The Giant Chalukou Porphyry Mo Deposit, Northeast China: The Product of a Short-Lived, High Flux Mineralizing Event

Zhao, Qingqing; Zhai, Degao; Mathur, Ryan; Liu, Jiajun; Selby, David; Williams-Jones, Anthony E.

Abstract

Whether giant porphyry ore deposits are the products of single, short-lived magmatic-hydrothermal events or multiple events over a prolonged interval is a topic of considerable debate. Previous studies, however, have all been devoted to porphyry Cu and Cu-Mo deposits. In this paper, we report high-precision isotope dilution-negative-thermal ionization mass spectrometric (ID-N-TIMS) molybdenite Re-Os ages for the newly discovered, world-class Chalukou porphyry Mo deposit (reserves of 2.46 Mt @ 0.087 wt % Mo) in NE China. Samples were selected based on a careful evaluation of the relative timing of the different vein types (i.e., A, B, and D veins), thereby ensuring that the suite of samples analyzed could be used to reliably determine the age and duration of mineralization. The molybdenite Re-Os geochronology reveals that hydrothermal activity at Chalukou involved two magmatic-hydrothermal events spanning an interval of 6.92 ± 0.16 m.y. The first event (153.96 ± 0.08/0.63/0.79 Ma, molybdenite ID-N-TIMS Re-Os age) was associated with the emplacement of a granite porphyry dated at 152.1 ± 2.2 Ma (zircon laser ablation-inductively coupled plasma-microscopic [LA-ICP-MS] U-Pb ages), and led to only minor Mo mineralization, accounting for <10% of the overall Mo budget. The bulk of the Mo (>90%) was deposited in less than 650 kyr, between 147.67 ± 0.10/0.60/0.76 and 147.04 ± 0.12/0.72/0.86 Ma (molybdenite ID-N-TIMS Re-Os ages), coincident with the emplacement of a fine-grained porphyry at 148.1 ± 2.6 Ma (zircon LA-ICP-MS U-Pb ages). The high-precision Re-Os age determinations presented here show, contrary to the finding of a number of studies of porphyry Cu and Cu-Mo systems, that the giant Chalukou porphyry Mo deposit primarily formed in a single, short-lived (<650 kyr) hydrothermal event, suggesting that this may also have been the case for other giant porphyry Mo deposits.

Citation

Zhao, Q., Zhai, D., Mathur, R., Liu, J., Selby, D., & Williams-Jones, A. E. (2021). The Giant Chalukou Porphyry Mo Deposit, Northeast China: The Product of a Short-Lived, High Flux Mineralizing Event. Economic geology and the bulletin of the Society of Economic Geologists, 116(5), 1209-1225. https://doi.org/10.5382/econgeo.4818

• Journal Article Type: Article
• Acceptance Date: Nov 6, 2020
• Online Publication Date: Feb 16, 2021
• Publication Date: Aug 1, 2021
• Deposit Date: Apr 29, 2021
• Publicly Available Date: Aug 1, 2022
• Journal: Economic Geology and the Bulletin of the Society of Economic Geologists
• Print ISSN: 0361-0128
• Electronic ISSN: 0361-0128
• Publisher: Society of Economic Geologists
• Peer Reviewed: Peer Reviewed
• Volume: 116
• Issue: 5
• Pages: 1209-1225
• DOI: https://doi.org/10.5382/econgeo.4818