Geochemical and mineralogical investigations of fine growth structures of ferromanganese nodules from the Clarion and Clipperton Zone, Pacific Ocean

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Conhecimentos e opiniões de médicos e farmacêuticos acerca dos genéricos versus padrões de prescrição/dispensa

Objectivos (Objectives): Na actual situação da economia portuguesa, a política do medicamento assume uma importância primordial na prossecução de uma redução da despesa pública com medicamentos para 1,25% do PIB até final de 2012 e para cerca de 1% do PIB em 2013, conforme o acordo estabelecido com as entidades internacionais. No entanto, do ponto de vista do cidadão, a despesa privada em medicamentos é também uma temática na ordem do dia. Poucos temas são tão controversos na área da política do medicamento como a introdução de genéricos no mercado de medicamentos, contudo, estes podem desempenhar um papel fundamental na optimização da afectação de recursos. São muitas as questões levantadas contra e a favor da qualidade, segurança e eficácia dos genéricos. Se os médicos, através da prescrição, são o factor decisivo para o aumento da quota de genéricos; os farmacêuticos enquanto dispensadores assumem um papel preponderante na sensibilização dos utentes para a sua aceitação e adesão à terapêutica. Objectivo: O presente estudo pretende estudar os conhecimentos e opiniões de médicos e farmacêuticos face aos medicamentos genéricos e as suas relações com a prescrição/dispensa de genéricos. Metodologia (Methodology): Foi enviado, via postal, um inquérito por questionário a uma amostra de médicos e farmacêuticos. Responderam 261 indivíduos, 158 médicos e 103 farmacêuticos. O inquérito foi validado por um painel de juízes e demonstrou uma boa consistência interna. Para efectuar a comparação entre as respostas dos diferentes grupos, recorreu-se ao teste t para amostras independentes. Resultados (Results): 75,9% dos inquiridos, considerou que o medicamento genérico é bioequivalente ao de referência mas apenas 58,7% disse acreditar que um fármaco genérico, no processo de preparação, oferece as mesmas garantias de qualidade. Verificou-se que os médicos que têm mais conhecimentos e opinião mais favorável sobre os genéricos prescrevem genéricos com mais frequência (p <0.001). Constatou-se que os farmacêuticos têm mais conhecimentos (p <0.008) sobre os medicamentos genéricos que os médicos e que manifestaram respostas mais positivas (p <0.001). Conclusões (Conclusions): Médicos e farmacêuticos acreditam que a despesa em medicamentos é um factor a ter em atenção no momento da prescrição/dispensa de medicamentos. Subsistem, no entanto, algumas crenças erróneas sobre a qualidade do medicamento genérico. Tal facto reforça a necessidade de políticas activas de promoção dos medicamentos genéricos

Sulfide enrichment along igneous layer boundaries in the lower oceanic crust: IODP Hole U1473A, Atlantis Bank, Southwest Indian Ridge

