Partial melting of deeply subducted continental crust and the formation of quartzofeldspathic polyphase inclusions in the Sulu UHP eclogites  

作　　者：ZENG LingSen LIANG FengHua ASIMOW Paul CHEN FangYuan CHEN JJng 

机构地区：[1]Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China [2]Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA [3]School of Physics, Peking University, Beijing 100871, China

出　　处：《Chinese Science Bulletin》2009年第15期2580-2594,共15页

基　　金：Supported by the National Natural Science Foundation of China (Grant No. 40673027);Outlay Research Fund of Chinese Academy of Geological Sciences (Grant No.20071120101125)

摘　　要：Two types of quartzofeldspathic inclusions hosted by omphacite and garnet were identified in the Sulu UHP eclogites. The first consists of albite, quartz, and various amounts of K-feldspar. In contrast, the second consists predominantly of K-feldspar and quartz without any albite. The presence of quart-zofeldspathic inclusions within the UHP mafic eclogites indicates that partial melting occurred in deeply subducted continental crust via mica dehydration melting reactions at an early stage of rapid exhumation. Such a melting event generated hydrous Na-K-Al-Si melts. These melts infiltrated into the mafic eclogite and were captured by recrystallizing garnet or omphacite, which together followed by dehydration and crystallization to form feldspar-bearing polyphase inclusions. Formation of silicate melts within the deeply subducted continental slab not only provides an excellent medium to transport both mobile (LILE) and immobile (HFSE) elements over a large distance, but also induces effective changes in the physical properties of the UHP slab. This process could be a major factor that enhances rapid exhumation of a deeply subducted continental slab.Two types of quartzofeldspathic inclusions hosted by omphacite and garnet were identified in the Sulu UHP eclogites. The first consists of albite, quartz, and various amounts of K-feldspar. In contrast, the second consists predominantly of K-feldspar and quartz without any albite. The presence of quartzofeldspathic inclusions within the UHP mafic eclogites indicates that partial melting occurred in deeply subducted continental crust via mica dehydration melting reactions at an early stage of rapid exhumation. Such a melting event generated hydrous Na-K-Al-Si melts. These melts infiltrated into the mafic eclogite and were captured by recrystallizing garnet or omphacite, which together followed by dehydration and crystallization to form feldspar-bearing polyphase inclusions. Formation of silicate melts within the deeply subducted continental slab not only provides an excellent medium to transport both mobile （LILE） and immobile （HFSE） elements over a large distance, but also induces effective changes in the physical properties of the UHP slab. This process could be a major factor that enhances rapid exhumation of a deeply subducted continental slab.

关 键 词：超高压榴辉岩 大陆地壳 深俯冲 包裹体 部分熔融 多相 体形 快速折返 

分 类 号：P588.34[天文地球—岩石学] P541[天文地球—地质学]