Person: Bustillo Revuelta, Manuel
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First Name
Manuel
Last Name
Bustillo Revuelta
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Department
Mineralogía y Petrología
Area
Petrología y Geoquímica
Identifiers
4 results
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Item Evolución geoquímica del estroncio en los procesos de dolomitización: Aplicación a las dolomías del Cretácico Inferior de la zona oeste de Cantabria(Boletín geológico y minero, 1986) Bustillo Revuelta, Manuel; Fort González, RafaelEn este trabajo se propone un modelo basado en la evolución geoquímíca del estroncio durante los procesos de dolomitización. Las dolomías penecontemporáneas incluyen dos estadios de formación: a) Sedimentación de lodos aragoníticos, y b) dolomitización por aguas de derivación marina. Por el contrario, las dolomías originadas por procesos diagenéticos tardíos incluyen: a) Sedimentación de lodos aragoníticos; b) estabilización diagenética del aragonito a calcita de bajo contenido en magnesio, y e) dolomitización por mezcla de aguas de origen marino y meteórico. Cada uno de estos estadios produce cambios en los contenidos en estroncio. Así, el modelo propuesto muestra que las dolomías penecontemporáneas están enriquecidas en estroncio (324 p.p.m.) en comparación con las dolomías diagenéticas (65 p.p.m.). Posteriormente, este modelo se aplica al estudio 'de las dolomías aptienses del norte de España (zona este de Cantabria). Los dos procesos de dolomitización considerados y sus contenidos en estroncio se comparan con los resultados obtenidos en las dolomías estudiadas. Esta comparación pone de manifiesto que su origen está probablemente relacionado con procesos de dolomitización diagenéticos tardíos. Esta conclusión concuerda con los estudios petrológicos y sedimentológicos llevados a cabo en estas dolomías.Item Origin of the Rubian carbonate-hosted magnesite deposit, Galicia, NW Spain: mineralogical, REE, fluid inclusion and isotope evidence)(Mineralium deposita, 2006) Kilias, Stephanos P.; Pozo, M.; Bustillo Revuelta, Manuel; Stamatakis, Michael G.; Calvo Sorando, José PedroThe Rubian magnesite deposit (West Asturian—Leonese Zone, Iberian Variscan belt) is hosted by a 100-m-thick folded and metamorphosed Lower Cambrian carbonate/siliciclastic metasedimentary sequence—the Cándana Limestone Formation. It comprises upper (20-m thickness) and lower (17-m thickness) lens-shaped ore bodies separated by 55 m of slates and micaceous schists. The main (lower) magnesite ore body comprises a package of magnesite beds with dolomite-rich intercalations, sandwiched between slates and micaceous schists. In the upper ore body, the magnesite beds are thinner (centimetre scale mainly) and occur between slate beds. Mafic dolerite dykes intrude the mineralisation. The mineralisation passes eastwards into sequence of bedded dolostone (Buxan) and laminated to banded calcitic marble (Mao). These show significant Variscan extensional shearing or fold-related deformation, whereas neither Rubian dolomite nor magnesite show evidence of tectonic disturbance. This suggests that the dolomitisation and magnesite formation postdate the main Variscan deformation. In addition, the morphology of magnesite crystals and primary fluid inclusions indicate that magnesite is a neoformed hydrothermal mineral. Magnesite contains irregularly distributed dolomite inclusions (<50 μm) and these are interpreted as relics of a metasomatically replaced dolostone precursor. The total rare earth element (REE) contents of magnesite are verysimilar to those of Buxan dolostone but are depleted in light rare earth elements (LREE); heavy rare earth element concentrations are comparable. However, magnesite REE chondrite normalised profiles lack any characteristic anomaly indicative of marine environment. Compared with Mao calcite, magnesite is distinct in terms of both REE concentrations and patterns. Fluid inclusion studies show that the mineralising fluids were MgCl2–NaCl–CaCl2–H2O aqueous brines exhibiting highly variable salinities (3.3 to 29.5 wt.