Well-Constrained Mineralization Ages by Integrated 40Ar/39Ar and U-Pb Dating Techniques for the Xitian W-Sn Polymetallic Deposit, South China

Abstract Mineralization ages of many mineral deposit types (such as orogenic Au, stratabound Cu, and Mississippi Valley-type Pb-Zn deposits) are still difficult to date by the traditional isotopic chronometry because of the lack of suitable minerals. We have made efforts to establish a widely suitable dating technique to determine ore formation ages using a high-precision 40Ar/39Ar method on ubiquitously present fluid inclusions in quartz, sphalerite, and other nonpotassium minerals from hydrothermal deposits. The Xitian W-Sn polymetallic deposit in central South China contains several minerals suitable for isotopic dating for interchronometer comparison. 40Ar/39Ar laser step heating of 16 micas from ore veins, greisen, and metallogenic granites yields flat age spectra and thus well-defined ore formation ages ranging from 152.4 ± 1.5 (2σ) to 148.1 ± 1.4 Ma with an average of 150.2 ± 0.6 Ma. 40Ar/39Ar progressive crushing of nine quartz samples produces well-defined isochron lines for their primary fluid inclusions corresponding to isochron ages of 153.7–149.9 Ma with an average of 151.6 ± 0.6 Ma. Cassiterites from three hand specimens have weighted mean 206Pb/238U ages of 151.5 ± 1.7 (2σ), 149.7 ± 2.1, and 151.7 ± 2.1 Ma. All these new geochronological dates and previous molybdenite Re-Os ages yield well-constrained mineralization ages of 153–148 Ma for the Xitian W-Sn polymetallic deposit, which also confirms conclusively that the quartz 40Ar/39Ar progressive crushing technique is a feasible, valid dating technique. Furthermore, significant age information on the secondary fluid inclusions is potentially obtained simultaneously by this technique. We expect that this novel dating technique will be widely applied to determine the geologic fluids trapped in minerals during hydrothermal mineralization, hydrocarbon accumulation, metamorphism, tectonic activities, and other geologic processes.

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Fluid Inclusions and C, H, O, S, and Pb Isotopic Compositions of the Dabaoshan Cu Polymetallic Deposit, Northern Guangdong Province, South China

Resource Geology ◽

10.1111/rge.12169 ◽

2018 ◽

Vol 68 (3) ◽

pp. 258-274

Author(s):

Hongying Qu ◽

Jingwen Mao ◽

Shumin Zhou

Keyword(s):

Fluid Inclusions ◽

South China ◽

Guangdong Province ◽

Polymetallic Deposit ◽

Isotopic Compositions ◽

Northern Guangdong

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Fluid Inclusions and H-O-C-S-Pb Isotope Studies of the Xinmin Cu-Au-Ag Polymetallic Deposit in the Qinzhou-Hangzhou Metallogenic Belt, South China: Constraints on Fluid Origin and Evolution

Geofluids ◽

10.1155/2021/5171579 ◽

2021 ◽

Vol 2021 ◽

pp. 1-17

Author(s):

Rui-Chun Duan ◽

Shao-Yong Jiang

Keyword(s):

High Temperature ◽

Fluid Inclusions ◽

South China ◽

Late Stage ◽

High Salinity ◽

Main Stage ◽

Pb Isotope ◽

Isotope Data ◽

Polymetallic Deposit ◽

Metallogenic Belt

Qinzhou-Hangzhou metallogenic belt is an important polymetallic (Cu, Mo, W, Sn, Pb, Zn, Au, and Ag) belt in South China. The Xinmin polymetallic deposit is located in the southwestern segment of this belt, which ore bodies hosted in the contact zone of granite and Lower Devonian sedimentary strata and in the structure fractured zone within the strata. Three hydrothermal stages can be distinguished: quartz+tourmaline+pyrite (early stage), tourmaline+pyrite+galena+bismuthinite+sphalerite+chalcopyrite+pyrrhotite (main stage), and quartz+calcite+dolomite (late stage). The mineralizing fluid system can be described as aqueous with medium-high salinity (2.7-50.7 wt.‰ NaCl equiv. in the main stage and 0.18-8.81 wt.‰ NaCl equiv. in the late stage) and medium-high temperature of 485°C to 205°C (main stage) and 300°C to 116°C (late stage). The trapping pressures varied from 2 MPa to 30 MPa (main stage) and 0.4 MPa to 9 MPa (late stage). The δ 18 O values of quartz range from 6.7‰ to 8.5‰, and the δ D values for fluid inclusions in quartz range from -45‰ to -52‰. The calcite has C-isotopes ranging from -5.8‰ to +0.7‰ and O-isotopes from +12.7‰ to 21.4‰. H-O-C isotope data are consistent with a hydrothermal fluid derived from the Cretaceous granitoid magma. The δ 34 S values of sulfides are -3.3‰ to +1.9‰. Sulfides have 206Pb/204Pb ratios of 18.377 to 18.473, 207Pb/204Pb ratios of 15.606 to 16.684, and 208Pb/204Pb ratios of 38.613 to 38.902. The S-Pb isotope data suggest derivation of S and Pb mainly from the Cretaceous granitic magma. It is concluded that the Xinmin deposit is a medium-high temperature, medium-high salinity hydrothermal polymetallic deposit, related to the granitic magmatism and strictly controlled by the fault and shattered zones.

