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Xie G.Q.,Chinese Academy of Geological Sciences | Ren T.,No.713 Geological Team | Li J.B.,No.713 Geological Team | Wang R.T.,Geological Exploration Institution | And 4 more authors.
Acta Petrologica Sinica | Year: 2012

There have plenty of Cu-Mo deposits ( occurrences) which are genetically associated with intermediate-acid granitoid stock from the Zhashan basin in the Qinling Orogenic Belt, recently huge copper orebody has been discovered in the Chigou Cu-Mo deposit region, but the timing and petrogenesis of ore-bearing granitoids were poorly constrained. In this contribution, ore-bearing granitoids for the Chigou Cu-Mo deposit were selected: geochemistry and LA-MC-ICPMS zircon U-Pb data for these rocks have been carried out. They are dominantly quartz diorite, diorite and porphyritic granite in petrology, and geochemically belong to high potassic calc-alkaline I-type granitoid, geochemical and Sr-Nd isotopic evidence demonstrate that these rocks originated from partial melting of upper mantle and lower crust. The weight average 206Pb/238 U ages for these ore-bearing granitoids are ∼ 145 Ma. In combined with regional geological characteristics and relation between igneous rocks and mineralization, it is proposed that the Chigou ore-bearing igneous rocks were formed during the Late Jurassic-Early Cretaceous time, and it is indicated that there have regional Late Jurassic- Early Cretaceous granitoid and porphyry-skarn Cu-Mo ploymetallic deposits in the Zhashan basin, synchronously the formation of granitoid batholith or stock and the corresponding porphyry Mo-hydrothermal vein Zn-Pb-Ag deposits in South margin of North China Craton.

Xie G.,Chinese Academy of Geological Sciences | Mao J.,Chinese Academy of Geological Sciences | Wang R.,Geological Exploration Institution | Ren T.,Northwest Mining and Geological Exploration Bureau for Nonferrous Metals | And 2 more authors.
Journal of Asian Earth Sciences | Year: 2015

The newly discovered porphyry Cu deposits in the South Qinling Belt (SQB) have not been well researched as compared with the large porphyry Mo province in the southern North China Block (S-NCB), and the origin of granitoids associated with porphyry Cu mineralization in the Zha-Shan district, SQB is poorly constrained. Here, we present detailed zircon U-Pb geochronological, whole rock elemental and Sr-Nd isotopic data for important Late Mesozoic granitoid stocks associated with porphyry Cu deposits in the Zha-Shan district; these data are used to constrain the age and the source of magmas that formed these granitoids, and implication of regional metallogeny. The new zircon LA-ICPMS U-Pb ages presented here indicate that the granitoids related to porphyry Cu system at Chigou, Beishagou, Shuangyuangou and Yuanjiagou developed at 148-144Ma, 144Ma, 145-144Ma and 146Ma, respectively. These rocks are high-K calc-alkaline I-type granitoids, which are enriched in large ion lithophile elements (e.g., Th, U, and Pb) and light rare earth elements, are depleted in Nb, Ta and Ti, characterizing by wide variations in initial εNd(t) (-3.8 to -9.5), and moderate radiogenic Sr isotopes ((87Sr/86Sr)i=0.7046 to 0.7093). These features indicate that the magmas that formed the granitoids related to porphyry Cu system in the Zha-Shan district formed as a result of variable degrees of mixing between crustal and metasomatic lithospheric mantle. The new zircon LA-ICPMS U-Pb ages in this study, combined with previous published data, suggest that regional-scale Late Jurassic to Early Cretaceous granitoid stocks, and associated porphyry Cu and Mo systems in both the S-NCB and SQB formed almost contemporaneously, with 147-139Ma porphyry Mo deposits in the S-NCB and 148-145Ma porphyry Cu deposits in the SQB. The Cu-related intrusions contained a greater contribution of lithospheric mantle component than the Mo-related intrusions in the East Qinling Orogeny. © 2014 Elsevier Ltd.

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