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

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.

Fluorine-rich mafic lower crust in the southern Rocky Mountains: The role of pre-enrichment in generating fluorine-rich silicic magmas and porphyry Mo deposits

“…Hence, silicic melts with >2000 ppm F and F/Cl near unity can differentiate rapidly; over shorter time frames than the full lifespan of porphyry Mo systems (100's to 1000's of k.y. ; Gaynor et al 2019;Zhao et al 2021). Existing models have hypothesized that S in porphyry Mo is introduced by small volumes of mafic melts, rather than being from the causative silicic magmas (Mercer et al 2015).…”

The key role of volatile‐rich magma in the formation of porphyry molybdenum deposits: A case study of the Chalukou deposit, China

“…Extensive magmatic activities, and its intermediate‐acidic intrusive rocks are relatively well‐developed in the Chalukou deposit. These rocks can be divided into three episodes, that is, pre‐mineralization monzogranite, syn‐mineralization quartz porphyry, fine‐grained porphyry and granite porphyry, and post‐mineralization feldspar porphyry (Zhao et al, 2021).…”

“…(a) Regional geological map of the Chalukou ore district (modified after Xiong, He, Yao, Cui, Shi, et al, 2014). (b) Geological map of the Chalukou deposit (modified after Zhao et al, 2021). …”

Discrete late Jurassic Sn mineralizing events in the Xianghualing Ore District, South China: Constraints from cassiterite and garnet U-Pb geochronology

“…See http:/www.minsocam.org or GeoscienceWorld because the distal skarn and vein-type orebodies commonly lack an obvious spatial association with granitic plutons and their distribution is controlled mostly by stratigraphy and faults, the genetic relationships between these orebodies and the causative plutons are difficult to determine (Newberry et al, 1991;Baker et al, 2004;Wu S et al, 2018). This difficulty is compounded by the fact that the ages of distal skarns and their associated mineralization are rarely known to the required degree of accuracy (Chiaradia et al, 2009(Chiaradia et al, , 2013Zhai et al, 2014Zhai et al, , 2019Zhao et al, 2021).…”