藏南特提斯喜马拉雅带内江孜-康马地区白垩纪多期基性岩浆作用  

Multiple phases of cretaceous mafic magmatism in the Gyangze-Kangma area,Tethyan Himalaya,southern Tibet

作　　者：王亚莹[1] 高利娥[1] 曾令森[1] 陈福坤[2] 侯可军[3] 王倩[3] 赵令浩[4] 高家昊 

机构地区：[1]中国地质调查局大陆构造与动力学创新研究中心,中国地质科学院地质研究所,北京100037 [2]中国科学技术大学地球与空间科学学院,合肥230026 [3]中国地质科学院矿产资源研究所,北京100037 [4]中国地质科学院国家地质实验测试中心,北京100037

出　　处：《岩石学报》2016年第12期3572-3596,共25页Acta Petrologica Sinica

基　　金：公益性行业科研专项(201511022);国家自然科学基金项目(41425010;41503023);中国地质调查项目(12120115027101)联合资助

摘　　要：在特提斯喜马拉雅带东部江孜-康马一带发育大量近东西向展布的辉绿岩体／墙，研究表明这些基性岩至少可分为三期：（1）形成于-140Ma的辉绿岩具有OIB型地球化学特征，部分样品Sr—Nd同位素组成与其东部一132Ma错美．班布里大火成岩省中基性岩相当，部分高镁样品具有Nb-Ta负异常和Ph正异常，εNd（t）值小于0；（2）形成于～120Ma的辉绿岩显示N—MORB型地球化学特征；（3）形成于～90Ma的辉绿岩显示E—MORB型地球化学特征。后两期基性岩的Sr-Nd同位素组成均显示与印度洋MORB相关。结合同时期的Kerguelen地幔柱活动轨迹及东冈瓦纳大陆裂解事件，本文认为江孜-康马地区～140Ma基性岩代表Kerguelen地幔柱及其与上覆东冈瓦纳大陆岩石圈地幔相互作用产物，是Kerguelen地幔柱长期潜伏于东冈瓦纳大陆下的证据，在前人研究基础上将该地幔柱影响的范围从错美向西拓展了约200km；之后随着东冈瓦纳大陆裂解和印度洋的开启及扩张，印度板块逐渐北移并远离Kerguelen地幔柱，江孜-康马地区～120Ma和～90Ma两期基性岩代表新生印度洋软流圈部分熔融的产物，与Kerguelen地幔柱无关。该区识别出的三期基性岩浆活动表明：特提斯喜马拉雅带的东部在白垩纪经历了与东冈瓦纳大陆裂解、印度洋的开启和扩张相关的多期基性岩浆活动。这些基性岩为深入了解和限定特提斯喜马拉雅带自140Ma以来的古地理位置和构造演化过程提供了新的岩石记录和时间坐标。A large number of E-W trending subparallel diabases occurred in the Gyangze-Kangma area, eastern Tethyan Himalaya, southern Tibet. Results from field observation, zircon U-Pb dating, whole-rock geochemical and Sr-Nd isotopic data indicate that they represent at least three episodes of Cretaceous mafic magmatism within the Tethyan Himalaya at ~ 140Ma, - 120Ma, and ~ 90Ma, respectively. （ 1 ） The T0907 suite, occurred at 142. 0 ＋ 1.4Ma, is characterized by OIB-like trace element patterns and Sr-Nd isotopic compositions, similar to those in the - 132Ma Comei-Bunbury Large Igneous Province to the east. However, the contemporaneous T0902 suite shows elevated Mg, Cr and Ni contents, but Nb-Ta negative anomalies, Pb positive anomalies and negative εNd （t） values, which could be derived from an enriched lithospheric source; （2） The T0904 suite, formed at 121.1 ± 0.7Ma, displays N-MORB-like geochemical characteristics; （3） The TO901 suite, formed at 90Ma, displays E-MORB-like geochemical characteristics. Combined with the evolutional history of the breakup of the East Gondwana continent and the hotspot track of the Kerguelen mantle plume, we suggest that the mafic magmatism at -140Ma in Gyangze-Kangma area represents the products from interaction between the Kerguelen mantle plume and the overlying East Gondwana continental lithospheric mantle, possibly due to relatively long-time incubation of the Kerguelen mantle plume beneath the East Gondwana supercontinent. However, with the breakup of the East Gondwana continent and the initiation and spreading of the Indian oceanic ridge, the Indian continent started to drift away from the Kerguelen hotspot. Mafic magmatism at ~ 120Ma and ~ 90Ma in this studied area represent the products formed by partial melting of asthenosphere mantle under Indian ridges, rather than the products of Kerguelen mantle plume. Data presented above indicates that mafic rocks within the Himalayan terrane were produced by multiple episodes of magmatism associated with the breakup o

关 键 词：特提斯喜马拉雅 基性岩浆作用 Kerguelen地幔柱 大火成岩省 

分 类 号：P588.124[天文地球—岩石学] P597.3[天文地球—地质学]