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The Traspena meteorite fell on 2021 January 18 about 20 km south-east of the city of Lugo (Galiza, Spain), shortly after a huge and bright fireball crossed the sky for 4.84 s. Astrometric measurements obtained from the fireball cameras of the Universidade de Santiago de Compostela (USC) as well as from many casual videos were used to determine the atmospheric trajectory of this meteoroid which penetrated the atmosphere and generated sound waves that were detected at three seismic stations. The original meteoroid had a diameter of about 1.15 m and a mass around 2620 kg. It impacted the Earth’s atmosphere with a steep entry angle of about 76 . ◦7 from a height of 75.10 km until fading away at 15.75 km with a velocity of 2.38 km s −1 . Before the impact, this small asteroid was orbiting the Sun with a semimajor axis of 1.125 au, a moderate eccentricity of 0.386, and a low inclination of 4 . ◦55. A weak evidence of dynamic link with the PHA (Potential Hazardous Asteroid) Minos was investigated. During the atmospheric entry, two major fragmentation events occurred between heights of 35 and 29 km at aerodynamic pressures between 1 and 5 MPa. The strewn field was computed after calculating the individual dark flights of the main body along with two smaller fragments. For- tunately, 2 month after the superbolide, a 527-g meteorite was found. It was examined using several geochemical and petrographic analyses which allowed us to classify it as a moderately shocked (S3) L5 ordinary chondrite with a bulk density of 3.25 g cm −3 ., This paper was supported by the Xunta de Galicia (Spain) under the ED431B 2020/38 grant.

The XAS analysis of a blue-and-white Ming porcelain's decorations has been used to elucidate the porcelain's production technology. The porcelain exhibits the typical blue decorations with dark spots that are constituted by dendritic aggregates enriched in Mn and Fe. The XAS revealed that during firing Mn2+ and Fe2+ ions diffused into the glaze and started to crystallize at 900 °C as rhodonite and hausmannite-jacobsite intermediate compounds. The study of the Fe XAS pre-edges provided to be a powerful tool to assess the redox record from the porcelain. The natural basalt calibration determined the Fe3+/ƩFe × 100 in the glaze and confirmed the oxidizing conditions during its production. Hence, the obtained XAS helped to elucidate the temperatures at which the wares were produced by identifying the porcelain's pigments and the redox conditions during their production. This novel approach can also be applied on a broad range of modern and archaeological ceramics to elucidate their production technology.

In the Neolithic Gavà mines, variscite and turquoise were exploited for ornaments manufacturing, although some prospective pits and tunnels were dug on other similar greenish minerals such as smectite or kandite. A 3D study of the distribution of mineral phases allows us to determine the parameters involved in variscite colours. Methods are comprised of quantitative colourimetry, thin section petrography, SEM-BSE-EDS, EMPA, XRD, Raman spectroscopy, and57Fe Mössbauer spectrometry. Mapping of the mines indicates that colour is not directly dependent on depth. Although variscite from Gavà is poor in Cr3+ and V+3 compared with gemmy variscite from other localities, the deep green samples content has the highest values of Cr3+. In the case of cryptocrystalline mixtures with jarosite, phosphosiderite, or goethite, variscite tends to acquire a greenish brown to olivaceous hue. If white minerals such as quartz, kandite, crandallite, or alunite are involved in the mixtures, variscite and turquoise colours become paler., This paper has been granted by the projects 2014 SGR 1661, 2014/100820, 2017 SGR 995, and CLT009/1800044 of the Generalitat de Catalunya; by the project RYC2016-21108 of MCIN/AEI/10.13039/501100011033 and by “ESF Investing in your future” (EU).

The Hamutenha intrusion (Huíla province, SW Angola) is a 3-km-long elongated magmatic body defined by a set of two intrusive units. The northern unit is formed by alternating bands of dunites and olivine gabbros, while the southern unit is composed of amphibole diorites. The Hamutenha body is hosted by the Paleoproterozoic Epupa Complex in the Angolan Shield, SW margin of the Congo Craton. A mineralogical, petrological and geochemical study of the Hamutenha intrusion has been performed. The constrained compositional features of the parental melt suggest interaction of tholeiitic magmas with a significant enrichment in Fe and Ti. Although disseminated Fe–Ni–Cu-(Co) secondary sulphides are observed, both the crustal contamination parameters and generally low bulk-rock metals contents indicate that these elements were most likely previously extracted from the parental melt. U–Pb zircon dating of amphibole diorite samples from the southern unit yields a date of 1844 ± 14 Ma. These data suggest that the emplacement of these rocks was previous to the KC emplacement and it was probably related to the Paleoproterozoic Epupa Complex magmatism. This work has been supported by the project CGL2009-13758 of the Spanish Government and the projects SGR-444 and SGR-589 of the Catalan Government.

Large kaolin deposits developed by weathering on Precambrian granitic rocks have been discovered in the Caluquembe area, Huila province, Angola. To determine accuracy of analysis and to evaluate the kaolinite grade, a full-profile Rietveld refinement by X-ray Powder Diffraction (XRPD) and Thermal Gravimetric Analysis (TGA) was used. Caluquembe kaolin is composed mainly of kaolinite (44–93 wt.%), quartz (0–23 wt.%), and feldspar (4–14 wt.%). The Aparicio-Galan-Ferrell index (AGFI), calculated by XRPD profile refinement, indicates low- and medium-defect kaolinite. Kaolinite particles show a platy habit and they stack together forming ‘booklets’ or radial aggregates; they also occur as small anhedral particles in a finer-grained mass. Muscovite-kaolinite intergrowths have also been found. Whole-rock chemical analysis included major, trace, and Rare Earth Elements (REE). Chondrite-normalized REE patterns show the same tendency for all samples, with a significant enrichment in Light Rare Earth Elements (LREE). Mineralogical and compositional features of the Caluquembe kaolin indicate that it is a suitable material for the manufacture of structural products, such as bricks, paving stones, and roofing tiles. In addition, the significant REE contents of the Caluquembe kaolin can be considered as a potential future target of mining exploration.

