<:@G@K8K<J
5.5.2. The Mabahiss Deep
'<KQ  @EM<JK@>8K<; K?< '898?@JJ <<G CF:8K<; 8K °( FE
K?< :<EKI8C ,<; -<8 I@=K 8O@J 8;A8:<EK KF 8 C8I>< MFC:8E@: JKIL:KLI<
ʻ'898?@JJ 'FEJʻ .?@J JL9D8I@E< MFC:8EF :FM<IJ 8E 8I<8 F=  BDX
8E; I<GI<J<EKJ FE< F= K?< C8I><JK @E;@M@;L8C MFC:8E@: JKIL:KLI<J 8CFE> K?<
=I@:8E I89@8E I@=K JPJK<D  @> 
'<KQ  J8DGC<; 98J8CK =IFD K?@J JL9J<8 MFC:8EF 8E; @;<EK@
T<; K?< E<N=FID<; D@E<I8C GLDG<CCP@K< N?@:? JKIFE>CP @E;@:8K<J @E
K<ID<;@8K< KF CFN K<DG<I8KLI< ° ?P;IFK?<ID8C 8:K@M@KP @E
K?< JLIIFLE;@E>J F= K?< MFC:8EF LIK?<IDFI< ?< :8I<=LCCP 8E8CPJ<; K?<
DFIG?FCF>P F= K?< MFC:8EF 8E; @KJ <<G 8E; I<8:?<; JFD< @EK<I<JK
@E> :FE:CLJ@FEJ =FI <O8DGC< K?8K K?< JDFFK? UFFI F= K?< '898?@JJ
<<G C@B<CP I<GI<J<EKJ K?< JLI=8:< F= K?< LGG<I F:<8E@: :ILJK FCCFN
@E> FLK<CC< <K 8C  K?< JK<GN@J< DFIG?FCF>P 8CFE> K?< '898?@JJ
<<G 1<JK<IE 8J@E I<JLCKJ =IFD CF:8C JL9J@;<E:< ;L< KF K?< >I8;
L8C @E@K@8K@FE F= FI>8E@Q<; J<8UFFI JGI<8;@E> K?< U8K ;<GI<JJ@FE DFJK
C@B<CP I<GI<J<EK@E> K?< FLK:IFGG@E> F:<8E@: 98J<D<EK 8E; CF:8K@FE F=
Fig. 17. <8KLI<J I<:FI;<; 9P '<KQ  8;A8:<EK KF K?< 8:K@M< :<EKI8C MFC:8EF '898?@JJ 'FEJ@E K?< :<EKI8C ,<; -<8 'F;@T<; =IFD '<KQ  (FK< ?FN J8CK @J UFN@E> ;FNE
K?< U8EBJ 8E; KFN8I;J K?< '898?@JJ <<G N?@:? @J JLJG<:K<; UFFI<; 9P F:<8E@: :ILJK LIK?<IDFI< K?< ( 8EPFE LGG<I I@>?K @J JL>><JK<; KF I<GI<J<EK 8 I8M@E< K?IFL>? J<;@D<EKJ
<M8GFI@K<J <IF;<; 9P J<<G@E> N8K<I9I@E<J <> JGI@E> J8GG@E> )I8E>< <K 8C   FI @EK<IGI<K8K@FE F= K?< I<=<I<E:<J KF :FCFI @E K?@J T>LI< C<><E; K?< I<8;<I @J I<=<II<; KF K?< 1<9
M<IJ@FE F= K?@J 8IK@:C<

UNCORRECTED PROOF
M. Hovland et al. Marine and Petroleum Geology xxx (2018) xxx-xxx
K?< (1-JKI@B@E> I@=K 8O@J !L<EEF: <K 8C ” “"FN<M<I K?<
I<JLCK@E> 8>< F= 8K C<8JK  '8 8>I<<J N@K? G8C<FD8>E<K@: ;8K8 9P
!L<EEF: <K 8C  N?@:? JK8K< K?< FEJ<K F= F:<8E@: :ILJK 8::I<K@FE
@E K?< 8I<8 8K  '8 .?<J< TE;@E>J JFD<N?8K :?8CC<E>< K?< 8JJLDG
K@FE 9P F:?I8E  K?8K 8:K@M< J<8UFFI JGI<8;@E> @E K?< '898?@JJ
<<G 8I<8 DLJK 9< PFLE><I K?8E  '8'<KQ 
-8CK UFNJ I<GI<J<EK 8 ;FD@E8K@E> =<8KLI< @E K?@J <<G 8::FI;@E>
KF '<KQ  J<< @>  -8CK UFNJ 8I< L9@HL@KFLJCP GI<J<EK 8CFE>
K?< D8I>@EJ F= K?< 1<JK<IE 8J@E LIK?<I ;FNEJCFG< I<GC<E@J?D<EK 8E;
JL9J<HL<EK FM<IUFN F= K?< ;<<G @J @E?@9@K<; 9P K?< 9LC>@E> GI<J<E:< F=
K?< '898?@JJ 'FEJ <;@T:< 8E; 8 GIFKIL;@E> GC8K<8LC@B< =FID8K@FE F=
K?< C18A? ;FD8@E KF K?< EFIK?N<JK 8E; EFIK?<8JK I<JG<:K@M<CP
'<KQ  8CJF GL9C@J?<; 8 JK<I<F 8E8>CPG? D8G F= K?<
'898?@JJ <<G I<>@FE J?FN@E> ?@>?I<JFCLK@FE J<8UFFI 98K?PD<KIP
8I<=LC 8E8CPJ@J F= K?@J @D8>< :C<8ICP J?FNJ K?< F::LII<E:< F=
GF@EKJFLI:< <IFJ@FE @E K?< J:8IG8E; 8K K?< 9FKKFD F= K?< ( 8EPFE
I8M@E< @>  .?< <J:8IGD<EK 5J:8IG@E @> 6 JLI=8:< 8GG<8IJ
KF 9< ?<8M@CP TJJLI<; @E JCFG<G8I8CC<C ;@I<:K@FE 8E; ;<M<CFGJ @EKF 8E
8KI@LDJ?8G<; =FID8K@FE KFN8I;J K?< N<JK K?<I<9P :CFJ<CP I<J<D9C@E>
K?< <>>9FO G8KK<IEI<:F>E@Q<; 9P *@C:?<I 8E; CLDJK<@E  8CFE>
J8CK =IFEKJ @E K?< )I:8 8J@E !LC= F= '<O@:F'<KQ 
5.5.3. The Thetis Deep
.?< .?<K@J <<G N8J <OGCFI<; 9P *@<II<K <K 8C  8E; '@K:?<CC <K
8C   8E; K?<P ;@J:FM<I<; 8E 8GG8I<EK 8EFD8CP @E K?@J G8IK@:
LC8I <<G <JG@K< @K 9<@E> 8 CF:8CCP <E:CFJ<; <<G KFK8CCP JLIIFLE;<;
9P ?@>?<I >IFLE; K?<I< 8I< EF ;<EJ< 9I@E<J KI8GG<; @EJ@;< @K .?@J @J I<
>8I;<; 8J 8EFD8CFLJ =FI KNF I<8JFEJ @ K?<I< 8I< D<K8CI@:? J<;@D<EKJ
8K K?< 9FKKFD F= K?< <<G JLJG<:K<; F= ?8M@E> 9<<E ;<GFJ@K<; 9P :FE
:<EKI8K<; ?P;IFK?<ID8C 9I@E<J *@<II<K <K 8C  8E; @@ K?<I< 8I<
J8CK UFNJ K?8K K<ID@E8K< @EJ@;< K?< <<G N@K?FLK @E:I<8J@E> K?< J8C@E@KP
F= K?< <E:CFJ<; 9F;P F= JK@CC N8K<I '@K:?<CC <K 8C  /CK@D8K<CP
K?< C8:B F= 8 9I@E< C8B< ?<I< D8P K?<I<=FI< ?8M< 8 JKIL:KLI8C FI@>@E @=
K<:KFE@: DFM<D<EKJ FE 9FLE;8IP N8CC =8LCKJ 8I< KFF JD8CC 8E;FI @E=I<
HL<EK J@>E@=@:8EKCP KF FVJ<K K?< ?<D@G<C8>@: 8E; <M8GFI@K< 9<;J KF 8CCFN
;@JJFCLK@FE N?@C< <M8GFI@K< UFN8>< 8E; J<89<; GIF:<JJ<J 8:K@E> FE JLI
=8:< ?<D@G<C8>@: J<;@D<EKJ 8I< :FEK@EL8CCP ?<8C@E> JL:? FVJ<KJ KF GI<
M<EK N8K<I :@I:LC8K@FE'@K:?<CC <K 8C 
#E K?< ;<J:I@GK@FE F= K?< .?<K@J <<G 9P '@K:?<CC <K 8C  
K?<P 8CJF @E=<I K?8K K?<I< @J 8:K@M< ?P;IFK?<ID8C 8:K@M@KP K?<I< *<I
?8GJ 9<:8LJ< 8EP MFC:8E@: 8E;FI ?P;IFK?<ID8C 8:K@M@KP @J =FIKL@KFLJCP
CF:8K<; 8N8P =IFD K?< <M8GFI@K< 9<;J :FE<J KF K?< -1 8E; - 8E;
9<:8LJ< F= K?< ?<D@G<C8>@: :FM<I I<C8K@M<CP C@KKC< F= K?< ?8C@K< ?8J
9<<E ;@JJFCM@E> 8E; :FEKI@9LK@E> KF 8 9I@E< C8P<I @E K?< .?<K@J <<G @E
K?< ><FCF>@:8CCP I<:<EK G8JK '@K:?<CC <K 8C 
#E :FEKI8JK KF K?@J :FE:CLJ@FE "FMC8E; <K 8C  F==<I<; 8 KFK8CCP
;@==<I<EK <OGC8E8K@FE 98J<; FE 8:K@M< ?P;IFK?<ID8C 8:K@M@KP @EJ@;< 8E;
9<E<8K? K?< .?<K@J <<G J <OGC8@E<; 9P "FMC8E; <K 8C  K?< ?P
;IFK?<ID8C J8CK DF;<C I<HL@I<J K?< G8IK@K@FE F= C8I>< HL8EK@K@<J F= :FE
;<EJ8K@FE N8K<I =IFD K?< G?8J< J<G8I8K@FE QFE< F= K?< ?P;IFK?<ID8C
JPJK<D @E K?< JL9JLI=8:< .?@J ?FK JLG<I:I@K@:8C N8K<I M8GFI 8K ;<E
J@KP 8IFLE;  >:DXW N@CC :FE;<EJ8K< 9P :FFC@E> ;LI@E> K?< LGN8I;J
8J:<EK K?LJ GIF;L:@E> ;@JK@CC<;N8K<I C<8M@E> ?@>? ;<EJ@KP 9I@E< 8E;
GI<:@G@K8K<; J8CK @E K?< ;<<G (LD<I@:8C DF;<C@E> J?FNJ K?8K K?@J N8
K<I M8GFI K<E;J KF <J:8G< LGN8I; @E K?< I<ULO QFE<"FMC8E; <K 8C
8 N?@:? @J CF:8K<; @DD<;@8K<CP 89FM< K?< ?FKK<JK QFE< F= K?< JPJ
K<D K?8K @J K?IFL>? K?< ;<<G<JK G8IKJ F= K?< <<GJ  @>J  8E; 
.?@J @J 8CJF JLGGFIK<; 9P &<:LD9<II@-8E:?<Q <K 8C  N?F NI@K<
.?< :F<O@JK@E> M8GFI G?8J< N?@:? 8J:<E;J DFI< I8G@;CP K?8E K?< C@H
L@; NFLC; KI8EJGFIK JLC=LI 8E; >FC; LGN8I;
.?<I< @J EF ;FL9K K?8K K?@J =I<J? ?FK N8K<I @J ?@>?CP :FIIFJ@M< KF
8EP E<8I9P 9F;P F= J8CK @E:CL;@E> K?< F9J<IM<; J8CK UFNJE8D8B@<IJ
@E K?< <<G .?LJ K?< M<EK@E> F= :FE;<EJ8K@FE N8K<I LG @EKF JFD< F=
K?< <<GJ @E:CL;@E> K?< .?<K@J <<G D8P ?@E;<I K?< =FID8K@FE F= 8
:FE:<EKI8K<; 9I@E< C8P<I 8E; D8P 8CJF I8G@;CP ;@JJFCM< K?< =IFEK F= K?<
J8CK UFNJ K?8K 8I< DFM@E> KFN8I;J K?< .?<K@J <<G .?@J ;PE8D@: 8E;
I<C8K@M<CP I8G@; GIF:<JJ D8P 8CJF <OGC8@E K?< JK<<G CF98K< J?8G< F= K?<
J8CK UFN K<ID@E8K@FEJ "FMC8E; <K 8C 
5.6. Salt walls and ridges inside Red Sea Deeps
CK?FL>? K?<I< 8I< ELD<IFLJ J8CK:FI<; I@;><J 8CFE> K?< U8EBJ F=
K?< EFIK?<IE ,<; -<8 '8IK 8E; ,FJJ  J@D@C8I I@;><J F= 8GG8I<EKCP
D8JJ@M< J8CK N<I< 8CJF ;@J:FM<I<; :IFJJ@E> FM<I J<M<I8C F= K?< <<GJ
F= K?< ,<; -<8 ::FI;@E> KF ?I?8I;K <K 8C  8E; ?I?8I;K 8E;
"ü9J:?<I  K?< FEI8; <<G @E K?< EFIK?<IE ,<; -<8 @J 8 GFFICP
