Constraints on the timing and genetic link of scheelite- and wolframite-bearing quartz veins in the chuankou W ore field, South China

Abstract

• LA-ICP-MS zircon analysis confirms age of ~237–227 Ma of the Granitic intrusion. • Diverse W deposit type in Chuankou shows accordant mineralization age. • Late Triassic W mineralization and magmatism are recognized. • Undiscovered granite in the deep part is associated to W mineralization. The Chuankou W ore field, located in the Nanling region, South China, is one of the famous W ore fields in China, which displays many of the metallogenic features commonly associated with granitic intrusion, including vein type scheelite and wolframite mineralization. The Chuankou W deposit is the most important deposit in the Chuankou ore field. The diverse W mineralization around the Chuankou pluton exhibits orderly zoning and comprises proximal wolframite-bearing quartz veins and distal scheelite-bearing quartz veins. The scheelite-bearing quartz veins occur invariably in sandstone and slate, whereas the wolframite-bearing veins are mainly hosted by the granite. Medium-grained muscovite granite exposed to the surface, while the hidden granite pluton in tunnel is mainly composed of fine-grained tourmaline-bearing granite. In situ zircon and hydrothermal wolframite U–Pb dating and molybdenite Re–Os dating techniques are used to refine the age spectra of granitic intrusion and W mineralization in the Chuankou area. Medium-grained muscovite granite and fine-grained tourmaline-bearing granite of the Chuankou granitic intrusion have zircon U–Pb ages of 237 Ma and 227 Ma, respectively. The molybdenite Re–Os age of the scheelite-bearing quartz veins is 212.5 ± 7.3 Ma, which is consistent with the U–Pb age of the hydrothermal wolframite from wolframite-bearing quartz vein (212.6 ± 1.4 Ma). The combined chronology data collectively indicate that the two types of W mineralization have a temporal and genetic link. Our new magmatism and mineralization dates in the Chuankou deposit demonstrated that Nanling region has an enormous potential for Indosinian W mineralization and more attention should be given to the Indosinian ore prospecting in the region. These similar ore-forming ages demonstrate that the W mineralization type may be controlled by the lithologies of wall-rock which can provide Ca for scheelite and Fe/Mn for wolframite. The two mineralization ages are significantly inconsistent with the zircon U–Pb age of the Chuankou pluton, which may indicate that granite only plays a wall rock role in the formation of wolframite-bearing quartz veins. The W mineralization in the Chuankou is interpreted to be genetically related to a hidden Late Triassic granitic pluton. By studies of the high-precision geochronological, the genetic model of the W mineralization of the Chuankou deposit precludes genetic link between the W mineralization and Chuankou pluton and predicts a metallogenic granite in the deep part of Chuankou pluton have not been exposed.