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Zhang C.-L.,Nanjing Institute of Geology and Mineral Resources | Zou H.-B.,Auburn University | Li H.-K.,Tianjin Institute of Geology and Mineral Resources | Wang H.-Y.,Nanjing Institute of Geology and Mineral Resources
Gondwana Research | Year: 2013

The Tarim Block is characterized by a double layer structure consisting of a Precambrian basement and Neoproterozoic to Cambrian cover series. It experienced different stages of tectonic evolution since its generation, with similarities and dissimilarities to the North and South China Blocks in many aspects. This has brought about complexities in understanding the tectonic processes of crustal growth and reworking in the Tarim Block. In this contribution, we provide a comprehensive synthesis on the regional geology and analytical data. Based on the study herein, we constructed its tectonic framework and main evolution stages and its sedimentary-magmatic-metamorphic concurrence to the main tectonic events. In the Archean, the 2.80-2.57. Ga Archaean TTG was intruded by the ca.2.53. Ga high Ba-Sr granite, leading to the formation of the Archean proto crust of the Tarim. During the Proterozoic, two periods of tectono-metamorphic events occurred in the Orosirian-Statherian period (2.0-1.8. Ga) and the late Mesoproterozoic to early Neoproterozoic (1.0-0.9. Ga), respectively. They were concurrent with the global assembly of Columbia and Rodinia supercontinents, respectively. Since 760. Ma, Tarim and other landmasses started to split from Rodinia in response to the Rodinian breakup. In the middle to late Neoproterozoic, the Rodinia breakup resulted in the diverse and voluminous intriguing igneous activities along the northern margin of the Tarim. In the Early Cambrian, the Tarim Block drifted away from the other parts of Rodinian landmass in response to the Pan-African tectonic event. During the late Neoproterozoic to the Carboniferous, the early Paleozoic Northern Kunlun orogen was produced by collision of the Qaidam with the southern margin of Tarim, whereas in the late Paleozoic the southern Tianshan orogen was brought about due to collision between the Yili terrane and the northern margin of Tarim. In the Permian, a large igneous province occurred in Tarim, which is the last igneous activity in this block. © 2012 International Association for Gondwana Research. Source

Liu C.,Chinese Academy of Geological Sciences | Zhao G.,University of Hong Kong | Liu F.,Chinese Academy of Geological Sciences | Shi J.,Tianjin Institute of Geology and Mineral Resources
Lithos | Year: 2014

The Lu¨liang Complex is located at the western margin of the middle segment of the Trans-North China Orogen, along which the Western and Eastern Blocks amalgamated to form the basement of the North China Craton. The complex consists of the Paleoproterozoic granitic plutons and meta-supracrustal rocks, of which the latter are subdivided into the Jiehekou, Lu¨liang, Yejishan, and Heichashan/Lanhe Groups. A meta-volcanic rock from the Yejishan Group gives a magmatic zircon U-Pb age of 2188±48Ma and εHf(t) values of +0.06 to +5.42. Based on the geochemical characteristics, four different ~2.2Ga igneous rock suits have been identified in the Lu¨liang Complex. The calc-alkaline basalts and andesites show the geochemical features of typical 'normal' arc volcanics with pronounced LREE enrichments relative to HREE, negative Nb, Ta, P and Ti anomalies and εNd(t) values of -2.69 to +2.14. The adakitic rocks are characterized by high Na2O/K2O ratios, weak to positive Eu anomalies, positive Sr and Ba but negative Nb and Ti anomalies, and relatively clustered and near to zero εNd(t) values. The Nb-enriched basalts and andesites have higher Nb, Zr and TiO2 contents, higher Nb/Ta (14.4-19.3) and Nb/U (20.6-23.2) ratios than the majority of arc basalts and andesites and relatively variable εNd(t) values (-1.54 to +3.02). The magnesian andesites are characterized by anomalously high MgO, Cr and Ni contents and have εNd(t) values of -3.90 to +1.17. The occurrence of adakitic rocks, Nb-enriched basalts and andesites and magnesian andesites has been described from many modern arcs featuring subduction of oceanic slab. Therefore, we suggest that similar mechanism may have played an important role in the production of the ~2.2Ga igneous rocks in the Lu¨liang Complex and thus the final collision between the Eastern and Western Blocks along the TNCO must have happened at some time after ~2.2Ga. © 2014 Elsevier B.V. Source

Zhang J.,Chinese Academy of Geological Sciences | Yu S.,Chinese Academy of Geological Sciences | Gong J.,Chinese Academy of Geological Sciences | Li H.,Tianjin Institute of Geology and Mineral Resources | Hou K.,Chinese Academy of Geological Sciences
Precambrian Research | Year: 2013