LE;<IJKFF; 98J@E 8JJF:@8K<; N@K? I@=K@E> 8E; J?<8I 8::FDDF;8K@FE #K
?8J 8 J<I@<J F= 8EFD8CFLJ =<8KLI<J JFD< F= N?@:? ?I?8I;K <K 8C 
8E; ?I?8I;K 8E; "ü9J:?<I  JLJG<:K<; KF 9< J8CK ;@8G@I@JD 9P 8G
GCP@E> K?< :FEM<EK@FE8C <M8GFI@K< DF;<C  @> 
#EJK<8; F= @EK<IGI<K@E> K?< GI<J<EK<; I<U<:K@FE J<@JD@: ;8K8 @E
K?< :FEM<EK@FE8CD8EE<I N@K? =8LCK GC8E<J <K: 8E 8CK<IE8K@M< @EK<I
GI<K8K@FE @J JL>><JK<; N?<I<9P :LDLC@=FID J8CK 8::LDLC8K<; @E =8LCKJ
8E; =I8:KLI<J @E K?< ;<<G ?P;IFK?<ID8C JPJK<D 8I< GLJ?<; LGN8I;J KF
9< JHL<<Q<; LG 9P K<:KFE@: =FI:<J 8J ;L:K@C< J8CK D8JJ<J .?@J DF;<C
@J I<=<II<; KF 8J J8CK @EA<:K@K< @>  "FMC8E; <K 8C  .?<
GIF:<JJ @J JL>><JK<; KF 9< 8::FDG8E@<; 9P ?P;IFK?<ID8C UFN F= J8KL
I8K<; 9I@E<J 8E; J8CK JCLII@<J
Fig. 18. Left 98J<; FE @>  F= ?I?8I;K <K 8C  .?< G@EB :FCFI I<GI<J<EKJ 8DFIG?FLJ CFN I<U<:K@M@KP J<@JD@: :?8I8:K<I .?@J J@>E8KLI< FI :?8I8:K<I @J JL>><JK<; KF I<GI<J<EK
<@K?<I  FM<IGI<JJLI<; GFI<N8K<I FI  ?@>?J8C@E@KP 9I@E<J GFJJ@9CP ;L:K@C< :LDLC8K@M< J8CK Right "@>?I<JFCLK@FE *8I8JFLE; @D8>< J?FN@E> K?8K K?< ;@8G@I@: D8K<I@8C @J M<IP JK<<G
8E; K?8K @K @J DFJK GIF989CP <OKIL;<; FLK F= K?< J<8UFFI LE;<I GI<JJLI< I8K?<I K?8E 8::LDLC8K@E> 8J 8 DL; MFC:8EF =IFD 8 ;@JK@E:K :FE;L@K "FN<M<I ;L< KF K?< GI<JJLI< I<C<8J< 8EP
JLIGCLJ 9I@E< @E K?< J8CK N@CC M<EK KF K?< J<8N8K<I 8E; N@CC GIF989CP UFN ;FNE?@CC 8E; 8::LDLC8K< @EJ@;< K?< 8;A8:<EK FEI8; <<G  FI @EK<IGI<K8K@FE F= K?< I<=<I<E:<J KF :FCFI @E K?@J
T>LI< C<><E; K?< I<8;<I @J I<=<II<; KF K?< 1<9 M<IJ@FE F= K?@J 8IK@:C<

UNCORRECTED PROOF
M. Hovland et al. Marine and Petroleum Geology xxx (2018) xxx-xxx
5.7. Massive salt ?ows
.?< -* &<>  J:@<EK@T: ;I@CC@E> I<GFIK 8:KL8CCP :FE:CL;<J K?8K
K?<P J8DGC<; UFN@E> J8CK !@I;C<I 8E; 1?@KD8IJ?  "FN<M<I @K
N8J EFK 9<=FI<  ;<:8;<J C8K<I N?<E '@K:?<CC <K 8C  TIJK D8GG<;
K?< J<8UFFI F= K?< :<EKI8C ,<; -<8 N@K? JN8K? 98K?PD<KIP K?8K K?<P ;@J
:FM<I<; K?< C8I>< J8CK UFNJ @E K?< .?<K@J <<G  @>  8E; @E K?< K
C8EK@J ## ;<<G N?<I< K?< -* ;I@CC@E> CF:8K@FEJ 8E; N<I<
CF:8K<;  @>  .?@J C8KK<I CF:8K@FE @J J<<E KF 9< CF:8K<; @EJ@;< 8 J8CK
UFN 8I<8 J<<E FE @>  &8K<I DFI< ;<K8@C<; N@;<J:8C< D8GG@E> I<
M<8C<; K?8K K?<I< N<I< D8EP FK?<I :<EKI8C ,<; -<8 8I<8J K?8K ?8; UFN
JKIL:KLI<J @EK<IGI<K<; 8J DFM@E> J8CK <> L>LJK@E <K 8C 
.?< @EK<IGI<K8K@FE F= K?< UFN JKIL:KLI<J ?8J 9<:FD< DFI< ;<K8@C<;
I<:<EKCP 8E; @K ?8J 9<<E =FLE; K?8K K?< J8CK :8IG<KJ D8P UFN 8K 8 M<
CF:@KP F= DFI< K?8E D G<I P<8I  <C;<EJ 8E; '@K:?<CC  .?<J<
JLIGI@J@E>CP C8I>< J8CK UFNJ N<I< <JK@D8K<; KF ?8M< I<C@<=J F= 
D ::FI;@E> KF <C;<EJ 8E; '@K:?<CC  K?< UFN@E> D8K<I@8C @J
JLJG<:K<; KF :FEJ@JK F= 8 ;@JG<IJ@FE F= G8IK@:LC8K< JFC@; J8CK D@O<; N@K?
:C8JK@: J<;@D<EK G8IK@:C<J @E :FE:<EKI8K<; 9I@E< <> 8 J8CK JCLIIP 8J
8CJF JL>><JK<; 9P K?< -* &<>  ;I@CC@E> I<JLCKJ .?< GFJJ@9@C@KP F=
8 :FE:<EKI8K<; :FFC@E> 8E; GI<:@G@K8K@E> 9I@E< :FLC; 8CJF 9< 8;;<;
'@K:?<CC <K 8C  8E; <C;<EJ 8E; '@K:?<CC  @EK<IGI<K K?<J<
J8CK UFNJ KF F::LI 8J 8 :FEJ<HL<E:< F= '@F:<E< <M8GFI@K< ;@JJFCLK@FE
9P ?P;IFK?<ID8C 8:K@M@KP  J@D@C8I M@<N @J 8CJF ?<C; 9P L>LJK@E <K 8C
 8CK?FL>? K?<P ;F EFK D<EK@FE K?8K ?P;IFK?<ID8C GIF:<JJ<J 8I<
@EMFCM<; 9LK @E=<I K?8K K?< KI@>><I@E> D<:?8E@JD =FI K?< J8CK UFN @J
8 :FD9@E8K@FE F= ;@JJFCLK@FE 9P J<8N8K<I 8E; K<:KFE@: <OK<EJ@FE LI
K?<IDFI< K?<P K<ID K?< J8CK UFNJ submarine namakiers E8D<; 8=K<I
GC8JK@: JL98<I@8C DFM<D<EK F= >C8:@<IC@B< IF:B J8CK UFN@E> ;FNE K?<
%L?@(8D8BJ8CK ;FD< 8E; FK?<I J8CK ;FD<J @E K?< 8J?K@ I<>@FE F=
#I8E &<<J  .8C9FK  L>LJK@E <K 8C 
IFD K?<@I 8;;<; 98K?PD<KIP D8GG@E> L>LJK@E <K 8C  TE;
J@D@C8I J8CK UFNJ <JG<:@8CCP N<CC ;<M<CFG<; @E K?< #EK<I .IFL>? 4FE<J
#.4J N?<I< “… CFE>N8M<C<E>K? I<C8K@M< KF K?< ?LDDF:BP K<II8@E
@E K?< <<GJ C@E<8I I@;><J 8I< M@J@9C< @E D8EP I<>@FEJ” “1?<I< KNF
E8D8B@<IJ UFN@E> =IFD FGGFJ@K< J@;<J F= K?< I@=K D<<K 8 :<EKI8C :C<=K
FI JLKLI< @J ><E<I8CCP M@J@9C< .?< 98K?PD<KI@: ;8K8 8CJF J?FN E8D8B@<I
UFN I@;><J 8GG8I<EKCP ;<M@8K@E> 8IFLE; MFC:8EF<J 8E; MFC:8E@: I@;><J
FE K?< I@=K U8EBJ JL>><JK@E> K?8K K?<J< 8I< @EUL<E:@E> E8D8B@<I UFN
L>LJK@E <K 8C 
#E K?< ?P;IFK?<ID8C J8CK DF;<C "FMC8E; <K 8C  GI<;@:K K?8K
C8I>< HL8EK@K@<J F= ?P;IFK?<ID8CCP GIF;L:<; G8IK@:LC8K< J8CK N@CC 8::L
DLC8K< LE;<I>IFLE; @E K?< :<EKI8C J<:K@FEJ F= K?< ,<; -<8 .?<I<=FI<
K?< F9J<IM8K@FE F= K?<J< <OK<EJ@M< J8CK UFNJ @J K8B<E 8J 8EFK?<I @E;@:8
K@FE K?8K K?< ?P;IFK?<ID8C DF;<C @J I<8C@JK@: E @EK<I<JK@E> 8JG<:K F=
K?< ?P;IFK?<ID8C GIF:<JJ @J 8CJF K?8K K?< J8CK UFNJ J<<D KF <D8E8K<
=IFD K?< J@;<J F= K?< :<EKI8C >I89<E I8K?<I K?8E =IFD GF@EK JFLI:<J @E
J@;< K?< >I89<E ::FI;@E> KF L>LJK@E <K 8C  K?< CFE><JK ;@J
K8E:< =IFD K?< :<EKI8C 8O@J F= K?< ,<; -<8 ,@=K KF K?<@I JFLI:< 8I<8 @J LG
KF BD .?@J JL>><JKJ K?8K K?< J8CK UFNJ 8I< :FDGFJ<; F= 9FK? E<NCP
GI<:@G@K8K<; J8CK JCLII@<J 8E; FC;<I J8CKJ 8E; J<;@D<EKJ K?8K ?8M< 9<<E
DF9@C@Q<; 8E; 8I< :FD@E> LG K?< D8@E =8LCKJ 8CFE> K?< U8EBJ  @> 
8J 8CJF JL>><JK<; 9P '@K:?<CC <K 8C  <C;<EJ 8E; '@K:?<CC 
8E; L>LJK@E <K 8C 
5.8. Suggested analogues to the red sea
5.8.1. The South Atlantic rifting
.?< I@=K@E> 8E; FG<E@E> F= K?< -FLK? KC8EK@: @J JL>><JK<; KF 9< 8E
8E8CF>L< KF K?< ,<; -<8 ;<M<CFGD<EK .?< C8I><JK J8CK 98J@E @E K?< -FLK?
KC8EK@: @J K?< -8EKFJ 8J@E :?8I8:K<I@Q<; 9P C8I>< J8CK N8CCJ 8C@>E<;
8CFE> 8 EFIK? JFLK? ;@I<:K@FE @E K?< ;<<G<JK G8IK F= K?< 98J@E G8I8CC<C
KF K?< I@=K 8O@J 'F?I@8B <K 8C  'F?I@8B 8E; &<IFP  .?@J @J
J@D@C8I KF K?< F::LII<E:< F= K?< J8CK N8CCJ @E K?< EFIK?<IE ,<; -<8 '8IK
8E; ,FJJ 
Fig. 19. .FGF>I8G?@: =<8KLI<J @E K?< .?<K@J <<G 8 EFIK?<IE G8IK 9 JFLK?<IE G8IK : KI8EJ<:K 8:IFJJ K?< JFLK?<IE .?<K@J <<G CF:8K@FE J?FNE @E 9 'F;@T<; =IFD &@>@ <K 8C  8E;
L>LJK@E <K 8C 

UNCORRECTED PROOF
M. Hovland et al. Marine and Petroleum Geology xxx (2018) xxx-xxx
CJF @E K?< -8EKFJ 8J@E K?<I< @J <M@;<EKCP 8 M<IP :CFJ< I<C8K@FEJ?@G
9<KN<<E J8CK ;<GFJ@K@FE 8E; <G@JF;<J F= ?@>? ?<8KUFN <> 98J8CK@:
@EKILJ@M<J 8E; <OKILJ@M<J 8J ;<J:I@9<; 9P 8M@JFE <K 8C  .?<
I8Q@C@8E J8> 98J@E @J TCC<; N@K? :F8IJ< :C8JK@: 8CCLM@8C =8EJ @E K?< GIFO
@D8C 8I<8 N?@:? >I8;< C8K<I8CCP @EKF J?8CCFN N8K<I :8I9FE8K<J D8@ECP
JKIFD8KFC@K< 8E; K?IFD9FC@K< .?< :8I9FE8K<J N<I< GIF989CP ;<GFJ@K<;
@E 8E 8CB8C@E< C8B< …” “8J< C8M8J N<I< <E:FLEK<I<; @E K?< ,$-
N<CC @E K?< -8EKFJ 8J@E E<8I K?< 98J< F= K?< J8> :8I9FE8K<J …” 8M@JFE
<K 8C 
1@K? K?< 18CM@J ,@;>< 0FC:8E@: "@>? ;<M<CFG@E> KF K?< JFLK?
