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Epigenetic Graphitization in the Basement of the Siberian Craton as Evidence of the Migration of Hydrocarbon-enriched Fluids in the Paleoproterozoic (English version)

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This paper reports on diagnostic and structural studies that were first carried out for carbonaceous material of quartz–muscovite dynamoschists from the schistosity zone in biotite migmatites, pegmatites, and diabases of the southern part of the Baikal ledge of the Siberian craton. The carbonaceous material is represented by phanerocrystalline and microcrystalline graphite with residual hydrocarbon radicals. Native Ni, Sn, zincous Cu, Fe–Ni compounds, sulfides of Cu, rutile, monazite, and zircon were revealed in the intergrowths with carbonaceous material. The carbon isotopic composition ranges from –29.19‰ to –31.58‰, except for carbonaceous material from the schistocity diabase, where δ¹³C = –24.93‰. ⁴⁰Ar–³⁹Ar dating of muscovite gave an age of 1947 ± 7.8 Ma pointing to the relation between dynamic metamorphism with accretion of the Akitkan fold system and the ancient complexes of the craton. It was concluded that the deposition of native carbon and metals was caused by migration of essentially hydrocarbonate fluid in the formations of the upper crust (Fig. 4, Table 1).
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ISSN 1028-334X, Doklady Earth Sciences, 2019, Vol. 486, Part 1, pp. 498–502. © Pleiades Publishing, Ltd., 2019.
Russian Text © The Author(s), 2019, published in Doklady Akademii Nauk, 2019, Vol. 486, No. 2.
Epigenetic Graphitization in the Basement of the Siberian Craton
as Evidence of the Migration of Hydrocarbon-enriched Fluids
in the Paleoproterozoic
V. B. Savelyevaa,*, Yu. V. Danilovaa, T. G. Shumilovab, A. V. Ivanova,
B. S. Danilova, and E. P. Bazarovaa
Presented by Academician F.A. Letnikov March 15, 2017
Received March 29, 2017
AbstractThis paper reports on diagnostic and structural studies that were first carried out for carbonaceous
material of quartz–muscovite dynamoschists from the schistosity zone in biotite migmatites, pegmatites, and
diabases of the southern part of the Baikal ledge of the Siberian craton. The carbonaceous material is repre-
sented by phanerocrystalline and microcrystalline graphite with residual hydrocarbon radicals. Native Ni,
Sn, zincous Cu, Fe–Ni compounds, sulfides of Cu, rutile, monazite, and zircon were revealed in the inter-
growths with carbonaceous material. The carbon isotopic composition ranges from –29.19‰ to –31.58‰,
except for carbonaceous material from the schistocity diabase, where δ13C = –24.93‰. 40Ar–39Ar dating of
muscovite gave an age of 1947 ± 7.8 Ma pointing to the relation between dynamic metamorphism with accre-
tion of the Akitkan fold system and the ancient complexes of the craton. It was concluded that the deposition
of native carbon and metals was caused by migration of essentially hydrocarbonate fluid in the formations of
the upper crust (Fig. 4, Table 1).
DOI: 10.1134/S1028334X19050155
In the folded margins of the southern part of the
Siberian craton and granitoids of the basement, occur-
rences of carbonatization are often encountered in the
form of native carbon and bituminoids within the oil-
and gas-bearing areas. The carbonatization is consid-
ered as a result of the impact of high-carbon deoxi-
dized fluids [2, 3, 5, 13]. The isotopic composition of
carbon in graphite from thenear-fault tectonites and
metasomatites is mostly enriched in 13 C coinciding
with the endogenic origin. However, the sources of
carbon and the relationship between carbonization
and geodynamic processes are controversial issues in
many respects. We have studied, for the first time, epi-
genetic carbonatization with an unusual (enriched by
13C) isotopic composition of carbon in the schistosity
zones of the southern part of the Baikal basement
ledge of the Siberian craton (Western Baikal area).
