Sources of ore‐forming material for Pb‐Zn deposits in the Sichuan‐Yunnan‐Guizhou triangle area: Multiple constraints from C‐H‐O‐S‐Pb‐Sr isotopic compositions

Abstract

The Sichuan‐Yunnan‐Guizhou Pb‐Zn triangle area is located in the western margin of the Yangtze Block and comprises more than 400 ore deposits or prospects. This triangular area contains 200 million tons of ores at average grades of 5 wt.% Pb and 10 wt.% Zn. The Pb‐Zn ore bodies are mainly distributed as stratoid and vein types within the Neoproterozoic to Permian carbonate rocks, which are typical epigenetic Pb‐Zn mineralizations. Previous studies have mainly focused on individual deposits. In this study, the compositions of C‐H‐O‐S‐Pb‐Sr isotopes of approximately 20 typical deposits are summarized and studied in detail to reveal the source of the ore‐forming material. δ13CPDB ‐ δ18OSMOW isotopic compositions of the hydrothermal calcite, dolomite, and fluid inclusions show that CO2 in the ore‐forming fluids could have been derived from marine carbonate with subordinate incorporation of organic matter. In addition, δDH2O ‐ δ18OH2O isotopic studies also indicate the multisource features of the ore‐forming fluids, for example, meteoric water and metamorphic water; meanwhile, some deposits are related to organic fluids. The δ34S values of most sulphide minerals range from +9.0‰ to +28.6‰, similar to late Neoproterozoic to Permian seawater sulphate (+8.0‰ to +38.7‰). This similarity suggests that the reduced sulphur in sulphides could have been mainly derived from the thermochemical sulphate reduction of the host strata seawater sulphate. In addition, thermal decomposition of sulphur‐bearing organic matter could have provided some of the reduced sulphur for mineralization in some Pb‐Zn deposits. The Pb isotopic compositions of the sulphides from most deposits are totally homogeneous and located between the crustal Pb and orogenic Pb evolution curves. Comparing these deposits with the regional basement rocks, sedimentary strata, and Permian Emeishan basalts, we propose that the metals for Pb‐Zn mineralization were mainly derived from the basement rocks and sedimentary country rocks. For some deposits (e.g., Jinshachang) with highly radiogenic Pb isotopic compositions, their Pb mainly originated from Precambrian basement carbonaceous slate and Lower Cambrian shales. The (87Sr/86Sr)t ratios of sphalerite, hydrothermal calcite, and fluorite range from 0.7099 to 0.7469, higher than those of the regional sediments and the Emeishan basalts, but lower than those of the Proterozoic basement rocks. Such features also indicate the mixing source for Sr in sulphides and ore‐forming fluids. The comprehensive study of multiple C‐H‐O‐S‐Pb‐Sr isotopes from typical deposits suggests mixed sources for the ore‐forming fluids and materials in this triangular area.

The giant Upper Yangtze Pb–Zn province in SW China: Reviews, new advances and a new genetic model

“…Wang (1993), Zheng (1994), Hu (1999), Zhang et al (1998Zhang et al ( , 2016, Liu and Lin (1999), Fu (2004), Tang et al (2012), Zhou et al (2013aZhou et al ( , 2013bZhou et al ( , 2013cZhou et al ( , 2014aZhou et al ( , 2014b, Li et al (2015), Jin et al (2015, Xiang et al (2015), Bao et al, 2017;Chen et al (2017), and Zeng et al (2017). The sources of data are the same to those in Figure 32, other data are sourced from Faure (1977), Cong (1988), Li and Qin (1988), Chen and Ran (1992) and Kong et al, 2017. from extension to compression, and then to extension again (Carter et al, 2001;Reid et al, 2007;Lepvrier et al, 2008;Qiu et al, 2016;Hu et al, 2017aHu et al, , 2017bZhou et al, 2018b), causing these initial fluids flowed through or interacted with Proterozoic to Paleozoic multiple geological units, and then forming metal-rich fluids.…”

“…The origin of these Pb-Zn deposits in the Upper Yangtze metallogenic province has been dealt with in literature (e.g. Zhou et al, 2013a;Li et al, 2015;Zhu et al, 2016a;Kong et al, 2017). However, most of these studies only focused on individual deposits and concerned with ore deposit geology, trace elements, isotopes, geochronology or fluid inclusions.…”

Metallogenesis and Formation of the Maliping Pb-Zn Deposit in Northeastern Yunnan: Constraints from H-O Isotopes, Fluid Inclusions, and Trace Elements

“…The sphalerites of the Huize, Lehong, and Maliping deposits in northeastern Yunnan have similar REE distribution patterns and ΣREE contents, indicating similar sources of ore-forming materials. The ore-forming materials for the Huize Pb-Zn deposit were mainly derived from basement rocks (Kunyang Group) and cover sedimentary rocks, whereas the Emeishan basalt may provide a small amount of material for mineralization [62]. The ore-forming materials for the Lehong Pb-Zn deposit were mainly derived from Proterozoic Eon basement rocks (Kunyang Group), with a possible contribution from sedimentary strata [9,62].…”

Metallogenic Age and Ore‐forming Material Sources of the Dahongshan Fe‐Cu Deposit, Yunnan Province: Insights from Molybdenite Re‐Os Dating and H‐O‐S‐Pb Isotopes

“…The base map was modified from Kong et al (2018). Data for the Lala deposit were obtained from Yang et al (1988), Chen and Ran (1992), Sun et al (2006) and Huang (2019).…”