黑龙江省翠中铁钨多金属矿床成岩成矿年代学、地球化学特征及地质意义

为了厘清翠中铁钨多金属矿床浅部的粗粒碱长花岗岩和深部的细粒碱长花岗岩与成矿之间的关系,本次工作对这2种岩浆岩分别进行了岩石地球化学、锆石U-Pb年代学和Hf同位素分析,对岩石和矿石开展了Pb同位素研究.粗粒碱长花岗岩和细粒碱长花岗岩的锆石U-Pb年龄分别为503±2.9 Ma和201±6.4 Ma,表明其侵入时代分别为加里东中期和印支晚期-燕山早期.辉钼矿Re-Os同位素模式年龄为202±2.9 Ma,与细粒碱长花岗岩锆石U-Pb年龄基本一致.粗粒碱长花岗岩中锆石的εHf(t)值变化于-8.31~0.57,指示其来源于中元古代古老地壳部分熔融,细粒碱长花岗岩中锆石的εHf(t)值为2.84~4.78,表明其起源于亏损地幔中新增生的年轻地壳物质的部分熔融.综合成岩成矿时代、成矿元素趋势面分析以及岩矿石Pb同位素对比,我们认为翠中铁钨多金属矿床的成矿作用与深部的细粒碱长花岗岩有关.结合区域构造演化历史,推测成矿作用可能形成于佳木斯地块向松嫩地块俯冲挤压的构造环境.

Petrogenic and Metallogenic Geochronology,Geochemical Characteristics and Its Geological Implications of Cuizhong Fe Polymetallic Deposit,Heilongjiang Province

Two main types of igneous rocks are distributed in the Cuizhong Fe polymetallic deposit, including the coarse-grained alkali-feldspar granite in the shallow part and the fine-grained alkali-feldspar granite at depth, whose relationships with ore mineralization have long been debated. Whole rock geochemistry, zircon U-Pb geochronology and Hf isotopic analyses are carried out for these two types of granitoids. Pb isotopic analyses are performed on both the granitoids and the sulfides. The coarse-grained alkali-feldspar granite and fine-grained alkali-feldspar granite yield weighted mean 206Pb/238U age of 503±2.9 Ma and 201±6.4 Ma respectively, indicating that they were formed during middle Caledonian and late Indosinian-early Yanshanian respectively.The Re-Os model age of molybdenite is 202±2.9 Ma, which is consistent with the crystallization age of the fine-grained alkali-feldspar granite.Zircons in the coarse-grained alkali-feldspar granite display ε_Hf(t) values of -8.31 to 0.57, indicating that it was derived from partial melting of Mesoproterozoic crustal rocks. Zircon crystals in the fine-grained alkali-feldspar granite have ε_Hf(t) values of 2.84 to 4.78, indicating that it was generated by reworking of newly-growing juvenile crustal material which was originated from depleted mantle. In combination with the metallogenic and petrologic ages, trend surface analysis of ore-forming elements, and the comparison of Pb isotopes, we suggest that the mineralization in the Cuizhong Fe polymetallic deposit is genetically associated with the fine-grained alkali-feldspar granite. The polymetallic mineralization was generated in a compressional tectonic setting in response to the subduction of the Jiamusi Block towards the Songnen Block.