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18 pages, 18259 KiB

Open AccessArticle

Petrographic and Geochemical Inferences for Genesis of Terra Rossa: A Case Study from the Apulian Karst (Southern Italy)

by Francesca Micheletti, Annamaria Fornelli, Luigi Spalluto, Mario Parise, Salvatore Gallicchio, Fabrizio Tursi and Vincenzo Festa

Minerals 2023, 13(4), 499; https://doi.org/10.3390/min13040499 - 31 Mar 2023

Cited by 2 | Viewed by 1442

Abstract

Terra rossa is a reddish clay soil which is often present on the surface of limestone in regions with a Mediterranean-type climate. Its genesis is a controversial subject in terms of the origin of the parent material, from the residuum of underlying (carbonate/dolomite) [...] Read more.

Terra rossa is a reddish clay soil which is often present on the surface of limestone in regions with a Mediterranean-type climate. Its genesis is a controversial subject in terms of the origin of the parent material, from the residuum of underlying (carbonate/dolomite) bedrock in the absence/presence of an external silicate contribution (e.g., aeolian dust). Within this context the main goal of the present work was the understanding of the geochemical processes leading to the formation of the terra rossa starting from the carbonate bedrock. We report the results of a multi-method analysis on a terra rossa deposit occupying the bottom of a Quaternary karst depression on Mesozoic limestones exposed in the Murge area (Apulia Foreland, southern Italy). Geological, petrographic, textural, and chemical data were collected on karst products (reddish calcite incrustations and nodules, and fine-grained portion of terra rossa) by a detailed field mapping, optical microscopy, XRF and fusion ICP/MS analyses and by scanning electron microscope. New collected data show that the mineralogical composition of reddish incrustations and nodules is comparable, consisting of fibrous and impure calcite, detrital fragments of quartz, K-feldspar, zircon and authigenic minerals as (Mn, Ba, Ca) phases, (Al, Si, Mn, Fe, Mg, Ba, Ca) minerals, Fe-kaolinite and anatase. The prevailing minerals, instead, in the fine-grained portion of terra rossa are hematite, kaolinite, and goethite. Based on the chemical composition, and especially on REE patterns, a progressive interaction of silicate aqueous solutions (with Al, Si, Fe), containing pelite material, with the calcareous bedrock, as a source of carbonic acid, was the process driving the formation of terra rossa. Obtained results add new elements to the definition of the long-lasting question about the genetic processes responsible for the formation of terra rossa, corroborating their polygenetic origin, as result of limestone alteration in conjunction with the chemical interaction with allochthonous siliciclastic material. Full article

(This article belongs to the Special Issue Understanding the Geologic History of Italy: Perspectives from Geochemistry, Geology and Mineralization)

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Review

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32 pages, 23821 KiB

Open AccessReview

The Ophiolite-Hosted Cu-Zn VMS Deposits of Tuscany (Italy)

by Andrea Dini, Andrea Rielli, Paolo Di Giuseppe, Giovanni Ruggieri and Chiara Boschi

Minerals 2024, 14(3), 273; https://doi.org/10.3390/min14030273 - 04 Mar 2024

Viewed by 1054

Abstract

Several Jurassic, ophiolite-hosted Cu-Zn VMS deposits occur in Tuscany. They are hosted by tectonic units of oceanic affinity (Ligurian Units), such as the well-known deposits of nearby Liguria. Industrial production was small and definitively ceased in the 1960s. Locally, massive ore (chalcopyrite-bornite-chalcocite) with [...] Read more.

Several Jurassic, ophiolite-hosted Cu-Zn VMS deposits occur in Tuscany. They are hosted by tectonic units of oceanic affinity (Ligurian Units), such as the well-known deposits of nearby Liguria. Industrial production was small and definitively ceased in the 1960s. Locally, massive ore (chalcopyrite-bornite-chalcocite) with an exceptionally high grade was found. The Montecatini Val di Cecina mine exploited the largest “bonanza” and, for few decades in the 19th century, became one of the most profitable copper mines in Europe. This study provides an updated review of these deposits. Tuscan Cu-Zn VMSs mostly occur in proximity of the contact between the serpentinite-gabbro basement and the overlying basalts. Chalcopyrite-pyrite stockworks occur in serpentinite-gabbro cut by dolerite dykes, while the largest massive sulphide bodies are hosted by polymictic-monomictic breccias at the base of pillow basalts. Early chalcopyrite ores were mechanically–chemically reworked and upgraded to bornite-rich nodular ore embedded in a chlorite, calcic amphibole, Fe-rich serpentine, quartz, andradite, ilvaite, and xonotlite assemblage. This bornite-rich ore contains substantial amount of sphalerite and pyrite and ubiquitous grains of clausthalite, hessite, tellurium, and gold. They represent a prime example of the sub-seafloor portion of a hybrid mafic-ultramafic oceanic hydrothermal system formed in an OCC along the slow spreading ridge of the Jurassic Piedmont-Ligurian Ocean. The peculiar mineralogical–textural character of the bornite-rich ore was driven by an interface coupled dissolution–precipitation process mediated by fluids. Full article

