| 南羌塘索日卡地区三叠纪玄武岩锆石U-Pb年龄、地球化学特征及其地质构造意义 |
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| 引用本文：陈云,陈冲,季长军,朱江,刘锦明,周连凤,王雅萍.2025.南羌塘索日卡地区三叠纪玄武岩锆石U-Pb年龄、地球化学特征及其地质构造意义[J].地球学报,46(3):506-518. |
| DOI：10.3975/cagsb.2025.021422 |
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| 基金项目:国家自然科学基金项目(编号: 41602122; 42172103; U24A20597)、国家重大科技专项计划深地专项(编号: 2024ZD1001005)、中国地质调查局项目(编号: DD20230024; DD20230315)、西藏自治区科技计划项目(编号: XZ202401YD0006; XZ202403ZY0040)、湖北省自然科学基金项目(编号: 2023AFD206; 2023AFD230; 2024AFD401)、资源与生态环境地质湖北省重点实验室开放基金资助项目(编号: HBREGKFJJ-202302; HBREGKFJJ-202403)和地质过程与矿产资源国家重点实验室科技部专项经费(编号: GPMR202424) |
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| 中文摘要:三叠纪是羌塘地块构造转折的关键时期。为深入理解三叠纪南、北羌塘微地块拼合造山及洋陆演化, 本文对南羌塘地区中央造山带南侧索日卡玄武岩开展了LA-ICP-MS锆石原位U-Pb同位素测年和岩石地球化学研究。索日卡玄武岩的锆石U-Pb加权平均年龄为(245.1±2.5) Ma(n=4, MSWD=0.26)和(250.7±2.9) Ma(n=3, MSWD=0.06), 形成于三叠纪。岩石SiO2含量为45.2%~52.9%, K2O含量为2.42%~3.60%, MgO含量为3.16%~6.22%, 属于钾玄岩系列和钙碱性玄武岩系列。岩石具有高Ti/V比值(28~31)和Zr/Y比值(>7.53), Eu异常不明显, 亏损Nb、Ta和低Nb/La比值(<1)特征。索日卡玄武岩具有大陆玄武岩特征, 可能形成于板内环境, 代表了龙木错—双湖洋盆闭合后的幔源岩浆活动。玄武岩的捕获锆石保留了大量前寒武纪年龄信息, 获得2 512 Ma、1 816 Ma、1 277~1 019 Ma、800 Ma、558 Ma、420 Ma和340 Ma等多期岩浆-热事件年龄, 揭示南羌塘微地块卷入了一些早前寒武纪古老陆壳物质。这些古老陆壳物质记录了Columbia、Rodinia和Gondwana超大陆等全球性演化相关的前寒武纪构造-岩浆-热事件信息。 |
| 中文关键词:玄武岩 地球化学 锆石U-Pb年龄 LA-ICP-MS 古老陆壳物质 南羌塘 |
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| Zircon U-Pb Ages, Geochemistry, and Tectonic Significances of the Triassic Suorika Basalts in the Southern Qiangtang Terrane |
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| Abstract:The Triassic period marks a pivotal era for the tectonic transformation of the Qiangtang block. To gain a deeper understanding of the amalgamation and orogeny of the South and North Qiangtang micro-blocks during the Triassic, as well as the evolution of the ocean and continent, this study conducted LA-ICP-MS zircon in-situ U-Pb isotopic dating and petrochemical analysis on the basalts from the southern side of the central orogenic belt in the South Qiangtang region, specifically the Sorika basalts. The basalt samples yielded zircon U-Pb weighted average ages of (245.1±2.5) Ma and (250.7±2.9) Ma, and exhibited SiO2 contents ranging from 45.2% to 52.9%, K2O contents ranging from 2.42% to 3.60%, MgO contents ranging from 3.16% to 6.22%, and Mg# values of 51–60, suggesting that they belong to the shoshonitic and calc-alkaline basalt series. They are characterized by high Ti/V (28 to 31) and Zr/Y (>7.53) ratios, enrich-ment of LREE with (LREE/HREE)N=15.44 to 19.96 and no Eu anomaly, low Nb/La ratios (<1), and deple-tion of Nb and Ta. They are considered continental basalts, and the basaltic magma was probably gener-ated by partial melting of the mantle within the intraplate setting following the closure of the Long-mucu–Shuanghu Ocean. Xenocrystic zircon gains from the Suorika basalts recorded multiple magmatic events at 2 512 Ma, 1 816 Ma, 1 277 to 1 019 Ma, 800 Ma, 558 Ma, 420 Ma, and 340 Ma. These ancient crustal materials record information related to global Precambrian tectonic-magmatic-thermal events as-sociated with the evolution of supercontinents such as Columbia, Rodinia, and Gondwana. |
| keywords:basalts geochemistry zircon U-Pb age LA-ICP-MS ancient crust southern Qiangtang |
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