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Yang Y.,China University of Geosaences | Wang X.-X.,Chinese Academy of Geological Sciences | Ke C.-H.,Chinese Academy of Geological Sciences | Li J.-B.,Changan University
Geology in China | Year: 2012

The Shibaogou granitoid pluton, consisting of porphyritic monzogranite and middle-fine-grained monzogranite as well as mafic magma enclaves, is located in the southern margin of the North China Craton. The zircon LA-ICPMS dating of the porphyritic monzogranite and mid-fine-grained monzogranite from this pluton yielded ages of 156±lMa (MSWD=0.34, N= 15) and 157±1Ma (MSWD=0.10, N=17), respectively. The rocks are of high K cale-alkaline series and belong to metaluminous to weak peraluminous I-type granite with A/CNK being 0.82-1.02, Na2O+K2O 7.61%-8.91% and K2O/Na2O 1.02-1.48. Their PvEE and trace elements are enriched in large ion lithophile elements (LPvEE, Rb, Ba, K and Pb), and depleted in high-field strength elements (HPvEE, P and Ti), with slighdy negative to positive anomalies of Eu (δ Eu=0.81∼1.12). Zircon Hf isotopic compositions of the porphyritic monzogranite and middle-fine-grained monzogranite are mainly characterized by ξ Hf (t) values of-22.6-8.3 and -26.9-12.4, and the two-stage model ages of 2.64 to 1.73 Ga and 2.91 to 1.99 Ga, respectively. Geochemistry and zircon Hf isotopic compositions show that they were derived from an ancient continental crust (probably Archean Taihua Group), with the addition of juvenile components. Source

Qzhang J.,China University of Geosaences | Mao J.-W.,China University of Geosaences | Mao J.-W.,Chinese Academy of Geological Sciences | Cheng Y.-B.,China University of Geosaences | And 2 more authors.
Geology in China | Year: 2012

The Gejiu polymetallic tin ore district in Yunnan Province is the largest tin deposit in the world, and the Kafang copper (tin) deposit is a component part of this ore district. The stratoid ore body of the Kafang copper (tin) deposit, closely related to meta-basalt, is characterized by enriched copper. The basalt has been altered and the alteration intensity is related to the copper mineralization. This paper presents a new 110Ar- 39Ar phlogopite age for the meta -basalt in the Kafang tin -copper deposit in order to constrain the timing and duration of the alteration of basalt and the mineralization. Phlogopite yielded 110Ar-39Ar plateau age of 85.49±0.63 Ma, isochronal age of 85.6210.42 Ma, and inverse isochronal age of 85.59±0.81 Ma. These ages are substantially consistent with each other, pointing to late Cretaceous. These results are coincident with the data obtained from the Gejiu polymetallic tin-copper deposit. Source

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