Reactive porous or focused melt flows are common in crystal mushes of mid-ocean ridge magma reservoirs. Although they exert significant control on mid-ocean ridge magmatic differentiation, their role in metal transport between the mantle and the ocean floor remains poorly constrained. Here we aim to improve such knowledge for oceanic crust formed at slow-spreading centers (approximately half of present-day oceanic crust), by focusing on specific igneous features where sulfides are concentrated. International Ocean Discovery Program (IODP) Expedition 360 drilled Hole U1473A 789 m into the lower crust of the Atlantis Bank oceanic core complex, located at the Southwest Indian Ridge. Coarse-grained (5–30 mm) olivine gabbro prevailed throughout the hole, ranging locally from fine- (&lt;1 mm), to very coarse-grained (&gt;30 mm). We studied three distinct intervals of igneous grain size layering at 109.5–110.8, 158.0–158.3, and 593.0–594.4 meters below seafloor to understand the distribution of sulfides. We found that the layer boundaries between the fine- and coarse-grained gabbro were enriched in sulfides and chalcophile elements. On average, sulfide grains throughout the layering were composed of pyrrhotite (81 vol.%; Fe1-xS), chalcopyrite (16 vol.%; CuFeS2), and pentlandite (3 vol.%; [Ni,Fe,Co]9S8), which reflect paragenesis of magmatic origin. The sulfides were most commonly associated with Fe-Ti oxides (titanomagnetites and ilmenites), amphiboles, and apatites located at the interstitial positions between clinopyroxene, plagioclase, and olivine. Pentlandite exsolution textures in pyrrhotite indicate that the sulfides formed from high-temperature sulfide liquid separated from mafic magma that exsolved upon cooling. The relatively homogenous phase proportion within sulfides along with their chemical and isotopic compositions throughout the studied intervals further support the magmatic origin of sulfide enrichment at the layer boundaries. The studied magmatic layers were likely formed as a result of intrusion of more primitive magma (fine-grained gabbro) into the former crystal mush (coarse-grained gabbro). Sulfides from the coarse-grained gabbros are Ir-Platinum Group Element-rich (PGE; i.e., Ir, Os, Ru) but those from the fine-grained gabbros are Pd-PGE-rich (i.e., Pd, Pt, Rh). Notably, the sulfides from the layer boundaries are also enriched in Pd-PGEs, and therefore elevated sulfide contents at the boundaries were likely related to the new intruding melt. Because S concentration at sulfide saturation level is dependent on the Fe content of the melt, sulfide crystallization may have been caused by FeO loss, both via crystallization of late-precipitating oxides at the boundaries, and by exchange of Fe and Mg between melt and Fe-bearing silicates (olivine and clinopyroxene). The increased precipitation of sulfide grains at the layer boundaries might be widespread in the lower oceanic crust, as also observed in the Semail ophiolite and along the Mid-Atlantic Ridge. Therefore, this process might affect the metal budget of the global lower oceanic crust. We estimate that up to ∼20% of the Cu, ∼8% of the S, and ∼84% of the Pb of the oceanic crust inventory is accumulated at the layer boundaries only from the interaction between crystal mush and new magma. © 2022 The Author

Sulfide enrichment along igneous layer boundaries in the lower oceanic crust: IODP Hole U1473A, Atlantis Bank, Southwest Indian Ridge

