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

发布时间：2019-05-29 08:02

【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~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Pb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。
[Abstract]:A large number of diabase / wall distributed near east-west direction are developed in the eastern Jiangzi-Kangma area of the Tethys Himalayan belt. The results show that these basic rocks can be divided into at least three stages: (1) the diabase formed in ~ 140Ma has the characteristics of OIB type geochemistry. The Sr-Nd isotopic composition of some samples is similar to that of the basic rocks in the eastern part of the 132Ma Shanmei-Banbury diagenetic province. Some of the high magnesium samples have negative Nb-Ta anomalies and positive Pb anomalies, and the 蔚 Nd (t) value is less than 0. (2) the diabase formed in ~ 120Ma shows the geochemical characteristics of N-MOB type, and (3) the diabase formed in ~ 90Ma shows the geochemical characteristics of E-MOB type. The Sr-Nd isotopic composition of the latter two basic rocks is related to MORB in the Indian Ocean. The active track of Kerguelen mantle plume and the cracking event of East Gondane continent during the contract period. It is considered in this paper that the 140Ma basic rocks in Jiangzi-Kangma area represent the Kerguelen mantle plume and its interaction with the lithosphere mantle of the overlying East Gondwane continent. It is the evidence that Kerguelen mantle plume lurks under East Gondane continent for a long time. On the basis of previous studies, the influence range of this mantle plume has been expanded from wrong beauty to west about 200 km. After that, with the cracking of East Gondane continent and the opening and expansion of the Indian Ocean, the Indian plate gradually moved northward and far away from the Kerguelen mantle plume. The ~ 120Ma and ~ 90Ma basic rocks in Jiangzi-Kangma area represent the products of the partial melting of the new Indian Ocean soft flume circle. It has nothing to do with Kerguelen mantle plume. The three stages of basic magmatic activity identified in this area show that the eastern part of the Tethys Himalayan belt experienced multiple basic magmatic activities related to the cracking of East Gondane continent and the opening and expansion of the Indian Ocean in the Cretaceous. These basic rocks provide new rock records and time coordinates for further understanding and limiting the paleogeographic location and tectonic evolution of the Tethys Himalayan belt since 140Ma.
【作者单位】：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;中国科学技术大学地球与空间科学学院;中国地质科学院矿产资源研究所;中国地质科学院国家地质实验测试中心;
【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
【分类号】：P588.11;P534.53

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