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《Earth Science》 2018-07
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Zircon U-Pb Geochronology and Geochemical Characteristics of the Kunlunguan A-Type Granite in Central Guangxi

Liu Fei;Li Kun;Huang Guicheng;Qiu Xiaofei;Yan Lejia;Lu Shicai;Wuhan Center of China Geological Survey;Research Center of Granitic Diagenesis and Mineralization,China Geological Survey;Guangxi Geological Exploration Institute of China Metallurgical Geology Bureau;  
For studying the Late Yanshan magmatism in South China hinterland,and analyzing its petrogenesis and tectonic significance,this paper carries out systematical geochronological,geochemical and Sm-Nd isotopic investigations on the Kunlunguan granitic pluton in central Guangxi.LA-ICP-MS zircon U-Pb dating yields a weighted mean ~(206)Pb/~(238)U age of 97.7±1.3 Ma(MSWD=1.6),implying its Late Yanshan intrusion time.Geochemical compositions show that it is enriched in Si(SiO_2=69.42%-72.52%),alkali(total alkali=7.43%-8.43%),K(K_2O=4.00%-5.02%,K_2O/Na_2O=1.17-1.62),Al(Al_2O_3=13.65%-14.25%),but depleted in Ca(CaO=1.20%-2.78%).Rb,Th,U,K,Pb elements are enriched in the intrusion while Ba,Nb,Sr,P,Ti elements are depleted.REE is characterized by obvious negative Eu anomalies(δEu=0.45-0.61),and exhibits right-dipping patterns with LREE enrichment.Its aluminum saturation index value(A/CNK)ranges from 0.93 to1.16,while redman index value(δ)ranges from 2.06 to 2.41,indicating the intrusion belongs to high-K calc-alkaline series and metaluminous to peraluminous rocks.Itsε_(Nd)(t)value varies between-7.68 to-10.31,and the correspondent two-stage Nd isotopic modal ages range from 1.52 to 1.73 Ga(average value is 1.58 Ga).Mineralogy and geochemical characteristics indicate that Kunlunguan pluton is A-type granite.It has formed by partial melting of the Cathaysia paleoproterozoic felsic crustal material,being mixed with some mantle drived mafic malts,under a low-pressure,high-temperature condition at an extensional tectonic setting.Taking the igneous and metallogenic events in central Guangxi and adjacent areas into consideration,this study suggests that the lithosphere of South China hinterland thinned in 100-90 Ma.
【Fund】: 中国地质调查局地质矿产调查项目(No.121201009000150012)
【CateGory Index】: P588.121
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