Geochronology and geochemistry of the Shilu Cu-Mo deposit in the Yunkai area, Guangdong Province, South China and its implication

W. Zheng, J. Mao, Franco Pirajno, H. Zhao, C. Zhao, Z. Mao, Y. Wang

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

© 2014 Elsevier B.V. Shilu is a large porphyry-skarn deposit in the Yunkai district in Guangdong Province, South China. The Shilu granitic intrusion in the mine area is a granodiorite which is genetically related to Cu mineralization. Plagioclase in the granodiorite has a zoned texture and is mainly andesine with minor amounts of labradorite, whereas the K-feldspars exhibit Carlsbad twins and some are also characterized by a zonal texture. K-feldspars from the granodiorite show high contents of Or (87-92wt.%) with minor Ab (8-13wt.%) and negligible An value of 0-0.3wt.%. Biotite can be classified as magnesio-biotite, and is characterized by Mg-rich [Mg/(Mg+Fe)=0.54-0.60] and AlVI-low (average values=0.11). Hornblende is chiefly magnesiohornblende and tschermakite. LA-ICP-MS zircon U-Pb age of the Shilu granodiorite is 107±0.7Ma, which is consistent with molybdenites Re-Os age of 104.1±1.3Ma. Geochemical data indicate that the Shilu granodiorite is silica-rich (SiO2=63.43-65.03wt.%) and alkali-rich (K2O+Na2O=5.45-6.05wt.%), as well as calcium-rich (CaO=4.76-5.1wt.%). Trace element geochemistry results show enrichments in large ion lithophile elements (e.g., Rb, K, and Ba) and depletions in some high field strength elements (e.g., Nb, P, Ta, and Ti). The total rare earth element (REE) content of the granodioritic rocks is low (∑REE9] and moderately negative Eu anomalies (Eu/Eu*=0.83-0.90). These mineralogical, geochronological, and geochemical results suggest that the Shilu granodiorite has a mixed crust-mantle source with a geochemical affinity to I-type granitoids. Hornblende thermobarometry yielded magmatic crystallization temperatures of 686-785°C and crystallization pressures between 1.0 and 2.34kbar, which is converted to depths in a range of 3.31 to 7.71km. Biotite thermobarometry yielded similar temperatures and lower pressures of 680-780°C and 0.8-2kbar (depth 2.64-6.6km), respectively. The parent magma had a high oxygen fugacity. The Shilu granodiorite has a relatively low εNd/t-t value and high (87Sr/86Sr)i value, and Nd isotopes yield two-stage depleted mantle Nd model ages of 969-1590Ma. Our new data, combined with previous studies, imply that the granodiorite and the associated Shilu Cu-Mo deposit was formed in an extensional environment, closely related to remelting of residual subducted slab fragments in the Jurassic.
Original languageEnglish
Pages (from-to)382-398
JournalOre Geology Reviews
Volume67
Issue number1
DOIs
Publication statusPublished - Jun 2015

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