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引用本文:严松涛,吴青松,李虎,秦蒙,毛世东,李余生,张勇. 甘孜—理塘蛇绿混杂岩带中段理塘地区混杂岩物质组成及其洋盆演化史[J]. 中国地质, 2021, 48(6): 1875-1895.
YAN Songtao,WU Qingsong,LI Hu,QIN Meng,MAO Shidong,LI Yusheng,ZHANG Yong. Material composition and oceanic basin evolution process of the Litang mélange in the middle part of the Ganzi-Litang ophiolite mélange belt[J]. Geology in China, 2021, 48(6): 1875-1895(in Chinese with English abstract).
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甘孜—理塘蛇绿混杂岩带中段理塘地区混杂岩物质组成及其洋盆演化史
严松涛1, 吴青松1, 李虎1, 秦蒙1, 毛世东2, 李余生3, 张勇4
1.中国地质调查局军民融合地质调查中心, 四川 成都 610000;2.中国地质调查局自然资源综合调查指挥中心, 北京 100032;3.成都理工大学, 四川 成都 610000;4.东华理工大学, 江西 南昌 330000
摘要:
理塘混杂岩位于甘孜-理塘蛇绿混杂岩带中段新龙县-理塘县一带,其内部保存有完整的混杂岩系,包括蛇绿岩残片、洋岛残块、洋内弧残块、复理石建造、裂谷残片、高压变质岩等,是恢复和反演甘孜-理塘洋盆演化的理想地区。在总结前人研究的基础上,结合笔者近年来的研究成果,详细阐述了理塘混杂岩的物质组成、构造环境及形成时代,进一步约束了甘孜-理塘洋盆的时空、性质以及演化历程。LA-ICP-MS锆石U-Pb测年结果表明,甘孜-理塘混杂岩带内蛇绿岩年龄为(346±17)Ma、(286.2±5.1)Ma、(219.5±2.2)Ma、(216.1±2.3)Ma,洋岛年龄为(271±10)Ma、(245.1±1.5)Ma、(211.8±1.8)Ma,在侏罗纪瑞环山组粉砂岩夹层中测得碎屑锆石最新年龄为(196±3)Ma,结合大量的古生物化石鉴定结果,分析认为理塘混杂岩最早的年龄记录可追溯至中泥盆世,最晚可延至早白垩世,是甘孜-理塘洋盆中泥盆世-早白垩世连续演化的记录。综合以上研究成果,笔者还大致建立了甘孜-理塘洋盆晚古生代-中生代的演化过程模式。
关键词:  物质组成  锆石U-Pb年龄  理塘混杂岩  甘孜—理塘蛇绿混杂岩带  洋盆史  地质调查工程
DOI:10.12029/gc20210617
分类号:P587;P597.3
基金项目:中国地质调查局项目(12120115041701)资助。
Material composition and oceanic basin evolution process of the Litang mélange in the middle part of the Ganzi-Litang ophiolite mélange belt
YAN Songtao1, WU Qingsong1, LI Hu1, QIN Meng1, MAO Shidong2, LI Yusheng3, ZHANG Yong4
1.Civil-military Integration Center of Geological Survey, China Geological Survey, Chengdu 610000, Sichuan, China;2.Natural Resources Comprehensive Survey Command Center, China Geological Survey, Beijing 100032, China;3.Chengdu University of Technology, Chengdu 610000, Sichuan, China;4.East China University of Technology, Nanchang 330000, Jiangxi, China
Abstract:
The Litang mélange, in which conserves complete mélange system is developed, including remnant of ophiolite, oceanic island blocks, intra-oceanic arc blocks, flysch formation, remnant of rift, high-ultrahigh pressure belt, is located in the middle part of the Ganzi-Litang ophiolite mélange belt around Xinlong-Litang county town, and is an ideal object for the restoring and inversing of the evolution of the Ganzi-Litang ocean basin. On the basis of previous studies and combined with recent research results, the mineral composition, tectonic environment and formation age of Litang melange are described in detail, which further constrain the space-time, nature and evolution of Ganzi-Litang ocean basin. The results of LA-ICP-MS zircon U-Pb dating show that the age of ophiolite is (346±17)Ma, (286.2±5.1)Ma, (219.5±2.2)Ma, (216.1±2.3)Ma, the age of oceanic island is (271±10)Ma, (245.1±1.5)Ma, (211.8±1.8)Ma, and the latest age of detrital zircon is (196±3)Ma in the siltstone interlayer of Ruihuanshan Formation in Jurassic. Combined with a large number of fossil identification results, the analysis shows that the age of the Litang mélange probably ranges from the Middle Devonian to the Early Cretaceous, indicating that it records the continuous evolution of Ganzi-Litang ocean basin from the Middle Devonian to early Cretaceous. With all the achievement mentioned above, the formation and evolution mode of the Ganzi-Litang ocean basin from the Late Paleozoic to the Mesozoic is approximately established.
Key words:  material composition  zircon U-Pb age  Litang mélange  Ganzi-Litang ophiolite mélange  oceanic basin evolution  geological survey engineering