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Padron-Navarta J.A.,University of Granada | Hermann J.,Australian National University | Garrido C.J.,Instituto Andaluz Of Ciencias Of La Tierra Iact | Lopez Sanchez-Vizcaino V.,University of Jaen | Gomez-Pugnaire M.T.,University of Granada
Contributions to Mineralogy and Petrology | Year: 2010

Piston cylinder experiments were performed to constrain the pressure and temperature conditions for two high-pressure antigorite dehydration reactions found in silica-enriched serpentinites from Cerro del Almirez (Nevado-Filábride Complex, Betic Cordillera, southern Spain). At 630-660°C and pressures greater than 1.6 GPa, antigorite first reacts with talc to form orthopyroxene ± chlorite + fluid. We show that orthopyroxene + antigorite is restricted to high-pressure metamorphism of silica-enriched serpentinite. This uncommon assemblage is helpful in constraining metamorphic conditions in cold subduction environments, where antigorite serpentinites have no diagnostic assemblages over a large pressure and temperature range. The second dehydration reaction leads to the breakdown of antigorite to olivine + orthopyroxene + chlorite + fluid. The maximum stability of antigorite is found at 680°C at 1.9 GPa, which also corresponds to the maximum pressure limit for tremolite coexisting with olivine + orthopyroxene. The high aluminium (3.70 wt% Al2O3) and chromium contents (0.59 wt% Cr 2O3) of antigorite in the investigated starting material is responsible for the expansion of the serpentinite stability to 60-70°C higher temperatures at 1.8 GPa than the antigorite stability calculated in the Al-free system. The antigorite from our study has the highest Al-Cr contents among all experimental studies and therefore likely constraints the maximum stability of antigorite in natural systems. Comparison of experimental results with olivine-orthopyroxene-chlorite-tremolite assemblages outcropping in Cerro del Almirez indicates that peak metamorphic conditions were 680-710°C and 1.6-1.9 GPa. © 2009 Springer-Verlag. Source

La Rubia-Garcia M.D.,University of Jaen | Yebra-Rodriguez A.,University of Jaen | Eliche-Quesada D.,University of Jaen | Corpas-Iglesias F.A.,University of Jaen | Lopez-Galindo A.,Instituto Andaluz Of Ciencias Of La Tierra Iact
Construction and Building Materials | Year: 2012

The disposal of olive oil industrial waste is an environmental problem regardless of the manufacturing process. Contamination of soils with wet pomace (a waste product of the two-phase olive oil extraction method) can be a serious problem. Moreover, it cannot be composted or burned without expensive pre-treatment. In this work, we used wet pomace as a pore-forming additive in the manufacture of clay bricks to evaluate the possibility of obtaining a lightweight construction material with good insulating characteristics. To this end, bricks were prepared by adding 5, 10, 15, 20, and 25 wt% wet pomace to the clay without additional water. The results indicate that the incorporation of 10 wt% wet pomace is beneficial for manufacturing good-quality bricks, obtaining an apparent density of 1.43 g/cm 3, a compressive strength of 40.22 MPa, and a thermal conductivity of 0.72 W/mK. © 2012 Elsevier Ltd. All rights reserved. Source

Pesquera A.,University of the Basque Country | Torres-Ruiz J.,University of Granada | Garcia-Casco A.,University of Granada | Garcia-Casco A.,Instituto Andaluz Of Ciencias Of La Tierra Iact | Gil-Crespo P.P.,University of the Basque Country
Journal of Petrology | Year: 2013

Tourmaline occurs in peraluminous granites from the Central Iberian Zone associated with two main AFM mineral assemblages: (1) muscovite + biotite ± cordierite ± andalusite in the Araya-type granites; (2) muscovite ± biotite ± garnet in leucogranites from the Alamo complex. When tourmaline is dominant, biotite is an accessory or absent, and vice versa. We present field and petrographic relations, mineral chemistry, and geochemical data for tourmaline-bearing and tourmaline-free granitic rocks from various localities in the Central Iberian Zone. Compositional phase diagrams are used to evaluate the factors controlling the occurrence of tourmaline relative to biotite in granitic rocks, with particular emphasis on the relationships between mineral assemblage and whole-rock chemistry and its petrological implications. Although tourmaline stability in felsic magmas depends on the interplay between rates of changing environmental conditions such as bulk composition, T, aH2O, and fO2, the principal factor dictating tourmaline formation is the B content of the melt, judging from phase relations. In short, regardless of other variables, granitic melts have to surpass a critical boron threshold to achieve tourmaline saturation. Experimental constraints, combined with petrographic and geochemical data, suggest minimum boron contents in the range of ∼500-3000 μg g-1 (depending on temperature) to saturate melt in tourmaline. Acting in concert with boron content, other variables such as Al2O3, mafic components, T, fO2, and so on, control not only the formation of tourmaline during melt crystallization, but also the magnitude of boron loss from the magma to the surrounding rocks. The analysis of phase relations suggests that tourmaline granites usually form units distinct from biotite granites because common granitic melts have restricted accessibility to the three-phase Tur-Bt-Ms field. © The Author 2012. Published by Oxford University Press. All rights reserved. Source

