Unraveling alteration histories in serpentinites and associated ultramafic rocks with magnetite (U-Th)/He geochronology
Unraveling alteration histories in serpentinites and associated ultramafic rocks with magnetite (U-Th)/He geochronology
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利用磁铁矿 (U-Th)/He 地质年代学揭示蛇纹岩和相关超镁铁岩的蚀变历史
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
D. Stockli
中科院分区：
文献类型：
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作者：
E. Cooperdock;D. Stockli
蛇纹石化作用是一个广泛的过程，它影响着沿着板块边界的大尺度地球动力学过程，包括大陆断裂、海底扩张和俯冲。记录蛇纹岩化的时间对于我们理解这些过程至关重要，但直接测定蛇纹岩的年代具有挑战性或不可能。我们提出的第一个应用磁铁矿（U-Th）/He测年的超镁铁岩的蚀变和冷却阶段。为了证明磁铁矿的可行性，他在这些岩性定年，磁铁矿年龄获得两个超镁铁质岩性的坎波斯混杂岩带，高压低温俯冲复杂的锡罗斯岛，希腊。磁铁矿（U-Th）/He测量的内部碎片从大颗粒内的一个榴辉岩和蛇纹岩记录中新世剥露相关的冷却年龄，而较小的颗粒蛇纹岩记录矿物生长与热液流体流沿着上新世正断层。这些年龄结果与磁铁矿微量元素地球化学揭示了多幕流体岩石蚀变的证据，这对冷却历史和局部地球化学交换的高压-低温热液。该方法为研究不同构造背景下蛇纹石化的过程和时间尺度提供了一种新的工具。
Serpentinization is a widespread process that affects large-scale geodynamic processes along plate boundaries, including continental breakup, seafloor spreading, and subduction. Documenting the timing of serpentinization is critical for our understanding of these processes, but direct dating of serpentinites has been challenging or impossible. We present the first application of magnetite (U-Th)/He chronometry to date stages of alteration and cooling in ultramafic rocks. In order to demonstrate the viability of magnetite He dating in these lithologies, magnetite ages were obtained from two ultramafic lithologies of the Kampos melange belt, a high-pressure–low-temperature subduction complex on the island of Syros, Greece. Magnetite (U-Th)/He measurements of internal fragments from large grains within a chlorite schist and a serpentinite record Miocene exhumation-related cooling ages, whereas smaller grains from the serpentinite record mineral growth associated with hydrothermal fluid flow along Pliocene normal faults. These age results with magnetite trace element geochemistry reveal evidence for multiple episodes of fluid-rock alteration, which has implications for the cooling history and local geochemical exchanges of this high-pressure–low-temperature terrane. This method provides a new tool that may be expanded to investigate the processes and time scales of serpentinization from a variety of tectonic settings.
影响因子：
5.8
作者：
Klein, Frieder;Bach, Wolfgang;Berquo, Thelma S.
通讯作者：
Berquo, Thelma S.