准噶尔西北缘吐尔库班套阿拉斯加型镁铁-超镁铁岩体的发现及意义  

Discovery of Alaskan-style Tuerkubantao maficultramafic complex in NW-Junggar,NW China,and its significance

作　　者：秦克章[1,2,3] 郭正林 唐冬梅[1,2] 李金祥 郭旭吉[4] 董连慧[1,7] QIN KeZhang;GUO ZhengLin;TANG DongMei;LI JinXiang;GUO XuJi;DONG LianHui(Key Laboratory of Mineral Resources,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Institutions of Earth Science,Chinese Academy of Sciences,Beijing 100029,China;University of Chinese Academy of Sciences,Beijing 100049,China;No.706 Geological Party,Xinjiang Geoexploration Bureau for Nonferrous Metals,Altay 839000,China;Xinjiang Xinhui Geoexploration and Mining Co,limited,Urumqi 830000,China;Institute of Tibetan Plateau Research,Chinese Academy of Sciences,Beijing 100101,China;Xinjiang Bureau of Geology and Mineral Resource,Urumqi 830000,China)

机构地区：[1]中国科学院矿产资源研究重点实验室中国科学院地质与地球物理研究所,北京100029 [2]中国科学院地球科学研究院,北京100029 [3]中国科学院大学,北京100049 [4]新疆维吾尔自治区有色地质勘查局706队,阿勒泰839000 [5]新疆鑫汇地质矿业有限责任公司,乌鲁木齐830000 [6]中国科学院青藏高原研究所,北京100101 [7]新疆维吾尔自治区地质矿产勘查局,乌鲁木齐830000

出　　处：《岩石学报》2018年第7期1897-1913,共17页Acta Petrologica Sinica

基　　金：国家重点研发计划项目(2017YFC0601204);国家自然科学基金项目(41472075);新疆有色地勘局706队萨乌尔成矿带研究项目联合资助

摘　　要：在西准噶尔萨吾尔岛弧带上首次发现了阿拉斯加型(岛弧型)镁铁-超镁铁环状杂岩体,并伴有铜镍矿化,这对认识区域构造格局与区域铜镍找矿具有重要意义。吐尔库班套杂岩体主要岩性为角闪辉长岩、辉长岩和橄榄岩。橄榄岩位于杂岩体的中部,辉长岩主要位于边部,角闪辉长岩位于杂岩体的最外带,表现出环状岩体特征。辉长岩锆石U-Pb谐和年龄为394.6±4.9Ma,形成于早泥盆世。元素地球化学特征表明该镁铁-超镁铁杂岩体来自同一源区,是同一原始岩浆分异演化的产物。高Mg和Cr特征及Sr-Nd-Hf同位素特征暗示源区可能主要显示出略亏损地幔的性质,但由于俯冲富水洋壳物质的加入或者在上升过程中受到地壳物质混染,显示出轻微富集地幔的特征。亏损高场强元素Nb、Ta、Zr、Hf、Ti为岛弧岩浆的特征。该岩体明显不同于新疆东天山黄山、图拉尔根、香山和额尔齐斯东段的喀拉通克等早二叠世造山后伸展背景的Cu-Ni矿床,与美国阿拉斯加东南部Duke Island杂岩体赋存的Cu-Ni矿床相类似。确认其为产于岛弧构造背景的阿拉斯加型岩体。同时确立了在萨乌尔山地区,准噶尔洋壳的俯冲作用在早泥盆世就已存在。在萨乌尔岛弧带泥盆纪阿拉斯加型岩体中具有寻找岩浆硫化物铜-镍-铂矿的地质条件与潜力。Northwestern margin of Junggar is located at the convergence of southwestern of Altai metallogenic belt and north of West Junggar,and in the binding district between Siberian plate and the Junggar plate,and is an important tectonic-magmatic-metallogenic province in northern Xinjiang. The Devonian Tuerkubantao mafic-ultramafic complex of Alaskan type was discovered in the Sawuer arc belt for the first time,accompanying by copper-nickel mineralization,which has significance on the prospecting of the regional and circum-Junggar arc belt. Tuerkubantao complex has the ring-shape characteristics,peridotite,gabbro,and hornblende gabbro occurs from inner to outer. Gabbro yields a zircon U-Pb concordia age of 394. 6 ± 4. 9 Ma,forming in the Early Devonian. Major and trace element characteristics indicate that the mafic-ultramafic complex was the product of differentiation of the same primary magma from the mantle source. High Mg O and Cr abundance,Sr-Nd and Hf isotopic characteristics suggest that the magma source may be slightly depleted mantle,contaminated by the addition of subducted oceanic crust and by a small amount of crustal material in the process of ascend from mantle to upper crust. The rocks are characterized by enrichments in large-ion lithophile elements（ LILE： Rb,Ba,Sr）,more mobile highly incompatible lithophile elements（ HILE）（ U,Th） and relatively depletion in high field strength elements（ HFSE：Nb,Ta,Zr,Hf,Ti,P） suggesting that the primary magma of Tuerkubantao mafic-ultramafic complex is arc magma in nature.However,it is significantly different from Xiangshan,Huangshan and Tulaergen magmatic Cu-Ni deposit in the eastern Tianshan,and Kalatongke in the eastern section of Irtysh metallogenic belt forming at the Early Permian post-orogenic extension setting,but is similar to Duke Island Complex hosting Cu-Ni mineralization in the southeastern Alaska. Based on these features,we confirm Tuerkubantao complex is the Alaskan-type formed in the arc setting. In addition,the inference supports p

关 键 词：吐尔库班套杂岩体 锆石定年 地球化学 阿拉斯加型 西准噶尔萨乌尔岛弧 Cu-Ni-PGE矿化潜力 

分 类 号：P588.124[天文地球—岩石学] P588.125[天文地球—地质学]