Pedro Pablo Gil Crespo

University of the Basque Country

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A. Pesquera

University of the Basque Country

Encarnación Roda-Robles

University of the Basque Country

J. Torres-Ruíz

Universidad de Granada

Idoia Garate-Olave

University of the Basque Country

Francisco Velasco

Universidad de Murcia

William B. Simmons

Maine State Museum

Alexandre Lima

Centro de Estudos em Geografia e Ordenamento do Territorio

Jon Errandonea-Martin

University of the Basque Country

Alexander U. Falster

Maine State Museum

Romeu Vieira

Universidade do Porto

Cooperative Institutions

University of the Basque Country

Universidad de Granada

Consejo Superior de Investigaciones Científicas

Ente Vasco de la Energía

Centre National de la Recherche Scientifique

Université Toulouse III - Paul Sabatier

Instituto Andaluz de Ciencias de la Tierra

University of New Orleans

Universidade do Porto

Universitat de Barcelona

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Tourmaline as a petrogenetic monitor of the origin and evolution of the Berry-Havey pegmatite (Maine, U.S.A.)

American Mineralogist (2014)

Encarnación Roda-Robles William B. Simmons A. Pesquera Pedro Pablo Gil Crespo James W. Nizamoff

The Berry-Havey pegmatite (Oxford pegmatite field, Androscoggin County, Maine, U.S.A.), enriched in Li, F, B, Be, and P, is intruded in hornblende-rich amphibolite, with minor biotite or diopside. The pegmatite has a complex internal structure, with four texturally and compositionally different zones that show an increasing degree of evolution inward: wall zone, intermediate zone, core margin, and core zone. The main minerals are quartz, feldspars, Al-micas, tourmaline, with minor Fe-micas, garnet, beryl, amblygonite-montebrasite, Fe-Mn phosphates, and apatite. Tourmaline is present in all zones of the pegmatite, showing different textures: black anhedral crystals in the wall and intermediate zones; black prisms of up to 40 cm in length in the intermediate zone; black tapered prisms, surrounded by a pseudo-graphic intergrowth of quartz or albite with black ± green/bluish tourmaline, and constituting a continuous layer under the core zone; multicolored and "watermelon" zoned crystals in the core zone; and gemmy deep green and color-zoned "watermelon" tourmaline prisms, up to 15 cm length, inside the pockets. A complete chemical evolution from Mg-rich schorl in the wall zone to elbaite with an important deprotonation in the pockets inside the core zone is observed. The most plausible exchange vectors for this chemical evolution are FeMg-1, YAlWO[YR2+W(OH)]-1 and Al[X]X(R2+Na)-1 (where R2+ = Fe2++Mg2++Mn2++Zn2+), for the tourmalines from the wall and intermediate zones. In the core margin, tourmaline composition evolves from schorl toward Li-rich species through the substitution (YAlYLiYR2+-2). Later, during the crystallization of the core zone, this exchange vector combined with the substitution ([X] YAl0.5XNa-1YLi-0.5). Finally, the gemmy tourmalines from the pockets show a deprotonation related to the exchange vector YAlWO2YLi-1W(OH)-2 and may be classified as darrellhenryite. These substitutions may reflect an increase in oxygen fugacity and a decrease in Li and F related to the crystallization of lepidolite and amblygonite-montebrasite in the core zone adjacent to or within the pockets. The crystallization of these minerals would reduce the availability of Li and F for the very latest tourmaline crystals, growing inside the pockets, where the deprotonation becomes important. Chemical and textural variation in tourmaline is consistent with a fractional crystallization process for the internal evolution of the Berry-Havey pegmatite. Crystallization of the tourmaline layer under the core zone may be related to the exsolution of the fluid phase implied in the formation of pockets.

Tourmaline

Pegmatite

Hornblende

10.2138/am-2015-4829

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Citations (33)

Preliminary results of Unidirectional Solidification Textures recorded by the aplite-pegmatites from Tres Arroyos (Badajoz, Spain) and the story they tell

Idoia Garate-Olave Encarnación Roda-Robles Pedro Pablo Gil Crespo Jon Errandonea-Martin A. Pesquera

<p>One of the most characteristic attributes of pegmatitic rocks is their anisotropic fabric with a great variety of textures, including not only a broad range of crystal sizes, but also different types of unidirectional crystal growths such as the so-called Unidirectional Solidification Textures (UST). In the Tres Arroyos Pegmatite Field (Central Iberian Zone of the Iberian Massif), apart from comb-textures, the alternation of aplitic and pegmatitic layers (with variable modal proportions) parallel to the contacts with the host rocks occur commonly all across the pegmatitic dykes. The origin of the layering in these bodies is still enigmatic.</p><p>In the case of Tres Arroyos, the strong undercooling of the system could be produced by a combination of different factors, including a sudden drop of pressure favoring the exsolution of a fluxing components-bearing aqueous fluid from the pegmatitic melt, and a marked temperature decrease of the pegmatitic melt due to its intrusion into significantly colder host rocks. The reduced thickness of the studied dykes (average of 2 m) would promote to the development of nonequilibrium textures along the entire width of the dykes. The variation of the crystal size (&#8776;2-3 orders of magnitude) through different layers constituting the dykes reflects changes in the nucleation density and crystal growth rate during crystallization. The occurrence of dykes with several alternating thin pegmatitic and aplitic layers could be the result of cyclical changes induced by the competition between crystal growth rate and nucleation rate. The simplest layering patterns observed in Tres Arroyos, with alternating quartz-rich and plagioclase-rich bands, or alternating lepidolite-rich and albite-rich layers, could be explained by a diffusion-controlled oscillatory nucleation model, whereas the understanding of more complex layering patterns would need a more comprehensive study.</p>

