| 广西崇左三叠系北泗组火山岩锆石U-Pb年龄、Hf同位素和地球化学特征——对古特提斯演化的指示 |
| 点此下载全文 |
| 引用本文：张鲲,李剑锋,程顺波,李堃,鲍波,刘阿睢,夏杰.2026.广西崇左三叠系北泗组火山岩锆石U-Pb年龄、Hf同位素和地球化学特征——对古特提斯演化的指示[J].地球学报,47(3):613-628. |
| DOI：10.3975/cagsb.2025.090521 |
| 摘要点击次数: 374 |
| 全文下载次数: 33 |
|
| 基金项目:本文由中国地质调查局地质调查项目(编号: DD20242336; DD20221689)资助。 |
|
| 中文摘要:崇左六汤地区北泗组流纹岩、英安岩为同期出露的最北端火山岩, 本文获得其高精度LA-ICP-MS锆石U-Pb年龄分别为(247.8±1.4) Ma、(248.0±1.4) Ma; 统计显示桂西南北泗组、板八组火山岩形成于240~ 248 Ma、248~250 Ma, 同为早—中三叠世构造岩浆活动的产物。岩石地球化学分析表明, 北泗组火山岩整体具有高SiO2、全碱(Na2O+K2O)含量, 极低的MgO、MnO、CaO含量; 流纹岩、英安岩稀土配分曲线均为右倾轻稀土富集型, 具明显铕负异常(δEu=0.14~0.16、0.16~0.18); 富集Rb、K、Th、U、Nd, 亏损Ba、Sr、P、Nb、Ta、Ti等元素。Hf同位素研究显示流纹岩εHf(t)= –14.1 ~ –4.4、TDM2=1 553~2 169 Ma, 英安岩εHf(t)= –16.2~ –7.8、TDM2=1 774~2 296 Ma; 均源自古元古代变沉积岩的部分熔融。综合资料, 得出桂西南早—中三叠世火山岩形成于古特提斯洋俯冲背景下的陆缘弧环境的结论; 与富宁—那坡—崇左—凭祥早—中三叠世岛弧火山岩、八布—Cao Bang蛇绿混杂岩带构成洋壳俯冲增生杂岩-弧体系。因此, 六汤地区火山岩限定了古特提斯洋俯冲在桂西南的影响范围与时限。 |
| 中文关键词:锆石U-Pb年龄 地球化学 火山岩 北泗组 崇左 古特提斯 |
| |
| Zircon U-Pb Ages, Hf Isotopes, and Geochemical Characteristics of the Triassic Beisi Formation Volcanic Rocks in Chongzuo, Guangxi: Implications for the Evolution of the Paleo-Tethys Ocean |
|
|
| Abstract:The Chongzuo Liutang area exposes the northernmost rhyolite and dacite of the contemporaneous Beisi Formation volcanic rocks. We obtained high-precision LA-ICP-MS zircon U-Pb ages of (247.8±1.4) Ma and (248.0±1.4) Ma for these rocks. Statistical analysis indicates that volcanic rocks of the Beisi and Banba Formations in southwestern Guangxi Province were formed at 240–248 Ma and 248–250 Ma, respectively, which were the products of the Early-Middle Triassic tectonic movement. The geochemical analysis shows that the volcanic rocks of the Beisi Formation comprise high SiO2 and alkali (Na2O+K2O) contents and extremely low MgO, MnO, and CaO contents. The rhyolite and dacite REE contents both exhibit right-inclined LREE enrichment patterns, with δEu values of 0.14–0.16 and 0.16–0.18. Furthermore, they are enriched in Rb, K, Th, U, and Nd contents, and are depleted in Ba, Sr, P, Nb, Ta, and Ti, etc. The Hf isotope study shows that the rhyolites have εHf(t) values ranging from –14.1 to –4.4 and TDM2 values ranging from 1 553 Ma to 2 169 Ma, while the dacites have εHf(t) values ranging from –16.2 to –7.8 and TDM2 values ranging from 1 774 Ma to 2 296 Ma. It can be concluded that the volcanic rocks in this study originated from the partial melting of Paleoproterozoic metasedimentary rocks. Based on a comprehensive study, the Early–Middle Triassic volcanic rocks in southwestern Guangxi are interpreted to have formed in a continental margin arc setting associated with the subduction of the Paleo-Tethys Ocean. These rocks, together with the Early–Middle Triassic island arc volcanic rocks in the Funing–Napo–Chongzuo–Pingxiang area and the Babu–Cao Bang ophiolitic melange belt, constitute an oceanic crust subduction-accretion complex-arc system. Thus, the Liutang area volcanic rocks constrain the spatial extent and temporal limits of Paleo-Tethys oceanic subduction in southwestern Guangxi. |
| keywords:zircon U-Pb age geochemistry volcanic rocks Beisi Formation Chongzuo Paleo-Tethys Ocean |
| 查看全文 查看/发表评论 下载PDF阅读器 |
|
|
|
|
|
