Geology of late-Variscan Sàrrabus pluton (south-eastern Sardinia, Italy)

Secchi, Francesco; Naitza, Stefano; Oggiano, Giacomo; Cuccuru, Stefano; Puccini, Antonio; Conte, Aida Maria; Giovanardi, Tommaso; Mazzucchelli, Maurizio

doi:10.1080/17445647.2021.1982032

Cited by 7 publications

(16 citation statements)

References 44 publications

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“…Once exhumed at shallow structural levels, the Rosas Shear Zone acted as weakness and permeable zone favorable for the intrusion of mafic dyke and, soon after, for extensive granite-related fluid circulation. The ages of each step are supposed taking into account the available dating in the Sardinian basement of the regional metamorphism (~350 Ma, [68], mafic dyke intrusion (~300 Ma, [41,69,70]) and granite intrusion (~289 Ma [17,42]).…”

Section: Discussionmentioning

confidence: 99%

“…The lower Cambrian-lower Carboniferous succession was intruded during lower Permian by numerous granitoid bodies and associated mafic and felsic dikes forming the Sulcis pluton [17] that crops out few kilometers to the SE of the RSZ (Figure 1b) and most likely occurs at shallow depth beneath the Rosas mine district (Figure 1c). In southern Sardinia, the intrusion of mafic dykes is a process that lasted for a long time span, more than 10 Ma, so dykes may pre-date, be coeval or post-date the granite body intrusion [17,41]. The outermost part of the Pluton in Northern Sulcis consists of F-bearing, ferroan ilmeniteseries, subaluminous I-type granites ("GS1 suite", [17]), dated at 289 ± 1 Ma by Re-Os on molybdenite [42].…”

Section: Stratigraphic Settingmentioning

confidence: 99%

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Passive Structural Control on Skarn Mineralization Localization: A Case Study from the Variscan Rosas Shear Zone (SW Sardinia, Italy)

Cocco¹,

Attardi²,

Deidda³

et al. 2022

Minerals

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The case study presented here deals with the Pb-Zn-Cu skarn ores hosted in the Rosas Shear Zone (RSZ), a highly strained domain located in the external zone of the Sardinian Variscan chain. The RSZ is characterized by several tectonic slices of Cambrian limestones within a strongly folded and foliated Cambrian-Ordovician siliciclastic succession, intruded by late Variscan granites and mafic dykes. Based on geological mapping, structural and microscope analyses, our results show that the skarn ores in the RSZ are an example of passive structurally controlled mineralization. The RSZ was structured close to the brittle–ductile transition and, once exhumed to shallower crustal levels, acted as plumbing system favoring a large-scale granite-related fluid circulation. The paragenesis and the mineralization style of the skarn vary slightly according to the peculiarity of the local structural setting: a tectonic slice adjacent to the mafic dyke; an intensely sheared zone or a discrete thrust surface.

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Section: Discussionmentioning

confidence: 99%

Section: Stratigraphic Settingmentioning

confidence: 99%

Passive Structural Control on Skarn Mineralization Localization: A Case Study from the Variscan Rosas Shear Zone (SW Sardinia, Italy)

Cocco¹,

Attardi²,

Deidda³

et al. 2022

Minerals

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“…(1) The older magmatic peak (OMP), prevalently represented in N Sardinia and referable to a period of time spanning from 322 ± 8 Ma in N Sardinia [77,78] to 299 ± 3 Ma in Central Sardinia [79]; (2) The younger magmatic peak (YMP), represented by several plutons emplaced during a shorter span of time, from 291 to 286 Ma [80][81][82].…”

Section: The Sardinia Batholithmentioning

confidence: 99%

“…The dominant felsic character of magmatism appears as a primary crustal signature for the post-collisional magmatism forming the entire SCB. Magma production has been largely interpreted as related to partial melting of crustal materials and interactions of felsic melts with mafic magmas at different levels in the crust [82,83,[92][93][94][95][96][97][98][99][100]. Interactions of crustal magmas with mantle-derived melts are testified by mixing/mingling evidence resulting in hybrid varieties, and by the widespread occurrence of hornblende-pyroxene bearing mafic to tonalitic enclaves in granodiorites [82,99,100].…”

Section: The Sardinia Batholithmentioning

confidence: 99%

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

Naitza,

Casini,

Cocco

et al. 2024

Minerals

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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.

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“…2) is composed of several tectonic units, each of which is characterised by a sedimentary and volcanic succession spanning in age from the early Cambrian to the early Carboniferous. These units were affected by shortening events during Variscan collision and by post-collisional extensional tectonics, leading to uplift of the entire basement and emplacement of Variscan granitoids (Carmignani et al 1994(Carmignani et al , 2016Conti et al 1999;Conte et al 2017;Secchi et al 2021;Cocco et al 2022). The collisional events occurred with associated regional metamorphism, which ranged from very low grade in the southwestern part of the island to high grade in the northern part of the island and produced a nappe stack with dominant topto-the-SSW and subordinate top-to-the-W tectonic transport directions (Conti and Patta 1998;Conti et al 2001;Casini et al 2010;Montomoli et al 2018;Carosi et al 2022;Petroccia et al 2022aPetroccia et al , 2022b.…”

Section: Geological Settingmentioning

confidence: 99%

Ordovician tectonics of the South European Variscan Realm: new insights from Sardinia

Cocco

Loi

Funedda

et al. 2022

Int J Earth Sci (Geol Rundsch)

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Although much is known about the Ordovician tectonics of the South European Variscides, aspects of their geodynamic evolution and palaeogeographic reconstruction remain uncertain. In Sardinia, Variscan tectonic units include significant vestiges of Ordovician evolution, such as a fold system that affected only the Cambrian–Lower Ordovician successions, and are cut by a regional angular unconformity. A comparison of the stratigraphy and tectonic structures of the successions below and above the Lower Ordovician unconformity and a reinterpretation of biostratigraphic data allow us to identify significant differences between the stacked tectonic units. The unconformity is sealed as follows: (i) in the Sulcis–Iglesiente Unit (Variscan External Zone, SW Sardinia) by Middle–Upper Ordovician continental and tidal deposits; and (ii) in the Sarrabus and Gerrei units (part of the Variscan Nappe Zone, SE Sardinia) by Middle–Upper Ordovician calc–alkaline volcanic rocks. Therefore, at the same time, one tectonic unit was situated close to a rifting setting and the others were involved in a convergent margin. Of note are the different durations associated with the unconformities in the tectonic units (17 Myr in the Sulcis–Iglesiente Unit, 6 Myr in the Sarrabus and Gerrei units) and the occurrence (or absence) of glacio-marine deposits indicating that the units were located at different palaeo-latitudes during the Ordovician. These results suggest that the SW and SE Sardinia blocks did not share the same geodynamic setting during the Ordovician, implying that they were situated in different palaeogeographic positions at this time and subsequently amalgamated during the Variscan Orogeny. Furthermore, stratigraphic and tectonic correlations with neighbouring areas, such as the eastern Pyrenees, imply alternative palaeogeographic reconstructions to those proposed previously for some peri-Mediterranean Variscan terranes.

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Geology of late-Variscan Sàrrabus pluton (south-eastern Sardinia, Italy)

Cited by 7 publications

References 44 publications

Passive Structural Control on Skarn Mineralization Localization: A Case Study from the Variscan Rosas Shear Zone (SW Sardinia, Italy)

Passive Structural Control on Skarn Mineralization Localization: A Case Study from the Variscan Rosas Shear Zone (SW Sardinia, Italy)

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

Ordovician tectonics of the South European Variscan Realm: new insights from Sardinia

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