Special Issue "Minerals of Alkaline Igneous Rocks: Chemical and Isotopic Features as Tracers of Magmatic Processes"

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

Deadline for manuscript submissions: 20 July 2022 | Viewed by 3705

Special Issue Editors

Prof. Dr. Massimo D’Antonio
E-Mail Website
Guest Editor
Dipartimento di Scienze della Terra, dell’Ambiente e delle Risorse, Università degli Studi di Napoli Federico II, Complesso Universitario di Monte Sant’Angelo, Via Vicinale Cupa Cintia 21, 80126 Napoli, Italy
Interests: geochemistry; radiogenic and stable isotopes geochemistry; igneous petrology; volcanology; tephrochronology and tephrostratigraphy; diffusion chronometry; human mobility and diet; environmental isotope geochemistry; archaeometry
Dr. Ilenia Arienzo
E-Mail Website
Guest Editor
Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Vesuviano, Via Diocleziano 328, 80124 Napoli, Italy
Interests: geochemistry; isotopes geochemistry; igneous petrology; volcanology; tephrochronology and tephrostratigraphy; diffusion chronometry; human mobility and diet; archaeometry

Special Issue Information

Dear Colleagues,

The minerals of alkaline igneous rocks (MAIR), both plutonic and volcanic, e.g., olivine, clinopyroxene, feldspars, opaque oxides, black mica, and amphibole, have an extremely variable composition, being solid solutions among several pure components. A relevant property of MAIR is their attitude to provide estimates of P–T–fO2 conditions during magma crystallization, because changes in thermodynamic parameters induce element and isotope exchanges in minerals. Therefore, MAIR are precious archives of the crystallization history of host rocks, recording a variety of magmatic processes. Diffusion of major and trace elements within MAIR provides timescale estimates of several magmatic processes occurring from nucleation until growth of the very last crystal rim, providing important insights for volcanic hazard assessment. Moreover, combining radiogenic and stable isotopes and chemistry of MAIR opens an even wider window on the Earth’s interior. This Special Issue aims at gathering studies dealing with chemical and isotopic variations of MAIR from relevant areas of magmatism worldwide. We welcome contributions concerning mineral chemistry, geothermobarometry, and isotopes on MAIR, aimed at assessing P-T-fO2 conditions of magma cooling, unveiling pre-eruptive magmatic processes and their timescales. Methodological studies exploring new frontiers of such issues are strongly solicited too, offering significant contributions to better understand magmatic processes and precursor phenomena.

Prof. Dr. Massimo D’Antonio
Dr. Ilenia Arienzo
Guest Editors

Manuscript Submission Information

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Keywords

  • Alkaline igneous rocks
  • P–T–fO2 conditions
  • Geothermobarometry
  • Radiogenic and stable isotopes
  • Diffusion chronometry
  • Timescales of magmatic processes

Published Papers (4 papers)