J?FIKCP 9<=FI< J8CK ;<GFJ@K@FE ;LI@E> K?< *8I8E8 MFC:8E@JD 8M@JFE <K
8C  K?<I< @J JKIFE> <M@;<E:< =FI 8 J@KL8K@FE I<D8IB89CP J@D@C8I KF
K?< GI<J<EK =8I8E8B@C&8B< J8C<IK8 C< MFC:8E@: J8CK JPJK<D E;
 @E;<<; 8M@JFE <K 8C  ;<J:I@9< 8 ?P;IFK?<ID8C J8CK =FID8K@FE
JPJK<D @E K?< -FLK? KC8EK@: :FDG8K@9C< N@K? K?< ?P;IFK?<ID8C DF;<C
.?< K?@:B K8:?P?P;I@K< C8P<IJ GI<J<EK @E K?< <M8GFI@K< J<HL<E:< NFLC;
EFK GI<:@G@K8K< =IFD EFID8C J<8N8K<I 8E; K?< DFJK C@B<CP <OGC8E8K@FE F=
K?<J< ;<GFJ@KJ @J K?8K K?<P 8I< ;<I@M<; =IFD ?P;IFK?<ID8C 8CK<I8K@FE F=
98J8CK $8:BJFE <K 8C  .?< G<I:FC8K@FE DF;<C K?IFL>? ?FK 98J8CKJ
GIF;L:<J <EI@:?<; J<8N8K<I N?@:? @J E<:<JJ8IP =FI K8:?P?P;I@K< GI<:@G
@K8K@FE8M@JFE <K 8C 
.?< I8Q@C@8E J8> 98J@E N?@:? 8CJF :FEK8@EJ 8CCLM@8CJ :8I9FE8K<J @E
:CL;@E> JKIFD8KFC@K<J 8E; D@:IF9@8C@K<J @J GIF989CP HL@K< J@D@C8I KF K?<
8CB8C@E< C8B<J @E K?< N<JK<IE 8ID F= K?< 8JK =I@:8E ,@=K , .?LJ @E
&8B< .8E>8EP@B8 K?<I< 8I< 8CJF JL:? ;<GFJ@KJ @E:CL;@E> D@:IF9@8C@K<J
>IFN@E> @E CF:8K@FEJ F= ><FK?<ID8C J<<G8><J F?<E  1< K?LJ
@E=<I K?8K K?@J C8B< @J 8K 8E <8IC@<I JK8>< F= I@=K ;<M<CFGD<EK :FDG8I<;
KF K?< 8JK<IE 8ID F= , N?<I< N< TE; DFI< 8:K@M< I@=K@E> @E:CL;@E>
?@>?<I ?<8KUFN 8E; 8:K@M< J8CK =FID8K@FE 8E; ;<GFJ@K@FE
5.8.2. The Guaymas Basin
EFK?<I :LII<EKCP 8:K@M< D8I@E< I@=K K?8K GIF989CP E<M<I N8J ;<J
@::8K<; @J K?< !L8PD8J 8J@E @E K?< :<EKI8C !LC= F= 8C@=FIE@8 -<@JD@:
KI8EJ<:KJ ?8M< I<M<8C<; 8 BD× BD N@;< 8E;  BD K?@:B '@F:<E<
 '8 <M8GFI@K< 9F;P LE;<I K?< J?<C= F= K?< <8JK<IE D8I>@E F= K?<
98J@E '@CC<I <K 8C  .?< J<KK@E> F= K?< 98J@E @E;@:8K<J JKIFE>CP 8
?P;IFK?<ID8C =FID8K@FE F= K?@J C8I>< <M8GFI@K< 9F;P
5.8.3. Stromatolites and hydrothermal venting
E @EK<I<JK@E> 8E8CF>L< KF K?< JKIFD8KFC@K<J 8E; D@:IF9@8C@K<J @E K?<
, 8E; K?< I8Q@C@8E J8> 98J@E @J K?< ;<J:I@GK@FE F= JL:? =<8KLI<J 8K K?<
J8C@E< 8E; 8CB8C@E< &8B< -F:FDG8 J@KL8K<;  D 89FM< J<8 C<M<C @E
K?< I><EK@E<8E E;<J ::FI;@E> KF 8Ií8J <K 8C  .?< N8K<I 8K
K?< J@K< F= JKIFD8KFC@K<J =FID8K@FE @J 8CB8C@E< ?PG<IJ8C@E< I@:? @E @EFI
>8E@: ELKI@<EKJ M<IP I@:? @E 8IJ<E@: 8E; N8ID  ° ;L< KF 8 ?P
;IFK?<ID8C @EGLK
.?@J D<8EJ K?8K 8CC K?I<< F= K?<J< F::LII<E:<J F= JKIFD8KFC@K<J @E
, I8Q@C@8E J8> 98J@E 8E; K?< I><EK@E<8E E;<J 8I< >IFN@E> 8K CF
:8C@K@<J N?<I< ?P;IFK?<ID8C 9I@E<J 8I< M<EK@E> J8C@E< 8E; 8CB8C@E< N8K<I
8K JC@>?KCP ?@>?<I K<DG<I8KLI<J K?8E K?< JLIIFLE;@E>J @E;@:8K@E> K?8K
K?<J< <EM@IFED<EKJ 8I< 8KKI8:K@M< KF K?@J B@E; F= 98:K<I@8C >IFNK? 9FK?
8K GI<J<EK 8E; @E K?< G8JK
6. Summary and conclusions
6.1. Formation of solid salt in the deep crust is an inevitable process
.?<IDF;PE8D@:J GI<;@:KJ K?8K J8C@E< N8K<IJ N@CC @E:I<8J< @E J8C@E
@KP N?<E JL9A<:K<; KF ?@>?<I GI<JJLI<J 8E; K<DG<I8KLI<J -8C@E< N8K<IJ
N@CC K?LJ JGC@K @EKF =I<J? N8K<I M8GFI N?@C< K?< I<D8@E@E> C@HL@; 9I@E<
@E:I<8J<J @E ;<EJ@KP 8J :FETID<; 9P <OG<I@D<EK8C I<J<8I:? 8K GI<J
JLI<J 8E; K<DG<I8KLI<J I<C<M8EK =FI K?< :FE;@K@FEJ ;<<G @E K?< 8IK?J
:ILJK
%EFNC<;>< 89FLK K?< J8CKN8K<I G?PJ@:F:?<D@:8C GIFG<IK@<J :FD
9@E<; N@K? K?<IDF;PE8D@:J K?8K :FEKIFC K?<@I 9<?8M@FI 8CCFN :FD
GLK<I98J<; DF;<C@E> F= K?< ?P;IFK?<ID8C GIF:<JJ<J @E K?< ;<<G :ILJK
.?< I<JLCKJ F= JL:? DF;<C@E> J?FN K?8K K?< <M<I J8CK@<I 9I@E<J :FEK@EL<
KF D@>I8K< =LIK?<I ;FNE KFN8I;J K?< ?<8K JFLI:< LEK@C JFC@; J8CK GI<:@G@
K8K<J .?< =FID8K@FE F= JFC@; J8CK @J K?<I<=FI< 8E @E<M@K89C< GIF:<JJ :FE
KIFCC<; 9P K?<IDF;PE8D@:J N?<E J<8N8K<I :@I:LC8K<J @E =8LCKJ 8E; =I8:
KLI<J ;I@M<E 9P K?< ?<8K F= N8ID D8>D8 9F;@<J FI @>E<FLJ @EKILJ@FEJ
6.2. Hydrothermal circulation along tectonic plate boundaries
.?< DFJK 8:K@M< QFE<J =FI ?P;IFK?<ID8C :@I:LC8K@FE F= J<8N8K<I 8I<
C@EB<; KF GC8K< K<:KFE@:J N?<I< ?@>? K<DG<I8KLI<J 8E; GI<JJLI<J GI<M8@C
@E K?< I@=K@E> 8E; JL9;L:K@FE QFE<J 8CFE> K?< GC8K< 9FLE;8I@<J 8JJF:@
8K<; N@K? K?< 1@CJFE :P:C<J
6.3. Re>ning of salts
'8I@E< J8CKJ ?8M< M<IP ;@==<I<EK JFCL9@C@K@<J 8CJF 8K <C<M8K<; K<DG<I
8KLI<J ,<TE@E> F= J8CKJ K8B<J GC8:< ;L< KF K?@J ;@==<I<E:< @E GIFG<IK@<J
8CJF ;LI@E> K?< ?P;IFK?<ID8C :@I:LC8K@FE F= J<8N8K<I9I@E< "8C@K< 9<
@E> K?< C<8JK JFCL9C< :?CFI@;< F= D8I@E< J8CKJ N@CC 9< K?< TIJK KF GI<:@G
@K8K< LGFE @E:I<8J<; J8KLI8K@FE F= 9I@E<J N?@C< K?< DFI< JFCL9C< J8CKJ
?8M< 8 K<E;<E:P KF <J:8G< K?< JPJK<D .?@J K<E;<E:P KF <J:8G< D8P 9<
:FLEK<I8:K<; @= K?< DFI< JFCL9C< J8CKJ 8I< 8CCFN<; KF 8::LDLC8K< @E 8
GIFK<:K<; <EM@IFED<EK <> 9I@E< C8B<J FI 8I@; J8CK G8EJ <> 8CCFC
K?@FG@8 FI @E ?PG<IJ8C@E< GFE;J FE K?< J<8UFFI 9<KN<<E J8CK JKF:BJ
;FD<J -L:? GC8:<J ?8M< K?< I@>?K G?PJ@:F:?<D@:8C :?8I8:K<I@JK@:J =FI
K?< :IPJK8CC@Q8K@FE F= <OFK@:J8CKJ C@B< K8:?P?P;I@K< N@K? @KJ ?@>? :FE
K<EK F= :IPJK8C N8K<I .?<J< J8CKJ 8I< LEJK89C< 8K 8KDFJG?<I@: :FE;@K@FEJ
;L< KF K?< 89JFIGK@FE F= ?LD@;@KP =IFD K?< 8@I
6.4. Subduction of oceanic crust
.?< F:<8E@: :ILJKJ 8I< :?8I8:K<I@Q<; 9P ?8M@E> GFIFJ@K@<J @E K?< FI
;<I F=  D8@ECP =I8:KLI< GFIFJ@KP -<8N8K<I :@I:LC8K@E> @E K?< ;<<G<I
G8IKJ F= K?<J< :ILJKJ D8P 9< JL=T:@<EKCP ?<8K<; LE;<I JL=T:@<EKCP ?@>?
GI<JJLI<J KF LE;<I>F G?8J< J<G8I8K@FE I<JLCK@E> @E K?< JKFI8>< F= ?@>?
;<EJ@KP 9I@E<J 8E; <M<E JFC@; J8CKJ .?< ;@J:FM<IP F= 9FK? CFN 8E;
?@>?J8C@E@KP N8K<I M<EK@E> FE K?< J<8 UFFI JKIFE>CP @E;@:8K<J K?8K JL:?
