The sodium-rich dacites and albite porphyries of Permian in the Awulale Mountain of west Tianshan have unique chemical and trace element signatures identical to adakite. These intermediate-acidic igneous rocks are cha...The sodium-rich dacites and albite porphyries of Permian in the Awulale Mountain of west Tianshan have unique chemical and trace element signatures identical to adakite. These intermediate-acidic igneous rocks are characterized by high Na2O, Al2O3 and Sr contents and high Sr/Y and La/Y ratios (】40 and 】20, respectively), and low Y and Yb contents, and strong depletion in HREE, and positive Eu anomaly. The (143Nd/144Nd)i is in the range from0.51236 to 0.51248 and the εNd(t) is positive value (+0.79-+3.11); the (87Sr/86Sr)i is in the range from 0.7052 to 0.7054. These Nd and Sr isotopic composition features indicate that the source rocks of these adakite-type rocks are from a weakly depleted mantle, or a depleted mantle, but was contaminated by the crustal materials. These adakite-type rocks were most likely derived from the partial melting of new underplated basaltic rocks under the conditions of amphibo-lite to eclogite transition in the postcollisional environment of North Xinjiang during the Permian展开更多
Field observation, petrological and geochemical characteristics of plagiogranite from Kuerti ophiolite indicate a similar origin to those in shearing zones. It isderived from partial melting of amphibolite that is dev...Field observation, petrological and geochemical characteristics of plagiogranite from Kuerti ophiolite indicate a similar origin to those in shearing zones. It isderived from partial melting of amphibolite that is developed from gabbro within the ocean layer 3 shear zone by the low-angle shearing deformation during the oceanic crustmigrating process. Zircon SHRIMP age of 372±19 Ma for the plagioganite from Kuerti ophiolite indicates that thisophiolite formed in the Devonian period and it alsorepresented the time of extension of the Kuerti backarc basin that is relevant to the northwards subduction of thePaleo-Asian oceanic crust. Therefore, the northwardssubduction of the Paleo-Asian Ocean beneath the Siberian Plate began in the early stage of the Late Paleozoic era.展开更多
基金This workwas co-supported by the State Major Basic Research Program of China (Grant No. G1999043200) the State "305" Program of China (Grant No. 96-915-03-02)+1 种基金 the Chinese Academy of Sciences (Grant No. KZCX2-102) the State Climbing Program of Chi
文摘The sodium-rich dacites and albite porphyries of Permian in the Awulale Mountain of west Tianshan have unique chemical and trace element signatures identical to adakite. These intermediate-acidic igneous rocks are characterized by high Na2O, Al2O3 and Sr contents and high Sr/Y and La/Y ratios (】40 and 】20, respectively), and low Y and Yb contents, and strong depletion in HREE, and positive Eu anomaly. The (143Nd/144Nd)i is in the range from0.51236 to 0.51248 and the εNd(t) is positive value (+0.79-+3.11); the (87Sr/86Sr)i is in the range from 0.7052 to 0.7054. These Nd and Sr isotopic composition features indicate that the source rocks of these adakite-type rocks are from a weakly depleted mantle, or a depleted mantle, but was contaminated by the crustal materials. These adakite-type rocks were most likely derived from the partial melting of new underplated basaltic rocks under the conditions of amphibo-lite to eclogite transition in the postcollisional environment of North Xinjiang during the Permian
基金supported by the State Key Basic Research Development Program(Grant No.2001CB409805)the National Natural Science Foundation of China(Grant No.40073006).
文摘Field observation, petrological and geochemical characteristics of plagiogranite from Kuerti ophiolite indicate a similar origin to those in shearing zones. It isderived from partial melting of amphibolite that is developed from gabbro within the ocean layer 3 shear zone by the low-angle shearing deformation during the oceanic crustmigrating process. Zircon SHRIMP age of 372±19 Ma for the plagioganite from Kuerti ophiolite indicates that thisophiolite formed in the Devonian period and it alsorepresented the time of extension of the Kuerti backarc basin that is relevant to the northwards subduction of thePaleo-Asian oceanic crust. Therefore, the northwardssubduction of the Paleo-Asian Ocean beneath the Siberian Plate began in the early stage of the Late Paleozoic era.
