芬兰北部金矿床产出环境、地质特征和成矿作用

芬兰北部的金矿床数量众多,大多数金矿床(点)产出于古元古界中央拉普兰绿岩带(CLGB)和库萨莫—帕拉波加片岩带内,主要分为3种类型:造山型金矿、铁氧化物铜-金(IOCG型)矿床及砂金矿。其中造山型金矿绝大部分分布于中央拉普兰绿岩带中部及库萨默地区和帕拉波加地区,最常见的矿石矿物为黄铁矿、毒砂、黄铜矿和磁黄铁矿,其次为方铅矿、闪锌矿、黝铜矿等。围岩蚀变包括钠长石化、绢云母化、黑云母化、碳酸盐化及绿泥石化。造山型金矿床主要控制因素包括构造、岩性和造山期区域变质。IOCG型矿床主要分布在CLGB的西部克拉瑞地区,容矿围岩是钠长石-直闪石石棉型岩石,矿石中富含Fe-Cu-Au±Ag、Bi、Ba、Co、Mo、Sb、Se、Te、Th、U和轻稀土元素。围岩蚀变强烈,并且有明显的分带现象。IOCG型金矿床的形成受岩浆热液活动和构造的影响较大。砂金矿床包括古砂金矿床和现代砂金矿床,主要分布在CLGB东北部。芬兰北部金矿床的研究对北极圈及邻区的找矿勘查工作具有重要意义,也为中国胶东半岛、华北克拉通北缘、小秦岭和秦岭地区及新疆北部地区进一步金矿勘查提供参考。

Geological setting, geological characteristics and mineralization of gold deposits in northern Finland

Gold deposits in northern Finland occur like numerous stars in Paleoproterozoic Central Lapland greenbelt (CLGB) and Kuusamo-Perapohjaschist greenbelt. Gold deposits in northern Finland can be divided into three categories: orogenic gold deposits, iron oxide Cu-Au deposits (IOCG) and placer gold deposits. Most of orogenic gold deposits are distributed mainly over CLGB and Kuusamo-Perapohjaschist greenbelt. The most common ore minerals of orogenic gold deposits are pyrite, arsenopyrite, chalcopyrite and pyrrhotite, whereas the accessory minerals are mainly galena, sphalerite and tetrahedrite. The wall rock alterations of orogenic gold deposits mainly include albitization, sericitization, biotitization, carbonatization and, to some extent, chloritization. The orogenic gold deposits have many similarities in mineralization, and main controlling factors include tectonics, lithology and orogenic metamorphism. The IOCG deposits in northern Finland are distributed mainly in the Clariant area of west CLGB, and the wall rocks are albite-anthophyllite rocks with strong wall rock alteration and obvious zonation. Elements concentrated in the ore are Ag, Au, Bi, Co, Cu, Fe, Mo, LREE, S, Se, and Te. The mineralization of IOCG deposits was closely related to magmatic hydrothermal activity and structure. Placer gold deposits in northern Finland comprise paleoplacer deposits and placer deposits which are mainly distributed in the northeast of CLGB.Gold deposits in northern Finland are of great significance for the mineral exploration in Arctic Circle and adjacent areas; on the other hand, the study of ore deposits in northern Finland is of reference value for the gold exporation work in such areas as the Jiaodong Peninsula, the northern margin of North China Craton, Xiao Qinling and Qinling area and northern Xinjiang in China.