The Qidushan pluton in southern Jiangxi Province is the parent rock of heavy rare earth mineralization in the Shitouping deposit,but the understanding of its emplacement age,petrogenesis,rock type and tectonic environment is insufficient.In this paper,zircon and monazite U-Pb dating,rock geochemistry and Sr-Nd isotope of biotite syenite in the Qidushan pluton were studied.The results show that U-Pb ages of zircons and monazite are 145.0±2.3 Ma and 147±1.7 Ma,respectively,which belong to the Early Cretaceous magmatic activity.The rocks have high SiO2(72.78%～77.67%),rich potassium(K2O/Na2O=1.07～1.38),low Al2O3(12.03%～13.18%),peraluminous-strong peraluminous(A/CNK=1.08～1.25),and the REE classification pattern is seagull type.The enrichment of Rb,Th,U and other elements,the loss of Ba,Sr,Eu and other elements,and the slightly higher saturation temperature of zircons(761～834℃)are indicative of the characteristics of peraluminous A-type granite.In addition,the rocks show high content of Rb(277.6×10-6～901.3×10-6),Rb/Sr ratio(8.07～195.93),displaying high differentiation characteristics of granite.In summary,the Qidushan pluton is a highly differentiated peraluminous A-type granite.The variation of εNd(t)ranges from-4.1 to-3.0(>-7.0),which is consistent with the involvement of mantle material in the diagenesis process.The mantle material mainly provides much heat but few material contributions in the diagenesis.According to the regional geology and tectonic illustrations,it is suggested that the intrusion of pluton is related to the lithospheric extension caused by the subduction and retraction of the ancient Pacific Plate.
A-type graniteU-Pb datingSr-Nd isotopeheavy rare earthQidushan plutonsouthern Jiangxi Province
维普
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