Zircon U-Pb Geochronology, Geochemistry And Petrogenesis Of The Taocunba Granite, Northern Guangdong Province

Nanling tectonic belt is an important granitic uranium deposit which developed on severe deformation folding basement. This belt developed large-volume granite and rift basins in south china during later Mesozoic. The Guidong pluton, locating in the south central Cathaysian and east central of Dadongshan-Guidong-Wuliting granite belt, belongs to Nanling tectonic belt. This pluton regionally located at the cross of post Caledonian uplift of Fujian and Jiangxi province, and hollow zone of Hunan, Guizhou and north Guangdong province.The Guidong pluton is composed of Xiazhuang, Luxi, Maofeng, Sundong, Siqian, Taocunba granite and so on. Taocunba granite is located at the junction of the east and west of the Guidong composite granite batholith. The east is researched Earlier for uranium mineralization concentrated. By contrast, the Western research is relatively weak, and only a small amount of mineralized points are founded, and the uranium deposit of industrial value is not found. Although there are some studies on petrology of the western granite, the research degree is relatively weak. Especially for the Taocunba granite, although the predecessors told it individually according to regional geological data, they did not study it further. This article detailed researches the granite from the viewpoint of chronology, element geochemistry and isotope geochemistry for the first time, to find out the formation age of the granite, the source of diagenetic material, genetic type and tectonic setting, in order to further clarify your geochemical differences between the eastern and the western of the Guidong composite granite batholith, as well as to study uranium metallogenic potential of the granite.The Taocunba granite is one of the granitic plutons locating 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±1.8Ma(MSWD=1.7), suggesting that it was formed in the Early Yanshanian period. Chemically, the granites of the Taocunba ploton are peraluminous, and low in silicon, calcium and magnesium, and rich in alkalis with potassium higher than sodium. They also show high FeO*/MgO ratios. On trace element aspect, they are characterized by enrichment of Rb, Th and U and depletion of Ba, Sr, Ti and Nb. They also display enrichment of LREE (LREE/HREE=7.39-16.4, (La/Yb)N=8.79-25.5) and evident depletion of Eu (δEu=0.44-0.59). Furthermore, the granites have high Ga/Al ratios with a mean value of 2.99, and Zr+Nb+Ce+Y contents of them 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 1.66-1.76Ga, 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 extension setting.