![The geological map of the Anwangshan gold deposit (modified after Lu et al. [43]). There are four gold ore bodies, including No.1 to No.4, distributed along with the shear zone.](https://www.researchgate.net/publication/385113213/figure/fig2/AS:11431281418415282@1746154986318/The-geological-map-of-the-Anwangshan-gold-deposit-modified-after-Lu-et-al-43-There_Q320.jpg)
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Citation: Chen, W.; Yan, Z.; Yuan, J.;
Zhao, Y.; Xu, X.; Sun, L.; Lü, X.; Ma, J.
Gold Mineralization at the
Syenite-Hosted Anwangshan Gold
Deposit, Western Qinling Orogen,
Central China. Minerals 2024,14, 1057.
https://doi.org/10.3390/min14101057
Academic Editor: Bernhard Schulz
Received: 15 September 2024
Revised: 2 October 2024
Accepted: 17 October 2024
Published: 21 October 2024
Copyright: © 2024 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
minerals
Article
Gold Mineralization at the Syenite-Hosted Anwangshan Gold
Deposit, Western Qinling Orogen, Central China
Wenyuan Chen 1,2, Zhibo Yan 3, Jin Yuan 2, Yuanyuan Zhao 2, Xinyu Xu 2, Liqiang Sun 2, Xinbiao Lü 3and
Jian Ma 1, 2, *
1Jiangxi Provincial Key Laboratory of Genesis and Prospect for Strategic Minerals, East China University of
Technology, Nanchang 330013, China; wychen31@163.com
2School of Earth Sciences, East China University of Technology, Nanchang 330013, China
3Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China
*Correspondence: jianma@ecut.edu.cn
Abstract: The Anwangshan gold deposit is located in the northwestern part of the Fengtai Basin,
Western Qinling Orogen (WQO). The gold ore is hosted within quartz syenite and its contact zone. The
U–Pb weighted mean age of the quartz syenite is 231
±
1.8 Ma. It is characterized by high potassium
(K
2
O = 10.13%, K
2
O/Na
2
O > 1) and high magnesium (Mg
#
= 55.31 to 72.78) content, enriched in large
ion lithophile elements (Th, U, and Ba) and light rare earth elements (LREE), with a typical “TNT”
(Ti, Nb, and Ta) deficiency. The geochemical features and Hf isotope compositions (
εHf
(t) =
−
6.68 to
+2.25) suggest that the quartz syenite would form from partial melting of an enriched lithospheric
mantle under an extensional setting. Three generations of gold mineralization have been identified,
including the quartz–sericite–pyrite (Py1) stage I, the quartz–pyrite (Py2)–polymetallic sulfide–early
calcite stage II, and the epidote–late calcite stage III. In situ sulfur isotope analysis of pyrite shows
that Py1 (
δ34
S =
−
1.1 to +3.8‰) possesses mantle sulfur characteristics. However, Py2 has totally
different
δ34
S (+5.1 to +6.7‰), which lies between the typical orogenic gold deposits in the WQO
(
δ34
S = +8 to +12‰) and mantle sulfur. This suggests a mixed source of metamorphosed sediments
and magmatic sulfur during stage II gold mineralization. The fluid inclusions in auriferous quartz
have three different types, including the liquid-rich phase type, pure (gas or liquid)-phase type, and
daughter-minerals-bearing phase type. Multiple-stage fluid inclusions indicate that the ore fluids
are medium-temperature (concentrated at 220 to 270
◦
C), medium-salinity (7.85 to 13.80% NaCleq)
CO
2
–H
2
O–NaCl systems. The salinity is quite different from typical orogenic gold deposits in WQO
and worldwide, and this is more likely to be a mixture of magmatic and metamorphic fluids as
well. In summary, the quartz syenite should have not only a spatio-temporal but also a genetical
relationship with the Anwangshan gold deposit. It could provide most of the gold and ore fluids at
the first stage, with metamorphic fluids and/or gold joining in during the later stages.
Keywords: whole-rock geochemistry; zircon U–Pb dating; in situ sulfur isotope; Anwangshan gold
deposit; West Qinling Orogen
1. Introduction
The Qinling orogenic belt is famous for numerous Triassic magmatic activities and
sediment-hosted gold deposits. The Triassic magmatism mainly developed in the early
Indosinian period (245–235 Ma) and the late Indosinian period (227–205 Ma), during which
there was an intermission of ca. 10 Myr [
1
–
7
]. It is widely recognized that late Indosinian
magmatic activity was formed in a post-collision setting [
5
–
11
]. However, the tectonic
setting of early Indosinian magmatic activity is still under debate, including the active
continental margin model and the early stage of a post-collision setting model [
2
,
4
,
9
,
12
].
The major conflict over the two models concerns the closure time of the Mianlve Ocean.
The active continental margin model is founded on the geochemical characteristics of early
Minerals 2024,14, 1057. https://doi.org/10.3390/min14101057 https://www.mdpi.com/journal/minerals
Minerals 2024,14, 1057 2 of 21
Indosinian magmatism, which resemble those of island arc magmatic rocks [
12
]. The post-
collision setting model is based on geological observation. The conglomerate at the bottom
of the lower part of the molasse formation in the Upper Permian Gequ Formation in the
East Kunlun area is disconformably overlaid on the ophiolite suite of the Mianlve suture
zone, indicating that the Mianlve Ocean had already closed and a continent–continent
collision had occurred in the Late Permian [
13
]. Therefore, understanding the genesis of ca.
230 Ma magmatic activity will be critical to solving the controversy.
Veins, characterized as magmatic intrusions with vein-like or wall-like structures, are
widely distributed around orogenic belts [
14
–
16
]. Sedimentary hosted gold deposits are
generally structurally controlled in the Western Qinling Orogen (WQO, western part of
the Qinling Orogen, divided by the Baoji–Chengdu railway), with abundant magmatic
veins sharing the same pass with gold mineralization or hosting in nearby unmineralized
faults. The genetic relationship between magmatic veins and gold mineralization is a hot
topic in the region [
17
–
22
]. Some scholars believe that magmatic veins are merely spatially
related to gold mineralization without genetic connection, since the magmatic veins are
earlier or later than the gold mineralization [
23
]. Other scholars argue that magmatic
veins are closely genetically related to gold mineralization, not only providing a heat
source but also supplying mineralizing substances [
20
,
21
,
24
,
25
]. It is vital to clarify the
genetical relationship between syenite veins and gold mineralization, especially in terms of
its theoretical significance and implications for regional mineral exploration.
The Anwangshan gold deposit is situated in the Fengtai polymetallic metallogenic
belt, WQO [
26
]. Field investigations show that multiple quartz syenite veins have been in-
troduced into the pyroxenite stock, and gold mineralization is highly spatially related to the
quartz syenite veins. Zircon U–Pb dating of quartz syenite renders an age of 231
±
1.8 Ma,
which is between the early and late Indosinian magmatic activity. In order to understand
the genesis of the ca. 230 Ma quartz syenite and its genetical relationship with gold miner-
alization, this study conducts zircon U–Pb geochronology, whole-rock geochemistry, fluid
inclusion, and pyrite in situ sulfur isotope analysis on representative quartz syenite and
ore samples. Through a comparison study of the nearby Jiuzigou diopsidite and syenite
complex, the petrogenesis of quartz syenite has been put forward. The fluid inclusion and
pyrite sulfur isotope study build a connection between gold mineralization and the quartz
syenite veins. This finally establishes the foundation for exploring the genetic relationship
between magmatic veins and gold mineralization in the WQO.
2. Regional Geology
The Qinling Orogen is a unique continental composite orogenic belt spanning the
central part of China (Figure 1A). Since the break-up of the Rodinia supercontinent in the
Neoproterozoic, the Qinling Orogen has undergone multiple tectonic evolutionary stages,
including the formation of the Qin-Qi-Kun Ocean, oceanic crustal subduction orogeny,
continental collision orogeny, intraplate extension, and intracontinental superimposed
orogeny [
1
,
27
–
29
]. The magmatic intrusions are widely spread and of long duration in the
Qinling Orogen, among which the Indosinian period is the most common. The Indosinian
magmatic activity in the western segment of the orogeny is mainly dated between 245 and
235 Ma, while the eastern segment is concentrated between 227 and 205 Ma [30–32].
The research area is situated at the northwest part of the Fengtai basin in the WQO,
which is famous for its numerous Pb–Zn and gold deposits [
33
,
34
]. The outcropped strata
covered a wide time span from the Early Proterozoic to the Carboniferous (Figure 1B) [
35
].
This includes the Paleoproterozoic Qinling Group (Pt
1
Q), which is in fault contact with the
Lower Paleozoic Danfeng Group (Pz
1
D) to the south and the Ordovician Longwanggou
Formation (Ol) to the north, consisting mainly of gneiss, amphibolite, granulite, and
marble [
36
]. The northern part of the Lower Paleozoic Luohansi Group (Pz
1
L) is bordered
by the Luohansi–Wayaoshang ductile–brittle fault and the Dacaotan Formation, and is
a set of shallowly metamorphosed and strongly deformed volcanic–sedimentary rock
series. The Pz
1
D is a structural mélange belt which has undergone multiple stages of
Minerals 2024,14, 1057 3 of 21
metamorphism and deformation, and mainly comprises arc-related volcanic–sedimentary
rocks in low amphibolite facies [
37
]. The Ordovician Caotangou Group is characterized
by a series of sub-greenschist facies terrigenous volcaniclastic rocks and can be divided
into the Zhangjiazhuang Formation (Ozh) and the Longwanggou Formation (Ol) from the
bottom to the top. The Upper Devonian Dacaotan Formation (D
3
d) comprises greenschist
facies clastic rocks with well-preserved original sedimentary structures. The Carboniferous
Caoliangyi Formation (Cc) is in fault contact with the Ozh in the south and is intruded
by the Baoji batholith in the north. It is mainly composed of quartz sandstone, quartz
conglomerate, etc. (Figure 1B).
Minerals 2024, 14, x FOR PEER REVIEW 3 of 22
Figure 1. (A) Simplified geological map showing major tectonic units of China. (B) Regional geolog-
ical map of the Anwangshan gold deposit. 1 = Anwangshan, 2 = Pangjiahe, 3 = Matigou.
