Lianqiang Zhu , Zezhang Song , Guangdi Liu , Peng Cheng , Haifeng Gai , Hui Tian
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引用次数: 0
Abstract
Hydrocarbon fluids play crucial roles in Pb–Zn mineralization, yet the contribution of metals from hydrocarbon fluids remains a key research topic. Based on petrographic analyses of sulfide minerals and solid bitumen, combined with LA-ICP-MS analysis of sphalerite, this study investigates hydrocarbon-phase evolution during metal mineralization and the composition of trace elements and rare earth elements (REEs) in sphalerite formed in various hydrocarbon phases. The study focuses on the classical lead-zinc mineralization belt of the Yangtze Block, South China. By comparing the composition of trace elements and REEs in solid bitumen and sphalerite across different hydrocarbon phases, the hydrocarbon contribution to metal mineralization is assessed. The results indicate that hydrothermal activity induced oil cracking in the reservoir, leading to the formation of two distinct types of sphalerites before and after oil cracking, reflecting environments with and without crude oil. Sphalerites formed before and after oil cracking exhibit formation temperatures of 132–252 °C and 88–202 °C, respectively. Both sphalerites share identical ore-forming fluid sources with similar sulfur and oxygen fugacity and the weak difference in their trace element compositions was caused by the decreasing fluid temperature, suggesting that crude oil did not significantly contribute to ore-forming metals. Moreover, the compositions of trace elements and REEs in both sphalerites differ from those of solid bitumen from oil cracking, further supporting that the metals for mineralization were not from crude oil. Instead, hydrothermal fluids induced rapid oil cracking, causing metals like Pb and Zn in crude oil to precipitate with solid bitumen without mineralization. This study provides direct evidence that metals transported by hydrocarbons precipitate with solid bitumen during oil cracking and do not contribute to Pb–Zn mineralization in medium-to high-temperature hydrothermal systems, disproving previous assumption that inferred metal involvement in mineralization solely based on high metal concentrations in hydrocarbon fluids.
期刊介绍：
Applied Geochemistry is an international journal devoted to publication of original research papers, rapid research communications and selected review papers in geochemistry and urban geochemistry which have some practical application to an aspect of human endeavour, such as the preservation of the environment, health, waste disposal and the search for resources. Papers on applications of inorganic, organic and isotope geochemistry and geochemical processes are therefore welcome provided they meet the main criterion. Spatial and temporal monitoring case studies are only of interest to our international readership if they present new ideas of broad application.
Topics covered include: (1) Environmental geochemistry (including natural and anthropogenic aspects, and protection and remediation strategies); (2) Hydrogeochemistry (surface and groundwater); (3) Medical (urban) geochemistry; (4) The search for energy resources (in particular unconventional oil and gas or emerging metal resources); (5) Energy exploitation (in particular geothermal energy and CCS); (6) Upgrading of energy and mineral resources where there is a direct geochemical application; and (7) Waste disposal, including nuclear waste disposal.
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