北衙金多金属矿床地质特征与成因

Geological Characteristics and Metallogenic Types of Beiya Gold-polymetallic Deposit, in Yunnan

详细讨论了北衙矿区的地质特征,通过对勘探资料的深入研究和野外观察,初步确定,北衙矿区存在两期岩浆活动,早期的石英正长斑岩、正长斑岩等近南北向分布,晚期的黑云正长斑岩、煌斑岩脉等呈近东西向展布。矿化主要与近南北向岩体关系密切。北衙地区存在五种矿床类型,即矽卡岩型铁金矿床,其形成时代相对较早,分布于万硐山矿段、马头湾矿段等地;斑岩-隐爆角砾岩筒型金铜矿床,分布于北衙矿区的西矿带的万硐山-红泥塘(观音箐一带,形成时代相对较晚,并叠加于早期的矽卡岩型矿床之上;裂隙-溶洞型铁金矿床,主要分布于北衙矿区的东矿带的笔架山一带,属强氧化高品位金矿石;砂岩型铁金矿床,分布于本区的三叠系下统腊美组(T1l)砂岩中,呈似层状产出,成矿潜力巨大;红土型金矿床,主要分布于北衙盆地浅表部位的丽江组(E2l)和第四系堆积物中,易采易选,可供利用。北衙地区下一步勘探和研究的主要矿床类型应是深部具有潜力的斑岩(隐爆角砾岩筒型金铜矿床和三叠系下统碎屑岩中产出的砂岩型铁金矿床。

The paper discusses in detail the geology of the Beiya gold-polymetallic deposit. Based on the comprehensive study of the exploration data from the Beiya mine, combined with the field observation to the region, it is confirmed that there exist two stages of magmatic activities in the Beiya region. The early magmatic rocks include quartz syenite porphyries, syenite porphyries, striking in near SN direction; the latter ones include biotite syenite porphyries, lamprophyres, striking in near EW direction. The mineralization is close to the early magmatic rocks striking in near SN. In Beiya, there exist five types of deposits, namely, the skarn-type iron-gold deposit, relatively early, distributed in the blocks Wandongshan and Matouwan; the porphyry-craptobrecciated type gold-copper deposit, relatively latter, distributed along the belt of Wandongshan-Hongnitang-Guanyinqing in the west belt of the Beiya region and superimposed over the early skarn type mineralisation; the fracture-karst cave type iron-gold deposit, mainly distributed in the belt of Bijiashan in the east of the Beiya region a kind of strongly oxidized ore with high grade of gold; the sandstone-type iron-gold deposit, distributed in the Lamei Formation of the Lower Triassic, occurred in the stratiform and with great potential; the laterite-type gold deposit occurred in the sandstone and conglomerate of the Lijinag Formation of the Oligocene and Quaternary in the Beiya basin, easy to mine and to refine. The major objectives of exploration and research for next step are the porphyry-craptobrecciated-type gold-copper deposit and the sandstone-type iron-gold deposit, with great potential, in the deep in Beiya.