Supergene enrichment and exotic mineralization at Chuquicamata, Chile

Ce travail propose une étude détaillée des minéralisations supergènes et exotiques du gisement de type porphyre cuprifère de Chuquicamata (Chili), et avec une emphase sur les minéraux/minéraloïdes peu décrits que sont la chrysocolla, le copper pitch et le copper wad. Dans un deuxième temps, il propose un modèle génétique pour cette minéralisation

Barriers to Environmental Innovation in SMEs: Empirical Evidence from French Firms

International audienceRecent literature explores the determinants of environmental innovations (EI) but rarely addresses obstacles to these innovations. To our knowledge, no previous study accounts for antecedents of EI to explore the various perceived barriers to EI for small and medium-sized enterprises (SMEs). Noting the importance of SMEs in European economies, this article identifies the extent to which SMEs perceive barriers to environmental innovations, considering their type, number, and intensity. With a merged data set of 435 French SMEs, we investigate different perceptions of environmentally innovative SMEs, compared with those of technologically innovative SMEs and non-innovative ones, using a multiple treatment model that integrates the antecedents. We thereby analyze SME CEO's perceptions of barriers to EI. The barriers are not only more numerous but also more important for SMEs that engage in environmental innovation activity compared with those that have introduced only technological innovation or those that do not undertake any innovation activity

Genesis of the exotic chrysocolla — “copper pitch/wad” — atacamite/brochantite ore at the Exótica (Mina Sur) deposit, Chuquicamata, Chile

Detailed mineralogical and textural studies, combined with sequential X-ray diffraction and geochemical modeling, helped to solve the “copper pitch/wad” enigma in the Exótica deposit located downstream of the Chuquicamata porphyry copper deposit. Copper pitch and copper wad are essentially chrysocolla with co-precipitated Mn oxides, mainly birnessite, as well as pseudo-amorphous Mn oxide/oxyhydroxides. Linking the mineralogical, geochemical, and textural evidences with the geological, tectonic, and climatic evolution of the Chuquicamata–Calama area, a four-step genetic model for the evolution of the Exótica deposit is presented: (A) formation of a mature supergene enrichment profile at Chuquicamata (~ 30–25 Ma to ~ 15 Ma) during an erosion-dominated regime (∼900 m of erosion) which was accompanied by acidic (pH ∼2–4) Cu-Mn-Si-dominated rock drainage (ARD) with fluid flow southwards through the Exótica valley towards the Calama Basin, resulting in a strongly kaolinized and chrysocolla/copper wad-impregnated bedrock of the Exótica deposit; (B) deposition of the Fortuna gravels in the Exótica valley (starting ∼19 Ma) intercepted the Cu-Mn-Si-dominated ARD, triggering the main chrysocolla, copper pitch/wad mineralization as syn-sedimentary mineralization by chiefly surficial flow in strongly altered gravels; (C) tectonic freezing and onset of hyper-aridity (∼15–11 Ma) exposed the enriched chalcocite blanket of Chuquicamata to oxidation, resulting in acidic (pH ~ 2–4) and Cu-Si-dominated solutions with less Mn. These solutions percolated in a slightly more reducing groundwater flow path and mineralized relatively unaltered gravels with pure chrysocolla; and (D) ingression of confined chloride-rich groundwater in the upper oxidation zone of Chuquicamata, most likely between 6 and 3 Ma, is responsible for the atacamite/brochantite mineralization (pH ~ 5.5–7) of mainly unaltered gravels in the northern and central part of the Exótica deposit.</p

Reported supergene sphalerite rims at the Chuquicamata porphyry deposit (northern Chile) revisited: Evidence for a hypogene origin

