Identification of Two Types of Metallogenic Fluids in the Ultra-Large Huize Pb–Zn Deposit, SW China

Abstract

This work investigates the ultra-large Huize Pb-Zn deposit, based on the results of preceding studies and detailed field geological surveys. The existing findings were reorganized and reinterpreted and supplemented with C-H-O isotopic measurements, which resulted in the identification of two different metallogenic fluids: a high temperature, low salinity, and acidic Fluid A, which originates from deep-seated fluids and is enriched in lighter C and O isotopes (−3‰ < 13 C‰ < −4‰; 10‰ < 18 O‰ < 17‰; −92‰ < D‰ < −50‰), and a low temperature, high salinity Fluid B, which is a subsurface brine formed by atmospheric precipitation. Fluid B is characterized by heavier C-O-H isotopic compositions (−2‰ < 13 C‰ < 1‰; 2‰ < 18 O‰ < 24‰; −66‰ < D‰ < −43‰) than Fluid A and cycles continuously within the strata. We hypothesize that the Huize Pb-Zn deposit is the result of large-scale fluid migration from deep regions of the crust. These upward-moving fluids extracted metallic elements from carbonate strata of various ages, forming a metal-rich metallogenic fluid (Fluid A). After higher-grade ores were precipitated from the fluid following decompression boiling, it then mixed with Fluid B and continued to precipitate sulfides.

Ore genesis of the Qilinchang Carboniferous carbonate Pb-Zn Mississippi Valley-type deposit, Western Yangtze Platform, Southwest China: Constraints from mineralogy, C-O-S-Pb isotope systematics, and REE studies

“…This is an indication that the ore-forming fluids were related to water/rock (W/R) interaction between the mantle and/or metamorphic fluids and carbonates. The values obtained from this study are consistent with previous data of host rock and miarolitic calcites (Huang et al, 2003;Zhang et al, 2005b;Han et al, 2007;Zhang et al, 2017) but different from the primary ore calcites. The correlation between δ 1 3…”

“…values (+19.24 to 26.83‰, average of 13.28‰) of syn-ore calcite extracts from the Qilinchang deposit are significantly greater than that of the mantle-derived rocks (+6.0 to +10.0‰; Taylor et al, 1967), but most values are analogous to the marine carbonate rocks (+20.0 to +30.0‰; Veizer and Hoefs, 1976) and lesser than the sedimentary organic matter (+24.0 to +35.0‰; Liu and Liu, 1997 (Zheng and Chen, 2000) are lower than those of sedimentary organic matters, marine carbonate rocks, but are analogous to those of mantle or metamorphic fluids having documented values of +2 to + 25‰ (Hoefs, 2009). Inference can be made that the mantle and organic matters did not contribute a substantive amount of carbon to the hydrothermal fluids and suggested that the carbon in the fluids was probably injected by the carbonate host rocks of the Carboniferous Baizuo Formation (Han et al, 2007;Zhang et al, 2017). Also, based on (Fig.…”

“…Also, Huang et al (2003), suggested using carbon and oxygen isotope of calcite and ore-hosting strata, theorized that the ore-forming fluids represent crustal-mantle fluid mixing. Latterly, Zhang et al (2017), identified dual types of metallogenic fluid using C-H-O isotopic measurements of carbonates and proposed that the ore-forming fluids are formed because of capacious fluid migration from deep regions of the crust. In all of these, the origins of the metallogenic fluids of the Huize deposit remain controversial despite the large volume of detailed studies that have been carried out in this region.…”

Geology and geochemistry of Zn-Pb(-Ge-Ag) deposits in the Sichuan-Yunnan-Guizhou Triangle area, China: A review and a new type

“…The gas phase components contain CO 2 + CH 4 + N 2 (Han et al, 2007a;Han et al, 2016;Zhang et al, 2017a). The results show that gas-liquid differentiation occurs during the oreforming process.…”

“…Hydrogen and oxygen isotopes can effectively identify the ore-forming fluid source (Huang et al, 2019b). Zhang et al (2017a) identified the two different metallogenic fluids by C-H-O isotope: a high temperature, low salinity, and acidic Fluid A, which originates from deep-seated fluids and is enriched in lighter C -O-H isotopes (−3‰ < δ 13 C ‰ < −4‰; 10‰ < δ 18 O‰ <17‰; −92‰ < δD‰ < −50‰), and a low temperature, high salinity Fluid B, which is a subsurface brine formed by atmospheric precipitation. Fluid B is characterized by heavier C-O-H isotopic compositions (−2‰ < δ 13 C‰ < 1‰; 2‰ < δ 18 O‰ < 24‰; −66‰ < δD‰ < −43‰) than Fluid A and cycles continuously within the strata.…”