Probing the Chilean subduction zone at mantle depths:Insights from Patagonian High-Pressure rocks

尽管在过去的30年里进行了大量的地球物理研究，但智利俯冲带的结构和深度超过40公里的动力学仍然没有得到很好的解决。在此，我们建议研究智利边缘在Diego de Almagro岛（智利巴塔哥尼亚）的蓝片岩-榴辉岩相（深度40-50 km）中发掘的唯一高压变质地体，以突出智利俯冲带深处（40-50 km）的增生和流体-岩石相互作用过程。该岛的内部结构显然是由来自不同来源和变质历史的物质构成的，需要进一步描述其地质历史。实地活动将允许(i)实现整个岛屿的广泛采样和结构测量；（ii）实现整个岛屿的第一个地质横截面；（iii）为构建岛屿的各种子单元执行详细的压力-温度-时间-变形路径。该方法的优势在于将现代热气压测量工具与原位Ar-Ar地质年代学约束和Rb-Sr变形年龄相结合。这些结果对于提高我们对智利俯冲通道的岩性组成和构造以及根植于发震带底部的变形过程的认识具有重要意义。结果还将揭示莫霍深度的俯冲界面动力学，因此对地球物理学家社区具有重要意义。

Even though documented by numerous geophysical studies over the last 30 years, the Chilean subduction zone structure and dynamics at depths greater than 40 km remains poorly resolved. We herein propose to study the only high-pressure metamorphic terrane from the Chilean margin exhumed from blueschist-to-eclogite facies (40-50 km depth) on the Diego de Almagro Island (Patagonia, Chile), to highlight accretionary and fluid-rock interaction processes in the deep (40-50 km) Chilean subduction zone. The internal structure of the Island, which is apparently constituted by material from various origins and metamorphic histories, needs further characterization of its geological history. The field campaign will permit (i) to realize a widespread sampling and structural measurements throughout the Island (ii) to realize the first geological cross-section across the island and (iii) to perform detailed pressure-temperature-time-deformation paths for the various sub-units building up the island. The strength of our approach is to combine modern thermobarometric tools with in situ Ar-Ar geochronological constrains and Rb-Sr deformation ages. These results will be of importance to improve our vision of the lithological composition and structure of the Chilean subduction channel as well as of deformation processes rooted at the base of the seismogenic zone. The results will also shed light on subduction interface dynamics at Moho depths and will therefore be of importance of the geophysicists community.