菲律宾北甘马仁省拉惹普(Larap)铁铜钼矿床地质特征及成因

Geological characteristics and genesis of iron-copper-molybdenum deposit in Larap of Camarines Norte,Philippines

拉惹普(Larap)铁、铜钼矿床产于菲律宾板块俯冲吕宋岛被动陆缘的岛弧造山带上,处于菲律宾中央走滑断裂带近旁。含矿层位于古近纪渐新世晚期蚀变安山岩、角砾岩和古新统的角岩、角岩化页岩的喷溢角度不整合面的追踪断裂带上。大面积的安山岩、角砾岩的褪色化和带状展布的灰绿色热液交代蚀变岩系,矿体产于蚀变带中,呈似层状、透镜状;铁矿体在上部层位,铜钼矿体在铁矿体下部,与贫磁铁矿相伴产出;铁矿体伴生铜、钼,铜钼矿体又伴生铁、金、银和钴等,矿石中的金属矿物以磁铁矿为主,其次有黄铁矿、黄铜矿、辉钼矿、磁黄铁矿、沥青铀矿和自然金等。元素组合除铁、铜、钼外,还有金、银、钴和铀等,与奥林匹克坝、Candelaria(智利)的氧化铁型(IOCG)铜金矿床类比,拉惹普矿床成因属于氧化铁型铜钼金矿床新类型。

Larap iron-copper-molybdenum deposit is formed in the island arc orogen of Luzon passive continental margin which is subducted by Philippine Plate,and located near Philippines central strike-slip fracture zone.The mineral-bearing layer is situated on tracing fracture zone of outpouring angular uncomformity between altered andesite and breccia in upper Oligocene and hornfel and hornfel shale in Paleogene.Large area of faded andesite and hornfel and zonal distributed grey-green hydrothermal fluid are metasomatized with altered rock series,the orebody is formed in such alteration zone with laminiplantation and lense shapes.Iron orebody is located in upper layer,while the copper-molybdenum ore body is located in lower layer of iron orebody together with lean magnetite.The iron orebody associates with copper and molybdenum,the copper-molybdenum body associates with iron,gold,silver,cobalt and others.Magnetite is the dominant metallic mineral in the ore,secondly are pyrite,chalcopyrite,molybdenite,pyrrhotite,uraninite,nature gold and so on.Besides iron,copper and molybdenum,other element combinations include gold,silver,cobalt and uranium.Compared with Olympic dam and Candelaria（Chile） iron oxide copper-gold deposits,Larap deposit belongs to a new type of iron oxide copper-molybdenum-gold deposit.