1. Mercury isotope constraints on the sources of metals in the Baiyangping Ag-Cu-Pb-Zn polymetallic deposits, SW China.
- Author
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Tang, Yongyong, Yin, Runsheng, Hu, Ruizhong, Sun, Guangyi, Zou, Zhichao, Zhou, Ting, and Bi, Xianwu
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MERCURY isotopes ,MERCURY ,HYDROTHERMAL deposits ,SEDIMENTARY rocks ,METALS ,MARINE sediments - Abstract
The genesis of the giant Ag-Cu-Pb-Zn polymetallic mineralization in the northern Lanping basin, Southwest China, remains controversial. To address the sources of metals, a systematic study on Hg isotope compositions was conducted for the Cu-dominated deposit at Baiyangping and the Pb-Zn-dominated deposits at Fulongchang and Liziping. The Cu deposit shows positive Δ
199 Hg signatures (0.14 ± 0.13‰), in contrast to the Δ199 Hg of the Pb-Zn deposits (− 0.09 ± 0.06‰). As positive Δ199 Hg values are commonly observed in marine sediments and the Lanping Triassic marine sedimentary rocks show exclusively positive Δ199 Hg signals (0.03 ± 0.07‰), the Hg in Cu ores was mainly sourced from the Triassic strata. The negative Δ199 Hg signals observed in the Pb-Zn deposits, typical of terrestrial Hg, agree roughly with those of the Jurassic to Paleocene terrestrial sedimentary rocks (− 0.05 ± 0.08 ‰), indicating that the terrestrial strata provided the Hg in Pb-Zn ores. Compared to the source rocks, the Cu deposit shows isotopically lighter Hg enrichments (δ202 Hg = − 2.30 ± 0.35‰), possibly resulting from fractionations induced by Hg2+ sorption, organic complexation, and precipitation of Hg-bearing sulfides. The Pb-Zn deposits show comparable or slightly heavier δ202 Hg (− 0.56 ± 0.48‰); moreover, δ202 Hg values of late-stage sulfides are higher than early-stage δ202 Hg values, suggesting that the δ202 Hg variation was primarily caused by sulfide precipitation. Thus, Hg isotope data indicate that separate hydrothermal events resulted in Cu and Pb-Zn mineralization. More importantly, this study reveals the great potential of Hg isotopes to discriminate sedimentary sources of metals for low-temperature hydrothermal deposits. [ABSTRACT FROM AUTHOR]- Published
- 2022
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