Protoliths and metamorphism of the central Himalayan eclogites: Zircon/titanite U–Pb geochronology, Hf isotope and geochemistry
Protoliths and metamorphism of the central Himalayan eclogites: Zircon/titanite U–Pb geochronology, Hf isotope and geochemistry
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喜马拉雅中部榴辉岩的原岩和变质作用：锆石/钛矿 U-Pb 年代学、Hf 同位素和地球化学
DOI：
10.1016/j.gr.2021.10.014
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发表时间：
2021-10
影响因子：
6.1
通讯作者：
Zhang Liangliang
中科院分区：
文献类型：
--
作者：
Dong Xin;Zhang Zeming;Tian Zuolin;Niu Yaoling;Zhang Liangliang
喜马拉雅山中部的高压榴辉岩为研究青藏高原地壳物质的变质作用和折返历史提供了重要资料。由于暴露程度较低，榴辉岩的原岩和变质作用的性质和时间仍然知之甚少。本文报道了喜马拉雅山中部Thongmön和Kharta地区榴辉岩的锆石和钛铁矿U-Pb年龄、岩石和矿物成分以及锆石Hf同位素数据。榴辉岩在>1.6 GPa时记录了高压榴辉岩相变质作用的峰值，高温-超高温（HT-UHT）麻粒岩相叠加（约1.5 GPa）。0.88-0.99 GPa和875-920 °C），以及随后的减压-冷却退变质作用（约。0.42-0.62 GPa和800-820 °C）。地球化学数据表明，榴辉岩原岩是最一致的海底拉斑玄武岩与E-MORB签名。榴辉岩的继承岩浆锆石核测得其原岩年龄为450 Ma，εHf（t）值为+3.2 ~+7.0。变质增生地幔或部分锆石边记录了早期减压麻粒岩相变质阶段（17.9- 15.3Ma），其他变质增生边和变质生长锆石反映了晚期减压冷却退变质阶段（14.8- 13.3Ma）。钛铁矿U-Pb年龄（~ 15.4Ma）进一步指示了后期退变质作用的开始。所有这些数据和观察允许的建议，相对于超高压（UHP）榴辉岩在喜马拉雅西部，高压榴辉岩在喜马拉雅中部记录了印度大陆地壳的长期埋藏和相对缓慢的折返，因为最初的印度-亚洲碰撞在1.55亿年。
The high-pressure (HP) eclogites in the central Himalaya provide insights into the metamorphism and exhumation history of crustal material beneath the Tibetan plateau. Due to the paucity of exposure, the nature and timing of the protolith and metamorphism of the eclogites remain poorly known. Here we report zircon and titanite U–Pb ages, bulk-rock and mineral compositions and zircon Hf isotope data on the eclogites from the Thongmön and Kharta areas in the central Himalaya. The eclogites record peak HP eclogite-facies metamorphism at >1.6 GPa, high-temperature to ultrahigh-temperature (HT-UHT) granulite-facies overprinting (ca. 0.88–0.99 GPa and 875–920 °C), and subsequent decompression-cooling retrograde metamorphism (ca. 0.42–0.62 GPa and 800–820 °C). Geochemical data suggest that the eclogite protoliths are most consistent with being seafloor tholeiitic basalts with an E-MORB signature. Inherited magmatic zircon cores from the eclogites give a protolith age of ∼450 Ma and εHf(t) values of + 3.2 to + 7.0. Metamorphic overgrown mantles or some rims of zircon record an early decompression granulite-facies metamorphic stage (∼17.9–15.3 Ma); other metamorphic overgrown rims and metamorphic growth zircons reflect later decompression-cooling retrograde metamorphic stage (∼14.8–13.3 Ma). The titanite U–Pb age (∼15.4 Ma) further indicates the beginning of the later retrograde metamorphism. All these data and observations allow the proposal that in contrast to the ultrahigh-pressure (UHP) eclogites in the western Himalaya, the HP eclogites in the central Himalaya record the long-lived burial and relatively slow exhumation of the Indian continental crust since initial Indo-Asia collision at ∼55 Ma.
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影响因子：
2.9
作者：
J. Chakungal;J. Dostal;D. Grujic;S. Duchêne;K. S. Ghalley
通讯作者：
J. Chakungal;J. Dostal;D. Grujic;S. Duchêne;K. S. Ghalley
影响因子：
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作者：
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通讯作者：
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影响因子：
3.4
作者：
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通讯作者：
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影响因子：
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作者：
Hua Xiang;J. Connolly
通讯作者：
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影响因子：
3.9
作者：
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通讯作者：
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