Petrology of gedrite‐bearing rocks in mid‐crustal ductile shear zones from the Eastern Ghats Belt, India
Petrology of gedrite‐bearing rocks in mid‐crustal ductile shear zones from the Eastern Ghats Belt, India
复制标题
印度东高止山脉中地壳韧性剪切带含镁辉石岩石的岩石学
DOI：
10.1046/j.1525-1314.1999.00226.x
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发表时间：
1999
影响因子：
3.4
通讯作者：
Raith
中科院分区：
文献类型：
--
作者：
Dasgupta;Sengupta;P. Sengupta;Ehl;Raith
印度东高止山脉带最南端的一套变质岩、基性岩和石英长石质岩，被内生片麻岩侵入，变质于公元前200年。750-800 °C，6 kbar，经受重复的韧性剪切变形，水化，冷却和伴随的碱交代沿着狭窄的剪切带。 含钙铝榴石的组合发育于穿越变碧岩的剪切带中。FMASH系统中适当的P-T网格、NFMASH系统中等温等压μH2O-μ Na 2 O网格中的反应结构解释以及地质温压数据表明，含镁铁辉石共生体具有复杂的演化历史。最初，由于在几乎恒定但高μH2O的情况下μ Na 2 O增加，伴随冷却，产生了含镁铁榴石的组合。由于μ Na_2O的逐渐增加，使钙铝榴石部分失稳为斜方辉石+钠长石。在进一步冷却和增加μ H_2O时，岩石中出现第二代镁铁榴石。
A suite of metapelitic, basic and quartzofeldspathic rocks intruded by enderbitic gneiss from the southernmost tip of the Eastern Ghats Belt, India, and metamorphosed at c. 750–800 °C, 6 kbar, were subjected to repeated ductile shear deformation, hydration, cooling and accompanying alkali metasomatism along narrow shear zones. Gedrite‐bearing assemblages developed in the shear zones traversing metapelitic rocks. Interpretation of the reaction textures in an appropriate P–T grid in the system FMASH, an isothermal–isobaric μH2O–μNa2O grid in the system NFMASH, and geothermobarometric data suggest a complex evolutionary history for the gedrite‐bearing parageneses. Initially, gedrite‐bearing assemblages were produced due to increase in μNa2O at nearly constant but high μH2O accompanying cooling. Gedrite was partially destabilized to orthopyroxene+albite due to progressively increasing μNa2O. During further cooling and at increased μH2O a second generation of gedrite appeared in the rocks.