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Research

Article
On the Morphology and Geochemistry of Hydrothermal Crypto- and Microcrystalline Zircon Aggregates in a Peralkaline Granite
Minerals 2022, 12(5), 628; https://doi.org/10.3390/min12050628 - 14 May 2022
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Abstract
Singular crypto- and microcrystalline hydrothermal zircon aggregates occur in peralkaline granites from the Corupá Pluton of “A-type” granites and syenites in Graciosa Province, Southern Brazil, and are herein characterized for their morphological, textural and geochemical (major, minor and trace elements, and Lu-Hf isotopes) [...] Read more.
Singular crypto- and microcrystalline hydrothermal zircon aggregates occur in peralkaline granites from the Corupá Pluton of “A-type” granites and syenites in Graciosa Province, Southern Brazil, and are herein characterized for their morphological, textural and geochemical (major, minor and trace elements, and Lu-Hf isotopes) properties. The aggregates were found to present a variety of habits, such as dendritic, oolitic, botryoidal and spherulitic, and they are associated with typical hydrothermal minerals (alkali-feldspars, quartz, fluorite, epidote-group minerals, phyllosilicates and Fe oxides) in micro-fractures and small miarolitic cavities in the host rock. They precipitated directly from a hydrothermal fluid and, compared to magmatic zircon crystals from the host, were found to contain relatively high abundances of the “non-formula” elements (e.g., Fe, Al, and Ca) and HFSEs (High-Field-Strength Elements), particularly the L- and MREEs (Light and Medium Rare Earth Elements), features most typical of hydrothermal zircon, as well as high Th/U ratios, whereas the Lu-Hf isotopic signatures were found to be similar. The formation of the zircon aggregates and the associated epidote-groups minerals was probably due to the interaction between an orthomagmatic, F-bearing, aqueous fluid transporting the HFSEs with the host-rock and/or with an external meteoritic fluid from the country rocks. The preservation of an amorphous-like Zr-silicate compound and crypto-to-microcrystalline zircon varieties is arguably related to the inefficient fluid flux and/or elemental diffusion in a low-temperature oxidizing environment. Full article
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Article
Mineral-Melt Equilibria and Geothermobarometry of Campi Flegrei Magmas: Inferences for Magma Storage Conditions
Minerals 2022, 12(3), 308; https://doi.org/10.3390/min12030308 - 28 Feb 2022
Cited by 1 | Viewed by 558
Abstract
The eruptions of Campi Flegrei (Southern Italy), one of the most studied and dangerous active volcanic areas of the world, are fed by mildly potassic alkaline magmas, from shoshonite to trachyte and phonotrachyte. Petrological investigations carried out in past decades on Campi Flegrei [...] Read more.
The eruptions of Campi Flegrei (Southern Italy), one of the most studied and dangerous active volcanic areas of the world, are fed by mildly potassic alkaline magmas, from shoshonite to trachyte and phonotrachyte. Petrological investigations carried out in past decades on Campi Flegrei rocks provide crucial information for understanding differentiation processes in its magmatic system. However, the compositional features of rocks are a palimpsest of many processes acting over timescales of 100–104 years, including crystal entrapment from multiple reservoirs with different magmatic histories. In this work, olivine, clinopyroxene and feldspar crystals from volcanic rocks related to the entire period of Campi Flegrei’s volcanic activity are checked for equilibrium with combined and possibly more rigorous tests than those commonly used in previous works (e.g., Fe–Mg exchange between either olivine or clinopyroxene and melt), with the aim of obtaining more robust geothermobarometric estimations for the magmas these products represent. We applied several combinations of equilibrium tests and geothermometric and geobarometric methods to a suite of rocks and related minerals spanning the period from ~59 ka to 1538 A.D. and compared the obtained results with the inferred magma storage conditions estimated in previous works through different methods. This mineral-chemistry investigation suggests that two prevalent sets of T–P (temperature–pressure) conditions, here referred to as “magmatic environments”, characterized the magma storage over the entire period of Campi Flegrei activity investigated here. These magmatic environments are ascribable to either mafic or differentiated magmas, stationing in deep and shallow reservoirs, respectively, which interacted frequently, mostly during the last 12 ka of activity. In fact, open-system magmatic processes (mixing/mingling, crustal contamination, CO2 flushing) hypothesized to have occurred before several Campi Flegrei eruptions could have removed earlier-grown crystals from their equilibrium melts. Moreover, our new results indicate that, in the case of complex systems such as Campi Flegrei’s, in which different pre-eruptive processes can modify the equilibrium composition of the crystals, one single geothermobarometric method offers little chance to constrain the magma storage conditions. Conversely, combined methods yield more robust results in agreement with estimates obtained in previous independent studies based on both petrological and geophysical methods. Full article
