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3 pages, 203 KiB

Open AccessEditorial

Editorial for the Special Issue “Petrology and Mineralogy of Pegmatite Deposits”

by Axel Müller and Encarnación Roda-Robles

Minerals 2023, 13(6), 818; https://doi.org/10.3390/min13060818 - 15 Jun 2023

Viewed by 1353

Abstract

This Special Issue of Minerals, section Mineral Deposits, on the topic of “Petrology and Mineralogy of Pegmatite Deposits”, was inspired by the currently growing scientific and economic interest in pegmatites [...] Full article

(This article belongs to the Special Issue Petrology and Mineralogy of Pegmatite Deposits)

Research

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31 pages, 31923 KiB

Open AccessArticle

Calibrating a Handheld LIBS for Li Exploration in the Barroso–Alvão Aplite-Pegmatite Field, Northern Portugal: Textural Precautions and Procedures When Analyzing Spodumene and Petalite

by Filipa Dias, Ricardo Ribeiro, Filipe Gonçalves, Alexandre Lima, Encarnación Roda-Robles and Tânia Martins

Minerals 2023, 13(4), 470; https://doi.org/10.3390/min13040470 - 26 Mar 2023

Cited by 10 | Viewed by 2627

Abstract

In pegmatites containing abundant petalite and spodumene, such as those from the Barroso–Alvão (BA) aplite-pegmatite field, calibrating a portable laser-induced breakdown spectroscopy (pLIBS) equipment to identify and analyze these minerals may be challenging. Forty-nine samples of spodumene, petalite and spodumene + quartz were [...] Read more.

In pegmatites containing abundant petalite and spodumene, such as those from the Barroso–Alvão (BA) aplite-pegmatite field, calibrating a portable laser-induced breakdown spectroscopy (pLIBS) equipment to identify and analyze these minerals may be challenging. Forty-nine samples of spodumene, petalite and spodumene + quartz were collected from 22 aplite-pegmatites from the BA field and sent for inductively coupled plasma-mass spectroscopy analysis. One calibration for both spodumene and petalite has been proven to be impossible since almost all the LIBS intensity ratios, including for Li, overlapped on both minerals. Thus, three calibrations were developed: one qualitative to distinguish both minerals and two more quantitative, specifically made for each mineral. The first LIBS calibration only has Fe since it is the sole element with intensity ratios different enough to distinguish both minerals. Eleven calibration lines were created: Li, Al, Si, Be, Na, P, K, Mn, Fe, Rb and Cs; however, only the Li, Al, and Si have consistent errors below 20%. Thin sections were produced and observed with optical microscopy and cathodoluminescence (CL) to control the purity and mineral paragenesis of the samples. The petalite pellets were also controlled with cold CL since petalite crystals often present fine spodumene and quartz inclusions. Full article

(This article belongs to the Special Issue Petrology and Mineralogy of Pegmatite Deposits)

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16 pages, 4590 KiB

Open AccessArticle

Petrophysical Database for European Pegmatite Exploration—EuroPeg

by Claudia Haase and Claudia M. Pohl

Minerals 2022, 12(12), 1498; https://doi.org/10.3390/min12121498 - 24 Nov 2022

Cited by 3 | Viewed by 3092

Abstract

Granitic pegmatites contain natural concentrations of a variety of raw materials invaluable for modern technologies and a green and sustainable society. The most abundant ones are silicon for high-purity quartz applications, and indispensable lithium for today’s batteries. However, the exploration of these target [...] Read more.

