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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.

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 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 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

A representative sampling of carbonatites, alkaline felsic igneous rocks and corresponding paleosols was carried out on Gran Canaria and Fuerteventura (Canary Islands, Spain) in order to assess the geochemical composition, focussing on Rare-Earth Elements (REE). Thus, we analysed 70 samples of plutonic, subvolcanic and volcanic rocks from the Miocene declining and Pliocene rejuvenation volcanic stages, and associated soils (B-C horizons) on Gran Canaria. In addition, 40 samples from the Oligocene-early Miocene submarine magmatic stage composed by syenites, nepheline-syenites and carbonatites (veins, dykes and stocks), as well as from the Miocene alkaline declining stage with trachytes and quartztrachytes (domes) have been studied on Fuerteventura. The maximum REE contents (mg/kg) for Gran Canaria are in the Miocene syenites (474-590), trachytes (588-601), phonolites (828-1036) and rhyolites (446-577), whereas lower values are found in Pliocene trachytic lavas (446) and phonolitic domes (333-577). REE enriched C-B horizons range from 429 to 1,584 mg/kg. In Fuerteventura, REE contents in Oligoceneearly Miocene syenites range between 51 and 1,761 mg/kg; from 697 and 7,372 in carbonatites and from 90 to 394 in Miocene trachytes. According to our results, LREE are one order of magnitude higher than HREE, and REE resources from Gran Canaria are significant in Miocene felsic igneous rocks and their paleosols, while early-Miocene carbonatites are the best REE exploration target in Fuerteventura.

The polymetallic Huanuni deposit, a world-class tin deposit, is part of the Bolivian tin belt. As a likely case for a “mesothermal” 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 “family” 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 δ34SVCDT values, which range −7.2‰ to 0.2‰ (mostly −7‰ to −5‰) in the central area and −4.2‰ to 1.0‰ (mainly constrained between −2‰ and 1‰) 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. Keywords: critical elements; indium; gallium; germanium; tin; silver; cerium; hydrothermal; bolivian tin belt The polymetallic Huanuni deposit, a world-class tin deposit, is part of the Bolivian tin belt. As a likely case for a “mesothermal” 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 “family” 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 δ34SVCDT values, which range −7.2‰ to 0.2‰ (mostly −7‰ to −5‰) in the central area and −4.2‰ to 1.0‰ (mainly constrained between −2‰ and 1‰) 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. Keywords: critical elements; indium; gallium; germanium; tin; silver; cerium; hydrothermal; bolivian tin belt The polymetallic Huanuni deposit, a world-class tin deposit, is part of the Bolivian tin belt. As a likely case for a “mesothermal” 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 “family” 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 δ34SVCDT values, which range −7.2‰ to 0.2‰ (mostly −7‰ to −5‰) in the central area and −4.2‰ to 1.0‰ (mainly constrained between −2‰ and 1‰) 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. Keywords: critical elements; indium; gallium; germanium; tin; silver; cerium; hydrothermal; bolivian tin belt