The formations of the Baikal ledge in the Siberian
craton structure are involved in the Akitkan fold belt,
which is considered as a Late Paleoproterozoic inde-
pendent island arc system, which were thrust onto the
ancient basement during the amalgamation of terrains
1.91–2.00 Ga ago (Fig. 1) [11, 14]. The Baikal terrain
is composed of Paleoproterozoic metamorphosed vol-
canic–sedimentary formations and Neoarchean
(2.88 Ga [14]) and Paleoproterozoic (2.02–2.07 Ga
[9]) granitoids, which were recrystallized in the colli-
sion of the Siberian and North American paleoconti-
nents at the end of the Paleoproterozoic [4]. The rocks
of the terrain basement are overlapped by nonmeta-
morphosed volcanic–sedimentary formations of the
Akitkan series and intruded by post-collision granit-
oids dated at 1.85–1.88 Ga [14].
The formations of the Ilikta suite of the Sarma
series (PR1) occur on most of the Baikal ledge studied
(Fig. 1b). These formations are represented by metaef-
fusives of basic and intermediate composition, phyl-
lites, and chlorite–quartz, sericite–chlorite–quartz,
and quartz–sericite schists containing carbonaceous
material (CM), as well as limestones, sandstones, and
tuff sandstones. The block of the underlying Khulurtui
suite, 60 km2 in area, is distinguished among these for-
mations. The suite is composed of biotite, horn-
GEOLOGY
aInstitute of the Earth’s Crust, Siberian Branch,
Russian Academy of Sciences, Irkutsk, 664033 Russia
bYushkin Institute of Geology, Komi Science Center, Ural Branch,
Russian Academy of Sciences, Syktyvkar, 167982 Russia
*e-mail: vsavel@crust.irk.ru
DOKLADY EARTH SCIENCES Vol. 486 Part 1 2019
EPIGENETIC GRAPHITIZATION IN THE BASEMENT 499
blende–biotite, and hornblende gneisses and migma-
tites, amphibolites, quartzites, and carbonate rocks
metamorphosed at 660–700°C and 3 kbar. The rocks
of both suites are intruded by synmetamorphic plagi-
ogranites, granites, and pegmatites of the Kocherikova
complex (PR1), post-orogenic granites of the Primor-
skii complex, carbonatite dikes of about 1 Ga in age,
and diabase dikes (Fig. 1b).
Within many areas of the Khulturui block, the met-
amorphic rocks and granitoids intruding them bear
signs of deformations that were accompanied by the
replacement process, when biotite was replaced by
muscovite and chlorite, hornblende by actinolite, and
plagioclase by sericite. Fine-flake graphite and tour-
maline (dravite) are often encountered in intergrowths
with newly formed muscovite. On the coastal cliffs of
Lake Baikal (Fig. 1b), steep dipping schistosity zones
up to 6 m thick are observed in cataclased muscovi-
tized migmatites and chloritized diabase. These zones
are composed of quartz–muscovite–carbonaceous
Fig. 1. (a) Tectonic zonation of the Siberian craton [11] and (b) scheme of the geological structure of the study area (according
to the geological survey). (1) Cenozoic deposits; (2) carbonate–terrigenous deposits of the Baikal series R; (3) terrigenous and
volcanic formations of the Akitkan series PR1; (4, 5) Sarma series PR1: 4, Ilikta suite: chlorite–sericite schists, sandstones, tuff
sandstones, effusives of basis and intermediate composition; 5, Khulurtui suite: gneisses, migmatites, quartzites, amphibolites,
carbonate rocks; (6) synmetamorphic granites of the Kocherikova complex PR1; (7) post-orogenic granites of the Primorskii
complex PR1; (8) faults: a, established; b, assumed; c, overlain by Lake Baikal waters; (9) occurrences of carbonization; (10) sam-
pling points for isotopic geochemical studies; (11) the area of work on the tectonic scheme. In Fig. 1b, no dikes of diabases and
carbonatites are shown for simplicity.
