In situ thermochemical sulfate reduction during ore formation at the Itxaspe Zn-(Pb) MVT occurrence (Basque-Cantabrian basin, Northern Spain)

Organic matter is thought to play a role in the genesis of many Mississippi Valley-type (MVT) deposits, acting as a reducing agent during thermochemical sulfate reduction (TSR). Although TSR is an extremely slow reaction t low temperatures (<100ºC), under favorable conditions it may supply the necessary reduced sulfur during ore formation. To test this hypothesis, the Itxaspe Zn-(Pb) MVT occurrence in the Basque-Cantabrian basin (Northern Spain) was studied. Sphalerite, the main ore phase, is generally found disseminated in Urgonian (Lower Cretaceous) carbonates, and in close relationship with solid bitumen. The bitumen source rock was very likely deposited in a marine marginal setting. Differences in composition of the bitumen samples are attributed to a fractionation during hydrocarbon expulsion and/or migration. The fluids involved in ore deposition were low temperature (Th ~130ºC), Na-Ca-Cl-(K-Mg)-type brines (salinities ~12.5 equiv. mass % NaCl). The origin of brine solutes (including sulfate) is related to the dissolution of Mesozoic evaporite units, although the contribution of evaporated seawater brines cannot be ruled out. The temperatures of ore deposition, the close relationship between the bitumen and ore phases, the presence of aromatic sulfur-bearing compounds and the d34S of sulfides and sulfates are consistent with an in situ TSR during ore formation in the Itxaspe Zn-(Pb) occurrence. Therefore, at least for small mineralizations like Itxaspe, our conclusion is that the necessary reduced sulfur can be supplied by TSR during ore genesis at the site of metal deposition

Introducing Public Procurement

This chapter introduces the concept of public procurement and explains what itis and is not and how it is distinct from private purchasing. To do so it describesthe public-private continuum and explains what publicness is. Subsequently, thepublic procurement process is described using the circular 3P (Prepare, Purchase, and Perform) model. This is followed by a discussion of the seven developmental stages of public procurement. It explains how public procurement has developed over time from an executive management function aimed at fulfilling an internal demand to a policy instrument that can collaboratively create public value. The chapter ends with an explanation of the multifaceted nature of public procurement and why understanding and applying multiple perspectives (e.g., economic, legal, societal, and political) is necessary to bring public procurement into a new era and fully understand and utilize the impact of public procurement

In situ thermochemical sulfate reduction during ore formation at the Itxaspe Zn-(Pb) MVT occurrence (Basque-Cantabrian basin, Northern Spain)

International audienceOrganic matter is thought to play a role in the genesis of many Mississippi Valley-type (MVT) deposits, acting as a reducing agent during thermochemical sulfate reduction (TSR). Although TSR is an extremely slow reaction at low temperatures (<100ºC), under favorable conditions it may supply the necessary reduced sulfur during ore formation. To test this hypothesis, the Itxaspe Zn-(Pb) MVT occurrence in the Basque-Cantabrian basin (Northern Spain) was studied. Sphalerite, the main ore phase, is generally found disseminated in Urgonian (Lower Cretaceous) carbonates, and in close relationship with solid bitumen. The bitumen source rock was very likely deposited in a marine marginal setting. Differences in composition of the bitumen samples are attributed to a fractionation during hydrocarbon expulsion and/or migration. The fluids involved in ore deposition were low temperature (Th ~130ºC), Na-Ca-Cl-(K-Mg)-type brines (salinities ~12.5 equiv. mass % NaCl). The origin of brine solutes (including sulfate) is related to the dissolution of Mesozoic evaporite units, although the contribution of evaporated seawater brines cannot be ruled out. The temperatures of ore deposition, the close relationship between the bitumen and ore phases, the presence of aromatic sulfur-bearing compounds and the 34S of sulfides and sulfates are consistent with an in situ TSR during ore formation in the Itxaspe Zn-(Pb) occurrence. Therefore, at least for small mineralizations like Itxaspe, our conclusion is that the necessary reduced sulfur can be supplied by TSR during ore genesis at the site of metal deposition

Public procurement policy and procurement strategy

In dit hoofdstuk worden de concepten beleid en strategie met betrekking totpubliek inkopen besproken. Inkoopbeleid gaat over de beslissingen en richtlijnen van een publieke organisatie met betrekking tot haar inkoop en gebruik van haar leveranciersbestand. Kaders en richtlijnen van een inkoopbeleid vormen een belangrijke basis voor het ontwikkelen van een specifieke strategie voor een aanbesteding of groep van aanbestedingen. Voor het bepalen van een algemene richting van een inkoopstrategie in de publieke context wordt het Kraljic-portfoliomodel in combinatie met het klantenportfoliomodel van Carter gepresenteerd. Het hoofdstuk eindigt met een beschrijving van verschillende specifieke strategische beslissingen die een inkoper moet maken, zoals de keuze voor het contracteren van een of meerdere leveranciers of de duur van het contract

In situ thermochemical sulfate reduction during ore formation at the Itxaspe Zn-(Pb) MVT occurrence (Basque-Cantabrian basin, Northern Spain)

