The South Qilian belt mainly comprises an early Paleozoic arc-ophiolite complex, accretionary prism, microcontinental block, and foreland basin. These elements represent accretion-collision during Cambrian to Silurian...The South Qilian belt mainly comprises an early Paleozoic arc-ophiolite complex, accretionary prism, microcontinental block, and foreland basin. These elements represent accretion-collision during Cambrian to Silurian time in response to closure of the Proto-Tethyan Ocean in the NE of the present-day Tibet Plateau. Closure of the Proto-Tethyan Ocean between the Central Qilian block and the Oulongbuluke block and the associated collision took place from NE to SW in a zipper-like style. Sediment would have been dispersed longitudinally SW-ward with a progressive facies migration from marginal alluvial sediments toward slope deep-water and deep-sea turbidites. This migration path indicates an ocean basin that shrank toward the SW. The Balonggongga'er Formation in the western South Qilian belt represents the fill of a latest Ordovician-Silurian remnant ocean basin that separated the Oulongbuluke block from the Central Qilian block, and records Silurian closure of the Proto-Tethyan Ocean and subduction beneath the Central Qilian block. However, alluvial deposits in the Lajishan area were accumulated in a retro-foreland basin, indicating that continent-continent collision in the eastern South Qilian belt occurred at c. 450–440 Ma. These results demonstrate that the Proto-Tethyan Ocean closed diachronously during early Paleozoic time.展开更多
The Archean North China Craton is composed of the Western Block,Eastern Block and the intervening Central Orogenic Belt.A 4-10 km wide and 85 km long tectonic mélange belt informally called the Zanhuang tectonic
As one of the important Paleo-Tethys suture zones in eastern Tibet,the Jinshajiang orogenic belt is of great significance to study the tectonic evolution of the main suture zone of Paleo-Tethys.In this paper,eclogites...As one of the important Paleo-Tethys suture zones in eastern Tibet,the Jinshajiang orogenic belt is of great significance to study the tectonic evolution of the main suture zone of Paleo-Tethys.In this paper,eclogites developed in the Jinshajiang suture zone in Gonjo area,eastern Tibet,are selected as specific research objects,and petrological,geochemical and Ar-Ar geochronological analyses are carried out.The major element data of the whole rock reveals that the eclogite samples have the characteristics of picritic basalt-basalt and belong to the oceanic low potassium tholeiites.The results of rare earth elements and trace elements of the samples show that the protoliths of eclogites have characteristics similar to oceanic island basalt(OIB)or normal mid ocean ridge basalt(N-MORB).Muscovite(phengite)from two eclogite samples yield the Ar-Ar plateau ages of 247±2 Ma and 248±2 Ma respectively,representing the peak metamorphic age of eclogite facies and the timing of complete closure of the Jinshajiang Paleo-Tethys Ocean.Muscovite and biotite selected from the hosting rocks of eclogite yield the Ar-Ar plateau ages are 238±2 Ma and 225±2 Ma respectively,reflecting the exhumation age of eclogites and their hosting rocks.Combined with the zircon U-Pb dating data(244 Ma)of eclogites obtained in previous work,it can be concluded that the Jinshajiang Paleo-Tethys ocean was completely closed and arc-continent collision was initiated at about 248-244 Ma(T21).Subsequently,due to the large-scale arc(continent)-collision orogeney between Deqin-Weixi continental margin arc and Zhongza block(T31-T32),the eclogites were rapidly uplifted to the shallow crust.展开更多
基金the National Natural Science Foundation of China(Grants 41672221,41872241)China Geological Survey(Grants DD20190006,DD2016020104)IGGCAS Open Research Foundation(SKLK201702)。
文摘The South Qilian belt mainly comprises an early Paleozoic arc-ophiolite complex, accretionary prism, microcontinental block, and foreland basin. These elements represent accretion-collision during Cambrian to Silurian time in response to closure of the Proto-Tethyan Ocean in the NE of the present-day Tibet Plateau. Closure of the Proto-Tethyan Ocean between the Central Qilian block and the Oulongbuluke block and the associated collision took place from NE to SW in a zipper-like style. Sediment would have been dispersed longitudinally SW-ward with a progressive facies migration from marginal alluvial sediments toward slope deep-water and deep-sea turbidites. This migration path indicates an ocean basin that shrank toward the SW. The Balonggongga'er Formation in the western South Qilian belt represents the fill of a latest Ordovician-Silurian remnant ocean basin that separated the Oulongbuluke block from the Central Qilian block, and records Silurian closure of the Proto-Tethyan Ocean and subduction beneath the Central Qilian block. However, alluvial deposits in the Lajishan area were accumulated in a retro-foreland basin, indicating that continent-continent collision in the eastern South Qilian belt occurred at c. 450–440 Ma. These results demonstrate that the Proto-Tethyan Ocean closed diachronously during early Paleozoic time.
文摘The Archean North China Craton is composed of the Western Block,Eastern Block and the intervening Central Orogenic Belt.A 4-10 km wide and 85 km long tectonic mélange belt informally called the Zanhuang tectonic
基金funded by two Second Tibetan Plateau Comprehensive Scientific Investigation and Research Projects(2019QZKK0702,2019QZKK0706)a project of National Natural Science Foundation of China(42230311)two geological survey projects of China Geological Survey(DD20221635,DD20221811).
文摘As one of the important Paleo-Tethys suture zones in eastern Tibet,the Jinshajiang orogenic belt is of great significance to study the tectonic evolution of the main suture zone of Paleo-Tethys.In this paper,eclogites developed in the Jinshajiang suture zone in Gonjo area,eastern Tibet,are selected as specific research objects,and petrological,geochemical and Ar-Ar geochronological analyses are carried out.The major element data of the whole rock reveals that the eclogite samples have the characteristics of picritic basalt-basalt and belong to the oceanic low potassium tholeiites.The results of rare earth elements and trace elements of the samples show that the protoliths of eclogites have characteristics similar to oceanic island basalt(OIB)or normal mid ocean ridge basalt(N-MORB).Muscovite(phengite)from two eclogite samples yield the Ar-Ar plateau ages of 247±2 Ma and 248±2 Ma respectively,representing the peak metamorphic age of eclogite facies and the timing of complete closure of the Jinshajiang Paleo-Tethys Ocean.Muscovite and biotite selected from the hosting rocks of eclogite yield the Ar-Ar plateau ages are 238±2 Ma and 225±2 Ma respectively,reflecting the exhumation age of eclogites and their hosting rocks.Combined with the zircon U-Pb dating data(244 Ma)of eclogites obtained in previous work,it can be concluded that the Jinshajiang Paleo-Tethys ocean was completely closed and arc-continent collision was initiated at about 248-244 Ma(T21).Subsequently,due to the large-scale arc(continent)-collision orogeney between Deqin-Weixi continental margin arc and Zhongza block(T31-T32),the eclogites were rapidly uplifted to the shallow crust.