G?8J< J<G8I8K@FE K8B<J GC8:< F9J<IM<; @E K?< <<GJ F= K?< ,<; -<8
.?LJ K?< JL9;L:K@E> F:<8E@: :ILJK D8P 9< CF8;<; N@K? DFI< J8CK K?8E
D<I<CP @KJ J<8N8K<ITCC<; GFIFJ@KP
6.5. Salt in the subduction zones
-8CK 8E; ?<8MP 9I@E<J =FID 8IFLE; 8E; @EJ@;< JL9;L:K@E> JC89J FE:<
K?< I<C<M8EK GI<JJLI< 8E; K<DG<I8KLI< :FE;@K@FEJ 8I< D<K .?< J8CK I<
D8@EJ ?@;;<E @E K?< ;<<G LEC<JJ ;@JJFCM<; 8E; KI8EJGFIK<; M@8 :FE;L:K
@E> =8LCKJ KF K?< JLI=8:< 9P N8K<I I<C<8J<; =IFD JK<<G JC89J FI 9P C8K<I
I@=K@E> @E K?< I<>@FE GI<=<I89CP 8CFE> K?< JLKLI< QFE<
0FC:8E@JD @J KI@>><I<; 9P K?< I<C<8J< F= N8K<I =IFD K?< JL9;L:K@E>
JC89 .?LJ J8CKJ D8P 9< KI8EJGFIK<; KF K?< JLI=8:< =8:@C@K8K<; 9P MFC
:8E@JD 8E; 8JJF:@8K<; ?P;IFK?<ID8C 8:K@M@KP 8J ;<DFEJKI8K<; 9P K?<
?L>< 8::LDLC8K@FEJ F= J8CKJ ?@>? LG @E K?< E;<8E 'FLEK8@EJ "<I<
?P;IFK?<ID8C 9I@E<J 8I< M<EK@E> FLK 8K  D 89FM< J<8 C<M<C
89FM< K?< QFE<J F= JK<<G JL9;L:K@FE .?<J< :FE:<EKI8K<; 9I@E<J 8I<
<M8GFI8K@E> @E K?< ;IP :C@D8K< N?@:? @J 8CJF GIFK<:K@E> K?< J8CK =IFD
I<;@JJFCLK@FE
.?< J8CKJ ;<GFJ@K<; 8I< K?< I<JLCK F= J<M<I8C G?8J<J F= I<TE@E> 8:
:FI;@E> KF K?< ;@==<I<EK JFCL9@C@K@<J F= K?< M8I@FLJ J8CK KPG<J 8K K?< M8I@
FLJ GI<JJLI<J 8E; K<DG<I8KLI<J K?<P ?8M< <E:FLEK<I<; #E 8;;@K@FE K?<
N8K<IIF:B @EK<I8:K@FEJ ?8M< JLGGC@<; D8EP 8;;@K@FE8C @E>I<;@<EKJ @EKF

UNCORRECTED PROOF
M. Hovland et al. Marine and Petroleum Geology xxx (2018) xxx-xxx
K?< M<EK@E> 9I@E<J @E:CL;@E> 9FIFE 8E; C@K?@LD .?@J :8E <OGC8@E K?<
?L>< ;<GFJ@KJ F= 9FI8K<J @E K?< E;<J 8E; <CJ<N?<I<
6.6. Oceanic subduction
.?< :FDGC<O JL9;L:K@FE QFE<J @E K?< '<;@K<II8E<8E =FI <O8DGC<
9<E<8K? K?< D@; '<;@K<II8E<8E ,@;>< I<GI<J<EKJ 8 :8J< =FI JKL;P
@E> F:<8E@: JL9;L:K@FE "<I< K?< =I@:8E GC8K< @J JL9;L:K@E> LE;<I K?<
<><8E GC8K<  J<I@<J F= C8I>< ?PG<IJ8C@E< 9I@E< GFE;J ?8M< 9<<E ;@J
:FM<I<; FE K?< J<8UFFI N?<I< 9I@E<J 8I< :FD@E> LG =IFD K?< JL9;L:
K@FE QFE< .?< 9I@E< C8B<J 8I< =<; 9P ?P;IFK?<ID8C 9I@E<J K?IFL>? =8LCKJ
8E; =I8:KLI<J K?8K G<E<KI8K< ;FNE @EKF K?< QFE< F= K?< JL9;L:K@E> JC89
6.7. Continental rifting and salt
FEK@E<EK8C I@=K@E> @J :?8I8:K<I@Q<; 9P K?< =FID8K@FE F= 8 M8CC<P N@K?
?8C=>I89<EJ 8E; =8LCKJ FI@<EK<; @E K?< ;@I<:K@FE F= K?< M8CC<P C@EB<;
8CFE> K?< >I89<EJ 0FC:8E@JD @J :FDDFECP <E:FLEK<I<; @E K?< I@=K JPJ
K<DJ 8E; M<EK@E> F= ?FK ?P;IFK?<ID8C 9I@E<J K?8K =<<; J8C@E< C8B<J
M<E :FEK@E<EK8C I@=K M8CC<PJ N@K?FLK :FEK8:K N@K? J<8N8K<I 8I< M<EK@E>
JF;@LD :?CFI@;< 8E; FK?<I J<8 J8CKJ -<M<I8C :8J< JKL;@<J 8I< ;@J:LJJ<;
KF JL9JK8EK@8K< K?<J< @JJL<J <:8LJ< F= 8CC K?< J8CK 8::LDLC8K@FEJ @E I@=K
M8CC<PJ @E:CL;@E> D8I@E< J8CKJ @K @J :8LK@FLJCP JL>><JK<; K?8K I@=K@E> @J
:FDDFECP K8B@E> GC8:< @E FC; JL9;L:K@FE 8I<8J N?<I< hidden salt @E K?<
JL9;L:K@FE QFE< @J 9<@E> DF9@C@Q<; ;LI@E> I@=K@E> 9P K?< :@I:LC8K@FE F=
?FK ?P;IFK?<ID8C N8K<I K?8K @J @EK<I8:K@E> N@K? K?< IF:BJ
6.7.1. Case 1: the East African Rift (EAR)
.?< , :FEK8@EJ 8CC K?< :?8I8:K<I@JK@: GIFG<IK@<J F= :FEK@E<EK8C I@=K
@E> #E K?< EFIK?<IE G8IK F= K?< I@=K @E:CL;@E> K?< 8CCFC 8I<8 @E K?@FG@8
K?< J8CKJ 8I< ;FD@E8EKCP :?CFI@;<J N@K? (8 % '> 8 <K: GF@EK@E>
8K 8 D8I@E< FI@>@E .?< ?L>< J8CK ;<GFJ@KJ @E 8CCFC K?@FG@8 8I< =FID
@E> 9P 8J:<E;@E> 9I@E<J K?8K 8I< M<EK@E> FLK FE K?< JLI=8:< N?<I< K?<
J8CK @J GI<:@G@K8K@E> @E K?< ;IP :C@D8K< #E K?<J< :8J<J K?<I< @J 8 TE8C
JK8>< F= <M8GFI8K@FE @EMFCM<; .?< J8D< ;IP :C@D8K< GIFK<:KJ K?< J8CK
=IFD I<;@JJFCLK@FE .?< :FDGFJ@K@FEJ F= K?< J8CKJ @E;@:8K< 8 D8I@E< FI@
>@E 9LK D@O<; N@K? <C<D<EKJ C<8:?<; FLK =IFD 9I@E<IF:B @EK<I8:K@FEJ
;LI@E> K?< ?P;IFK?<ID8C :@I:LC8K@FE
#E K?< JFLK?<IE G8IK F= K?< , M8CC<P N< TE; J8CK ;<GFJ@KJ 8E; C8B<J
N@K? 89LE;8EK :FEK<EKJ F= JF;@LD :8I9FE8K<J 8E; 9@:8I9FE8K<J @E 8;
;@K@FE KF :?CFI@;<J <> &8B< (8KIFE 8E; &8B< '8>8;@ N?<I< K?<I< @J
GI<:@G@K8K@FE F= JF;8 .?@J @J <OGC8@E<; 9P K?< GI<J<E:< F= )X =IFD K?<
MFC:8E@: 8:K@M@KP :FD9@E<; N@K? ?@>? G" @E K?< N8K<I G?8J< .?< ?@>?
G" F= K?< 9I@E<J @E;@:8K<J K?< GI<J<E:< F= J<IG<EK@E@Q8K@FE GIF:<JJ<J 8K
;<GK? @< @EK<I8:K@FE 9<KN<<E ?FK ?P;IFK?<ID8C N8K<I 8E; ?FK D8>
D8K@: @EKILJ@FEJ
#K @J JL>><JK<; K?8K K?<J< JF;@LD J8CKJ 9FK? :8I9FE8:<FLJ 8E; :?CF
I@;<J 8I< DF9@C@Q<; hidden salt JKFI<; @E K?< IF:BJ =IFD K?< GI<M@FLJ
JL9;L:K@FE 8E; :FCC@J@FE 9<KN<<E 8JK 8E; 1<JK !FE;N8E8 K?8K =FIDJ
K?< 8JK =I@:8E )IF><E    '8 9<=FI< GI<J<EK
<:8LJ< F= 8CC K?< J8CK 8::LDLC8K@FEJ @E I@=K M8CC<PJ  ;FD@E8EKCP J8CKJ
F= D8I@E< FI@>@E @K @J :8LK@FLJCP JL>><JK<; K?8K I@=K@E> @J :FDDFECP K8B
@E> GC8:< 8CFE> K?< JLKLI< QFE<J F= FC; JL9;L:K@FE 8I<8J <> 1@CJFE
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Uncited references
$8:BJFE <K 8C  'F?I@8B <K 8C  .8C9FK 8E; $8:BJFE 
Acknowledgements
1< K?8EB KNF I<M@<N<IJ 0@KKFI@F -:I@98EF 8E; 1<9JK<I 'F?I@8B =FI
K?<@I :FEJKIL:K@M< :FDD<EKJ 8E; N< NFLC; 8CJF C@B< KF K?8EB GI<M@
FLJ :FE:<GKL8C ;@J:LJJ@FEJ 8E; ?<CG =IFD (8A<<9 ,8JLC 8E; ?8ICFKK< 
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References
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UNCORRECTED PROOF
M. Hovland et al. Marine and Petroleum Geology xxx (2018) xxx-xxx
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F:<8E @JC8E; 98J8CKJ =IFD I<E:? *FCPE<J@8 @DGC@:8K@FEJ =FI K?< < 8E; &@< I8K@FJ
8J KI8:<IJ F= JL9;L:K<; :FDGFE<EKJ '@E<I8C '8>  S L>LJK 
?I?8I;K  "ü9J:?<I   .?< EFIK?<IE ,<; -<8 @E KI8EJ@K@FE =IFD I@=K@E> KF ;I@=K
@E> C<JJFEJ C<8IE<; =IFD F:<8E ;<<GJ #E ,8JLC (' -K<N8IK #  ;J .?<
,<; -<8 K?< FID8K@FE 'FIG?FCF>P ):<8EF>I8G?P 8E; EM@IFED<EK F= 8 3FLE>
):<8E 8J@E -GI@E><I 8IK? -PJK<D -:@<E:<J <IC@E "<@;<C9<I> GG S
?I?8I;K  "ü9J:?<I  !8A<NJB@   FEI8; <<G (FIK?<IE ,<; -<8 ;<M<CFG
D<EK F= 8E <8ICP JK8>< F:<8E ;<<G N@K?@E K?< 8O@8C ;<GI<JJ@FE .<:KFEFG?PJ@:J 
S
I@:BJ<E ! 0@E< $ 8CCóE ,  ?<D@:8C :FDGFJ@K@FE 8E; ;@JKI@9LK@FE F=
C@K?@LDI@:? 9I@E<J @E J8C8I ;< /PLE@ 8E; E<8I9P J8C8IJ @E JFLK?N<JK<IE FC@M@8 E
<I>P   S
I@:BJ<E !  /GG<I .<IK@8IP 8E; +L8K<IE8IP :FEK@E<EK8C J8C@E< ;<GFJ@KJ @E K?< E
;<8E I<>@FE !<FC -F: 8E8;8 -G<: *8G<I  S
8::<EE8  <:B<I .1 L<I & @CC@  FJ:?@ & ILE $* 8G@K8E@F  L
E@:@<CCF  "FIMàK?  $FC@M<K & *@IFD8CCF  ,FP;<E & ,FJJ<KK@  -<IG<CCFE@
  '8EKC< ;PE8D@:J @E K?< D<;@K<II8E<8E ,<M !<FG?PJ  S ?KKGJ
;F@FI>,!
8Ií8J ' ,8J:FM8E ( .FE<8KK@ ' C98II8:íE 0" CFI<J ', *F@Ié !
FCC8M@EF '' >L@C8I )' 08QHL<Q '* *FC<I<:BP &  .?< ;@J:FM<IP F=
JKIFD8KFC@K<J ;<M<CFG@E> 8K  D 89FM< J<8 C<M<C @E 8 ?@>?8CK@KL;< MFC:8E@: C8B< -F
:FDG8 I><EK@E<8E E;<J *&F- )E<   < ?KKGJ;F@FI>AFLIE8C
GFE<
<C;<EJ * '@K:?<CC (  -8CK UFN@E K?< :<EKI8C I<; J<8 #E ,8JLC (' -K<N
8IK #  ;J .?< ,<; -<8 -GI@E><I 8IK? -PJK<D -:@<E:<J <IC@E "<@;<C9<I> GG
S
!@I;C<I ,1 1?@KD8IJ? ,  '@F:<E< <M8GFI@K<J @E ,<; -<8 :FI<J K?<@I I<C<M8E:<
KF K?< GIF9C<D F= K?< N@;K? 8E; 8>< F= F:<8E@: :ILJK 9<E<8K? K?< ,<; -<8 #E 1?@K
D8IJ? , 1<J<I * ,FJJ  ;J #E@K@8C ,<GFIKJ F= K?< <<G -<8 I@CC@E>
*IFA<:K 0FCLD<  /- !FM<IED<EK *I@EK@E> )=T:< 18J?@E>KFE GG S
!@I;C<I ,  .?< <MFCLK@FE F= K?< !LC= F= 8;<E 8E; I<; J<8 @E JG8:< 8E; K@D< <<G
-<8 ,<J *8IK  ):<8EF>I ,<J *8G  S
!@I;C<I ,  *IF9C<DJ :FE:<IE@E> K?< <MFCLK@FE F= F:<8E@: C@K?FJG?<I< @E K?< EFIK?
