Gahnite, chrysoberyl and beryl co-occurrence as accessory minerals in a highly evolved peraluminous pluton: The Belvís de Monroy leucogranite (Cáceres, Spain)

Merino, Enrique; Villaseca, Carlos; García, David Orejana; Jeffries, Teresa

doi:10.1016/j.lithos.2013.08.004

Cited by 42 publications

(43 citation statements)

References 62 publications

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“…The most evolved leucogranites are interpreted as evolving in a deep chamber, from a source compositionally similar to other less evolved exposed granites, rather than evolving through fractionation of the exposed, less evolved granites, similar to the G3-G4 and G5 granites. The potential to reach shallow emplacement levels is aided by high concentrations of volatile and fluxing components (Merino et al, 2013).…”

Section: Accepted M Manuscriptmentioning

confidence: 99%

The petrogenesis of the Early Permian Variscan granites of the Cornubian Batholith: Lower plate post-collisional peraluminous magmatism in the Rhenohercynian Zone of SW England

Simons

Shail

Andersen

2016

Lithos

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The Early Permian Cornubian Batholith was generated during an extensional regime following Variscan convergence within the Rhenohercynian Zone of SW England. Its component granites can be classified, using mineralogical, textural and geochemical criteria, into five main types, all of which are peraluminous (A/CNK >1.1): G1 (two-mica), G2 (muscovite), G3 (biotite), G4 (tourmaline) and G5 (topaz). G1 granites formed through up to 20% muscovite and minor biotite dehydration melting of a metagreywacke source at moderate temperatures and pressures (731-806°C, >5 kbar). Younger G3 granites formed through higher temperature, lower pressure (768-847°C, <4 kbar) biotite-dominated melting of a similar source. Partial melting was strongly influenced by the progressive lower-mid crustal emplacement of mafic igneous rocks during post-Variscan extension and a minor (<5-10%) mantle-derived component in the granites is possible. Two distinct fractionation series, G1-G2 and G3-G4, are defined using whole rock geochemical and mineral chemical data.Variations in the major elements, Ba, Sr and Rb indicate that G1 and G3 granites underwent 15-30% fractionation of an assemblage dominated by plagioclase, alkali feldspar and biotite to form, more evolved G2 and G4 granites respectively. Decreasing whole rock abundances of Zr, Th and REE support fractionation of zircon, monazite, apatite and allanite. Subsolidus alteration in G2 and G4 granites is indicated by non-primary muscovite and tourmaline and modification of major and trace element trends for G3-G4 granites, particularly for P 2 O 5 and Rb. Topaz (G5) granites show low Zr, REE and extreme enrichment in Rb (up to 1530 ppm) and Nb (79 ppm) that cannot be related in a straightforward manner to continued differentiation of the G1-G2 or G3-G4 series. Instead, they are considered to represent partial melting, mediated by granulite facies fluids, of a biotite-rich restite following extraction of

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Section: Accepted M Manuscriptmentioning

confidence: 99%

The petrogenesis of the Early Permian Variscan granites of the Cornubian Batholith: Lower plate post-collisional peraluminous magmatism in the Rhenohercynian Zone of SW England

Simons

Shail

Andersen

2016

Lithos

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“…Line 001, 3 -EZR9B-C7-T1 Line 004, 4 -EZR9B-C7-T1 Line 006, 5 -EZR17B-C6-T1 Line 005, 6 -EZR17B-C6-T1 Line 006, 7 -EZR17C-C7-T1 Line 006, 8 -PCH2B-C7-T1 Line 002, 9 -PCH2B-C7-T1 Line 004, 10 -PCH2D-BSD-6-T2 Line 003, 11 -PCH2D-ULC-P2, 12 -PCH2F-C8-T1 Line 004, 13 -PCH2F-C8-T2 Line 001, PCH6A C10 CrB T1 Line 001, PCH6A Abv C2 CrA T1 Line 003 1981; Černý and Hawthorne 1982;Batchelor and Kinnaird 1984;Černý et al 1985;Spry and Scott 1986b;Morris et al 1997;Neiva and Champness 1997;Szuszkiewicz and Łobos 2004;Soares et al 2007Soares et al , 2009Soares et al , 2014Neiva 2013;Merino et al 2010Merino et al , 2013; Table 2). Even though gahnite is a much rarer accessory mineral compared to other accessory pegmatite phases, it does occur in various types of evolved granitic pegmatites, including members of the rare-element class and Li subclass (beryl -columbite-phosphate subtype and complex-type; e.g., Černý et al 1985) belonging to the LCT family (based on the classification of Černý and Ercit 2005;Černý et al 2012), some of which are hosts to economic raremetal (Li, Be, Ta, Nb) mineralization (Table 2).…”

Section: Occurrence Of Gahnite In Granitic Pegmatitesmentioning

confidence: 99%

“…Of the factors that control mineral crystallization, in addition to low sulfur fugacity, the formation of gahnite in granitic pegmatites is thought to be favored by an excess of Al in the melt, a low amount of other Fe-bearing minerals crystallizing in the melt, and the availability of Zn at the end of the fractional crystallization process of parent granitic melts (e.g., Černý et al 1985). In pegmatites gahnite commonly occurs spatially associated with other aluminous minerals, principally garnet, muscovite, beryl, tourmaline, and nigerite, and rarely with sphalerite (e.g., Eskola 1914;Pehrman 1948;Černý and Hawthorne 1982) and chrysoberyl (e.g., Merino et al 2013). In the Pala Chief and Elizabeth R aplites gahnite occurs in association with plagioclase, quartz, muscovite, garnet, and schorl, and sphalerite was not found in the studied samples.…”

