Intrusion age, geochemistry and metamorphic conditions of a quartz-monzosyenite intrusion at the craton–Eastern Ghats Belt contact near Jojuru, India

详细信息    查看全文

• 作者：D. Upadhyay ; M.M. Raith
• 关键词：Craton– ; Eastern Ghats Belt suture ; Monzosyenite ; Mesoproterozoic ; Pan-African ; Amphibolite facies
• 刊名：Gondwana Research
• 出版年：2006
• 出版时间：November 2006
• 年：2006
• 卷：10
• 期：3-4
• 页码：267-276
• 全文大小：1501 K

文摘

The boundary between the Archean cratons and the Eastern Ghats Belt in peninsular India represents a rifted Mesoproterozoic continental margin which was overprinted by a Pan-African collisional event associated with the westward thrusting of the Eastern Ghats granulites over the cratonic foreland. The contact zone contains a number of deformed and metamorphosed nepheline syenite complexes of rift-related geochemical affinities. In addition to the nepheline-bearing rocks, metamorphosed quartz-bearing monzosyenitic bodies can also be identified along the suture in the region between the Godavari-Pranhita graben and the Prakasam Igneous Province. One such occurrence at Jojuru near Kondapalle is geochemically comparable to the nepheline syenites and furnishes a weighted mean concordant U–Th–Pb SHRIMP zircon age of 1263 ± 23 Ma (2σ), which provides a lower age bracket for the rift-related magmatic activity. The original igneous mineral assemblage in the monzosyenite was partially replaced by the formation of coronitic garnet during the Pan-African metamorphism of the rocks. P–T estimates of garnet corona formation at the interface between clinopyroxene–orthopyroxene–ilmenite clusters and plagioclase indicate mid to upper amphibolite facies condition (5.5–7.0 kbar and 600–700 °C) during the thrust induced deformation and metamorphism associated with the Pan-African collisional tectonics.