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Pieterek, B., Ciazela, J., Boulanger, M., Lazarov, M., Wegorzewski, A., Pańczyk, M., Strauss, H., Dick, H. J. B., Muszyński, A., Koepke, J., Kuhn, T., Czupyt, Z., & France, L. Sulfide enrichment along igneous layer boundaries in the lower oceanic crust: IODP Hole U1473A, Atlantis Bank, Southwest Indian Ridge. Geochimica et Cosmochimica Acta, 320, (2022): 179–206, https://doi.org/10.1016/j.gca.2022.01.004.Reactive porous or focused melt flows are common in crystal mushes of mid-ocean ridge magma reservoirs. Although they exert significant control on mid-ocean ridge magmatic differentiation, their role in metal transport between the mantle and the ocean floor remains poorly constrained. Here we aim to improve such knowledge for oceanic crust formed at slow-spreading centers (approximately half of present-day oceanic crust), by focusing on specific igneous features where sulfides are concentrated. International Ocean Discovery Program (IODP) Expedition 360 drilled Hole U1473A 789 m into the lower crust of the Atlantis Bank oceanic core complex, located at the Southwest Indian Ridge. Coarse-grained (5–30 mm) olivine gabbro prevailed throughout the hole, ranging locally from fine- (30 mm). We studied three distinct intervals of igneous grain size layering at 109.5–110.8, 158.0–158.3, and 593.0–594.4 meters below seafloor to understand the distribution of sulfides. We found that the layer boundaries between the fine- and coarse-grained gabbro were enriched in sulfides and chalcophile elements. On average, sulfide grains throughout the layering were composed of pyrrhotite (81 vol.%; Fe1-xS), chalcopyrite (16 vol.%; CuFeS2), and pentlandite (3 vol.%; [Ni,Fe,Co]9S8), which reflect paragenesis of magmatic origin. The sulfides were most commonly associated with Fe-Ti oxides (titanomagnetites and ilmenites), amphiboles, and apatites located at the interstitial positions between clinopyroxene, plagioclase, and olivine. Pentlandite exsolution textures in pyrrhotite indicate that the sulfides formed from high-temperature sulfide liquid separated from mafic magma that exsolved upon cooling. The relatively homogenous phase proportion within sulfides along with their chemical and isotopic compositions throughout the studied intervals further support the magmatic origin of sulfide enrichment at the layer boundaries. The studied magmatic layers were likely formed as a result of intrusion of more primitive magma (fine-grained gabbro) into the former crystal mush (coarse-grained gabbro). Sulfides from the coarse-grained gabbros are Ir-Platinum Group Element-rich (PGE; i.e., Ir, Os, Ru) but those from the fine-grained gabbros are Pd-PGE-rich (i.e., Pd, Pt, Rh). Notably, the sulfides from the layer boundaries are also enriched in Pd-PGEs, and therefore elevated sulfide contents at the boundaries were likely related to the new intruding melt. Because S concentration at sulfide saturation level is dependent on the Fe content of the melt, sulfide crystallization may have been caused by FeO loss, both via crystallization of late-precipitating oxides at the boundaries, and by exchange of Fe and Mg between melt and Fe-bearing silicates (olivine and clinopyroxene). The increased precipitation of sulfide grains at the layer boundaries might be widespread in the lower oceanic crust, as also observed in the Semail ophiolite and along the Mid-Atlantic Ridge. Therefore, this process might affect the metal budget of the global lower oceanic crust. We estimate that up to ∼20% of the Cu, ∼8% of the S, and ∼84% of the Pb of the oceanic crust inventory is accumulated at the layer boundaries only from the interaction between crystal mush and new magma.This research was funded by National Science Centre Poland (PRELUDIUM 12 no. 2016/23/N/ST10/00288), Graduate Academy of the Leibniz Universität Hannover (60421784), and ECORD Research Grant to J. Ciazela, as well as Deutsche Forschungsgemeinschaft (KO1723/23-1) to J. Koepke and H. Strauss. J. Ciazela is additionally supported within the START program of the Foundation for Polish Science (FNP). This is CRPG contribution No. 2813

Hydrogenetic, Diagenetic and Hydrothermal Processes Forming Ferromanganese Crusts in the Canary Island Seamounts and Their Influence in the Metal Recovery Rate with Hydrometallurgical Methods

