东昆仑古特提斯造山带巴隆地区中性岩墙群的岩石成因与构造意义  

Petrogenesis and tectonic implications of the Balong intermediate dyke swarms in East Kunlun Paleo-Tethyan orogenic belt

作　　者：楚志强 闫东东 赵涵[1,2] 龚婷婷[1,2] 熊富浩[1,3] CHU Zhiqiang;YAN Dongdong;ZHAO Han;GONG Tingting;XIONG Fuhao(College of Earth Sciences,Chengdu University of Technology,Chengdu 610059,China;Key Laboratory of Tectonic Controls on Mineralization and Hydrocarbon Accumulation of Ministry of Natural Resources,Chengdu University of Technology,Chengdu 610059,China;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]成都理工大学地球科学学院,四川成都610059 [2]自然资源部构造成矿成藏重点实验室,成都理工大学,四川成都610059 [3]油气藏地质及开发工程国家重点实验室,成都理工大学,四川成都610059

出　　处：《沉积与特提斯地质》2024年第2期454-466,共13页Sedimentary Geology and Tethyan Geology

基　　金：国家自然科学基金(41602049);成都理工大学珠峰科学研究计划(2021ZF11412)。

摘　　要：岩墙群是研究造山带构造演化过程与大陆地壳生长机制的重要探针。本文以东昆仑古特提斯造山带巴隆地区中性岩墙群为研究对象,开展了岩石学、年代学和地球化学研究,分析其岩石成因及其对古特提斯造山作用过程的启示。巴隆中性岩墙群以闪长玢岩为主,其锆石U-Pb年龄为250.2±1.3 Ma,属于早三叠世岩浆作用的产物。岩墙群的SiO_(2)含量为52.8%~59.6%,全碱(K_(2)O+Na_(2)O)含量为3.98%~6.25%,Mg#值为24~46,铝饱和指数为0.91~0.98,属于高钾钙碱性、准铝质岩石。样品的轻重稀土元素分异显著,(La/Yb)N值为5.44~7.76,Eu异常不明显(δEu=0.91~1.11)。样品均富集大离子亲石元素,亏损高场强元素,且具有显著的Nb、Ta负异常。岩石成因分析表明巴隆早三叠世中性岩墙群主要起源于古老镁铁质地壳物质的部分熔融,且岩浆受到一定程度的壳–幔混合影响。综合分析区域地质资料,本文认为巴隆地区中性岩墙群形成于东昆仑古特提斯洋俯冲消减的陆缘弧环境,且大陆弧古老地壳物质重熔和壳–幔混合作用是东昆仑古特提斯造山旋回大陆地壳生长演化的重要方式。Dyke swarms are an important"probe"to study the tectonic evolution of orogenic belts and the growth mechanism of continental crust.Herein,we present petrological,geochronological and geochemical studies on the Balong intermediate dyke swarms in East Kunlun Paleo-Tethyan orogenic belt,to unravel their petrogenesis and its implications for the evolution of PaleoTethyan Orogeny.The studied Balong intermediate dyke swarms are mainly composed of diorite porphyrite with zircon U-Pb ages of 250.2±1.3 Ma.They have SiO_(2) contents ranging from 52.8%to 59.6%,total alkali(K_(2)O+Na_(2)O)contents ranging from 3.98%to 6.25%,Mg#values of 24 to 46,and aluminum saturation indices ranging from 0.91 to 0.98,belonging to the high-K calc-alkaline,metaluminous rock series.The samples exhibit significantly fractionation between LREE and HREE with(La/Yb)N ratios of 5.44~7.76,and they show unobvious Eu anomalies(δEu=0.91~1.11).They are enriched in large-ion lithophile elements but depleted in high-field-strength elements with significant negative Nb and Ta anomalies.Petrogenesis study shows that the early Triassic Balong intermediate dyke swarms are mainly derived from partial melting of ancient mafic crust with a certain degree of crust-mantle magma mixing.In combination with regional geology data,this study proposes that the studied intermediate dyke swarms are generated in Paleo-Tethyan oceanic subduction-related continental arc setting,and the reworking of continental arc crust followed by crust-mantle mixing is the key model of growth and evolutionary of continental ancient crust during East Kunlun Paleo-Tethyan orogeny.

关 键 词：中性岩墙群 闪长玢岩 早三叠世 陆缘弧 东昆仑 

分 类 号：P581[天文地球—岩石学] P588.12.1[天文地球—地质学]