Geochemical features and petrogenesis of the Dajinshan granites in west Guangdong Province

Abstract：This paper aims at reporting the petrology and the geochemistry of the buried granite stock in Dajinshan area, which is composed mainly of medium to fine grained biotitic granitic rock and porphyritic biotic granitic rock. These granites are characterized by richness of silica and alkali and depletion of magnesium and calcium. In this study, all samples from Dajinshan are high-K calc-alkaline rocks, which are enriched in Rb, Th, U and depleted in Nb, Eu, Ti in the primitive mantle-normalized spidergrams. The REE values of medium to fine grained biotite granite and porphyritic biotite granite are 203.36×10-6~248.42×10-6 and 243.76×10-6~255.08×10-6 respectively. The medium to fine grained biotite granite body is slightly enriched in HREE whereas the porphyritic biotite granite is enriched in LREE. They all show prominent negative Eu anomalies with δEu values being 0.004~0.009 and 0.059~0.13. The εHf(t) values and two-stage Hf model ages of medium to fine grained biotite granite and porphyritic biotite granite are -2.05~-8.64, -0.92~-6.57 and 1277~1692Ma, 1204~1556Ma, respectively. Based on regional geological and granite geochemical data, it can be concluded that the Dajinshan granites were derived from the partial melting of the Mesoproterozioc continental crust under a crustal extension geodynamic setting during the Late Yanshanian period.