Study on the occurrence,distribution and enrichment of cobalt in Anqing copper-iron deposit,Anhui Province
The Middle-Lower Yangtze River Metallogenic Belt is one of the most important ones in eastern China,which is characterized by widespread skarn-type copper-iron deposits with associated cobalt(Co)resources.However,the occurrence,distribution and enrichment patterns of the Co element in skarn-type copper-iron deposits within this metallogenic belt have not been systematically studied.This study focuses on the Anqing copper deposit,a skarn-type copper-iron type one,and carries out a systematic sampling,microscopic observations,scanning electron microscopic and whole-rock chemical analyses,LA-ICP MS trace element and TIMA testing.The preliminary estimation of the associated Co resources in the deposit is approximately 8769 tons,indicating a medium-scale deposit with significant potential for comprehensive utilization.The average Co content of the associated minerals is 166 ×10-6.It was found that the Co content in copper ores is significantly higher than those in iron ores,especially in copper-bearing pyrrhotite ores,which exhibit the highest Co enrichment.The calculated ore composition shows that the magnetite,pyrite,magnetite and chalcopyrite account for 45.1％,52.8％,0.5％and 1.6％of the total Co content,respectively.Furthermore,there is a strong positive correlation between the Co content in different types of mineralized altered rocks and the total content of pyrrhotite and pyrite.Co is mainly present in pyrite and pyrrhotite as solid solution and exsolution.The Co content in pyrite varies significantly,ranging from 258 × 10-6 to 25920 × 10-6 in the early sulfide stage(Py1)and from 0.3 × 10-6 to 594 × 10-6 in the late sulfide stage(Py2).The Co content in pyrrhotite shows a smaller range,mainly concentrated in between 311 ×10-6 and 1181 ×10-6.Co is primarily enriched in the early quartz sulfide stage,while there is no significant enrichment in the late quartz sulfide stage.The wide range of Co element variation(85 × 10-6～430 × 10-6)in copper-bearing magnetite ores is due to the uneven distribution of pyrite and pyrrhotite in the ore,as well as the highly heterogeneous Co content in pyrite.Based on previous studies,this work suggests that the cooling and dilution of ore-forming fluids caused by the infiltration of atmospheric precipitation may be the main factor for the precipitation and enrichment of Co in pyrite and pyrrhotite in the Anqing copper deposit.
Critical metal CoOccurrence stateEnrichment ruleAnqing copper depositThe Middle-Lower Yangtze River Valley Metallogenic Belt
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