粤北地区塘洞岩体地球化学特征及地质意义OACSTPCD

Tangdong granite intrusion is located in the north of Changjiang uranium ore field,which has preferably uranium mineralization conditions.In this paper,the petrographic and geochemical analyses of Tangdong granite intrusion were carried out to initially explore the genesis and the tectonic setting.The results showed that:(1)Tangdong granite intrusion is a medium-grained dolomite granite with the characteristic of high potassium-calcium alkaline peraluminous granite of high SiO2(=72.77%～73.83%),rich aluminium(Al2O3=13.13%～13.82%),rich alkali(K2O= 5.00%～6.84%,Na2O=1.55%～2.67%),potassium greater than sodium,poor in iron,magnesium,calcium,titanium,phosphorus,and aluminium saturation index(A/CNK)is=1.08～1.28)greater than 1.1.(2)high total rare earths,light rare earth enrichment(LREE/HREE=8.45～12.86),moderate negative europium anomaly(δEu=0.24～0.30);(3)enrichment of large ionic lithophile elements Rb,Th,U,K,Pb,while depleted in Nb,Ta,Ti,Zr and other high field strength elements;(4)pond cave rock CaO/Na2O=0.16～0.58,Rb/Sr =5.01～8.19,Ra/Ba=0.90～1.94,indicating that its source area is a mixed of sandy rocks and mudstone,which belongs to S-type granite.The granite was mainly formed by partial melting of crustal material during the tectonic transition from collisional thickening to extensional thinning in the late synclinal phase.