Berkesi M.,Eotvos University Budapest | Guzmics T.,Eotvos University Budapest | Szabo C.,Eotvos University Budapest | Dubessy J.,University of Lorraine | And 3 more authors.
Earth and Planetary Science Letters | Year: 2012

Upper mantle peridotite xenoliths from the Tihany Maar Volcanic Complex, Bakony-Balaton Highland Volcanic Field (Central Pannonian Basin, Hungary) contain abundant pyroxene-hosted negative crystal shaped CO 2-rich fluid inclusions. The good correlation between enrichment of the clinopyroxenes in Al 2O 3, TiO 2, Na 2O, MREE and Zr, and the presence of fluid inclusions in the xenoliths provide strong evidence for fluid-related cryptic metasomatism of the studied xenoliths. The FIB-SEM (focused ion beam-scanning electron microscopy) exposure technique revealed a thin glass film, covering the wall of the fluid inclusions, which provides direct evidence that the silicate components were formerly dissolved in the CO 2-rich fluid phase. This means that at upper mantle conditions CO 2-rich fluids are capable of transporting trace and major elements, and are the agents responsible for cryptic metasomatism of the peridotite wall rock.Several daughter phases, including magnesite, quartz and sulfide, were identified in the fluid inclusions. Magnesite and quartz are the products of a post entrapment carbonation reaction, whereby the reactants are the CO 2-rich fluid and the host orthopyroxene. It is likely that the thin glass film prevented or arrested further growth of the magnesite and quartz by isolating the fluid from the host orthopyroxene, resulting in the preservation of residual CO 2 in the fluid inclusions. © 2012 Elsevier B.V. Source

Padron-Navarta J.A.,Montpellier University | Tommasi A.,Montpellier University | Garrido C.J.,Instituto Andaluz Of Ciencias Of La Tierra Iact | Lopez Sanchez-Vizcaino V.,University of Jaen
Earth and Planetary Science Letters | Year: 2012

We have inferred the deformation mechanisms of antigorite by high-resolution EBSD mapping of samples from Cerro del Almirez ultramafic massif (Betic Cordillera, SE Spain). Textural relations and phase diagram calculations constrain the foliation development conditions to the subduction prograde path at up to 600-630 °C and 1.6-1.9. GPa. Deformation was followed by static annealing of antigorite at ca. 680 °C. The Crystal Preferred Orientation (CPO) of antigorite is characterised by a strong alignment of (001) poles normal to the foliation plane and a weaker, but clear, parallelism between [100] axes and the macroscopic lineation defined by the elongation of magnetite aggregates. Analysis of misorientations across subgrains shows predominance of [010] rotation axis, consistent with activation of the [100](001) slip system. However, tilt subgrain boundaries subparallel to (100), probably formed by edge dislocations of this system, are subsidiary. Most subgrain boundaries are subparallel to (001) planes. They are interpreted as (001) twins wherein continuing viscoplastic deformation resulted in a slight increase of the misorientation between the twins. Modelling of the evolution of the antigorite CPO using a lower bound approach and considering different deformation regimes and sets of basal and non-basal slip systems has shown that intensities of [100] and [010] maxima reflect the relative strength of the antigorite [100](001) and [010](001) systems. Activation of other basal or non-basal slip systems does not change significantly the CPO patterns, but results in less concentrated CPO. 3D transpression models better reproduce the CPO of natural antigorite serpentinites. We propose that the widespread occurrence of strong CPO in high-pressure antigorite serpentinite is consistent with deformation by dislocation creep with dominant glide on [hk0](001), together with the activation of twinning, implying that a power law rheology would better account for the mechanical behaviour of antigorite serpentinite deep in the subduction channel and mantle wedge. © 2012 Elsevier B.V. Source

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