The Formation and Evolution of Uvarovite in UHP Serpentinite and Rodingite and its Constraints on Chromium Mobility in the Oceanic Subduction Zone  

作　　者：ZHANG Cong SHEN Tingting ZHANG Lifei LIN Congcong ZHANG Zhongwei Qin Xueqing HU Han QIU Tian XIANG Zhenqun ZHANG Jianxin 

机构地区：[1]Key Laboratory of Deep-Earth Dynamics of the Ministry of Natural Resources,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China [2]School of Earth and Space Sciences,Peking University,Beijing 100871,China [3]Comprehensive Exploration Technology Center,Shandong Coal Field Geological Survey and Research Institute,Jinan 250104,China [4]Tianjin Center,China Geological Survey,Tianjin 300170,China

出　　处：《Acta Geologica Sinica(English Edition)》2021年第5期1456-1471,共16页地质学报（英文版）

基　　金：financially supported by the National Natural Science Foundation of China(Grant Nos.41872067,41972064,41630207,41720104009,41703053);Project of the Chinese Geological Survey(Grant Nos.DD20190006,DD20190060);the Foundation of the Chinese Academy of Geological Sciences(Grant Nos.J1901-9,J1901-31,J1903)。

摘　　要：The uvarovite-andradite and uvarovite-andradite-grossular solid-solution series are rare in nature.The discovery of uvarovite-andradite in serpentinite and rodingite from the ultra-high pressure(UHP)metamorphic belt in southwestern Tianshan provided an opportunity to investigate its behavior in the subduction zone.Uvarovite(defined as chromiumgarnet)from serpentinite is homogeneous in a single grain,covering compositions in the uvarovite-andradite solid solution series of Adr_(58-66)Uv_(33-41),with few grossular components.Uvarovite from rodingites contain various Cr_(2)O_(3) contents(1.7-17.9 wt%)and mineral compositions being in the range of Adr_(21-31)Uv_(41-50)Grs_(22-37),Adr_(52-90)Uv_(5-25)Grs_(0-21) and Adr_(19-67)Uv_(3-63)Grs_(13-42).Discontinuous chemical variation of uvarovite from core to rim indicates that uvarovite formed by consuming andradite and chromite,which could provide Ca,Cr,Al and Fe.Raman signals of water were identified for uvarovite from both serpentinite and rodingite,with high water content in uvarovite from serpentinite.The high pressure mineral assemblage,as well as the association with perovskite,indicated that the studied uvarovite from serpentinite and rodingite was formed through high pressure metamorphism,during the subduction zone serpentinization and rodingitization.High alkaline and highly reduced fluids released from serpentinization or rodingitization in the oceanic subduction zone promote the mobility of chromium and enable its long-distance migration.

关 键 词：UVAROVITE SERPENTINITE RODINGITE chromium migration oceanic subduction zone 

分 类 号：P542[天文地球—构造地质学]