The composition and chemical zoning in garnet from high to ultrahigh pressure metamorphic rocks
The composition and chemical zoning in garnet from high to ultrahigh pressure metamorphic rocks
复制标题
高压至超高压变质岩石榴石的成分和化学分带
DOI：
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发表时间：
2011
影响因子：
1.8
通讯作者：
Zheng YongFei
中科院分区：
文献类型：
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作者：
Xia QiongXia;Zheng YongFei
石榴石常见于高压至超高压变质成因的榴辉岩和片麻岩中，其耐火度高，在流体和熔体中溶解度低，在俯冲带变质作用过程中得以完好保存。石榴石中保存的化学成分和矿物包裹体可用于约束P-T条件、变质演化和流体作用。石榴石的化学成分与全岩等多种因素有关。石榴石的成分、P-T条件、形成石榴石的变质反应以及共生矿物的组合。因此，在用于约束超高压变质岩的变质P-T演化过程时，应考虑石榴石中的主量元素、微量元素、氧同位素、矿物包裹体及其相互关系。另外，还需对锆石和/或锆石等副矿物中的U-Pb同位素和微量元素进行原位分析。石榴石中的独居石包裹体可以直接制约变质石榴石的生长时间。通过研究俯冲带变质作用过程中石榴石的生长历史，不仅可以为含石榴石变质岩的生成过程提供岩石学和地球化学证据，而且可以为石榴石的成因提供线索，这对于俯冲带变质作用的化学动力学具有重要意义。
Garnet is common in eclogite and gneiss of high-pressure(HP)to ultrahigh-pressure(UHP)metamorphic origin.It can be well preserved during subduction-zone metamorphism for its high refractoriness and low solubility in fluid and melt.The chemical composition and mineral inclusions preserved in garnet can be used to constrain the P-T conditions,metamorphic evolution,and fluid action.The chemical composition of garnet is related to many factors,such as whole-rock composition,P-T conditions,garnet-forming metamorphic reactions and the assemblage of coexisting minerals.Thus the major elements,trace elements,oxygen isotopes,mineral inclusions and their relations in garnet should all be taken into account when it is used to constrain the metamorphic P-T evolution in UHP metamorphic rocks.In addition,in-situ analyses of U-Pb isotopes and trace elements in accessory minerals such as zircon and/or monazite inclusions in garnet can place a direct constraint on the time of metamorphic garnet growth.Through studying the history of garnet growth during subduction-zone metamorphism,it can not only provide petrologic and geochemical evidence for the processes to produce garnet-bearing metamorphic rocks,but also give clues to the origin of garnet.These are very important to the chemical dynamics of subduction-zone metamorphism.