Abstract
The Longtang Pb-Zn deposit occurs in the Upper Sinian Guanyinyan Formation. The host rocks include sandy shale, cherty limestone and dolomitic limestone. The deposit is a typical one of thallogen origin.
The mineral assemblage in the ore is made up of sphalerite, galena, pyrite, enargite, tennantite, seligmannite, asphalt, etc. The ore-forming process is possessed of multiepisode and multi-stage characters. Generally, sphalerites exhibit algal stromatolitic, bacterial and algal colloidal textures, providing evidence for the direct involvement of algae and bacteria in mineralization of ore-forming elements during sedimentary diagenesis. This is the first transmigration of ore-forming elements. However, pyrite embracing bacteria and galena replacing/filling trichomes are typical organic textures, which are related to organic carbon and bitumen that can adsorb or reduce ore-forming elements. This is an indirect process of organic mineralization, i.e., the second transmigration of ore-forming elements. δ34S values are all greater than 5%., indicating the dominance of the heavy sulfur isotopes. The ore-forming temperature deduced from fluid inclusions ranges from 100°C to 150°C±. All this goes to show that the Longtang Pb-Zn deposit is of thallogen origin.
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References
Shuai Dequan, 1988, Biological fabrics of ore minerals: Chengdu, Sichuan University Press, 155p.(in Chinese)
Wei Muchao, 1990, Micropaleontology: Beijing, Geological Press, 115p. (in Chinese)
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Dequan, S., Shouting, Z. & Xiaoqiang, H. Algal-bacterial fabrics of ores and their genetic implications in the longtang lead-zinc deposit at Yanbian, Sichuan. Chin. J. of Geochem. 14, 220–230 (1995). https://doi.org/10.1007/BF02842045
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DOI: https://doi.org/10.1007/BF02842045