新疆青河县玉勒肯-哈腊苏叠加改造型斑岩铜金(钼)矿床地质特征及成因

摘要

Yuleken-Halasu porphyry copper-gold ( molybdenum) deposit, located in the northwestern section of Kalaxiangerrnporphyry copper metallogenic belt, lies on the northeastern margin of Junggar Basin. Granodiorite porphyry and granite porphyry in Early Hercynian are the main ore-bearing porphyries. The wall rocks are basically a set of volcanic-sedimentary rock series in the Middle Devonian Beitashan Formation, intruded by magmatic rocks in Late Hercynian and Indosinian. Of all the deposits in Kalaxianger metallogenic belt, Yuleken-Halasu deposit is the most intensively deformed. A series of schistositized belts occur in Yuleken-Halasu ore area due to impact of the Erqisi fault. Meanwhile, most of the ore-bearing porphyries and the wall rocks are mylonitized and schistositized inordinately. The main ore rocks are not only mineralized in the form of stockwork and dissemination at the early stage of typical porphyry deposit, but also superimposed in the form of mineralization in the schistosity, mylonitized foliation and cleavage at the late stage. Geochronological study indicates that there are several magmatic and tecton-thermal events in Devonian-Triassic and metallogenic events in Devonian-Carboniferous recorded in the metallogenic belt. Through this article and the previous studies, the metallogenic belt, intruded by mass medium-acidic porphyries, was in the island arc tectonic setting related with oceanic subduction in Middle-Late Devonian (390 ~ 360Ma) , accompanied by large-scale Cu-Mo mineralization. The whole metallogenic belt went through collision stage with intensely tectonic reworking and superimposed mineralization in Early Carboniferous (360 ~330Ma). Furthermore, Cu-Mo mineralization was developed along the mylonite foliation. The post-collision stage in Middle-Late Carboniferous (330~300Ma) was characterized by superimposed molybdenite + chalcopyrite + K-feldspar veins mineralization. The metallogenic belt underwent post-orogenic extension stage in Early Permian (270 ~ 260Ma) , causing Cu-Mo filled and re-enriched in structural fracture cleavage, which resulted in superimposed mineralization developed along the fracture cleavage. In Triassic, the whole metallogenic belt was in intracontinental orogenic stage, accompanied by vein-type superimposed mineralization which was associated with low-angle overthrust faults. Therefore, Yuleken is a typical porphyry deposit which is characterized by superimposition and tectonic reworking.%玉勒肯哈腊苏斑岩铜金(钼)矿床位于准噶尔盆地东北缘,卡拉先格尔斑岩铜矿带北西端.该矿床含矿斑岩为海西早期花岗闪长斑岩和花岗斑岩,围岩为中泥盆统北塔山组火山-沉积岩系,同时还有海西晚期和印支期岩浆岩(热)活动的记录.在整个斑岩铜矿带中,玉勒肯矿床构造作用最为强烈,主要受到区域额尔齐斯和二台断裂带多期构造活动的影响,矿区大部分含矿斑岩和围岩发生了不同程度的片理化或糜棱岩化作用.矿石矿物的赋存状态,除早期细脉浸染状斑岩型矿化外,还叠加有后期的沿片理面、糜棱面理,及破劈理分布的细脉状矿化.同位素年代学研究表明,玉勒肯矿区记录了从泥盆纪到三叠纪的构造、岩浆和成矿事件.综合本文及前人研究资料,本文认为卡拉先格尔斑岩铜矿带,在中-晚泥盆世(390～360Ma)时处于与俯冲有关的岛弧构造背景,有中酸性斑岩侵入以及斑岩型Cu-Mo矿化;早石炭世(360 ～ 330Ma)时,经历了碰撞阶段的改造成矿作用,矿化沿糜棱面理发育;中晚石炭世(330～300Ma)为后碰撞阶段,发育以辉钼矿-黄铜矿-钾长石脉为特征的叠加成矿;早二叠世(270 ～ 260Ma)进入造山后伸展阶段,形成以沿破劈理面分布的叠加成矿;进入三叠纪以后,为陆内造山阶段,也见少量脉状矿化.可见,玉勒肯哈腊苏矿床是一个具叠加改造成矿特色的斑岩型矿床.