Four pure hydrogenetic, mixed hydrogenetic-diagenetic and hydrogenetic-hydrothermal Fe-Mn Crusts from the Canary Islands Seamount Province have been studied by Micro X-Ray Diffraction, Raman and Fourier-transform infrared spectroscopy together with high resolution Electron Probe Micro Analyzer and Laser Ablation Inductively Coupled Plasma Mass Spectrometry in order to find the correlation of mineralogy and geochemistry with the three genetic processes and their influence in the metal recovery rate using an hydrometallurgical method. The main mineralogy and geochemistry affect the contents of the different critical metals, diagenetic influenced crusts show high Ni and Cu (up to 6 and 2 wt. %, respectively) (and less Co and REY) enriched in very bright laminae. Hydrogenetic crusts on the contrary show High Co and REY (up to 1 and 0.5 wt. %) with also high contents of Ni, Mo and V (average 2500, 600 and 1300 μg/g). Finally, the hydrothermal microlayers from crust 107-11H show their enrichment in Fe (up to 50 wt. %) and depletion in almost all the critical elements. One hydrometallurgical method has been used in Canary Islands Seamount Province crusts in order to quantify the recovery rate of valuable elements in all the studied crusts except the 107-11H, whose hydrothermal critical metals’ poor lamina were too thin to separate from the whole crust. Digestion treatment with hydrochloric acid and ethanol show a high recovery rate for Mn (between 75% and 81%) with respect to Fe (49% to 58%). The total recovery rate on valuable elements (Co, Ni, Cu, V, Mo and rare earth elements plus yttrium (REY)) for the studied crusts range between 67 and 92% with the best results for Co, Ni and V (up to 80%). The genetic process and the associated mineralogy seem to influence the recovery rate. Mixed diagenetic/hydrogenetic crust show the lower recovery rate for Mn (75%) and Ni (52.5%) both enriched in diagenetic minerals (respectively up to 40 wt. % and up to 6 wt. %). On the other hand, the presence of high contents of undigested Fe minerals (i.e., Mn-feroxyhyte) in hydrogenetic crusts give back low recovery rate for Co (63%) and Mo (42%). Finally, REY as by-product elements, are enriched in the hydrometallurgical solution with a recovery rate of 70–90% for all the studied crusts

X-ray absorption spectroscopy study of Mn reference compounds for Mn speciation in terrestrial surface environments

X-ray absorption spectroscopy (XAS) offers great potential to identify and quantify Mn species in surface environments by means of linear combination fit (LCF), fingerprint, and shell-fit analyses of bulk Mn XAS spectra. However, these approaches are complicated by the lack of a comprehensive and accessible spectrum library. Additionally, molecular-level information on Mn coordination in some potentially important Mn species occurring in soils and sediments is missing. Therefore, we investigated a suite of 32 natural and synthetic Mn reference compounds, including Mn oxide, oxyhydroxide, carbonate, phosphate, and silicate minerals, as well as organic and adsorbed Mn species, by Mn K-edge X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy. The ability of XAS to infer the average oxidation state (AOS) of Mn was assessed by comparing XANES-derived AOS with the AOS obtained from redox titrations. All reference compounds were studied for their local (<5 Å) Mn coordination environment using EXAFS shell-fit analysis. Statistical analyses were employed to clarify how well and to what extent individual Mn species groups) can be distinguished by XAS based on spectral uniqueness. Our results show that LCF analysis of normalized XANES spectra can reliably quantify the Mn AOS within ~0.1 v.u. in the range +2 to +4. These spectra are diagnostic for most Mn species investigated, but unsuitable to identify and quantify members of the manganate and Mn(III)-oxyhydroxide groups. First-derivative XANES fingerprinting allows the unique identification of pyrolusite, ramsdellite, and potentially lithiophorite within the manganate group. However, XANES spectra of individual Mn compounds can vary significantly depending on chemical composition and/or crystallinity, which limits the accuracy of XANES-based speciation analyses. In contrast, EXAFS spectra provide a much better discriminatory power to identify and quantify Mn species. Principal component and cluster analyses of k$^2$-weighted EXAFS spectra of Mn reference compounds implied that EXAFS LCF analysis of environmental samples can identify and quantify at least the following primary Mn species groups: (1) Phyllo- and tectomanganates with large tunnel sizes (2 × 2 and larger; hollandite sensu stricto, romanèchite, todorokite); (2) tectomanganates with small tunnel sizes (2 × 2 and smaller; cryptomelane, pyrolusite, ramsdellite); (3) Mn(III)-dominated species (nesosilicates, oxyhydroxides, organic compounds, spinels); (4) Mn(II) species (carbonate, phosphate, and phyllosilicate minerals, adsorbed and organic species); and (5) manganosite. All Mn compounds, except for members of the manganate group (excluding pyrolusite) and adsorbed Mn(II) species, exhibit unique EXAFS spectra that would allow their identification and quantification in mixtures. Therefore, our results highlight the potential of Mn K-edge EXAFS spectroscopy to assess bulk Mn speciation in soils and sediments. A complete XAS-based speciation analysis of bulk Mn in environmental samples should preferably include the determination of Mn valences following the “Combo” method of Manceau et al. (2012), EXAFS LCF analyses based on principal component and target transformation results, as well as EXAFS shell-fit analyses for the validation of LCF results. For this purpose, all 32 XAS reference spectra are provided in the Online Materials1 for further use by the scientific community

