Geochemistry of Granites and Granitic Pegmatites

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Deposits".

Deadline for manuscript submissions: closed (15 September 2020) | Viewed by 10737

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Institute of Geology of the Czech Academy of Science, CZ-165 00 Praha, Czech Republic
Interests: granite petrology; rock-forming minerals; granite-related mineral deposits
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Dear Colleagues,

Granite represents one of the most widespread rocks on the Earth’s crust, and together with chemically similar pegmatites, it is also the most important source of several rare metals, such as Nb, Ta, W, Sn, and Li, which are significant for new technologies. Though granite has been studied systematically in all possibly respects for a long time, many aspects of its origin are still matter of controversial debate. In particular, the following issues are unsolved: (i) whether high concentrations of rare elements are the product of pronounced fractionation of common melt or unusually low degree-melting of a special protolith; (ii) the relationship between melt- and fluid-related processes in the final stage of granite evolution and the origin of granite-related mineral deposits; and (iii) the critical parameter for crystallization of acid silicate melt as homogeneous granite, layered rock, or regularly zoned pegmatite.

This Special Issue invites authors to submit papers on geochemical, isotopic, and experimental studies, as well as case studies of magmatic vs. hydrothermal rock textures and the evaluation of mineral zoning. Studies combining high-precision chemical analyses with detailed imaging methods (BSE, CL, automated mineralogical maps) are of special interest.

Dr. Karel Breiter
Guest Editor

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Keywords

  • origin of granitic melt
  • magmatic fractionation vs. fluid-related processes
  • granite vs. pegmatite enigma
  • textures, a key to understanding of the rock evolution
  • zoning of minerals—snaps from the rock history

Published Papers (3 papers)

