Raman geobarometry of quartz inclusions in eclogitic garnet constrains the metamorphic evolution and exhumation of the Sumdo oceanic slab in Tibet
Raman geobarometry of quartz inclusions in eclogitic garnet constrains the metamorphic evolution and exhumation of the Sumdo oceanic slab in Tibet
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榴辉石榴石中石英包裹体的拉曼地压测量制约了西藏松多洋板的变质演化和折返
DOI：
10.1016/j.gr.2021.05.015
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发表时间：
2021-05
影响因子：
6.1
通讯作者：
Tian Qiu
中科院分区：
文献类型：
--
作者：
Cong Zhang;Thomas Bader;Xiaoyu Liu;Tingting Shen;Zhengqun Xiang;Tian Qiu
由于地幔深处的高密度，俯冲的洋壳很少折返到地球表面，这使得确定洋壳的演化和动力学行为具有挑战性。松多榴辉岩变质带位于西藏拉萨南北地体之间，是研究洋相榴辉岩变质演化的天然实验室。我们将相平衡模型与该带新发现的西朗榴辉岩的详细岩石学研究相结合，获得了 1.84 GPa 下 539 °C 的近峰值变质条件和陡峭的折返 P-T 路径。这些值远低于该带其他区域的公布值。众所周知，高压岩石中密封在石榴石中的石英包裹体可以在折返过程中保留残余压力，这可以用来重新检查松多变质带榴辉岩的峰值变质条件。我们利用激光拉曼显微光谱分析了该带中三个不同区域（包括西朗、吉朗和辛达多）的石英。西朗榴辉岩保存了石英稳定场中最高的残余压力，为0.53±0.07 GPa。对不同榴辉岩残余压力的系统比较表明，控制残余压力的不仅是峰值变质条件，还有围岩的折返速率。因此，西朗榴辉岩可能记录了较低的峰值 P-T 条件，因为它的折返方式与 Sumdo 变质带其他地区的榴辉岩不同。结合数值模拟，拉曼光谱获得的残余压力可能成为除同位素研究之外比较榴辉岩变质条件、获取年代学信息的新途径。
Due to the high density at mantle depths, subducted oceanic crust rarely exhumes to the surface of Earth, making it challenging to determine the evolution and dynamic behavior of oceanic crust. The Sumdo eclogite-bearing metamorphic belt, located between the north and south Lhasa terranes in Tibet, is a natural laboratory for studying the metamorphic evolution of oceanic eclogites. We combined phase equilibrium modeling with detailed petrological investigations for the newly discovered Xilang eclogite from this belt and obtained near-peak metamorphic conditions of 539 °C at 1.84 GPa and a steep exhumation P–T path. These values are much lower than published for the other areas of this belt. Quartz inclusions sealed in garnet from high-pressure rocks are known to preserve residual pressures during exhumation, which can be used to reexamine the peak metamorphic conditions of eclogites in the Sumdo metamorphic belt. We analyzed quartz from three different areas in the belt, including Xilang, Jilang, and Xindaduo, with laser Raman micro spectroscopy. Xilang eclogite preserved the highest residual pressure of 0.53 ± 0.07 GPa in the quartz stability field. A systematic comparison of the residual pressures of different eclogites revealed that not only the peak metamorphic conditions but also the exhumation rate of the host rocks controlled the residual pressure. Hence, the Xilang eclogite may record lower peak P–T conditions, because it exhumed differently than the eclogites from the other areas in the Sumdo metamorphic belt. Combined with numerical modeling, the residual pressures obtained by Raman spectroscopy may be a new way to compare the metamorphic conditions of eclogites and to obtain geochronological information in addition to isotopic investigations.
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影响因子：
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DOI：
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发表时间：
2015
期刊：
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影响因子：
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DOI：
10.1130/2007.2433(02
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影响因子：
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