China
Africa
Explore chapters and articles related to this topic
Introduction
Published in J. R. Coaton, A. M. Marsden, Lamps and Lighting, 2012
Wolframite (FeMnWO4) and Scheelite (CaWO4) are the most important tungsten-bearing ores of current commercial interest; Ferberite (FeWO4) and Huebnerite (MnWO4) are of somewhat lesser importance. Generally, the benificiated ore containing >60 per cent WO3 is treated (purified) with alkali hydroxides to form ammonium paratungstate (APT). APT is decomposed to tungsten oxides by heating in hydrogen, and at this stage the all-important dopant solutions containing Al2O3, K2O and SiO2 [AKS] are added. The doped powder is then reduced to the metal by heating in hydrogen. Finally, the doped powder is compacted into ingots which are sintered to ~95 per cent density in hydrogen and then swaged, rolled and drawn to wire of the required diameter. A typical processing route from ore to filament wire is given in Figure 6.2.
Cretaceous tungsten-tin mineralisation in the Tin Range, Stewart Island, New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2022
Hamish C. Lilley, James M. Scott, Josh J. Schwartz, Rose E. Turnbull, Andy J. Tulloch
Element scavenging from nearby aluminosilicate-rich host rocks may have been important for wolframite precipitation in the geologically similar Panasqueira W-Sn greisen deposit (Portugal), with the host rock Fe-Mn ratio being directly related to Fe-Mn ratios within the wolframite ((Fe,Mn)WO4) (Lecumberri-Sanchez et al. 2017). EDS analysis of the biotite in the unaltered Pegasus Group schist shows FeO-concentrations of between ∼18–20%, but MnO content was too low for EDS detection. This high FeO content of the biotite may explain why the Tin Range wolframite is close to the Fe-endmember, ferberite (Fe67.8Mn32.2). In contrast, only minor greisenisation and mineralisation is found in the mica-poor Pegasus Group quartzite.
The Hübnerite/Ferberite ratio as an exploration tool for W-deposits
Published in Applied Earth Science, 2019
J. A.-S. Michaud, M. Pichavant
Understanding wolframite deposition processes is key to the development of reliable exploration guides for vein-type W-deposits. In the Variscan belt and elsewhere, wolframites show a wide range of compositions ranging from hübnerite (MnWO4) to ferberite (FeWO4). Deposition style, source of Mn and Fe, distance from the heat/fluid source and temperature have been proposed to be important factors controlling the wolframite hübnerite/ferberite ratio (H/F ratio; 100 at. Mn / (Fe+Mn)). The Argemela mineralised district, located near the Panasqueira W world-class mine (Portugal), contains a quartz-wolframite intragranitic vein system that is closely spatially and genetically associated with a rare-metal granite (RMG). Wolframite mostly occurs as large homogeneous hübnerite (H/F = 64–75%). Locally, early wolframite evolves to more Fe-rich compositions (H/F = 45–55%). Field, structural, mineralogical and geochemical evidence suggests that the intragranitic wolframite-bearing veins are the expression of magmatic fluids exsolved from the granite at the magmatic-hydrothermal transition. Thus, W and Mn both have a magmatic origin and interactions with host rocks or involvement of an external fluid are negligible. In one quartz vein hosted within the country rocks, early wolframites have Fe-rich hübnerite compositions (H/F = 50–63%) while late wolframites, occurring as recrystallised rims, have very low H/F ratios (H/F = 6–23%). Such a compositional gap suggests that Fe has been added to the ore fluid via fluid/country rocks interactions, a mechanism already proposed for ferberite deposition at Panasqueira. In W deposits across the Variscan belt, wolframites generally have low H/F ratios and hübnerites, such as those found in the Argemela district, are uncommon. Wolframites from greisens generally have intermediate H/F ratios whereas veins hosted in metamorphic country rocks contain wolframites with low to extremely low H/F ratios. Thus, hübnerite crystallisation is a marker of a strong magmatic imprint while intermediate to low H/F ratios are the expression of fluid/rock (involving either granite or country rocks) interactions. A parallel can be made between the H/F ratio, the marker of W-deposition mechanisms, and deposit type/commodity. High H/F ratios are characteristic of RMG and pegmatite generally mined for quartz-feldspar, kaolin and/or disseminated Li-Sn-Nb-Ta minerals. Wolframites with intermediate H/F ratios occur in greisens which are resources mainly for Li-Sn-Nb-Ta±W whereas low H/F ratios are characteristic of country rock-hosted vein swarms/stockworks which can form major W±Sn deposits. Thus, the H/F ratio appears as a reliable tool for the exploration of a wide range of commodities, in addition to wolframite (Figure 1).