Mineralogical transformations in polymetallic nodules and the change of Ni, Cu and Co crystal-chemistry upon burial in sediments

International audiencePolymetallic nodules from the Clarion and Clipperton Zone of the equatorial Pacific Ocean were studied using X-ray diffraction, X-ray absorption, Fourier-transformed infrared spectroscopy and transmission electron microscopy. This study includes nodules found at the sediment surface as well as subsurface (14–16 cm sediment depth) and deeply buried (530–985 cm sediment depth) nodules. The surface and subsurface nodules are currently under oxic conditions whereas the deeply buried nodules are under suboxic conditions. Surface nodules consist mainly of turbostratic phyllomanganates (7 Å and 10 Å vernadite and Fe-vernadite); todorokite is a minor phase, if present at all. In contrast, subsurface and especially deeply buried nodules predominantly consist of todorokite, which increases in abundance with depth in the sediment. Thus, upon burial of nodules within the shallow sediment, phyllomanganates transform to todorokite, probably through the combined action of time and change in the ambient chemical conditions. Nodules from deeper sediment depth (>500 cm) consist primarily of todorokite and additionally show signs of dissolution.The transformation of phyllomanganates to todorokite and their further dissolution upon nodule burial under suboxic conditions induces modifications in the crystal-chemistry of Ni, Co, and Cu. In surface nodules, Ni and Co are incorporated in the octahedral sheets of phyllomanganates, whereas Cu mainly is located at the edges of those phyllomanganate sheets. In buried nodules Cu and to a lesser extent Ni are incorporated in todorokite by forming outer-sphere complexes within the tunnels. However, Ni is predominantly incorporated within the octahedra of the newly formed todorokite structure. Co is also enriched in the octahedra of todorokite as a result of dissolution of hydrogenetic vernadite and re-incorporation in the more stable Mn-phase formed during the diagenetic transformation. Co enrichment under suboxic conditions after burial within the sediments is noteworthy since Co in surface nodules is characteristic for oxic conditions

The geochemical behavior of metals during early diagenetic alteration of buried manganese nodules

Highlights • This paper investigates the dissolution of Mn nodules buried in suboxic sediments. • Hydrogenetic layers start to dissolve first, whereas diagenetic layers are stable. • Cobalt, thungsten and barium are strongly enriched in buried nodules. • Cobalt enrichment results from a redox reaction with manganese. • Molybdenum, zinc and lithium are depleted in buried nodules. • Iron oxides from the hydrogenetic layers form authigenic phases. • These authigenic phases consist of nontronite and goethite. Abstract Marine polymetallic nodules and crusts represent an important resource for numerous metals such as Ni, Co, Cu, Mn and thus may be subject to deep sea mining operations in the future. Manganese nodules have a widespread occurrence on the seafloor of the Clarion-Clipperton Zone (CCZ) in the equatorial North Pacific and have been intensively studied in the past. They consist of hydrogenetic layers formed by precipitation from ambient oxic seawater and diagenetic layers sourced from suboxic pore water. While numerous studies have focused on nodules found on the sediment surface, only a few have dealt with nodules buried at greater sediment depth. In this study, we have thus systematically investigated the diagenetic processes altering the chemical and mineralogical composition of buried nodules in the eastern CCZ down to a sediment depth of around 10 m and assessed the influence of these processes on sediment geochemistry. Our results show that nodules subject to suboxic conditions are not simply reductively dissolved but react with the surrounding sediment and pore water. After burial, the hydrogenetic layers start to dissolve and the associated metals (Mn, Ni, Co, Cu, Mo) are released into the pore water. The remaining Fe oxides react with the surrounding sediment and pore water to form an authigenic Fe-Si-Al-rich layer consisting of nontronite and goethite. The diagenetic layers of buried nodules were found to be highly enriched in Co and Ba and strongly depleted in Mo, Zn and Li compared to surface nodules. The strong, up to 4-fold enrichment of Co during burial under suboxic conditions is noteworthy since the distribution of this element in nodules is commonly used as a proxy for oxic conditions in surface sediments. Here, the Co enrichment is interpreted to result from a redox reaction with Mn. When suboxic conditions in the sediment prevail long enough, the diagenetic Mn oxide phases are also reductively dissolved and only the Fe-oxide component of the former nodule remains. Under the changing redox conditions associated with burial, Mn nodules exert a strong control on the mobility of metals by either fixing them into the crystal lattice of the Mn mineral phases or releasing them into pore water during their reductive dissolution

