吉林省白山市板庙子金矿区花岗斑岩黑云母成分特征及其成岩成矿意义

Compositional characteristics of biotite in the granitic porphyry from Banmiaozi Gold Deposit,Baishan City,Jilin Province and their diagenetic and metallogenic significance

板庙子金矿床是吉南老岭金多金属成矿带内的大型金矿床,矿区内地质条件优越,具有较好的成矿潜力。矿区内出露的花岗斑岩是与金成矿有关的侵入岩,其为成矿提供了热源和物源。通过对板庙子金矿区花岗斑岩黑云母进行电子探针分析及相关计算,结果表明:花岗斑岩黑云母具有高Si、富Mg、贫Fe等特征,镁质率较高,属于镁质黑云母;利用黑云母成分估算岩浆成岩温度为700℃~750℃、氧逸度为-12^-14、深度为5.0~6.5 km。黑云母成分揭示岩浆来源具有壳幔混源特征,花岗斑岩为与造山活动有关的Ⅰ型花岗岩;花岗斑岩有利于金矿床的形成,推测板庙子金矿床是与古太平洋板块俯冲有关的中、浅成造山型金矿床。

The Banmiaozi Gold Deposit is a large gold deposit in the Laoling gold polymetallic metallogenic belt in south Jilin.The geological conditions in the district are favorable and the metallogenic potentials are great.The granitic porphyry intrusions exposed in the district are related to gold mineralization and provide heat and material sources for gold mineralization.The electron microprobe(EPMA)of granitic porphyry biotite from Banmiaozi Gold District as well as related calculations was conducted.The results show that the granitic biotite is characterized by high Si,rich Mg and low Fe,with relatively high Mg mass rate,and belongs to magnesian biotite.According to the biotite composition estimation,the magmatic diagenetic temperature is 700 ℃-750 ℃,the O2 fugacity is-12--14,the depth is 5.0-6.5 km.The biotite composition reveals that the magma source has the feature of mixed crust and mantle sources and the granite is type I granite related to orogenic activities.The granitic porphyry is favorable for gold deposit genesis,and it is speculated that the Banmiaozi Gold Deposit is a medium shallow formation orogenic gold deposit related to the subduction of the ancient Pacific plate.