Time filter

Source Type

Ages and chemical and isotopic compositions of the Permian mafic dyke swarms from Kelamayi, eastern Tianshan and western Tianshan in western part of the Central Asian Orogenic Belt (CAOB), NW China, are reported here in order to gain more insights into the Permian Tarim Large Igneous Province (Tarim LIP). These CAOB mafic (-andesitic) dyke swarms from Kelamayi, eastern Tianshan and western Tianshan were emplaced at 267±3Ma, 278±2Ma and 260-290Ma, respectively, and are coeval with the radiating mafic dyke swarm in the Tarim Block. The dykes in CAOB exhibit subalkalic character in major element compositions, and are enriched in LILE and LREE and depleted in HFSE and HREE, with the exception of a few LREE-depleted samples from western Tianshan. Isotopically, dykes from Kelamayi and western Tianshan are characterized by significant positive εNd(t) values (3.1 to 7.9 for Kelamayi; 7.2 to 7.3 for western Tianshan), while dykes form eastern Tianshan exhibit variable negative εNd(t) values (-0.7 to -3.3). Their geochemical features suggest that the mafic (-andesitic) dykes in CAOB were derived from a recently metasomatized lithospheric mantle source (sub-continental lithosphere mantle) with subsequent variable extents of assimilation of the crustal materials in a non-orogenic setting. In contrast, the mafic dykes in Tarim exhibit systematic chemical signatures similar to those of OIB, indicating that they were derived from a depleted sub-lithospheric mantle source. We thus propose that the Permian Tarim LIP has two different mantle domains for the coeval mafic rocks, i.e., the Tarim domain and the CAOB domain. © 2012 Elsevier B.V. Source

Zhang C.-L.,Nanjing Institute of Geology and Mineral Resources | Zou H.-B.,Auburn University
Lithos | Year: 2013

Zircon U-Pb ages, whole-rock geochemical and zircon Hf isotope data are reported for the Permian A-type quartz syenites-granites in western Tarim Block, Northwest China. Zircon U-Pb dating indicates these alkali plutons were emplaced at 270-277Ma. Elemental geochemistry shows their typical A-type signatures, i.e., high total alkali, HFSE, REE contents and Ga/Al, FeOtot/(FeOtot+MgO) and Nb/Y ratios. Isotopically, their epsilon Nd values vary from -2.6 to 2.0. Based on zircon Hf isotope compositions, they could be divided into two sub-groups: Group I exhibits high positive εHf(t) ranging from 3 to 11 (mostly within the range of 5 to 9), which is highly comparable with the syenites in Bachu area located just south of these plutons. Group II has εHf(t) ranging from -3 to 2. The second group exhibits comparable Nd-Hf isotope compositions with the spatially and temporally related Piqiang ultramafic-mafic complex. Integrating geological, geochemical and Nd-Hf isotope data, we suggest that the A-type syenite-granites were formed via intensive crystal fractionation from a common plume-derived parental mafic magma, coupled with variable extent of crustal contamination. Moreover, the extent of the crustal contamination increase from inner Tarim towards South Tianshan Collisional Belt.A comprehensive synthesis of the coeval A-type granites in the western part of the Central Asian Orogenic Belt (CAOB) shows that they exhibit distinct geochemical features, e.g., large range of εNd(t) and (87Sr/86Sr)i values, high Y/Nb, Yb/Ta and low Nb/La ratios. All these features argue that they were derived from juvenile mafic crust with variable addition of the mafic materials from mantle sources and some old crustal materials or mixing of mantle-derived mafic magma with Precambrian crustal components. We suggest that both the Permian A-type granites from Tarim and western section of CAOB were genetically linked to the Permian Tarim mantle plume, which is concurrent with the two mantle domains for the Permian Tarim Large Igneous Province (LIP). © 2013 Elsevier B.V. Source

Xu Z.-Q.,Chinese Academy of Geological Sciences | He B.-Z.,Chinese Academy of Geological Sciences | Zhang C.-L.,Nanjing Institute of Geology and Mineral Resources | Zhang J.-X.,Chinese Academy of Geological Sciences | And 2 more authors.
Precambrian Research | Year: 2013

Based on new petrographic observations and zircon U-Pb geochronological data of the Precambrian basement from deep drilling cores in the Tarim basin and comparison with the Precambrian basements surrounding orogenic belts of the Tarim basin, we reconstruct a possible unified Tarim block. Data presented in this contribution lead to a three-fold subdivision of the pre-900. Ma basement of the Tarim block into the North Tarim terrane, the South Tarim terrane and the Central Tarim terrane. The North Tarim terrane containing Precambrian basements of the northern part of the Tarim basin, the Korla-Kuluketage and the Dunhuang area possesses a ca. 2.7-2.5. Ga or an even older continental nucleus and underwent multiple phases of magmatic and metamorphic events at ca. 2.0-1.8. Ga, 1.0-0.8. Ga and 760-687. Ma. The South Tarim terrane including Precambrian basements of the southern part of the Tarim basin, eastern Kunlun and western Kunlun orogenic belts, possesses a 2.4-2.3. Ga continental nucleus and underwent 2.0-1.75. Ga and 1.0-0.8. Ga metamorphic and magmatic events. The Central Tarim terrane encompassing Precambrian basement of the central part of the Tarim basin and the Altun orogenic belt, is characterized by magmatic arc system during 940-890. Ma. The unified Tarim Block was assembled as part of Rodinia supercontinent after series of geological processes, e.g. (1) breakup between the North and South Tarim terranes, (2) formation of the Central Tarim ocean, (3) subduction-related magmatic arc accretion, and (4) finally amalgamation of the North and South Tarim terranes during 1.0-0.8. Ga. There are two phases of the middle Neoproterozoic magmatic activities at 820-760. Ma and 760-687. Ma, respectively. They were most possibly related to the two phases of the Rodinia plume activities. The late Mesoproterozoic to Sinian assembly and breakup of the Rodinia led to the typical double-layered structure of the Tarim Block, i.e. the Pre-Nanhuaian basement and the Nanhuaian to Sinian cover sequence. Based on this study, we suggest that the unified Tarim Block, composed of Precambrian basement of Tarim basin and its surrounding orogenic belts, should be more large than the present Tarim basin. © 2013 Elsevier B.V. Source

Zhang C.-L.,Nanjing Institute of Geology and Mineral Resources | Li H.-K.,Tianjin Institute of Geology and Mineral Resources | Santosh M.,Kochi University | Santosh M.,China University of Geosciences
Terra Nova | Year: 2013

New field observations and zircon U-Pb age data, combined with previous studies, are employed here to evaluate the process of assembly of the Yangtze and Cathaysia Blocks. We show that the process started from the west prior to 1.0 Ga and migrated eastward with the final amalgamation along the suture at around 830-820 Ma. During the period of 850-820 Ma, both the mantle plume which possibly started at 850 Ma and the north-directed plate subduction along the southern margin of the Yangtze Block controlled the formation and closure of a back-arc basin along the middle to eastern segment of the Yangtze Block, as well as the diverse and complex magmatic activities. The closure of the back-arc basin and almost synchronous rift basin overlying the folded "basement" sequence mark the termination of subduction when the Rodinia plume exerted a dominant control on the evolution of the middle to late Neoproterozoic basin and the related magmatic pulses. © 2013 Blackwell Publishing Ltd. Source

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

Discover hidden collaborations