The 40Ar/39Ar dating of quartz: new insights into the metallogenic chronology of the Jinchang gold deposit and its geological significance

Abstract

The Jinchang gold deposit has been extensively studied, but precise dates for its formation are debated. Native gold mainly occurs as inclusions within pyrite and quartz. In this study, we analysed quartz crystals coeval with gold precipitation from two different types of mineralization using the ArgusVI multi-collector noble gas mass spectrometer by the stepwise crushing technique to resolve the timing and genesis of gold mineralization. 40Ar/39Ar dating of quartz samples (J12Q) from breccia ore yields a plateau age of 109.87 ± 0.86 Ma, and an inverse isochron age of 109.87 ± 0.88 Ma. Quartz samples (J18Q) from vein ore yields a slightly younger plateau age of 107.76 ± 0.85 Ma, with an inverse isochron age of 107.76 ± 0.92 Ma. These dates place the ore-forming age of the Jinchang gold deposit at 107~110 Ma, much younger than previously published radiometric ages, suggesting the gold mineralization is spatio-temporally associated with the granite porphyry. The formation of the Jinchang gold deposit is consistent with the regional late Mesozoic porphyry-epithermal gold mineralization event in the Yanbian-Dongning area. Finally, our study shows that 40Ar/39Ar of quartz can be used as a powerful tool to date the formation ages of hydrothermal ore deposits.

Progressive crushing 40Ar/39Ar dating of a gold-bearing quartz vein from the Liaotun Carlin-type gold deposit, Guangxi, southern China

“…In contrast, the 40 Ar/ 39 Ar progressive crushing technique of fluid inclusions has overcome this obstacle, and PFIs and SFIs in a sample can potentially be separated by progressive crushing owing to their various volume and distinctive distribution characteristics 36 , 39 – 42 . Furthermore, we have demonstrated that an age spectrum and isochron line can be obtained from just one sample by 40 Ar/ 39 Ar progressive crushing, and using the 36 Ar/ 40 Ar vs 39 Ar/ 40 Ar inverse isochron diagram, contamination of excess 40 Ar, if present, can be eliminated by the initial 40 Ar/ 36 Ar ratio from the isochron 37 , 38 . Last but not least, the correlations of K, Ca, Cl and Ar isotopes derived from neutron irradiation have the potential to be used to obtain PFI and SFI ages 37 , 40 , 42 , 48 , and when combined with the initial 40 Ar/ 36 Ar ratio from the isochron, they also can be used to fingerprint the source and evolution history of the ore-forming fluids 31 , 32 , 40 , 43 , 62 , 63 .…”

“…The 40 Ar/ 39 Ar in vacuo progressive crushing technique for dating the ages of fluid inclusions has been improved and developed for thirty-five years 31 , 32 . This method has been widely applied to constrain the formation ages of hydrocarbon resources 33 , 34 , retrogression after high-ultrahigh pressure metamorphism 35 , 36 , and in particular, for direct dating of hydrothermal mineral deposits of cassiterite, sphalerite, and wolframite, and gangue minerals like mineralized quartz veins 32 , 37 – 43 . Nevertheless, this technique has not yet been successfully employed in sediment-hosted Carlin-type gold deposits, although mineralized quartz veins with abundant fluid inclusions are widely developed in this type of ore deposit.…”