摘要
为确定松嫩—张广才岭地块东缘晚三叠世的构造属性,并限制古太平洋板块开始向欧亚大陆俯冲的时间,对松嫩—张广才岭地块东缘西砬子沟花岗闪长岩进行了锆石LA-ICP-MS U-Pb年龄和岩石地球化学研究。西砬子沟花岗闪长岩锆石U-Pb测年结果为(216±1) Ma,为晚三叠世岩浆作用的产物。地球化学研究表明,西砬子沟花岗闪长岩为准铝质高钾钙碱性Ⅰ型花岗岩,富硅,高钾,低铁镁钙,富集LREE,相对富集LILE (Rb、Th、U、K),亏损HFSE (Nb、Ta、Ti),这些特征表明西砬子沟花岗闪长岩是下地壳物质部分熔融的产物。结合相邻地区同时代火成岩的岩石组合特征与空间分布,笔者认为西砬子沟花岗闪长岩形成于古亚洲洋闭合后的伸展环境,古太平洋板块向欧亚板块的俯冲作用发生在晚三叠世之后。
In order to determine the Late Triassic tectonic attribute in the eastern margin of Songnen-Zhangguangcai Range Massif,and delineate the time of the subduction of Palaeo-Pacific Plate underneath the Eurasian continent,LA-ICP-MS zircon U-Pb dating and geochemical analysis of the Xilazigou granodiorite were undertaken. The zircon U-Pb age of the Xilazigou granodiorite is( 216 ± 1) Ma that is the product of magmatism in Late Triassic. The geochemical data indicate that the Xilazigou granodiorite belongs to metaluminous,high-potassium calc-alkaline I-type granite,the granites are characterized by high content of SiO2 and K2 O,low contents of MgO,CaO and Fe2 O3,enrichment of LREE,relative enrichment in LILE( Rb,Th,U,K) and depletion in HFSE( Nb,Ta,Ti). These characteristics suggest that the Xilazigou granodiorite was derived from partial melting of the lower crustal materials. According to the rock assemblage and spatial distribution of the contemporaneous igneous rocks in adjacent areas,the authors suggest that the Xilazigou granodiorite formed in the post-orogenic extensional setting which could be related to the closure of the Paleo-Asian Ocean,following the subduction of Palaeo-Pacific Plate underneath the Eurasian continent after Late Triassic.
作者
孙永刚
王聚胜
张辉
詹天宇
殷大分
SUN Yong-gang;WANG Ju-sheng;ZHANG Hui;ZHAN Tian-yu;YIN Da-fen(College of Earth Sciences,Jilin University,Changchun 130061,China;Jilin Institute of Geological Survey,Changchun 130061,China)
出处
《世界地质》
CAS
2019年第1期68-79,共12页
World Geology
基金
中国地质调查局项目(DD20160049)
