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Zeng C.-Y.,Guangxi Geological Survey Institute | Zeng C.-Y.,Guangdong Provincial Key Laboratory of Mineral Resources & Geological Processes | Ding R.-X.,Sun Yat Sen University | Ding R.-X.,Guangdong Provincial Key Laboratory of Mineral Resources & Geological Processes | And 7 more authors.
Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis

Pangxidong composite granitoid pluton located in the southwestern margin of Yunkai massif. The metamorphic grade of this pluton increases from outside to inside, that is, banded-augen granitic gneisses, gneissoid granites and granites distribute in order from edge to core. X-Ray Fluorescence Spectroscopy and Plasma Mass Spectrometry are conducted to study the geochemical characteristics of the three types of rocks. The result shows that all the three types of rocks are peraluminous rocks and their contents of main elements and rare earth elements change gradually. From granitic gneisses to granites, the contents of Al2O3, CaO, MgO, TiO2, total rare earth elements and light rare earth elements increase, but the contents of SiO2 and heavy rare earth elements decrease. It is suggested that the phylogenetic relationship exists between granitic gneisses, gneissoid granites and granites during the multi-stage tectonic evolution process. Furthermore, the remelting of metamorphosed supracrustal rocks in Yunkai massif is probably an important cause of granitoid rocks forming. The evolutionary mechanism is probably that SiO2 and heavy rare earth elements were melt out from the protolith and gradually enriched upward, but Al2O3, CaO, MgO, TiO2 and light rare earth elements enriched downward. © 2015, Science Press. All right reserved. Source

Zeng C.,Guangxi Geological Survey Institute | Zeng C.,Guangdong Provincial Key Laboratory of Geological Processes and Mineral Resources Survey | Zhou Y.,Sun Yat Sen University | Zhou Y.,Guangdong Provincial Key Laboratory of Geological Processes and Mineral Resources Survey | And 8 more authors.
Earth Science Frontiers

The Qinzhou Bay (Q)-Hangzhou Bay (H) juncture orogenic belt is a giant suture separating Yangtze Block from Cathaysia Block in South China. Before involving into the Western Pacific active continental margin, it underwent several stages of regional-scale tectono-magmatism events. Assembly-collision had taken place between Yangtze Block and Cathaysia Block during the Neoproterozoic Sibao orogeny (1000-880 Ma), with suture spreading from the Jiangshan-Shaoxing Fault, through northeastern Jiangxi Province and eastern Hunan Province, to the Qinzhou Bay of Guangxi Province. Post-collision process included post-orogeny magmatism stage and extension-break up stage, with broad extensional basin between Yangtze and Cathaysia Blocks. During the Silurian (460-410 Ma) and the Indosinian (250-200 Ma), Yangtze Block and Cathaysia Block re-assembled, leading to the regional-scale tectono-magmatism and the united depositional environment in South China. Affected by the West Pacific subduction, the transformation of tectonic regime during the Late Jurassic (125-140 Ma) in South China turned the tectonic setting from compression to lithosphere thinning, arousing intensive magmatism and mineralization. Three segments, the northern, the middle and the southern, may be distinguished by the geological variation and are divided roughly at latitudes 24° and 27° north. The middle section is overlapped with the traditional Nanling Belt; the northern section is roughly coincident with the Shaoxing-Jiangshan-Pingxiang zone; and the southern section with the Yunkai-Shiwandashan Mountainous zone. Chronological and chemical studies show that meta-mafic and ultramafic rocks found in the western Yunkai massif were formed in the Neoproterozoic and display MORB or ITA characteristics. The Caledonian meta-volcanic rocks in the Cenxi area display the same MORB chemical characteristics. The Early Mesozoic felsic volcanics and rhyolite in the both sides of Shiwandashan Mountains also display geochemical characteristics of typical subduction-related arc volcanic rocks. Therefore, a paleo ocean plate did exist in the Q-H juncture orogenic belt, the same as the evolution of north segment, which underwent collision and orogeny events during the Neoproterozoic, Caledonian and Indosinian eras. ©, 2015, Chinese Academy of Forestry. All right reserved. Source

Fu L.,Wuhan University | Wei J.,Wuhan University | Li Y.,Wuhan University | Tan J.,Wuhan University | And 3 more authors.
Chinese Journal of Geochemistry

The Kunlunguan biotite granite pluton, located in the southwestern part of the Nanling Mesozoic granite belt, is controlled by the NW-trending Nandan-Kunlunguan deep fault. LA-ICP-MS zircon U-Pb dating yielded a weighted mean 206Pb/238U age of 93.0±1 Ma (MSDW=1.7) for the main part of the pluton, implying its Late Cretaceous intrusion. The Kunlunguan body is a high-K calc-alkaline rock characterized by high silicon, alkali and aluminum, and low phosphorus and titanium. SiO2 contents of the Kunlunguan body range from 68.13% to 72.61% and K2O/Na2O ratios from 1.28 to 1.87. A/CNK values vary from 0.76 to 1.42, indicating a metaluminous to intensively peraluminous character. The rocks are enriched in Ga, Rb, Th, U and Pb but depleted in Ba, Nb, Sr, P and Ti. The REEs are characterized by remarkable negative Eu anomalies (Eu/Eu*=0.53-0.73) and exhibit right-inclined "V"-shaped patterns with LREE enrichment. Petrology, major and trace elements data all indicate that the pluton is aluminous A-type granite which intruded in a post-collisional extensional tectonic setting. It is related to back-arc extension, reflecting high-angle subduction of the paleo-Pacific plate, caused by northward movement of the Indian plate. The Nandan-Kunlunguan A-type granites belt, together with similar plutons in the coastal areas of Zhejiang and Fujian provinces, represent the two A-type granite belts under a matching tectonic system. © 2010 Science Press, Institute of Geochemistry, CAS and Springer Berlin Heidelberg. Source

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