Cobalt demand is increasing due to its key role in the transition to clean energies. Although the main Co ores are the sediment-hosted stratiform copper deposits of the Democratic Republic of the Congo, Co is also a by-product of Ni–Co laterite deposits, where Co extraction efficiency depends, among other factors, on the correct identification of Co-bearing minerals. In this paper, we reported a detailed study of the Co mineralisation in the Ni–Co laterite profiles of Loma Caribe (Dominican Republic) and Loma de Hierro (Venezuela). Cobalt is mainly associated with Mn-oxyhydroxide minerals, with a composition between Ni asbolane and lithiophorite, although a Co association with phyllosilicates has also been recorded in a Loma de Hierro deposit. In Loma Caribe, Co-bearing Mn-oxyhydroxide minerals mainly developed colloform aggregates, and globular to spherulitic grains, while in Loma de Hierro, they displayed banded colloform, fibrous or tabular textures. Most of the compositional analyses of Mn-oxyhydroxides yielded 20 and 40 wt.% Mn, with Ni and Co up to 16 and 10 wt.%, respectively. In both profiles, Mn-bearing minerals were mainly found in the transition from the oxide horizon to the saprolite, as observed in other laterite profiles in the world, where the precipitation of Mn-bearing minerals is enhanced because of the pore solution saturation and pH increase., This research was supported by grant PID2019-105625RB-C21 funded by MCIN/AEI/10.13039/501100011033 and by the Caribbean Lithosphere Reserve Group (http://caribbeanlithos.com/). IDAEA-CSIC is a Severo Ochoa Center of Research Excellence (Spanish Ministry of Science and Innovation, Project CEX2018-000794-S).

MAP2XANES is an intuitive Jupyter notebook that automatizes the analysis of synchrotron X-ray fluorescence imaging and X-ray absorption spectroscopy for the characterization of complex and heterogeneous samples. The notebook uses basic modules and functions from Numpy, Scipy, Pandas, iPywidgets and Matplotlib libraries for a powerful data reduction process that, in just a few clicks, guides the user through the visualization of elemental maps, space-resolved absorption spectra and their automatized analysis. In particular, by means of linear combination fit of the XANES spectra, the notebook determines the chemical species distribution in the sample under investigation. The direct output of the analysis process is the correlation between the different elemental distributions and the spatial localization of the chemical species detected. An application to mineralogy is thus presented, analyzing the Mn2+, Mn3+ and Mn4+ distribution in a mineral sample of hausmannite (Mn2+Mn2 3+O4), courtesy of the Museum of Natural Science of Barcelona.

The basement of eastern Mexico comprises Grenvillian-age granulite-facies metamorphic rocks. The Oaxacan Complex represents the largest outcrop belt of this basement in Mexico. In this work, southwestern Oaxacan Complex garnets are studied from a petrographical, geochemical, and geothermobarometrical perspective for the first time. The studied garnets display different grain sizes nucleated in a polyphase evolution. The almandine end member proportion is similar in all of the studied lithotypes. The highest pyrope concentrations are found in Qz Fsp paragenesis and ultramafic rocks and the lowest pyrope concentrations are found in amphibolite. The highest grossular and spessartine concentrations are found in the amphibolite lithotype. Southwestern Oaxacan Complex garnets from paraderivate samples are more enriched in Rb, Ba, Pb, Ni, and Zn than those from orthoderivate samples enriched in Ti and V. This fact is related to the nature of the protoliths and the mineral phases that fractionate the same minor and trace elements. Garnets from para-and orthoderivate samples display 0.02–1.1 Eu/Eu* anomalies. This fact indicates that almost all of the garnets formed while the plagioclase was stable, and it does not rule out the interpretation that some garnets were peritectic. The pressure obtained using a Grt-Opx-Pl-Qz geobarometer in the southwestern Oaxacan Complex is higher than the pressure obtained in the northern part of the Complex, and it is consistent with the pressure obtained in the Grenvillian-age granulites of the Novillo Gneiss from northeastern Mexico. Geothermobarometric studies reveal different P-T features at the study site, so different structural levels of the orogen are inferred. Published version This research was funded by CONACYT grant number 240226 and DGAPA-UNAM grant number IN111917.

One of the limiting factors for the analysis of minor elements in multiphase materials by electron probe microanalysis is the effect of secondary fluorescence (SF), which is not accounted for by matrix corrections. Although the apparent concentration due to SF can be calculated numerically or measured experimentally, detailed investigations of this effect for fine-grained materials are scarce. In this work, we use the Monte Carlo simulation program PENEPMA to examine and correct the effect of SF affecting micron-sized mineral inclusions hosted by other minerals. A concentration profile across an olivine [(Mg,Fe)2SiO4] inclusion in chromite (Fe2+Cr2O4) is measured and used to assess the reliability of calculations, where different boundary geometries are examined. Three application examples are presented, which include the determination of Cr in olivine and serpentine [Mg3Si2O5(OH)4] inclusions hosted by chromite and of Fe in quartz (SiO2) inclusions hosted by almandine garnet (Fe3Al2Si3O12). Our results show that neglecting SF leads to concentrations that are overestimated by ~0.1–0.8 wt%, depending on inclusion size. In addition, assuming a straight boundary yields to an underestimation of SF effects by a factor of ~2–4. Because its long-range nature, SF severely compromises trace element analyses even for phases as large as 1 mm in size.

On Christmas Day 1704, at 17 h (UT), a meteorite fell in Terrassa (about 25 km NW of Barcelona). The meteorite fall was seen and heard by many people over an area of several hundred kilometers and it was recorded in several historical sources. In fact, it was interpreted as a divine sign and used for propaganda purposes during the War of the Spanish Succession. Although it was believed that meteorite fragments were never preserved, here we discuss the recent discovery of two fragments (49.8 and 33.7 g) of the Barcelona meteorite in the Salvador Cabinet collection (Botanic Institute of Barcelona). They are very well preserved and partially covered by a fresh fusion crust, which suggests a prompt recovery, shortly after the fall. Analysis of the fragments has revealed that the Barcelona meteorite is an L6 ordinary chondrite. These fragments are among the oldest historical meteorites preserved in the world. On Christmas Day 1704, at 17 h (UT), a meteorite fell in Terrassa (about 25 km NW of Barcelona). The meteorite fall was seen and heard by many people over an area of several hundred kilometers and it was recorded in several historical sources. In fact, it was interpreted as a divine sign and used for propaganda purposes during the War of the Spanish Succession. Although it was believed that meteorite fragments were never preserved, here we discuss the recent discovery of two fragments (49.8 and 33.7 g) of the Barcelona meteorite in the Salvador Cabinet collection (Botanic Institute of Barcelona). They are very well preserved and partially covered by a fresh fusion crust, which suggests a prompt recovery, shortly after the fall. Analysis of the fragments has revealed that the Barcelona meteorite is an L6 ordinary chondrite. These fragments are among the oldest historical meteorites preserved in the world. On Christmas Day 1704, at 17 h (UT), a meteorite fell in Terrassa (about 25 km NW of Barcelona). The meteorite fall was seen and heard by many people over an area of several hundred kilometers and it was recorded in several historical sources. In fact, it was interpreted as a divine sign and used for propaganda purposes during the War of the Spanish Succession. Although it was believed that meteorite fragments were never preserved, here we discuss the recent discovery of two fragments (49.8 and 33.7 g) of the Barcelona meteorite in the Salvador Cabinet collection (Botanic Institute of Barcelona). They are very well preserved and partially covered by a fresh fusion crust, which suggests a prompt recovery, shortly after the fall. Analysis of the fragments has revealed that the Barcelona meteorite is an L6 ordinary chondrite. These fragments are among the oldest historical meteorites preserved in the world.

