特提斯喜马拉雅中新世煌斑岩的成因及构造意义  

Genesis and tectonic significance of Miocene lamprophyres in the Tethys Himalaya

作　　者：孙敏佳 魏震 刘晓强 刘桂萍 宫相宽 郭瑞清 Sun Minjia;Wei Zhen;Liu Xiaoqiang;Liu Guiping;Gong Xiangkuan;Guo Ruiqing(School of Geology and Mining Engineering,Xinjiang University,Ürümqi 830017;Xinjiang Key Laboratory for Geodynamic Processes and Metallogenic Prognosis of the Central Asian Orogenic Belt,Ürümqi 830017;State Key Laboratory of Metallogenic Mechanism of Endogenous Metal Deposits,Nanjing University,Nanjing 210046)

机构地区：[1]新疆大学地质与矿业工程学院,乌鲁木齐830017 [2]新疆中亚造山带大陆动力学与成矿预测自治区重点实验室,乌鲁木齐830017 [3]南京大学内生金属矿床成矿机制研究国家重点实验室,南京210046

出　　处：《地质科学》2024年第4期853-869,共17页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学基金项目(编号:42202114);内生金属矿床成矿机制研究国家重点实验室开放研究基金课题项目(编号:2022-LAMD-K12);新疆维吾尔自治区重点研发计划项目(编号:2022B03015-2);新疆大学博士启动基金项目(编号:620320043)资助。

摘　　要：后碰撞幔源岩浆是示踪深部地球动力学和地幔动力学过程的最直接指针。印度-亚洲碰撞缝合带南侧特提斯喜马拉雅中-新生代地层中发现了规模可观的煌斑岩岩墙群,锆石U-Pb定年结果显示其整体侵位时代介于15~10 Ma。煌斑岩具有中等的SiO_(2)含量(50.0%~52.9%),较高的K_(2)O(2.30%~4.77%)和Na_(2)O含量(3.04%~4.23%),属于钙碱性煌斑岩。其高MgO含量(5.64%~7.63%)和Mg^(#)值(70~74)以及高Cr(363×10^(-6)~465×10^(-6))、Co(24.7×10^(-6)~31.2×10^(-6))、Ni(128×10^(-6)~269×10^(-6))等过渡族元素丰度,显示显著的幔源岩石特征,未受明显地壳混染。煌斑岩富含大离子亲石元素、轻稀土元素(Th、U、Ba、Pb、Nd),贫高场强元素和重稀土元素(Nb、Ta、Ti),来源于与俯冲作用有关的富集岩石圈地幔,是在石榴石稳定域含金云母二辉橄榄岩低程度部分熔融的产物。岩墙群呈东西向平行展布,指示该区域中新世处于南北向伸展背景,可能是撕裂的印度大陆岩石圈板片局部地区发生断离,软流圈上涌,导致富集印度岩石圈地幔源区部分熔融的产物。Post-collisional mantle-derived magmas serve as the most direct indicators for tracing deep geodynamics and mantle processes.A large-scale lamprophyre dyke swarm has been discovered within the Mesozoic-Cenozoic strata of the Tethys Himalaya,located on the southern side of the Indus-Yarlung suture zone.Zircon U-Pb dating results indicate the intrusion of these dykes occurred between 15 and 10 Ma.Geochemical analyses reveal that these lamprophyres exhibit a moderate SiO_(2)content(50.0%~52.9%),high K_(2)O content(2.30%~4.77%),and high Na_(2)O content(3.04%~4.23%),thus classifying them as calc-alkaline lamprophyres.Additionally,these rocks are characterized by high MgO content(5.64%~7.63%)and Mg^(#)value(70~74),high content of Cr(363×10^(-6)~465×10^(-6)),Co(24.7×10^(-6)~31.2×10^(-6)),Ni(128×10^(-6)~269×10^(-6))and other transition elements,which are indicative of a mantle-derived origin without significant crustal assimilation.The lamprophyres are enriched in large-ion lithophile and light rare earth elements(such as Th,U,Ba,Pb,Nd)but depleted in high field strength elements and heavy rare earth elements(such as Nb,Ta,Ti).Its origin is associated with an enriched lithospheric mantle related to subduction processes and is the product of low-degree partial melting of phlogopite-bearing dipyroxene peridotite within the stability field of garnet.Spatially,the dykes exhibit an E-W parallel orientation,which suggests the existence of a north-south extensional regime in the region during the Miocene.Consequently,these lamprophyres are suggestive of a localized detachment and delamination of the Indian lithospheric plate.Such a process would have likely promoted the asthenospheric upwelling,culminating in partial melting within the enriched mantle source regions of the Indian lithosphere.

关 键 词：特提斯喜马拉雅 中新世 煌斑岩 地球化学 

分 类 号：P588.1[天文地球—岩石学]