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首页> 外文期刊>Journal of Asian earth sciences >Temperature and age constraints on the metamorphism of the Tethyan Himalaya in Central Nepal: A multidisciplinary approach
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Temperature and age constraints on the metamorphism of the Tethyan Himalaya in Central Nepal: A multidisciplinary approach

机译：温度和年龄对尼泊尔中部特提斯喜马拉雅山变质的制约：多学科方法

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摘要

Metasediments of Devonian to Triassic age of the Tethyan Himalaya (TH) from several areas in central and western Nepal, between western Dolpo and Marsyandi Valley, were sampled for thenno-metamorphic studies (illite and chlorite "crystallinity", vitrinite reflectance, calcite-dolomite and chlorite-chloritoid geothermometers, K/Ar dating on illite-rich fractions and zircon fission track thermochro-nology). This paper reports, for the first time, the occurrence of chloritoid in the TH out of the range of granite contact aureoles. It also presents the first zircon fission track dating performed on TH metasediments. The peak temperatures of metamorphism have been around 250-300℃, 320-350℃, 330-370℃ and 400-500℃ in the western Dolpo, Hidden Valley, Manang and Marpha areas, respectively. In the Manang and Hidden Valley areas, illite K/Ar data are interpreted as ages of recrystallized K-white micas newly formed during metamorphism at around 25-30 Ma. In the Marpha area, illite K/Ar and zircon fission-track ages (12-15 Ma) are consistent representing cooling ages after metamorphic overprinting of higher grade than in the other areas. The joint investigation of the organic maturation and zircon FT chronology yields insight on the thermal calibration of zircon reset. The R_(max) of 5.7% to ～8.0% indicates a temperature range of ca. 315-325℃ which is in the partial annealing zone of the zircon FT thermochronometer. Our results might be explained by the presence of a thick thrust sheet once existing above the study area.
机译：从尼泊尔中部和西部几个地区的特提斯喜马拉雅山（TH）的泥盆纪至三叠纪时代的变质沉积样品，进行了Donpomorphism研究（伊利石和绿泥石的“结晶度”，镜质体反射率，方解石-白云石）以及亚氯酸盐类盐酸盐地热仪，富含伊利石馏分的K / Ar和锆石裂变径迹热色谱技术）。本文首次报道了在花岗岩接触性金矿的范围之外，TH中存在类胡萝卜素。它还介绍了对TH沉积物进行的首次锆石裂变径迹测年。在Dolpo西部，Hidden Valley，Manang和Marpha地区，变质的峰值温度分别约为250-300℃，320-350℃，330-370℃和400-500℃。在Manang和Hidden Valley地区，伊利石K / Ar数据被解释为在变质期25-30 Ma左右新形成的再结晶K-白云母的年龄。在Marpha地区，伊利石K / Ar和锆石裂变径迹年龄（12-15 Ma）是一致的，代表了比其他地区更高等级的变质叠印后的冷却年龄。对有机物成熟度和锆石FT年代学的联合研究，使人们对锆石重置的热校准有了深入的了解。 R_（max）为5.7％〜8.0％，表明温度范围约为。锆石FT温度计的部分退火区为315-325℃。一旦研究区域上方存在厚推力板，便可以解释我们的结果。

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