Previous studies attributed a supergene origin to sphalerite rimming copper minerals occurring in Chuquicamata in a mineral assemblage including typically chalcocite-digenite (Cu1.85S1.12 and u1.99S1.01), covellite(CuS and Cu1.08S0.92), and sphalerite (up to 1.2 wt % Fe). Microscopic observations on samples from a central and a southern section, completed by scanning electronic microscope (SEM) backscattering electron imaging and electron microprobe analyses, suggest that all sphalerite in Chuquicamata is hypogene. A scenario, backed by observations in each step, that explains the formation of the peculiar “sphalerite rims” is the following: (1) precipitation of chalcopyrite, typical of the early and main hydrothermal stages; (2) precipitation of sphalerite rimming chalcopyrite and in voids and in weakness sites during the late hydrothermal stage; (3) partial or total replacement of chalcopyrite by chalcocite-digenite during the late hydrothermal stage; and (4) formation of lamellar covellite, principally at the expense of chalcopyrite, suggesting increasingly oxidizing and/or acidic conditions. This covellite may be linked to supergene processes and/or to the late hydrothermal stage. The findings of the present work have implications for the position of the lower limit of the supergene enrichment in the eastern-southern part of the deposit, as the sphalerite rims, now interpreted as hypogene, were the only potential supergene sulfide in the eastern vertical section of the southern section

The supergene enrichment at Chuquicamata revisited

Using archived samples, two comprehensive vertical profiles in the central part of the Chuquicamata open pit have been studied. The observed textures and mineralogy suggest, at the preliminary stage of the study,that digenite and sphalerite might be predominantly or entirely hypogene. Covellite and chalcocite can be both hypogene and supergene, but textural analysis allows a discrimination in certain cases

Integrin and autocrine IGF2 pathways control fasting insulin secretion in β-cells

Elevated levels of fasting insulin release and insufficient glucose-stimulated insulin secretion (GSIS) are hallmarks of diabetes. Studies have established cross-talk between integrin signaling and insulin activity, but more details of how integrin-dependent signaling impacts the pathophysiology of diabetes are needed. Here, we dissected integrin-dependent signaling pathways involved in the regulation of insulin secretion in β-cells and studied their link to the still debated autocrine regulation of insulin secretion by insulin/insulin-like growth factor (IGF) 2-AKT signaling. We observed for the first time a cooperation between different AKT isoforms and focal adhesion kinase (FAK)-dependent adhesion signaling, which either controlled GSIS or prevented insulin secretion under fasting conditions. Indeed, β-cells form integrin-containing adhesions, which provide anchorage to the pancreatic extracellular matrix and are the origin of intracellular signaling via FAK and paxillin. Under low-glucose conditions, β-cells adopt a starved adhesion phenotype consisting of actin stress fibers and large peripheral focal adhesion. In contrast, glucose stimulation induces cell spreading, actin remodeling, and point-like adhesions that contain phospho-FAK and phosphopaxillin, located in small protrusions. Rat primary β-cells and mouse insulinomas showed an adhesion remodeling during GSIS resulting from autocrine insulin/IGF2 and AKT1 signaling. However, under starving conditions, the maintenance of stress fibers and the large adhesion phenotype required autocrine IGF2-IGF1 receptor signaling mediated by AKT2 and elevated FAK-kinase activity and ROCK-RhoA levels but low levels of paxillin phosphorylation. This starved adhesion phenotype prevented excessive insulin granule release to maintain low insulin secretion during fasting. Thus, deregulation of the IGF2 and adhesion-mediated signaling may explain dysfunctions observed in diabetes

Mineralogía de la mineralización exótica en Chuquicamata: nuevos avances

La mineralización exótica del pórfido cuprífero de Chuquicamata está constituida por minerales bien identificados como atacamita, crisocola, pseudomalaquita, paracoquimbita, paratacamita, ebethenita, sampleita y óxidos de manganeso, y otros menos bien estudiados, llamados genéricamente “copper-wad” y “copper-pitch”. Estos dos últimos términos sugieren mineralogías habitualmente descritas en la mineralización exótica, pero que no hacen referencia a estructuras cristalinas y rangos de composición definidos. El estudio de la composición química de las muestras de “copper-wad” y “copperpitch” indica contenidos variables principalmente en sílice, hierro, manganeso, aluminio, cobre y azufre, pero no se diferencian entre ellos. La difracción de rayos X pone de manifiesto estructuras débilmente cristalinas (incluso amorfas), con presencia de pequeñas fases cristalinas, principalmente yeso y atacamita