东昆仑祁漫塔格虎头崖铅锌多金属矿区花岗岩年代学、地球化学及Hf同位素特征

Geochronology,geochemical characteristics and Hf isotopic compositions of granite in the Hutouya deposit,Qimantag,East Kunlun

虎头崖铅锌多金属矿床位于东昆仑祁漫塔格地区,矿区内中酸性侵入岩体广泛发育,且与成矿关系密切。LA-ICP-MS锆石U-Pb同位素年龄测试表明,虎头崖Ⅴ矿带外围花岗闪长岩形成时代为（224.3±0.6）Ma,Ⅷ号矿带矿体下部正长花岗岩形成时代为（239.7±0.8）Ma,岩体形成时代为中—晚三叠世。岩石地球化学表明,花岗闪长岩富钾贫钠（K2O/Na2O为2.02~2.88）,无明显负Eu异常（δEu为0.68~1.06）,富集Rb、Th、U、K等大离子亲石元素,明显亏损Nb、P、Ti等元素,属I型花岗岩;正长花岗岩具高硅、富碱、低铁镁、贫钙磷钛的特征,负Eu强烈（δEu为0.08~0.26）,富集Rb、Th、U、K,亏损P、Ti、Ba、Sr,属高分异I型花岗岩;二者均形成于后碰撞构造背景;Hf同位素组成不均一,指示其经历了壳幔岩浆混合作用,幔源物质的加入可能带来了丰富的成矿物质。

The Hutouya Pb- Zn polymetallic ore deposit is located in Qimantag, East Kunlun. Intermediate- acid intrusive rocks occur widely in this area, and are closely related to iron polymetallic mineralization. The results of LA- ICP- MS zircon U- Pb isotope dating reval that the granodiorite in the periphery of No. Ⅴore belt was formed at（224.3±0.6） Ma and the orthoclase granitein No. Ⅷ ore belt was formed at（239.7±0.8） Ma. Petrogeochemistry shows that the granodiorite is rich in K and poor in Na, with no strong negative Eu anomalies（δEu=0.68-1.06）, and is enriched in Rb, Th, U, K, but depleted in Nb, P, Ti, thus belonging probably to I- type granite series. The orthoclase granite is characterized by high Si O2, high alkali, low TFe O, Mg O, Ca O, P2O5 and Ti O2,strong negative Eu anomalies（δEu 0.08- 0.26）, enrichment of Rb, Th, U, K,and depletion of P, Ti, Ba, Sr, belonging probably to highly fractionated I-type granite series. Both of them were formed at the post-collision stage. Variable Hf isotopic compositions of zircon indicate that it experienced magma mixing, which provided large quantities of ore- forming meterials for large- scale polymetallic mineralization.