% salts). This may be the result of a combination of fluid mixing, migration of pulses of variable-salinity brines and/or local dissolution and replacement processes of the host dolostone. Fluid inclusion data and comparison with other N Iberian dolostone-hosted metasomatic deposits suggest that Rubian magnesite probably formed at temperatures between 160 and 200°C. This corresponds, at hydrostatic pressure (500 bar), to a depth of formation of ∼5 km. Mineralisation- related Rubian dolomite yields δ18O values (δ18O: 12.0–15.4‰, mean: 14.4±1.1‰) depleted by around 5‰ compared with barren Buxan dolomite (δ18O: 17.1– 20.2‰, mean: 19.4±1.0‰). This was interpreted to reflect an influx of 18O-depleted waters accompanied by a temperature increase in a fluid-dominated system. Overlapping calculated δ18Ofluid values (∼+5‰ at 200°C) for fluids in equilibrium with Rubian dolomite and magnesite show that they were formed by the same hydrothermal system at different temperatures. In terms of δ13C values, Rubian dolomite (δ13C: −1.4 to 1.9‰, mean: 0.4±1.3‰) and magnesite (δ13C: −2.3 to 2.4‰, mean: 0.60±1.0‰) generally exhibit more negative δ13C values compared with Buxan dolomite (δ13C: −0.2 to 1.9‰, mean: 0.8± 0.6‰) and Mao calcite (δ13C: −0.3 to 1.5‰, mean: 0.6± 0.6‰), indicating progressive odification to lower δ13C values through interaction with hydrothermal fluids. 87Sr/86Sr ratios, calculated at 290 Ma, vary from 0.70849 to 0.70976 for the Mao calcite and from 0.70538 to 0.70880 for the Buxan dolostone. The 87Sr/86Sr ratios in Rubian magnesite are more radiogenic and range from 0.71123 to 0.71494. The combined δ18O–δ13C and 87Sr/86Sr data indicate that the magnesite-related fluids were modified basinal brines that have reacted and equilibrated with intercalated siliciclastic rocks. Magnesite formation is genetically linked to regional hydrothermal dolomitisation associated with lithospheric delamination, late-Variscan high heat flow and extensional tectonics in the NW Iberian Belt. A comparison with genetic models for the Puebla de Lillo talc deposits suggests that the formation of hydrothermal replacive magnesite at Rubian resulted from a metasomatic column with magnesite forming at higher fluid/rock ratios than dolomite. In this study, magnesite generation took place via the local reaction of hydrothermal dolostone with the same hydrothermal fluids in very high permeability zones at high fluid/rock ratios (e.g. faults). It was also possibly aided by additional heat from intrusive dykes or sub-cropping igneous bodies. This would locally raise isotherms enabling a transition from the dolomite stability field to that of magnesite.Item Génesis del yacimiento de magnesita de Rubián (Lugo): nueva interpretación basada en datos petrológicos y geoquímicos(Geotemas, 2004) Pozo, M.; Calvo Sorando, José Pedro; Bustillo Revuelta, Manuel; Kilias, Stephanos P.; Stamatakis, Michael G.The Rubian sparry magnesite (Galicia, NW Spain) is hosted in Lower Cambrian carbonate rocks (Caliza de Cándana Fm.) included in a strongly deformed and faulted thick succession of siliciclastic and carbonate rocks. The magnesite shows massive and banded fabrics. δ18 O SMOW values range from 13,32‰ to 17,22‰ whilst δ13C PDB values range from -2,32‰ to 2,37‰. Radiogenic strontium isotopes from magnesite exceed 0.711435, considerably higher than those commonly reported for Cambrian marine carbonates. Similarly, REE patterns do not show any sort of anomaly indicative of marine environment. Fluid inclusions can be interpreted as a result of NaCI-CaCI2(±MgCI2) mineralising brines, probably by mixing of two CaCI2 -rich fluids of contrasted salinity, and allow to conclude that magnesite formed at a minimum temperature of 170±15QC. Accordingly, a hydrothermal/metasomatic replacement of preexisting dolostone is proposed as a more reliable process to explain the origin of the sparry magnesite of Rubian, which is in contrast with previous interpretations that supported a syn-diagenetic model for the formation of the deposit.Item Neoformaciones y reemplazamientos en depósitos palustres de la Unidad Intermedia (NE de la Cuenca de Madrid)(Geotemas, 2004) Pérez Jiménez, José Luis; Bustillo Revuelta, Manuel; Alonso Zarza, Ana MaríaThe NE zone of the Madrid Basin contains palustrine deposits of the Miocene Intermediate Unit which have undergone silicification processes. These processes are conditioned by the type of palustrine deposit within they developed and occur at specific stratigraphic positions in the basin. In this paper we analyze three different sectors. In the Yesares section silicification produced quartz and took place in gypsum deposits which contain bioturbation channels that favoured silica fixation. In the Brihuega area silicification on bioturbated palustrine micrites also produced quartz. Both silicifications appear at the top of unit or sequence of the Intermediate Unit. In the Jadraque section the silicification of the micrites and dolomicrites was controlled by the presence of biosiliceous marls and sepiolite. This silicification was consequence of early diagenesis.