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Article
Sr-Nd Isotopic Composition of Pyroxenes as a Provenance Indicator of a Double-Volcanic Source in Sands of the Ofanto River (Southern Italy)
Minerals 2022, 12(2), 232; https://doi.org/10.3390/min12020232 - 11 Feb 2022
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Abstract
The sands of the Ofanto River (Southern Italy) include a volcaniclastic component represented by clinopyroxene, melanite garnet, amphibole and subordinate volcanic lithics. In order to infer the provenance of this component, we have conducted a microanalytical and isotopic study on the volcanic minerals [...] Read more.
The sands of the Ofanto River (Southern Italy) include a volcaniclastic component represented by clinopyroxene, melanite garnet, amphibole and subordinate volcanic lithics. In order to infer the provenance of this component, we have conducted a microanalytical and isotopic study on the volcanic minerals of the sands collected in three different sites along the Ofanto River: (1) upstream sector, where only sedimentary rocks are drained; (2) middle course, along a tributary draining only the Monte Vulture volcanic rocks, (3) the mouth of the Ofanto. Moreover, minerals of the beach sands of the Tyrrhenian Cilento coast were analyzed for comparison. The microanalytical study and the Sr-Nd isotopic composition reveal the existence of two populations of pyroxenes characterized by distinct isotopic signatures and indicating a provenance from two different volcanic sources. One is confidently identifiable with Monte Vulture, and is evident in the minerals of the middle course and mouth sands. The pyroxenes of the upstream sector, isotopically similar to those of the Cilento coast, have a Campanian signature. The simultaneous occurrence of amphibole and garnet point to the explosive eruptions of Mount Vesuvius as the most probable sources of these minerals. The absence of Campanian pyroxenes at the mouth of the Ofanto River could be related to the occurrence of dams limiting the transport of solids along the river. Full article
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Article
Petrography and Mineral Chemistry of Monte Epomeo Green Tuff, Ischia Island, South Italy: Constraints for Identification of the Y-7 Tephrostratigraphic Marker in Distal Sequences of the Central Mediterranean
Minerals 2021, 11(9), 955; https://doi.org/10.3390/min11090955 - 31 Aug 2021
Cited by 2 | Viewed by 1159
Abstract
The 56 ka Monte Epomeo Green Tuff (MEGT) resulted from the largest volume explosive eruption from Ischia island (south Italy). Its tephra is one of the main stratigraphic markers of the central Mediterranean area. Despite its importance, a detailed characterisation of the petrography [...] Read more.
The 56 ka Monte Epomeo Green Tuff (MEGT) resulted from the largest volume explosive eruption from Ischia island (south Italy). Its tephra is one of the main stratigraphic markers of the central Mediterranean area. Despite its importance, a detailed characterisation of the petrography and mineral chemistry of MEGT is lacking. To fill this gap, we present detailed petrographic description and electron microprobe mineral chemistry data on samples collected on-land from the MEGT. Juvenile clasts include pumice, scoria, and obsidian fragments with porphyritic/glomeroporphyritic, vitrophyric, and fragmental textures. The porphyritic index is 13–40 vol.%, and phenocryst phases include alkali-feldspar, plagioclase, clinopyroxene, ferrian phlogopite, and titano-magnetite, in order of decreasing abundance; accessory phases include sphene, hydroxy-fluor-apatite, and rare edenite. Plagioclase varies from predominant andesine to subordinate oligoclase, whereas alkali-feldspar is more variable from sanidine to anorthoclase; quasi-pure sanidine commonly occurs as either rim or recrystallisation overgrowth of large phenocrysts due to hydrothermal alteration. Secondary minerals include veins and patches of carbonate minerals, Fe-Mn oxyhydroxides, clay minerals, and zeolites. Clinopyroxene is ferroan diopside (En45–29Fs7–27) and never reaches Na-rich compositions. This feature allows the discrimination of MEGT from aegirine-bearing, distal tephra layers erroneously attributed to MEGT, with implications for the areal distribution of Ischia explosive deposits. Full article
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

1. Title: Decoding the Holocene Magmatic System at el Hierro (Canary Islands, Spain): Insights from Olivines and Clinopyroxenes

Authors: Prieto-Torrell, C.; Aulinas, M.; Arienzo, I; Fernandez-Turiel, J.L.; Rodriguez-Gonzalez, A.; Perez-Torrado, F.J., D’Antonio, M.; Cabrera, M.C.

2. Title: The Campi Flegrei Magmatic Feeding System: Constrains from Mineral-Melt Thermobarometry

Authors: C. Pelullo; R.S. Iovine; I. Arienzo; M. D’Antonio; L. Pappalardo; P. Petrosino

3. Title: Geochemical and Sr-Isotopic Data of Clinopyroxenes from Somma- Vesuvius Lavas: Inferences for Magmatic Processes

Authors: Valeria Di Renzo; Ilenia Arienzo; Lucia Civetta; Paola Petrosino; Massimo D’Antonio

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