| 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 |
| 投稿时间：2024-06-25 修订日期：2025-02-10 点此下载全文 |
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| 基金项目:国家自然科学基金项目（41602122, 42172103）、深地专项课题（2024ZD1001005）、中国地质调查局项目（DD20230024, DD20230315）、西藏自治区科技计划项目（XZ202401YD0006、XZ202403ZY0040）、湖北省自然科学基金项目（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(HBREGKFJJ-202302)、地质过程与矿产资源国家重点实验室科技部专项经费（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年龄为245.1 ± 2.5 Ma（n = 4，MSWD = 0.26）和250.6 ± 1.3 Ma （n = 3, MSWD = 0.15），形成于三叠纪。岩石SiO2含量为45.24 wt% ~ 52.86 wt%，K2O含量为2.42 wt% ~ 3.60 wt%, MgO含量为3.16 wt% ~ 6.22 wt%，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（＞7.5）、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，可能起源于地幔物质部分熔融。该玄武岩形成于板内环境，代表了于龙木错—双湖洋盆闭合后的幔源岩浆活动。其捕获锆石保留了大量太古代—前寒武纪年龄信息，获得2512 Ma、1816 Ma、1277 ~ 1019 Ma、800 Ma、558 Ma、420 Ma和340 Ma等多期岩浆-热事件年龄，暗示南羌塘微地块存在早前寒武纪古老陆壳卷入。这些古老陆壳记录了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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| U-Pb dating and geochemistry of the Suorika basalt in the South Qiangtang Terrane: implications for Triassic tectono-magmatic evolution and unexposed crust |
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| Abstract:To better understand the Triassic collision between the southern Qiangtang and northern Qiangtang blocks, we present laser ablation-inductively plasma–mass spectrometry (LA-ICP-MS) zircon U-Pb dating and whole-rock major-trace elemental analyses for the Suorika basalt. The basalt samples yielded zircon U-Pb ages at ca. 245 Ma, and exhibited SiO2 contents ranging from 45.24 wt% to 52.86 wt%, K2O contents ranging from 2.42 wt% to 3.60 wt%, MgO contents ranging from 3.16 wt% to 6.22 wt%, and Mg# values from 51 to 60, suggesting that they belong to shoshonitic and calc-alkaline basalt series. They are characterized by high Ti/V (28 to 31) and Zr/Y (＞7.5) ratios, enrichment of LREE with (LREE/HREE)N=15.44 to 19.96 and no Eu anomaly, low Nb/La ratios (＜1), and depletion of Nb and Ta. They are considered to be continental basalt, probably generated by the partial melting of mantle. They are formed within the intraplate setting following the closure of the Longmucu-Shuanghu ocean. Xenocrystic zircons from the Suorika basalt recorded multiple magmatic events at 2512 Ma, 1816 Ma, 1277 to 1019 Ma, 800 Ma, 558 Ma, 420 Ma, 340 Ma. We infer that Precambrian crust was involved in the South Qiangtang block, and might be involved in the evolution of Columbia, Rodinia, and Gondwana supercontinents. |
| keywords:Basalts Geochemistry Zircon U-Pb age LA-ICP-MS Ancient crust South Qiangtang |
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