Age constraints on the genesis of the Changkeng tungsten deposit, Nanling region, South China

Abstract

Abstract The Changkeng quartz vein tungsten deposit is located in the eastern part of the Helong ore field, Nanling region, South China. It has a proven WO3 reserves of 9680 tons WO3, and an average grade of 2.98%. It contains 28 ore-bearing quartz veins, and the mineralization stages are divided as follows: (I) quartz-wolframite-cassiterite-scheelite stage; (II) quartz-wolframite-scheelite-molybdenite-pyrite-sphalerite-galena-flourite stage; (III) quartz-calcite-flourite stage. The intrusion within the deposit is concealed, and comprising medium- and coarse-grained biotite monzogranite. Zircon grains from the Changkeng pluton have a U-Pb age of 156.7 ± 0.54 Ma (MSWD = 2.9). Cassiterite grains from stage I yield a weighted mean 206Pb/238U age of 156.1 ± 3.4 Ma (MSWD = 3.4). Molybdenite separates from stage II have a well-defined 187Re/187Os isochron age of 156.9 ± 2.0 Ma (MSWD = 0.77), with model ages ranging from 155.6 ± 2.5 to 157.5 ± 2.2 Ma. The zircon eHf(t) values range from −14.1 to −11.1, and the Hf two-stage model ages range from 1.87 to 2.06 Ga, indicating a primary reworking of the Paleoproterozoic crust. The low rhenium contents (0.3238 to 8.763 μg/g) in molybdenite suggest that the ore-forming materials was derived from a crustal source. The age consistence between the intrusion and mineralization, together with the Hf and Re isotope signature, all indicate a close genetic link between magmatism and mineralization. The Changkeng deposit is an example of a Jurassic regional-scale tungsten-tin ore-forming event between 160 and 150 Ma in the Nanling region, South China.