The ∼390 Ma high-T metamorphic event in the Chinese Altai: A consequence of ridge-subduction?
The ∼390 Ma high-T metamorphic event in the Chinese Altai: A consequence of ridge-subduction?
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DOI：
10.2475/10.2010.08
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发表时间：
2010-12
影响因子：
2.9
通讯作者：
Yingde Jiang;M. Sun;Guochun Zhao;C. Yuan;W. Xiao;X. Xia;X. Long;Fu-Yuan Wu
中科院分区：
文献类型：
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作者：
Yingde Jiang;M. Sun;Guochun Zhao;C. Yuan;W. Xiao;X. Xia;X. Long;Fu-Yuan Wu
中国阿尔泰地区存在高级岩石，但变质作用的时间限制很差，这阻碍了我们对该地区热构造历史的理解。选取哈纳斯-富蕴硅线石带中具有代表性的高品位样品进行锆石U-Pb定年和温度估算。LA-ICP-MS分析锆石增生边和重结晶域的年龄一致，为1.390 Ma，这是一个区域变质事件的记录。使用角闪石-斜长石-石英（Amp-Pl-Qtz）和石榴石-黑云母（GB）地质温度计估算的温度（T）相对较高，范围为650至700 °C。利用锆石中钛温度计，锆石变质边缘的温度估计为720 °C。这些数据表明，高温变质事件发生在中国阿尔泰在中泥盆世，并可能意味着一个构造环境，涉及异常升高的热通量从深源。我们的数据支持可能的脊俯冲约390 Ma，造成热软流圈的上涌，并引发了高温变质作用。该模型还可以解释阿尔泰造山带同时代火山活动的一系列地球化学特征，不同的镁铁质侵入体和广泛的热液成矿作用。
High-grade rocks occur in the Chinese Altai, but the timing of metamorphism is poorly constrained, which hinders our understanding of the thermo-tectonic history of the region. Representative high-grade samples from the sillimanite zone extending from Hanas to Fuyun were selected for zircon U-Pb dating and temperature estimation. LA-ICP-MS analyses of zircon overgrowth rims and recrystallized domains give consistent ages of ∼390 Ma, which is interpreted to record a regional metamorphic event. Temperature (T) estimations using the amphibole-plagioclase-quartz (Amp-Pl-Qtz) and garnet-biotite (GB) geothermometers give relatively high temperatures ranging from 650 to 700 °C. The zircon metamorphic rims yield temperature estimates of ∼720 °C by using the Ti-in-zircon thermometer. These data suggest that a high-temperature metamorphic event took place in the Chinese Altai in the Middle Devonian, and may imply a tectonic environment involving an unusually elevated heat flux from a deep-seated source. Our data support possible ridge subduction around 390 Ma that caused upwelling of the hot asthenosphere and triggered the high-T metamorphism. This model can also account for coeval volcanic activity with a range of geochemical characteristics, diverse mafic intrusions and extensive hydrothermal mineralization in the Altai orogen.