84°96°
96°
108°
108°
107°45°
53°40°
53°40°
107°45°
107°30°
107°30°
012345
km
N
E
Anabar
province
Tunguska
province
Aldan
province
Stanovaya province
Akitkan belt
Akitkan belt
Akitkan belt
Angara belt
Angara belt
Angara belt
120 °
120 °
132 °
132 °
144 °
Olenek
Olenek
province
province
Olenek
province
156 °
68°
68°
60°
52°
16/14
12/13
19/13
32/14
29/14
69/15
68/15
64/15
78/15_1
9/13
9/13
52°
60°
1
4
7
10
2
5
8
3
6
7
11
N
E
0 1000
km
Irkutsk
a
bc
Baikal ledge
Lake Baikal
(a)
(b)
500
DOKLADY EARTH SCIENCES Vol. 486 Part 1 2019
SAVELYEVA et al.
dynamoschists with admixtures of chlorite, albite, and
accessory tourmaline. Outcrops of carbonatized dyna-
moschists are also encountered in other areas within
the Khulturui block, where they are attributed to the
submeridional and northeast-striking zones (Fig. 1b).
The study of carboniferous material and mineral com-
position and the measurements of the isotopic compo-
sition of carbon were carried out at the Geoscience
Center for Collective Use, Yushkin Institute of Geol-
ogy, Komi Science Center, Ural Branch, Russian
Academy of Sciences (Syktyvkar) with the use of a
TESCAN VEGA3 scanning electron microscope
(Czech Republic) with an energy-dispersive attach-
ment of an Oxford Instrument X-Max, an HR800
Raman high-definition spectrometer, Horiba Jobin
Yvon (France), a Tesla BS-500 electron microscope
(Czechoslovakia), and an XRD-6000 X-ray diffrac-
tometer, Shimadzu (Japan). The isotopic composition
of carbon was studied in the regime of a continuous
helium flow (CF-IRMS) on the analytical complex,
which includes a Flash EA 1112 element analyzer,
which is connected with thte Delta V Advantage mass
spectrometer (Germany) through the Conflo-IV gas
commutator.
The study of the chemical composition of the rocks
and 40Ar–39Ar dating of muscovite were performed in
the Geodynamic and Geochronology Center for Col-
lective Use, Institute of the Earth’s Crust, Siberian
Branch, Russian Academy of Sciences, Irkutsk. The
ARGUS VI complex, which included a mass spec-
trometer of the same name, a gas purification system,
and a high-vacuum oven, was used for 40Ar–39Ar dat-
ing. Argon was released from muscovite in heating by
steps from 470°C to full melting at 1100°C. The ages
were calculated in relation to the BERN4M standard
with the assigned age of 18.885 ± 0.097 Ma, which
allows us to correlate the U–Pb and 40Ar–39Ar dates
[15]. The carbon content Cel (noncarbonate) was
determined by the weight method.
The schistosity of migmatites was accompanied by
the removal of Ca, Na, Mg, Fe (the last one was rede-
posited in the form of oxides), Sr, Co, Ni, and Zn and
an increase in the content of K, Si, Al, Ba, Rb, Y, and
Nb. The carbon content (Cel) in dynamoschists
amounts to 16 wt % significantly exceeding that in the
rocks of the Ilikta suite (less than 3 wt %).
In dynamoschists, CM is distributed along schisto-
sity or evenly scattered, being in a dispersive state.
However, graphite particles 70 μm in size were regis-
tered. A planar structure of the particles and the unit
cell parameters are typical for high-ordered hexagonal
graphite: d002 = 0.336 nm, d004 = 0.168 nm, d006 =
0.112 nm. Spectra that are typical for phanerocrystal-
line and microcrystalline graphite with residual hydro-
carbon radicals were obtained by Raman spectroscopy
(Figs. 2a, 2b). Native metals and their clusters 10–
50 μm in size were revealed in the intergrowths with
CM: Ni with an admixture of Fe (Ni0.88–0.94Fe0.06–0.12),
Sn, zincous Cu (Cu0.88Zn0.11Fe0.01), Fe0.43–0.60Ni0.40–0.57
intermetallic compounds (Fig. 3), and sulfides of Cu,
rutile, monazite, and zircon.
The isotopic composition of carbon from quartz–
muscovite dynamoschists on migmatite and pegmatite
ranges from –29.19‰ to –31.58‰. The isotopic
composition of carbon from schistose diabase is
heavier (Table 1). In muscovite dating, the Ar releasing
spectrum was characterized by the “ascending stair-
case” type. Five steps with the highest temperatures
ranging from 1010 to 1100°C lie on the plateau of
1947.8 ± 7.8 Ma (Fig. 4). This age may be slightly
younger than the true age of muscovite crystallization
due to radiogenic Ar losses, which occurred during the
superimposed Caledonian tectono-thermal events;
however, this age is likely close to the real age. The
youngest age is 564 ± 8 Ma at a temperature of 470°C,
but it cannot coincide in time with a real geological
event (Fig. 4).