The Dunhuang block, in the easternmost segment of the Tarim craton, exposes Precambrian mafic granulite and felsic gneiss. To better understand the poorly known formation and evolution of the Tarim craton, we carried out detailed field-based petrological and geochronological investigations on the major lithologies of the Dunhuang block. U-Pb dating and Hf isotopic analyses on the mafic granulite and felsic gneiss (TTG gneiss) of the Dunhuang block reveal two distinct age populations: the Latest Neoarchaean (∼2.5. Ga) and the Late Palaeoproterozoic (1.82-1.85. Ga). The zircon magmatic cores and metamorphic rims of tonalitic gneisses yield similar ages of ∼2.5. Ga, supporting the existence of Archean rocks in the Dunhuang block. The short time interval between Latest Neoarchean magmatism and high-grade metamorphism suggests that they were related to the same Latest Neoarchean tectonothermal event. The ∼2.5. Ga zircons show Hf-depleted mantle model ages between 2.55. Ga and 2.8. Ga with a peak at ∼2.7. Ga, suggesting that ∼2.7. Ga juvenile crust of the Dunhuang block was reworked during a 200-300. m.y. period at the end of the Neoarchean. The age of ∼1.85. Ga obtained from the mafic granulites and felsic gneisses is interpreted as the age of high-pressure granulite facies metamorphism. Combined with the Hf isotopic data, these data suggest that the Dunhuang block experienced ∼2.7. Ga crustal growth, a ∼2.5. Ga magmatic-metamorphic event and a 1.82-1.85. Ga (HP) granulite facies metamorphic event. This sequence of events is very similar to that of the North China Craton, implying that the evolutionary history of the Dunhuang block was consistent with that of the North China Craton from the Neoarchean to Paleoproterozoic. © 2012 Elsevier B.V. Source

Liang X.,China University of Geosciences | Wang G.,China University of Geosciences | Yuan G.,China University of Geosciences | Liu Y.,Tianjin Institute of Geology and Mineral Resources
Gondwana Research | Year: 2012

The Late Paleozoic Qomo Ri Accretionary Complex (QRAC) in the Central Qiangtang region of Tibet lies at the southern margin of the Longmu Co-Shuanghu suture. QRAC is tectonically linked with the Nierong and Jitang metamorphic complexes in eastern Tibet and the Yunling and Lancang complexes in western Yunnan province, SW China. This metamorphic complex is mainly composed of Late Paleozoic passive continental marginal strata of the South Qiangtang basin, which was underthrust beneath North Qiangtang in the Late Triassic. At least three stages of deformation, D 1, D 2 and D 3, with two corresponding metamorphic events, M 1 and M 2, were identified within the QRAC. D 1 is characterized by a penetrative foliation, S 1, bearing a dextral shear and a corresponding M 1 mineral assemblage of phengite, garnet and quartz. This deformation was interpreted to be the result of the northwestward oblique subduction of the Paleo-Tethys Ocean and dated at 211-219Ma by phengite 40Ar/ 39Ar ages. D 2, a subsequent compression deformation, followed D 1 immediately and exhibits flexural folds and pervasive axial crenulation in foliation S 2. Deformations from D 1 to D 2 indicate that an oblique oceanic subduction was immediately followed by a collision between the North and South Qiangtang blocks along the Longmu Co-Shuanghu suture. The D 3, recorded by minor folds and divisional axial cleavage (S 3), is related to a giant arc structure with an extension of ~50km. © 2011 International Association for Gondwana Research. Source

Zhang C.-L.,Nanjing Institute of Geology and Mineral Resources | Santosh M.,China University of Geosciences | Zou H.-B.,Auburn University | Li H.-K.,Tianjin Institute of Geology and Mineral Resources | Huang W.-C.,Nanjing Institute of Geology and Mineral Resources
Lithos | Year: 2013

The Fuchuan ophiolite occurs along the easternmost domain of the Jiangnan Orogen, considered as the suture between Yangtze and Cathaysia Blocks in South China. Here we report results from our new field observations, zircon U-Pb ages and Hf isotope of the cumulate units, chemistry and tectonic discrimination of Cr-spinel from the harzburgite, and whole rock geochemistry of the pillow lava from the ophiolite in an attempt to evaluate the Neoproterozoic tectonic evolution of South China. The zircon data indicate that the ophiolite suite formed at 840-820Ma, and the high εHf(t) (8-13) and εNd(t) (3.3-5.7) values suggest that the cumulates were derived from significantly depleted mantle sources. The pillow lavas and the keratophyres, show typical calc-alkalic continental arc-signatures including the enrichment in LREE and LILE, and depletion in HFSE (Nb/La=0.3 to 0.5) and a wide range of εNd(t) values (-1.2 to 2.5). The chromium-spinels from the serpentinized harzburgite show Cr# ranging from 40 to 67 and Mg# from 33 to 60 comparable with the chemistry of spinels from suprasubduction zone (SSZ)-type ophiolites. The geochemical features as well as the association of coeval I-S type granites and several thousand meters of flysch-type sedimentary sequences correlate the Fuchuan ophiolite to SSZ-type. We suggest that the emplacement of the Fuchuan ophiolite suite marks the time of final welding between the Yangtze and Cathaysia blocks in South China at ca.820Ma. © 2013 Elsevier B.V. Source

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