Geochemical constraints on origin of hydrothermal volatiles from southern Tibet and the Himalayas: Understanding the degassing systems in the India-Asia continental subduction zone
Geochemical constraints on origin of hydrothermal volatiles from southern Tibet and the Himalayas: Understanding the degassing systems in the India-Asia continental subduction zone
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西藏南部和喜马拉雅山热液挥发物起源的地球化学约束：了解印度-亚洲大陆俯冲带的脱气系统
DOI：
10.1016/j.chemgeo.2017.02.023
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发表时间：
2017-10
期刊：
影响因子：
3.9
通讯作者：
Cheng Zhihui
中科院分区：
文献类型：
--
作者：
Zhang Maoliang;Guo Zhengfu;Zhang Lihong;Sun Yutao;Cheng Zhihui
热液活动（例如，青藏高原南部和喜马拉雅地区广泛分布着大量的天然气（包括热泉和间歇泉），形成了一条长约2000 km的东西向热液带，代表了印度-亚洲大陆俯冲带（IACSZ）正在进行的脱气系统。在这项研究中，我们报告了新的数据的化学成分和He-C-N同位素的热液带中的代表性温泉的气体样品，旨在了解挥发性来源的热液脱气系统在IACSZ及其构造意义。根据空间位置，将样品分为西部、中部和东部亚组，其3 He/4 He和CO2/3 He比值等地球化学特征在空间上具有可识别性。挥发性演化所需的基本组成部分包括硅酸盐岩，碳酸盐岩，沉积有机质和幔源端员，这都是预期在IACSZ后的构造模型，包括一个增生楔和岩浆锋。He-C-N同位素混合计算的基础上，再加上岩石地球化学和地球物理研究的限制，富集地幔楔（EMW）提出了作为一个潜在的候选人的来源的幔源成分，这突出了回收的印度大陆材料的重要性相比，以前的模型，不考虑这种可能性地幔源富集的考虑。由硅酸盐岩、碳酸盐岩和沉积有机质组成的区域地壳岩石组合被解释为EMW衍生挥发分的污染物（例如岩浆前缘的脱气系统）或增生楔中脱气系统的热液挥发分的源物质。根据IACSZ的构造框架，我们认为挥发性地球化学的空间变化（例如，3 He/4 He）主要受构造亲合力控制（即，增生楔和岩浆前缘）的热液脱气系统。类似地壳的3 He/4 He比值和高的N2和4 He含量与增生楔（包括喜马拉雅和弧前盆地）中高的沉积对脱气系统的贡献相一致，而藏南高的幔源氦排放则与岩浆前缘下EMW源熔体的贡献密切相关。此外，具有可变规模和穿透深度的区域性断裂系统将作为一个额外的因素，可能会扰动由构造环境控制的3 He/4 He跨IACSZ剖面。我们对藏南和喜马拉雅地区脱气系统的解释可能为理解IACSZ的物质循环机制和构造环境提供来自挥发性地球化学的约束。
Hydrothermal activities (e.g., hot springs and geysers) are extensively distributed in southern Tibet and the Himalayas, forming an east-west trending, ~ 2000-km-long, hydrothermal belt that represents the ongoing degassing systems in the India-Asia continental subduction zone (IACSZ). In this study, we report new data of chemical compositions and He-C-N isotopes for gas samples from representative hot springs in the hydrothermal belt, aimed at understanding volatile origin of the hydrothermal degassing systems in the IACSZ and their tectonic implications. According to spatial location, the samples are divided into western, central and eastern subgroups, which display spatially discernible geochemical characteristics, such as3He/4He and CO2/3He ratios. The essential components required for volatile evolution include silicate rocks, carbonate rocks, sedimentary organic matter and a mantle-derived end-member, which are all expected in the IACSZ following a tectonic model incorporating an accretionary wedge and a magmatic front. On the basis of He-C-N isotope mixing calculations, together with constraints from petrogeochemical and geophysical studies, an enriched mantle wedge (EMW) is proposed as a potential candidate for the source of the mantle-derived components, which highlights the importance of recycled Indian continental materials compared to previous models that do not take this possibility for mantle source enrichment in account. The regional crustal rock assemblages composed of silicate rocks, carbonate rocks and sedimentary organic matter are interpreted as contaminants of the EMW-derived volatiles (as exemplified by degassing systems in the magmatic front) or as source materials of hydrothermal volatiles from degassing systems in the accretionary wedge. Following tectonic framework of the IACSZ, we suggest that spatial variations in volatile geochemistry (e.g.,3He/4He) are predominantly controlled by tectonic affinities (i.e., the accretionary wedge and magmatic front) of the hydrothermal degassing systems in southern Tibet and the Himalayas. The crustal-like3He/4He ratios and high N2and4He contents agree well with the high sedimentary contributions to degassing systems in the accretionary wedge (including the Himalayas and fore-arc basins), whereas the high mantle-derived helium emissions in southern Tibet exhibit close affinities with contributions from the EMW-derived melts beneath the magmatic front. Moreover, regional fault systems with variable scales and depths of penetration would act as an extra factor that may perturb the across-IACSZ profile of3He/4He ratios controlled by tectonic settings. Our interpretation on degassing systems in southern Tibet and the Himalayas may have the potential to provide constraints from volatile geochemistry for understanding material recycling mechanism and tectonic settings of the IACSZ.
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DOI：
10.1007/978-3-319-78527-1
发表时间：
1973
期刊：
Stable Isotope Geochemistry
影响因子：
--
作者：
J. Hoefs
通讯作者：
J. Hoefs
影响因子：
3.4
作者：
J. Mabry;T. Lan;P. Burnard;B. Marty
通讯作者：
J. Mabry;T. Lan;P. Burnard;B. Marty
影响因子：
3.4
作者：
Y. Sano;J. Hirabayashi;Takeshi Oba;T. Gamo
通讯作者：
Y. Sano;J. Hirabayashi;Takeshi Oba;T. Gamo
影响因子：
4.6
作者：
Kagoshima T;Sano Y;Takahata N;Maruoka T;Fischer TP;Hattori K
通讯作者：
Hattori K
影响因子：
5.8
作者：
A. Draut;P. Clift
通讯作者：
A. Draut;P. Clift