We present the description of a new species of Limoniidae Rondani, 1856. Trentepohlia (Paramongoma) miocenica Mederos & Wang n. sp. is described from resinites (little or poorly polymerized amber) of Yanigua Formation, in the Eastern District of Dominican Republic, well differentiated from the other species from the fossil record of Hispaniola to date, Trentepohlia (Paramongoma) agri Podenas & Poinar, 1999. A key to the five fossil species of the subgenus Paramongoma Brunetti, 1911 described to date is also offered. Since the biology of the immature stages of Paramongoma are associated with aquatic microhabitats (such as phytotelmata and small mountain streams), the occurrence of such microhabitats can therefore be hypothesized in the area then occupied by the Hispaniolan paleo-island. The records of extant species of the subgenus Paramongoma from several islands of the Lesser and Greater Antilles, as well as presence of the suitable ecological conditions, offers the possibility of finding living species of Trentepohlia Bigot, 1854 at Hispaniola, which is currently the only large island in the Caribbean without records of the genus. Nous présentons la description d’une nouvelle espèce de Limoniidae Rondani, 1856. Trentepohlia (Paramongoma) myocénique Mederos & Wang n. sp., décrite à partir d’une résinite (ambre peu ou mal polymérisée) de la formation de Yanigua, située dans le district oriental de la République dominicaine, bien différenciée de la seule espèce connue des archives fossiles d’Hispaniola, Trentepohlia (Paramongoma) agri Podenas et Poinar, 1999. Une clé séparant les cinq espèces fossiles du sous-genre Paramongoma Brunetti, 1911 décrites à ce jour est proposée. Comme la biologie des stades immatures de Paramongoma est associée à des microhabitats aquatiques (tels que les phytotelmata et des petits ruisseaux de montagne), on peut faire l’hypothèse que ces types de microhabitats étaient présents dans la zone alors occupée par la paléo-île d’Hispaniola. Les signalisations connues des espèces actuelles du sous-genre Paramongoma dans plusieurs îles des Petites et Grandes Antilles, ainsi que l’existence de conditions écologiques favorables, offrent la possibilité de trouver des espèces vivantes à Hispaniola, alors que cette île est la seule grande île de la Caraîbe sans mention du genre Trentepohlia Bigot, 1854.

The essential role of Critical Elements (CE) in 21st century economy has led to an increasing demand of these metals and promotes the exploration of non-conventional deposits such as weathering profiles. The present work is focused on the study of a weathering profile located at the Archaeological Park of the Gav&agrave, Neolithic Mines, Barcelona, Catalonia, Spain. In the Gav&agrave, deposit, acid and oxidising meteoric fluids generated intense weathering during the early Pleistocene, affecting series of Llandoverian black shales and associated syn-sedimentary phosphates. The circulation of these acid fluids at deeper levels of the profile generated supergene vein-like mineralisations comprised of secondary phosphates (e.g., variscite, perhamite, crandallite, phosphosiderite) and sulphates (e.g., jarosite, alunite). This supergene mineralisation is significantly enriched in certain CE (e.g., Ga, Sc, REE, In, Co and Sb) that were mobilised from host rock components and later hosted in the crystal lattice of supergene minerals. Weathering processes and corresponding supergene enrichment of CE at the Gav&agrave, deposit could be used as an example to determine exploration guidelines of CE in weathering profiles and associated supergene phosphates worldwide.

A volcanic dome complex of Miocene age hosts the In-bearing &Aacute, nimas&ndash, Chocaya&ndash, Siete Suyos district in SW Bolivia. Ore mineralization occurs as banded and massive infillings in sub-vertical, NE-SW striking veins. In this article, a detailed petrographic study is combined with in situ mineral geochemistry determinations in ore from the Arturo, Chorro and Diez veins in the Siete Suyos mine, the &Aacute, nimas, Burton, Colorada, and Rosario veins in the &Aacute, nimas mine and the Nueva vein in the Chocaya mine. A three-stage paragenetic sequence is roughly determined for all of them, and includes (1) an early low-sulfidation stage that is dominated by cassiterite, pyrrhotite, arsenopyrite, and high-Fe sphalerite (FeS &gt, 21 mol. %), (2) a second intermediate-sulfidation stage dominated by pyrite + marcasite &plusmn, intermediate product, sphalerite (FeS &lt, 21 mol. %), stannite, and local famatinite, and, (3) a late intermediate-sulfidation stage dominated by galena and Ag-Pb-Sn sulfosalts. Electron-probe microanalyses reveal high indium enrichment in stage-2 sphalerite (up to 9.66 wt.% In) and stannite (up to 4.11 wt.% In), and a moderate enrichment in rare wurtzite (up to 1.61 wt.% In), stage-1 sphalerite (0.35 wt.% In), cassiterite (up to 0.25 wt.% In2O3), and ramdohrite (up to 0.24 wt.% In). Therefore, the main indium mineralization in the district can be associated to the second, intermediate-sulfidation stage, chiefly in those veins in which sphalerite and stannite are more abundant. Atomic concentrations of In and Cu in sphalerite yield a positive correlation at Cu/In = 1 that agrees with a (Cu+ + In3+) 2Zn2+ coupled substitution. The availability of Cu in the mineralizing fluids during the crystallization of sphalerite is, in consequence, essential for the incorporation of indium in its crystal lattice and would control the distribution of indium enrichment at different scales. The highest concentrations of indium in sphalerite, which is found in the Diez vein in the Siete Suyos mine, occur in crustiform bands of sphalerite with local &ldquo, chalcopyrite disease&rdquo, texture, which has not been observed in the other studied veins. In stannite, the atomic concentrations of In are negatively correlated with those of Cu and Sn at Cu + In = 2 and Sn + In = 1. Thus, atomic proportions and correlations suggest the contextualization of the main indium mineralization in the sphalerite&ndash, stannite&ndash, roquesite pseudoternary system.

