Paired garnet-clinopyroxene inclusions in diamonds – implications to the fate of subducted slab

During crystallisation, a small proportion of diamonds (no more than 2%), captures tiny inclusions of other minerals. In rare cases, inclusions of different minerals are captured simultaneously. Here we propose to implement the Synchrotron Mössbauer Source (beamline ID14) in order to measure Fe3+/Fe2+ in paired garnet-clinopyroxene inclusions. These inclusions are of eclogitic origin meaning that at some point in time they were at the surface, and were later transported into the deep mantle by subduction. The study of these inclusions will permit us not only to identify the oxidation state of the upper mantle eclogitic rocks, but to also assess how oxidised is the material transported by subduction. This study will have important implications to the mantle rheology and transport properties as well as to mantle convection and material circulation by subduction

在钻石结晶过程中，仅有不超过2%的钻石会捕获其他矿物的微小包裹体。极少数情况下，钻石会同时捕获多种矿物的包裹体。本研究拟采用同步穆斯堡尔源（Synchrotron Mössbauer Source，光束线ID14），以测定成对产出的石榴石-单斜辉石包裹体中的Fe³+/Fe²+比值。这类包裹体具有榴辉岩成因，意味着它们曾一度位于地表，随后通过俯冲作用被带入地球深部地幔。对这类包裹体开展研究，不仅能够确定上地幔榴辉岩的氧化状态，还可以评估俯冲作用所搬运物质的氧化程度。本研究对于地幔流变学与输运特性、以及地幔对流和俯冲作用相关的物质循环均具有重要的科学意义。