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He-Ar Isotopes and Trace Gas Compositions of Fluid Inclusions in Massive Sulphides from the Yushui Copper-Polymetallic Deposit, South China: Metallogenic Implications

Minerals ◽

10.3390/min9050258 ◽

2019 ◽

Vol 9 (5) ◽

pp. 258

Author(s):

Yi Huang ◽

Zhongwei Wu ◽

Xiaoming Sun ◽

Yan Wang ◽

Guiyong Shi ◽

...

Keyword(s):

Fluid Inclusions ◽

South China ◽

Massive Sulphide ◽

Trace Gas ◽

Main Stage ◽

Sulphide Deposit ◽

Rock Interaction ◽

Origin And Evolution ◽

Polymetallic Deposit ◽

Ore Bodies

The Yushui ore deposit, located in the middle section of the Yong’an-Meixian Hercynian depression, is a medium-sized Cu-polymetallic massive sulphide deposit in Eastern Guangdong Province, South China. This deposit is characterized by unusually high copper grade (up to 50–60 wt. % Cu). Other metallic elements, such as lead, zinc and silver, are also economically important in the Yushui ore bodies. The aim of this study was to apply N2–Ar–He systematics, together with organic gases (light-hydrocarbon tracers), to constrain the origin and evolution of ore-forming fluids. The helium-argon isotopes and trace gas compositions of fluid inclusions trapped within metal sulphide minerals were measured for a number of bonanza ores from the Yushui deposit. The noble gas concentrations in the studied samples vary over one to two orders of magnitude (4He: 2.27–160.00 × 10−5 cm3 STP g−1; 3He: 0.53–34.88 × 10−12 cm3 STP g−1; 40Ar: 6.28–37.82 × 10−7 cm3 STP g−1; 36Ar: 1.25–10.40 × 10−9 cm3 STP g−1). Our data show a narrow range of 3He/4He ratios from 0.006 to 0.056 Ra (~0.026 Ra on average, n = 8), which are considerably lower than the modern atmospheric end-member value; whereas the 40Ar/36Ar ratios (ranging from 333.76 to 501.68, with an average of 397.53) are significantly greater than that of air-saturated water. Most of the bornite samples have somewhat higher 3He/4He ratios of trapped fluids when compared to chalcopyrite. Overall, these He-Ar results are well within the range of crustal reservoir, thus implying a predominantly crustal source (originated from Caledonian basement) for ore-forming solutions, with little contribution from mantle-derived fluids. Analysis of the N2–Ar–He composition in Cu-rich sulphides indicates that the Yushui ore-forming fluids were probably derived from formation water (or basinal hot brines). Moreover, organic gas species identified in sulphide-hosted fluid inclusions are mainly composed of C1–C4 alkanes, while the concentrations of unsaturated olefins and aromatic hydrocarbons are very low. In particular, most chalcopyrite samples with relatively low 3He/4He ratios (0.006–0.016 Ra) and 40Ar*/4He values (0.0002–0.0012) are generally characterized by very high CO2/CH4 ratios (~60–102). All these suggest that main-stage Cu-Ag metallogenic processes might have not been affected by high-temperature magmatic activities or superimposed by strong metamorphic overprinting, although some chalcopyrite-rich ores appear to be influenced by later stage hydrothermal processes. In summary, neither magmatic input nor convecting seawater has played an important role in the formation of Yushui copper-polymetallic deposit. The massive sulphide ore bodies were products of water–rock interaction between metal-bearing basinal brines and the host sedimentary strata.

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LINKAGES BETWEEN TECTONICS AND SEDIMENTARY RECORDS OF MESOZOIC INTRACONTINENTAL DEFORMATION IN CENTRAL SOUTH CHINA

10.1130/abs/2017am-302692 ◽

2017 ◽

Author(s):

Huimin Ma ◽

◽

Yu Wang ◽

Yajuan Huang

Keyword(s):

South China ◽

Sedimentary Records ◽

Intracontinental Deformation ◽

Central South

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The Temperature of Halite Crystallization in the Badenian Saline Basins, in the Context of Paleoclimate Reconstruction of the Carpathian Area

Minerals ◽

10.3390/min11080831 ◽

2021 ◽

Vol 11 (8) ◽

pp. 831

Author(s):

Anatoliy R. Galamay ◽

Krzysztof Bukowski ◽

Igor M. Zinczuk ◽

Fanwei Meng

Keyword(s):

Temperature Distribution ◽

Air Temperature ◽

Fluid Inclusions ◽

Middle Miocene ◽

Single Phase ◽

Dead Sea ◽

Paleoclimate Reconstruction ◽

Near Surface ◽

Carpathian Region ◽

Primary Fluid

Currently, fluid inclusions in halite have been frequently studied for the purpose of paleoclimate reconstruction. For example, to determine the air temperature in the Middle Miocene (Badenian), we examine single-phase primary fluid inclusions of the bottom halites (chevron and full-faceted) and near-surface (cumulate) halites collected from the salt-bearing deposits of the Carpathian region. Our analyses showed that the temperatures of near-bottom brines varied in ranges from 19.5 to 22.0 °C and 24.0 to 26.0 °C, while the temperatures of the surface brines ranged from 34.0 to 36.0 °C. Based on these data, such as an earlier study of lithology and sedimentary structures of the Badenian rock salts, the crystallization of bottom halite developed in the basin from concentrated and cooled near-surface brines of about 30 m depth. Our results comply with the data on the temperature distribution in the modern Dead Sea.

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