Large kaolin deposits developed by weathering on Precambrian granitic rocks have been discovered in the Caluquembe area, Huíla province, Angola. To determine accuracy of analysis and to evaluate the samples kaolinite grade, it was used full profile Rietveld refinement by X-­‐Ray Powder Diffraction (XRPD) and Gravimetric Thermal Analysis (TGA). Caluquembe kaolin is mainly comprised of kaolinite (44 to 93 wt.%), quartz (0 to 23 wt.%) and feldspar (4 to 14 wt. %). AGFI Crystallinity Index, calculated by XRPD profile refinement, indicates low and medium defect kaolinite. Kaolinite particles show a platy habit and they are stacked together forming ‘booklets’ or radial aggregates, also occurring as fine anhedral particles in a finer-­‐grained mass. Muscovite-­‐kaolinite intergrowths have also been found. Whole-­‐rock chemical composition was analyzed, including major, trace, and Rare Earth Elements (REE). Chondrite and Upper Continental Crust 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 in the manufacture of structural products, such as bricks, pavers and roofing tiles. In addition, REE significant contents of the Caluquembe kaolin can be considered as a potential future target of mining exploration. Caluquembe; Angola; kaolinite; AGFI; REE. Large kaolin deposits developed by weathering on Precambrian granitic rocks have been discovered in the Caluquembe area, Huíla province, Angola. To determine accuracy of analysis and to evaluate the samples kaolinite grade, it was used full profile Rietveld refinement by X-­‐Ray Powder Diffraction (XRPD) and Gravimetric Thermal Analysis (TGA). Caluquembe kaolin is mainly comprised of kaolinite (44 to 93 wt.%), quartz (0 to 23 wt.%) and feldspar (4 to 14 wt. %). AGFI Crystallinity Index, calculated by XRPD profile refinement, indicates low and medium defect kaolinite. Kaolinite particles show a platy habit and they are stacked together forming ‘booklets’ or radial aggregates, also occurring as fine anhedral particles in a finer-­‐grained mass. Muscovite-­‐kaolinite intergrowths have also been found. Whole-­‐rock chemical composition was analyzed, including major, trace, and Rare Earth Elements (REE). Chondrite and Upper Continental Crust 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 in the manufacture of structural products, such as bricks, pavers and roofing tiles. In addition, REE significant contents of the Caluquembe kaolin can be considered as a potential future target of mining exploration. Caluquembe; Angola; kaolinite; AGFI; REE. Large kaolin deposits developed by weathering on Precambrian granitic rocks have been discovered in the Caluquembe area, Huíla province, Angola. To determine accuracy of analysis and to evaluate the samples kaolinite grade, it was used full profile Rietveld refinement by X-­‐Ray Powder Diffraction (XRPD) and Gravimetric Thermal Analysis (TGA). Caluquembe kaolin is mainly comprised of kaolinite (44 to 93 wt.%), quartz (0 to 23 wt.%) and feldspar (4 to 14 wt. %). AGFI Crystallinity Index, calculated by XRPD profile refinement, indicates low and medium defect kaolinite. Kaolinite particles show a platy habit and they are stacked together forming ‘booklets’ or radial aggregates, also occurring as fine anhedral particles in a finer-­‐grained mass. Muscovite-­‐kaolinite intergrowths have also been found. Whole-­‐rock chemical composition was analyzed, including major, trace, and Rare Earth Elements (REE). Chondrite and Upper Continental Crust 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 in the manufacture of structural products, such as bricks, pavers and roofing tiles. In addition, REE significant contents of the Caluquembe kaolin can be considered as a potential future target of mining exploration. Caluquembe; Angola; kaolinite; AGFI; REE.

Kaolin deposits has been for long exploited in several regions of Angola, and some of the most important are produced by weathering of anorthositic rocks from the Cunene complex. However, a systematic research has not been carried out until the present mo Kaolin deposits has been for long exploited in several regions of Angola, and some of the most important are produced by weathering of anorthositic rocks from the Cunene complex. However, a systematic research has not been carried out until the present mo Kaolin deposits has been for long exploited in several regions of Angola, and some of the most important are produced by weathering of anorthositic rocks from the Cunene complex. However, a systematic research has not been carried out until the present mo

Kaolin deposits has been for long exploited in several regions of Angola, and some of the most important are produced by weathering of anorthositic rocks from the Cunene complex. However, a systematic research has not been carried out until the present moment. Some extensive outcrops of kaolinitic weathering proiles developed on Precambrian granitic rocks were discovered during a recent trip in the Caluquembe area, in the Huila province (SSE of Luanda). The present study determined the mineralogical features and thermal properties of the clay minerals fromthese outcrops. The mineral composition was determined by means of X-ray diffraction, Raman spectroscopy and scanning electron microscopy. The quantitative mineral phase analyses of the samples were obtained by X-ray diffraction proile reinement using Topas V2.2. The thermal behaviour was studied by differential thermal and thermogravimetric analysis. Whole-rock geochemical analyses on random powders (XRPD) reveal that samples are mainly composed of kaolinite, quartz, feldspars (e.g. albite and microcline) and muscovite. In addition, smectite and hematite have been detected only in some samples. The obtained results indicate that samples present high kaolinite contents (~85 wt%), although a few samples which contain smectite have lower percentages of kaolinite (~28% wt%). Thermal analyses were carried out to check the quantitative results of mineral phasesby XRPD. The differential thermal analysis (DTA) curve showsonly an endothermic peak at about 540 °C in dry air which conirms the dehydration of kaolinite [1] in samples lacking smectite. Mass loss in the samples, measured by thermogravimetric analysis (TG), is between 4 to 11 wt% until 650 ºC; samples with higher kaolinitecontents show the highest mass loss values. The amount of kaolinite calculated by mass loss is between 90 and 25 wt%. We can conclude that XRPD and TG results have a good correlation and the combination of both techniques is suitable to determine the kaolinite content in this kind of clay deposits. Based on the high content of kaolinitefrom the deposit of Caluquembe, this area is very suitable for the exploration and potential exploitation of kaolinite, which is a very valuable raw material demanded in the fabrication of ceramics, cosmetics, paper or pharmaceutical products.

