Molybdenite Re-Os isochron age of the Chiwawu Mo-Cu deposit in Fuping County, Hebei Province in northern Taihang Mountains and its prospecting significance

The Chiwawu porphyry Mo-Cu deposit in the northern Taihang Mountains porphyry-skarn metallogenic belt is a medium-sized one discovered in recent years.The Mo-Cu orebodies are mainly hosted within porphyritic granodiorite of internal facies in Chiwawu pluton.In order to determine the age of mineralization and the source of molybdenum, seven molybdenite samples were collected from the Chiwawu Mo-Cu deposit for Re-Os dating.The Re-Os dating yields model ages ranging from129.1 Ma to130.6 Ma, with a weighted mean age of 129.7±0.7 Ma, and obtains an isochron age of 128.7±4.4 Ma.Evidently, model ages are consistent with isochron age within the error ranges, which constrains the ore-forming age of Chiwawu Mo-Cu deposit at the Early Cretaceous.The Re values of molybdenum vary in the range of 25.9×10^-6~37.1×10^-6, indicating that they were derived from mixing of crust and mantle sources.Combined with available chronologic data, it is recognized that a regional magmatic-metallogenic event might exist during the 134~124 Ma in northern Taihang Mountains.The prospecting potentiality of porphyry Cu-Mo deposits is great in this area.