The research area is situated at the northwest part of the Fengtai basin in the WQO,
which is famous for its numerous Pb–Zn and gold deposits [33,34]. The outcropped strata
covered a wide time span from the Early Proterozoic to the Carboniferous (Figure 1B) [35].
This includes the Paleoproterozoic Qinling Group (Pt1Q), which is in fault contact with
the Lower Paleozoic Danfeng Group (Pz1D) to the south and the Ordovician Long-
wanggou Formation (Ol) to the north, consisting mainly of gneiss, amphibolite, granulite,
and marble [36]. The northern part of the Lower Paleozoic Luohansi Group (Pz1L) is bor-
dered by the Luohansi–Wayaoshang ductile–brittle fault and the Dacaotan Formation,
and is a set of shallowly metamorphosed and strongly deformed volcanic–sedimentary
rock series. The Pz1D is a structural mélange belt which has undergone multiple stages of
metamorphism and deformation, and mainly comprises arc-related volcanic–sedimentary
rocks in low amphibolite facies [37]. The Ordovician Caotangou Group is characterized
by a series of sub-greenschist facies terrigenous volcaniclastic rocks and can be divided
into the Zhangjiazhuang Formation (Ozh) and the Longwanggou Formation (Ol) from the
bottom to the top. The Upper Devonian Dacaotan Formation (D3d) comprises greenschist
facies clastic rocks with well-preserved original sedimentary structures. The Carbonifer-
ous Caoliangyi Formation (Cc) is in fault contact with the Ozh in the south and is intruded
by the Baoji batholith in the north. It is mainly composed of quartz sandstone, quartz con-
glomerate, etc. (Figure 1B).
Multiple stages and types of fault are well-developed in the research area [38]. Under
the compression of north–south stress in the late Caledonian, nearly east–west- to north-
west-oriented faults were formed, represented by the Miaoping–Kangjialiang fault and
the Majiayao–Baijiadian ductile–brittle fault which are distributed in the central part of
the region (Figure 1B). The east–west Luohansi–Wayaoshang ductile–brittle fault was
formed during the Indosinian period. The northeast Anwangshan normal fault and the
northeast Yujiayao–Weijiawan strike-slip fault were formed in the Himalayan period, cut-
ting through earlier northwest-oriented structures. All those different faults together
Figure 1. (A) Simplified geological map showing major tectonic units of China. (B) Regional
geological map of the Anwangshan gold deposit. 1 = Anwangshan, 2 = Pangjiahe, 3 = Matigou.
Multiple stages and types of fault are well-developed in the research area [
38
]. Under
the compression of north–south stress in the late Caledonian, nearly east–west- to northwest-
oriented faults were formed, represented by the Miaoping–Kangjialiang fault and the
Majiayao–Baijiadian ductile–brittle fault which are distributed in the central part of the
region (Figure 1B). The east–west Luohansi–Wayaoshang ductile–brittle fault was formed
during the Indosinian period. The northeast Anwangshan normal fault and the northeast
Yujiayao–Weijiawan strike-slip fault were formed in the Himalayan period, cutting through
earlier northwest-oriented structures. All those different faults together shaped the basic
structural framework of the area. Intensive magmatic activities were developed in the
area as well, represented by the northern Baoji batholith which is a multiphase magmatic
intrusion formed at 217 Ma, 212 Ma, and 196 Ma [
39
]. The Tangzang pluton in the southern
part was formed at 428 Ma by fractional crystallization of mafic melt from enriched mantle
with crustal contamination [
40
]. The Jiuzigou stock exposed in the east is a composite
intrusion with diopsidite (235 Ma), biotite diopsidite (232 Ma), and diopside-bearing syenite
(230 Ma) from early to late [41].
Minerals 2024,14, 1057 4 of 21
3. The Anwangshan Gold Deposit
The Anwangshan gold deposit is newly discovered in the WQO [
42
], and it is still
undergoing continuous exploration. The Pt
1
Q, Ozh, Ol, Cc, and Quaternary (Q) sediments
have been found in the mining area (Figure 2). The Ol can be further divided into Ol
s
(composed mainly of tuffaceous siltstone and sericitized) and Ol
f
(composed mainly of
slightly metamorphosed quartz sandstone). The gold ore bodies and magmatic intrusions
are generally hosted within the Ols.
Minerals 2024, 14, x FOR PEER REVIEW 4 of 22
shaped the basic structural framework of the area. Intensive magmatic activities were de-
veloped in the area as well, represented by the northern Baoji batholith which is a multi-
phase magmatic intrusion formed at 217 Ma, 212 Ma, and 196 Ma [39]. The Tangzang
pluton in the southern part was formed at 428 Ma by fractional crystallization of mafic
melt from enriched mantle with crustal contamination [40]. The Jiuzigou stock exposed in
the east is a composite intrusion with diopsidite (235 Ma), biotite diopsidite (232 Ma), and
diopside-bearing syenite (230 Ma) from early to late [41].
3. The Anwangshan Gold Deposit
The Anwangshan gold deposit is newly discovered in the WQO [42], and it is still
undergoing continuous exploration. The Pt1Q, Ozh, Ol, Cc, and Quaternary (Q) sediments
have been found in the mining area (Figure 2). The Ol can be further divided into Ols
(composed mainly of tuffaceous siltstone and sericitized) and Olf (composed mainly of
slightly metamorphosed quartz sandstone). The gold ore bodies and magmatic intrusions
are generally hosted within the Ols.
Figure 2. The geological map of the Anwangshan gold deposit (modified after Lu et al. [43]). There
are four gold ore bodies, including No.1 to No.4, distributed along with the shear zone.
The two northwest-trending Wuxingtai–Nianziba and Miaoping–Kangjialiang faults
are parallel to each other, and crosscut by the late northeast-trending Yujiayao–Weijiawan
fault (Figure 2). Under the influence of the two northwest-trending faults, three strong
mylonitic zones with a width of 20–50 m are distributed between them. Silicification, se-
ricitation, potassization, and pyritization are developed within the mylonitic zone.
The magmatic rocks are highly related to the gold mineralization in the Anwangshan
deposit, including the pyroxenite and the quartz syenite veins. Minor granite porphyry
veins display no spatial relation with gold mineralization and will not be discussed here.
The pyroxenite is mainly exposed in the area sandwiched between the Jiangjiagou and
Hujiagou river, which is 100–200 m in width and approximately 1 km in length. The
Figure 2. The geological map of the Anwangshan gold deposit (modified after Lu et al. [
43
]). There
are four gold ore bodies, including No.1 to No.4, distributed along with the shear zone.
The two northwest-trending Wuxingtai–Nianziba and Miaoping–Kangjialiang faults
are parallel to each other, and crosscut by the late northeast-trending Yujiayao–Weijiawan
fault (Figure 2). Under the influence of the two northwest-trending faults, three strong
mylonitic zones with a width of 20–50 m are distributed between them. Silicification,
sericitation, potassization, and pyritization are developed within the mylonitic zone.
The magmatic rocks are highly related to the gold mineralization in the Anwangshan
deposit, including the pyroxenite and the quartz syenite veins. Minor granite porphyry
veins display no spatial relation with gold mineralization and will not be discussed here.
The pyroxenite is mainly exposed in the area sandwiched between the Jiangjiagou and
Hujiagou river, which is 100–200 m in width and approximately 1 km in length. The
quartz syenite veins intruded into the pyroxenite and Ol
s
tuffaceous siltstone (Figure 3A,B).
The quartz syenite veins vary from 0.5 to 30 m in width and from 10 to 1000 m in length,
showing obvious structural control, with a general northwest trending.
Pyroxenite, displaying a grayish-green color (Figure 3C), is mainly made up of py-
roxene (75%–80%), plagioclase (10%–15%), and apatite (5%–10%) (Figure 3D). The size of
Minerals 2024,14, 1057 5 of 21
different mineral grains ranges from 0.2 to 2 millimeters, with medium- to fine-grained
euhedral textures. The quartz syenite veins display flesh-red color, weathering to grayish-
white to brownish-yellow (Figure 3E). Quartz syenite is mainly made up of K-feldspar
(80%–90%), quartz (5%–10%), plagioclase (5%–10%), and minor biotite (Figure 3F). The
mineral grain size ranges from 0.1 to 3 millimeters. The plagioclase is generally undergoing
sericitization. Accessory minerals, including magnetite, apatite, and pyrite, can be observed
in quartz syenite. Field investigation and microscopic observation both indicate that the
combination of pyroxenite and quartz syenite in the Anwangshan gold deposit have similar
texture and mineralogical features to the 3 km-southeast Jiuzigou complex [41].
Minerals 2024, 14, x FOR PEER REVIEW 5 of 22
quartz syenite veins intruded into the pyroxenite and Ols tuffaceous siltstone (Figure
3A,B). The quartz syenite veins vary from 0.5 to 30 m in width and from 10 to 1000 m in
length, showing obvious structural control, with a general northwest trending.
Pyroxenite, displaying a grayish-green color (Figure 3C), is mainly made up of py-
roxene (75%–80%), plagioclase (10%–15%), and apatite (5%–10%) (Figure 3D). The size of
different mineral grains ranges from 0.2 to 2 millimeters, with medium- to fine-grained
euhedral textures. The quartz syenite veins display flesh-red color, weathering to grayish-
white to brownish-yellow (Figure 3E). Quartz syenite is mainly made up of K-feldspar
(80%–90%), quartz (5%–10%), plagioclase (5%–10%), and minor biotite (Figure 3F). The
mineral grain size ranges from 0.1 to 3 millimeters. The plagioclase is generally undergo-
ing sericitization. Accessory minerals, including magnetite, apatite, and pyrite, can be ob-
served in quartz syenite. Field investigation and microscopic observation both indicate
that the combination of pyroxenite and quartz syenite in the Anwangshan gold deposit
have similar texture and mineralogical features to the 3 km-southeast Jiuzigou complex
[41].
