V-Rich Minerals in Contact-Metamorphosed Silurian Sedex Deposits in the Poblet Area, Southwestern Catalonia, Spain

Abstract

The Lower Llandoverian metasedimentary rocks of the Prades Mountains, southwestern Catalonia, Spain, consist of interstratified anorthite-rich beds, chert beds, phosphate beds, sulfide-rich black shale (with mainly pyrrhotite and minor chalcopyrite), massive sulfide lenses and calc-silicate beds. These metasedimentary rocks are anomalously enriched in V and Cr, and have disseminated minerals of precious metals: mainly sperrylite and palladian löllingite. The V-and Cr-rich associations are the result of an isochemical metamorphism of V-and Cr-rich protoliths. The contact metamorphism of V-rich shale produced metapelitic hornfels with V-rich aluminosilicates and VCr oxides. The occurrence of V oxides in apparent equilibrium with Vrich silicates suggests a limit for the V and Cr contents in these aluminosilicates at the conditions of thermal metamorphism. On the other hand, metamorphism of anorthite-and VCr r-rich sedimentary rocks produced V-and Cr-rich silicates, such as goldmanite, V-rich amphiboles, V-rich titanite and V-rich allanite.

Metamorphic vanadian-chromian silicate mineralization in carbon-rich amphibole schists from the Male Karpaty Mountains, Western Carpathians, Slovakia

“…The carbon-rich schists contain, on average, around 2 wt% C org , 500 ppm V, 100 ppm Cr, 180 ppm Ni, 140 ppm Cu, and 3500 ppm Ti; and locally, up to 6000 ppm V, 1000 ppm Cr, 850 ppm Ni, 530 ppm Cu, and 1 wt% Ti (Table 1; Cambel and Khun 1983). Similar V enrichment and the presence of vanadian garnet and other V-rich silicates has been reported from several C-rich ("black shale") lithologies worldwide (e.g., Filippovskaya et al 1972;Karev 1974;Litochleb et al 1985;Benkerrou and Fonteilles 1989;Jeong and Kim 1999;Canet et al 2003). However, at least a fraction of the V, as well as a main portion of the Cr source originated from the mafic material of the volcanoclastic rocks.…”

“…Such V,Cr-rich metamorphic assemblages are very rare. Chromian goldmanite with other V-(Cr)-enriched silicates (titanite, allanite, biotite, amphiboles) and variegated V-Cr oxide minerals occur in metasedimentary rocks of the Poblet area, Spain (Canet et al 2003). Somewhat elevated Cr and Ti contents are reported in vanadian grossular to spessartine from the Domoradice graphite deposit, Czech Republic (Grs 23-49 Sps 27-49 : 0-7.5 mol% uvarovite, 0.5-3.6 mol% schorlomite and 0.2-25.6 mol% goldmanite; Černý et al 1995).…”

“…Vanadian grossular to goldmanite [Ca 3 V 2 (SiO 4 ) 3 ], a V-dominant member of the ugrandite garnet subgroup, is the most conspicuous mineral in such associations, together with other V-rich phases including micas, diopside, amphiboles, titanite, biotite, oxide minerals, and even sillimanite (e.g., Moench and Meyrowitz 1964;Karev 1974;Suwa et al 1979;Benkerrou and Fonteilles 1989;Canet et al 2003;Donohue and Essene 2005). Moreover, goldmanite has been described in refractory inclusions from the Leoville carbonaceous chondrite (Simon and Grossman 1992).…”

“…However, in the Poblet area, Spain, V-and Cr-rich goldmanite and other minerals have been described (Canet et al 2003). Donohue and Essene (2005) have also described chromian hercynite with vanadoan sillimanite.…”

“…Abbreviations of compositional fields: OG = Ogcheon belt, Korea(Jeong and Kim 1999); PB = Poblet area, Spain(Canet et al 2003); OT = V-bearing uvarovite from Outolumpu, Finnland(von Knorring et al 1986). …”