<IE ,<; -<8 .<:KFEFG?PJ@:J  S
!I8EK - !I8EK 1 $FE<J  %8KF  &@ &  (FM<C 8I:?8<8C G?PCFKPG<J =IFD
8E 8JK =I@:8E 8CB8C@E< J8CK<IE OKI<DFG?@C<J  S
!L<EEF: * *8LKFK ! FLK<CC<   -LIT:@8C JKIL:KLI<J F= K?< EFIK?<IE ,<; -<8
8O@8C M8CC<P =IFD °( KF °( K@D< 8E; JG8:< <MFCLK@FE F= E<FF:<8E@: JKIL:KLI<J
.<:KFEFG?PJ@:J  S
!L<EEF: * *8LKFK ! &< +L<EKI<: '  FLK<CC<   -KIL:KLI< F= 8E <8ICP
F:<8E@: I@=K @E K?< EFIK?<IE I<; J<8 ):<8EFC :K8   S
!LKJ:?<I ' )C@M<K $& JC8E@8E  @JJ<E $* '8LIP ,  .?< CFJK #E:8
*C8K<8L :8LJ< F= U8K JL9;L:K@FE 9<E<8K? *<IL 8IK? *C8E<K -:@ &<KK  
S
!LKJ:?<I ' -G8BD8E 1 @AN88I; " E>;8?C ,  !<F;PE8D@:J F= U8K JL9
;L:K@FE J<@JD@:@KP 8E; KFDF>I8G?@: :FEJKI8@EKJ =IFD K?< E;<8E D8I>@E .<:KFE@:J
  S
"8I;@< &  .?< IFC<J F= I@=K@E> 8E; ?P;IFK?<ID8C 8CX 9I@E<J @E K?< FI@>@E F=
GFK8J? <M8GFI@K<J 8E ?PGFK?<J@J D $ -:@  S
"FMC8E; ' @:?C<I  ,L<JCåKK<E " $F?EJ<E "% 8 <<G IFFK<; G@<I:<D<EK
JKIL:KLI<J @E ;<<G J<;@D<EK8IP 98J@EJD8E@=<JK8K@FEJ F= JLG<I:I@K@:8C N8K<I ><E<I8
K@FE 8K ;<GK? $ !<F:?<D OGCFI  S
"FMC8E; ' %LQE<KJFM8 . ,L<JCåKK<E " %M8DD<  $F?EJ<E "% C8;D8IB !
"<98:?  9 -L9JLI=8:< GI<:@G@K8K@FE F= J8CKJ @E JLG<I:I@K@:8C J<8N8K<I 8J@E
,<J  S
"FMC8E; ' ,L<JCåKK<E "! $F?EJ<E "% %M8DD<  %LQE<KJFM8 . : -8CK =FI
D8K@FE 8JJF:@8K<; N@K? JL9JLI=8:< 9F@C@E> 8E; JLG<I:I@K@:8C N8K<I '8I *<KIFC !<FC
 S
"FMC8E; ' ,L<JCåKK<E " $F?EJ<E "%  LI@<; ?P;IFK?<ID8C JPJK<DJ K?< GF
K<EK@8C IFC< F= JLG<I:I@K@:8C N8K<I-:I@1 @E M8I@FLJ ><FCF>@:8C GIF:<JJ<J 8E; F::LI
I<E:<J @E K?< JL9JLI=8:< D $ E8C ?<D  S
"FMC8E; ' ,L<JCåKK<E " $F?EJ<E "%  ,<; -<8 J8CK =FID8K@FEJ8 I<JLCK F= ?P
;IFK?<ID8C GIF:<JJ<J K?< ,<; -<8 #E ,8JLC (' -K<N8IK #  ;J .?< ,<;
-<8 -GI@E><I 8IK? -PJK<D -:@<E:<J <IC@E "<@;<C9<I> GG S
"FMC8E; ' ,L<JCåKK<E " $F?EJ<E "%  &8I>< J8CK 8::LDLC8K@FEJ 8J 8 :FEJ<
HL<E:< F= ?P;IFK?<ID8C GIF:<JJ<J 8JJF:@8K<; N@K? 1@CJFE :P:C<J 8 I<M@<N *8IK  KF
N8I;J 8 E<N LE;<IJK8E;@E> '8I *<KIFC !<FC ?KKGJ;F@FI>AD8IG<K><F

"FMC8E; ' ,L<JCåKK<E " $F?EJ<E "% '8EL<CC8   *FJJ@9C< IFC< F= J8CK 8::L
DL8CK@FEJ @E 1@CJFE :P:C<J #E 89JKI8:K *IF:<<;@E>J F= K?< IK?LI "FCD<J '<<K@E>
 !<FC -F: '8P  &FE;FE
"L>L<E  ?8DFK,FFB< ( &FL9I@<L  '8J:C< $  'FIG?FCF>P F= 8 GI<:FCC@
J@FE8C J8CK9<8I@E> 8::I<K@FE8IP :FDGC<O K?< '<;@K<II8E<8E ,@;>< <8JK<IE D<;@K<I
I8E<8E '8I !<FG?PJ ,<J  S
"LK:?@EJFE , E><CJ !   ;@J:LJJ@FE FE K?< JKIL:KLI< 8E; <MFCLK@FE F= K?< ,<;
-<8 8E; K?< E8KLI< F= K?< ,<; -<8 !LC= F= ;<E 8E; K?@FG@8 I@=K ALE:K@FE  K<:KFE@:
J@>E@=@:8E:< F= I<>@FE8C ><FCF>P 8E; <M8GFI@K< C@K?F=8:@<J @E EFIK?<8JK<IE K?@FG@8
*?@C .I8EJ '8K? *?PJ E> -:@  S ?KKGJ;F@FI>IJK8

$8:BJFE & $8:BJFE '* "L;<: ', ,F;I@>L<Q ,  E@>D8K@: JKIL:KLI<J
N@K?@E J8CK N8CCJ F= K?< -8EKFJ 8J@E  *8IK  ><FD<KIP 8E; B@E<D8K@:J =IFD  J<@J
D@: I<U<:K@FE 8E; N<CC ;8K8 $ -KIL:K !<FC  S
$8:BJFE '* I8D<Q  FE:B $'  ,FC< F= JL98<I@8C MFC:8E@: IF:BJ 8E; D8E
KC< GCLD<J @E :I<8K@FE F= -FLK? KC8EK@: D8I>@EJ @DGC@:8K@FEJ =FI J8CK K<:KFE@:J 8E;
JFLI:< IF:BJ '8I *<KIFC !<FC  S
$L;;  "FMC8E; '  -<89<; CL@; CFN #DG8:K FE !<FCF>P @FCF>P 8E; K?< '8
I@E< EM@IFED<EK 8D9I@;>< /E@M<IJ@KP *I<JJ 8D9I@;>< /%  GG
%8N8DFKF . 3FJ?@B8N8 ' %LD8>8@ 3 '@I89L<EF '". )BLEF ' %F98P8J?@
.  '8EKC< N<;>< @ETCKI8K<; N@K? J8C@E< UL@;J =IFD ;<?P;I8K@FE 8E; ;<:8I9FE
8K@FE F= JL9;L:K@E> JC89 *IF: (8KC :8; -:@ /E@K -K8K<J D  S
&8D9 -  <M@C @E K?< 'FLEK8@E 8 -<8I:? =FI K?< )I@>@E F= K?< E;<J *I@E:<KFE
/E@M<IJ@KP *I<JJ *I@E:<KFE (<N $<IJ<P
&8LDFE@<I ' !8@CC8I;  'L@I  CLE;P $ /EJNFIK? '  !@8EK D8>D8K@:
N8K<I I<J<IMF@IJ 8K D@;:ILJK8C ;<GK? @E=<II<; =IFD <C<:KI@:8C :FE;L:K@M@KP 8E; K?<
>IFNK? F= K?< :FEK@E<EK8C :ILJK 8IK? *C8E<K -:@ &<KK  S
&<:LD9<II@-8E:?<Q * -K<<C<'8:#EE@J ' 1<@J * I@<JE<I . F;E8I ,$ 
-8CK GI<:@G@K8K@FE @E D8>D8K@:?P;IFK?<ID8C JPJK<DJ 8JJF:@8K<; N@K? LGG<I :ILJK8C
GCLKFEJ !<FCF>P  S
&<<J !  -8CK JFD< ;<GFJ@K@FE8C 8E; ;<=FID8K@FE8C GIF9C<DJ JPDGFJ@LD FE J8CK
;FD<J $ #EJK *<K .<:?EFC S
&@>@ ' FE8KK@  ,8JLC ('  -<8UFFI JGI<8;@E> @E@K@8K@FE ><FG?PJ@:8C 8E; ><F
:?<D@:8C :FEJKI8@EKJ =IFD K?< .?<K@J 8E; (<I<LJ <<GJ :<EKI8C ,<; -<8 #E ,8JLC
(' -K<N8IK #  ;J .?< ,<; -<8 -GI@E><I <IC@E "<@;<C9<I> GG S
&@FL $! .JLA@DFI@ . 38E> $ 4?8E> , IEJK 1  ,<:P:C@E> F= :ILJK8C D8K<I@
8CJ K?IFL>? JKL;P F= LCKI8?@>?GI<JJLI< D@E<I8CJ @E :FCC@J@FE8C FIF><EJ FG?@FC@K<J 8E;
D8EKC< O<EFC@K?J 8 I<M@<N $ J@8E 8IK? -:@  S
&L>C@ - '8EQ@ 0 ,FM<I@ ' -:?I<@9<I   .?< ;<<G I<:FI; F= K?< '<JJ@E@8E
J8C@E@KP :I@J@J <M@;<E:< F= 8 EFE;<J@::8K<; D<;@K<II8E<8E J<8 *8C8<F><F>I *8C8<F
:C@D8KFC *8C8<F<:FC  S
'8E8 - LID8I . .LII@E  <@><EJFE ' -N@J?<I   '8>D8K@: 8:K@M@KP
8:IFJJ K?< 8JK =I@:8E EFIK? .8EQ8E@8E ;@M<I><E:< QFE< $ !<FC -F:  S
'8IK 3 ,FJJ   *FJK'@F:<E< I@=K@E> 8E; ;@8G@I@JD @E K?< EFIK?<IE ,<; -<8
'8I !<FC  S
'8IK@EF; $ "LJJFE & ,FG<I:? * !L@CC8LD<  JGLIK (  "FI@QFEK8C JL9;L:
K@FE QFE<J :FEM<I><E:< M<CF:@KP 8E; K?< 9L@C;@E> F= K?< E;<J 8IK? *C8E<K -:@ &<KK
 S
'<@C@AJFE  -K<@E9<I> $ "@C><E  @8C@B )' 18C;D8EE ( '8BFNJBP 3 
<<G98J@E <M@;<E:< I<JFCM<J 8 P<8IFC; ;<98K< 8E; ;<DFEJKI8K<J JPE:?IFEFLJ FE
J<K F= '<JJ@E@8E <M8GFI@K< ;<GFJ@K@FE @E 8 EFE;<J@::8K<; D<;@K<II8E<8E !<FCF>P
?KKGJ;F@FI>!
'<C8:B $' %@C?8D *  *?FKFJPEK?<K@: I8K<J F= G?PKFGC8EBKFE @E 8JK=I@:8E 8C
B8C@E< J8C@E< C8B<J &@DEFC ):<8EF>I  S
'<KQ   '898?@JJ 'FEJ  °( ,<; -<8 ,@=K .<:KFE@:J 8E; 0FC:8E@JD F= 8 &8I><
-L9D8I@E< FD< 0FC:8EF 8:LCKP F= '8K?<D8K@:J 8E; (8KLI8C -:@<E:< '-: ;@JJ<IK8
K@FE ?I@JK@8EC9I<:?KJ /E@M<IJ@KP F= %@<C %@<C !<ID8EP 
'@CC<I ( &@Q8II8C;<  "8I;@E>  %<EK !  FEJKI8@EKJ FE <8ICP !LC= F= 8C
@=FIE@8 I@=K@E> =IFD J<@JD@: @D8><J 8:IFJJ K?< <8JK<IE D8I>@E F= !L8PD8J 8J@E #E
9JKI8:K !/ 8CC '<<K@E> 8C@=FIE@8 <:<D9<I  *FJK<I .
