Early Jurassic porphyry copper mineralization in NE China: A case study of the Yanghuidongzi deposit

The Yanghuidongzi Cu deposit is located in the southeastern part of Heilongjiang Province in NE China and represents one of the few known Early Jurassic porphyry Cu deposits within the eastern edge of the Xing'an-Mongolia Orogenic Belt. Here we present new whole-rock major and trace element and Sr-Nd isotopic data, zircon U-Pb and Hf isotopic data, and molybdenite Re-Os data for units associated with the deposit. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) dating of zircons from the granodiorite porphyry in the study area yielded ages of 191.0 +/- 1.1 and 191.2 +/- 1.0 Ma that are interpreted to be the emplacement age of this intrusion. The molybdenite Re-Os dating undertaken during this study yielded model ages of 192.7-187.0 Ma, an isochron age of 188.2 +/- 3.8 Ma, and a weighted mean model age of 190.2 +/- 2.6 Ma, representing the timing of formation of the Cu mineralization in this area. The Yanghuidongzi granodiorite porphyry contains relatively high concentrations of SiO2 (68.88-72.49 wt%), Al2O3 (15.37-16.31 wt%), and Sr (230-479 ppm), but relatively low concentrations of Y (7.97-9.87 ppm) and Yb (0.72-0.85 ppm), suggesting that this intrusion has an adakitic affinity. Combining this with the positive epsilon Nd (t) (0.7-1.1) and epsilon Hf(t) values (4.0-6.9), low Mg-# values (41-50), and the low concentrations of MgO (0.86-1.22 wt%), Cr (3.17-4.37 ppm), and Ni (2.11-4.20 ppm) within this intrusion suggests it formed from a magma generated by the partial melting of juvenile lower crustal material during the Early Jurassic subduction of the Paleo-Pacific Plate.