拉萨地块北部孔马地区早白垩世花岗闪长岩地球化学、锆石U-Pb年代学及其构造意义
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P588.12+2;P597.+3

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中国地质调查局项目(DD20240032); 国家自然科学基金项目(42002032)


Geochemistry and zircon U-Pb chronology of the Early Cretaceous granodiorite in Kongma area, northern Lhasa Terrane, and their tectonic significance
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    摘要:

    拉萨地块北部广泛分布白垩纪岩浆岩,其记录的岩浆-变质事件,对于研究拉萨地块白垩纪岩浆岩的岩石成因和构造背景具有重要的意义。本文对拉萨地块北部孔马地区花岗闪长岩进行了岩石学、地球化学和年代学研究,结果表明,研究区花岗闪长岩LA-ICP-MS锆石U-Pb年龄为113.2±1.3 Ma,属早白垩世晚期岩浆作用的产物。该岩体属高钾钙碱性系列,铝饱和指数A/CNK=1.05~1.12,相对富集Rb、Th、U、K等大离子亲石元素,亏损Ti、P、Ta等高场强元素,具有中等Eu负异常,为过铝质S型花岗岩。岩石地球化学特征显示其成岩岩浆主要来自古老地壳的部分熔融,并受到地幔物质混染。结合区域资料,认为孔马地区花岗闪长岩形成于早白垩世晚期班公湖-怒江洋壳南向俯冲碰撞的构造环境,可能与重力拖拽下发生板片断离导致的软流圈物质上涌有关。

    Abstract:

    Cretaceous magmatic rocks are widely distributed in the northern the Lhasa Terrane, and the recorded magmatic-metamorphic events are of great significance for studying the petrogenesis and tectonic setting of Cretaceous magmatic rocks in the Lhasa Terrane. This paper reports the petrology, geochemical results and zircon U-Pb age of the Early Cretaceous granodiorite exposed in the Kongma area located in the northern Lhasa Terrane. The results show that the LA-ICP-MS zircon U-Pb age of granodiorite in the study area is 113.2±1.3 Ma, which belong to the late Early Cretaceous magmatism. These rocks are belong to the high potassium calc-alkaline series, with aluminum saturation index(A/CNK=1.05~1.12) and medium negative Eu anomaly, relatively enriched large ion lithophile elements Rb, Th, U, K, and deficient high field strength elements Ti, P, Ta, which is a peraluminous S-type granite. Geochemical characteristics of the rocks shows that they were originated from the partial melting of the ancient crust with the mixing of mantle materials. Combined with the regional data, it is believed that the granodiorite in the Kongma area was formed in the tectonic environment of the southward subduction collision of the Bangonghu-Nujiang oceanic crust in the late Early Cretaceous, which may be related to the asthenosphere material upsurge caused by the slab break-off under gravity drag.

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李俊,张士贞,刘函,等, 2026. 拉萨地块北部孔马地区早白垩世花岗闪长岩地球化学、锆石U-Pb年代学及其构造意义[J]. 岩石矿物学杂志, 45(1):71~85.
LI Jun, ZHANG Shi-zhen, LIU Han, et al, 2026. Geochemistry and zircon U-Pb chronology of the Early Cretaceous granodiorite in Kongma area, northern Lhasa Terrane, and their tectonic significance[J]. Acta Petrologica et Mineralogica, 45(1): 71~85.

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  • 收稿日期:2025-03-24
  • 最后修改日期:2025-09-20
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  • 在线发布日期: 2026-01-19
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