Blueschist accompanied by pelitic schist expose along the Xinlin-Xiguitu fault in the Toudaoqiao area, northeastern China. In this paper, the blueschist is systematically studied on the petrography and mineral chemist...Blueschist accompanied by pelitic schist expose along the Xinlin-Xiguitu fault in the Toudaoqiao area, northeastern China. In this paper, the blueschist is systematically studied on the petrography and mineral chemistry. The amphiboles in the blueschist are zoned from winchite core to magnesioriebeckite/glaucophane rim to winchite outermost rim. The peak metamorphic conditions are defined by the mineral assemblage of magnesioriebeckite/glaucophane, epidote, high-Si phengite（Si〈7.1）, chlorite, albite, hematite and quartz, indicating an epidote-blueschist facies metamorphism. The P-T conditions are estimated as T=350–400 ℃ and P=10-12 kbar. The occurrence of the blueschist along the Xinlin-Xiguitu fault strongly suggests the fault is the suture between the Ergun and the Xing＇an blocks situated in the eastern portions of the Central Asia Orogenic Belt（CAOB）.展开更多
We undertook a boat expedition to explore the geological framework of a very remote, lesser-known island, in the Chilean Patagonia: the Diego de Almagro Island(latitude S51°330'). This uninhabited, ca.400 km^...We undertook a boat expedition to explore the geological framework of a very remote, lesser-known island, in the Chilean Patagonia: the Diego de Almagro Island(latitude S51°330'). This uninhabited, ca.400 km^2 Island is one of the very rare exposures of the Mesozoic accretionary subduction complex along the Chilean margin. Unstable weather, strong winds, steep topography, and very dense vegetation make an on-land mission difficult. Careful preparation based on high-resolution satellite images is advised to optimize shore access and minimize risks of injury. Despite a relatively important degree of regional reequilibration of metamorphic assemblages due to sluggish exhumation through the forearc crust, our results have shown that the island is composed of a nappe stack of ocean-floor derived slivers of metasedimentary units that exhibit very different pressure-temperature-time paths during burial by subduction under the Chilean margin and subsequent exhumation. These rocks are witness to a complex thermal evolution of the subduction zone between Jurassic and Cretaceous times from granulite facies to blueschist facies conditions as well as multiple episodes of accretion at ca. 35 -40 km in depth for almost100 Ma over the Mesozoic era.展开更多
The <sup>40</sup>Ar/<sup>39</sup>Ar ages indicate that the eclogite facies rocks of the Hasiate slice in the western Tianshan Mountains were formed at the early stage of Devonian （401 Ma） and...The <sup>40</sup>Ar/<sup>39</sup>Ar ages indicate that the eclogite facies rocks of the Hasiate slice in the western Tianshan Mountains were formed at the early stage of Devonian （401 Ma） and had been uplifted to the greenschist facies tectonic level in the middle stage of Devonian （381 Ma）. The formation and uplift of the blueschists of the Akesayi slice are constrained to the late stage of Devonian （370-364 Ma）. The different tectonic slices in the high-pressure metamorphic belt have experienced the different uplift history.展开更多
基金supported by 973 program (No.2013CB429802) to Y.J.Liuthe National Natural Science Foundation of China (Grant 41302175) to W.M.LiJilin University and JSPS Grant-in-Aid for Scientific Research (Nos.17340149, 24340124) to A.Takasu, Shimane University, Japan
文摘Blueschist accompanied by pelitic schist expose along the Xinlin-Xiguitu fault in the Toudaoqiao area, northeastern China. In this paper, the blueschist is systematically studied on the petrography and mineral chemistry. The amphiboles in the blueschist are zoned from winchite core to magnesioriebeckite/glaucophane rim to winchite outermost rim. The peak metamorphic conditions are defined by the mineral assemblage of magnesioriebeckite/glaucophane, epidote, high-Si phengite（Si〈7.1）, chlorite, albite, hematite and quartz, indicating an epidote-blueschist facies metamorphism. The P-T conditions are estimated as T=350–400 ℃ and P=10-12 kbar. The occurrence of the blueschist along the Xinlin-Xiguitu fault strongly suggests the fault is the suture between the Ergun and the Xing＇an blocks situated in the eastern portions of the Central Asia Orogenic Belt（CAOB）.
文摘We undertook a boat expedition to explore the geological framework of a very remote, lesser-known island, in the Chilean Patagonia: the Diego de Almagro Island(latitude S51°330'). This uninhabited, ca.400 km^2 Island is one of the very rare exposures of the Mesozoic accretionary subduction complex along the Chilean margin. Unstable weather, strong winds, steep topography, and very dense vegetation make an on-land mission difficult. Careful preparation based on high-resolution satellite images is advised to optimize shore access and minimize risks of injury. Despite a relatively important degree of regional reequilibration of metamorphic assemblages due to sluggish exhumation through the forearc crust, our results have shown that the island is composed of a nappe stack of ocean-floor derived slivers of metasedimentary units that exhibit very different pressure-temperature-time paths during burial by subduction under the Chilean margin and subsequent exhumation. These rocks are witness to a complex thermal evolution of the subduction zone between Jurassic and Cretaceous times from granulite facies to blueschist facies conditions as well as multiple episodes of accretion at ca. 35 -40 km in depth for almost100 Ma over the Mesozoic era.
文摘The <sup>40</sup>Ar/<sup>39</sup>Ar ages indicate that the eclogite facies rocks of the Hasiate slice in the western Tianshan Mountains were formed at the early stage of Devonian （401 Ma） and had been uplifted to the greenschist facies tectonic level in the middle stage of Devonian （381 Ma）. The formation and uplift of the blueschists of the Akesayi slice are constrained to the late stage of Devonian （370-364 Ma）. The different tectonic slices in the high-pressure metamorphic belt have experienced the different uplift history.