The tin-rich polymetallic epithermal deposit of Poop&oacute, 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 &ldquo, family&rdquo, 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 Poop&oacute, 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 l&ouml, llingite 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 &delta, 34SVCDT range in sulphides (&minus, 5.9 to &minus, 2.8&permil, ) 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 Poop&oacute, deposit, based on their abundance in the deposit and compositions, are rhodostannite, franckeite, cassiterite, stannite and, less importantly, teallite, sphalerite and jamesonite.

Gran Canaria is a hotspot-derived, intraplate, oceanic island, comprising a variety of alkaline felsic magmatic rocks (i.e. phonolites, trachytes, rhyolites and syenites). These rocks are enriched in rare-earth elements (REE) in relation to the mean concentration in the Earth's crust and they are subsequently mobilised and redistributed in the soil profile. From a set of 57 samples of felsic rocks and 12 samples from three paleosol profiles, we assess the concentration and mobility of REE. In the saprolite that developed over the rhyolites, we identified REE-bearing minerals such as primary monazite-(Ce), as well as secondary phases associated with the edaphic weathering, such as rhabdophane-(Ce) and LREE oxides. The averaged concentration of REE in the alkaline bedrock varies from trachytes (449 mg kg−1), to rhyolites (588 mg kg−1) and to phonolites (1036 mg kg−1). REE are slightly enriched in saprolites developed on trachyte (498 mg kg−1), rhyolite (601 mg kg−1) and phonolite (1171 mg kg−1) bedrocks. However, B-horizons of paleosols from trachytes and phonolites showed REE depletion (436 and 994 mg kg−1, respectively), whereas a marked enrichment was found in soils developed on rhyolites (1584 mg kg−1). According to our results, REE resources on Gran Canaria are significant, especially in Miocene alkaline felsic magmatic rocks (declining stage) and their associated paleosols. We estimate a total material volume of approximately 1000 km3 with REE concentrations of 672 ± 296 mg kg−1, yttrium contents of 57 ± 30 mg kg−1, and light and heavy REE ratios (LREE/HREE) of 17 ± 6. This mineralisation can be considered as bulk tonnage and low-grade ore REE deposits but it remains necessary to develop detailed mineral exploration on selected insular zones in the future, without undermining environmental and socioeconomic interests. REE exploration; REE-bearing minerals; Weathering processes; Ocean intraplate volcanic island; Gran Canaria

Chiva is a circular lagoon with a diameter of 900 m, located in the vicinity of the Catanda graben (Angola). This area is largely covered by Quaternary lacustrine sediments, however, a few dykes of carbonatiticcomposition have been found near the SE shore of the lagoon. The intrusion of these carbonatitic dykes has been linked to the occurrence of recent volcanic events in the Chiva area and interpreted as feeding channels of an eruptive centre with maar morphology. The Chiva carbonatitic dykes show a finely porphyritic texture formed by phenocrysts of subhedral calcite (60 %), apatite (30 %) and magnetite (10 %) hosted in a fine calcite-rich ground mass that also contains accessory minerals such as pyrochlore, perovskite and kimzeyite. The mineralogical and compositional features of the Chiva dykes are similar o those described in some of the carbonatitic lavas from the Catanda graben, suggesting that both volcanic events are genetically related. The finding of this new eruptive centre enlarges the carbonatitic domain of Catanda and opens the door to the discovery of new carbonatitic outcrops in this region of Western Angola. En las inmediaciones del graben de Catanda (Angola) se localiza una laguna circular de 900 metros de diámetro conocida como laguna de Chiva. Aunque éste área se encuentra mayoritariamente cubierta por sedimentos lacustres, hay afloramientos de un pequeño grupo de diques de composición carbonatítica en la orilla SE de la laguna. La intrusión de estos diques carbonatíticos se relaciona con el desarrollo de eventos volcánicos en la zona de Chiva y se interpreta como los antiguos canales de alimentación de un centro eruptivo que desarrolló una morfología de maar. Los diques carbonatíticos de Chiva presentan una típica textura porfídica formada por fenocristales subhedrales de calcita (60 %), apatito (30 %) y magnetita (10 %) implantados en una matriz de calcita de grano fino con cantidades accesorias de pirocloro, perovskita y kimzeyita. Las características mineralógicas y composicionales de los diques del maar de Chiva son equivalentes a las descritas en las lavas carbonatíticas del graben de Catanda, lo que sugiere que ambos procesos volcánicos están relacionados genéticamente. El hallazgo de este nuevo centro eruptivo amplía la zona de desarrollo del vulcanismo carbonatítico en Catanda y abre la puerta al posible descubrimiento de nuevos afloramientos carbonatíticos extrusivos en esta zona occidental de Angola.

The pyroclastic carbonatitic rocks from the Catanda volcanic area (Angola) contain annite and phlogopite grains which have been affected to a significant extent by vermiculitization. A mineralogical study of these micas has revealed that the annite was altered to K-vermiculite while vermiculitization of phlogopite generated Ca-vermiculite. Intermediate alteration products such as intergrowths of phlogopite/Ca-vermiculite were also found, but interstratified crystals of phlogopite/ vermiculite, a common intermediate product during vermiculitization processes, are not reported in the Catanda rocks. The two types of vermiculitized micas show ‘accordion’ textures, related to the expansion of vermiculite. To the authors’ knowledge, the present study is the first report of expanded vermiculites described in natural rocks and not generated as a consequence of industrial processing.

