Zircon U-Pb dating reveals Late Jurassic gold mineralization in the Jidong district of the northern North China Craton

Abstract

The North China Craton (NCC) hosts numerous gold deposits clustering in several districts, which combined have proven reserves of ~7000 t Au. Geochronological studies have shown that the craton-wide gold mineralization occurred mostly in the 140–120 Ma interval, coincident with the peak of thinning and destruction of the lithospheric keel beneath the NCC. Here we integrate geological relations with LA-ICP-MS zircon U-Pb dating to reveal a new gold mineralization event in the Jidong district, northern NCC. The Xiajinbao, Yu’erya and Jinchangyu gold deposits in this district are characterized by crosscutting relationships between gold veins and various dikes. This relation suggests that zircon U-Pb dating of the pre-ore and post-ore dikes can provide tight constraints on the time of gold veining. LA-ICP-MS zircon U-Pb dating of pre- and post-ore dikes from the three gold deposits yields concordant U-Pb dates of 165–163 Ma, 165–164 Ma and 165–164 Ma, respectively. These indistinguishable U-Pb dates within analytical uncertainty are interpreted as the timing of gold deposition (165–163 Ma) and thus reveal a previously unrecognized Late Jurassic gold mineralization event in the Jidong district. A large variety of mafic to intermediate dikes in the Jidong district have zircon U-Pb dates of 166 ± 1 to 164 ± 2 Ma, consistent with ages of the three gold deposits investigated. The temporal consistency and abundant sulfide inclusions hosted in the mafic-intermediate intrusions, along with the close spatial relations between gold veins and various dikes within and surrounding the mines, indicate a possible magmatic source for ore fluids. Synthesis of regional geological, geochemical and isotopic data led us to conclude that the Late Jurassic gold mineralization in the northern NCC is genetically related to lithosphere destruction of the NCC. An additional implication from this study is that the Mesozoic decratonization of the NCC and associated gold mineralization are spatially and temporally heterogeneous and much more prolonged than commonly thought.