Figure 3. (A) Quartz syenite vein intruded into pyroxenite. (B) Northwest-trending quartz syenite
vein intruded into tuffaceous siltstone of Ols. (C) Fresh pyroxenite. (D) Microphotograph of the py-
roxenite. (E) Fresh quartz syenite. (F) Microphotograph of the quartz syenite. (G) Sketch map of the
Trench 14 in the Anwangshan deposit. Orebody No.2 consists of three branches, including No.2-1,
No.2-2, and No.2-3. Abbreviations: Pl = plagioclase; Px = pyroxene; Kf = K-feldspar; Q = quartz; Ap
= apatite.
Figure 3. (A) Quartz syenite vein intruded into pyroxenite. (B) Northwest-trending quartz syenite
vein intruded into tuffaceous siltstone of Ol
s
. (C) Fresh pyroxenite. (D) Microphotograph of the
pyroxenite. (E) Fresh quartz syenite. (F) Microphotograph of the quartz syenite. (G) Sketch map of
the Trench 14 in the Anwangshan deposit. Orebody No.2 consists of three branches, including No.2-1,
No.2-2, and No.2-3. Abbreviations: Pl = plagioclase; Px = pyroxene; Kf = K-feldspar; Q = quartz;
Ap = apatite.
Four gold ore bodies (No.1, 2, 3, and 4) have been identified within the mining area,
with gold grades peaking at 62.3 g/t. They share a strong spatial relationship with quartz
syenite veins, either enclosed within the veins or situated within contact zones between the
veins and the Ol
s
(Figures 2and 3G). Importantly, ore grades within the veins generally
exceed those in the Ol sediments. The ores can be divided into altered quartz–syenite type
Minerals 2024,14, 1057 6 of 21
and altered sandstone type. Silicification, sericitization, carbonatization, epidotization,
pyritization, and chloritization are widely developed in the mining area.
Based on the field evidence and observation under the microscope, the paragene-
sis of the Anwangshan gold deposit have been divided into three stages. The quartz–
sericite-pyrite (Py1) stage I is characterized by hydrothermal veins comprising coarse-
grained quartz, sericite, and sparsely distributed euhedral Py1 (Figure 4A–C). The quartz–
polymetallic sulfide–early calcite stage II is characterized by anhedral pyrite (Py2) occurring
in association with sphalerite (Figure 4D,E). Minor chalcopyrite presents as solid solutions
within sphalerite. Additionally, early calcite veins crosscutting stage I quartz veins are
widely distributed (Figure 4D,F). The epidote–late calcite stage III is characterized by epi-
dote predominantly developing along fissures. The epidote veins cut through early calcite
veins (Figure 4G,H) and are subsequently cut by even later calcite veins (Figure 4I), with
minimal to no association with gold mineralization.
Minerals 2024, 14, x FOR PEER REVIEW 6 of 22
Four gold ore bodies (No.1, 2, 3, and 4) have been identified within the mining area,
with gold grades peaking at 62.3 g/t. They share a strong spatial relationship with quartz
syenite veins, either enclosed within the veins or situated within contact zones between
the veins and the Ol
s
(Figures 2 and 3G). Importantly, ore grades within the veins gener-
ally exceed those in the Ol sediments. The ores can be divided into altered quartz–syenite
type and altered sandstone type. Silicification, sericitization, carbonatization, epidotiza-
tion, pyritization, and chloritization are widely developed in the mining area.
Based on the field evidence and observation under the microscope, the paragenesis
of the Anwangshan gold deposit have been divided into three stages. The quartz–sericite-
pyrite (Py1) stage I is characterized by hydrothermal veins comprising coarse-grained
quartz, sericite, and sparsely distributed euhedral Py1 (Figure 4A–C). The quartz–
polymetallic sulfide–early calcite stage II is characterized by anhedral pyrite (Py2) occur-
ring in association with sphalerite (Figure 4D,E). Minor chalcopyrite presents as solid so-
lutions within sphalerite. Additionally, early calcite veins crosscutting stage I quartz veins
are widely distributed (Figure 4D,F). The epidote–late calcite stage III is characterized by
epidote predominantly developing along fissures. The epidote veins cut through early
calcite veins (Figure 4G,H) and are subsequently cut by even later calcite veins (Figure 4I),
with minimal to no association with gold mineralization.
Figure 4. Representative hand specimen samples and its photomicrographs in the Anwangshan
gold deposit. (A) Quartz syenite with quartz–pyrite veins crosscutting. (B) Stage I euhedral pyrite
(Py1) in the quartz vein. (C) Py1 coexisting with quartz and sericite. (D) Auriferous quartz syenite
with abundant sulfides and early calcite veins (Cal1) crosscutting. (E) Anhedral pyrite (Py2) coex-
isting with sphalerite. (F) Py2 and chalcopyrite within the Cal1 veins. (G) Epidote veins incised
through Cal1 veins and crosscut by late calcite veins (Cal2). (H) Epidote veins crosscutting the Cal1
veins. (I) Cal2 veins crosscutting the epidote vein. Abbreviations: Py = pyrite; Ser = sericite; Q =
quartz; Sp = sphalerite; Ccp = chalcopyrite; Cal = calcite; Ep = epidote.
4. Sampling and Analytical Methods
The quartz syenite samples for zircon U–Pb dating, Hf isotope, and whole-rock major
and trace element analysis in this study were all collected from the TC-14. Samples for
fluid inclusion micro-thermometry and in situ sulfur isotope analysis were collected from
the No.2 ore bodies.
Zircon from quartz syenite was separated using conventional heavy liquid and mag-
netic techniques in the laboratory of Langfang Yantuo Geological Service Co., Ltd., Hebei
province. Handpicked zircon grains were mounted in epoxy blocks, polished to obtain an
Figure 4. Representative hand specimen samples and its photomicrographs in the Anwangshan gold
deposit. (A) Quartz syenite with quartz–pyrite veins crosscutting. (B) Stage I euhedral pyrite (Py1)
in the quartz vein. (C) Py1 coexisting with quartz and sericite. (D) Auriferous quartz syenite with
abundant sulfides and early calcite veins (Cal1) crosscutting. (E) Anhedral pyrite (Py2) coexisting
with sphalerite. (F) Py2 and chalcopyrite within the Cal1 veins. (G) Epidote veins incised through
Cal1 veins and crosscut by late calcite veins (Cal2). (H) Epidote veins crosscutting the Cal1 veins.
(I) Cal2 veins crosscutting the epidote vein. Abbreviations: Py = pyrite; Ser = sericite; Q = quartz;
Sp = sphalerite; Ccp = chalcopyrite; Cal = calcite; Ep = epidote.
4. Sampling and Analytical Methods
The quartz syenite samples for zircon U–Pb dating, Hf isotope, and whole-rock major
and trace element analysis in this study were all collected from the TC-14. Samples for
fluid inclusion micro-thermometry and in situ sulfur isotope analysis were collected from
the No.2 ore bodies.
Zircon from quartz syenite was separated using conventional heavy liquid and mag-
netic techniques in the laboratory of Langfang Yantuo Geological Service Co., Ltd., Hebei
province (Langfang, China). Handpicked zircon grains were mounted in epoxy blocks, pol-
ished to obtain an even surface, and cleaned in an acid bath before laser ablation–inductively
coupled plasma mass spectrometry (LA–ICP-MS) analysis. Cathodoluminescence (CL)
imaging, U–Pb dating, and Hf isotope analysis of zircon were conducted at the State
Minerals 2024,14, 1057 7 of 21
Key Laboratory of Geological Processes and Mineral Resources (GPMR) (Wuhan, China),
China University of Geosciences, Wuhan. LA–ICP-MS U–Pbdating was conducted using
an Agilent 7500a ICP-MS (Palo Alto, CA, USA) instrument equipped with a GeoLas2005
193 nm ArF excimer laser, with a beam spot diameter of 32
µ
m and a frequency of 8 Hz.
The background acquisition time for each zircon analysis point was 20 s, and the target
signal acquisition time was 40 s. Isotope ratio fractionation correction was performed
using external standard 91500. Detailed operating conditions and data reduction follow
those in Liu et al. [
44
]. Zircon Hf isotope LA–MC-ICP-MS (Resolution S155-Nu Plasma II)
analysis (Charlestown, SC, USA) was conducted near the U–Pb dating sites, with a laser
beam diameter of 44
µ
m and an ablation rate of 8 Hz. The carrier gas is high-purity helium
mixed with argon and a small amount of nitrogen before entering the mass spectrometer.
For detailed instrument parameters and analytical methods, refer to Hu et al. (2012) [45].
Whole-rock major and trace element analysis were completed at ALS Chemex
(Guangzhou) Co., Ltd (Guangzhou, China). Major elements were analyzed using X-ray
fluorescence spectroscopy (XRF), method code ME-XRF26d, with the PANalytical Axios
Max (Malvern, UK) instrument manufactured in the Netherlands. Trace elements were ana-
lyzed using inductively coupled plasma atomic emission spectroscopy (ICP-AES), method
code ME-ICP61, with the Agilent VISTA instrument manufactured in the United States.
Fluid inclusion microthermometry was conducted at GPMR using a LINKAM TMS93
stage (Waltham, MA, USA), capable of temperature measurements ranging from 194 to
600
◦
C, with a temperature reproducibility error of
±
1
◦
C and an ice point temperature
error of
±
0.1
◦
C. Phase transition temperatures of fluid inclusions were carefully observed
and recorded, and salinity was calculated using appropriate formulas.
LA–MC-ICP-MS in situ sulfur isotope analysis was conducted at GPMR, employing
a Resolution S-155 laser ablation system and Nu Plasma II multi-collector inductively
coupled plasma mass spectrometer. The laser spot diameter was set at 33
µ
m, with an
ablation rate of 5 Hz and an energy density of 2 J/cm
2
. High-purity helium gas was used
as the carrier gas, mixed with argon and a small amount of nitrogen before entering the
mass spectrometer, with a single test duration of about 120 s. The test employed a sample-
standard cross-matching method, with the laboratory internal standard pyrite sample WS-1
(
δ34
S
V-CDT
= 0.3
±
0.1‰, Zhu et al. [
46
]) used for analysis, with an analytical precision
of ±0.5‰.
