青海多彩铜多金属矿区火山岩地球化学特征及其对岛弧环境的限定

青海多彩铜多金属矿累计探明Cu+Pb+Zn资源量103万t。该矿位于三江成矿带北西段,处于特提斯-喜马拉雅构造域、北羌塘-昌都陆块北缘。矿区火山岩出露广泛,岩性为安山岩、英安岩和流纹岩。对矿区火山岩进行了地球化学特征研究,结果表明,矿区火山岩为过铝质钙碱性岩石,稀土元素配分曲线属于轻稀土富集型,富集大离子亲石元素Ru、Ba、K、Th,相对亏损高场强元素Nb、Ta、P、Ti,铕负异常明显;岩石具有高Ba含量特征,微量元素特征显示成岩熔浆物质主要来源于幔源物质;岩石具有岛弧火山岩地球化学特征。结合年代学数据和地球化学特征,认为多彩矿区火山岩属于晚三叠世金沙江洋壳向北羌塘陆块俯冲的产物,指示了活动大陆边缘的岛弧环境。

Geochemical characteristics and geological significance of volcanic rocks in Duocai copper polymetallic mining area, Qinghai Province and its limitation to the island arc environment

The Duocai copper polymetallic mining area in Qinghai Province is located in the northwest of Sanjiang metallogenic belt, in the Tethys Himalayan structural domain and in the northern margin of the North Qiangtang Changdu landmass. The volcanic rocks in the mining area are widely exposed, and the lithology is andesite, dacite and rhyolite, which are studied. The results show that the volcanic rocks are peraluminous calc alkaline rocks. The REE distribution curve belongs to the light rare earth enrichment type, which is rich in large ion lithophile elements Ru, Ba, K, th, relatively deficient and high field strength Elements Nb, Ta, P, Ti, europium negative anomalies are obvious. The rocks have high Ba content characteristics, and the trace element characteristics show diagenetic magma. The rocks are mainly derived from mantle derived materials and have geochemical characteristics of island arc volcanic rocks. Based on the geochronological data and geochemical characteristics, it is considered that the volcanic rocks in the Duocai copper-polymetallic mining area are the products of the plate convergence process of the subduction of the Paleo Tethys ocean plate to the North China landmass in the Late Triassic, indicating the island arc environment of the active continental margin.