甘孜-理塘蛇绿混杂岩带中段洋岛型岩石组合的发现及其对构造演化的指示意义
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本文为国家地质矿产评价项目(编号12120115041701)资助的成果。


The discovery of the ocean island rock association in the middle part of the Ganzi- Litang Ophiolite Mélange Belt and its implication for tectonic evolution
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    摘要:

    甘孜-理塘蛇绿混杂岩带位于西南“三江”多岛弧盆系东缘,是研究古特提斯洋发展演化的重要组成部分,一直备受地质学者瞩目。本文以甘孜-理塘蛇绿混杂岩带中段新龙-理塘地区新发现的大量洋岛型岩石组合为研究对象,通过对其岩石组合以及沉积特征分析将研究区不同类型洋岛型岩石组合依次划分为台地相村戈岩组、斜坡相达森隆洼岩组、坡脚相阿达隆岩组。通过同位素年代学和古生物化石研究表明研究区洋岛型岩石组合的形成时代从早二叠世到晚三叠世均有分布,暗示甘孜-理塘洋盆在早二叠世时期就已存在成熟洋壳,并且洋岛火山活动一直持续至晚三叠世。根据不同类型洋岛型岩石组合的分布特征以及变质变形上的差异,推测甘孜-理塘蛇绿混杂岩带中段新龙-理塘地区洋岛残片不应该归属于单个古洋岛,而应是不同时期、不同古洋岛相继俯冲、消减和就位后的残片。该项研究进一步丰富了甘孜-理塘蛇绿混杂岩带的演化内容,为正确认识甘孜-理塘洋盆构造演化过程提供新的资料和证据。

    Abstract:

    The Ganzi- Litang ophiolite mélange belt is located in the eastern section of the ‘Three- River’ archipelagic arc basin system in southwest China. Geologists have paid close attention to this region with a view to study the development and evolution of the paleo- Tethys ocean. This study conducted detailed research on the rock assemblages and sedimentary characteristics of the ocean island rock association from the Xinlong- Litang area in the middle part of the Ganzi- Litang Ophiolite Mélange Belt. The different types of oceanic island rock assemblages in the study area are divided into the Cunge Formation with platform facies, the Dasenlongwa Formation with slope facies, and the Adalong Formation with slope foot facies. Isotope chronology and paleontological studies show that the formation age of the oceanic island- type rock assemblages in the study area extends from the Early Permian to the Late Triassic, suggesting that the Ganzi- Litang ocean basin existed as a mature ocean in the Early Permian, and the volcanic activity continued into the late Triassic. Based on the distribution characteristics of different types of oceanic island rock assemblages and differences in metamorphic deformation, it is inferred that the oceanic island debris found in the Xinlong- Litang area in the middle part of the Ganzi- Litang ophiolite melange belt could not belong to a single ancient oceanic island, but is the debris after subduction and emplacement of different ancient oceanic islands at different times. The results achieved by the authors have significantly advanced the study of the evolution of the Ganzi- Litang ophiolite mélange belt by providing new data and evidence for the accurate understanding of the tectonic evolution process in the Ganzi- Litang oceanic basin.

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严松涛,谭昌海,段阳海,李虎.2020.甘孜-理塘蛇绿混杂岩带中段洋岛型岩石组合的发现及其对构造演化的指示意义[J].地质学报,94(2):439-449.
YAN Songtao, TAN Changhai, DUAN Yanghai, LI Hu.2020. The discovery of the ocean island rock association in the middle part of the Ganzi- Litang Ophiolite Mélange Belt and its implication for tectonic evolution[J]. Acta Geologica Sinica,94(2):439-449.

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  • 收稿日期:2018-12-10
  • 最后修改日期:2019-02-26
  • 录用日期:2019-04-18
  • 在线发布日期: 2019-04-18