Yang, Qun, Ren, Yun-sheng, Huizenga, Jan-Marten, Li, Jing-mou, Wang, En-de, Wang, Xi, and Wang, Bin (2021) Geological significance of Early Triassic porphyry Cu mineralization in the eastern Xar Moron–Changchun Metallogenic Belt, Northeast China: a case study of the newly-discovered Guokuidingzi Cu deposit. Ore Geology Reviews, 133. 104092.

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Abstract

The Guokuidingzi porphyry copper deposit is a poorly studied deposit located in the eastern Xar Moron-Changchun Mo–Cu Metallogenic Belt (XCMB) of the northern margin of the North China Craton. The Cu mineralization occurs mainly within the porphyritic granodiorite. Discovery of the Guokuidingzi deposit in the eastern XCMB is of great significance for understanding the regional porphyry Mo–Cu mineralization and metallogeny. To better understand the genetic relationship between Cu mineralization and associated magmatism, we in present study documented molybdenite Re–Os, zircon U–Pb geochronology, geochemical and in-situ zircon Hf isotope data in the Guokuidingzi deposit. The ore-related porphyritic granodiorite from the alteration center yields zircon U–Pb age of 251.2 ± 2.1 Ma (MSWD = 0.25) that is similar to zircon U–Pb age of 250.7 ± 2.0 Ma (MSWD = 0.56) yielded by the fresh porphyritic granodiorite. Both ages are consistent with molybdenite weighted average age of 250.0 ± 1.5 Ma (MSWD = 0.26). These similar ages constrain the timing of emplacement and associated Cu mineralization in the Guokuidingzi Cu deposit to the Early Triassic, and indicate a close temporal and genetic relationship between Cu mineralization and the porphyritic granodiorite. The Guokuidingzi porphyritic granodiorite is high in SiO2 Al2O3, K2O, Sr, Mg#, Sr/Y, LREE and LILE, and low in Y, Yb, Cr, Co, Ni, HREE and HFSE, as well as a weak negative Eu anomaly and positive εHf(t) values (+8.1 to +11.1), suggesting a geochemical affinity to high-K adakite-like rocks. The ore-forming porphyritic granodiorite was most likely formed by partial melting of thickened juvenile mafic lower-crust, which previously underwent underplating of mantle-derived components/or melts at the base of the crust. The geology, geochemistry, geochronology and tectonic setting of the Guokuidingzi Cu deposit in the eastern XCMB are similar to the Early to Middle Triassic porphyry deposits in the western XCMB (EW-trending), but differ from the Middle Jurassic porphyry deposits in the southern Lesser Xing’an–Zhangguangcai Ranges Metallogenic Belt (NS-trending). This important finding suggests that the XCMB extends eastward to the Jilin, and even to the Yanbian area, which indicates the need for further research on the Early to Middle Triassic porphyry mineralization potential and prospecting in the eastern XCMB. We propose that the Early Triassic Guokuidingzi and porphyry deposits in the XCMB were formed during ition from syn-collisional compression to post-collisional extension after the final closure of the Paleo-Asian Ocean.

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