Granitic pegmatites contain natural concentrations of a variety of raw materials invaluable for modern technologies and a green and sustainable society. The most abundant ones are silicon for high-purity quartz applications, and indispensable lithium for today’s batteries. However, the exploration of these target materials in Europe is underdeveloped, causing high dependencies on non-European supply chains. The European Commission Horizon 2020 project GREENPEG (GA no. 869274) is addressing the exploration of buried, small-scale pegmatite deposits in Europe through the development of innovative new exploration toolsets. One component of these toolsets is petrophysical data of pegmatite ores and their wall rock. These data are essential to supplement and ground-truth non-invasive geophysical investigations and deposit modeling. Both important tools in mineral exploration can then be used in a more targeted and cost-effective way. Petrophysical parameters measured on drill core and field samples and acquired through geophysical borehole logging are compiled in the first database for European Pegmatite deposits: EuroPeg_PetroDB. Samples are supplemented with meta-information, and the database is comprehensively structured in an easy-to-use format. Supporting the initiative of FAIR data, EuroPeg is freely accessible on an open data repository. The sample content and petrophysical measurements are described, followed by the structure and usability of the database. Full article

(This article belongs to the Special Issue Petrology and Mineralogy of Pegmatite Deposits)

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21 pages, 10164 KiB

Open AccessArticle

Rare Element Enrichment in Lithium Pegmatite Exomorphic Halos and Implications for Exploration: Evidence from the Leinster Albite-Spodumene Pegmatite Belt, Southeast Ireland

by Renata Barros, David Kaeter, Julian F. Menuge, Thomas Fegan and John Harrop

Minerals 2022, 12(8), 981; https://doi.org/10.3390/min12080981 - 1 Aug 2022

Cited by 10 | Viewed by 6669

Abstract

Pegmatitic deposits of critical metals (e.g., Li, Ta, Be) are becoming increasingly significant, with growing interest in understanding metal enrichment processes and potential vectors to aid the discovery of new resources. In southeast Ireland, the Leinster pegmatite belt comprises several largely concealed Li-Cs-Ta [...] Read more.

Pegmatitic deposits of critical metals (e.g., Li, Ta, Be) are becoming increasingly significant, with growing interest in understanding metal enrichment processes and potential vectors to aid the discovery of new resources. In southeast Ireland, the Leinster pegmatite belt comprises several largely concealed Li-Cs-Ta albite-spodumene-type pegmatites. We carried out detailed mineralogical characterization and whole-rock geochemical analyses of six drill cores intersecting pegmatite bodies and their country rocks. Exomorphic halos 2–6 m thick, enriched in Li, Rb, Be, B, Cs, Sn and Ta, are identified in both mica schists and granitic rocks adjacent to spodumene pegmatites. Metasomatism in wall rocks visible to the naked eye is restricted to a few tens of centimeters, suggesting country rock permeability plays a key role in the dispersion of these fluids. We propose that halos result from the discharge of rare element-rich residual fluids exsolved near the end of pegmatite crystallization. Halo geochemistry reflects the internal evolution of the crystallizing pegmatite system, with residual fluid rich in incompatible elements accumulated by geochemical fractionation (Be, B, Cs, Sn, Ta) and by auto-metasomatic resorption of spodumene and K-feldspar (Li, Rb). The possibility of identifying rare-element enrichment trends by analysis of bedrock, stream sediments and soils brings opportunities for mineral exploration strategies in Ireland and for similar albite-spodumene pegmatites worldwide. Full article

(This article belongs to the Special Issue Petrology and Mineralogy of Pegmatite Deposits)

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25 pages, 4122 KiB

Open AccessFeature PaperArticle

Lead Isotopes and the Sources of Granitic Magmas: The Sveconorwegian Granite and Pegmatite Province of Southern Norway

by Nanna Rosing-Schow, Tom Andersen and Axel Müller

Minerals 2022, 12(7), 878; https://doi.org/10.3390/min12070878 - 12 Jul 2022

Cited by 2 | Viewed by 2920

Abstract

Lead isotope analyses of K-feldspar from late Sveconorwegian (900–1000 Ma) granitic pegmatites and A-type, ferroan granitic intrusions in four different areas of southern Norway analyzed by laser-ablation inductively coupled plasma source mass spectrometry (LA-ICPMS) give compositions in the range ²⁰⁶Pb/²⁰⁴Pb [...] Read more.