espanolEl Complejo Minero Neolitico de Gava (CMNG) ubicado en Cataluna tuvo como objeto la explotacion de la variscita verde utilizada para la elaboracion de adornos y joyeria. Los trabajos arqueologicos en mas de 100 minas indican que la minera en este complejo se llevo a cabo ~5800 anos antes del presente. CMNG constituye (A) uno de los primeros ejemplos conocidos de mineria subterranea en Europa, (B) posiblemente el ejemplo mas antiguo de mineria a gran escala para uso ornamental y (C) el ejemplo mas antiguo de aplicacion de conceptos geologicos y mineros complejos. En el CMNG, la variscita se encuentra en dos estilos distintos: (1) reemplazamientos de laminas delgadas de fluorapatito intercaladas con pizarras negras ricas en minerales organicos de edad silurica y (2) vetillas que cortan transversalmente estos materiales. El conjunto esta cubierto discordantemente y localmente por caliches del Cuaternario. La variscita se formo como resultado de procesos supergenicos cuaternarios que oxidaron la pirita produciendo soluciones acidas y oxidadas. Los fluidos resultantes movilizaron fosfato de apatito y lixiviaron Al y materia organica de las pizarras, lo cual condujo a la precipitacion de los fosfatos ricos en Al como rellenos de venas y de reemplazamientos estratoligados de apatito. La formacion de variscita se restringio a la extension del frente de oxidacion, y la variscita de ambos estilos de mineralizacion varia de color verde amarillento, en superficie, hasta verde profundo, en profundidad. El area de estudio contiene dos campos mineros: Can Tintorer y Can Badosa-Les Ferreres. La presencia de abundantes vetas subverticales de variscita en Can Tintorer permitio un complejo desarrollo de galerias en diferentes niveles de explotacion comunicadas por pozos y rampas, logrando 15 metros de profundidad. La explotacion empleada por los mineros neoliticos fue mediante realce ascendente y descendente; tambien usaron pilares y rellenos de explotaciones mas antiguas para evitar el colapso de la mina. Estas minas fueron abiertas en muchos casos por pozos que fueron cavados directamente en duros caliches cuaternarios, favoreciendo la estabilidad de las galerias y revelando que los mineros comprendian la continuidad de la mineralizacion por debajo de la cubierta de caliches. El mapeo geologico revela que las explotaciones en el area de Can Badosa-Les Ferreres son simples, mostrando una entrada unica a galerias simples o rampas que alcanzan menos de 5 m de profundidad y excavadas directamente en afloramientos de fosfatos. En contraste, las minas en el area de Can Tintorer tienen varias entradas y consisten en pozos verticales a traves de una cubierta cuaternaria, presentando una intrincada geometria con muchas galerias grandes y comunicadas a diferentes profundidades con un sistema de camaras y pilares. Aunque el desarrollo de ambas areas mineras fue esencialmente contemporaneo, Can Badosa-Les Ferreres puede considerarse como un area de exploracion. Ademas, la mineria se llevo a cabo en minerales adyacentes a la variscita, no directamente en las venas de variscita, lo cual indica que los mineros usaron de forma efectiva un caudal de conocimiento geologico que se adquirio previamente a las complejas operaciones en las minas de Can Tintorer. EnglishThe Gava Neolithic Mining Complex (GNMC) located in Catalonia was devoted to the exploitation of green variscite used in the crafting of ornaments. Archaeological works in more than 100 mines indicated that this mining activity was carried out ~5800 years before present. GNMC constitutes (1) one of the earliest known examples of underground mining in Europe, (2) the earliest example of large-scale mining for ornamental use, and (C) the earliest of the application of complex geological and mining concepts. In the GNMC variscite is found as two distinct styles: (1) replacement of thin fluorapatite beds, which are interbedded with pyritic organic-rich black shales of Silurian age; and (2) veinlets crosscutting these materials. This set of geological materials is unconformably covered locally by Quaternary calcretes. Variscite formed as a result of Quaternary supergene processes, which oxidized the pyrite and produced acidic, oxidized solutions. The resulting fluids mobilized phosphate from apatite and leached Al and organic matter out of Silurian shales, thus leading to the precipitation of the Al-rich phosphates as vein infillings and strata-bound replacements after apatite. The formation of variscite is restricted to the extent of the oxidizing front, and variscite of both mineralization styles changes in color from yellowish green near the surface to deep green in depth. The study area contains two mining fields: Can Tintorer and Can Badosa-Les Ferreres range. The presence of abundant subvertical variscite veins in Can Tintorer allowed a complex development of galleries at different exploitation levels communicated by shafts and ramps, achieving 15 meters depth. The exploitation by Neolithic miners was by overhand and underhand stoping; they also used pillars and refilling of older exploitations to avoid the mine collapsing. These mines were opened in many cases by shafts that were dug directly through hard Quaternary calcretes, favoring the galleries’ stability and revealing that miners understood that mineralization continues underneath the calcrete cover. Geological mapping reveals that exploitations in the Can Badosa-Les Ferreres area are simple, showing a single entrance to simple galleries or ramps attaining less than 5 m in depth and directly excavated on phosphate outcrops. Contrastingly, the mines in the Can Tintorer area have several entrances that consist of vertical shafts through a Quaternary cover, presenting an intricate geometry with many large and communicated galleries at different depths with a system of cameras and pillars. Although the development of both mining areas was essentially contemporaneous, the Can Badosa-Les Ferreres area can only be considered an exploration area. In addition, mining was carried out on minerals adjacent to variscite, not directly on variscite veins themselves, thus indicating that the miners were effectively using a wealth of geological knowledge that was previously acquired in the complex operations in the Can Tintorer mines.

The Eureka deposit in Castell-esta&oacute, in the Catalan Pyrenees is a Cu&ndash, U&ndash, V deposit, hosted by Triassic red-bed sandstones, and classified here as a low-temperature, sandstone-hosted stratabound metamorphite U deposit. The main mineralisation is stratabound, related to coal-bearing units and produced during the Alpine deformation by migration of hydrothermal fluids. In this stage, the original sedimentary and diagenetic components (quartz and calcite, micas, hematite and locally apatite) were replaced by a complex sequence of roscoelite, fine-grained REE phosphates, sulphides and Ni&ndash, Co arsenides and sulpharsenides, Ag&ndash, Pb selenides, bismuth phases, sulphosalts and uraninite. The black shales of the Silurian sediments underlying the deposit and the nearby Carboniferous volcanoclastic rocks are interpreted as the source of the redox-sensitive elements concentrated in Eureka. The sulphur source is related to leaching of the evaporitic Keuper facies. The REE transport would be facilitated by SO4-rich solutions. The reduction of these solutions by interaction with organic matter resulted in the widespread precipitation of REE and redox-sensitive elements, including many critical metals (V, Bi, Sb, Co), whereas barite precipitated in the oxidized domains. The occurrence of similar enrichments in critical elements can be expected in other similar large uranium deposits, which could be a source of these elements as by-products.

