Citation: | ZHANG Kun, XU Deming, HU Junliang, LU Youyue, HUANG Hao. Petrogenesis of the granites in Sandun area-Constraints from petrochemistry, zircon U-Pb chronology and Hf Isotope[J]. Geological Bulletin of China, 2017, 36(9): 1591-1600. |
In this paper, the authors studied the petrogenesis and tectonic-significance of the granite from the Sandun Cu-Pb-Zn polymetallic deposit in northeastern Hu'nan Province by means of zircon U-Pb isotope chronology, whole rock geochemistry and Hf isotope. LA-ICP-MS zircon U-Pb dating yielded crystallization age of 131.9±1.1Ma for the Sandun granite. The Sandun granite is a peraluminous high-Al calc-alkaline intrusive granite. The rocks are characterized by high U, Ta, Pb and low Ba, Nb, Sr, Zr, Ti val-ues. The REE distribution patterns are strongly LREE enriched and HREE depleted, with weakly negative Eu anomalies. The Hf iso-tope analyses show that the εHf(t) values of the late Yanshanian granite zircons are between -5.9 and -2.4, and the two stage Hf model ages ranging from 1558Ma to 1338Ma, which indicates that its parental magma was derived from partial melting of rocks of Middle Proterozoic paleo-crust. Inherited zircon with an age of 749.5Ma has the εHf(t) of +4.8 and two stage Hf model age of 1355Ma, re-spectively, which indicates that its parental magma was mainly derived from the mantle. The Sandun granite probably resulted from the formation of the molten magma in the middle and lower crust and the formation of a small amount of mantle derived material.
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Geological sketch map of Sandun
Hand specimen (a) and crossed nicols photograph (b) of granite
Representative CL images for zircons with U-Pb ages
U-Pb concordia diagram (a) and 206Pb/238U age spectrum (b) of zircons form the granites
TAS(a)and SiO2-K2O(b)diagram of the granite
Chondrite-normalized REE patterns(a)and primitive mantlenormalized trace element spider diagram(b)of the granite
Histograms of εHf(t)(a)and Hf isotopic diagram(b)of zircons from the granite