A. Miras

Residence and fractionation of rare earth elements during kaolinization of alkaline peraluminous granites in NW Spain

Abstract A geochemical and mineralogical study has allowed us to address the factors controlling distribution pattern, residence and behaviour of rare earth elements (REE) during kaolinization of Variscan granitoids in NW Spain. Mineral composition of the deeply weathered samples is dominated by kaolinite, with minor amounts of quartz, muscovite-illite, alkaline feldspar and traces of resistant minerals (rutile, ilmenite, zircon and monazite). Variable amounts of Si, Na, Ca, K, Rb, Cs, Ba, U and P were lost from the weathering profile, as a result of feldspars, mica and apatite breakdown, whereas Al, Fe, Ti, Zr, Th, Hf and REE were concentrated in the residual kaolin. Chondrite-normalized REE patterns of the kaolins show an overall enrichment of light REE (LaN/SmN = 1.22 - 2.53), heavy REE depletion (GdN/YbN = 2.42 - 15.10) and a strong negative Eu anomaly (Eu/Eu* = 0.11 - 0.25), probably inherited from the parent granite. Nevertheless, the normalization to the parent granite reveals some REE fractionation and increasing positive Eu anomalies with advancing weathering, in response to the breakdown of feldspars. Different grain-size fractions show similar REE distribution patterns, but differ in concentration levels. Although the fine fractions are the most important REE reservoir, there is no positive correlation with clay mineralogy. The correlative behaviour among P2O5, Th and REE in the <2 μm fraction suggests that monazite plays a dominant role controlling the REE budget in the weathering profile.

Multi-source water pollution in a highly anthropized wetland system associated with the estuary of Huelva (SW Spain).

Major ions, nutrients, trace elements and pesticides distribution were studied in a coastal wetland heavily impacted by human development in Spain. Past land use has altered the local hydrodynamics leading to the partitioning of the ecosystem into a tideland subject to marine influence, and an artificial freshwater reservoir created by stream impoundment. The tideland stretch is flooded twice a day with a heavy metal plume that emerges from the mine-polluted estuary of Huelva and propagates landward depicting the same dispersal trend of major seawater ions. Additionally, the tidal channel receives acid discharges from industrial point sources that contribute to metal enhancement. The impounded area and stream tributaries are affected by agrochemicals runoff (nitrate, phosphate, pendimethalin, simazine, diuron and therbuthylazine) from surrounding agricultural lands. The tidal regime plays a crucial role in the transport and dispersion of pollutants, except in the artificial reservoir where freshwater exhibits a seasonal mineralization pattern.

Technical properties of compounded kaolin sample from Griva (Macedonia, Greece)

Abstract The purpose of this paper is to establish the possible industrial applications of Griva kaolin. This kaolin comes from the alteration of gabbroic rocks from the Griva area, Macedonia, Greece. Mineralogically, the kaolin is composed mainly of kaolinite associated with vermiculite and plagioclases, and traces of quartz, amphiboles, halloysite and smectites. The kaolin grain-size analysis shows that the kaolin is mostly finer than

Properties and applications of diatomitic materials from SW Spain

Abstract Diatomaceous materials (diatomites and diatomitic marls) from the Guadalquivir basin (SW Spain) were characterized mineralogically, physically and physico-chemically. Some potential uses for these materials are suggested based on the results obtained, as well as on laboratory beneficiation tests and applicable specifications. The diatomitic materials are of only fair quality, but, upon appropriate treatment, can be used as catalyst supports, filter aids and lightweight structural ceramic bodies. In addition, the marls can be used for industrial ceramic purposes as constituents of structural clay products to be fired at temperatures between 900 and 1000°C.

Graphite occurrences in the low-pressure/high-temperature metamorphic belt of the Sierra de Aracena (southern Iberian Massif)

Abstract Four distinct associations of graphite have been identified in the low-pressure, high-temperature belt of the Sierra de Aracena (SW Spain). Syngenetic occurrences include: (1) stratiform graphite mineralization within a calc-silicate series; (2) disseminated graphite within a terrigenous sequence; and (3) ‘restitic’ graphite within anatectic tonalites and their enclaves. Epigenetic graphite occurs as (4) veins cross-cutting mafic granulites. Graphite in all types of occurrences is highly crystalline, with the c parameter close to 6.70 Å. Such c values correspond to temperatures of formation of ~800°C. The thermal properties of graphite are also typical of well-ordered graphite and provide DTA exothermic maxima ranging from 810 to 858°C depending on the mode of occurrence. The differences among the temperatures of formation estimated by graphite geothermometry, the position of the exothermic maximum in the DTA curves, and petrologic geothermometers are discussed in terms of the applicability of graphite geothermometry to granulite-facies rocks. Carbon isotope analysis yields δ13C values in the range from -31.6 to -21.4‰ for syngenetic graphite of types I, II and III attributable to biogenically-derived carbon. The heavier signatures for graphite in vein occurrences (δ13C= -17.7 to -18.3‰) with respect to syngenetic graphites suggest that isotopically heavy carbonic species were incorporated into the metamorphic fluids (probably as a consequence of decarbonation reactions of the calc-silicate rocks) from which graphite precipitated into the veins. These fluids were strongly channelled through structural pathways.

Chapter 16 – Sepiolite and Palygorskite as Sealing Materials for the Geological Storage of Carbon Dioxide

Abstract This research provides experimental data on the reactive behaviour of sepiolite and palygorskite with CO2 in presence of water and under dry conditions, at temperatures of interest for geological CO2 sequestration. Results suggest that sepiolite and palygorskite are capable of sequestering CO2 through both a physical and a mineral mechanism. The physical trapping is higher for palygorskite than for sepiolite. But at the same time, these minerals are subject to attack by CO2 in either a dry or a wet environment, leading to partial decomposition of their structure, together with a reduction in volume and mechanical resistance. In the case of palygorskite, however, carbonates formed during reaction with CO2 can precipitate. Thus, a portion of the CO2 is chemically bound (‘trapped’). More importantly, the structural integrity of palygorskite is largely preserved. A geochemical modelling needs to be developed in order to predict the long-term reactive effect of geological CO2 storage when sepiolite- and palygorskite-rich rocks were used as sealing materials.

The life cycle impact assessment applied to the Domingo Rubio tidal system by the study of seasonal variations of the aquatic eutrophication potential.

The innovative technique of Life Cycle Impact Assessment (LCIA) applied to dynamic environmental systems has been recently developed. In this work we investigate a complex system, the Domingo Rubio tideland (Huelva, Spain), where a tidal marsh and a continental lagoon converge. This wetland, catalogued as Natural Park by the Andalusia government, is subjected to a high eutrophicant pressures related to the strawberry culture and the inputs coming from industrial wastes. NO(2)(-), NO(3)(-) and PO(4)(3-) were analyzed in 41 water samples, obtaining values up to 100mg L(-1) Σ(NO(2)(-), NO(3)(-)) and 18.5mg L(-1) PO(4)(3-). All these values exceed the accepted levels by the European Environment Agency. N/P ratios and the Aquatic Eutrophication Potentials (AEP) for N and P showed a constant imbalance of the system. During one tidal cycle, the tidal channel can have both N and P as limiting nutrient (P is the limiting nutrient during low tide and N is during high tide) and there exists an alternation of AEP domination too between N and P in the continental area, what points to an excess of both nutrients all over the study area, and to the necessity of diminishing the nutrient inputs and a higher control on these pollution sources as well.