espanolLa mineria de los recursos de hierro del area de Gava (Cataluna) fue activa de forma intermitente durante las epocas Iberica y Romana, la Edad Media, y hasta la era industrial, lo cual se ha probado mediante datos arqueologicos y documentos historicos. Es posible que, inclusive, la mineria de hierro en el area haya existido durante el periodo Neolitico. Las mineralizaciones de hierro se formaron en dos estadios: (1) alteracion hidrotermal regional asociada a cabalgamientos Hercinicos que produjo ankeritizaciones de calizas en las series del Paleozoico, y (2) el reemplazamiento karstico de los carbonatos ricos en hierro durante el Plioceno y el Cuaternario por medio de fluidos supergenicos que produjeron ocres con goethita y hematites. El estilo de mineralizacion depende en gran medida de las caracteristicas del protolito reemplazado, lo cual lleva a la definicion de tres estilos de mineralizacion: (1) El reemplazamiento supergenico de calizas masivas ankeritizadas del Pridoliense produjo unicamente reemplazamientos locales restringidos a discontinuidades estructurales o estratigraficas por lo tanto, las mineralizaciones son de dimensiones reducidas en forma de vetillas o masas verticales irregulares; (2) El reemplazamiento de alternancias de calizas ankeritizadas con pizarras que contienen pirita diseminada (Lockoviense) produjo bolsadas de mineralizaciones masivas ricas en silice derivadas de las pizarras alteradas; (3) El reemplazamiento de carbonatos cabalgados por pizarras ricas en sulfuros y fosfatos favorecio la formacion de mineralizaciones estratoligadas masivas, que son las de mayor tamano y grado en el area de estudio, pudiendo estar localmente enriquecidas en minerales del supergrupo de la alunita y en fosfatos de Ca y Fe. Afloramientos de todos estos estilos de mineralizacion fueron explotadas tanto en la antiguedad como en la Edad Media, aprovechando la alta calidad metalurgica de las menas, pese a que los dos primeros estilos de mineralizacion presentan cuerpos de reducido tamano. Por ello, en dichas epocas la explotacion fue artesanal mediante trincheras o pocillos. En cambio, en la epoca industrial solo se beneficiaron los recursos masivos del tercer estilo de mineralizacion a cielo abierto y a traves de galerias. EnglishMining for iron resources in the Gava area of Catalonia occurred intermittently during the Iberian and Roman epochs, the Middle Ages, and continuing until the industrial era, as evidenced by historical and archaeological documents.. Iron mining in this area could have occurred even earlier, during the Neolithic period. Iron ores were formed in two stages: (1) a regional hydrothermal alteration associated with Hercynian thrusts that produced the ankeritization of limestones within the Paleozoic series, and (2) the karstic replacement of these iron-rich carbonates during the Pliocene and Quaternary by means of supergenic fluids that produced ochres with goethite and hematite. The style of mineralization largely depends on the characteristics of the replaced protolith, and three styles of mineralization can be defined: (1)The supergenic replacement of ankeritized massive Pridolian limestones only produced local replacements that were restricted to structural or stratigraphic discontinuities, therefore, the mineralization has reduced dimensions and occurs as irregular veinlets or pipes; (2) The replacement of interbedded ankeritized limestones and pyrite-bearing shales (Lockovian) produced massive ores in pod-shaped bodies rich in silica impurities derived from the altered shales; and (3) The replacement of carbonates overthrust by pyrite- and phosphate-rich shales favored the formation of massive stratabound deposits, which are the largest and highest grade deposits in the study area, and may be locally enriched in minerals of the alunite supergroup and Ca- and Fe-rich phosphates. Outcrops of all of these styles of mineralization were mined by the Iberian cultures, during the roman period and in the Middle Ages, taking advantage of the relatively high metallurgical quality of the ores.Therefore, the exploitation during these epochs was artisanal by means of trenches or small pits. In contrast, during the industrial era only the massive stratabound deposits were exploited in open pits and underground galleries.

The polymetallic Huanuni deposit, a world-class tin deposit, is part of the Bolivian tin belt. As a likely case for a &ldquo, mesothermal&rdquo, or transitional deposit between epithermal and porphyry Sn types (or shallow porphyry Sn), it represents a case that contributes significantly to the systematic study of the distribution of critical elements within the &ldquo, family&rdquo, of Bolivian tin deposits. In addition to Sn, Zn and Ag, further economic interest in the area resides in its potential in critical elements such as In, Ga and Ge. This paper provides the first systematic characterisation of the complex mineralogy and mineral chemistry of the Huanuni deposit with the twofold aim of identifying the mineral carriers of critical elements and endeavouring plausible metallogenic processes for the formation of this deposit, by means of a multi-methodological approach. With In concentrations consistently over 2000 ppm, the highest potential for relevant concentrations in this metal resides in widespread tin minerals (cassiterite and stannite) and sphalerite. Hypogene alteration assemblages are hardly developed due to the metasedimentary nature of host rocks, but the occurrence of potassium feldspar, schorl, pyrophyllite and dickite as vein material stand for potassic to phyllic or advanced argillic alteration assemblages and relatively high-temperature (and low pH) mineralising fluids. District-scale mineralogical zonation suggests a thermal zonation with decreasing temperatures from the central to the peripheral areas. A district-scale zonation has been also determined for &delta, 34SVCDT values, which range &minus, 7.2&permil, to 0.2&permil, (mostly &minus, 7&permil, to &minus, 5&permil, ) in the central area and &minus, 4.2&permil, to 1.0&permil, (mainly constrained between &minus, 2&permil, and 1&permil, ) in peripheral areas. Such values stand for magmatic and metasedimentary sources for sulfur, and their spatial zoning may be related to differential reactivity between mineralising fluids and host rocks, outwardly decreasing from the central to the peripheral areas.

The Kunene Intrusive Complex (KIC), in NW Namibia and SW Angola, is one of the largest Proterozoic anorthosite massif-type exposures in the world. A geochemical, mineralogical and petrological study of four Fe–Ti(–V) oxide bodies located in the understudied Angolan part of the KIC has been performed. The massive Fe–Ti(–V) oxide bodies, locally apatite-rich (nelsonites), are lenticular or dike-like. They consist mostly of titaniferous magnetite, ilmenite and minor aluminous spinel, apatite, olivine and graphite. Titaniferous magnetite displays a wide variety of subsolvus features, including aluminous spinel–magnetite–ulvöspinel exsolutions and ilmenite (Trellis) exsolutions. This work estimated the composition of the titaniferous magnetite prior to the exsolution, in order to calculate the temperature and oxygen fugacity of the different lithologies of each ore body. The thermo-oxybarometry results obtained range from 600 ºC to 820 º C and ƒO2 from 10-24.7 to 10-14.7. These values do not correspond to magmatic crystallization in equilibrium, but to a later re-equilibration. In addition, the mineralogical and geochemical results indicate that the studied ore bodies contain economic reserves of Ti, V, and possibly of P and REE.