'@K:?<CC ( L>LJK@E (  "8CFB@E<K@:J 8E; FK?<I =<8KLI<J F= !&),# CFE>I8E><
J@;<J:8E JFE8I ;8K8 =IFD K?< ,<; -<8 '8I@E< 8E; *<KIFC !<FC  S
'@K:?<CC ( &@>@ ' <C;<EJ * "ü9J:?<I   <=FID8K@FE F= 8 PFLE> J8CK >@8EK
I<>@FE8C KFGF>I8G?P F= K?< ,<; -<8 '@F:<E< <M8GFI@K<J 8J@E ,<J  S

UNCORRECTED PROOF
M. Hovland et al. Marine and Petroleum Geology xxx (2018) xxx-xxx
'@K:?<CC ( &@>@ ' <II8EK< 0 FE8KK@  ,'LKK<I   -L9D8I@E< J8CK UFNJ
@E K?< :<EKI8C ,<; -<8 !<FC -F: D LCC  S
'@K:?<CC ( *8IB 3  (8KLI< F= :ILJK @E K?< :<EKI8C I<; J<8 .<:KFEFG?PJ 
S
'@K:?<CC ( -:?D@;K ' &@>@ '  FDD<EK FE FID8K@FE F= .?<K@J <<G
D<K8CI@:? J<;@D<EKJ @E K?< 89J<E:< F= 9I@E<J ,<; -<89P *@<II<K <K 8C  $
!<F:?<D OGCFI  S
'F?I@8B 1/ &<IFP -  I:?@K<:KLI< F= I@=K<; :FEK@E<EK8C D8I>@EJ 8E; 9I<8BLG
<MFCLK@FE @EJ@>?KJ =IFD -FLK? KC8EK@: EFIK? KC8EK@: 8E; I<; J<8 !LC= F= 8;<E
:FEAL>8K< D8I>@EJ #E 'F?I@8B 1/ 8E=FIK?  *FJK *$ IFNE  .8I@
! (<D:FB ' -@E?8 -. ;J !<FCF>@:8C -F:@<KP &FE;FE -G<:@8C *L9C@:8K@FEJ
 GG S
'F?I@8B 1 (<DčFB ' E:@JF !  -FLK? KC8EK@: ;@M<I><EK D8I>@E <MFCLK@FE
I@=K9FI;<I LGC@=K 8E; J8CK K<:KFE@:J @E K?< 98J@EJ F= - I8Q@C !<FC -F: &FE; -G<:@8C
*L9C  S
'F?I@8B 1/ -Q8KD8I@ * EAFJ -  -8CK ><FCF>P 8E; K<:KFE@:J F= J<C<:K<; I8Q@C
@8E 98J@EJ @E K?<@I >CF98C :FEK<OK !<FCF>@:8C -F: &FE; -G<:@8C *L9C  S
'FD<EQ8;<? '  -8C@E< ;<GFJ@KJ 8E; 8CB8C@E< D8>D8K@JD 8 ><E<K@: DF;<C $
*<KIFC !<FC  S
'FEE@E  ,8D9FQ   .?< 8E?P;I@K< J8KLI8K@FE @E;<O F= K?< ,<; -<8 GFE;<;
9I@E<J 8E; J<;@D<EK GFI< N8K<IJ F= K?< ,<; -<8 ;<<GJ ?<D !<FC  S
(FIKFE #) 8IILK?<IJ . "L;<: ',  ,@=K KF ;I@=K KI8EJ@K@FE @E K?< -FLK? K
C8EK@: J8CK 98J@EJ 8 E<N U8MFI F= F:<8E@: :ILJK !<FCF>P   S ?KKGJ;F@
FI>!
)I8E>< & !I<<E< "! ,<<;  <K 8C  1@;<JGI<8; UL@; <OGLCJ@FE FE 8
KI8EJC8K@FE8C :FEK@E<EK8C D8I>@E DL; MFC:8EF<J =8LCK QFE<J ?<8;C<JJ :8EPFEJ 8E;
FI>8E@:I@:? JL9JKI8K<J @E 'FEK<I<P 8P 8C@=FIE@8 !<FC -F: D LCC 
S
*@<II<K ' C8L<I ( FJ:?  C8E: !  =FID8K@FE F= .?<K@J ;<<G D<K8CI@:? J<;
@D<EKJ @E K?< 89J<E:< F= 9I@E<J I<; J<8 $ !<F:?<D OGCFI  S
*@C:?<I ,- CLDJK<@E ,  I@E< MFCLD< 8E; J8CK ;@JJFCLK@FE I8K<J @E )I:8 8J@E
EFIK?<8JK !LC= F= '<O@:F *! D JJF: *<K !<FC LCC   S
*@I8AEF   "P;IFK?<ID8C *IF:<JJ<J 8E; '@E<I8C -PJK<DJ !<FCF>@:8C -LIM<P F=
1<JK<IE LJKI8C@8 -GI@E><I
,8JLC (' -K<N8IK # (8N89 4  #EKIF;L:K@FE KF K?< ,<; -<8 @KJ FI@>@E JKIL:
KLI< 8E; <EM@IFED<EK #E ,8JLC (' -K<N8IK #  ;J .?< ,<; -<8 -GI@E><I
8IK? -PJK<D -:@<E:<J <IC@E "<@;<C9<I> GG S
,<KK@> -& $FE<J   ,@J8:?<I   !<F:?<D@:8C <MFCLK@FE F= 9I@E<J @E K?< J8C8I F=
/PLE@ FC@M@8 ?<D !<FC   S 
,FM<I@ ' C<:B<I , %I@A>JD8E 1 <K 8C  .?< '<JJ@E@8E -8C@E@KP I@J@J G8JK 8E;
=LKLI< F= 8 >I<8K :?8CC<E>< =FI D8I@E< J:@<E:<J '8I !<FC  S
-8<DLE;JJFE %  8JK =I@:8E I@=K JPJK<D 8E FM<IM@<N -?FIK FLIJ< 0 FE OGCF
I8K@FE =FI !<FK?<ID8C ,<JFLI:<J 
-8E;N<CC  'üCC<I , -D@K? 1"  !8I:@8  I8E:@J ,  (<N >CF98C D8I@E<
>I8M@KP DF;<C =IFD IPF-8K 8E; $8JFE I<M<8CJ 9LI@<; K<:KFE@: JKIL:KLI< -:@<E:<
 S
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... These salt giants were usually accumulated in active tectonic environments (subduction or rift) and accompanied by some magmatic-hydrothermal events, which may occur as parts of "Wilson cycles" 5,6 . Meanwhile, the complicated hydrodynamics, thermodynamics and properties of brines and the processes of solid-liquid phase transformations in these salt giants were different from the traditional salt formation models 5,6,9,10,11 . The current upsurge in the study of evaporite dynamics, the development of new evaporite mechanisms and the ensuing controversies 5,6,8,9,10,11 have led to re-assessment of various roles in salt accumulation. ...
... Meanwhile, the complicated hydrodynamics, thermodynamics and properties of brines and the processes of solid-liquid phase transformations in these salt giants were different from the traditional salt formation models 5,6,9,10,11 . The current upsurge in the study of evaporite dynamics, the development of new evaporite mechanisms and the ensuing controversies 5,6,8,9,10,11 have led to re-assessment of various roles in salt accumulation. Therefore, a new systematic salt accumulation mechanism is eagerly needed for these large salt deposits. ...
... In spite of the intervals between the LIPs and LEPs, there might be positively promoting effect to accumulation of the LEPs from the LIPs. Recently, Hovland et al. 5,6 suggested a model of large salt accumulation based on hydrothermal processes within Wilson cycles and proposed that solid salt was easily formed in subduction and rifting tectonic environments, such as the Andean subduction zone (oceanic-continental subduction), the Mediterranean ridge subduction zone (oceanic-oceanic subduction), and the East African and Rea Sea rifts. This is consistent with our analysis of statistic data of distributions, masses, and salt-forming rates of evaporite deposits in the world. ...
Preprint
Full-text available
Large evaporite provinces (LEPs) represent prodigious volumes of evaporites widely developed from the Sinian to Neogene. The reasons why they often quickly develop on a large scale with large areas and thicknesses remain enigmatic. Possible causes range from warming from above to heating from below. The fact that the salt deposits in most salt-bearing basins occur mainly in the Sinian-Cambrian, Permian-Triassic, Jurassic-Cretaceous, and Miocene intervals favours a dominantly tectonic origin rather than a solar driving mechanism. Here, we analysed the spatio-temporal distribution of evaporites based on 138 evaporitic basins and found that throughout the Phanerozoiceon, LEPs occurred across the Earth’s surface in most salt-bearing basins, especially in areas with an evolutionary history of strong tectonic activity. The masses of evaporites, rates of evaporite formation, tectonic movements, and large igneous provinces (LIPs) synergistically developed in the Sinian-Cambrian, Permian, Jurassic-Cretaceous, and Miocene intervals, which are considered to be four of the warmest times since the Sinian. We realize that salt accumulation can proceed without solar energy and can generally be linked to geothermal changes in tectonically active zones. When climatic factors are involved, they may be manifestations of the thermal influence of the crust on the surface.
... These salt giants were usually accumulated in active tectonic environments (subduction or rift) and accompanied by some magmatic-hydrothermal events, which may occur as parts of "Wilson cycles" 5,6 . Meanwhile, the complicated hydrodynamics, thermodynamics and properties of brines and the processes of solid-liquid phase transformations in these salt giants were different from the traditional salt formation models 5,6,9,10,11 . The current upsurge in the study of evaporite dynamics, the development of new evaporite mechanisms and the ensuing controversies 5,6,8,9,10,11 have led to re-assessment of various roles in salt accumulation. ...
... Meanwhile, the complicated hydrodynamics, thermodynamics and properties of brines and the processes of solid-liquid phase transformations in these salt giants were different from the traditional salt formation models 5,6,9,10,11 . The current upsurge in the study of evaporite dynamics, the development of new evaporite mechanisms and the ensuing controversies 5,6,8,9,10,11 have led to re-assessment of various roles in salt accumulation. Therefore, a new systematic salt accumulation mechanism is eagerly needed for these large salt deposits. ...
... In spite of the intervals between the LIPs and LEPs, there might be positively promoting effect to accumulation of the LEPs from the LIPs. Recently, Hovland et al. 5,6 suggested a model of large salt accumulation based on hydrothermal processes within Wilson cycles and proposed that solid salt was easily formed in subduction and rifting tectonic environments, such as the Andean subduction zone (oceanic-continental subduction), the Mediterranean ridge subduction zone (oceanic-oceanic subduction), and the East African and Rea Sea rifts. This is consistent with our analysis of statistic data of distributions, masses, and salt-forming rates of evaporite deposits in the world. ...
Preprint
Full-text available
Large evaporite provinces (LEPs) represent prodigious volumes of evaporites widely developed from the Sinian to Neogene. The reasons why they often quickly develop on a large scale with large areas and thicknesses remain enigmatic. Possible causes range from warming from above to heating from below. The fact that the salt deposits in most salt-bearing basins occur mainly in the Sinian-Cambrian, Permian-Triassic, Jurassic-Cretaceous, and Miocene intervals favours a dominantly tectonic origin rather than a solar driving mechanism. Here, we analysed the spatio-temporal distribution of evaporites based on 138 evaporitic basins and found that throughout the Phanerozoiceon, LEPs occurred across the Earth’s surface in most salt-bearing basins, especially in areas with an evolutionary history of strong tectonic activity. The masses of evaporites, rates of evaporite formation, tectonic movements, and large igneous provinces (LIPs) synergistically developed in the Sinian-Cambrian, Permian, Jurassic-Cretaceous, and Miocene intervals, which are considered to be four of the warmest times since the Sinian. We realize that salt accumulation can proceed without solar energy and can generally be linked to geothermal changes in tectonically active zones. When climatic factors are involved, they may be manifestations of the thermal influence of the crust on the surface.
... change during the MSC and average annual conditions with a temperature of 22 °C (Δ = 15.6-24.7 °C), a relative humidity of 19% (Δ = 17.5-60%) and a rainfall of 575 mm (Δ = 355-872 mm) 19 . Similarly, fossil organic lipids suggest normal salinity (26)(27)(28)(29)(30)(31)(32)(33)(34) and temperatures ranging from 25 to 28 °C during the MSC 20 . Such climatic conditions, if they lasted for years, could be consistent with a decrease in the sea level and thus salt precipitation (if disconnected from the world ocean). ...
... Emerging theories propose deep salt formation by supercritical fluids 27 or exothermic serpentinization in mantle exhumation zones [28][29][30] . Several thermodynamic processes occur at depth and involve thermal reactions influenced by rifts and/or water consumption by precipitation of hydrated minerals 31 . ...
... When considered, talc is insignificant (<0.01% of the additional precipitation) and, unlike magnesite, does not prevent Mg-rich salt precipitation. The thermodynamic calculations indicate that the temperature decrease due to brine interactions with seawater lowers the salt solubility, which allows the deposition of soluble salt at the seafloor despite the large quantity of water available, as currently observed in pools at the bottom of the Red Sea 28,29 . In addition, cooling of the highly concentrated brine that reaches the seafloor makes it much denser than seawater. ...
Article
Full-text available
The evaporation of seawater in arid climates is currently the main accepted driving mechanism for the formation of ancient and recent salt deposits in shallow basins. However, the deposition of huge amounts of marine salts, including the formation of tens of metres of highly soluble types (tachyhydrite and bischofite) during the Aptian in the South Atlantic and during the Messinian Salinity Crisis, are inconsistent with the wet and warm palaeoclimate conditions reconstructed for these periods. Recently, a debate has been developed that opposes the classic model of evaporite deposition and argues for the generation of salt by serpentinization. The products of the latter process can be called “dehydratites”. The associated geochemical processes involve the consumption of massive amounts of pure water, leading to the production of concentrated brines. Here, we investigate thermodynamic calculations that account for high salinities and the production of soluble salts and MgCl2-rich brines through sub-seafloor serpentinization processes. Our results indicate that salt and brine formation occurs during serpentinization and that the brine composition and salt assemblages are dependent on the temperature and CO2 partial pressure. Our findings help explain the presence and sustainability of highly soluble salts that appear inconsistent with reconstructed climatic conditions and demonstrate that the presence of highly soluble salts probably has implications for global tectonics and palaeoclimate reconstructions.
... 62 2. Observations not explained by the current evaporite theory 63 To illustrate that there might be a need for additional perspectives on the formation 64 processes for giant salt accumulations; some pertinent observations from major salt 65 accumulations are presented below. The first examples are related to the Messinian salts 66 of the Mediterranean, as these are probably the best studied salt deposits in the world and 67 in essence form the basis for the present conventional evaporite model (Hsü et al., 1973). 68 69 Roveri et al. (2014) present a state-of-the-art example from this scientific theme. ...
