新疆琼库都克Ag-Pb-Zn多金属矿区岩浆岩地球化学特征及锆石U-Pb年龄研究

Geochemical Characteristics and Zircon U-Pb Ages of the Magmatite inthe Qiongdukuke Ag-Pb-Zn Polymetallic Deposit of Xinjiang

琼库都克银多金属矿床位于新疆哈密东北200km的小石头泉地区,是一个浅成低温热液型的银铅锌多金属矿床。地球化学特征上,矿区的花岗斑岩、二长花岗岩和黑云母花岗岩表现为高硅(SiO_2平均值分别73.45%、76.69%、76.97%),高碱(K_2O平均值为3.22%、2.49%、4.78%,Na_2O平均值为2.99%、5.20%、3.60%)、低铝(Al_2O_3平均值分别为13.29%、12.19%、11.97%),都属于钙碱性岩石(里特曼指数σ的平均值分别为1.27、1.76、2.08,σ<3.3),微量元素和稀土元素表现为富集大离子亲石元素和轻稀土元素,相对亏损高场强元素和重稀土元素,具有较为明显的Eu负异常(δEu平均值为0.57、2.07、0.15)。LA-ICP-MS U-Pb定年实验获得二长花岗岩320±1.5Ma,花岗斑岩312±1.7Ma和黑云母花岗岩314±2.8Ma,代表了该岩浆岩的形成年龄,说明成岩年龄为晚石炭世。矿区采集的岩浆岩样品地球化学特征说明琼库杜克银多金属矿区形成于岩浆岛弧环境。整个矿床形成过程伴随着哈尔里克山的造山作用,大致可以推断矿床形成于早石炭世-晚二叠世之间。

The Qiongdukuke Ag-Pb-Zn polymetallic deposit, located in the Xiaoshitouquan area 200 km away from northeast Hami, Xinjiang, is an epithermal Ag-Pb-Zn polymetallic deposit. Granite porphyries, monzonitic granites and biotite granites in the mining area are characterized by high silicon （average values of SiO2 are 73.45%, 76.69% and 76.97%）, high alkaline（average values of K2O are 3.22%, 2.49% and 4.78%; average value of Na2O are 2.99%, 5.20% and 3.60%） and low aluminum （average value of Al2O3 are 13.29%, 12.19% and 11.97%） in terms of the major element, belonging to calc-alkaline series （average values of Rittmann Index are 1.27, 1.76 and 2.08, σ〈3.3）. The results of the trace element and rare earth element tests suggest that they are enriched in large ion lithophile elements and light rare earth elements but depleted in high field strength elements and heavy rare earth elements, with relatively prominent negative Eu anomaly （average values of δEu are 0.57, 2.07 and 0.15）. The zircon U-Pb dating by LA-ICP-MS yields ages of 320±1.5 Ma in monzonitic granites, 312±1.7 Ma in granite-prophyry and 314±2.8 Ma in biotite granites. These ages indicate that these igneous rocks were emplaced in the Late Carboniferous epoch. Geochemical characteristics of the collected magmatic rocks in this deposit indicate that this deposit was formed in a magmatic arc environment. The whole formation process of the deposit was accompanied by orogeny of Harlik mountains, and we can roughly infer that the deposit was formed between the Early Carboniferous and Late Permian.