Title: The Sakar batholith - petrology, geochemistry and magmatic evolution
Abstract:Based on a new sample set and extensive re-mapping an attempt is made to elucidate the field relations, mineral composition, nomenclature, geochemical features, magmatic and postmagmatic evolution, an...Based on a new sample set and extensive re-mapping an attempt is made to elucidate the field relations, mineral composition, nomenclature, geochemical features, magmatic and postmagmatic evolution, and to find new evidence for geodynamic reconstructions of the Sakar batholith. The dome-like batholith is emplaced into high-grade metamorphic rocks of still unclear age. It is covered by Permian and Triassic sedimentary rocks. The batholith is composed of the following granitoid units: equigranular in the inner parts, porphyroid with large microcline megacrysts in the outer parts, and small aplitoid bodies. Large xenoliths of gneisses and orthoamphibolites occur in the marginal parts of the batholith. The modal petrographic species are quartz-monzodiorite, quartz-monzonite, granodiorite, granite, quartz-syenite and leucogranite. The main rock-forming minerals are separated from artificial heavy concentrates and studied optically, chemically, by X-ray and IR-analysis. No characteristic differences are observed for the plagioclase composition in the equigranular and porphyroid granitoids - An30-An10, but plagioclases in the aplitoid granitoids are more acid - An15-An10. Potassium feldspars are high microclines. Their rims are poorer in Sr, Ba, Li, Co and richer in Th and U. Biotite is a common variety with prevailing siderophyllite isomorphism. Muscovites are primary magmatic and secondary postmagmatic. Based on 147 new analyses for 36 elements, some specific petrochemical and geochemical features are revealed and arguments in favour of primary and secondary petrogenetic evolution are discussed. Crystal fractionation is required to explain the geochemical pattern of the rocks. Late-magmatic to post-magmatic re- crystallization is supposed for the microcline porphyry crystals. The rocks are typically calc-alkaline and exhibit REE distributions intrinsic to plate margin orogenic settings. Mixed volcanic-arc and post-collisional discriminations argue for the presence of mantle component in the magma source and crustal contamination of the magmas. Presumably, melting of amphibolite/basaltic rocks from the lower crust could generate the parental magmas, which produced the rocks of the batholith by differentiation, fluid input and postmagmatic reworking.Read More
Publication Year: 2010
Publication Date: 2010-01-01
Language: en
Type: article
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Cited By Count: 6
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