Three Angolan carbonatites were selected to evaluate the change in composition of pyrochlores during magmatic evolution: the Tchivira carbonatites occur in a plutonic complex, the Bonga carbonatites represent hypabyssal carbonatites and the Catanda carbonatites are volcanic in origin. In Tchivira pyrochlore, zoning is poorly developed; fluorine is dominant at the Y site; chemical zoning may arise as a result of substitutions for Nb in the B site; and the rare earth element (REE), U, Th and large-ion lithophile element (LILE) contents are very low. Pyrochlores from Bonga show oscillatory zonation; the F and Na contents are lower than those in the pyrochlores from Tchivira; and as substitution of Na at the A site increases, the Th, U, REE contents and inferred vacancies also increase. Pyrochlores from Catanda display complex textures. They generally have a rounded corroded core, which is mantled by two or three later generations. The core composition is similar to the Bonga pyrochlores. The rims are enriched in Zr, Ta, Th, Ce and U, but depleted in F and Na. In pyrochlores from the Angolan carbonatites, the F and Na contents decrease from plutonic to volcanic settings and there is enrichment of Th, U and REE in the A site and Ta and Zr in the B site. Zoning may be explained by changes in the activity of F, due to the crystallization of fluorite or apatite in the plutonic and hypabyssal carbonatites, or to volatile exsolution in the volcanic carbonatites.

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.

The tin-rich polymetallic epithermal deposit of Poopó, of plausible Late Miocene age, is part of the Bolivian Tin Belt. As an epithermal low sulfidation mineralisation, it represents a typological end-member within the “family” of Bolivian tin deposits. The emplacement of the mineralisation was controlled by the regional fault zone that constitutes the geological border between the Bolivian Altiplano and the Eastern Andes Cordillera. In addition to Sn and Ag, its economic interest resides in its potential in critical elements as In, Ga and Ge. This paper provides the first systematic characterisation of the complex mineralogy and mineral chemistry of the Poopó deposit with the twofold aim of identifying the mineral carriers of critical elements and endeavouring to ascertain plausible metallogenic processes for the formation of this deposit, by means of a multi-methodological approach. The poor development of hydrothermal alteration assemblage, the abundance of sulphosalts and the replacement of löllingite and pyrrhotite by arsenopyrite and pyrite, respectively, indicate that this deposit is ascribed to the low-sulphidation subtype of epithermal deposits, with excursions into higher states of sulphidation. Additionally, the occurrence of pyrophyllite and topaz has been interpreted as the result of discrete pulses of high-sulphidation magmatic fluids. The δ34SVCDT range in sulphides (−5.9 to −2.8‰) is compatible either with: i. hybrid sulphur sources (i.e., magmatic and sedimentary or metasedimentary); or ii. a sole magmatic source involving magmas that derived from partial melting of sedimentary rocks or underwent crustal assimilation. In their overall contents in critical elements (In, Ga and Ge), the key minerals in the Poopó deposit, based on their abundance in the deposit and compositions, are rhodostannite, franckeite, cassiterite, stannite and, less importantly, teallite, sphalerite and jamesonite.

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The Lower Llandoverian metasedimentary series of the Prades Mountains, in southwestern Catalonia, Spain, consists of interbedded massive feldspar beds, composed of almost pure anorthite, with chert, phosphate beds, sulfide-rich black shale, massive sulfides and minor calc-silicate beds. The sulfides mainly consist of pyrrhotite with minor chalcopyrite. The metasedimentary rocks are anomalously V-and Cr-rich and contain disseminated minerals bearing precious metals, e.g., sperrylite and palladian löllingite. On the basis of the geological setting of ore formation and the textural relationships among the minerals, a sedex model is proposed for the primary origin of these deposits and occurrences. However, textural patterns and mineral compositions were modified during several episodes. Firstly, Hercynian deformation and associated regional low-grade metamorphism produced cleavage and small-scale veining in the primary associations. Later, contact metamorphism related to Late Hercynian intrusions annealed the mineral associations. A sulfidation stage of mineralization caused replacement of Pd-bearing löllingite by arsenopyrite. During this process, the arsenopyrite structure was unable to accommodate such high Pd contents and, consequently, Pd was precipitated as PdAs 2 and scarce small grains of native Pd, disseminated along the löllingite-arsenopyrite contact, in association with argentian gold, and tellurides and selenides of Au, Ag, Bi and Pb.