Organic matter is thought to play a role in the genesis of many Mississippi Valley-type (MVT) deposits, actino as a reducing agent during thermochemical sulfate reduction (TSR). Although TSR is an extremely slow reaction t low temperatures (lt;100ºC), under favorable conditions it may supply the necessary reduced sulfur during ore formation. To test this hypothesis, the Itxaspe Zn-(Pb) MVT occurrence in the Basque-Cantabrian basin (Northern Spain) was studied. Sphalerite, the main ore phase, is generally found disseminated in Urgonian (Lower Cretaceous) carbonates, and in close relationship with solid bitumen. The bitumen source rock was very likely deposited in a marine marginal setting. Differences in composition of the bitumen samples are attributed to a fractionation during hydrocarbon expulsion and/or migration. The fluids involved in ore deposition were low temperature (Th ~130ºC), Na-Ca-Cl-(K-Mg)-type brines (salinities ~12.5 equiv. mass % NaCl). The origin of brine solutes (including sulfate) is related to the dissolution of Mesozoic evaporite units, although the contribution of evaporated seawater brines cannot be ruled out. The temperatures of ore deposition, the close relationship between the bitumen and ore phases, the presence of aromatic sulfur-bearing compounds and the d34S of sulfides and sulfates are consistent with an in situ TSR during ore formation in the Itxaspe Zn-(Pb) occurrence. Therefore, at least for small mineralizations like Itxaspe, our conclusion is that the necessary reduced sulfur can be supplied by TSR during ore genesis at the site of metal deposition

Convective mixing fingers and chemistry interaction in carbon storage

Dissolution of carbon-dioxide into formation fluids during carbon capture and storage (CCS) can generate an instability with a denser CO2-rich fluid located above the less dense native aquifer fluid. This instability promotes convective mixing, enhancing CO2 dissolution and favouring the storage safety. Convective mixing has been extensively analysed in the context of CCS over the last decade, however the interaction between convective mixing and geochemistry has been insufficiently addressed. This relation is explored using a fully coupled model taking into account the porosity and permeability variations due to dissolution-precipitation reactions in a realistic geochemical system based on the Hontomín (Spain) potential CCS site project. This system, located in a calcite, dolomite, and gypsum bearing host rock, has been analysed for a variety of Rayleigh and Damköhler values. Results show that chemical reactions tend to enhance CO2 dissolution. The model illustrates the first stages of porosity channel development, demonstrating the significance of fluid mixing in the development of porosity patterns. The influence of non-carbon species on CO2 dissolution shown in this study demonstrates the needs for realistic chemical and kinetic models to ensure the precision of physical models to accurately represent the carbon-dioxide injection process

Monitorización y verificación de un almacenamiento geológico de CO2. Aplicación de la monitorización superficial en la PDT de Hontomín (Burgos, España)

La necesidad de reducir las emisiones de gases de efecto invernadero ha contribuido al desarrollo de nuevas tecnologías de utilización sostenible de los combustibles fósiles. Destacan entre ellas la captura y almacenamiento de CO2 (CAC), aunque su aplicación industrial aún requiere avances tecnológicos. En este sentido, la Fundación Ciudad de la Energía (CIUDEN) desarrolla un proyecto integral de demostración de las técnicas CAC en el marco del proyecto Compostilla OXYCFB300 financiado por el programa europeo “European Energy Program for Recovery (EEPR)

CO2 soil flux baseline at the technological development plant for CO2 injection at Hontomin (Burgos, Spain)

From the end of 2013 and during the following two years, 20 kt of CO2sc are planned to be injected in a saline reservoir (1500 m depth) at the Hontomín site (NE Spain). The target aquifers are Lower Jurassic limestone formations which are sealed by Lower Cretaceous clay units at the Hontomín site (NE Spain). The injection of CO2 is part of the activities committed in the Technology Development phase of the EC-funded OXYCFB300 project (European Energy Program for Recovery – EEPR, http://www.compostillaproject.eu), which include CO2 injection strategies, risk assessment, and testing and validating monitoring methodologies and techniques. Among the monitoring works, the project is intended to prove that present-day technology is able to monitor the evolution of injected CO2 in the reservoir and to detect potential leakage. One of the techniques is the measurement of CO2 flux at the soil–atmosphere interface, which includes campaigns before, during and after the injection operations. In this work soil CO2 flux measurements in the vicinity of oil borehole, drilled in the eighties and named H-1 to H-4, and injection and monitoring wells were performed using an accumulation chamber equipped with an IR sensor. Seven surveys were carried out from November 2009 to summer 2011. More than 4000 measurements were used to determine the baseline flux of CO2 and its seasonal variations. The measured values were low (from 5 to 13 g m−2 day−1) and few outliers were identified, mainly located close to the H-2 oil well. Nevertheless, these values cannot be associated to a deep source of CO2, being more likely related to biological processes, i.e. soil respiration. No anomalies were recognized close to the deep fault system (Ubierna Fault) detected by geophysical investigations. There, the CO2 flux is indeed as low as other measurement stations. CO2 fluxes appear to be controlled by the biological activity since the lowest values were recorded during autumn-winter seasons and they tend to increase in warm periods. Two reference CO2 flux values (UCL50 of 5 g m−2 d−1 for non-ploughed areas in autumn–winter seasons and 3.5 and 12 g m−2 d−1 for in ploughed and non-ploughed areas, respectively, in spring–summer time, and UCL99 of 26 g m−2 d−1 for autumn–winter in not-ploughed areas and 34 and 42 g m−2 d−1 for spring–summer in ploughed and not-ploughed areas, respectively) were calculated. Fluxes higher than these reference values could be indicative of possible leakage during the operational and post-closure stages of the storage project

Baseline of soil CO2 flux in the Hontomin site (Burgos, Spain)

Baseline of soil CO2 flux in the Hontomin site (Burgos, Spain