An early Eocene magmatic event in southern Tibet triggered by oceanic slab break-off: evidence from ocean island basalt-like mafic rocks
An early Eocene magmatic event in southern Tibet triggered by oceanic slab break-off: evidence from ocean island basalt-like mafic rocks
复制标题
藏南早始新世大洋板片断裂触发的岩浆事件：来自洋岛状玄武岩基性岩石的证据
DOI：
10.1007/s00410-022-01987-6
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发表时间：
2023-01
影响因子：
3.5
通讯作者：
Ming Lei;Jianlin Chen;Dan Wang;Ying Luo;Yi-Xin Liu
中科院分区：
文献类型：
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作者：
Ming Lei;Jianlin Chen;Dan Wang;Ying Luo;Yi-Xin Liu
藏南早新生代岩浆爆发的时间和起源仍然存在争议，主要是因为缺乏稀有的小体积洋岛玄武岩（OIB）样镁铁质岩石的可用数据，可以深入了解这一地质事件。藏南仲巴地区早新生代类OIB玄武岩与这次岩浆爆发密切相关，是深部地幔动力学的响应。本文对中坝玄武岩进行了详细的年代学和地球化学研究。这些Eocene（CA。OIB类玄武岩具有K、Zr、Hf、Ti负异常，低Fe/Mn和高Fe/Zn比值，Sr-Nd-Hf和HIMU类Pb同位素组成均匀富集（87 Sr/86 Sr（i）= 0.7052-0.7053; εNd（t）= − 1.7-− 1.3; εHf（t）= − 1.1-− 0.3; 206 Pb/204 Pb = 19.83-19.87），表明来自碳酸盐橄榄岩。结合区域构造演化，提出中坝玄武岩的碳酸盐橄榄岩源区是亏损洋中脊玄武岩类地幔橄榄岩与俯冲的新特提斯碳酸盐洋壳熔体反应生成的。这种碳酸盐橄榄岩可能保存在岩石圈和软流圈之间的热边界上，并经历了部分熔融，产生了中坝玄武岩，这是新特提斯洋岩石圈板片断裂的反应。52 Ma.板块断裂引发了岩浆爆发和其他地质过程（例如，印度板块的速度下降）在西藏南部始新世。
The timing and origins of the Early Cenozoic magmatic flare-up in southern Tibet remain controversial, mainly because of the lack of available data for the rare, small-volume, ocean island basalt (OIB)-like mafic rocks that can shed insights into this geological event. We have confirmed that Early Cenozoic OIB-like basalts in the Zhongba area, southern Tibet, were closely related to this magmatic flare-up, which occurred in response to deep mantle geodynamics. In this study, we present detailed geochronological and geochemical data for the Zhongba basalts. These Eocene (ca. 52 Ma) OIB-like basalts have negative K, Zr, Hf, and Ti anomalies, low Fe/Mn and high Fe/Zn ratios, and uniform and enriched Sr–Nd–Hf and HIMU-like Pb isotopic compositions (87Sr/86Sr(i)= 0.7052–0.7053; εNd(t)= − 1.7 to − 1.3; εHf(t)= − 1.1 to − 0.3;206Pb/204Pb = 19.83–19.87), indicative of derivation from carbonated peridotite. Based on the regional tectonic evolution, we propose that the carbonated peridotite source of the Zhongba basalts was generated by the reaction between depleted mid-ocean ridge basalt-like mantle peridotite and melts from subducted Neo-Tethys carbonate-bearing oceanic crust. This carbonated peridotite was possibly preserved at the thermal boundary between the lithosphere and asthenosphere and underwent partial melting to produce the Zhongba basalts in response to slab break-off of the Neo-Tethys oceanic lithosphere at ca. 52 Ma. The slab break-off triggered the magmatic flare-up and other geological processes (e.g., a decrease in the velocity of the Indian Plate) in southern Tibet during the Eocene.