东天山古生代斑岩铜矿床成矿规律和构造背景

Metallogeny and tectonic setting of Paleozoic porphyry copper deposits in the East Tianshan

东天山铜成矿带是中亚成矿域的重要组成部分,发育土屋、延东大型铜矿,三岔口、玉海中型铜矿,赤湖、福兴、灵龙、玉带和四顶黑山等小型铜矿床。其中的斑岩铜矿带主要沿大南湖-头苏泉岛弧带近东西向展布,其成岩作用集中于志留纪和石炭纪,而成矿峰期为石炭纪。东天山斑岩铜矿带赋矿围岩包括火山岩、花岗岩和沉积岩,围岩蚀变主要有黑云母-磁铁矿化、绢英岩化和青磐岩化,钾化相对较弱。成矿岩体主要为中酸性钙碱性花岗岩,富集大离子亲石元素,亏损高场强元素,具有高Sr/Y比值,显示典型的岛弧岩浆岩和埃达克质特征。成矿流体早阶段发育大量含子晶的高盐度包裹体,为H2O-NaCl±CO_(2)体系,氢氧硫同位素显示明显的岩浆热液特征。锶钕铪同位素表明成矿岩体具有新生地壳和亏损地幔混合来源。东天山斑岩铜矿带形成于古天山洋的多期次俯冲造山,因而具有多期叠加成矿的特征。石炭纪钙碱性岩浆岩是下一步找矿的主要目标,后期构造叠加可能导致富矿体的形成。

The East Tianshan copper metallogenic belt is an important part of the Central Asian metallogenic belt,which mainly includes large-scale Tuwu and Yandong,medium-scale Sanchakou and Yuhai,and small-scale Chihu,Fuxing,Linglong,Yudai and Sidingheishan porphyry copper deposits.The porphyry copper belt is distributed along the Dananhu-Tousuquan island arc in a nearly EW direction.Magmatic activities related to this metallogenic belt mainly include two peak periods of the Silurian and Carboniferous periods,while the peak period of mineralization is the Carboniferous.The host rock strata of the porphyry copper belt are mainly Paleozoic volcanic rocks,granites and sedimentary rocks.The wall rock alteration mainly includes biotite-magnetite alteration,phyllic and propylitization,with a relatively weak potassium alteration.The ore-forming rocks are mainly intermediate-acid calc-alkaline granites with typical island arc magmatic and adakite characteristics,which are enriched in large ion lithophile elements and depleted in high field strength elements with high Sr/Y ratios.In the early stage of ore-forming fluid,a large number of daughter bearing high salinity inclusions are developed,which is an H2O-NaCl±CO_(2)system.H-O-S isotopes show obvious magmatic hydrothermal characteristics.Sr-Nd-Hf isotopic characteristics indicate that the ore-bearing rocks have a mixed source of juvenile crust and depleted mantle.The East Tianshan orogenic belt experienced a multi-directional and multi-stage arc basin transformation in the Paleozoic and experienced multiple magmatic hydrothermal activities,as a result,it has the characteristics of multi-stage superimposed mineralization.The Carboniferous calc-alkaline magmatic rocks are the main target for ore prospecting in the next step,and the late structural superposition may lead to the formation of rich ore bodies.