We conducted crystal-fabric analyses of peridotites within the Horoman peridotite complex in the Hidaka metamorphic belt, Hokkaido, Japan. Over fifty oriented peridotite samples were collected and analyzed for olivine fabric strength (J-index) and crystallographic preferred orientations (CPOs). The peridotites contained four olivine CPOs: A, E, D, and AG types. We confirmed that olivine CPOs presented a transitional distribution from E to A to AG type from south to north. Previous experimental studies have demonstrated that E type CPO can merge under hydrous conditions. In addition, magnetotelluric observations suggested that the subducting oceanic plate supplies pore fluid to the basal thrust in the region (the Hidaka Main Thrust). Therefore, we infer that the E type CPO was originated from a local water infiltration event. AG type CPO, on the other hand, was considered as a secondary product enhanced by the synkinematic melts in the northern (geological upper) part, combined with the pressure-temperature path inferred by previous petrological studies. Furthermore, we reconstructed the senses of shear strain using the microstructure and olivine crystal-fabrics. Then we built the tectonic history of the Horoman peridotite complex integrating the structural development of the Hidaka metamorphic belt.

中文翻译：

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Horoman 橄榄岩杂岩体的结构演变与北海道 Hidaka 变质带的形成相结合


我们对日本北海道日高变质带的 Horoman 橄榄岩杂岩体内的橄榄岩进行了晶体结构分析。收集了 50 多个取向的橄榄岩样品，并分析了橄榄石织物强度 （J 指数） 和晶体学择优取向 （CPO）。橄榄岩包含四种橄榄石 CPO：A、E、D 和 AG 型。我们证实橄榄石 CPOs 呈现从 E 到 A 再到 AG 型从南到北的过渡分布。以前的实验研究表明，E 型 CPO 可以在含水条件下合并。此外，大地磁观测表明，俯冲海洋板块为该地区的基底推力（日高主推力）提供孔隙流体。因此，我们推断 E 型 CPO 起源于当地的渗水事件。另一方面，AG 型 CPO 被认为是由北部（地质上部）的联动熔体结合先前岩石学研究推断的压力-温度路径增强的次级产品。此外，我们使用微观结构和橄榄石晶体结构重建了剪切应变的感觉。然后，我们构建了 Horoman 橄榄岩杂岩体的构造历史，整合了 Hidaka 变质带的结构发展。