https://scholars.lib.ntu.edu.tw/handle/123456789/331748
標題: | Geochemistry and geochronology of high-grade rocks from the Grove Mountains, East Antarctica: Evidence for an Early Neoproterozoic basement metamorphosed during a single Late Neoproterozoic/Cambrian tectonic cycle | 作者: | BOR-MING JAHN Liu, Xiaochun Jahn, Bor-Ming Zhao, Yue Zhao, Guochun Liu, Xiaohan |
關鍵字: | Early Neoproterozoic; East Antarctica; Grove Mountains; Late Neoproterozoic/Cambrian; Mafic-felsic intrusion; Prydz Belt; Single metamorphic cycle | 公開日期: | 2007 | 卷: | 158 | 期: | 1-2 | 起(迄)頁: | 93-118 | 來源出版物: | Precambrian Research | 摘要: | The Grove Mountains of East Antarctica are an inland continuation of the Prydz Belt. The high-grade metamorphic complex in this area is composed of felsic orthogneisses and mafic granulites, with minor paragneisses and calc-silicate rocks. U-Pb zircon analyses using SHRIMP and LA-ICP-MS techniques reveal that the protoliths of mafic granulites and felsic orthogneisses were emplaced during a short time interval of ca. 920-910 Ma. Mafic granulites can be divided into low- and high-Ti groups. They have initial εNd values [εNd(T)] ranging from +0.8 to -1.9. TiO2 is positively correlated with FeOt/MgO and La/Nb ratios, whereas it shows a negative correlation with εNd(T) values, indicating that the petrogenesis of their protoliths involved partial melting of a weakly enriched subcontinental lithospheric mantle and fractional crystallization of the magma accompanied by minor crustal contamination. Felsic orthogneisses have an affinity of A2-type granites, characterized by enrichment in REE, Y, Zr, Th and Ga and high Ga/Al and Y/Nb ratios. Most of them have εNd(T) values of -0.7 to -3.5 and Nd depleted mantle model ages (TDM) of 1.76-1.65 Ga, and a few have low εNd(T) values of -10.4 to -10.6 and old TDM of 2.46-2.27 Ga, reflecting a heterogeneity in their source region. Their protoliths were probably produced by high-temperature partial melting of tonalitic-granodioritic rocks triggered by the underplating of mantle-derived mafic magma during post-orogenic extension. U-Pb analyses also reveal a metamorphic age of ca. 2050 Ma from detrital zircons in a paragneiss, suggesting that the sedimentary materials of the paragneiss may have come from an as yet undiscovered Early Paleoproterozoic orogen of unknown provenance. Voluminous mafic-felsic intrusives and a small amount of sedimentary rocks constitute an Early Neoproterozoic basement of the Grove Mountains. Subsequently, this basement experienced only a single Late Neoproterozoic/Cambrian metamorphic cycle at ca. 550-535 Ma. The available data indicate that the Prydz Belt is a collage of multiple basement terranes and each of them has a distinct tectonic evolution. This supports the suggestion that the Prydz Belt may represent a Late Neoproterozoic/Cambrian collisional orogen that resulted in the final phase of the Gondwana assembly. © 2007 Elsevier B.V. All rights reserved. |
URI: | http://www.scopus.com/inward/record.url?eid=2-s2.0-34547800112&partnerID=MN8TOARS http://scholars.lib.ntu.edu.tw/handle/123456789/331748 |
DOI: | 10.1016/j.precamres.2007.04.005 | SDG/關鍵字: | basement rock; Cambrian; fractional crystallization; geochemistry; geochronology; granite; granulite; igneous intrusion; metamorphism; orthogneiss; paragenesis; partial melting; petrogenesis; Proterozoic; protolith; SHRIMP dating; tectonic evolution; tonalite; zircon; Antarctica; East Antarctica; Grove Mountains; Prydz Bay |
顯示於: | 地質科學系 |
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