Lead isotope analyses of K-feldspar from late Sveconorwegian (900–1000 Ma) granitic pegmatites and A-type, ferroan granitic intrusions in four different areas of southern Norway analyzed by laser-ablation inductively coupled plasma source mass spectrometry (LA-ICPMS) give compositions in the range ²⁰⁶Pb/²⁰⁴Pb = 16.637 to 17.555, ²⁰⁷Pb/²⁰⁴Pb = 15.445 to 15.534, ²⁰⁸Pb/²⁰⁴Pb = 36.317 to 37.459. These compositions broadly overlap with the initial compositions estimated from previously published solution TIMS whole-rock and feldspar Pb isotope analyses of late Sveconorwegian granitic plutons across the region, suggesting that magmas forming A-type granite plutons and granitic pegmatites have been derived from broadly similar source rocks, i.e., from a continental crust that initially formed in Palaeoproterozoic time (ca. 2.10–1.86 Ga), and subsequently underwent intracrustal partial melting, differentiation and rejuvenation via mafic underplating in Mesoproterozoic time. Full article

(This article belongs to the Special Issue Petrology and Mineralogy of Pegmatite Deposits)

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16 pages, 3078 KiB

Open AccessArticle

High-Density Upper Amphibolite/Granulite Facies Fluid Inclusions in Magmatic Garnet from the Koralpe Mountains (Eastern Alps, Austria)

by Martina Husar and Kurt Krenn

Minerals 2022, 12(7), 873; https://doi.org/10.3390/min12070873 - 11 Jul 2022

Cited by 1 | Viewed by 1793

Abstract

Fluid and solid inclusions in magmatic garnet from Permian pegmatites of the Koralpe Mountains were investigated. On the basis of MnO/(MnO + FeO) ratios, different degrees of melt fractionation during garnet growth were linked with fluid inclusion densities and chemistries. It is shown [...] Read more.

Fluid and solid inclusions in magmatic garnet from Permian pegmatites of the Koralpe Mountains were investigated. On the basis of MnO/(MnO + FeO) ratios, different degrees of melt fractionation during garnet growth were linked with fluid inclusion densities and chemistries. It is shown that garnet indicating low-melt fractionation trends contained primary CO₂ ± N₂-rich fluid inclusions of the highest densities, up to 1.15 g/cm³, compared to garnet samples of increased fractionation trends comprising CO₂-N₂-rich fluid inclusions with lower densities up to 0.85 g/cm³. This fluid composition is interpreted as a part of an unmixed CO₂ ± N₂-H₂O-rich fluid that was present during garnet crystallization. Variabilities in the nitrogen composition up to 40.83 mol% resulted from different degrees of partial melting of mica and plagioclase from the metapelitic host rock. Densities, fluid chemistries, and mineral chemical data enabled a continuous upward trend for garnet crystallization during anatexis from lower (ca. 25 km) up to middle crustal levels (12–15 km). Resulting amphibolite/granulite facies conditions of 7.6 kbar/700 °C for garnet crystallization in spodumene-free pegmatites were significantly higher than previously suggested for pegmatite formation in the Koralpe Mountains. Full article

(This article belongs to the Special Issue Petrology and Mineralogy of Pegmatite Deposits)

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30 pages, 10193 KiB

Open AccessArticle

Geological, Mineralogical and Geochemical Study of the Aquamarine-Bearing Yamrang Pegmatite, Eastern Nepal with Implications for Exploration Targeting

by Sushmita Bhandari, Kezhang Qin, Qifeng Zhou and Noreen J. Evans

Minerals 2022, 12(5), 564; https://doi.org/10.3390/min12050564 - 30 Apr 2022

Cited by 6 | Viewed by 3653

Abstract

The Yamrang Pegmatite in the Ikhabu Pegmatite Field, Eastern Nepal is Nepal’s primary source of aquamarine. This paper reports detailed mineralogy and whole rock granite and pegmatite geochemistry, and major and trace element data for alkali feldspar and muscovite in order to classify [...] Read more.

