The Ladakh batholith is exposed along the 600km long and 20 to 80km wide NW—SE trending Ladakh range north of the Indus\|Tsangpo Suture Zone. It was emplaced into an unmetamorphosed thick pile of mafic and felsic vol...The Ladakh batholith is exposed along the 600km long and 20 to 80km wide NW—SE trending Ladakh range north of the Indus\|Tsangpo Suture Zone. It was emplaced into an unmetamorphosed thick pile of mafic and felsic volcanics, ultramafics and sediments of Upper Cretaceous\|Eocene age (Dras Volcanics, Khardung Volcanics). The granites from the Ladakh batholith within the Leh\|Khardung La and Sakti—Chang La sections (samples collected between altitude of 3600m and 5440m above mean sea level, Fig.1) have been estimated for pressure and temperature of crystallization employing the hornblende geobarometer of Schmidt (1992) and hornblende\|plagioclase geothermometer of Blundy and Holland (1990), with the results of pressure of (250±60)MPa and temperature of (695±22)℃. Therefore, these granites were solidified at a depth of (8 6±2)km suggesting an unroofing of this thickness in this region. The importance of this geobarometric data in conjunction with age data on the cooling and unroofing history of the Trans\|Himalayan Ladakh batholith and geodynamic implications of the India—Asia collision are discussed.展开更多
The westerly extension of the Dras volcanics in the Deosai plateau of Baltistan, northern Pakistan, lying east of the Nanga Parbat—Haramosh Massif, is comprised of agglomerates and tuffs together with flows consistin...The westerly extension of the Dras volcanics in the Deosai plateau of Baltistan, northern Pakistan, lying east of the Nanga Parbat—Haramosh Massif, is comprised of agglomerates and tuffs together with flows consisting of basalt, andesite and some rhyolite. In the filed these volcanics are overlying the Ladakh batholith and both these basic and acidic suites of rocks carry the signatures of the Nanga Parbat—related orogeny. The flows appear to have evolved from a basaltic magma, with opaque oxide, clinopyroxene, hornblende and plagioclase, respectively appearing on the liquidus. These have been metamorphosed under greenschist facies conditions and may contain abundant epidote, chlorite and secondary amphibole. Metamorphic impact seems to be stronger in the west, i.e., in the vicinity of Nanga Parbat—Haramosh Massif, than in the East. An 40 Ar/ 39 Ar age of (125 4±6)Ma on hornblende phenocrysts in an andesite is in agreement with the Late Jurassic to Cretaceous age of the Dras volcanics, in India, and indicates that Nanga Parbat related tectonics may have played a part in the growth of lower green schist facies assemblage of the volcanic rocks.展开更多
文摘The Ladakh batholith is exposed along the 600km long and 20 to 80km wide NW—SE trending Ladakh range north of the Indus\|Tsangpo Suture Zone. It was emplaced into an unmetamorphosed thick pile of mafic and felsic volcanics, ultramafics and sediments of Upper Cretaceous\|Eocene age (Dras Volcanics, Khardung Volcanics). The granites from the Ladakh batholith within the Leh\|Khardung La and Sakti—Chang La sections (samples collected between altitude of 3600m and 5440m above mean sea level, Fig.1) have been estimated for pressure and temperature of crystallization employing the hornblende geobarometer of Schmidt (1992) and hornblende\|plagioclase geothermometer of Blundy and Holland (1990), with the results of pressure of (250±60)MPa and temperature of (695±22)℃. Therefore, these granites were solidified at a depth of (8 6±2)km suggesting an unroofing of this thickness in this region. The importance of this geobarometric data in conjunction with age data on the cooling and unroofing history of the Trans\|Himalayan Ladakh batholith and geodynamic implications of the India—Asia collision are discussed.
文摘The westerly extension of the Dras volcanics in the Deosai plateau of Baltistan, northern Pakistan, lying east of the Nanga Parbat—Haramosh Massif, is comprised of agglomerates and tuffs together with flows consisting of basalt, andesite and some rhyolite. In the filed these volcanics are overlying the Ladakh batholith and both these basic and acidic suites of rocks carry the signatures of the Nanga Parbat—related orogeny. The flows appear to have evolved from a basaltic magma, with opaque oxide, clinopyroxene, hornblende and plagioclase, respectively appearing on the liquidus. These have been metamorphosed under greenschist facies conditions and may contain abundant epidote, chlorite and secondary amphibole. Metamorphic impact seems to be stronger in the west, i.e., in the vicinity of Nanga Parbat—Haramosh Massif, than in the East. An 40 Ar/ 39 Ar age of (125 4±6)Ma on hornblende phenocrysts in an andesite is in agreement with the Late Jurassic to Cretaceous age of the Dras volcanics, in India, and indicates that Nanga Parbat related tectonics may have played a part in the growth of lower green schist facies assemblage of the volcanic rocks.