Pegmatite

Supercooling

Layering

Texture (cosmology)

10.5194/egusphere-egu22-5329

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Geotermometria de inclusiones fluidas de los yacimientos de siderita de Bilbao: Cretácico Inferior, cuenca Vasco-Cantábrica (España)

Boletín de la Sociedad Española de Mineralogía (1993)

Laura Álvarez-Dieguez Francisco Velasco Pedro Pablo Gil Crespo

Se presentan las caracteristicas microtermometricas de los minerales relacionados con los yacimientos masivos de siderita del distrito de Bilbao, encajados en carbonatos de edad Aptiense Inferior (Gargasiense), situados en la cuenca Vasco-Cantabrica (Norte de Espana). Estos yacimientos exhiben caracteristicas morfologicas, paragneticas y texturales muy similares, lo que permite generalizar acera del origen y condiciones de deposito de estos minerales. El estudio de las inclusiones primarias en diferentes minerales tanto de la minerales tanto de mineralizacion (siderita, cuarzo y calcita tardia) como del encajante (calcita y celestita) permite llegar a las siguientes conclusiones: (1) todas las inclusiones observadas son acuosas y bifasicas; (2) la siderita de la fase principal de deposito presenta temperaturas de homogeneizacion entre 160 y 250oC y salinidades de moderadas a altas; (3) la ganga acompanante presenta salinidades mas bajas y temperaturas decrecientes; (4) las inclusiones de celestita y calcita de las cavidades estromatacticas de las calizas encajantes precipitaron en condiciones de moderada y alta salinidad, alcanzando al menos los 200oC. La naturaleza de los fluidos hidrotermales investigados senala que las condiciones de formacion de estas mineralizaciones implican la mezcla de dos salmueras, una de tipo profundo, caliente por grado geotermico, ascendente utilizando fracturas, y otra, mas superficial, integrada por acuiferos de aguas principalmente meteoricas. Este modelo genetico implica que la solucion mas profunda fue capaz de lixiviar el hierro de las formaciones infrayacentes e indica que el deposito tuvo lugar durante la mezcla de las dos soluciones hidrotermales.

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Tourmalinites and Sn-Li mineralization in the Valdeflores area (C�ceres, Spain)

Mineralogy and Petrology (1996)

J. Torres-Ruíz A. Pesquera Pedro Pablo Gil Crespo José M. Casas

Tourmaline

Cassiterite

Batholith

Greisen

Arsenopyrite

Muscovite

Pegmatite

Fluorite

Wolframite

Topaz

Paragenesis

10.1007/bf01162604

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Citations (8)

Tourmaline from the rare-element Pinilla pegmatite, (Central Iberian Zone, Zamora, Spain): chemical variation and implications for pegmatitic evolution

Mineralogy and Petrology (2004)

Encarnación Roda-Robles A. Pesquera F. Fontán Pedro Pablo Gil Crespo J. Torres-Ruíz

Pegmatite

Tourmaline

Leucogranite

10.1007/s00710-004-0042-8

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Citations (27)

Geologia bizirik. GeoBizirik.org

Servicio Editorial de la Universidad del País Vasco/Euskal Herriko Unibertsitatearen Argitalpen Zerbitzua eBooks (2011)

Ainhoa Alonso Olazabal Estibaliz Apellaniz A. Apraiz Arantza Aranburu Artano José Javier Arostegi García

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Mississippi Valley-Type, Sedex, and Iron Deposits in Lower Cretaceous Rocks of the Basque-Cantabrian Basin, Northern Spain

Springer eBooks (1994)

Francisco Velasco José Miguel Herrero Rubio Pedro Pablo Gil Crespo Leyre Pérez‐Álvarez Iñaki Yusta Arnal

Ankerite

Gangue

Ore genesis

10.1007/978-3-662-03054-7_15

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Citations (33)

TOURCOMP: A program for estimating end-member proportions in tourmalines

Mineralogical Magazine (2008)

A. Pesquera Felipe Pascual Torres Pedro Pablo Gil Crespo J. Torres-Ruíz

Abstract A Visual Basic program (TOURCOMP) has been written to recast the tourmaline composition into end-member components from electron microprobe data or more complete tourmaline analyses. TOURCOMP is a program based on a linear algebraic model that directly calculates the end-member proportions of tourmalines from their structural formulae. The program is developed for IBM-compatible personal computers running under the Windows™ operating system. The source code has been also translated and compiled in order to run on an Apple computer. Analytical problems, uncertainties concerning site occupancies, and the normalization procedure to determine the structural formula are the main error sources. However, the method of recalculating tourmaline end-members presented in this paper is considered to provide reasonably good results, bearing in mind the chemical complexity of tourmaline.

Tourmaline

Normalization

IBM

Computer program

Microprobe

10.1180/minmag.2008.072.5.1021

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Citations (6)

X-ray diffraction, infrared and Mössbauer studies of Fe-rich carbonates

European Journal of Mineralogy (1992)

Pedro Pablo Gil Crespo A. Pesquera Francisco Velasco

10.1127/ejm/4/3/0521