Geology, isotope geochemistry, and ore genesis of the Yindonggou Ag–Au(–Pb–Zn) deposit, Hubei Province, China

Abstract

The Yindonggou Ag–Au(–Pb–Zn) deposit is hosted by metamorphosed volcanic rocks of the ca. 740–760 Ma Wudangshan Group in the Proterozoic Wudang Block of the southern part of the Qinling Orogen, central China. The deposit consists of a series of mineralized quartz veins located in the Yindongyan Anticline. Based on the mineral assemblages and cross‐cutting relationships of quartz veins, the deposit can be divided into: (1) early fine‐grained quartz–sphalerite–galena veins; (2) fine‐grained quartz–silver–gold veins containing minor amounts of pyrite; (3) coarse‐grained quartz veins with minor amounts of galena, sphalerite, and chalcopyrite; and (4) late ankerite–quartz veins. Most of the Pb–Zn mineralization formed during the early (Stage 1) veins followed by the deposition of Ag–Au mineralization in the Stage 2 veins. The δ18O value for the ore‐forming fluids decreases from 6.6–9.4‰ in the Stage 1 veins through 3.6–4.9‰ in the Stage 2 veins to −1.2‰ to 0.4‰ in the Stage 3 veins (the δ18O values could not be determined for the Stage 4 veins). Furthermore, the δD values are −74‰ for the Stage 1 veins, −95‰ to −56 ‰ for the Stage 2 veins, and −48‰ to −73‰ for the Stage 3 veins. The δ13C values for ankerite in the Stage 4 veins are between −2.9‰ and −1.1‰. The δD vs. δ18OH2O plot for these values indicates that there was a shift from metamorphic fluids during the formation of the early veins to meteoric fluids during the formation of the later veins at the deposit. The H–O–C isotope systematics also indicate that the ore fluids forming the deposit were probably initially sourced from metamorphic dehydration of volcanic‐carbonate rocks in the ca. 740–760 Ma Wudangshan Group and with time gradually mixed with meteoric water by Stage 4. The δ34S values for sulphides from the deposit range from −0.9‰ to 7.1‰ in the Stage 1 veins, 3.8‰ to 5.0‰ in the Stage 2 veins, and 2.4‰ to 11.3‰ in the wallrocks. Sulphides from the mineralized Stage 1 veins yield 206Pb/204Pb ratios of 16.44–16.6, 207Pb/204Pb ratios of 15.25–15.5, and 208Pb/204Pb ratios of 36.4–36.98. Five pyrite samples from the Stage 2 veins yield 206Pb/204Pb ratios of 16.475–16.529, 207Pb/204Pb ratios of 15.346–15.395, and 208Pb/204Pb ratios of 36.49–36.616. Both the S and Pb isotope ratios are between the ratios for units in the Wudangshan Group and mantle but differ from other lithological units in the Wudang Block, which suggest that the mineralized fluids interacted with both the Wudangshan Group and deep‐seated sources. Thus, we suggest that the original ore‐forming fluids are metamorphic in origin, and the metal deposition resulted from fluid mixing. From the characteristics observed, the Yindonggou Ag–Au(–Pb–Zn) deposit can be classified as an orogenic‐type deposit generated during the Triassic Qinling Orogeny resulting from northward oceanic plate subduction along the Mian‐Lue Suture. Copyright © 2014 John Wiley & Sons, Ltd.

Geology, geochemistry and genesis of the Huachanggou gold deposit, western Qinling Orogen, central China

“…Subsequently, voluminous meteoric water may have been introduced into the ore‐forming system and mixed with existing ore fluids, causing widespread development of the middle‐stage quartz–polymetallic sulphide veins. This corresponds well to the H–O isotope features and mineral assemblages of the middle‐stage mineralization at the Huachanggou deposit similar to many other famous orogenic‐types deposits around the world (Chen et al ., , , , ; J. Li et al ., ; Qi et al ., ; Zhang et al ., , , ; Zheng et al ., ; Yue et al ., ). Progressive input of meteoric water may have gradually diluted the ore‐forming fluids and reduced the temperature of the metallogenic system, and eventually, caused the development of late‐stage infertile carbonate ± quartz veinlets, commonly characterized by the comb texture and CO 2 ‐poor FIs with homogenization temperatures of <230 °C.…”

Triassic tectonics and mineral systems in the Qinling Orogen, central China

“…In the SQL, the Xujiapo Au deposit and Yindonggou Ag–Au–Pb–Zn deposits (Fig. ) were constrained to have formed in the Triassic (Table ; Chen et al ., ) but are now suggested to have formed in a subduction‐related accretion orogeny (Yue et al ., ). The Huachanggou Au deposit is located in the Mian‐Lue Suture (Fig.…”

Geology, fluid inclusions and sulphur isotopes of the Zhifang Mo deposit in Qinling Orogen, central China: a case study of orogenic‐type Mo deposits

“…The salient features of orogenic‐type mineral systems (Kerrich et al ., ; Chen, ) include the following: (1) the ores were formed at convergent plate margins in accretionary and collisional orogens; (2) the locations of the ore bodies are controlled by shear zones or faults; (3) the ore fluids are generally of low salinity and CO 2 ‐rich with variable CH 4 ; (4) the mineralization temperature and depth shows a wide range from 220 to 500 °C and from 5 to 18 km, respectively; (5) the mineralization is coeval with a major orogeny. Many orogenic‐type mineral systems have been identified based on these characters, such as the Tieluping Ag deposit (Chen et al ., ), Weishancheng Ag–Au belt (Zhang et al ., ), Lengshuibeigou Pb–Zn deposit (Qi et al ., ), Wangpingxigou Pb–Zn deposit (Yao et al ., ), Yindonggou Ag–Au–Pb–Zn deposit (Yue et al ., ) and Dahu Au–Mo deposit (Li et al ., ; Ni et al ., , ) in the Qinling Orogen; the Bainaimiao Cu–Au deposit (Li et al ., ) and Huogeqi Cu–Pb–Zn–Fe deposit (Zhong et al ., ) in the eastern part of the Central Asian Orogenic Belt; the Sarekuobu Au deposit (Zhang et al ., ), Tiemurt Pb–Zn deposit (Zhang et al ., ), Wulasigou Cu deposit (Zheng et al ., ), Qiaxia Cu deposit (Zheng et al ., ) and Mengku Fe deposit (Wan et al ., ) in the Altay Orogen in NW China; and the W–Mo deposit in the Caledon Orogen in Norway (Larsen and Stein, ).…”