5. Results
5.1. Zircon U–Pb Ages and Hf Isotope Composition
Age data for zircon samples from the quartz syenite are shown in Table A1. Zircon
grains are grayish and euhedral. Their size generally ranges from 50 to 110
µ
m, with
aspect ratios ranging from 2:1 to 4:1. Most of the zircon grains in the CL image exhibit
typical oscillatory zoning (Figure 5). The analyzed zircons have high Th and U, with Th/U
ratios from 0.58 to 2.58 (averaging 1.18), indicating their magmatic affinition [
47
]. A total
of 24 zircon grains were analyzed. Four of them with less than 90-percent concordance
have been excluded, with the remaining data showing
206
Pb/
238
U ages ranging from 226
to 234 Ma, and their weighted-mean
206
Pb/
238
U age is 231
±
1.8 Ma (1
σ
; MSWD = 1.15)
(Figure 5), representing the crystallization age of the quartz syenite. During this period
(ca. 234–224 Ma), the WQO underwent a short quiet period of magmatic activity [48].
The Hf isotope composition of zircon grains in the quartz syenite are presented in
Table A2. Two zircon grains display
176
Lu/
177
Hf ratios at 0.002099 and 0.002063, and the
remaining 21 points have
176
Lu/
177
Hf ratios less than 0.002, indicating minimal radiological
Hf accumulation after zircon crystallization. Therefore, the measured
176
Hf/
177
Hf values
can represent the Hf isotopic composition of the system at the time of zircon formation [
49
].
The measured
176
Hf/
177
Hf ratios in the quartz syenite zircon grains range from 0.2824 to
0.2827, resulting in calculated
εHf
(t) values of
−
6.68 to +2.25. The single-stage Hf model
ages range from 797 to 1128 Ma. The two-stage Hf model ages range from 1107 to 1692 Ma,
predominantly centered around 1310 to 1482 Ma.
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Minerals 2024, 14, x FOR PEER REVIEW 8 of 22
Figure 5. Cathodoluminescence (CL) images of representative zircon grains in the quartz syenite
and its U–Pb Concordia diagrams with weighted-mean ages.
The Hf isotope composition of zircon grains in the quartz syenite are presented in
Table A2. Two zircon grains display
176
Lu/
177
Hf ratios at 0.002099 and 0.002063, and the
remaining 21 points have
176
Lu/
177
Hf ratios less than 0.002, indicating minimal radiological
Hf accumulation after zircon crystallization. Therefore, the measured
176
Hf/
177
Hf values
can represent the Hf isotopic composition of the system at the time of zircon formation
[49]. The measured
176
Hf/
177
Hf ratios in the quartz syenite zircon grains range from 0.2824
to 0.2827, resulting in calculated ε
Hf
(t) values of −6.68 to +2.25. The single-stage Hf model
ages range from 797 to 1128 Ma. The two-stage Hf model ages range from 1107 to 1692
Ma, predominantly centered around 1310 to 1482 Ma.
5.2. Rock Geochemistry
The major and trace elements of the quartz syenite have been presented in Table A3.
The quartz syenite exhibited low contents of SiO
2
(56.68–64.42%), TiO
2
(0.28–0.69%), and
Na
2
O (3.32–4.63%). In contrast, the contents of Al
2
O
3
(14.88–17.65%), Mg
#
(55.31–72.78),
K
2
O (3.55–8.75%), total-alkali (Na
2
O + K
2
O = 7.47–12.72%) and potassium–sodium ratio
(K
2
O/Na
2
O = 0.85–2.22) were generally high in the quartz syenite. In the total-alkali-silica
(TAS) diagram, the samples are plotted in the syenite and syenite diorite fields (Figure
6A). All samples plot in the shoshonite field in the K
2
O–SiO
2
diagram (Figure 6B). Fur-
thermore, the Al
2
O
3
/ (Na
2
O + K
2
O) (A/NK) and Al
2
O
3
/ (CaO + Na
2
O + K
2
O) (A/CNK) ratios
are from 1.08 to 1.43 and from 0.77 to 1.06, respectively, indicating metaluminous to
weakly peraluminous characteristics (Figure 6C). On the basis of the Zr + Nb + Ce + Y
versus Na
2
O + K
2
O/CaO diagram, all samples are collectively plotted in the field of the A-
type granitoids (Figure 6D).
Figure 5. Cathodoluminescence (CL) images of representative zircon grains in the quartz syenite and
its U–Pb Concordia diagrams with weighted-mean ages.
5.2. Rock Geochemistry
The major and trace elements of the quartz syenite have been presented in Table A3.
The quartz syenite exhibited low contents of SiO
2
(56.68–64.42%), TiO
2
(0.28–0.69%), and
Na
2
O (3.32–4.63%). In contrast, the contents of Al
2
O
3
(14.88–17.65%), Mg
#
(55.31–72.78),
K
2
O (3.55–8.75%), total-alkali (Na
2
O+K
2
O = 7.47–12.72%) and potassium–sodium ratio
(K
2
O/Na
2
O = 0.85–2.22) were generally high in the quartz syenite. In the total-alkali-silica
(TAS) diagram, the samples are plotted in the syenite and syenite diorite fields (Figure 6A).
All samples plot in the shoshonite field in the K
2
O–SiO
2
diagram (Figure 6B). Furthermore,
the Al
2
O
3
/ (Na
2
O + K
2
O) (A/NK) and Al
2
O
3
/ (CaO + Na
2
O + K
2
O) (A/CNK) ratios are
from 1.08 to 1.43 and from 0.77 to 1.06, respectively, indicating metaluminous to weakly
peraluminous characteristics (Figure 6C). On the basis of the Zr + Nb + Ce + Y versus
Na
2
O + K
2
O/CaO diagram, all samples are collectively plotted in the field of the A-type
granitoids (Figure 6D).
The quartz syenite generally has relatively high total rare earth element (
Σ
REE) concen-
trations, ranging from 555.95 ppm to 718.8 ppm (average at 639.03 ppm). The LREE/HREE
ratio ranges from 22.72 to 44.44, and the (La/Yb)
N
varies from 42.4 to 116.8 (Table A3),
indicating significant fractionation between light and heavy rare earth elements. The
chondrite-normalized rare earth element distribution curves display strong rightward
slopes (Figure 7A).
The
δ
Eu values range from 0.73 to 0.76, indicating weakly negative anomalies. This
suggests the magma source from a plagioclase-stable reservoir or undergoing plagioclase
fractionation. δCe values range from 0.82 to 0.96, with no significant anomalies. The trace
element distribution patterns of all quartz syenite samples are similar to each other. The
large ion lithophile elements (LILE), such as Ba, Th, K, Sr, and LREE, are enriched, and the
high-field-strength elements (HFSE), including Nb, Ta, Ti, are depleted (Figure 7B).
Minerals 2024,14, 1057 9 of 21
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Figure 6. Classification diagrams of samples analyzed from the quartz syenite. (A) TAS diagram,
according to Wilson [50]. (B) K2O–SiO2 diagram, according to Peccerillo and Taylor [51]. (C) A/CN-
A/CNK diagram, according to Rickwood [52]. (D) Discrimination diagram of granites, according to
Whalen et al. [53]. Data on diopside-bearing syenites within the Jiuzigou complex are shown for
comparison [54]. OGT: undifferentiated I-, S-, and M-type granite zone. FG: differentiated I-type
granite zone.
The quartz syenite generally has relatively high total rare earth element (ΣREE) con-
centrations, ranging from 555.95 ppm to 718.8 ppm (average at 639.03 ppm). The
LREE/HREE ratio ranges from 22.72 to 44.44, and the (La/Yb) N varies from 42.4 to 116.8
(Table A3), indicating significant fractionation between light and heavy rare earth ele-
ments. The chondrite-normalized rare earth element distribution curves display strong
rightward slopes (Figure 7A).
The δEu values range from 0.73 to 0.76, indicating weakly negative anomalies. This
suggests the magma source from a plagioclase-stable reservoir or undergoing plagioclase
fractionation. δCe values range from 0.82 to 0.96, with no significant anomalies. The trace
element distribution patterns of all quartz syenite samples are similar to each other. The
large ion lithophile elements (LILE), such as Ba, Th, K, Sr, and LREE, are enriched, and
the high-field-strength elements (HFSE), including Nb, Ta, Ti, are depleted (Figure 7B).
Figure 7. (A) Chondrite-normalized REE pattern diagrams. (B) Primitive mantle-normalized trace
element diagrams. Data for normalization are from Sun and McDonough [55].
Figure 6. Classification diagrams of samples analyzed from the quartz syenite. (A) TAS diagram,
according to Wilson [
50
]. (B) K
2
O–SiO
2
diagram, according to Peccerillo and Taylor [
51
]. (C) A/CN-
A/CNK diagram, according to Rickwood [
52
]. (D) Discrimination diagram of granites, according
to Whalen et al. [
53
]. Data on diopside-bearing syenites within the Jiuzigou complex are shown for
comparison [
54
]. OGT: undifferentiated I-, S-, and M-type granite zone. FG: differentiated I-type
granite zone.
Minerals 2024, 14, x FOR PEER REVIEW 9 of 22
Figure 6. Classification diagrams of samples analyzed from the quartz syenite. (A) TAS diagram,
according to Wilson [50]. (B) K2O–SiO2 diagram, according to Peccerillo and Taylor [51]. (C) A/CN-
A/CNK diagram, according to Rickwood [52]. (D) Discrimination diagram of granites, according to
Whalen et al. [53]. Data on diopside-bearing syenites within the Jiuzigou complex are shown for
comparison [54]. OGT: undifferentiated I-, S-, and M-type granite zone. FG: differentiated I-type
granite zone.
The quartz syenite generally has relatively high total rare earth element (ΣREE) con-
centrations, ranging from 555.95 ppm to 718.8 ppm (average at 639.03 ppm). The
LREE/HREE ratio ranges from 22.72 to 44.44, and the (La/Yb) N varies from 42.4 to 116.8
(Table A3), indicating significant fractionation between light and heavy rare earth ele-
ments. The chondrite-normalized rare earth element distribution curves display strong
rightward slopes (Figure 7A).