En este trabajo se presentan los resultados de la caracterización mineralógica de las esmectitas representativas de la zona saprolítica y esmectítica del perfil de San Felipe mediante análisis de Difracción de rayos X (DRX) tanto de muestras en polvo como de agregados orientados (AO, AO+EG, AO+550ºC) y Microscopia Electrónica de Barrido (SEM-EDS) y de Transmisión (TEM-AEM).

Large-scale gas seepage and fluid ejection features are described from the edges of the active pull-apart Wagner and Consag basins (northern Gulf of California, Mexico), at water depths between 65 and 150 m. Gas vents, pockmarks, possible mud volcanoes, pyrite- and barite-rich sediments, slabs of lithified shell debris, and chemosynthetic fauna were found. Gas venting occurs mainly through N-S synsedimentary small-scale faults and fault-propagation folds that are believed to derive from the Wagner Fault. The presumed mud volcanoes are sub-rounded, domed bathymetric features, several hundreds of metres across, underlain by gas-charged sediments and surrounded by gas vents. Upward gas migration throughout the thick sedimentary sequence produces the fluid expulsion features on the sea floor.

Català: Aquest treball neix amb la intenció d’afegir un granet de sorra a un projecte d’investigació sobre la degradació de talussos de carretera situats en dos municipis del País Basc dut a terme per Joan Martínez-Bofill en col·laboració amb el Departament de Cristal·lografia i Mineralogia de la Universitat de Barcelona, el Departament d’Enginyeria del Terreny de la Universitat Politècnica de Catalunya i la Diputació Foral de Gipúzkoa. L’aportació fonamental al projecte és bàsicament la realització d’un estudi amb detall de la microtextura i la mineralogia de mostres extretes de sondeigs a peu de talús per mirar d’aprofundir en les causes de les patologies de degradabilitat que presenten els materials aflorants. Per fer-ho s’ha plantejat l’ús de la microscòpia electrònica d’escombrat (BSESEM/EDS) amb anàlisi d’energies dispersives i s’ha intentat justificar l’ús d’aquesta tecnologia en projectes d’aquest tipus, per a adquirir un grau de coneixement del terreny més profund i detallat del que permet la tradicional microscòpia òptica. Els resultats obtinguts d’aquestes anàlisis microtexturals s’han correlacionat amb els resultats obtinguts mitjançant els estudis d’ús habitual en aquest tipus de projectes i han servit per a establir una complementació mútua molt útil de cara a futures investigacions. Anglés: The aim of this work is to make a contribution to a research project that deals with the deterioration of road slopes located in two municipalities of the Basque Country. Said research project is carried out by Joan Martinez-Bofill, in collaboration with the Department of crystallography and Mineralogy of the University of Barcelona, the Department of Geotechnical Engineering of the Polytechnic University of Catalonia and the Provincial Government of Gipuzkoa. The main contribution to the project is basically a detailed microtextural and mineralogical study of samples taken from on-site surveys to try to explore in greater depth the causes leading to outcropping materials pathologies. To do so we have considered the use of scanning electron microscopy (BSE-SEM/EDS) with energy-dispersive spectroscopy, and sought to justify the use of this technology in this type of projects, in order to acquire a deeper knowledge and detail of the terrain than that allowed by traditional optical microscopy. The results of these microtextural analyses have been correlated with results of studies commonly used in projects of this kind, and they have helped to establish a degree of mutual complementation that will be useful for future research.