Dexing copper ore field, one of the most typical porphyry deposits in South China, is composed of Zhushahong, Tongchang, Fujiawu ore deposits. Based on petrographic investigation of drill core samples, the mineralized granodiorite porphyries at Zhushahong deposit are divided into three altered rock types, namely, the biotite-potassium feldspar alteration type, chlorite alteration type, and quartz-sericite (muscovite) alteration type. The alteration intensity of the three types rock changes from low through intermediate to high in sequence. According to the immobility of Al2O3, the Isocon analysis shows that during the hydrothermal alteration, the major elements (P2O5) as well as high field strength elements (e. g. Zr, Y, Nb, Ta and Hf) and transitional elements are almost immobile, while Na2O and Sr are strongly depleted. Metallic elements of Cu, Pb and W dramatically move in, indicating that the hydrothermal fluid responsible for alteration and the ore-forming fluid may belong to the same fluid system. The chondrite-normalized REE distribution patterns of all samples show typical flat to listric-shaped patterns and reflect crystallization of amphibole. In terms of net element gain and loss, chlorite alteration rocks have undergone net REE loss, while the muscovite-quartz alteration porphyries shows great difference, the behavior of LREE/HREE is contingent on the samples. The Y/Ho ratios are similar to those of CI chondrite, which indicates that Y and Ho show a similar geochemical behaviour during hydrothermal alteration. The ganodiorite porphyry rocks have high Sr/Y and La/Sm ratios and medium Sm/Yb ratios, indicating a magma source with the residual phases of amphibole and/or garnet.
Publication name |
ACTA PETROLOGICA SINICA Volume: 28 Issue: 12 Pages: 3869-3886 Published: DEC 2012 |
Author(s) |
Wang CuiYun; Li XiaoFeng; Xiao Rong; Bai YanPing; Yang Feng; Mao Wei; Jiang SongKun |
Corresponding author |
WANG Cuiyun wang1988cuiyun@163.com Chinese Acad Sci, Inst Geochem, State Key Lab Geochem Res, Guiyang 550002, Peoples R China. |
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