The origin of intraplate carbonatitic to alkaline volcanism in Africa is controversial. A tectonic control, i.e., decompression melting associated with far-field stress, is suggested by correlation with lithospheric sutures, repeated magmatic cycles in the same areas over several million years, synchronicity across the plate, and lack of clear age progression patterns. Conversely, a dominant role for mantle convection is supported by the coincidence of Cenozoic volcanism with regions of lithospheric uplift, positive free-air gravity anomalies, and slow seismic velocities. To improve constraints on the genesis of African volcanism, here we report the first radiometric and isotopic results for the Catanda complex, which hosts the only extrusive carbonatites in Angola. Apatite (U-Th-Sm)/He and phlogopite 40Ar/39Ar ages of Catanda aillikite lavas indicate eruption at ca. 500-800 ka, more than 100 m.y. after emplacement of abundant kimberlites and carbonatites in this region. The lavas share similar high-μ (HIMU)-like Sr-Nd-Pb-Hf isotope compositions with other young mantle-derived volcanics from Africa (e.g., Northern Kenya Rift; Cameroon Line). The position of the Catanda complex in the Lucapa corridor, a long-lived extensional structure, suggests a possible tectonic control for the volcanism. The complex is also located on the Bié Dome, a broad region of fast Pleistocene uplift attributed to mantle upwelling. Seismic tomography models indicate convection of deep hot material beneath regions of active volcanism in Africa, including a large area encompassing Angola and northern Namibia. This is strong evidence that intraplate late Cenozoic volcanism, including the Catanda complex, resulted from the interplay between mantle convection and preexisting lithospheric heterogeneities.

Las carbonatitas volcánicas de Catanda son las únicas descritas hasta el momento de carácter extrusivo en Angola. Esta localidad es, además, significativamente interesante por la presencia de lavas carbonatíticas, las cuales se han descrito en tan solo 14 lugares a nivel mundial. Sin embargo, la información publicada referente a Catanda se reducía, hasta ahora, a unos pocos trabajos elaborados por investigadores portugueses en la década de los años 1960 y 1970, en los cuales se aportaban datos sobre geología regional y se describían características de las carbonatitas, aunque estos resultados eran muy limitados. La falta de información geológica que hasta ahora había sobre la zona de estudio se debe, principalmente, a la inestabilidad política y social reinante en Angola por los conflictos bélicos que asolaron su territorio durante más de cuarenta años y que imposibilitaron el acceso y el estudio de la región de Catanda, así como de otras muchas áreas en el conjunto del país. Bajo este contexto general se planteó el presente proyecto de tesis doctoral, con el objetivo de aportar nueva información y conocimientos referentes al vulcanismo carbonatítico de la región de Catanda y, en particular, a las características litológicas, mineralógicas, petrológicas, geoquímicas, petrogenéticas y de emplazamiento de las carbonatitas volcánicas. A partir de las observaciones realizadas se ha podido constatar que las carbonatitas de Catanda están formadas por un conjunto de hasta siete edificios volcánicos con morfologías de anillos de tobas y maares que afloran en un graben de unos 50 km2 de extensión. Además, asociado a este conjunto principal, se ha descrito un octavo centro eruptivo, con morfología de maar, localizado a unos cinco kilómetros al este del graben de Catanda, en la zona conocida como laguna de Chiva. Los afloramientos de rocas piroclásticas y lávicas de la región forman series de materiales vulcano-sedimentarios que alcanzan 100 metros de potencia, hallándose dispuestos sobre un basamento de granitos de edad Arcaica que, a su vez, se encuentran recubiertos por sedimentos aluviales y coluviales de edad reciente. Se ha podido determinar que las carbonatitas de Catanda se formaron a partir de procesos volcánicos eminentemente explosivos y que la actividad efusiva que dio lugar a las lavas carbonatíticas fue escasa y está concentrada en las zonas externas del graben, asociadas a importantes fracturas regionales. El estudio petrográfico de las rocas de Catanda ha permitido diferenciar hasta cinco facies distintas de rocas piroclásticas y tres tipologías distintas de lavas carbonatíticas. Estas lavas pueden clasificarse como calciocarbonatitas (con un contenido de calcita superior al 70% modal), aillikitas (con contenidos de calcita inferiores al 35% y 5102 por encima del 14 % en peso) y natrocarbonatitas alteradas (formadas por cristales tabulares de calcita pseudomórficos de carbonatos alcalinos). La caracterización geoquímica de las lavas ha permitido constatar que a pesar de sus diferencias texturales y composicionales, todas ellas se formaron a partir de un mismo magma parental carbonatítico que, tras el estudio de las inclusiones fundidas incluidas en magnetita, se ha podido determinar que tenía una composición eminentemente alcalina. Los estudios realizados en Catanda por Silva y Pereira (1973) afirmaban que las carbonatitas de la región se formaron en el Cretácico superior (92 Ma), dato que obtuvieron a partir de la datación de un dique de rocas alcalinas (tinguaíta) que consideraron contemporáneo con las carbonatitas. Sin embargo, durante la realización del presente proyecto de tesis, se han llevado a cabo dataciones de minerales presentes en las carbonatitas de Catanda, utilizando los métodos de Rb/Sr en flogopita y U-Th-He en apatito. La edad obtenida ha sido de 0,65-0,66 Ma (Pleistoceno medio), variando sustancialmente la edad establecida en primera instancia por esos autores y obligando a replantear el contexto geodinámico y volcanológico del graben de Catanda y, en general, del margen Atlántico de Angola., The volcanic carbonatitic region of Catanda is the only extrusive carbonatite locality reported in Angola. The Catanda area is also significant due to the occurrence of carbonatitic lavas; those have been only reported in 14 localities worldwide. However, the available information about these carbonatites was restricted to a few works developed in the 60's and the 70's, in which the reported data about the geological setting and main features of the carbonatites were strongly limited. The information gap about Catanda was especially generated by the politic and social instability caused by the Angolan civil war, which made impossible the access to the Catanda region and entire Angola, for more than forty years. According to this general approach, the aim of the present Ph.D. project was to obtain new information and knowledge about the carbonatitic volcanism of the Catanda region and, especially, in relation to its lithological features, mineralogy, petrology geochemistry, genetic and emplacement processes related to the formation of the extrusive carbonatites. Coupled analyses of satellital images and field data demonstrated thatCatanda carbonatites are formed by a group of seven small volcanic edifices with maar and tuff ring morphologies, outcropping in a graben of 50 km2 in extension. In addition, we also discovered and maar at 5 km east from the main volcanic area, in the region known as Chiva lagoon. The pyroclastic rocks from the Catanda region may achieve up to 100 metres in thickness deposited over Archaean granites and broadly covered by recent alluvial and colluvial sediments. We have determined that Catanda carbonatites were especially formed by explosive events, while carbonatitic lavas were very minor and restricted to the external parts of the graben, associated to the most important fractures. The petrographic study of the Catanda rocks allowed us to distinguish 5 different facies of pyroclastic rocks and 3 typologies of carbonatitic lavas. These lavas can be classified as calciocarbonatites (containing more than 70% of modal calcite), silicocarbonatites-aillikites (with less than 35% of modal calcite and more than 14 wt.% of SiO2) and altered natrocarbonatites (formed by tabular calcite crystals pseudomorphs of primary alkaline carbonates). Geochemical data also permits to confirm that, even their compositional and textural differences, all Catanda lavas were formed from the same parental melt. The study of melt inclusions hosted in magnetite grains also indicates that the parental melt composition was broadly alkaline. The studies carried in Catanda by Silva & Pereira (1973) argued for the late Cretaceous age of the carbonatites (92 Ma). This age was obtained from the dating of a tinguaite dyke that the authors considered contemporaneous to the carbonatitic rocks. However, in the present Ph.D. project we carried out the first direct dating of the Catanda lavas, using Rb/Sr and U-Th-He methods in fluorapatite and phlogopite, respectively. The age obtained from these dating has been approximately 0.65-0.66 Ma. This new dating changes the general view of the volcanic and geodynamic setting of the Catanda graben and, in general, the entire Angolan Atlantic margin.