The δEu values range from 0.73 to 0.76, indicating weakly negative anomalies. This
suggests the magma source from a plagioclase-stable reservoir or undergoing plagioclase
fractionation. δCe values range from 0.82 to 0.96, with no significant anomalies. The trace
element distribution patterns of all quartz syenite samples are similar to each other. The
large ion lithophile elements (LILE), such as Ba, Th, K, Sr, and LREE, are enriched, and
the high-field-strength elements (HFSE), including Nb, Ta, Ti, are depleted (Figure 7B).
Figure 7. (A) Chondrite-normalized REE pattern diagrams. (B) Primitive mantle-normalized trace
element diagrams. Data for normalization are from Sun and McDonough [55].
Figure 7. (A) Chondrite-normalized REE pattern diagrams. (B) Primitive mantle-normalized trace
element diagrams. Data for normalization are from Sun and McDonough [55].
5.3. Fluid Geochemistry
Fluid inclusions in the Anwangshan deposit are characterized by being numerous,
small-sized, and morphologically complex. Three types of fluid inclusions are observed in
auriferous quartz formed during stages I and II: the liquid-rich phase (Figure 8A,B), pure
(gas or liquid) phase (Figure 8C), and daughter-minerals-bearing phase (Figure 8D). The
liquid-rich inclusions are elliptical or negatively crystalline, with sizes ranging from 3 to
7
µ
m and gas-phase percentages ranging from 5% to 30%. The pure phase inclusions are
commonly 2 to 9
µ
m in diameter, and are mostly elliptical in shape. The daughter-minerals-
bearing inclusions exhibit elliptical, elongated, or irregular shapes, with sizes ranging from
3 to 15 µm.
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5.3. Fluid Geochemistry
Fluid inclusions in the Anwangshan deposit are characterized by being numerous,
small-sized, and morphologically complex. Three types of fluid inclusions are observed
in auriferous quartz formed during stages I and II: the liquid-rich phase (Figure 8A,B),
pure (gas or liquid) phase (Figure 8C), and daughter-minerals-bearing phase (Figure 8D).
The liquid-rich inclusions are elliptical or negatively crystalline, with sizes ranging from
3 to 7 μm and gas-phase percentages ranging from 5% to 30%. The pure phase inclusions
are commonly 2 to 9 μm in diameter, and are mostly elliptical in shape. The daughter-
minerals-bearing inclusions exhibit elliptical, elongated, or irregular shapes, with sizes
ranging from 3 to 15 μm.
Figure 8. Micrographs of fluid inclusions in the Anwangshan gold deposit. Liquid-rich-phase-type
inclusions (A,B), pure-phase-type inclusions (C), and daughter-minerals-bearing phase inclusions
(D).
Primary fluid inclusions from the two stages were selected for microthermometric
analysis. Results are presented in Table A4 and Figure 9A. Stage I homogenization tem-
peratures range from 206 to 321 °C, with a concentration between 250 and 260 °C. Stage II
homogenization temperatures range from 155 to 276 °C, with a concentration between 220
and 230 °C. There is a trend of decreasing fluid temperature from stage I to stage II. Salin-
ity was calculated based on the ice point data using the formula proposed by Potter et al.
[56]: w(NaCleq)/% = 0.00 + 1.76985Tm − 4.2384 × 10
−2
Tm
2
+ 5.2778 × 10
−4
Tm
3
, where Tm is
the absolute value of the ice point temperature. A total of 11 ice point temperature data
were collected. The calculated salinity values range from 7.85 to 13.80%NaCleq (Figure
9B), predominantly concentrated between 9 and 12%NaCleq, which is of moderate salin-
ity.
Figure 8. Micrographs of fluid inclusions in the Anwangshan gold deposit. Liquid-rich-phase-type in-
clusions (A,B), pure-phase-type inclusions (C), and daughter-minerals-bearing phase
inclusions (D)
.
Primary fluid inclusions from the two stages were selected for microthermometric
analysis. Results are presented in Table A4 and Figure 9A. Stage I homogenization tem-
peratures range from 206 to 321
◦
C, with a concentration between 250 and 260
◦
C. Stage II
homogenization temperatures range from 155 to 276
◦
C, with a concentration between 220
and 230
◦
C. There is a trend of decreasing fluid temperature from stage I to stage II. Salinity
was calculated based on the ice point data using the formula proposed by Potter et al. [
56
]:
w(NaCleq)/% = 0.00 + 1.76985Tm
−
4.2384
×
10
−2
Tm
2
+ 5.2778
×
10
−4
Tm
3
, where Tm is
the absolute value of the ice point temperature. A total of 11 ice point temperature data
were collected. The calculated salinity values range from 7.85 to 13.80%NaCleq (Figure 9B),
predominantly concentrated between 9 and 12%NaCleq, which is of moderate salinity.
Minerals 2024, 14, x FOR PEER REVIEW 11 of 22
Figure 9. (A) Histograms of the total homogenization temperatures of fluid inclusions in quartz. (B)
Histograms of the salinities of fluid inclusions in quartz.
5.4. In Situ Sulfur Isotope Composition of Pyrite
This study completed in situ sulfur isotope composition analysis of pyrite at 18 points
across four ore samples (Table A5). For stage I pyrite (Py1), 10 analysis points showed a
relatively concentrated distribution between −1.1 and +3.8‰. For stage II pyrite (Py2), all
eight analysis points exhibit values higher than those of Py1, ranging from +5.1 to +6.7‰,
indicating the addition of more 34S during the stage II gold mineralization.
6. Discussion
6.1. Genesis of Ore-Bearing Quartz Syenite and Its Tectonic Implication
The syenite–ultramafic complex is generally interpreted as partial melting of mantle-
derived rocks in an extensional tectonic setting [57–61], or as a result of lower crust melt-
ing triggered by mantle-derived magma diapir [62–65]. The quartz syenite in the Anwang-
shan gold deposit exhibits characteristics of high potassium (average K2O of 10.13%,
K2O/Na2O > 1) and high magnesium values (Mg# 64.59). It is difficult for a single crustal-
source rock to generate rocks with high potassium and Mg# greater than 40 through partial
melting [66,67]. Liu [68] suggests that crustal materials in the northern Qinling terrane are
moderately enriched in LREE, with obvious negative Eu anomalies, and have high HREE
contents. These differ from the quartz syenite, which shows high enrichment in LREE,
weak negative Eu anomalies, and low HREE contents (Figure 7A). Additionally, no mafic
micro-granular enclave (MME) was observed in the field within the syenite veins, exclud-
ing the possibility that the syenite veins in Anwangshan were formed by direct partial
melting of crustal rocks or the mixing of crust and mantle magma caused by mantle-de-
rived magma diapir [69].
The εHf(t) values of quartz syenite range from −6.68 to +2.25, slightly lower than those
of the diopside-bearing syenite in Jiuzigou, and much lower than the depleted mantle
values during the same period (Figure 10). When the εHf(t) of zircon is negative, it is gen-
erally believed that magma originated from the crust or enriched mantle, or resulted from
crustal mantle mixing. The average Sr content of quartz syenite is 1205 ppm, which is
much higher than the Sr contents of depleted mantle and lower crust (20 ppm and 290
ppm, respectively; Wang et al. [70]), but similar to the enriched mantle (1100 ppm; Chen
and Zhai [71]). Moreover, the higher K2O + Na2O content (7.47%–12.72%) and (La/Yb) N
ratio (42.4–116.8) of quartz syenite is comparable to the composition of alkaline rocks
formed by the low-level partial melting of lithospheric mantle ((La/Yb) N= 23.56–130.64,
K2O + Na2O = 9.39%–14.28%, Eby [72],Pin et al. [73]; Laporte et al. [74]), suggesting that
the quartz syenite may be derived from the low-level partial melting of the enriched lith-
ospheric mantle [75,76]. Therefore, the crustal source and crustal mantle mixing could
have been ruled out again. The relatively positive εHf(t) values of the quartz syenite and
diopside-bearing syenite could not exclude the involvement of asthenosphere mantle
Figure 9. (A) Histograms of the total homogenization temperatures of fluid inclusions in quartz.
(B) Histograms of the salinities of fluid inclusions in quartz.
5.4. In Situ Sulfur Isotope Composition of Pyrite
This study completed in situ sulfur isotope composition analysis of pyrite at 18 points
across four ore samples (Table A5). For stage I pyrite (Py1), 10 analysis points showed a
Minerals 2024,14, 1057 11 of 21
relatively concentrated distribution between
−
1.1 and +3.8‰. For stage II pyrite (Py2), all
eight analysis points exhibit values higher than those of Py1, ranging from +5.1 to +6.7‰,
indicating the addition of more 34S during the stage II gold mineralization.
6. Discussion
6.1. Genesis of Ore-Bearing Quartz Syenite and Its Tectonic Implication
The syenite–ultramafic complex is generally interpreted as partial melting of mantle-
derived rocks in an extensional tectonic setting [
57
–
61
], or as a result of lower crust melting
triggered by mantle-derived magma diapir [
62
–
65
]. The quartz syenite in the Anwang-
shan gold deposit exhibits characteristics of high potassium (average K
2
O of 10.13%,
K
2
O/Na
2
O > 1) and high magnesium values (Mg
#
64.59). It is difficult for a single crustal-
source rock to generate rocks with high potassium and Mg
#
greater than 40 through partial
melting [
66
,
67
]. Liu [
68
] suggests that crustal materials in the northern Qinling terrane are
moderately enriched in LREE, with obvious negative Eu anomalies, and have high HREE
contents. These differ from the quartz syenite, which shows high enrichment in LREE,
weak negative Eu anomalies, and low HREE contents (Figure 7A). Additionally, no mafic
micro-granular enclave (MME) was observed in the field within the syenite veins, excluding
the possibility that the syenite veins in Anwangshan were formed by direct partial melting
of crustal rocks or the mixing of crust and mantle magma caused by mantle-derived magma
diapir [69].
