黑龙江三十二站金矿床地质地球化学特征及构造环境

Geological and geochemical characteristics and tectonic settings of Sanshi'erzhan gold deposit,Heilongjiang Province

三十二站金矿床位于黑龙江省漠河县西北部额尔古纳隆起北东端上黑龙江断陷盆地边缘。矿体赋存于二十二站组中粒砂岩-泥质岩中,岩浆岩以闪长玢岩、花岗岩为主,与成矿关系密切。矿区内共发现9条矿化蚀变带,10条金矿体,矿体长600～1 290 m,宽1.86～5.70 m,金品位(1.31～2.44)×10-6。构造环境判别图解表明,区内花岗岩为造山类花岗岩,具与俯冲带有关的陆缘环境或岛弧构造环境特征。闪长玢岩具有岛弧和活动大陆边缘弧岩浆岩的特征;二十二站组砂岩具有大陆岛弧的构造环境特征。结合区域地质演化特征,认为在中侏罗世末—晚侏罗世早期,古太平洋板块斜向俯冲于西伯利亚板块下部,二十二站组砂岩中的金元素初次富集,并为成矿提供有利空间。晚侏罗世后期中-酸性岩浆侵入,流体与地幔相互作用,导致地幔金属硫化物被氧化分解带至地表浅部,最后在成矿有利部位成矿。

Sanshier＇zhan gold deposit is located in the northeastern Erguna rising part on the edge of upper Heilongjiang Basin of fault subsidence. The gold ores are yielded in medium-grained sandstone in Ershi＇erzhan For- mation. Magmatic rocks are mainly with diorite and granite which is closely related to mineralization. Nine altera- tion zones and ten gold ore bodies were discovered within the mining area. The ore bodies ranges 600 - 1 290 m long by 1.86-5.70 m wide. The gold grade is （1.31 -2.44） x 10-6. According to tectonic environment dis- crimination diagrams, granite in this mining area is orogenic granite, showing some geochemical characteristics of that from island arc or continental margin environment related to the subduetion zone. Diorite shows the characteris- tics of that from island arc or active continental margin environment. Sandstone in Ershierzhan Formation shows the characteristics of that from continental island arc. At the end of Middle Jurassic-early Late Jurassic, the Pacific Plate had obliquely subducted the lower part of the Siberian Plate, which leads the gold element started enrichment in Ershierzhan Formation for the first time, and provided a favorable space for mineralization. In late Late Jurassic,magmatic fluid interacted with the mantle and caused the mantle metal sulfide oxidation decomposition and brought to the superficial ground. It finally enriched and mineralized in favorable metallogenic parts.