云南格咱岛弧成矿带铜厂沟铜钼多金属矿床地球化学特征及地质意义

Geochemical characteristics and geological significance of Tongchanggou Cu-Mo polymetallic deposit in Gezan Island Arc of Yunnan

通过对铜厂沟矿区花岗闪长斑岩地球化学元素及矿区地质特征分析研究,区内的花岗闪长斑岩SiO2含量为66.32%~69.60%,Al2O3含量为14.05%~15.55%,MgO含量为1.19%~1.39%,铝饱和指数A/CNK值为0.88~1.05,属于准铝质-弱过铝质,全碱（K2O＋Na2O）含量为6.97%~9.11%,相比中酸性岩石碱度较高。岩石中的轻稀土比较富集（LREE/HREE=13.56~16.94）,轻重稀土分馏明显（LaN/YbN=25.97~36.73）,δEu（0.87~1.01）、δCe（0.89~0.94）均无明显的异常。富集大离子亲石元素（LILE,Rb、K、La、Ba）,相对亏损高场强元素（HFSE,Nb、Hf、Ti）,指示岩石是与板块俯冲相关的造山花岗岩系列。矿床中斑岩型矿体与岩浆侵入成矿作用关系密切,而矽卡岩型-热液脉型矿体与岩浆热液上侵充填-接触交代作用相关,矿区深部工程已揭露出深部存在隐伏花岗闪长斑岩体,找矿潜力巨大。

This paper analyzed the geochemical elements of granodiorite-porphyry in Tongchanggou mining area and the geological characteristics of the mining area.The results revealed the contents of granodiorite-porphyry in this area,which include SiO2（66.32%-69.60%）,Al2O3（14.05%-15.55%）,and MgO（1.19%-1.39%）.The A/CNK value ranges from 0.88-1.05,and it indicates that the granodiorite-porphyry is a kind of metaluminous to weakly peraluminous rock.With K2O＋Na2O content accounting for 6.97%-9.11%,the alkalinity of the rocks is higher than that of intermediate-acidic rocks.The rock is LREE enriched（LREE/HREE=13.56-16.94）and is characterized by obvious fractionation between light and heavy rare earth elements（LaN/YbN=25.97-36.73）.The values ofδEu（0.87-1.01）andδCe（0.89-0.94）indicate no significant anomalies.The rock is characterized by LILE（short for large ion lithophile element,including Rb,K,La,Ba）enrichment and HFSE（high field strength element,including Nb,Hf,Ti）depletion,which suggests that it is a kind of orogenic granite series related to the plate subduction.The porphyry orebodies in the deposit are closely related to the mineralization after magmatic intrusion,and skarn type and hydrothermal vein type orebodies are correlated with upward intrusion and filling of magmatic hydrothermal fluid and contact metasomatism.The projects at the deep part of the mining area have revealed the existence of concealed granodiorite-porphyry rock bodies at depth and the deposit has great prospecting potential.