The
εHf
(t) values of quartz syenite range from
−
6.68 to +2.25, slightly lower than those
of the diopside-bearing syenite in Jiuzigou, and much lower than the depleted mantle
values during the same period (Figure 10). When the
εHf
(t) of zircon is negative, it is
generally believed that magma originated from the crust or enriched mantle, or resulted
from crustal mantle mixing. The average Sr content of quartz syenite is 1205 ppm, which is
much higher than the Sr contents of depleted mantle and lower crust (20 ppm and 290 ppm,
respectively; Wang et al. [
70
]), but similar to the enriched mantle (1100 ppm; Chen and
Zhai [
71
]). Moreover, the higher K
2
O + Na
2
O content (7.47%–12.72%) and (La/Yb)
N
ratio
(42.4–116.8) of quartz syenite is comparable to the composition of alkaline rocks formed
by the low-level partial melting of lithospheric mantle ((La/Yb)
N
= 23.56–130.64, K
2
O +
Na
2
O = 9.39%–14.28%, Eby [
72
], Pin et al. [
73
]; Laporte et al. [
74
]), suggesting that the quartz
syenite may be derived from the low-level partial melting of the enriched lithospheric
mantle [
75
,
76
]. Therefore, the crustal source and crustal mantle mixing could have been
ruled out again. The relatively positive
εHf
(t) values of the quartz syenite and diopside-
bearing syenite could not exclude the involvement of asthenosphere mantle material or
newborn crustal material [
41
]. Previous research of the nearby Jiuzigou complex, including
diopsidite (235.2 Ma), biotite diopsidite (232.8 Ma), and diopside-bearing syenite (230.7 Ma),
indicate that they resulted from partial melting of an enriched lithospheric mantle in an
extensional background [
41
]. The phenomenon in the field and under the microscope aligns
with the observation of quartz syenite veins intruded into pyroxenite in the Anwangshan
deposit. The emplacement age of quartz syenite at 231
±
1.8 Ma is also consistent with
the diopside-bearing syenite in the Jiuzigou complex. It is not easy to deny that the two
simultaneous syenite–ultramafic complexes should generate from the same source region.
Moreover, the lg [CaO/(Na
2
O+K
2
O)]
−
SiO
2
diagram indicates that the 231 Ma
quartz syenite should form in an extensional background (Figure 11A). The enrichment of
Th, Rb, Ba, and LREE and the negative anomalies of Ta, Nb, and Ti (“TNT” deficiency) also
indicate that the source mantle has already been metamorphized by the melt generated by
subducting plates [
55
,
77
]. The w (Rb)
−
w (Nb + Y) diagrams show that the quartz syenite
has a strong post-collisional affiliation (Figure 11B). If the early Indosinian magmatic activity
(245–235 Ma) is still under an active continental margin environment [
12
,
13
], there will
not be enough time to finish the subsequent continental collision and transform the stress
environment from compression to extension. Therefore, the post-collision setting model
is preferred to describe the tectonic setting of the early Indosinian magmatic activity. In
summary, the 231 Ma quartz syenite is formed by a low-level partial melting of the enriched
Minerals 2024,14, 1057 12 of 21
lithospheric mantle under the early stage of a post-collision setting [
2
,
4
]. This is consistent
with the characteristics of the Qinling orogenic belt transitioning from compression to
extension at around 230 Ma [41,78].
Minerals 2024, 14, x FOR PEER REVIEW 12 of 22
material or newborn crustal material [41]. Previous research of the nearby Jiuzigou com-
plex, including diopsidite (235.2 Ma), biotite diopsidite (232.8 Ma), and diopside-bearing
syenite (230.7 Ma), indicate that they resulted from partial melting of an enriched litho-
spheric mantle in an extensional background [41]. The phenomenon in the field and under
the microscope aligns with the observation of quartz syenite veins intruded into pyroxe-
nite in the Anwangshan deposit. The emplacement age of quartz syenite at 231 ± 1.8 Ma
is also consistent with the diopside-bearing syenite in the Jiuzigou complex. It is not easy
to deny that the two simultaneous syenite–ultramafic complexes should generate from
the same source region.
Figure 10. （A）Diagrams of initial εHf values versus the U–Pb ages of zircon from the quartz syenite
and Jiuzigou complex. (B) Enlarged data display of Figure 11A. Data for Jiuzigou complex are from
Gong [54].
Moreover, the lg [CaO/ (Na2O + K2O)] − SiO2 diagram indicates that the 231 Ma quartz
syenite should form in an extensional background (Figure 11A). The enrichment of Th,
Rb, Ba, and LREE and the negative anomalies of Ta, Nb, and Ti (“TNT” deficiency) also
indicate that the source mantle has already been metamorphized by the melt generated
by subducting plates [55,77]. The w (Rb) − w (Nb + Y) diagrams show that the quartz
syenite has a strong post-collisional affiliation (Figure 11B). If the early Indosinian mag-
matic activity (245–235 Ma) is still under an active continental margin environment
[12,13], there will not be enough time to finish the subsequent continental collision and
transform the stress environment from compression to extension. Therefore, the post-col-
lision setting model is preferred to describe the tectonic setting of the early Indosinian
magmatic activity. In summary, the 231 Ma quartz syenite is formed by a low-level partial
melting of the enriched lithospheric mantle under the early stage of a post-collision setting
[2,4]. This is consistent with the characteristics of the Qinling orogenic belt transitioning
from compression to extension at around 230 Ma [41,78].
Figure 11. Discriminant diagram of the Anwangshan quartz syenite. lg [CaO/(Na2O + K2O)] − SiO2
discriminant (A), according to Brown et al. [79]. (B) Rb − (Nb + Y) diagram (Pearce [80]). ORG: ocean
Figure 10. (A) Diagrams of initial
ε
Hf values versus the U–Pb ages of zircon from the quartz syenite
and Jiuzigou complex. (B) Enlarged data display of Figure 11A. Data for Jiuzigou complex are from
Gong [54].
Minerals 2024, 14, x FOR PEER REVIEW 12 of 22
material or newborn crustal material [41]. Previous research of the nearby Jiuzigou com-
plex, including diopsidite (235.2 Ma), biotite diopsidite (232.8 Ma), and diopside-bearing
syenite (230.7 Ma), indicate that they resulted from partial melting of an enriched litho-
spheric mantle in an extensional background [41]. The phenomenon in the field and under
the microscope aligns with the observation of quartz syenite veins intruded into pyroxe-
nite in the Anwangshan deposit. The emplacement age of quartz syenite at 231 ± 1.8 Ma
is also consistent with the diopside-bearing syenite in the Jiuzigou complex. It is not easy
to deny that the two simultaneous syenite–ultramafic complexes should generate from
the same source region.
Figure 10. （A）Diagrams of initial εHf val ues vers us the U–Pb ages of zirco n from th e quartz sy enite
and Jiuzigou complex. (B) Enlarged data display of Figure 11A. Data for Jiuzigou complex are from
Gong [54].
Moreover, the lg [CaO/ (Na2O + K2O)] − SiO2 diagram indicates that the 231 Ma quartz
syenite should form in an extensional background (Figure 11A). The enrichment of Th,
Rb, Ba, and LREE and the negative anomalies of Ta, Nb, and Ti (“TNT” deficiency) also
indicate that the source mantle has already been metamorphized by the melt generated
by subducting plates [55,77]. The w (Rb) − w (Nb + Y) diagrams show that the quartz
syenite has a strong post-collisional affiliation (Figure 11B). If the early Indosinian mag-
matic activity (245–235 Ma) is still under an active continental margin environment
[12,13], there will not be enough time to finish the subsequent continental collision and
transform the stress environment from compression to extension. Therefore, the post-col-
lision setting model is preferred to describe the tectonic setting of the early Indosinian
magmatic activity. In summary, the 231 Ma quartz syenite is formed by a low-level partial
melting of the enriched lithospheric mantle under the early stage of a post-collision setting
[2,4]. This is consistent with the characteristics of the Qinling orogenic belt transitioning
from compression to extension at around 230 Ma [41,78].
Figure 11. Discriminant diagram of the Anwangshan quartz syenite. lg [CaO/(Na2O + K2O)] − SiO2
discriminant (A), according to Brown et al. [79]. (B) Rb − (Nb + Y) diagram (Pearce [80]). ORG: ocean
Figure 11. Discriminant diagram of the Anwangshan quartz syenite. lg [CaO/(Na
2
O+K
2
O)]
−
SiO
2
discriminant (A), according to Brown et al. [
79
]. (B) Rb
−
(Nb + Y) diagram (Pearce [
80
]). ORG: ocean
ridge granite, post-COLG: post-collision granites, syn-COLG: syn-collision granites, VAG: volcanic
arc granites, WPG: within-plate granites.
6.2. Relationship between Quartz Syenite and Gold Mineralization
The Anwangshan gold deposit exhibits a close spatial–temporal relationship with
quartz syenite. The occurrence of ore bodies is identical to that of the quartz syenite vein.
The intensity of gold mineralization and alteration exhibits zoning characteristics, with the
quartz syenite vein serving as the center of gold mineralization (Figure 3E). The silicification,
sericitization, pyritization, and the gold grade on both sides of the vein gradually weaken,
indicating that quartz syenite has a direct controlling effect on gold mineralization.
Alkaline rocks usually have low background of gold (average gold content at about
3.4 ppb; Boyle [
81
]), and they generally cannot provide enough gold for mineralization.
However, Mutschler [
82
] proposed that when the gold content in alkaline rocks exceeds
10 ppb, they can serve as part of the sources for gold deposits. Both the Hougou gold
deposit and the Dongping gold deposit in the Zhangxuan area, north China, have close
tempo-spatial and genetic links with syenites [
83
], and the gold contents in the syenites
of the two are 22.2 ppb and 10.1 ppb, respectively [
84
]. The quartz syenite veins in the
Anwangshan gold deposit have an average gold content of 12.8 ppb [
41
]. The sulfur
isotope composition of Py1 (
−
1.1‰ to +3.8‰) shows clear mantle sulfur affiliation, which
Minerals 2024,14, 1057 13 of 21
is significantly different from orogenic gold deposits related to regional metamorphism
in the WQO (Figure 12). Thus, the quartz syenite could provide part of the gold source
during the first mineralization stage. During stage II, the sulfur isotope composition of
Py2 ranges between Py1 and the majority of orogenic gold deposits (deep gray) in the
WQO (Figure 12). This indicates that metamorphic gold may join in during the late gold
mineralization stage in the Anwangshan gold deposit.
Minerals 2024, 14, x FOR PEER REVIEW 13 of 22
ridge granite, post-COLG: post-collision granites, syn-COLG: syn-collision granites, VAG: volcanic
arc granites, WPG: within-plate granites.
