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Genesis of the Xiuwenghala Gold Deposit in the Beishan Orogen, Northwest China: Evidence from Geology, Fluid Inclusion, and H–O–S–Pb Isotopes
Author(s) -
Wang Qisong,
Zhang Jing,
Shu Sunping,
Lai Chunkit,
Xu Bowen,
Sun Haiwei
Publication year - 2019
Publication title -
resource geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.597
H-Index - 43
eISSN - 1751-3928
pISSN - 1344-1698
DOI - 10.1111/rge.12198
Subject(s) - geology , sericite , geochemistry , arsenopyrite , sphalerite , galena , fluid inclusions , silicic , chalcedony , calcite , pyrite , cassiterite , quartz , mineralization (soil science) , ore genesis , chlorite , magmatic water , mineralogy , chalcopyrite , basalt , chemistry , tin , paleontology , organic chemistry , copper , soil science , soil water
The Xiuwenghala gold deposit is located in the Beishan Orogen of the southern Central Asian Orogenic Belt. The vein/lenticular gold orebodies are controlled by Northeast‐trending faults and are hosted mainly in the brecciated/altered tuff and rhyolite porphyry of the Lower Carboniferous Baishan Formation. Metallic minerals include mainly pyrite and minor chalcopyrite, arsenopyrite, galena, and sphalerite, whilst nonmetallic minerals include quartz, chalcedony, sericite, chlorite, and calcite. Hydrothermal alterations consist of silicic, sericite, chlorite, and carbonate. Alteration/mineralization processes comprise three stages: pre‐ore silicic alteration (Stage I), syn‐ore quartz‐chalcedony‐polymetallic sulfide mineralization (Stage II), and post‐ore quartz‐calcite veining (Stage III). Fluid inclusions (FIs) in quartz and calcite are dominated by L‐type with minor V‐type and lack any daughter mineral‐bearing or CO 2 ‐rich/‐bearing inclusions. From Stages I to III, the FIs homogenized at 240–260°C, 220–250°C, and 150–190°C, with corresponding salinities of 2.9–10.9, 3.2–11.1, and 2.9–11.9 wt.% NaCl eqv., respectively. The mineralization depth at Xiuwenghala is estimated to be relatively shallow (<1 km). FI results indicate that the ore‐forming fluids belong to a low to medium‐temperature, low‐salinity, and low‐density NaCl‐H 2 O system. Theδ 18 O H 2 Ovalues decrease from Stage I to III (3.7‰, 1.7–2.4‰, and −1.7 to 0.9‰, respectively), and a similar trend is found for their δD H 2 Ovalues (−104 to −90‰, −126 to −86‰, and −130 to −106‰, respectively). This indicates that the fluid source gradually evolved from magmatic to meteoric. δ 34 S values of the hydrothermal pyrites (−3.0 to 0.0‰; avg. −1.1‰) resemble those of typical magmatic/mantle‐derived sulfides. Pyrite Pb isotopic compositions ( 206 Pb/ 204 Pb = 18.409–18.767, 207 Pb/ 204 Pb = 15.600–15.715, 208 Pb /204 Pb = 38.173–38.654) are similar to those of the (sub)volcanic ore host, indicating that the origin of ore‐forming material was mainly the upper crustal (sub)volcanic rocks. Integrating evidence from geology, FIs, and H–O–S–Pb isotopes, we suggest that Xiuwenghala is best classified as a low‐sulfidation epithermal gold deposit.