The basic granulite of the Altay orogenic belt occurs as tectonic lens in the Devonian medium- to lower-grade metamorphic beds through fault contact. The Altay granulite (AG) is an amphibole plagioclase two-pyroxene ...The basic granulite of the Altay orogenic belt occurs as tectonic lens in the Devonian medium- to lower-grade metamorphic beds through fault contact. The Altay granulite (AG) is an amphibole plagioclase two-pyroxene granulite and is mainly composed of two pyroxenes, plagioclase, amphibole and biotite. Its melano-minerals are rich in Mg/(Mg+Fe2+), and its amphibole and biotite are rich in TiO2. The AG is rich in Mg/(Mg+Fe2+), Al2O3 and depletion of U, Th and Rb contents. The AG has moderate ∑REE and LREE-enriched with weak positive Eu anomaly. The AG shows island-arc pattern with negative Nb, P and Ti anomalies, reflecting that formation of the AG may be associated with subduction. Geochemical and mineral composition data reflect that the protolith of the AG is calc-alkaline basalt and formed by granulite facies metamorphism having peak P-T conditions of 750 °C?780 °C and 0.6?0.7 Gpa. The AG formation underwent two stages was suggested. In the early stage of oceanic crustal subduction, calc-alkaline basalt with island-arc environment underwent granulite facies metamorphism to form the AG in deep crust, and in the late stage, the AG was thrust into the upper crust.展开更多
Recently, a series of basic granulite enclosures are found in the granulite gneisses along the right side of the Yarlung Zangbo River, lying west of the Namjagbarwa Mountain. Es-pecially, some high-pressure granulite ...Recently, a series of basic granulite enclosures are found in the granulite gneisses along the right side of the Yarlung Zangbo River, lying west of the Namjagbarwa Mountain. Es-pecially, some high-pressure granulite enclosures have been discovered in eastern gully of the Zhibei village. To the northwest of the high-pressure granulite belt there occur Yarlung Zangbo ophiolite zone. Southeastward the granulites change into amphibolite and green-schist facies rocks, which constitute a complete lower crust section.展开更多
文摘The basic granulite of the Altay orogenic belt occurs as tectonic lens in the Devonian medium- to lower-grade metamorphic beds through fault contact. The Altay granulite (AG) is an amphibole plagioclase two-pyroxene granulite and is mainly composed of two pyroxenes, plagioclase, amphibole and biotite. Its melano-minerals are rich in Mg/(Mg+Fe2+), and its amphibole and biotite are rich in TiO2. The AG is rich in Mg/(Mg+Fe2+), Al2O3 and depletion of U, Th and Rb contents. The AG has moderate ∑REE and LREE-enriched with weak positive Eu anomaly. The AG shows island-arc pattern with negative Nb, P and Ti anomalies, reflecting that formation of the AG may be associated with subduction. Geochemical and mineral composition data reflect that the protolith of the AG is calc-alkaline basalt and formed by granulite facies metamorphism having peak P-T conditions of 750 °C?780 °C and 0.6?0.7 Gpa. The AG formation underwent two stages was suggested. In the early stage of oceanic crustal subduction, calc-alkaline basalt with island-arc environment underwent granulite facies metamorphism to form the AG in deep crust, and in the late stage, the AG was thrust into the upper crust.
基金Project supported by the National Natural Science Foundation of China and the National Key Project KJ 85-07-01-04.
文摘Recently, a series of basic granulite enclosures are found in the granulite gneisses along the right side of the Yarlung Zangbo River, lying west of the Namjagbarwa Mountain. Es-pecially, some high-pressure granulite enclosures have been discovered in eastern gully of the Zhibei village. To the northwest of the high-pressure granulite belt there occur Yarlung Zangbo ophiolite zone. Southeastward the granulites change into amphibolite and green-schist facies rocks, which constitute a complete lower crust section.