6.2. Relationship between Quartz Syenite and Gold Mineralization
The Anwangshan gold deposit exhibits a close spatial–temporal relationship with
quartz syenite. The occurrence of ore bodies is identical to that of the quartz syenite vein.
The intensity of gold mineralization and alteration exhibits zoning characteristics, with
the quartz syenite vein serving as the center of gold mineralization (Figure 3E). The silic-
ification, sericitization, pyritization, and the gold grade on both sides of the vein gradually
weaken, indicating that quartz syenite has a direct controlling effect on gold mineraliza-
tion.
Alkaline rocks usually have low background of gold (average gold content at about
3.4 ppb; Boyle [81]), and they generally cannot provide enough gold for mineralization.
However, Mutschler [82] proposed that when the gold content in alkaline rocks exceeds
10 ppb, they can serve as part of the sources for gold deposits. Both the Hougou gold
deposit and the Dongping gold deposit in the Zhangxuan area, north China, have close
tempo-spatial and genetic links with syenites [83], and the gold contents in the syenites of
the two are 22.2 ppb and 10.1 ppb, respectively [84]. The quartz syenite veins in the
Anwangshan gold deposit have an average gold content of 12.8 ppb [41]. The sulfur iso-
tope composition of Py1 (−1.1‰ to +3.8‰) shows clear mantle sulfur affiliation, which is
significantly different from orogenic gold deposits related to regional metamorphism in
the WQO (Figure 12). Thus, the quartz syenite could provide part of the gold source dur-
ing the first mineralization stage. During stage II, the sulfur isotope composition of Py2
ranges between Py1 and the majority of orogenic gold deposits (deep gray) in the WQO
(Figure 12). This indicates that metamorphic gold may join in during the late gold miner-
alization stage in the Anwangshan gold deposit.
Figure 12. Comparison of sulfur isotopes between the Anwangshan gold deposit and the typical
orogenic gold deposits in the WQO. The shallow gray belt represents a mantle sulfur, and the
deep gray belt represents the majority sulfur isotope composition of orogenic gold deposits in the
WQO [85].
The point that syenite could provide ore-forming fluids during gold mineralization
process has also been reported. Ludovic and Michel [
86
] suggest that metamorphic fluids
and magmatic fluids from ore-bearing syenite jointly provided ore-forming fluids for
late-stage gold mineralization in the Beattie gold deposit, Canada. The study in the
Kirkland Lake–Larder Lake gold mineralization belt in Ontario, Canada, also suggested that
regional gold mineralization fluids originated from a deep alkaline magma–hydrothermal
system [
87
]. Previous studies on gold deposits closely related to magmatic dykes in
the WQO have also shown that intermediate to mafic dykes formed by partial melting
of enriched mantle provided ore-forming fluids for gold mineralization [
20
,
88
,
89
]. The
fluid inclusion studies of the Anwangshan gold deposit show that stage I displays mid-
temperature ranges (206 to 321
◦
C), with a trend of decline from early to later stages.
The appearance of daughter-mineral-bearing inclusions and the medium salinity (7.85 to
13.80% NaCleq) are quite different from those of typical orogenic gold deposits which are
dominated by CO
2
-rich vapor–liquid two-phase fluid inclusions with 3 to 7% NaCl eq in
salinity [
90
,
91
]. This indicates the involvement of high-salinity fluid, most likely magmatic
fluids in the Anwangshan deposit.
Minerals 2024,14, 1057 14 of 21
In conclusion, the in situ sulfur isotope and fluid inclusion study both support strong
magmatic affiliation during stage I gold mineralization. Combined with the geological
observation, the quartz syenite is an unavoidable source to provide gold and ore fluid in the
Anwangshan gold deposit. Mao [
19
] and Wang et al. [
65
] suggest that the Triassic large-scale
lead–zinc–gold mineralization in the WQO is a product of tectonic–magmatic-fluid activity.
The age of the quartz syenite (231.0
±
1.8 Ma) is younger than the nearby Tangzang pluton
(428 Ma, Wu et al. [
39
]) and the regional magmatic activity (ca. 240 Ma; Hejiazhuang pluton,
Liujiagou pluton, granite porphyry dykes in the Pangjiahe and Matigou gold deposit;
Ma, 2018 and references therein [
81
]). However, it is consistent with the mineralization
age of the nearby orogenic gold deposits, including the Pangjiahe (231.2 Ma) and the
Matigou (234 Ma) gold deposit [
34
,
92
]. Furthermore, the Qinling Orogen’s tectonic setting
changed from compression to extension at around 230 Ma, which would have provided
a favorable environment for auriferous fluid migration and precipitation in the shear
zones. Therefore, the ore-bearing quartz syenite should be the product of the same tectonic–
magmatic–fluid activity at around 230 Ma [
19
,
93
]. Unlike typical orogenic gold deposits
formed by Indosinian metamorphism in the WQO, the Anwangshan gold deposit has
the same mineralization age as the Pangjiahe and Matigou gold deposits (ca. 230 Ma),
but a totally different metal and fluid source in stage I. The mixing of magmatic fluids
with metamorphic fluids led to stage II sulfur isotope compositions and ore-forming fluid
temperatures similar to those of orogenic gold deposits (Figures 9A and 12).
7. Conclusions
The quartz syenite in the Anwangshan gold deposit was formed at 231
±
1.8 Ma,
during an intermittent period of two-stage Indosinian magmatic activity in the WQO. The
quartz syenite exhibits characteristics of high potassium, high magnesium, enrichment
of LILE, LREE, and depletion of HFSE, with a typical “TNT” (Ti, Nb, and Ta) deficiency.
Combined with the Hf isotope composition, it should be the product of partial melting of
enriched lithospheric mantle in the post-collision extension background of the WQO. The
geological characteristics, in situ sulfur isotope composition, and fluid inclusion studies all
indicate that the early stage I gold mineralization in the Anwangshan gold deposit have
strong magmatic affiliation, with metamorphic substance involvement in the late stage II
gold mineralization.
Author Contributions: Conceptualization, J.M. and X.L.; methodology, W.C.; formal analysis, W.C.,
L.S. and Z.Y.; investigation, J.Y., Y.Z. and X.X.; resources, Z.Y.; data curation, W.C. and Z.Y.; writing—
original draft preparation, W.C.; writing—review and editing, J.M.; supervision, X.L.; funding
acquisition, J.M. All authors have read and agreed to the published version of the manuscript.
Funding: This research was funded by the National Natural Science Foundation of China (41902076),
the Jiangxi Provincial Natural Science Foundation (20232BAB213059), and the Jiangxi Provincial Key
Laboratory of Genesis and Prospect for Strategic Minerals (No. 2023SSY01011). And The APC was
funded by [20232BAB213059].
Data Availability Statement: Data are contained within the article.
Acknowledgments: We acknowledge fieldwork help from the 211 Geological Brigade of the Sino
Shanxi Nuclear Industry Group, Xi’an. We acknowledge the generous help from editors and reviewers.
Conflicts of Interest: The authors declare no conflict of interest.
Minerals 2024,14, 1057 15 of 21
Appendix A
Table A1. LA–ICP-MS zircon U–Pb data of quartz syenite from the Anwangshan gold deposit.
Spot
No.
Content/ppm 207Pb/206 Pb 207Pb/235 U206Pb/238 U207Pb/206 Pb 207Pb/235 U206Pb/238 U
U Th Pb Th/U Ratio 1σRatio 1σRatio 1σAge 1σAge 1σAge 1σ
No.1 181 259 17.3 1.43 0.05473 0.00199 0.27235 0.00819 0.03667 0.00053 466 81 245 7 232 3
No.2 627 609 46.6 0.97 0.05172 0.00136 0.26284 0.00629 0.03695 0.00046 272 59 237 5 234 3
No.3 748 820 60.4 1.09 0.05313 0.00115 0.26769 0.00581 0.03656 0.00037 345 50 241 5 231 3
No.4 1274 958 85.1 0.75 0.05029 0.00131 0.25228 0.00666 0.03633 0.00043 209 94 228 5 230 3
No.6 1497 1071 93 0.71 0.05158 0.00124 0.26096 0.00668 0.03657 0.00031 265 56 235 5 232 2
No.7 919 880 66.8 0.95 0.05537 0.00102 0.28097 0.00564 0.03673 0.0005 428 45 251 4 233 3
No.8 1074 1137 82.8 1.05 0.05289 0.00099 0.26991 0.00505 0.03695 0.00036 324 43 243 4 234 2
No.10 574 587 43.9 1.02 0.05205 0.00126 0.25865 0.00664 0.03603 0.00046 287 56 234 5 228 3
No.11 1233 894 75.7 0.72 0.05092 0.00086 0.25275 0.00436 0.03593 0.00031 235 39 229 4 228 2
No.13 460 620 41.8 1.32 0.05491 0.0013 0.27372 0.00659 0.03618 0.00043 409 54 246 5 229 3
No.14 1249 992 88.1 0.73 0.05727 0.00319 0.28469 0.01538 0.03599 0.00087 501 122 254 12 228 5
No.15 169 420 23.4 2.48 0.05424 0.00151 0.2686 0.00786 0.0361 0.00062 389 63 242 6 229 4
No.16 241 396 24.8 1.64 0.05481 0.00651 0.26891 0.03092 0.03574 0.00085 406 264 242 25 226 5
No.17 1744 1014 102 0.58 0.05088 0.00118 0.2537 0.00678 0.03608 0.00058 235 49 230 5 229 4
No.18 374 968 49.5 2.58 0.0516 0.00091 0.26408 0.0052 0.03698
0.000382
333 38 238 4 234 2
No.20 906 746 62.9 0.828 0.05523 0.00109 0.27166 0.00517 0.03568 0.0003 420 44 244 4 226 2
No.21 662 634 43.5 0.95 0.05251 0.00122 0.26702 0.00636 0.03686 0.00037 309 562 240 5 233 2
No.22 213 394 23.6 1.84 0.05156 0.00139 0.2555 0.00674 0.03598 0.00031 265 58 231 5 228 2
No.23 638 601 49 0.94 0.05602 0.00137 0.28401 0.00755 0.03662 0.00038 454 54 254 6 232 2
No.24 398 396 30.9 0.99 0.05478 0.00214 0.27394 0.01035 0.03629 0.0004 467 82 246 8 230 2
Table A2. Hf isotope composition of zircons in the quartz syenite.
