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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 Creta-ceous intrusion. The Kunlunguan body is a high-K calc-alkaline rock characterized by high silicon, alkali and alu-minum, 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.
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 Creta-ceous intrusion. The Kunlunguan body is a high-K calc-alkaline rock characterized by high silicon, alkali and alu-minum, and low 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 significant negative Eu anomalies (Eu / Eu * = 0.53-0.73) and exhibit right-inclined “ ”-shaped patterns with LREE enrichment. Petrology, major and trace elements data all indicate that the pluton is alumin ous 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.