The Yamrang Pegmatite in the Ikhabu Pegmatite Field, Eastern Nepal is Nepal’s primary source of aquamarine. This paper reports detailed mineralogy and whole rock granite and pegmatite geochemistry, and major and trace element data for alkali feldspar and muscovite in order to classify the aquamarine-bearing Yamrang Pegmatite, elucidate beryl-saturation processes and evaluate potential geochemical exploration tools for beryl-pegmatites. Five internal mineralogical/textural zones were identified in the Yamrang Pegmatite; zone 1 (saccharoidal albite); zone 2 (blocky perthitic microcline); zone 3 (muscovite–microcline–quartz); zone 4 (beryl-quartz), and zone 5 (miarolitic cavities). Zones 1–4 represent the magmatic stage, while zone 5 formed during the hydrothermal stage of pegmatite genesis. Spectacular aquamarines are recovered from miarolitic zone 5, while beryl saturation is found in zones 3, 4, and 5. Based on beryllium (Be) content, Be partition among co-existing minerals at the magmatic stage is beryl > muscovite > tourmaline > alkali feldspar > quartz. In contrast, the sequence at the hydrothermal stage is beryl > muscovite > albite > tourmaline > quartz. The Be content in rock-forming minerals decreases from pegmatite margin to core, and tourmaline could have played a significant role in Be enrichment processes in the marginal pegmatite zone. High temperature, a low degree of fractionation, and the dominance of Be-compatible mineral phases such as muscovite, calcium-rich alkali feldspar and tourmaline resulted in beryl undersaturation in marginal zones. However, low temperature, high fractional crystallization, and low abundance of Be-compatible mineral phases resulted in beryl saturation in inner zones. The strongly peraluminous nature, low total REE content (<500 ppm), mineral assemblage of beryl, tourmaline, spessartine, columbite-tantalite, depletion of Ba, Nb, and enrichment of Pb, Rb, Cs in the primitive mantle normalized multi-element plots suggest that the beryl-bearing Yamrang Pegmatite corresponds to the LCT pegmatite family. Alkali feldspar with K/Rb values of 30–150, Rb ~3000 ppm, Cs >100 ppm, and muscovite, with K/Rb ranging 18–50, Rb ~6000 ppm, Cs > 500 ppm, and Ta > 65 ppm in inner zones (3–5), indicate that the Yamrang Pegmatite is an intermediate-fractionated, beryl-type rare-element (REL) pegmatite. It is probable that whole rock Be content of >10 ppm could be considered an exploration guide to beryl mineralization in the region. Full article

(This article belongs to the Special Issue Petrology and Mineralogy of Pegmatite Deposits)

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Review

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34 pages, 5928 KiB

Open AccessReview

Compositional Variations in Apatite and Petrogenetic Significance: Examples from Peraluminous Granites and Related Pegmatites and Hydrothermal Veins from the Central Iberian Zone (Spain and Portugal)

by Encarnación Roda-Robles, Pedro Pablo Gil-Crespo, Alfonso Pesquera, Alexandre Lima, Idoia Garate-Olave, Enrique Merino-Martínez, Joana Cardoso-Fernandes and Jon Errandonea-Martin

Minerals 2022, 12(11), 1401; https://doi.org/10.3390/min12111401 - 1 Nov 2022

Cited by 8 | Viewed by 3469

Abstract

Apatite can be used as an archive of processes occurring during the evolution of granitic magmas and as a pegmatite exploration tool. With this aim, a detailed compositional study of apatite was performed on different Variscan granites, pegmatites and quartz veins from the [...] Read more.