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Research

21 pages, 7393 KiB  
Article
Compositional Variability of Monazite–Cheralite–Huttonite Solid Solutions, Xenotime, and Uraninite in Geochemically Distinct Granites with Special Emphasis to the Strongly Fractionated Peraluminous Li–F–P-Rich Podlesí Granite System (Erzgebirge/Krušné Hory Mts., Central Europe)
by Karel Breiter and Hans-Jürgen Förster
Minerals 2021, 11(2), 127; https://doi.org/10.3390/min11020127 - 27 Jan 2021
Cited by 3 | Viewed by 2408
Abstract
A comprehensive study of monazite–cheralite–huttonite solid solutions (s.s.) and xenotime from the highly evolved, strongly peraluminous P–F–Li-rich Podlesí granite stock in the Krušné Hory Mts., Czech Republic, indicates that, with the increasing degree of magmatic and high-T early post-magmatic evolution, the content of [...] Read more.
A comprehensive study of monazite–cheralite–huttonite solid solutions (s.s.) and xenotime from the highly evolved, strongly peraluminous P–F–Li-rich Podlesí granite stock in the Krušné Hory Mts., Czech Republic, indicates that, with the increasing degree of magmatic and high-T early post-magmatic evolution, the content of the cheralite component in monazite increases and the relative dominance of middle rare earth elements (MREE) in xenotime becomes larger. Considering the overall compositional signatures of these two accessory minerals in the late Variscan granites of the Erzgebirge/Krušné Hory Mts., three types of granites can be distinguished: (i) chemically less evolved F-poor S(I)- and A-type granites contain monazite with a smooth, mostly symmetric chondrite-normalized (CN) rare-earth elements (REE) pattern gradually declining from La to Gd; associated xenotime is Y-rich (˃0.8 apfu Y) with a flat MREE–HREE (heavy rare earth elements) pattern; (ii) fractionated A-type granites typically contain La-depleted monazite with Th accommodated as the huttonite component, combined with usually Y-poor (0.4–0.6 apfu Y) xenotime characterized by a smoothly inclining, Yb–Lu-dominant CN-REE pattern; (iii) fractionated peraluminous Li-mica granites host monazite with a flat, asymmetric (kinked at La and Nd) CN-LREE pattern, with associated xenotime distinctly MREE (Gd–Tb–Dy)-dominant. Monazite and xenotime account for the bulk of the REE budgets in all types of granite. In peraluminous S(I)-type granites, which do not bear thorite, almost all Th is accommodated in monazite–cheralite s.s. In contrast, Th budgets in A-type granites are accounted for by monazite–huttonite s.s. together with thorite. The largest portion of U is accommodated in uraninite, if present. Full article
(This article belongs to the Special Issue Geochemistry of Granites and Granitic Pegmatites)
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26 pages, 7677 KiB  
Article
The Tres Arroyos Granitic Aplite-Pegmatite Field (Central Iberian Zone, Spain): Petrogenetic Constraints from Evolution of Nb-Ta-Sn Oxides, Whole-Rock Geochemistry and U-Pb Geochronology
by Idoia Garate-Olave, Encarnación Roda-Robles, Pedro Pablo Gil-Crespo, Alfonso Pesquera and Jon Errandonea-Martin
Minerals 2020, 10(11), 1008; https://doi.org/10.3390/min10111008 - 12 Nov 2020
Cited by 12 | Viewed by 3056
Abstract
Abundant Li-Cs-Ta aplite-pegmatite dykes were emplaced in the western Central Iberian Zone of the Iberian Massif during the Variscan Orogeny. Their origin and petrogenetic relationships with the widespread granitoids have led to a currently rekindled discussion about anatectic vs. granitic origin for the [...] Read more.
Abundant Li-Cs-Ta aplite-pegmatite dykes were emplaced in the western Central Iberian Zone of the Iberian Massif during the Variscan Orogeny. Their origin and petrogenetic relationships with the widespread granitoids have led to a currently rekindled discussion about anatectic vs. granitic origin for the pegmatitic melts. To deal with these issues, the aplite-pegmatite dykes from the Tres Arroyos area, which constitute a zoned pegmatitic field related to the Nisa-Alburquerque granitic batholith, have been studied. This work comprises a complete study of Nb-Ta-Sn oxides’ mineralogy, whole-rock geochemistry, and U-Pb geochronology of the aplite-pegmatites that have been grouped as barren, intermediate, and Li-rich. The most abundant Nb-Ta-Sn oxides from Tres Arroyos correspond to columbite-(Fe), columbite-(Mn) and cassiterite. Niobium-Ta oxides show a marked increase in the Mn/(Mn+Fe) ratio from the barren aplite-pegmatites up to the Li-rich bodies, whereas variations in the Ta/(Ta+Nb) ratio are not continuous. The probable factors controlling fractionation of Mn/Fe and Ta/Nb reflected in Nb-Ta oxides may be attributed to the crystallization of tourmaline, phosphates and micas. The lack of a progressive Ta/Nb increase with the fractionation may be also influenced by the high F and P availability in the parental pegmatitic melts. Most of the primary Nb-Ta oxides would have crystallized by punctual chemical variations in the boundary layer, whereas cassiterite formation would be related to an undercooling of the system. Whole-rock composition of the distinguished lithotypes reflects similar tendencies to those observed in mineral chemistry, supporting a single path of fractional crystallization from the parental Nisa-Alburquerque monzogranite up to the most evolved Li-rich aplite-pegmatites. The age of 305 ± 9 Ma, determined by LA-ICP-MS U-Pb dating of columbite-tantalite oxides, reinforces the linkage of the studied aplite-pegmatites and the cited parental monzogranite. Full article
(This article belongs to the Special Issue Geochemistry of Granites and Granitic Pegmatites)
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22 pages, 12013 KiB  
Article
Geochronology and Geochemistry of Archean TTG and Tremolite Schist Xenoliths in Yemadong Complex: Evidence for ≥3.0 Ga Archean Continental Crust in Kongling High-Grade Metamorphic Terrane, Yangtze Craton, China
by Yunxu Wei, Wenxiao Zhou, Zhengxiang Hu, Haiquan Li, Xianxiao Huang, Xiaoming Zhao and Daliang Xu
Minerals 2019, 9(11), 689; https://doi.org/10.3390/min9110689 - 8 Nov 2019
Cited by 13 | Viewed by 4436
Abstract
The origin and significance of the tonalite–trondhjemite–granodiorite (TTG) units and the familiar metabasite xenoliths they host in the Yangtze Craton, China, remain controversial, and resolving these issues is important if we are to understand the evolution of the early Yangtze Craton. We focused [...] Read more.
The origin and significance of the tonalite–trondhjemite–granodiorite (TTG) units and the familiar metabasite xenoliths they host in the Yangtze Craton, China, remain controversial, and resolving these issues is important if we are to understand the evolution of the early Yangtze Craton. We focused on biotite–tremolite schist xenoliths in the Archean TTG units of the Kongling high-grade metamorphic terrane, and U–Pb dating of their zircons yielded 207Pb/206Pb ages of ca. 3.00 Ga, which provides a minimum age for the formation of the pre-metamorphic basic igneous rock. The host TTGs and late intrusive granitic dikes yield three groups of upper intercept ages at 2.87–2.88, 2.91–2.94, and 3.07 Ga, and a concordant age at 2.94 Ga, which suggest that the Yangtze continental nucleus underwent three important metamorphic–magmatic events in the Mesoarchean at ca. 3.00, 2.94, and 2.87 Ga. The biotite–tremolite schists have high ratios of K2O/Na2O and high contents of CaO, Cr, and Ni, thus showing the characteristics of high-K calc-alkaline island-arc volcanic rocks (basalt–andesite) that form by the partial melting of subducted oceanic crust. The data also provide further proof that a Mesoarchean metamorphic basement exists in the Yangtze Plate. Derivation of the magmatic protoliths of the biotite–tremolite schist enclaves from an oceanic crust during slab subduction, and the presence of these xenoliths within the TTG suite, indicate the existence of the initiation of plate tectonics during the Mesoarchean (≤2.94 Ga). Full article
(This article belongs to the Special Issue Geochemistry of Granites and Granitic Pegmatites)
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