Carbonatite lavas and pyroclastic rocks are exposed in the volcanic graben of Catanda and represent the only known example of extrusive carbonatites in Angola. A new detailed geological map of the area is presented in this study as well as six different stratigraphic sections. Pyroclastic rocks, apparently unwelded, are dominant in the area and represented in all the stratigraphic columns. They form shallowly to moderately inclined layers, mostly devoid of internal structures, that range in thickness from several centimetres to metres. They are dominantly lapilli tuffs and minor tuffs occasionally comprising pelletal lapilli. Based on their different features and field relationships, at least five different pyroclastic lithofacies have been distinguished in the area. Carbonatitic lavas outcrop in the external parts of the Catanda graben, forming coherent layers interbedded with pyroclastic rocks. Calcite is the most common mineral in the lavas, but other accessory minerals such as fluorapatite, titaniferous magnetite, phlogopite, pyrochlore, baddeleyite, monticellite, perovskite, cuspidine and periclase have also been identified. At least four different types of lavas have been distinguished based on their mineral associations and textural features. This study reveals an overall abundance of pyroclastic material in comparison to lava flows in the Catanda area, suggesting that eruptive processes were dominated by explosive activity similar to what has been described in other carbonatite and kimberlite localities. The Catanda carbonatitic volcanism was associated with monogenetic volcanic edifices with tuff ring or maar morphologies, and at least seven possible eruptive centres have been identified in the area.

El coleccionismo de minerales es una actividad en expansión. El alto nivel de demanda de minerales y de sus derivados posibilita la creación de microempresas en países en vías de desarrollo que, con muy poca inversión de capital, pueden facilitar el desarrollo de áreas rurales sin producir apenas impacto en el medio natural. Un aspecto muy importante para la supervivencia de estas microempresas es que el material tenga la calidad adecuada para su óptima comercialización, cosa que no ocurre en la actualidad con la mayor parte del material que procede de los países en vías de desarrollo. En este trabajo se proporcionan, de forma ilustrada, los criterios que se deben usar para identificar el tipo de material que puede ser interesante para ser comercializado, así como los mecanismos de tratamiento de los minerales desde su lugar de extracción hasta el punto de venta. Mineral collecting is a growing activity. The high demand for minerals and their derivatives has resulted in the creation of microcompanies around the mineral trade in developing countries. This activity could facilitate the development of rural areas with no need of a large capital investment and with minimal environmental impact. The high quality of their products is the most important aspect for the survival of these micro-companies, but nowadays the material that comes from developing countries does not always arrive in the best condition. In this essay the basic criteria are provided for identifying the kind of minerals that are interesting enough to be commercialized, and also the procedures recommended for commercializing them from the place where they are extracted to their point of sale.

The Virulundo carbonatite in Angola is one of the largest in the world and contains pyrochlore as an accessory mineral in all of the carbonatite units (calciocarbonatites, ferrocarbonatites, carbonatite breccias and trachytoids). The primary magmatic pyrochlore is fluorine dominant and typically contains about equal molar quantities of Ca and Na at the A site. High-temperature hydrothermal processes have resulted in the pseudomorphic replacement of the primary pyrochlore by a second generation of pyrochlore with less F and Na. Low-temperature hydrothermal replacement of the first and second generation pyrochlore, associated with quartz-carbonate-fluorite vein formation in the carbonatite, has produced a third generation of pyrochlore, with a high Sr content. The Sr appears to have been released by low-temperature hydrothermal replacement of the primary magmatic carbonates. Finally, supergene alteration processes have produced late-stage carbonates, goethite, hollandite and rare earth element (REE) minerals (mainly synchysite-(Ce), britholite-(Ce), britholite-(La), cerite-(Ce)). Cerium separated from the other REE s in oxidizing conditions and Ce4+ was incorporated into a late generation of supergene pyrochlore, which is strongly enriched in Ba and strongly depleted in Ca and Na.

A set of small volcanic edifices with tuff ring and maar morphologies occur in the Catanda area, which is the only locality with extrusive carbonatites reported in Angola. Four outcrops of carbonatite lavas have been identified in this region and considering the mineralogical, textural and compositional features, we classify them as: silicocarbonatites (1), calciocarbonatites (2) and secondary calciocarbonatites produced by the alteration of primary natrocarbonatites (3). Even with their differences, we interpret these lava types as having been a single carbonatite suite related to the same parental magma. We have also estimated the composition of the parental magma from a study of melt inclusions hosted in magnetite microphenocrysts from all of these lavas. Melt inclusions revealed the presence of 13 different alkali-rich phases (e.g., nyerereite, shortite, halite and sylvite) that argues for an alkaline composition of the Catanda parental melts. Mineralogical, textural, compositional and isotopic features of some Catanda lavas are also similar to those described in altered natrocarbonatite localities worldwide such as Tinderet or Kerimasi, leading to our conclusion that the formation of some Catanda calciocarbonatite lavas was related to the occurrence of natrocarbonatite volcanism in this area. On the other hand, silicocarbonatite lavas, which are enriched in periclase, present very different mineralogical, compositional and isotopic features in comparison to the rest of Catanda lavas. We conclude that its formation was probably related to the decarbonation of primary dolomite bearing carbonatites.