(This article belongs to the Special Issue Understanding the Geologic History of Italy: Perspectives from Geochemistry, Geology and Mineralization)

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30 pages, 7994 KiB

Open AccessReview

Post-Collisional Tectonomagmatic Evolution, Crustal Reworking and Ore Genesis along a Section of the Southern Variscan Belt: The Variscan Mineral System of Sardinia (Italy)

by Stefano Naitza, Leonardo Casini, Fabrizio Cocco, Matteo Luca Deidda, Antonio Funedda, Alfredo Loi, Giacomo Oggiano and Francesco Secchi

Minerals 2024, 14(1), 65; https://doi.org/10.3390/min14010065 - 04 Jan 2024

Viewed by 863

Abstract

Since the early Paleozoic, numerous metallogenic events produced in the Sardinian massif a singular concentration of mineral deposits of various kinds. Among them, the Variscan metallogenic peak represents a late Paleozoic phase of diffuse ore formation linked to the tectonomagmatic evolution of the [...] Read more.

Since the early Paleozoic, numerous metallogenic events produced in the Sardinian massif a singular concentration of mineral deposits of various kinds. Among them, the Variscan metallogenic peak represents a late Paleozoic phase of diffuse ore formation linked to the tectonomagmatic evolution of the Variscan chain. Two main classes of ores may primarily be attributed to this peak: (1) mesothermal orogenic-type As-Au ± W ± Sb ores, only found in E Sardinia, and (2) intrusion-related Sn-W-Mo-F and base metals-bearing ores found in the whole Sardinian Batholith, but mainly occurring in central–south Sardinia. Both deposit classes formed diachronously during the Variscan post-compressional extension. The orogenic-type ores are related to regional-scale flows of mineralizing fluids, and the intrusion-related ores occur around fertile intrusions of different granite suites. Metallogenic reconstructions suggest almost entirely crustal processes of mineralization without a significant contribution from the mantle. We summarized these processes with a holistic approach and conceptualized the Sardinian Variscan Mineral System (SVMS), a crustal-scale physical system of ore mineralization in the Sardinian basement. The SVMS required suitable metal sources in the crust and diffuse crustal reworking triggered by heat that allowed (a) the redistribution of the original metal budget of the crust in magmas by partial melting and (b) the production of metal-bearing fluids by metamorphic dehydration. Heat transfer in the Sardinian Variscan crust involved shear heating in lithospheric shear zones and the role of mantle uplift as a thermal engine in an extensional tectonic setting. Lithospheric shear zones acted as effective pathways in focusing fluid flow through a large-scale plumbing system into regional-scale structural traps for ores. Pre-Variscan metal sources of metallogenic relevance may have been (1) the magmatic arc and magmatic arc-derived materials of Ordovician age, extensively documented in E Sardinia crust, and (2) an inferred Precambrian crystalline basement lying under the Phanerozoic crustal section, whose presence has been assumed from geophysical data and from petrological and geochemical characteristics of granite suites. At shallower crustal levels, important contributions of metals may have come from pre-Variscan ore sources, such as the Pb-Zn MVT Cambrian ores of SW Sardinia or the REE-bearing Upper Ordovician paleoplacers of E Sardinia. Full article

(This article belongs to the Special Issue Understanding the Geologic History of Italy: Perspectives from Geochemistry, Geology and Mineralization)

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22 pages, 3615 KiB

Open AccessReview

Mineralization and Skarn Formation Associated with Alkaline Magma Chambers Emplaced in a Limestone Basement: A Review

by Marco Knuever, Daniela Mele and Roberto Sulpizio

Minerals 2023, 13(9), 1184; https://doi.org/10.3390/min13091184 - 09 Sep 2023

Viewed by 1299

Abstract

The emplacement of shallow magma chambers within a carbonate basement is a typical feature of many volcanic systems around the world. The accompanying formation of exoskarns, endoskarns, cumulates, exsolved fluids and differentiated melts at the interface between the magma chamber and carbonate host-rock [...] Read more.

