首页|Geochemistry and mineral chemistry of the armoor granitoids,eastern dharwar craton:implications for the redox conditions and tectono-magmatic environment
Geochemistry and mineral chemistry of the armoor granitoids,eastern dharwar craton:implications for the redox conditions and tectono-magmatic environment
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The mineralogical and geochemical character-istics of the K-rich granites from the Armoor granitic rocks in the northeastern portion of the Eastern Dharwar Craton(EDC)are presented.In order to understand its physico-chemical conditions,the petrogenesis of the granitoid was explained from biotite chemistry and geochemical sys-tematics.Studies of mineral chemistry expose that com-positionally,K-feldspar and plagioclase in Armoor granite rocks range from An0,Ab3-5.9,Or94-96,9 and An5-29,-Ab71.9-94.9,Or0-1.5,respectively.The mineral chemistry of biotite crystals exhibits composition that varies from pri-mary to re-equilibrated primary biotites.Although biotites from the Armoor granites generally exhibit an I-type trend,with calc-alkaline parental magma in a subduction setting.Biotite chemistry of granites displays magnetite(oxidized)series nature,which has oxygen fugacity(fO2)=-15.1 to-16.7(log10 bar),under high oxidizing conditions.Tem-perature and pressure estimates for the crystallization of Armoor granites based on biotite composition are T=612-716 ℃ and 1.0-0.4 kbar,respectively.Geo-chemically,these rocks are metaluminous to slightly per-aluminous and magnesian,with calc-alkaline potassium-rich granite.On the chondrite normalized REE diagram,the granites have positive europium anomalies;rich Sr/Y,(Dy/Yb)N ratios and reduced Mg#,Rb/Sr,Rb,Sr indicate that the melting of earlier rocks,crystal accumulation and residual garnet source formed at high pressures.The examined granites show that they are produced from the melting of crustal sources.Thus,the extensive analyses of the described Armoor granite suggest that they were pro-duced by crust sources and developed under oxidizing conditions in subduction setting.
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