火山岩型金矿的地质特征及勘查准则

通过对全球典型的巨型火山岩型金矿的研究分析,总结了火山岩型金矿的地质特征:这类金矿产出的大的构造背景多为活动的大陆边缘和岛弧,其成矿时代主要集中在中生代—新生代,容矿岩石主要为第三纪钙碱性喷出岩和浅成侵入岩,容矿构造主要为火山中心、破火山口、火山颈、角砾岩筒、火山穹窿、火山背斜、破碎带、张性裂隙带等各种构造,矿化特点为金和银共生在同一矿床,往往呈自然金或银金矿出现,有些矿床中含碲较多,矿化深度浅,上部为金和银,下部往往变成锌和铅。火山岩型金矿床与地热和温泉的活动密切相关,其围岩蚀变为绢云母化、硅化、碳酸岩化、泥化、黄铁矿化和钾化发育,原生晕分带总的趋势为Hg Sb As Ag Au(Mo、Pb、W)。提出了勘查火山岩型金矿床的选靶准则,指出中国东部地区基底具有前寒武纪矿源层的火山岩断陷盆地周边、深大断裂带上的幔源火山岩区或某些洋壳重熔形成的火山岩区找金潜力较大,尤其是中国西部的东、西准噶尔、西天山、东天山、北天山、新疆南天山、松潘—甘孜和"三江"构造 成矿带的东缘是找金最有潜力的地区。

GEOLOGICAL CHARACTERISTICS AND EXPLORATION CRITERIONS OF VOLCANOGENIC GOLD DEPOSIT

Volcanogenic gold deposit is an important type of gold deposits. The geological characteristics of volcanogenic gold deposits are summarized by analysing some typically large gold deposits : the tectonic settings are active continental margin and island arc; the mineralization period are mostly Mesozoic-Cenozoic; the host rocks are mainly calc-alkali extrusive rock and hypabyssal intrusive ; the host structures are volcanic center, caldera, neck, breccia pipe, zone of fractures,etc.; gold and silver minerals occur in same deposit,and some gold deposits contain telluride; the depth of mineralization is shallow; the wall-rock alterations are sericitization,silication, carbonation, argillation, pyritization and potash-alteration; the zones of primary halo are Hg-Sb-As-Ag-Au ( Mo,Pb,W); the deposit is related to geotherm and thermal spring.The authors put forward exploration criterions of volcanogenic gold deposit,and suggest that the volcano-fault basin with Pre-Cambrian source bed and mantle-derived igneous rock province above deep-fracture zones in east of China, especially in western China, Zhunger,Tianshan,Songpan-Ganzi and the east margin of "Three Rivers" tectono-metallogenic belt are the most potential gold exploration regions.