Abstract

The Shangfang deposit is a recently discovered large-scale tungsten deposit (66,500 t at 0.23% WO3), which is located near the western boundary of the Southeastern Coastal Metallogenic Belt (i.e., Zhenghe–Dafu fault), and adjacent to the northeast of the Nanling Range Metallogenic Belt. Unlike many other W–Sn deposits in this region that occur within or near the granites, the orebodies in the Sangfang deposit all occur within the amphibolite of Palaeoproterozoic Dajinshan Formation and have no direct contact to the granite. In this study, we carry out a thermal ionization mass spectrometer (TIMS) Sm-Nd isotope analysis for the scheelites from the orebody, which yields a Sm–Nd isochron age of 157.9 ± 6.7 Ma (MSWD = 0.96). This age is in good agreement with the previously published zircon U–Pb age (158.8 ± 1.6 Ma) for the granite and the molybdenite Re–Os age (158.1 ± 5.4 Ma) in the deposit. Previous studies demonstrated that the W–Sn deposits occurring between Southeastern Nanling Range and Coastal Metallogenic Belt mainly formed in the two periods of 160–150 Ma and 140–135 Ma, respectively. The microthermometry results of fluid inclusions in scheelite and quartz are suggestive of a near-isothermal (possibly poly-baric) mixing between two fluids of differing salinities. The H–O isotope results illustrate that the ore-forming fluids are derived from magma and might be equilibrated with metamorphic rocks at high temperature. The Jurassic granite pluton should play a critical role for the large hydrothermal system producing the Shangfang W deposit. Furthermore, the negative εNd(t) of −14.6 obtained in the Shanfang scheelite suggests for the involvement of the deep crustal materials. In general, subduction of the paleo-Pacific plate caused an extensional tectonic setting with formation of the Shangfang granites and related W mineralization, the geological background of which is similar to other W deposits in the Nanling Range Metallogenic Belt.

Highlights

  • Tungsten (W) is a critical metal that has been widely used for the new industrial products

  • As one of the dominant mineral resources, most of the W deposits are found in three metallogenetic belts in South China

  • The Southeastern Coastal Metallogenic Belt is located at the continental margin of Eurasia, and is adjacent to the southeast of the Nanling Range Metallogenic Belt

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Summary

Introduction

Tungsten (W) is a critical metal that has been widely used for the new industrial products (e.g., filaments, electrodes, projectiles, catalysts). As one of the dominant mineral resources, most of the W deposits are found in three metallogenetic belts in South China (i.e., the Nanling Range, Southeastern Coast, and Jiangnan Orogen). All of these large-scale mineral systems in South China are genetically related to the Mesozoic granites but with different minerogenetic. Several granite-related large-scale W–Cu and W–Mo deposits (WO3 : more than 5.0 million tons) have been discovered in the Jiangnan Orogen, which is located in the southeast margin of Yangtze Craton, and to the south part of Middle–Lower Yangtze River Valley. The Southeastern Coastal Metallogenic Belt is located at the continental margin of Eurasia, and is adjacent to the southeast of the Nanling Range Metallogenic Belt

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