今天是2018年10月18日

东昆仑古特提斯构造带中的原特提斯记录:来自苦海镁铁质岩块的证据

DOI:10.3799/dqkx.2018.714

作者:张航,王宗起,马昌前,熊富浩,蒋红安,郭宇衡

联系地址:中国地质科学院矿产资源研究所,北京 100037

摘要:研究苦海地区是否发育原特提斯洋盆有助于揭示阿尼玛卿构造带和秦岭勉略构造带是否具有相似的演化过程,确定“秦-祁-昆”原特提斯洋的南界.产出于苦海地区的镁铁质岩构造就位于上古生界强片理化浊积岩中,显示出混杂特征.LA-ICP-MS锆石年代学研究显示该地区雪穷辉长岩块结晶年龄为610~630 Ma,雅日玄武安山岩结晶年龄约为504 Ma.微量元素和同位素地球化学分析表明,雪穷镁铁质岩浆起源于大陆岩石圈地幔,未受到地壳混染,形成于板内环境,雅日镁铁质岩浆起源于受俯冲沉积物产生的流体交代的地幔楔,源区受到一定地壳混染,形成于俯冲环境,反映秦昆结合地区存在早古生代大洋的俯冲-增生作用.结合区域资料,阿尼玛卿构造带和勉略构造带都有新元古代晚期至早古生代的大洋物质记录,表明这一时期阿尼玛卿和勉略构造带有可对比性,原特提斯洋的南界达到阿尼玛卿和勉略构造带.

关键字:苦海群;混杂带;锆石U-Pb年代学;地球化学

Proto-Tethys Record in Paleo-Tethys Belt of East Kunlun:Evidence from Kuhai Mafic Blocks

Author:Zhang Hang, Wang Zongqi, Ma Changqian, Xiong Fuhao, Jiang Hong'an, Guo Yuheng

Author Address:Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China

Abstract:The junction of the East Kunlun orogen and the West Qinling orogen is a key area for contrasting the tectonic evolution of the East Kunlun orogen with West Qinling orogen and determining the south margin of “Qinling-Qilian-Kunlun” proto-Tethys ocean. Kuhai mafic rocks,situated in the junction, were structurally placed into a Late Paleozoic foliated turbidites, indicating typical characteristics of mélange. The LA-ICP-MS zircon U-Pb dating indicates that the gabbros in Xueqiong were crystallized at 610-630 Ma, and the mafic rocks in Yari were crystallized with an age of about 500 Ma. Geochemical and isotopic studies show that Xueqiong gabbros were derived from subcontinent lithosphere mantle in a rift setting. Yari mafic rocks were derived from enrichment mantle wedge modified by subduction metasomatic fluids in subduction, representing the existence of the ocean. According to regional data analysis, the situation that proto-tethys materials mixed in paleo-tethys mélange belt may demonstrates a subduction-accretion process occurred in the junction of the East Kunlun orogen and the West Qinling orogen. From Late Neoproterozoic to the Early Palaeozoic, A'nyemaqen ocean had similar tectonic evolution with Mianlüe ocean. The margin of proto-Tethys ocean reached A'nyemaqen and Mianlüe mélange.

Keyword:Kuhai Group; mélange; zircon U-Pb chronology;geochemistry

 

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作者简介:张航(1989-),男,博士研究生,主要从事岩石学与区域构造研究.ORCID:0000-0001-6549-824X.E-mail: zhhang1989@163.com

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