Section: Factors Controlling the Formation Of Gahnite In Granitic Pegmentioning

confidence: 99%

“…Reflecting the lowest degree of fractionation among all the pegmatites for which gahnite data are available, the lowest Zn contents (25.6 wt.% ZnO) in gahnite are found in a pegmatite from the reversely-zoned Belvís de Monroy pluton, Spain (Merino et al 2010(Merino et al , 2013, the Pulsifer and Lord Hill pegmatites, Maine (Spry and Scott 1986b) and an LCT pegmatite from the Siedlimowice area, Poland (Szuszkiewicz and Łobos 2004;Fig. 5b).…”

Section: Comparison With Pegmatite Gahnite Worldwide and Relative Degmentioning

confidence: 99%

“…In analyzing the chemical composition of pegmatite dikes and their minerals, Zn is often not included in the list of elements analyzed for as it is typically not of economic importance in this kind of rock nor is gahnite considered a classic petrogenetic Editorial handling: L. Danyushevsky indicator. Therefore, the information currently available for gahnite in granitic pegmatite dikes is scarce (e.g., Černý and Hawthorne 1982;Batchelor and Kinnaird 1984;Neiva and Champness 1997;Szuszkiewicz and Łobos 2004;Soares et al 2007;Merino et al 2013;Neiva 2013) compared to other pegmatite minerals that are economically important or typically used as petrogenetic indicators (i.e., muscovite, feldspars, tourmaline, beryl, Li-bearing minerals, Ta-Nb oxides, etc. ).…”

Section: Introductionmentioning

confidence: 99%

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Melt evolution in felsic dikes inferred from the composition of gahnite in two new occurrences, Pala Chief and Elizabeth R composite dikes, California

2016

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We report the occurrence and composition of gahnite ([Zn,Fe,Mg,Mn]Al 2 O 4 ) in aplites of the Pala Chief and Elizabeth R layered pegmatite-aplite dikes, Pala District, California, and the significance for felsic melt evolution. The aplite is characterized by alternating bands of white, finegrained plagioclase + quartz + muscovite +/− black tourmaline and thin laminations defined by concentrations of reddishbrown garnet (Bline rock^). Accessory gahnite occurs as extremely fine-grained (50-250 μm) green to bluish-green crystals. Gahnite compositions in both occurrences are similar and defined by end-member ranges Ghn 83.5-90.9 Hc 8.7-15 Spl 0-1.4 . Zinc contents in gahnite are high (36.7-39.5 wt.% ZnO for Pala Chief, 37.2-40.2 wt.% ZnO for Elizabeth R), the MgO and MnO contents are negligible (< 0.7 wt.%), and Fe is the main substitution present (< 6.9 wt.% FeO). Gahnite is chemically zoned and characterized by higher Zn (< 2 wt.% ZnO) and lower Fe, Mg, and Mn contents in rims compared to cores, which shows the substitution mechanism, and reflects fast growth during melt evolution via fractional crystallization followed by fast cooling. Compositional variations are greater within individual crystals than among crystals and between laminations, which indicate a homogeneous melt at the aplite scale. Compared with the composition of gahnite from pegmatites worldwide, the studied gahnite reflects a moderate degree of melt evolution. This study confirms the incompatible character of Zn in evolving pegmatite-aplite melts and shows the usefulness of gahnite as a petrogenetic indicator. Because gahnite is a resistant mineral, surficial findings of gahnite with very low Mg contents and Zn contents similar or higher than those measured here may indicate a source of granitic pegmatite-aplite.

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Petrographic and geochemical study of the stone warrior stelae from central Iberia: Linking the geological record and archaeological heritage

Martínez¹,

Moreno

Chapa

et al. 2019

Geoarchaeology

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Six warrior stelae from central Iberia (Toledo, Spain) were studied using different geological techniques to discriminate their potential source materials and evaluate the displacement suffered from the quarry sites to their final location. The similar petrographic and geochemical features of the stelae, when compared with other lithological equivalents cropping out in the surrounding area, suggest that most raw materials were quarried less than 10 km from the finds. These materials mainly belong to a set of metasedimentary rocks from the Schist–Graywacke Complex and other Ordovician brownish sandstones, mostly found in the vicinity of the stelae sites. In contrast, the Talavera de la Reina stele, previously used as a statue‐menhir, was engraved on a leucogranite, geochemically similar to some plutonic units in the Navamorcuende area, in the southernmost region of the Spanish Central System batholith. The fact that all stelae and the proposed geological sources were located close to ancient tracks suggests that the raw materials were quarried in connection with these natural routes. The stelae may, therefore, have been landmarks or reference points that signaled transit passages used for trade or grazing, in the framework of continuous territorial expansion during the Late Bronze Age and Early Iron Age.

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Gahnite, chrysoberyl and beryl co-occurrence as accessory minerals in a highly evolved peraluminous pluton: The Belvís de Monroy leucogranite (Cáceres, Spain)

Cited by 42 publications

References 62 publications

The petrogenesis of the Early Permian Variscan granites of the Cornubian Batholith: Lower plate post-collisional peraluminous magmatism in the Rhenohercynian Zone of SW England

The petrogenesis of the Early Permian Variscan granites of the Cornubian Batholith: Lower plate post-collisional peraluminous magmatism in the Rhenohercynian Zone of SW England

Melt evolution in felsic dikes inferred from the composition of gahnite in two new occurrences, Pala Chief and Elizabeth R composite dikes, California

Petrographic and geochemical study of the stone warrior stelae from central Iberia: Linking the geological record and archaeological heritage

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