The emplacement of shallow magma chambers within a carbonate basement is a typical feature of many volcanic systems around the world. The accompanying formation of exoskarns, endoskarns, cumulates, exsolved fluids and differentiated melts at the interface between the magma chamber and carbonate host-rock is well documented through mineralogical and geochemical studies of ejected skarns and cumulates and through fluid and melt inclusion studies. This review presents the current knowledge on the interaction of alkaline magma chambers with carbonate-bearing host-rocks, with a focus on the geochemical evolution and mineralization at the outer margins of the magma chamber and the accessory mineral phases at Somma-Vesuvius, Colli Albani and Merapi volcanic systems. Furthermore, we discuss how this interaction and its products, especially the CO₂ released during the thermometamorphic decarbonation of the carbonate host-rock, impacts the eruptive behavior in all three systems. Full article

(This article belongs to the Special Issue Understanding the Geologic History of Italy: Perspectives from Geochemistry, Geology and Mineralization)

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19 pages, 21682 KiB

Open AccessReview

A Review of the Mineralogy, Petrography, and Geochemistry of Serpentinite from Calabria Regions (Southern Italy): Problem or Georesource?

by Rosalda Punturo, Roberto Visalli and Rosolino Cirrincione

Minerals 2023, 13(9), 1132; https://doi.org/10.3390/min13091132 - 26 Aug 2023

Viewed by 1225

Abstract

Serpentinite rocks testify to the ocean-floor metamorphism that took place and transformed the original mineralogy and fabric of previous ultramafic rocks. Due to their tectonic and petrological importance, in recent decades, there has been increasing interest in serpentinites. From the economic point of [...] Read more.

Serpentinite rocks testify to the ocean-floor metamorphism that took place and transformed the original mineralogy and fabric of previous ultramafic rocks. Due to their tectonic and petrological importance, in recent decades, there has been increasing interest in serpentinites. From the economic point of view, it is worth noting that, due to their beauty and attractiveness, serpentinite rocks have been exploited and traded as building and ornamental stones since prehistorical times worldwide. In this work, we provide a comprehensive report of the petrographic, mineralogical, petrophysical, and geochemical features of the serpentinites cropping out in the northern sector of the Calabria–Peloritani Orogen (Italy), where the historical quarries are located. Since these serpentinite rocks have been traded for a long time and employed as an excellent building material, their detailed knowledge may provide a useful tool to understand their behavior when they are employed as building materials, to predict their performances upon emplacement in monuments, and to plan correct restoration by considering the provenance of the lithotypes employed. Moreover, comprehensive characterization is also particularly important because it has been reported that serpentinites from Calabria may contain asbestiform and other fibrous minerals, as testified by the occurrence of chrysotile, tremolite, and actinolite asbestos located within the veins, which could lead to health problems due to asbestos fiber exposure. Finally, serpentinite may be considered as an important potential CO₂ sequestration sink. Full article

(This article belongs to the Special Issue Understanding the Geologic History of Italy: Perspectives from Geochemistry, Geology and Mineralization)

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19 pages, 4715 KiB

Open AccessReview

Geochemistry as a Clue for Paleoweathering and Provenance of Southern Apennines Shales (Italy): A Review

by Roberto Buccione, Giovanna Rizzo and Giovanni Mongelli

Minerals 2023, 13(8), 994; https://doi.org/10.3390/min13080994 - 26 Jul 2023

Viewed by 798

Abstract

The southern Apennines (Italy) chain is a fold-and-thrust belt mainly derived from the deformation of the African–Apulian passive margin where shallow-water, basinal, and shelf-margin facies successions, including fine-grained sediments, occur. Here, we provide a review of the geochemistry of Meso–Cenozoic shales from the [...] Read more.

The southern Apennines (Italy) chain is a fold-and-thrust belt mainly derived from the deformation of the African–Apulian passive margin where shallow-water, basinal, and shelf-margin facies successions, including fine-grained sediments, occur. Here, we provide a review of the geochemistry of Meso–Cenozoic shales from the Lagonegro basin to elucidate provenance and paleoweathering. The different suites of these shales are dominated by 2:1 clay minerals and are Fe shales and shales. An R-mode factor analysis suggests Ti, Al, and LREE (F1) and K₂O-MgO (F2) covariance, likely related to the illite → smectite → kaolinite evolution during weathering. HREE and Y are distributed by phosphate minerals, suggesting LREE/HREE fractionation. The CIA paleoweathering proxy rules out non-steady-state weathering conditions and indicates that the source area was affected by moderate to intense weathering. The paleoprecipitation values derived from the CIA-K and CALMAG indices show median values in the 1214–1610 mm/y range. The Eu/Eu*, Sm/Nd, and Ti/Al provenance ratios point toward a UCC-like source excluding any mafic supply and suggest that the Lagonegro basin was connected, through a southern area, with the African cratonic area. However, the Eu/Eu* median value of the southern Apennine shales is quite similar to the value of the Archean shales, possibly indicating a less differentiated component. This is consistent, in many samples, with the value of the (Gd/Yb)_ch ratio, suggesting that the shales likely incorporated ancient sediments derived from African Archean terranes through a cannibalistic process. Full article