Technical Report
Full-text available
The main objective of this communication is to describe the magmatic 'Global Salt Cycle', 8 an important addition to solar evaporative processes in the formation of salt giants. The Global Salt 9 Cycle (GSC) provides an alternative explanation for the observed volumes and composition of salts, 10 at the location where they are observed. The first stage in the GSC is saturation of oceanic crust and 11 sediments with seawater. Subduction of oceanic crust and serpentinized lithosphere transports 12 water, hydrated minerals, and marine salts deep into the crust and mantle. Upon pressurization and 13 heating of the subducting slab, different parts of this water are expelled at different 14 depths/temperatures. The resulting fluids will contain salts brought in with the slab, as well as 15 minerals and new salts formed by water-rock interaction. The main transport mechanisms bringing 16 mantle fluids closer to the surface, is upwelling of the mantle itself, followed by fluid exsolution. 17 Any tectonic processes that involve upwelling of fluid-invaded mantle or escape of fluids from it, 18 i.e., subduction processes, rifting of continental crust, back arc rifting above active subduction zones, 19 mantle upwelling and lithospheric extension above retreating subduction zones, and mantle 20 upwelling creating intracratonic basins, may potentially lead to deposition of solid salt. The global 21 extent of the processes involved in salt formation included in the GSC concept, is substantiated with 22 information and data included in four appendices (Additional Material). 23
... For the particular Cretaceous mantle exhumation stage, new concepts have proposed brine formation by interactions between mantle rock and seawater. Hovland et al. (2018) reviewed the different hydrothermal processes which should produce salt and brines through hydrated mineral formation, a mechanism already proposed by several studies (Gleeson et al. 2003;Stober and Bucher 2004;Richard et al. 2013;Bons et al. 2014;Walter et al. 2016;Martz et al. 2019). Scribano et al. (2017) have suggested that the formation of giant salt deposits should be genetically related to the serpentinization of ultramafic rocks. ...
Article
Triassic evaporites have a very particular location in the Pyrenees, close to detachment areas between the basement and the sedimentary cover, and constitute enormous chlorine and potentially brine reservoir. During the two successive deformation cycles related successively to the Cretaceous rifting and the convergence during early Cenozoic, brines were expulsed and implied in fault activity, breccia formation and fluid-rock interactions. Fluid inclusions from fault infillings and alpine-style fissures sampled all along the Pyrenean chain have a maximal chlorinity close to that of halite-water equilibrium at temperatures between 250 and 350°C. Mixing of brines with low chlorinity waters formed a series of fluids covering an extensive range of salinities. During syn-rift events, the hotter dilute end-member is likely derived from seawater infiltrated and heated near the exhumed mantle as no emerged areas were present at that time. During convergence and thrusting, brines again predominate and mixing occurred with a colder end-member, probably of meteoric origin, consistent with a significant period of relief formation. Brines played, therefore, an essential role in mass and heat transfer during the whole orogenic cycle in the Pyrenees.
... The deeps (the black dots in Figure 1) along the Red Sea form volcanic areas floored by MORB basalts as Haase et al. (2000) and Ligi et al. (2012) demonstrate in the Shaban, Thetis, and Nereus deeps. The deeps are associated with topographic lows, an extensive regime, and they are believed to be associated with mantle upwelling and, in the case of the Mabahiss deep, a graben structure (Hovland et al., 2018). Deeps can be considered as the nucleus for rift segments initiation and the precursor of a regular magmatic oceanic crust spreading center (Cochran et al., 1991;Haase et al., 2000;Ligi et al., 2012). ...
Article
Full-text available
Rifts and rifted passive margins are often associated with thick evaporite layers which challenge seismic reflection imaging in the sub-salt domain. This makes understanding the basin evolution and crustal architecture difficult. An integrative, multidisciplinary workflow has been developed using the exploration well, gravity and magnetics data together with seismic reflection and refraction datasets in order to build a comprehensive 3D subsurface model of the Egyptian Red Sea.Using a 2D iterative workflow first, we constructed cross-sections using the available well penetrations and seismic refraction data as preliminary constraints. The 2D forward model uses regional gravity and magnetic data to investigate the regional crustal structure. The final models are refined using enhanced gravity and magnetic data and geological interpretations. This process reduces uncertainties in basement interpretation and magmatic body identification. Euler depth estimates are used to point out the edges of high susceptibility bodies. We achieved further refinement by initiating a 3D gravity inversion. The resultant 3D gravity model increases precision in crustal geometries and lateral density variations within the crust and the pre-salt sediments. Along the Egyptian margin, where data inputs are more robust, basement lows are observed and interpreted as basins. Basement lows correspond with thin crust (lt;12 km), indicating that the evolution of these basins is closely related to the thinning or necking process. In fact, the Egyptian Northern Red Sea is typified by dramatic crustal thinning or necking that is occurring over very short distances ~30 km, and very proximal to the present day coastline. The integrated 2D and 3D modelling reveals the presence of high density, magnetic bodies which are located along the margin. The location of the present day Zabargad Transform fault zone (ZTFZ) is very well delineated in the computed crustal thickness maps, suggesting it is associated with thin crust, and shallow mantle.
... Recent studies have suggested that serpentinization in closed systems provides a mechanism to concentrate salts and generate NaCl-MgCl 2 -rich brines that can lead to the formation of seemingly inexplicable occurrences of salt in deep-water rift basins that were never desiccated (e.g. Red Sea and the Mediterranean Sea) (Scribano et al., 2017;Hovland et al., 2018bHovland et al., , 2018aHovland et al., , 2019Manuella et al., 2018;Scribano et al., 2018;Aftabi and Atapour, 2018;Debure et al., 2019). However, such high salinity brines are yet to be seen in active hydrothermal systems hosted by abyssal peridotites. ...
Article
Serpentinization, i.e. the hydrothermal alteration of ultramafic rocks, is an important and ubiquitous geologic process that occurs at slow- and ultraslow-spreading mid-ocean ridges, magma-poor passive margins, and subduction zones. While serpentinization occurs over a wide temperature range and involves diverse fluid compositions, few experimental studies systematically examined the effects of temperature and fluid composition on the kinetics of serpentinization of olivine, and published rates diverge greatly. We present results of an experimental study using synthetic fluid inclusions in Mg-rich olivine as micro batch reactors to monitor the effects of temperature (100 ° to 350 °C), fluid composition (H2O-MgCl-NaCl, H2O-NaCl, H2O-MgCl), and total salinity on serpentinization rates of olivine under closed system conditions. Petrographic observations and Raman analyses of the experimental run products revealed the alteration of olivine to produce serpentine minerals, brucite, and magnetite. The salinity of the aqueous fluid in the inclusions increased as H2O was removed from the solution and incorporated into the hydrous product phases and served as a proxy for reaction progress. The fastest serpentinization rates were found at 250 °C in the presence of a seawater-like aqueous solution. This result further suggests that serpentinization of olivine is fastest at lower temperatures (∼250 °C) and shallower depths in the oceanic lithosphere than suggested by previous studies (∼300 °C). Moreover, our experiments show that serpentinization rates decrease by several orders of magnitude as salinity and the concentration of dissolved Mg increase. These effects may reconcile some of the differences observed when comparing results of previously published rates obtained from experiments involving fluids of different compositions. We constructed a quantitative model based on the principle of detailed balance to predict variations in serpentinization rates (J±) from low temperatures to 320 °C. It suggests that at 25 °C, serpentinization rates are 4 to 5 orders of magnitude slower than at 250 °C. Moreover, the temperature dependence model has been coupled with the kinetic effects derived from experiments involving different fluid composition to calculate the amount of time required for serpentinization of olivine having different reactive surface areas. The model shows that between 200 and 300 °C serpentinization is fast on geologic timescales when rocks with large reactive surface areas interact with a seawater-like aqueous solution (complete serpentinization in days to decades).
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The main objective of this communication is to describe the ‘Global Salt Cycle’. Giant salt accumulations are commonly found along continental margins of former rifts. The first stage in the accumulation process is saturation of newly formed oceanic crust with seawater. Final mobilisation and accumulation of the salts occurs during rifting, localised in the vicinity of relict subduction zones. Oceanic crust is created along the spreading ridges in the deep oceans of the Earth. It exchanges mass and energy with seawater in hydrothermal circulation cells that penetrate deep into the new and fractured crust. Water-rock interactions include the formation of hydrated and hydroxylated minerals, e.g., serpentinites and clay minerals. By incorporating hydroxyl groups and water in their crystal lattices, the salinity of remaining brines increases. Subduction of oceanic crust and serpentinised lithosphere transports water, hydrated minerals, and marine salts deep into the crust and mantle. Upon pressurisation and heating of the subducting slab, different parts of this water are expelled at different depths/temperatures. The resulting fluids will contain salts brought in with the slab, as well as new salts formed by water-rock interaction. The combination of elevated pressures and temperatures, water, salinity, and CO2, create permeability in the normally impermeable, peridotitic mantle, by altering the fluid-rock dihedral angles of mineral grains. This P/T-determined intergranular permeability allows ascent of saline fluids, under lithostatic pressure, within the mantle wedge, or the slab itself. The fluids produce a mechanically weakened and buoyant zone within the mantle wedge due to high pore pressure between mineral grains and reduced mantle density. During the lifetime of a subduction zone, a substantial accumulation of saline fluids within the mantle wedge and crust, is evident. Deep, fluid reservoirs accumulate between the subduction trench and the volcanic front. They may exist for hundreds of millions of years, even after the extinction of the subduction zone. Saline fluids may escape to the surface along deep faults, due to overfilling of available pores/fractures. Fluids within the mantle wedge may form rock melts or exist as supercritical, mineral rich fluids. The combination of reduced pressure due to rifting, and a saline and buoyant mantle, creates a mantle circulation that brings the accumulated, saline fluids, to crustal levels. Salts will therefore accumulate during initial stages of rifting as a result of massive fluid expulsion, phase change and boiling of mantle fluids. No extra energy is required to produce phase change and boiling. The result is formation of solid salts or dense brines/slurries invading fractured crustal rocks, or escaping to the surface/seabed. This process may take place both before and after the sea has invaded a continental rift.
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The E-W oriented Sivas foreland basin in Turkey recorded a salinity crisis during the Late Eocene resulting in evaporite accumulations thick enough to trigger intense halokinesis during the Oligo-Miocene. The salinity crisis is studied thanks to three sedimentological sections crossing the transition from the last marine deposits (Bözbel Formation) to the overlying evaporitic facies (Tuzhisar Formation) preserved from halokinetic deformations. The top of the Bözbel Formation presents flood-generated hyperpycnites developed in pro-delta to delta front settings. In the central part of the basin, such facies become increasingly sediment-starved with azoic calcareous facies interlayered with organic-rich shales. Such facies are ultimately capped by thick accumulations of gypsiferous turbiditic lobe deposits. Southward, the foredeep was partly isolated from the central domain due to the propagation of an anticline. There, the basal siliciclastic turbidites become increasingly gypsum-rich and are capped by a 45 meters-thick mass-transport deposit enclosing olistoliths of gypsum and of ophiolitic rocks. Such gravity collapse deposits evolve upward to the same gypsiferous turbiditic lobes observed northward. Both transitional facies record the progressive confinement of the basin from the sea, likely due to the northward propagation of the fold-and-thrust belt located farther south. The evaporites started to precipitate in piggy-back evaporitic basins, along the highs of the fold-and-thrust belt, before being reworked gravitationally in the foredeep to the north, producing the high to low density gypsum turbidites. Finally, from north to south, the reworked evaporites are extensively covered by a > 100 m thick, chaotic, coarse-crystalline gypsum mass likely resulting from the hydration of anhydrite grains left as a residual phase after the leaching of a significant amount of halite. The latter formed in a hypersaline marine-fed basin and have lately allowed mini-basin salt tectonics during Oligo-Miocene times.
Article
Global climate evolution models for habitable earthlike planets do not consider the effect of ocean salinity on land ice formation through the hydrological cycle. We consider two categories of such planets: planets with deep oceans, but intrinsically high salinities due to the weaker salt removal process by hydrothermal vents; and planets with shallow oceans, where the increase in salt content and decrease in ocean area during the onset of glaciation cause a negative feedback, helping delay the spread of land ice. We developed a toy climate model of a habitable planet on the verge of an ice age, using a range of initial salt concentrations. Planets with deep oceans and high salinity show considerable increase in the time necessary to fill arctic land with ice sheets, up to 23 per cent considering the maximum salinity range. For planets with shallow oceans, the effect of intrinsic high salinity is reinforced by the negative feedback, counteracting positive feedbacks like the ice-albedo and Croll-Milankovitch perturbations, to the point of effectively terminating land ice sheet growth rate during the simulated timescale. We also apply this model to the putative ocean of early Mars, finding intermediate results: salinity probably did not play a role in the evolution of Mars´ climate, considering the timescale of its ice ages. We conclude that this phenomenon is essentially an abiotic self-regulation mechanism against ice ages and should be regarded in the context of habitable planets smaller and drier than the Earth, which may well represent the bulk of habitable planets.
