关键词: A型花岗岩；锆石U-Pb定年；地球化学；粤北

Abstract:

The Taocunba granite is one of the granitic plutons located within the central part of the Guidong composite granite batholith
in northern Guangdong province. LA-ICPMS zircon U-Pb dating yields an age of 161.5±1.8 Ma(MSWD=1.7), suggesting that it was
formed in the Early Yanshanian period. Geochemically, the granites of the Taocunba pluton are peraluminous, and low in silicon,
calcium and magnesium, and rich in alkalis with potassium content higher than sodium. They also show high FeO*/MgO ratios. The
trace elements are characterized by the enrichment in Rb, Th and U and the depletion in Ba, Sr, Ti and Nb. They also display
enrichment in LREE (LREE/HREE=7.39~16.4, (La/Yb)N=8.79~25.5) and evident depletion in Eu (δEu=0.44~0.59). Furthermore, the
granites have high Ga/Al ratios with a mean value of 2.99 and their Zr+Nb+Ce+Y contents are over 350×10-6, showing affinity with
A2-type granites. Isotopically, they have low εNd(t) values (-9.7~-8.95) with two-stage Nd model ages of 1.66~1.76 Ga and low εHf(t)
values (-20.0~-14.6) with Hf model ages of 2.12~2.46 Ga. Taken together, these features indicate that the granites of the Taocunba
pluton were derived from partial melting of the Paleoproterozoic crustal rocks under an extensional setting.

Key words: A-type granite, zircon U-Pb geochronology, geochemistry, northern Guangdong