(This article belongs to the Special Issue Understanding the Geologic History of Italy: Perspectives from Geochemistry, Geology and Mineralization)

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12 pages, 3402 KiB

Open AccessFeature PaperReview

Campiglia Marittima Skarn (Tuscany): A Challenging Example for the Evolution of Skarn-Forming Models

by Simone Vezzoni, Sergio Rocchi and Andrea Dini

Minerals 2023, 13(4), 482; https://doi.org/10.3390/min13040482 - 29 Mar 2023

Viewed by 1107

Abstract

Campiglia Marittima (hereafter Campiglia) has a long record of attracting interest on its ore deposits that have been intermittently exploited from the Copper Age to the late XX century. Since the XIX century, Campiglia has been a key locality for the debate on [...] Read more.

Campiglia Marittima (hereafter Campiglia) has a long record of attracting interest on its ore deposits that have been intermittently exploited from the Copper Age to the late XX century. Since the XIX century, Campiglia has been a key locality for the debate on skarn-forming processes due to the presence of mining activities ensuring access to ever new rock exposures. The pioneering study of vom Rath and the comparison with attractive chemical model (e.g., Korzhinskii’s theory) in the XX century made Campiglia a “classic” example of skarn ore deposit, from the causative intrusion to the marble host rock. In recent years, detailed field investigations integrated by petrographic, geochemical, and isotopic analyses revealed a more complex and stimulating geological history. The Campiglia skarn was later intruded by mafic magma causing textural reworking and chemical redistribution as well as the reverse telescoping process with Fe-Cu sulfides overprinting previously formed Pb-Zn ore. This work aims to trace the evolution of the scientific thinking on the Campiglia ore deposit by comparison with existing skarn-forming models and, ultimately, shows that the current skarn-forming model(s) cannot fully explain the textural and geochemical features of the Campiglia skarn. Full article

(This article belongs to the Special Issue Understanding the Geologic History of Italy: Perspectives from Geochemistry, Geology and Mineralization)

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26 pages, 2287 KiB

Open AccessReview

Review of Polymetallic Mineralization in the Sila and Serre Massifs (Calabria, Southern Italy)

by Rosa Anna Fregola, Antonio Ciccolella, Vincenzo Festa, Giovanni Ruggieri, Emanuela Schingaro, Fabrizio Tursi and Gennaro Ventruti

Minerals 2023, 13(3), 439; https://doi.org/10.3390/min13030439 - 19 Mar 2023

Viewed by 2047

Abstract

We provide an updated overview of the known mineral deposits from the Sila and Serre Massifs in Calabria, contributing to setting their genesis within a complex geologic history, starting from the late-Carboniferous. We summarize the mineralization reported in the literature, with a critical [...] Read more.

We provide an updated overview of the known mineral deposits from the Sila and Serre Massifs in Calabria, contributing to setting their genesis within a complex geologic history, starting from the late-Carboniferous. We summarize the mineralization reported in the literature, with a critical review of the host tectonic units, by taking into account the upgrades in the knowledge of these areas. We also set them in updated geological maps and in stratigraphic columns, highlighting the crustal levels to which they pertain. Despite the geologic and minerogenetic similarities potentially existing with late- to post-Variscan mineral deposits from other regions (e.g., Sardinia and French Central Massif), the scientific literature on the Calabria mineralization is out-of-date and not exhaustive. Moreover, these ore deposits were likely considered not economically attractive enough to stimulate new scientific studies. However, in our opinion, such studies are needed to resolve the main open questions, which rely on deciphering the origin and age of mineralization. Finally, research for critical elements hosted by the Sila and Serre mineralization (e.g., In, Ge and Ga in sphalerites) is a possible interesting new perspective. Full article

(This article belongs to the Special Issue Understanding the Geologic History of Italy: Perspectives from Geochemistry, Geology and Mineralization)

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