碧口古岛弧带构造演化与成矿

TECTONIC EVOLUTION AND MINERALIZATION IN BIKOU ACCIENT ISLAND ARC EELT

通过论述中—晚元古代碧口火山岛弧岩浆建造（喷发、侵入）特征、成岩成矿时代、成矿作用类型，探讨了碧口地体古岛弧岩浆带构造演化与成矿作用类型和矿床成矿系列的关系。中—晚元古代碧口火山岛弧构造演化期，约为１０亿年。可以分为武陵期（１８００～１４００Ｍａ）、四堡期（１４００～１０００Ｍａ）和晋宁期（１０００～８００Ｍａ）。碧口地体经过这三个时期完成了从岩浆岛弧的形成与发展，到板块俯冲和碰撞造山的连续演化过程。武陵期是该区岛弧火山岩带的发育期，生成与蛇绿岩有关的铬铁矿、熔离硫化镍矿床及与细碧－角斑岩有关的块状硫化物矿床。四堡期，主要表现为中酸性深成岩体与钠质辉绿岩的侵入活动，生成岩浆热液及接触交代型铁、铜矿床。晋宁期为碧口地体与扬子板块强烈碰撞造山期，除了生成与中酸性岩浆活动有关矿床外，主要生成与韧性剪切、构造动力变质热液成矿作用有关的金、银矿床。

By the detailed description of features of the magmatic formation,the ages of diagenesis andmineralization,and the mineralizing types,the relationship between tectonic evolution of the ac-cient island arc magmatic belt in Bikou Terrain and the types and sequence of mineralization hasbeen profoundly discussed in this paper. The age of tectonic evolution has enlonged about1,000Ma,which canbedividedinto Wulingperiod(1, 800 1,400Ma),Sipuperiod(1,400 1,000Ma)and Jinning period(1,000 800Ma).Through the three periods,Bikou Terrain com-pleted the continuously evolutional process from the formation and development of magmatic is-land arc to plate subduction and orogenics. There are different rock assemblages,mineralization tectonism relations,and then the different deposit types and mineralizing sequence in every peri-od.Wuling period is the widespreadingly developing period of island arc volcanic rocks,in whichforms the chromite deposits and nickel sulfide deposits related to ophiolites,and massive sulfidedeposits related to spilite keratophyre sequence. of Sipu Period is characterized by the intrusionsof intermediate acid plutons and sodic diabase,and by the formation of magmatic hydrothermaltype and contact metasomatic type of iron and copper deposits.Jinning period is the time of strongcollision between Bikou Terrain and Yangzi plate,in which mainly forms the gold and silver de-posits related to dynam hydrothermal mineralization in ductile shear zone as well as forms thedeposits associated with intermediate acid magma activity.