Zircon U-Pb Geochronology, Petrogenesis and Geological Implication of Ore-Bearing Granodiorite Porphyry in the Wulaga Gold Deposit, Heilongjiang Province
摘要
Heilongjiang is one of China’s most famous gold producing districts.Past production in the area was partially from epithermal gold mineralization,which was associated with the Mesozoic subaerial volcanic to subvolcanic intrusions.However,a little work has been done for the petrogenesis of these igneous rocks.In this paper,LA-ICP-MS zircon U-Pb ages,coupled with whole-rock major,trace elements and Sr-Nd-Pb isotopic data are present to constrain the geochronology and the petrogenesis of ore-bearing granodiorite in the Wulaga gold deposit,also discuss the epithermal gold mineralization potential of Heilongjiang Province.Two U-Pb zircon ages from Putaogou granodiorite intrusion and its southern ore-bearing granodiorite porphyry apophysis that occur in the Wulaga gold district are respectively 108.2±1.2Ma and 106±1.1Ma,which are similar to the age of surrounding volcanic rocks.Thus it is inferred that the gold mineralization hosted within the granodiorite porphyry apophysis was also formed in the Early Cretaceous,which was contemporaneous with the Dong’an gold deposit and Gaosongshan gold deposits.The granodiorite porphyry is the typically I-type,calc-alkaline(σ=1.83~2.18) granitoid with meta-aluminous attributes(A/NCK=0.97~1.16) .Geochemical and Sr-Nd-Pb isotopic features suggest that the granodiorite porphyry was likely derived from partial melting of the Neoproterozoic juvenile mafic low-crust,which is inferred to be the source of partial mineral-forming components by comparing with other gold deposits.Early Cretaceous magmatism favored an extensional regime in NE China,when complex tectonic activities occurred,at the same time as intense low crust-sourced magmatism.This result suggests that there is likely huge mineralization potential for epithermal gold deposits in the Heilongjiang Province,through comparison with regional mining epithermal gold deposits.