摘要
奥依塔克辉长岩出露于塔里木盆地西部,位于塔里木地块与北昆仑地体之间的奥依塔克韧性剪切带上,侵入于奥依塔克斜长花岗岩和英云闪长岩内。本研究对辉长岩进行了岩相学分析、全岩主微量分析、锆石微量元素分析和锆石U-Pb定年测试。研究结果显示,辉长岩的SiO_(2)含量为49.6%~51.3%,K_(2)O含量为0.16%~0.41%, Na_(2)O含量为2.58%~3.30%,为拉斑系列的辉长岩, Mg#值为66~68。辉长岩的REE球粒陨石标准化配分曲线呈右倾型,Eu正异常。奥依塔克辉长岩富集大离子亲石元素,亏损高场强元素,微量元素N-MORB标准化图解中Nb负异常。锆石U-Pb年代学研究表明,辉长岩的侵位年龄为206.5±3.2Ma。在Th-Hf-Ta构造图解中和U/Yb-Nb/Yb构造判定图解中,奥依塔克辉长岩都落入岛弧构造环境。地球化学特征表明奥依塔克辉长岩可能形成于大洋俯冲的背景,岩浆来源可能为地幔物质和俯冲板片混合作用的熔体。奥依塔克辉长岩可能形成于古特提斯洋洋壳的向北俯冲到西昆仑地区206Ma可能依然存在着古特提斯洋的洋壳俯冲,北昆仑地体与塔里木地块尚未完全碰撞。
The Aoyitake gabbro, which intruded plagioclase granite and tonalite, yielded in the Aoyitake ductile shear belt between the Tarim and North Kunlun blocks. Petrographic features, whole-rock major and trace element compositions, and zircon U-Pb ages are reported for the gabbro in this paper. The Aoyitake gabbro has classical igneous textures with large plagioclase crystals, which indicate a slow cooling history. High Mg# values(66 to 68)indicate that the gabbro may be derived from a hybrid source comprising mantle material and fluids from the melting of a subducted oceanic plate. The zircon U-Pb dating yielded an age of 206.5 ± 3.2 Ma for the gabbros. In the tectonic discrimination diagram, the Aoyitake gabbros plot in the IAT region and within the Continental Arc-type field on the zircon U/Yb-Nb/Yb diagram. Combined with previous research on tectonic evolution of west Kunlun block, we suggest that the subduction of Paleo-Tethys oceanic plate led to melting of lithospheric mantle by dehydration melting. The gabbro exposed in Aoyitake were probably formed by partial melting of the lithospheric mantle, triggered by the Paleo-Tethys oceanic crust slab subduction northward and magma upwelling in the Aoyitake back-arc basin. Our results also show that the west Kunlun area had still existed in the oceanic crust of the Paleo-Tethys until 206 Ma. This provides new data on the time of the closure of the Paleo-Tethys ocean and the orogeny of the Kunlun mountains. The closure time of the Paleo-Tethys ocean was no later than 206 Ma, and the timing of the west Kunlun large-scale orogeny was no earlier than 206 Ma.
作者
慕生禄
王核
王赛蒙
白洪阳
陈谋
贺国锐
MU Shenglu;WANG He;WANG Saimeng;BAI Hongyang;CHEN Mou;HE Guorui(Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,Guangdong,China;University of Chinese Academy of Sciences,Beijing 100049,China;Guangyuan Natural Gas Utilization Industrial Park Management Committee,Guangyuan 628017,Sichuan,China;Guangdong Nonferrous Metals Geological Prospecting Institution,Guangzhou 510080,Guangdong,China;Sichuan Branch of China National Geological Exploration Center of Building Materials Industry,Chengdu 610052,Sichuan,China)
出处
《地球化学》
CAS
CSCD
北大核心
2022年第3期365-376,共12页
Geochimica
基金
新疆维吾尔自治区科技重大专项、重点研发任务专项(2019B00011、2020A03005-3)
第二次青藏科考项目(2019QZKK0802)
国家自然科学基金(91962215、41972088)联合资助。
关键词
辉长岩
锆石U-PB定年
岛弧拉斑系列
古特提斯洋
洋壳俯冲
gabbros
zircon U-Pb dating
island arc tholeiitic series
paleo-tethys ocean
oceanic crust subduction
