Abstract
The large-scale Maoping W–Sn deposit in the Gannan metallogenic belt of the eastern Nanling Range, South China, spatially associated with the Maoping granite pluton, hosts total ore reserves of 103,000 t WO3 and 50,000 t Sn. Two different types of mineralization developed in this deposit: Upper quartz vein-type mineralization, mostly within the Cambrian metamorphosed sandstone and slate, and underneath greisen-type mineralization within the Maoping granite. Cassiterites from both types of mineralization coexist with wolframite. Here we report for the first time in situ U–Pb data on cassiterite and zircon of the Maoping deposit obtained by LA-ICP-MS. Cassiterite from quartz vein and greisen yielded weighted average 206Pb/238U ages of 156.8 ± 1.5 Ma and 156.9 ± 1.4 Ma, respectively, which indicates that the two types of mineralization formed roughly at the same time. In addition, the two mineralization ages are consistent with the emplacement age of the Maoping granite (159.0 ± 1.5 Ma) within error, suggesting a close temporal and genetic link between W–Sn mineralization and granitic magmatism. The two types of mineralization formed at the same magmatic-hydrothermal event. Cassiterite from both types of mineralization shows high Fe, Ta, and Zr contents with a low Zr/Hf ratio, suggesting that the ore-forming fluid should be derived from the highly differentiated Maoping granite pluton. Cassiterite in greisen has higher contents of Nb and Ta but a lower concentration of Ti compared with that in quartz vein, indicating that the formation temperature of greisen-type mineralization is little higher than that of quartz-vein-type mineralization.
Highlights
China accounts for 65% and 29% of the global total tungsten and tin reserves, respectively [1,2].The Nanling metallogenic belt in south China is the most important tungsten and tin production region, accounting for approximately 83% of tungsten resources and 63% of tin resources of China [3].The Gannan metallogenic belt (Figure 1A), as the eastern part of the Nanling metallogenic belt, is characterized by large-scale tungsten mineralization and contains 1.42 Mt of proven tungsten resources, which quartz vein-type tungsten deposits dominate [4]
Structures using a JEOL JXA–8100 M electron microprobe equipped with a MonoCL (Gatan, LA-ICP-MS zircon U–Pb dating was performed using an Agilent 7500a ICP–MS attached to a 213 nm Pleasanton, USA)
LA-ICP-MS zircon U–Pb isotopic analyses were performed on two samples
Summary
China accounts for 65% and 29% of the global total tungsten and tin reserves, respectively [1,2]. Previous studies yielded age constraints on W–Sn mineralization in the Gannan metallogenic belt using K–Ar, 40 Ar–39 Ar, Sm–Nd, and Rb–Sr dating of whole-rock/mineral [10,11,12] and Re–Os dating of molybdenite [8,13]. These dated minerals, may not have temporal and genetic relationships to W–Sn deposition and/or may have been subjected to a disturbance in their isotopic system due to later hydrothermal alteration and thermal events. We combine the zircon and cassiterite U–Pb dating techniques to constrain the timing of granitic magmatism and the two different types of mineralization in the Maoping deposit. We determine whether or not the two different types of mineralization are the products of the same magma-hydrothermal mineralization event
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