湖南省长平断裂南段盐田桥矿床钴的赋存状态、形成时代及地质意义OA

The Changsha-Pingjiang fault(Changping fault)is a major NE-trending deep-seated fault,its northern seg-ment constitutes an important hydrothermal Co-polymetallic metallogenic belt in Hunan Province,however,hy-drothermal Co mineralization has not been previously reported in its southern segment.This paper reports,for the first time,the identification of cobalt mineralization in the Yantianqiao deposit located within the southern seg-ment of this fault.To further elucidate the metallogenic age,occurrence state,and enrichment mechanisms of co-balt,detailed field geological investigations were carried out and combined with mineral TIMA mapping,EPMA mapping and quantitative analysis,monazite U-Pb dating,and in-situ sulfur isotope analysis of pyrite.The results reveal that the mineralization process at Yantianqiao can be divided into four stages:breccia-sulfide stage(Ⅰ),quartz vein-magnetite stage(Ⅱ),quartz vein-chalcopyrite stage(Ⅲ),and barite vein-pyrite stage(Ⅳ).Three dis-tinct types of pyrite(Py4a,Py4b and Py4c)were identified in stage Ⅳ,with Py4c being the primary cobalt-bear-ing mineral throughout the deposit.Monazite coexisting with Py4c yielded a U-Pb age of(149.0±0.8)Ma(MSWD=1.8).Cobalt-rich pyrite(Py4c)exhibits a significant positive correlation between Co,Ni and As contents,and a negative correlation between Co,Ni and Fe,S contents.The δ34S values of pyrite from various stages in the de-posit predominantly range from-13.5‰ to-7.8‰.The comprehensive analysis indicates that:the primary ore-forming material at Yantianqiao was derived mainly from the Neoproterozoic Lengjiaxi Group,with Co mineral-ization occurring during the Late Jurassic;the cobalt-bearing mineral(Py4c)formed via dissolution and reprecipi-tation during the replacement of Py4a by Py4b,and Co and Ni primarily entered the pyrite lattice through isomor-phic substitution for Fe;the Co mineralization at Yantianqiao exhibits distinct differences from Co-polymetallic deposits in the northern segment of the Changping Fault in terms of formation age,mineralization stages,and mineral assemblages.The Changping Fault shows promising potential for Co exploration,and cobalt mineraliza-tion around the Hengyang Basin also warrants attention.