CM in the Ilikta suite is characterized by a disperse
X-ray amorphous state; phanerocrystalline graphite is
not registered. The spectra of micro-grained aggre-
gates of CM are generally accompanied by lumines-
cence, but even so graphite lines are manifested. The
height and position of the graphite lines indicate a
Fig. 2. (a, b) Raman spectra of CM from quartz–musco-
vite dynamoschists of the Khulurtui block and (c) phyllite-
like schist of the Ilikta suite. (a) Crystalline graphite, pla-
nar segregation; (b) microcrystalline graphite–muscovite
aggregate with residual hydrocarbon radicals (lumines-
cence); (c) X-ray amorphic segregation of bituminoid with
strong luminescence in muscovite.
Intensity, relative units
265
706
3622
3622
3622 3622
2726
1583
1583
1583
2669
1355
2729
2687
2449
3250
265
1582
500 1000 1500 2000 2500 3000 3500 4000
Raman shear, cm1
(c)
(b)
(а)
DOKLADY EARTH SCIENCES Vol. 486 Part 1 2019
EPIGENETIC GRAPHITIZATION IN THE BASEMENT 501
high degree of defect structures and a small size of
crystallites. Some vermicular segregations of CM with
strong luminescence are likely graphite-like matter
with a high content of bitumen-forming components
(Fig. 2c). In comparison with carbon of graphite from
dynamoschists of the Khulurtui block, CM from
schists of the Ilikta suite is enriched in 13C (Table 1).
The lightest isotopic composition is characteristic of
CM from quartz-bearing cataclased schists.
The attribution of carbonization to the schistosity
zones within the Khulturui block, the low-tempera-
ture mineral paragenesis of dynamoschists, and the
low crystallinity of carboniferous material unambigu-
ously point to the carbonization that is manifested at
the retrograde stage in the process of the superim-
posed tectonic deformations. The dating obtained
allows us to establish the relationship between
dynamic metamorphism with accretion of the Akitkan
fold system and the complexes of the Anabar province
at the end of the Paleoproterozoic [11]. In comparison
with CM of the Ilikta suite, where δ13С is close to the
isotopic composition of living biomass, carbon of
dynamoschists (exceptapodiabase) is isotopically
lighter, with δ13С, typical for liquid hydrocarbons of
oil and bitumen in igneous rocks [1, 12]. The presence
of hydrocarbon radicals in CM of dynamoschists
allows us to assume that native carbon and metals were
deposited from hydrocarbon-containing fluid [10],
and paragenesis of tourmaline with muscovite point to
the chloride–borate composition of the solutions that
cause hydrothermal alteration of rocks [6].
The isotopic composition of carbon in the Ilikta
schists could become lighter due to the impact of the
hydrocarbon-containing fluid. However, carbon from
apodiabase dynamoschist was enriched in δ13С proba-
bly because of isotope fractionation [12]. Basite–
ultrabasite paragenesis of metals with an association
with CM is evidence in favor of a deep source of f luid,
when the setting of compression contributed to the
stability of hydrocarbons [7, 8, 10].
However, it cannot be excluded that biogenic car-
bon was transported from the Ilikta schists, when cer-
tain blocks of the Earth’s crust moved to areas with
high temperatures.
Fig. 3. Native Ni and Ni–Fe compound in carbonatized
dynamoschist. Ms, muscovite; C, carbonaceous material.
20 m
Ni-Fe
Ni-Fe
NiNi
MsMs
NiNi
Ni-FeNi-Fe
MsMs
C
C
Ni-Fe
Ni
Ms
Ni
Ni-Fe
Ms
C
C
Table 1. The δ13 C (PDB, ‰) carbon isotopic composition
of graphite
No. Sample
no.
