摘要
为探讨班公湖-怒江缝合带西段沙木罗组地层中闪长玢岩脉的成因、构造环境及其对区域构造演化的指示,对其开展了年代学和全岩地球化学研究。结果表明,闪长玢岩的LA-ICP-MS锆石U-Pb年龄为（103.5±1.5）Ma,具准铝质高钾钙碱性I型花岗岩特征,中等分异,稀土配分模式呈左陡右缓的右倾型,具中等负铕异常,相对富集不相容元素Rb、K、Th、Zr、Hf、U等,而亏损Ba、Nb、P、Ti高场强元素。结合区域地质背景认为,闪长玢岩形成于班公湖-怒江洋向北俯冲的大陆边缘弧,俯冲沉积物熔体交代地幔楔发生部分熔融形成幔源岩浆,在密度差的作用下幔源岩浆向上运移,底侵下地壳,引发下地壳物质部分熔融,并与之发生混合,形成了研究区闪长玢岩的母源岩浆;早白垩世晚期班公湖-怒江特提斯洋壳仍向北俯冲于南羌塘之下。
In order to discuss the genesis and tectonic setting of the diorite porphyry dyke in the Shamuluo Formation in the western segment of the Bangongco-Nujiang suture zone,and to further discuss their significances to the regional tectonic evolution,the chronology and geochemistry of the diorite porphyry dyke have been undertaken in this paper. The results indicate that the diorite porphyry is characterized with features of a metaluminous,high-potassium and calc-alkaline I-type granitoid,with a LA-ICP-MS zircon U-Pb dating age of（ 103. 5 ± 1. 5） Ma and the medium differentiation. The chondrite-normalized REE patterns are generally right-declined patterns which are characterized with steep in left and flat in rightand intermediate negative Eu anomalies. The primitive mantle-normalized trace element spider diagrams show that it is relatively enriched in large ion lithophile elements,such as Rb,K,Th,Zr,Hf,U,and is depleted in high field strength element,such as Ba,Nb,P and Ti. With the combination of regional geological background,it is suggested that the diorite porphyry could be formed in the continental arc setting resulted fromof the northward subduction of the Bangongco-Nujiang Tethyan Ocean.The magma was mainly derived from the partial melting of lower crust which was caused by the underplating of the mantle magma derived from the metasomatized mantle wedge by subducted sediments. It is believed that the Bangongco-Nujiang oceanic plate was still northward subducting to the Qiangtang plate in late stage of the early Cretaceous approximately at（ 103. 5±1. 5） Ma.
作者
雷传扬
吴建亮
尹显科
刘文
王波
李威
袁华云
张伟
尹滔
裴亚伦
LEI Chuan-yang;WU Jian-liang;YIN YUAN Hua-yun;ZHANG Xian-ke;LIU Wen;WANG Bo;LI Wei;Wei;YIN Tao;PEI Ya-lun(Geological Survey of Sichuan Province, Chengdu 610081, China)
出处
《矿物岩石地球化学通报》
CAS
CSCD
北大核心
2018年第2期250-259,共10页
Bulletin of Mineralogy, Petrology and Geochemistry
基金
中国地质调查局项目(DD20160026)