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The formation of large salt deposits is observed especially in areas with a geological history of high tectonic activity. Over the last decade it has become a well-established fact that heavy brines form and solid salts precipitate, due to the thermodynamic and physico-chemical properties of seawater at high temperatures and pressures encountered within hydrothermal systems. This article reviews the modern theoretical and experimental research behind these findings, and also describes geological settings that most likely cause brine- and salt-forming hydrothermal processes to occur. This analysis has led to the identification of a set of specific conditions, properties, and processes (referred to as Conceptual elements) that are used to explain the often complex processes of brine behavior that leads to hydrothermal formation of solid salt.The main objective of this review is to present hydrothermal conditions known to occur during Wilson cycles: subduction, collision, and rifting, e.g., zones of repeated tectonic unrest, where brines (commonly derived from seawater) are concentrated into heavy brines and precipitate solid salts. The internal heat of the Earth and its interaction with deeply-circulating seawater in hydrothermal systems and also the immense recycling of crustal materials, including porous oceanic crust and serpentinite (hydrated) rocks via mantle processes may lead to the formation of salt accumulations. It is also acknowledged that such brines and solid salts may often be stored sub-surface for long time periods, extending from one Wilson cycle to another. Thus, on the basis of this analysis, it is cautiously suggested that large amounts of salts 'hidden' inside subduction zones may appear on the surface during subsequent rifting and oceanization phases.In Part 2 of this review, the Conceptual elements, which are described and discussed herein (Part 1) are applied to selected cases, including the Andean Mountains, the East African Rift, the Red Sea Rift, and other locations.
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The omnipresence of lithium-ion batteries in mobile electronics, and hybrid and electric vehicles necessitates discovery of new lithium resources to meet rising demand and to diversify the global lithium supply chain. Here we demonstrate that lake sediments preserved within intracontinental rhyolitic calderas formed on eruption and weathering of lithium-enriched magmas have the potential to host large lithium clay deposits. We compare lithium concentrations of magmas formed in a variety of tectonic settings using in situ trace-element measurements of quartz-hosted melt inclusions to demonstrate that moderate to extreme lithium enrichment occurs in magmas that incorporate felsic continental crust. Cenozoic calderas in western North America and in other intracontinental settings that generated such magmas are promising new targets for lithium exploration because lithium leached from the eruptive products by meteoric and hydrothermal fluids becomes concentrated in clays within caldera lake sediments to potentially economically extractable levels.
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Worldwide marine salt deposits ranging over the entire geological record are generally considered climate-related evaporites, derived from the precipitation of salts (mainly chlorides and sulfates) from saturated solutions driven by solar evaporation of seawater. This explanation may be realistic for a salt thickness ≤ 100 m, being therefore inadequate for thicker (> 1 km) deposits. Moreover, sub-seafloor salt deposits in deep marine basins are difficult to reconcile with a surface evaporation model. Marine geology reports on abyssal serpentinite systems provide an alternative explanation for some salt deposits. Seawater-driven serpentinization consumes water and increases the salinity of the associated aqueous brines. Brines can be trapped in fractures and cavities in serpentinites and the surrounding ‘country’ rocks. Successive thermal dehydration of buried serpentinites can mobilize and accumulate the brines, forming highly saline hydrothermal solutions. These can migrate upwards and erupt onto the seafloor as saline geysers, which may form salt-saturated water pools, as are currently observed in numerous deeps in the Red Sea and elsewhere. The drainage of deep-seated saline brines to seafloor may be a long-lasting, effective process, mainly occurring in areas characterized by strong tectonic stresses and/or igneous intrusions. Alternatively, brines could be slowly expelled from fractured serpentinites by buoyancy gradients, and hence separated salts/brines could intrude vertically into surrounding rocks, forming salt diapirs. Serpentinizzation is an ubiquitous, long-lasting process throughout geological times with no demand for an external energy source. It is therefore reasonable to recognize the existence of buried, serpentinite-related salt deposits in many areas of the world.
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One Sentence Summary: Geophysical, laboratory conductivity and petrological experiments reveal that deep electrical conductivity anomalies beneath the Central Andes, Cascades and Taupo Volcanic Zone image the ponding of super-hydrous andesitic melts which contributes to the growth of continental crust. The formation of the continental crust at subduction zones involves the differentiation of hydrous mantle- derived magmas through a combination of crystallization and crustal melting. However, understanding the mechanisms by which differentiation occurs at depth is hampered by the inaccessibility of the deep crust in active continental arcs. Here we report new high-pressure electrical conductivity and petrological experiments on hydrated andesitic melt from Uturuncu volcano on the Bolivian Altiplano. By applying our results to regional magnetotelluric data, we show that giant conductive anomalies at mid- crustal levels in several arcs are characterized by relatively low amounts of intergranular andesitic partial melts with unusually high dissolved water contents (≥8 wt.% H2O). Below Uturuncu, the Altiplano- Puna Magma Body (APMB) displays an electrical conductivity that requires high water content (up to 10 wt.%) dissolved in the melt based on crystal-liquid equilibria and melt H2O solubility experiments. Such a super-hydrous andesitic melt must constitute about 10% of the APMB, the remaining 90% being a combination of magmatic cumulates and older crustal rocks. The crustal ponding level of these andesites at around 6 kbar pressure implies that on ascent through the crust hydrous magmas reach their water saturation pressure in the mid-crust, resulting in decompression-induced crystallization that increases magma viscosity and in turn leads to preferential stalling and differentiation. Similar high conductivity features are observed beneath the Cascades volcanic arc and Taupo Volcanic Zone. This suggests that large amounts of water in super-hydrous andesitic magmas could be a common feature of active continental arcs and may illustrate a key step in the structure and growth of the continental crust.
Article
The Messinian salinity crisis (MSC) is perceived as an environmental crisis governed by climatic and tectonic controls, affecting global oceans’ salinity and shaping the Mediterranean Sea’s biochemical composition. Recently drilled offshore wells in the Levant Basin retrieved a sedimentary record of the deep-basin Mediterranean MSC salt deposits and the underlying pre-evaporite unit. In this study, we have concentrated on the pre-evaporite interval and its transition into the overlying evaporites. Analysis of this data set changes the way these deposits have been perceived since the 1970s, when they were first penetrated in their uppermost part during Deep Sea Drilling Project expeditions. Using sedimentology, seismic interpretation, biostratigraphy, and astronomical tuning, we show that Messinian salt deposition in the Eastern Mediterranean began during stage 1 of the MSC. In contrast to the present paradigm, salt was deposited synchronously with gypsum in the marginal and intermediate-depth basins significantly before the 50 k.y. interval coined as the “MSC acme event”, ~400 k.y. after the crisis began. Thus salt precipitation took place in a non-desiccated deep basin, having a restricted but often open connection with the Atlantic Ocean, substantially altering our understanding of the mechanisms governing the deposition of salt giants. A coeval onset of basinal halite and marginal gypsum precipitation calls for a revaluation of global-scale climatic and oceanographic models of the MSC, taking into account a much older age for the beginning of halite deposition.
Article
The Red Sea is an unusual example of a rift basin that transitioned from its evaporitic stage to fully open-ocean conditions at the end of the Miocene (∼5.3 Ma), much more recently than older Mesozoic margins around the Atlantic and Gulf of Mexico. The patterns of halokinetic deformation occurring in the Red Sea are potentially of interest for understanding more generally how evaporite deposits deform during this early stage. Relevant to this issue, a line of reconnaissance sidescan sonar data (GLORIA) collected along the Red Sea in 1979 is re-evaluated here. We first interpret the data with the aid of newly compiled bathymetry from multibeam sonars in the central and southern Red Sea. Features in the acoustic backscatter data are associated with ridges, valleys and rounded flow fronts produced by halokinetic deformation. Some areas of higher acoustic backscattering from the evaporites are suggested to relate to roughness produced by deformation of the evaporite surface. Within the volcanic (oceanic) axial valleys, areas of differing high and low backscattering suggest varied sediment cover and/or carbonate encrustations. With the benefit of the above experience, we then interpreted data from the northern Red Sea, where there are fewer multibeam data available. Rounded fronts of halokinetic deformation are present in the Zabargad Fracture Zone, a broad, shallow valley crossing the Red Sea obliquely. The presence of halokinetic deformation here is evidence that subsidence has occurred along the fracture zone. Elsewhere in the northern Red Sea, the GLORIA data reveal folds in the evaporite surface, suggesting local areas of convergence, like those implied by multibeam data from inter-trough zones further south. Some linear features are observed, many of which are likely to be ridges overlying salt walls. Interestingly, several such features are oriented along an accommodation zone that is oriented parallel to the plate spreading direction. Several rounded, corrugated features are interpreted as possible evaporite flow fronts. Overall, the impression from the data is of a strongly mobile seabed in the Red Sea because of halokinetic deformation, involving both vertical and horizontal movements. However, salt walls appear more common than in the central and southern axial Red Sea, where horizontal movements instead tend to dominate.
Book
Foreword by Peter A. Cawood Acknowledgements. 1. Water and hydrothermal fluids on Earth 2. Hydrothermal processes and wall rock alteration 3. Tectonic settings, geodynamics and temporal evolution of hydrothermal mineral systems 4. Intrusion-related hydrothermal mineral systems 5. Porphyry systems fossil and active epithermal systems 6. Skarn systems 7. Submarine hydrothermal mineral systems 8. Metalliferous sediments and sedimentary rock-hosted stratiform and/or stratabound hydrothermal mineral systems 9. Orogenic, amagmatic and hydrothermal mineral systems of uncertain origin 10. Hydrothermal systems and the biosphere 11. Hydrothermal processes associated with meteorite impacts 12. Hydrothermal processes and systems on other planets and satellites 13. Uranium hydrothermal mineral systems References. Index
Article
The central Andean region contains one of the world's largest and most unusual accumulations of Upper Tertiary and Quaternary continental saline deposits of five principal types: 1) Nitrate deposits, which occur widely in the coastal Atacama Desert of northern Chile, are saline caliches. 2) Salars, which for the most part are desiccation remnants of former saline lakes. 3) Salar Grande, which also is the site of a former saline lake, is a unique body of high-purity coarsely crystalline rock salt. 4) Deformation continental saline deposits of Late Tertiary age include the folded rock-salt deposits in the Salar de Atacama basin, northern Chile, and the folded and faulted borax deposits at Tincalayu, northwestern Argentina. 5) Borate-spring deposits, both active and fossil, of which there are several in northwestern Argentina and one in southern Peru. -from Author
Chapter
Nowhere on the present-day Earth can the transition from a continental to an oceanic rift be observed and studied better than in the Red Sea region, where three rifts in different stages of evolution meet in a triple point located in the Afar region. A thermal and/or compositional mantle plume may have risen from the upper mantle below Afar already at ~30 Ma, and may have triggered, at least in part, the rifting process. The axial area of the rifts is marked by intense seismicity. While the East African is a fully continental rift, the Gulf of Aden rift experienced oceanic crust accretion between Arabia and Somalia starting already at 17 Ma with a progressive westward propagation that impacted against Africa in the Afar Triangle starting at <1 Ma. The axial zone of oceanic crustal accretion in the Gulf of Aden is segmented by several small (<30 km) offsets, including two major transform-fracture zones, the Socotra (offset ~50 km) and the Alula-Fartak (offset 180 km). Spreading is asymmetric, faster in the northern (Arabia) side (11–13 mm/a) than in the southern (Somalia) side (8 mm/a). The Afar Triangle is a topographically depressed region, located between the continental blocks of Nubia, Somalia, and the Danakil Alps, that separate it from the southern Red Sea. It is an area of thin crust, seismicity related to extension, and intense intrusive and extrusive, mostly basaltic, magmatism. Intrusive basaltic magmatism appears to be important in triggering the rifting process in Afar. Northern Afar displays basaltic ranges oriented parallel to the axis of the Red Sea, such as the Erta Ale, with a crestal permanent lava lake. These ranges represent an incipient oceanic accretionary plate boundary separating Africa from Arabia. At the northern tip of Afar, the plate boundary is displaced to the axial zone of the southern Red Sea, an elongated basin oriented ~N30°W. Its southern part is characterized by an axial rift valley floored by oceanic basalt and accompanied by parallel Vine-Matthews magnetic anomalies, suggesting initial oceanic crust accretion at ~5 Ma, although alternative interpretations suggest that the entire width of the southern Red Sea is underlain by oceanic crust. Moving still farther north, the axial valley becomes discontinuous and the initial accretion of oceanic crust appears to take place in discrete cells that become younger northward. Propagation from these initial nuclei will result in a continuous axial zone of oceanic accretion. Some of these axial “deeps” are the locus of intense hydrothermal activity and metallogenesis. Moving north, the oceanic rift impacts against the Zabargad fracture zone, a major topographic-structural feature that crosses the Red Sea in a NNE direction, offsetting its axis by nearly 100 km. Zabargad island, located at the SSW end of the fracture zone, exposes a sliver of sub-Red Sea lithosphere, including mantle peridotite bodies, Pan-African granitic gneisses criss-crossed by basaltic dykes, gabbro intrusions, and a sedimentary sequence starting with pre-rift Cretaceous deposits. North of the Zabargad Fracture zone, the Red Sea lacks an axial rift valley; it probably consists of extended thinned and faulted continental crust injected by gabbros and basaltic dykes. The activation of the NNE-trending Aqaba-Dead Sea fault at about 14 Ma has deactivated rifting in the Gulf of Suez. Basalt chemistry suggests that the degree of melting of the Red Sea subaxial mantle decreases from south to north, in parallel with a decreasing spreading rate and a lesser influence of the Afar plume.