Apatite can be used as an archive of processes occurring during the evolution of granitic magmas and as a pegmatite exploration tool. With this aim, a detailed compositional study of apatite was performed on different Variscan granites, pegmatites and quartz veins from the Central Iberian Zone. Manganese in granitic apatite increases with increasing evolution degree. Such Mn increase would not be related to changes in the fO₂ during evolution but rather to a higher proportion of Mn in residual melts, joined to an increase in SiO₂ content and peraluminosity. In the case of pegmatitic apatite, the fO₂ and the polymerization degree of the melts seem not to have influenced the Mn and Fe contents but the higher availability of these transition elements and/or the lack of minerals competing for them. The subrounded Fe-Mn phosphate nodules, where apatite often occurs in P-rich pegmatites and P-rich quartz dykes, probably crystallized from a P-rich melt exsolved from the pegmatitic melt and where Fe, Mn and Cl would partition. The low Mn and Fe contents in the apatite from the quartz veins may be attributed either to the low availability of these elements in the late hydrothermal fluids derived from the granitic and pegmatitic melts, or to a high fO₂. The Rare Earth Elements, Sr and Y are the main trace elements of the studied apatites. The REE contents of apatite decrease with the evolution of their hosting rocks. The REE patterns show in general strong tetrad effects that are probably not related to the fluids’ activity in the system. On the contrary, the fluids likely drive the non-CHARAC behavior of apatite from the most evolved granitic and pegmatitic units. Low fO₂ conditions seem to be related to strong Eu anomalies observed for most of the apatites associated with different granitic units, barren and P-rich pegmatites. The positive Eu anomalies in some apatites from leucogranites and Li-rich pegmatites could reflect their early character, prior to the crystallization of feldspars. The increase in the Sr content in apatite from Li-rich pegmatites and B-P±F-rich leucogranites could be related to problems in accommodating this element in the albite structure, favoring its incorporation into apatite. The triangular plots ΣREE-Sr-Y and U–Th–Pb of apatites, as well as the Eu anomaly versus the TE_1,3 diagram, seem to be potentially good as petrogenetic indicators, mainly for pegmatites and, to a lesser extent, for granites from the CIZ. Full article

(This article belongs to the Special Issue Petrology and Mineralogy of Pegmatite Deposits)

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16 pages, 1160 KiB

Open AccessReview

The Li-Bearing Pegmatites from the Pampean Pegmatite Province, Argentina: Metallogenesis and Resources

by Miguel Ángel Galliski, María Florencia Márquez-Zavalía, Encarnación Roda-Robles and Albrecht von Quadt

Minerals 2022, 12(7), 841; https://doi.org/10.3390/min12070841 - 30 Jun 2022

Cited by 7 | Viewed by 4358

Abstract

The Li-bearing pegmatites of the Pampean Pegmatite Province (PPP) occur in a rare-element pegmatite belt developed mainly in the Lower Paleozoic age on the southwestern margin of Gondwana. The pegmatites show Li, Rb, Nb ≤ Ta, Be, P, B, Bi enrichment, and belong [...] Read more.

The Li-bearing pegmatites of the Pampean Pegmatite Province (PPP) occur in a rare-element pegmatite belt developed mainly in the Lower Paleozoic age on the southwestern margin of Gondwana. The pegmatites show Li, Rb, Nb ≤ Ta, Be, P, B, Bi enrichment, and belong to the Li-Cs-Ta (LCT) petrogenetic family, Rare-Element-Li (REL-Li) subclass; most of them are of complex type and spodumene subtype, some are of albite-spodumene type, and a few of petalite subtype. The origin of the pegmatites is attributed predominantly to fractionation of fertile S-type granitic melts produced by either fluid-absent or fluid-assisted anatexis of a thick pile of Gondwana-derived turbiditic sediments. Most of the pegmatites are orogenic (530–440 Ma) and developed during two overlapped collisional orogenies (Pampean and Famatinian); a few are postorogenic (~370 Ma), related to crustal contaminated A-type granites. The pegmatites were likely intruded in the hinterland, preferably in medium-grade metamorphic rocks with PT conditions ~200–500 MPa and 400–650 °C, where they are concentrated in districts and groups. Known combined resources add up 200,000 t of spodumene, with variable grades between 5 and 8 wt.% Li₂O. The potential for future findings and enlargement of the resources is high, since no systematic exploration program has yet been developed. Full article

(This article belongs to the Special Issue Petrology and Mineralogy of Pegmatite Deposits)

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