Analysis
No. Age 176Yb
177Hf
176Lu
177Hf
176Hf
177Hf 2α εHf εHf (t) tDM (Hf) tDM (C) fLu/Hf
LH-4-1 232 ±3 0.025914
0.0011569
0.282589 0.000022 −6.47 −1.44 942 1359 −0.97
LH-4-2 234 ±3 0.034333
0.0015881
0.282555 0.000025 −7.67 −2.72 1002 1440 −0.95
LH-4-3 231 ±3 0.046215
0.0019609
0.282566 0.000029 −7.28 −2.4 996 1419 −0.94
LH-4-4 230 ±3 0.050392
0.0020349
0.282564 0.000037 −7.37 −2.47 1002 1426 −0.94
LH-4-5 232 ±2 0.033383
0.0016093
0.282556 0.000026 −7.65 −2.68 1002 1440 −0.95
LH-4-6 233 ±3 0.046072
0.0020993
0.282594 0.000022 −6.31 −1.44 960 1359 −0.94
LH-4-7 234 ±2 0.028519
0.0013355
0.282535 0.000019 −8.37 −3.39 1023 1482 −0.96
LH-4-8 228 ±3 0.015010
0.0006804
0.282554 0.000024 −7.72 −2.61 980 1435 −0.98
LH-4-9 228 ±2 0.019341
0.0007752
0.282484 0.000036 −10.2 −5.12 1080 1592 −0.98
LH-4-10 229 ±3 0.004002
0.0001692
0.282568 0.000021 −7.23 −2.04 948 1399 −0.99
LH-4-11 228 ±5 0.011150
0.0004350
0.282571 0.000024 −7.13 −1.97 950 1394 −0.99
LH-6-1 229 ±4 0.050771
0.0020629
0.282705 0.000028 −2.36 2.52 797 1107 −0.94
LH-6-2 226 ±5 0.004477
0.0001959
0.282437 0.000028 −11.84 −6.68 1128 1692 −0.99
LH-6-3 229 ±4 0.004669
0.0001967
0.282464 0.000034 −10.9 −5.72 1091 1631 −0.99
LH-6-4 234 ±2 0.007766
0.0003070
0.282531 0.000037 −8.53 −3.35 1002 1482 −0.99
LH-6-5 226 ±2 0.012339
0.0004776
0.282575 0.000032 −6.96 −1.83 945 1384 −0.99
LH-6-6 233 ±2 0.038755
0.0014199
0.282629 0.000040 −5.05 −0.06 892 1272 −0.96
LH-6-7 228 ±2 0.050945
0.0018332
0.282586 0.000023 −6.58 −1.65 964 1373 −0.94
LH-6-8 232 ±2 0.021080
0.0008728
0.282610 0.000030 −5.74 −0.66 906 1310 −0.97
LH-6-9 230 ±2 0.011014
0.0004390
0.282515 0.000029 −9.11 −3.95 1028 1520 −0.99
LH-6-10 234 ±2 0.053334
0.0019466
0.282612 0.000025 −5.65 −0.73 929 1315 −0.94
LH-6-11 228 ±3 0.027761
0.0010363
0.282632 0.000034 −4.95 0.08 879 1262 −0.97
LH-6-12 228 ±2 0.008001
0.0003248
0.282605 0.000063 −5.92 −0.77 900 1316 −0.99
Minerals 2024,14, 1057 16 of 21
Table A3. Major (wt%) and trace elements (ppm) content of quartz syenite.
Sample
No. L7-2 L7-7 L8-7 YFG-11 YFG-15 YFG-16
SiO263.64 64.42 60.19 56.68 59.25 60.94
TiO20.31 0.28 0.39 0.69 0.59 0.61
Al2O317.65 17.48 16.58 14.7 14.88 15.29
MgO 0.44 0.52 1.33 2.97 2.64 2.82
CaO 0.72 0.29 2.39 4.76 3.76 2.69
Na2O 4.63 3.95 3.71 3.92 3.32 4.54
K2O 8.09 8.75 7.08 3.55 5.42 3.84
Na2O+K2O 12.72 12.7 10.79 7.47 8.74 8.38
K2O/Na2O 1.75 2.22 1.91 0.91 1.63 0.85
Mg#55.31 72.78 68.52 61.27 64.46 65.19
A/CNK 1 1.06 0.91 0.77 0.82 0.92
A/NK 1.08 1.09 1.2 1.43 1.31 1.31
δ7.84 7.53 6.77 4.08 4.7 3.91
Cs 1.17 1.45 1.3 1.09 2.03 0.92
Rb 131 175.5 131 95.7 133.5 87.3
Ba 7590 6280 3160 3570 4290 3350
Th 21.7 38.6 23.8 48.4 44.7 43.7
U 1.18 3.54 2.61 5.41 5.75 5.78
V 44 43 88 143 108 111
Cr 10 10 40 40 40 30
Ga 17.5 18 16.5 20.1 18.8 19.2
Sr 2350 842 1320 994 973 755
Y 24.8 24.5 19.5 36.8 29.5 28.4
Zr 64 96 180 321 336 339
Nb 17.4 18.3 18.5 32 28.4 27.4
La 168 190.5 241 184 144 146
Ce 294 318 327 333 257 261
Pr 29.3 29.7 26.8 33.4 25.8 26
Nd 95.8 93.7 75.9 115.5 88.2 86.9
Sm 16.5 14.75 9.83 18.6 14.65 14.35
Eu 3.41 3.13 2.06 4 3.01 2.98
Gd 10.4 9.23 6.43 12.6 9.55 9.31
Tb 1.37 1.17 0.84 1.59 1.24 1.15
Dy 6.12 5.44 3.74 7.52 5.7 5.9
Ho 0.94 0.89 0.69 1.36 1.03 1.03
Er 2.11 2.11 1.72 3.31 2.72 2.68
Tm 0.26 0.29 0.24 0.47 0.37 0.4
Yb 1.56 1.73 1.48 3 2.33 2.47
Lu 0.22 0.26 0.22 0.45 0.35 0.39
Hf 2.1 2.9 4.1 7.4 7.6 7.8
Ta 1.5 1.4 0.9 1.5 1.3 1.4
W 282322
Sn 333444
ΣREE 629.99 670.9 697.95 718.8 555.95 560.56
LREE 607.01 649.78 682.59 688.5 532.66 537.23
HREE 22.98 21.12 15.36 30.3 23.29 23.33
LREE/HREE 26.41 30.77 44.44 22.72 22.87 23.03
(La/Yb)N77.25 78.99 116.8 43.99 44.33 42.4
δEu 0.74 0.76 0.74 0.75 0.73 0.74
Minerals 2024,14, 1057 17 of 21
Table A4. Physical and chemical characteristics of fluid inclusions in the Anwangshan gold deposit.
Stage Mineral Size (µm) Gas–Liquid
Ratio (%)
Homogenization
Temperature (◦C)
Freezing
Point (◦C)
I Quartz 2 ×4 10 289 −9.83
I Quartz 3 ×4 10 315 −7.72
I Quartz 3 ×3 10 280
I Quartz 3 ×4 15 256
I Quartz 4 ×4 10 244
I Quartz 3 ×4 10 278
I Quartz 4 ×3 15 262
I Quartz 2 ×4 10 234
I Quartz 2 ×3 10 243
I Quartz 2 ×4 10 303
I Quartz 2 ×3 10 287
I Quartz 6 ×4 30 206 −5
I Quartz 3 ×3 10 254
I Quartz 2 ×4 10 212
I Quartz 4 ×7 10 273
I Quartz 2 ×3 20 264
I Quartz 2 ×4 10 211
I Quartz 6 ×12 15 235
I Quartz 4 ×10 30 258
I Quartz 2 ×3 20 234
I Quartz 3 ×4 25 255
I Quartz 2 ×4 15 260
I Quartz 4 ×6 10 227
I Quartz 2 ×4 20 321 −5.92
II Quartz 3 ×4 10 276
II Quartz 3 ×6 15 210 −7.52
II Quartz 4 ×4 10 215 −6.98
II Quartz 4 ×5 10 230
II Quartz 4 ×4 10 252
II Quartz 4 ×4 10 230 −6.03
II Quartz 3 ×4 10 244
II Quartz 3 ×4 10 201
II Quartz 4 ×4 10 229 −8.13
II Quartz 3 ×4 10 235
II Quartz 3 ×5 10 215
II Quartz 3 ×2 20 229 −6.43
II Quartz 2 ×3 20 231
II Quartz 2 ×4 10 211
II Quartz 2 ×3 10 252 −6.83
II Quartz 6 ×16 20 243
II Quartz 2 ×3 20 186
II Quartz 2 ×2 20 190
II Quartz 3 ×2 10 240 −5.9
II Quartz 2 ×4 15 155
II Quartz 2 ×6 20 237
II Quartz 3 ×5 25 221
II Quartz 2 ×5 15 230
II Quartz 1 ×2 30 179
II Quartz 2 ×3 30 193
II Quartz 2 ×3 20 235
Minerals 2024,14, 1057 18 of 21
Table A5. Sulfur isotope composition of pyrite in the Anwangshan gold deposit.
Sample Number Pyrite Type δ34S (‰)
Aws-55-1 Py2 6.2
Aws-55-2 Py2 6.4
Aws-55-3 Py2 6.5
Aws-55-4 Py2 6.7
Aws-55-5 Py2 5.1
Aws-55-6 Py2 5.8
Aws-55-7 Py2 5.8
Aws-8-1 Py1 3.3
Aws-8-2 Py2 5.6
Aws-4-1 Py1 0.7
Aws-4-2 Py1 −1.1
Aws-4-3 Py1 3.8
Aws-21-1 Py1 0.5
Aws-21-2 Py1 2.6
Aws-21-3 Py1 2.7
Aws-21-4 Py1 2.9
Aws-21-5 Py1 2.1
Aws-21-5 Py1 3.0
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