北衙金矿区作为藏东-川滇西-滇东南喜马拉雅期富碱斑岩带的一部分,发育有3期成分不同的碱性斑岩,并经历了多期成矿作用。北衙金矿有3种成因不同的矿床:①与碱性斑岩有关的铜金多金属矿,包括与石英钠长斑岩和石英正长斑岩有关的斑岩型铜金矿床和矽卡岩型多金属矿床;②与辉长-玄武岩浆有关的铁金矿床,包括熔浆型铁金矿床和喷流沉积型多金属矿床,后者又有洞穴和湖相沉积环境之分;及③古砂矿,有古风化壳型砂矿、河湖相古砂矿和洞穴沉积古砂矿。北衙矿区复杂多样、多期叠加活动的岩浆与成矿作用,造就了矿区大规模的成矿作用。
The Beiya ore district, as a part of the Cenozoic alkali-rich porphyry belt in the eastern Tibet-western Yun- nan-southeastern Yunnan area, possesses three types of alkaline porphyries formed at three stages, and has experienced repeated mineralization. There are three genetic types of mineral deposits in the Beiya ore district: ① Cu-Au polymetallic deposits related to alkaline porphyries, comprising porphyritic Cu-Au deposits and polymetal- lie skarn deposits related to quartz-albite porphyry and quartz-K-feldspar porphyry; ② Fe-Au deposits related to gabbro or basalt magma, consisting of magmatic Fe-Au devasits and sedimentary polymetallic deposits formed in caves and lakes; and ③ palaeo-placers formed at the weathering surface, in lakes and in karsts. Complex and superimposed magmatism and hydrothermal processes resulted in the formation of a superlarge gold and polymetal-lieore district in the Beiya area.