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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >118-115 Ma magmatism in the Tethyan Himalaya igneous province: Constraints on Early Cretaceous rifting of the northern margin of Greater India
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118-115 Ma magmatism in the Tethyan Himalaya igneous province: Constraints on Early Cretaceous rifting of the northern margin of Greater India

机译：在Tethyan Himalaya Igneous省118-115 Ma Magmatism：在更大印度北边缘的早期白垩纪河流的限制

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Understanding the dynamics of Large Igneous Provinces (LIPs) is critical to deciphering processes associated with rupturing continental lithosphere. Microcontinental calving, the rifting of microcontinents from mature continental rifted margins, is particularly poorly understood. Here we present new insights into these processes from geochronological and geochemical analyses of igneous rocks from the Tethyan Himalaya. Early Cretaceous mafic dikes are widely exposed in the eastern and western Tethyan Himalaya, but no such rocks have been reported from the central Tethyan Himalaya. Here we present an analysis of petrological, geochronological, geochemical, and Sr-Nd-Hf-Os isotopic data for bimodal magmatic rocks from the center-east Tethyan Himalaya. Zircon U-Pb dating yields six weighted-mean concordant Pb-206/U-238 ages of 118 +/- 1.2 to 115 +/- 1.3 Ma. Mafic rocks display MORB-like compositions with flat to depleted LREE trends, and positive epsilon(Nd)(t) (+2.76 to +5.39) and epsilon(Hf)(t) (+8.0 to +11.9) values. The negative Nb anomalies and relatively high Os-187/Os-188 ratios (0.15-0.19) of these rocks are related to variable degrees (up to 10%) of crustal contamination. Geochemical characteristics indicate that mafic rocks were generated by variable degrees (2-20%) of partial melting of spinel lherzolites in shallow depleted mantle. Felsic rocks are enriched in Th and LREE, with negative Nb anomalies and decoupling of Nd (epsilon(Nd)(t) = -13.39 to -12.78) and Hf (epsilon(Hf)(t) = -4.8 to -2.0), suggesting that they were derived mainly from garnet-bearing lower continental crust. The geochemical characteristics of the bimodal magmatic associations are comparable to those of associations that form in a continental rift setting. Results indicate that Early Cretaceous magmatism occurred across the whole Tethyan Himalaya, named here as the "Tethyan Himalaya igneous province". Separation of the Tethyan Himalaya from the Indian craton may have occurred during ongoi
机译：了解大火宗省（嘴唇）的动态对与大陆岩石破裂相关的解密过程至关重要。微加管，从成熟的大陆裂泥边缘中的微观阴性越来越多，特别是理解。在这里，我们从Tethyan Himalaya的火成岩的地理学和地球化学分析中提出了新的洞察。早期的白垩纪MAFIC DICKES在东部和西部的Tethyan Himalaya中广泛暴露，但没有从Tethyan Himalaya中据报道这样的岩石。在这里，我们展示了来自中心东Tethyan Himalaya的双峰岩石岩石的岩浆物质，地理学，地球化学和SR-ND-HF-OS同位素数据。锆石U-PB约会产生六种加权平均交作PB-206 / U-238岁118 +/- 1.2至115 +/- 1.3 mA。 MAFIC岩石展示了Morb样组合物，平面为耗尽的嗜好的嗜睡趋势，ε（Nd）（t）（+2.76至+ 5.39）和ε（hf）（t）（+8.0至+11.9）值。这些岩石的阴性Nb异常和相对高的OS-187 / O-188比率（0.15-0.19）与地壳污染的可变度（最多10％）有关。地球化学特征表明，镁岩岩石由浅耗尽碎屑中尖晶石Lherzolites的部分熔化产生的可变性度（2-20％）产生。肠岩在Th和Lree中富集，具有阴性Nb异常和Nd的去耦（ε（nd）（t）= -13.39至-12.78）和hf（ε（hf）（t）= -4.8至-2.0），建议它们主要来自石榴石较低的大陆地壳。双峰岩石关联的地球化学特征与在大陆裂口环境中形成的关联的相互作用。结果表明，整个Tethyan Himalaya发生了早期的白垩纪岩浆广告，这里将在这里命名为“Tethyan Himalaya Igneous省”。在印度克拉顿的Tethyan Himalaya的分离可能已经发生在ongoi期间

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