安徽金寨县沙坪沟钼矿成矿岩体矿物学特征及其成岩成矿意义

Mineralogy of ore-hosting intrusions of the Shapinggou molybdenum deposit in Jinzhai County of Anhui Province and its implications for petrogenesis and mineralization

安徽金寨县沙坪沟钼矿成矿岩体主要包括二长花岗斑岩、正长斑岩及花岗斑岩,主要矿物组成为石英、钾长石、斜长石、黑云母.本文利用电子探针技术对主要矿物的矿物学特征进行了研究,结果表明,岩石中斜长石为钠长石;钾长石以条纹长石为主;黑云母属于镁质黑云母,富Mg、Al、K,贫Ca,MF值变化于0.65～0.72之间.黑云母化学成分显示本区岩体为Ⅰ型花岗岩,属于造山带钙碱性花岗岩类,其成岩物质具壳幔混合的特点.黑云母矿物温压计计算结果显示,岩体固结温度约500～580℃,氧逸度变化范围是10^-14～10^-15.8,其含铁指数对寻找钼矿具较好的指示意义.

The Shapinggou molybdenum deposit in Jinzhai County of Anhui Province is situated in the QinlingDabie orogenic belt,with mineralization substantially hosted in monzonitic granite porphyry,syenite porphyry and granite porphyry.Microscopic observation shows that the rocks mainly consist of plagioclase,potassium feldspar,biotite and quartz.With these minerals as the study objects,the authors used electron microprobe technology to analyze their mineralogical characteristics,and the results show that,in the rocks,the plagioclase is albite,K-feldspar is mainly perthite,and biotite is Mg-biotite rich in Mg,Al and K and depleted in Ca,with MF changing from 0.65 to 0.72.Chemical composition of biotite suggests that the intrusion is Ⅰ-type granite,which is a sort of calc-alkali orogenic granite,materially sourced from both the crust and the mantle.Biotite geothermometer and geobarometer imply that the intrusion was consolidated at 500～ 580℃,with the oxygen fugacity ranging from 10^-14 to 10^-1s.8 and the iron index being a good indicator for molybdenum mineralization.