δ13C, ‰
(PDB)
(±0.2‰)
Rocks
Dynamoschists of the Khulurtui block
1 9/13 –31.58 Quartz–muscovite–carbona-
ceous dynamoschist
2 19/13 –29.19 ''
3 32/14 –29.35 Quartz–muscovite–hematite–
carbonaceous dynamoschist
412/13 29.44Schistose pegmatite
5 29/14 –24.93 Schistose diabase
Schists of the Ilikta suite
6 16/14 –27.72 Cataclased quartz–musco-
vite–chlorite schists
7 64/15 –26.61 Quartz–sericite schists
8 78/15-1 –24.15 Quartz–feldspar–sericite schist
9 68/15 –25.39 ''
10 69/15 –28.12 Quartz-bearing quartz–feld-
spar–sericite schist
Fig. 4. 40Ar–39Ar, the age spectrum of muscovite.
400
800
1200
1600
2000
A
ge, Ma
020406080100
1947.8 ± 7.8 Ma
MSWD = 0.52
Probability = 0.72
Cumulative % of 39Ar released
Sample 191/13
(muscovite)
564 ± 8 Ma
502
DOKLADY EARTH SCIENCES Vol. 486 Part 1 2019
SAVELYEVA et al.
ACKNOWLEDGMENTS
This work was supported by the Russian Science
Foundation, project nos. 16-05-00320 and 17-05-
00819.
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Translated by V. Krutikova
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The Karoo-Ferrar igneous province is one of the largest igneous provinces on Earth. It extends from South Africa, along the Trans-Antarctic Mountains to Tasmania and South Australia. Reconstruction of the continents back to the Gondwana configuration in the Early Jurassic reveals a total length of the Karoo-Ferrar province of > 5000 km. New isotope dilution thermal ionization mass spectrometry (ID-TIMS) single grain U-Pb ages for zircon and baddeleyite from Tasmanian dolerites combined with ID-TIMS literature single grain U-Pb ages from the Ferrar and Karoo suites are consistent with the major pulse of synchronous magmatism throughout the province lasting about 1 Ma or less for the major pulse of magmatism at the time of the Toarcian mass extinction event. We argue that the mechanism of synchronization of magmatism over such a short period of time along such a long distance is the major question which has to be answered in search of the correct model for the origin of the Karoo-Ferrar large igneous province. It cannot be reconciled with the lower mantle plume head model with the plume impingement beneath the Karoo. Plume material could not spread beneath the lithosphere at a rate of ~ 5–10 m/yr (5000 km per 0.5–1 Myr), at least based on the current knowledge of the mantle physical properties. It seems unlikely that the entire Karoo-Ferrar large igneous province formed due to long distance magma migration through dykes from the same mantle plume irrespective on the proposed plume centre location. In such case, magma would have had to cross the boundaries (and thus weakness zones) between three future continents. In the framework of the dyke propagation model we would expect dykes to follow these weakness zones, not cross them. In addition to this, the Karoo and Ferrar contain geochemically different igneous rocks, which were not formed from the same magma source, preventing interpretations based on one single plume. Both the Karoo and Ferrar contain low-Ti tholeiites, which are similar by their trace element patterns to modern arc analogues – the Central Andes and Kamchatka, respectively. Thus, our preferred model for the origin of the Karoo-Ferrar large igneous province is associated with subduction of the Phoenix plate beneath the southern Gondwana. Probably, deep slab dehydration at the depth of the mantle transition zone modulated surface volcanism or the Toarcian tectonic event triggered voluminous but short-term melting of mantle, which was metasomatized by subduction-derived fluids.
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An integrated geological and geophysical study was performed to investigate the region of junction of the eastern part of the Central Asian Fold Belt and the Siberian Platform in the Skovorodino–Tommot 3-DV reference profile line (52°–60° N, 122°–129° E), where the belt is separated from the Aldan–Stanovoi Shield of the Platform by a series of deep faults. The main results are as follows: Seismic, density, and geoelectric characteristics of rocks were obtained and used to determine (refine) the intracrustal boundaries of tectonic structures; large-block structure of the Earth’s crust, caused by mantle faults, and the difference between the layered structure of the crust for the shield and fold regions were established; and available paleomagnetic data were used to perform palinspastic reconstructions for 180 and 140 million years, the most productive metallogenic epoch in the region, coeval with collision processes at the closure of the Mongol-Okhotsk paleobasin.
Zonal Distribution and Formation Conditions of Metasomatic Rocks
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