智利科皮亚波GV地区侵入岩地球化学及年代学研究

A Study on the Geochemistry and Geochronology of the Intrusive Rocks in Copiapó GV Area,Chile

智利北中部科皮亚波GV地区位于中生代铁氧化物铜金(IOCG)矿床与斑岩铜矿过渡带。侵入岩体主要为辉长闪长岩、闪长岩、闪长斑岩、黑云母花岗岩、斑状花岗岩和二长岩。岩石地球化学特征说明该侵入岩体属于钙碱性、I型或磁铁矿系列,来源于深部上地幔。推测这些岩浆岩岩石组合形成于洋壳俯冲带,局部扩张与挤压转换导致弧后盆地萎缩封闭并快速抬升。岩浆侵入具有多期次活动,形成了多期次热液活动中心,并发育面型与脉带型蚀变矿化分带,地表具有寻找大型IOCG矿床前景。地表泥化-绿泥石-多孔状硅化网脉和含金银多金属铁锰碳酸盐化网脉发育,含金银多金属网脉状-带状和面型蚀变区揭示地表有浅成低温热液型金银多金属矿床;深部具有寻找隐伏斑岩型铜金矿床前景。今后需在该区加强蚀变矿化分带规律研究,进行深部找矿预测。

The Copiapó GV area of northern-central Chile is situated in the transition zone between a Mesozoic iron oxide copper-gold（IOCG） deposit and a porphyry copper deposit.The intrusive rocks mainly consist of calc-alkaline,medium to coarse grained gabbro diorite,diorite,diorite porphyry,biotite granite,porphyritic granite and monzonite.These rocks are classified into the category of calc-alkaline,I-type and magnetite types,which is derived from the upper mantle.The assemblage of the intrusive rocks is interpreted to be formed at the subduction zone of oceanic crust during conversion from partially expansion to extrusion.As a consequence,the Mesozoic back-arc basin closed up and uplifted rapidly.The magma intruded mainly in the period of Late Cretaceous-Paleocene（about 65-54 Ma）.The magmatic activities of different periods created a number of hydrothermal centeres and developed horizonal alteration zones and vein-type alteration-mineralization zones.On surface argilization-chlorite alteration,porous and silicified stockwork,and Au-Ag bearing Fe-Mn carbonate stockwork well developed.The widely extensive alteration zones contain gold,silver poly-metallic veins,which may indicate that the area could develop some epithermal Au-Ag poly-metallic deposits.These phenomena may present the potential of occurrence of IOCG mineralization or porphyry copper-gold mineralisation in deep area.Further study of alteration and mineralization should be strengthen,which will create a guideline of exploration for the deep-buried deposits in the future.