吉中早中生代高镁安山岩:性质与意义  

Early Mesozoic high-Mg andesites in central Jilin Province: nature and implications

作　　者：王红燕 周建波 李功宇[1,2] 王斌 李皓东[1,2] 陈卓 WANG Hongyan;ZHOU Jianbo;LI Gongyu;WANG Bin;LI Haodong;CHEN Zhuo(Key Laboratory of Mineral Resources Evaluation in Northeast Asia,Ministry of Natural Resources,Changchun,Jilin 130061,China;College of Earth Sciences,Jilin University,Changchun,Jilin 130061,China;Shandong Provincial No.6 Exploration Institute of Geology and Mineral Resources,Weihai,Shandong 264209,China)

机构地区：[1]自然资源部东北亚矿产资源评价重点实验室,吉林长春130061 [2]吉林大学地球科学学院,吉林长春130061 [3]山东省第六地质矿产勘查院,山东威海264209

出　　处：《地质学报》2022年第5期1803-1814,共12页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41730210)资助成果。

摘　　要：高镁安山岩主要产出于板块会聚边缘的大洋俯冲消减带岛弧环境,是岛弧岩浆作用的代表性产物,研究其相关构造属性,对示踪板块俯冲时限、俯冲带构造背景、大洋俯冲作用过程中岩石圈地幔演化等方面至关重要。长春-延吉缝合带位于佳木斯-兴凯地块和华北板块之间,为古亚洲洋的闭合和古太平洋的启动过程提供了关键的信息,但有关缝合带位置与俯冲方式仍然存在很大的争议。本文对采自长春-延吉缝合带吉东地区的色洛河群绿片岩样品进行了主量和微量元素分析以及锆石U-Pb年龄测定,结果表明这套样品原岩为一套赞岐质高镁安山岩,具有富Mg、低Al、低Ti、高Cr、Ni等特征,与日本Setouchi火山岩带中的赞岐岩具可比性,由俯冲板片(洋壳+上覆沉积物)部分熔融的流体与地幔发生混合而成,形成于华北板块北部边缘之上的陆缘岛弧环境,由吉林-黑龙江洋的俯冲所致。锆石U-Pb定年结果表明其形成时代为中三叠世(246±2 Ma)。本文证据显示原定义为中元古代的色洛河群时代可能为早中生代,并非元古宙或者晚古生代增生杂岩,而应该为华北板块上形成于早中生代的陆缘岛弧安山岩。区域构造分析显示,长春-延吉缝合带不是天山-索伦-西拉木伦-长春缝合带的东延部分,而是吉林-黑龙江高压变质带的南延部分,形成于三叠纪前后古太平洋板块的西向俯冲作用导致的佳木斯-兴凯地块与华北板块之间的拼合。High-Mg andesites are mainly exposed in island arc environment along subduction zone of oceanic plate, which is a representative product of island arc magmatism. Detailed studies on the tectonic affinities of high-Mg andesites are of great significance for tracing the timing, tectonic setting, and evolution of lithospheric mantle during the oceanic plate subduction. The Changchun-Yanji suture lies between the Jiamusi-Khanka Block and the North China Craton, which provides crucial information on the closure of the Paleo-Asian Ocean and the commencement of the westward subduction of the Paleo-Pacific. However, the location of the suture between these two blocks and the subduction mode of the Paleo-Pacific are still controversial. In this study, we collected seven green schists from the Seluohe Group along the Changchun-Yanji suture and report the major and trace elements and zircon U-Pb age of these samples.The results show that they are a suite of high-Mg andesites with higher MgO, Cr and Ni, and lower Al;O;, TiO;, which are similar to the Sanukite in the Setouchi volcanic belt in Japan. They were formed by the interaction between the mantle wedge and the fluids from subducted slab(oceanic crust and overlying sediments), and were formed in a continental marginal arc on the North China Craton, which was subducted by the Jilin-Heilongjiang Ocean in the Middle Triassic, with zircon U-Pb age of 246±2 Ma. The evidence in this study suggests that the formation time of the Seluohe Group may be Early Mesozoic, and it is not an accretionary complex formed in the Proterozoic or the Late Paleozoic, but a suite of early Mesozoic continental marginal arc andesites.Regional tectonic analyses show that the Changchun-Yanji suture is not the eastern extension of the Tianshan-Solonker-Xar Moron-Changchun suture, but the southern margin of the Jilin-Heilongjiang high-pressure metamorphic belt, which was formed during the collision between the Jiamusi-Khanka Block and North China Craton caused by the westward subduction of the Paleo

关 键 词：高镁安山岩 锆石U-PB年龄 陆缘岛弧 中三叠世 长春-延吉缝合带 

分 类 号：P534.5[天文地球—古生物学与地层学] P588.144[天文地球—地质学]