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Zhang L.,Jilin University | Liu Y.,Jilin University | Li W.,Jilin University | Han G.,Jilin University | And 4 more authors.
Scientia Geologica Sinica | Year: 2013

Northeast China is the critical area for solving the tectonic evolution of the East-Asian continent, it has thus drawn much attention. In recent years, the debates on the Ergun massif has been very intense, especially, the basement properties and the eastern boundary of Ergun massif. In this paper, the zircon LA-ICP-MS U-Pb dating for granitic gneiss of the Taiping Forest has been obtained, the zircon age mainly concentrates in the range of 840~830 Ma, 800~780 Ma and 730~720 Ma, probably corresponds to three stages of magmatic event in Neoproterozoic. The weighted mean 206Pb/238U age of 21 analyzed zircon points yielded 779±20 Ma(MSWD=8.3), indicates that the original rock has emplaced and crystallized in Neoproterozoic; one zircon analysis shows U-Pb isotope age of 494±10 Ma, with the Th/U ratio is 0.06, suggesting that the zircon should be metamorphic origin, and this age therefore may be the metamorphic age of granite gneiss. Combine with the ages of granitoid that previously reported in Ergun massif and Xing'an massif, we concluded that only the Ergun massif has experienced the Neoproterozoic magmtic event; In addition, the Hf isotopic characteristics of granite in the Ergun massif and the Xing'an massif, obviously show different stages of initial evolution of the crust. Subsequent to the period of the collision between the Ergun massif and the Xing'an massif along the Tahe-Xiguitu suture zone in early Early Paleozoic, the two massifs have experienced Paleozoic magmatism together. The conclusions presented here significantly differ from the previous reported viewpoint that the Ergun massif and the Xing'an massif sutured along the Derbugan Fault.

Gou J.,Jilin University | Sun D.-Y.,Jilin University | Ren Y.-S.,Jilin University | Liu Y.-J.,Jilin University | And 5 more authors.
Journal of Asian Earth Sciences | Year: 2013

U-Pb dating and Hf isotopic analyses of zircons from various granitoids, combined with major and trace element analyses, were undertaken to determine the petrogenesis and geodynamic setting of Neoproterozoic and Late Paleozoic magmatism in the Manzhouli-Erguna area of Inner Mongolia, China. The Neoproterozoic granitoids are mainly biotite monzogranites with zircon U-Pb ages of 894±13Ma and 880±10Ma, and they are characterised by enrichment in large ion lithophile elements (LILEs; e.g., Rb, Ba, K) and light rare earth elements (LREEs), depletion in high field strength elements (HFSEs; e.g., Nb, Ta, Ti) and heavy rare earth elements (HREEs). The Late Devonian granitoids are dominantly syenogranites and mylonitised syenogranites with zircon U-Pb ages of 360±4Ma, and they form a bimodal magmatic association with subordinate gabbroic rocks of the same age. The Late Devonian syenogranites have A-type characteristics including high total alkalis, Zr, Nb, Ce and Y contents, and high FeOt/MgO, Ga/Al and Rb/Sr ratios. The Carboniferous granitoids are mainly tonalites, granodiorites and monzogranites with U-Pb ages varying from 319 to 306Ma, and they show very strong adakitic characteristics such as high La/Yb and Sr/Y ratios but low Y and Yb contents. The Late Permian granitoids are dominated by monzogranites and syenogranites with zircon U-Pb ages ranging between 257 and 251Ma. Isotopically, the εHf(t) values of the Neoproterozoic granitoids range from +4.3 to +8.3, and the two-stage model ages (TDM2) from 1.2 to 1.5Ga. The Late Devonian granitoids are less radiogenic [εHf(t) from +12.0 to +12.8 and TDM2 from 545 to 598Ma] than the Carboniferous [εHf(t) from +6.8 to +9.5 and TDM2 from 722 to 894Ma] and Late Permian granitoids [εHf(t) from +6.1 to +9.4 and TDM2 in the range of 680-895Ma]. These data indicate (1) the Neoproterozoic granitoids may have been generated by melting of a juvenile crust extracted from the mantle during the Mesoproterozoic, probably during or following the final stages of assembly of Rodinia as a result of the collision and amalgamation of Australia and the Tarim Craton; (2) the Late Devonian granitoids may have formed by partial melting of a new mantle-derived juvenile crust in a post-orogenic extensional setting; (3) the Carboniferous granitoids appear to have been produced by melting of garnet-bearing amphibolites within a thickened continental crust during and following the collision of the Songnen and Erguna-Xing'an terranes; and (4) the Late Permian granitoids may have been generated by melting of garnet-free amphibolites within the Neoproterozoic juvenile continental crust, probably in the post-collisional tectonic setting that followed the collision of the North China and Siberian cratons. © 2013 Elsevier Ltd.

Chen X.-H.,Northeastern University China | Gong E.-P.,Northeastern University China | Zhao Z.-H.,Northeastern University China | Zhao Z.-H.,No 240 Institute Of Nuclear Industry | Yang F.,No 240 Institute Of Nuclear Industry
Dongbei Daxue Xuebao/Journal of Northeastern University | Year: 2011

Based on former research findings, sedimentary system characteristics and potential uranium mineralization sections of the upper Sunjiawan formation of the late cretaceous located near Heishui were analyzed using principles of sedimentology, well logging geology, and stratigraphy. Results indicated that the Heishui area is in the formative stage of the upper Sunjiawan formation and is not located at the center of the Pingzhuang basin but lies on the edge of the basin. The sedimentary base level experienced a cycle in which elevation occurred during the early stage, a high point was reached in mid stage, and a drop off during the late stage. During this period, alluvial braided channel deposits were favorable to uranium mineralization.

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