Mineralogy and chemical composition of ferromanganese crusts from the Cruzeiro do Sul Lineament - Rio Grande Rise, South Atlantic

Samples dredged from the Cruzeiro do Sul Lineament exhibit ferromanganese crusts precipitated above phosphate-rich substrates (phosphorites, phosphate-impregnated volcanic rocks and older phosphatized ferromanganese crusts). Co-chronology of the crusts, paleontological data and 87Sr/86Sr ratios of the phosphatized substrate indicate that the last phosphatization event in the region happened between 17.6 and 14.6 Ma ago. When the event ceased, oxic conditions were resumed and hydrogenetic crust precipitation started at a maximum rate of 1.6–3.0 mm/Ma, forming layers of Fe-vernadite above the phosphorites. These crusts differ in composition from crusts that formed prior to the phosphatization, which were impregnated by carbonate fluorapatite and recrystallized forming a 10 Å Mn-phase, in expense of a lower crystallinity Mn-phase. Mn/Fe ratios of non-phosphatized crusts vary from 1.05 to 1.41. The Mn/Fe ratios as well as the metal content (Co = 0.65–1.04 wt%, Zn = 0.04–0.06 wt%, Cu = 0.02–0.06 wt% and Ni = 0.29–0.48 wt%) are similar to hydrogenetic crusts described in other parts of the world

Towards balancing the oceanic Ni budget

Nickel isotopes are a novel and promising tracer of the chemistry of past ocean environments, but realisation of this tracer's potential requires a comprehensive understanding of the controls on Ni burial in the marine sedimentary archive. An outstanding puzzle in the marine budget of Ni, first recognised in the 1970s, is a major imbalance in the known inputs and outputs to and from the ocean: the sedimentary outputs of Ni are much larger than the inputs (rivers, dust). Much more recently, it has also been recognised that the outputs are also considerably isotopically heavier than the inputs. In this study, we find light Ni isotope compositions (δ60NiNIST SRM986 = −0.2 to −0.8‰) for Mn-rich sediments from the eastern Pacific compared to Fe-Mn crusts (at about +1.6‰). These data suggest that diagenetic remobilisation of isotopically heavy Ni leads to a significant benthic Ni flux (estimated at 0.6−2.3×108 mol/yr), similar in magnitude to the riverine flux, to the ocean. Diagenetic remobilisation of Ni may occur either via cycles of Mn-oxide dissolution and precipitation, with associated Ni sorption and release, or during mineralogical transformation of birnessite to todorokite. A minor role for retention of isotopically light Ni by Fe oxides or Fe-rich authigenic clays is also proposed. Overall, a benthic flux of isotopically heavy Ni (at about +3‰) can balance the marine Ni budget, pinpointing diagenesis as a key missing piece of the Ni puzzle. © 2020 Elsevier B.V.ISSN:0012-821XISSN:1385-013