Role of the Sardic tectonic phase in the metallogenesis of SW Sardinia (Iglesiente): lead isotope evidence

Caron, C.; Lancelot, Joël; Omenetto, Paolo; Orgeval, Jean-Jacques

doi:10.1127/ejm/9/5/1005

Cited by 10 publications

(5 citation statements)

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“…Both the E-W folds and the overlying metaconglomerates were subsequently affected by Variscan N-S folds Funneda, 2011, 2017). Sardic-related volcanic rocks are not involved in this area, but Sardicinherited palaeoreliefs are lined with breccia slides that include metre-to-decametre-scale carbonate boulders ("olistoliti"), some of them hosting synsedimentary faults contemporaneously mineralized with ore bodies (Boni and Koeppel, 1985;Boni, 1986;Barca, 1991;Caron et al, 1997). The lower part of the unconformably overlying Monte Argentu Formation was deposited in alluvial to fluvial environments (Martini et al, 1991;Loi et al, 1992;Loi and Dabard, 1997).…”

Section: Sardiniamentioning

confidence: 99%

Comparative geochemical study on Furongian–earliest Ordovician (Toledanian) and Ordovician (Sardic) felsic magmatic events in south-western Europe: underplating of hot mafic magmas linked to the opening of the Rheic Ocean

et al. 2020

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Abstract. A geochemical comparison of early Palaeozoic felsic magmatic episodes throughout the south-western European margin of Gondwana is made and includes (i) Furongian–Early Ordovician (Toledanian) activities recorded in the Central Iberian and Galicia–Trás-os-Montes zones of the Iberian Massif, and (ii) Early–Late Ordovician (Sardic) activities in the Eastern Pyrenees, Occitan Domain (Albigeois, Montagne Noire and Mouthoumet massifs) and Sardinia. Both phases are related to uplift and denudation of an inherited palaeorelief, and stratigraphically preserved as distinct angular discordances and paraconformities involving gaps of up to 22 million years. The geochemical features of the predominantly felsic Toledanian and Sardic activities point to a predominance of magmatic byproducts derived from the melting of metasedimentary rocks, rich in SiO2 and K2O and with a peraluminous character. Zr ∕ TiO2, Zr ∕ Nb, Nb ∕ Y and Zr vs. Ga ∕ Al ratios, and rare-earth element (REE) and εNd(t) values suggest the contemporaneity, for both phases, of two geochemical scenarios characterized by arc and extensional features evolving to distinct extensional and rifting conditions associated with the final outpouring of mafic tholeiite-dominant lava flows. The Toledanian and Sardic magmatic phases are linked to neither metamorphism nor penetrative deformation; on the contrary, their unconformities are associated with foliation-free open folds subsequently affected by the Variscan deformation. The geochemical and structural framework precludes subduction-generated melts reaching the crust in a magmatic arc-to-back-arc setting and favours partial melting of sediments and/or granitoids in the lower continental crust triggered by the underplating of hot mafic magmas related to the opening of the Rheic Ocean.

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Section: Sardiniamentioning

confidence: 99%

Comparative geochemical study on Furongian–earliest Ordovician (Toledanian) and Ordovician (Sardic) felsic magmatic events in south-western Europe: underplating of hot mafic magmas linked to the opening of the Rheic Ocean

et al. 2020

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“…Only 3 new Hg minerals appear between 600 and 430 Ma: imiterite (Ag 2 HgS 2 ) from the 563-544 Ma Imiter mine, Ouarzazate Province, Morocco (Cheilletz et al 2002); perroudite from the 541-519 Ma Tsumeb mine, Otjikoto Region, Namibia; and balkanite (Cu 9 Ag 5 HgS 8 ) from the 520-465 Ma San Giovanneddu mine, Sardinia, Italy (Caron et al 1997;Boni et al 2000). The only other Hg mineral localities from this interval noted in our study (Table 3) are the Bou Azzer District of Morocco (600-550 Ma); Nurali Complex (572-397 Ma) and Uchaly (440-380 Ma), Southern Urals, Russia; Röhrerbühel Mountain, Tyrol, Austria (444-359 Ma); and the Rogaland district of Norway (500-465 Ma).…”

Section: Rifting Of Rodinia and The Short-lived Supercontinent Of Pannotia (~750 To 430 Ma)mentioning

confidence: 99%

Mercury (Hg) mineral evolution: A mineralogical record of supercontinent assembly, changing ocean geochemistry, and the emerging terrestrial biosphere

Hazen

Golden

Downs

et al. 2012

American Mineralogist

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Analyses of the temporal and geographic distribution of earliest recorded appearances of the 88 IMA-approved mercury minerals plus two potentially valid species exemplify principles of mineral evolution. Metacinnabar (HgS) and native Hg are the only two species reported from meteorites, specifically, the primitive H3 Tieschitz chondrite with an age of 4550 Ma. Since the first terrestrial appearance of cinnabar more than 3 billion years ago, mercury minerals have been present continuously at or near Earth's surface.Mercury mineral evolution is characterized by episodic deposition and diversification, perhaps associated with the supercontinent cycle. We observe statistically significant increases in the number of reported Hg mineral localities and new Hg species at ~2.8-2.6, ~1.9-1.8, and ~0.43-0.25 Gaintervals that correlate with episodes of presumed supercontinent assembly and associated orogenies of Kenorland (Superia), Columbia (Nuna), and Pangea, respectively. In constrast, few Hg deposits or new species of mercury minerals are reported from the intervals of supercontinent stability and breakup at ~2.5-1.9, ~1.8-1.2, and 1.1-0.8 Ga. The interval of Pangean supercontinent stability and breakup (~250-65 Ma) is also marked by a significant decline in reported mercury mineralization; however, rocks of the last 65 million years, during which Pangea has continued to diverge, is characterized by numerous ephemeral near-surface Hg deposits.The period ~1.2-1.0 Ga, during the assembly of the Rodinian supercontinent, is an exception because of the absence of new Hg minerals or deposits from this period. Episodes of Hg mineralization reflect metamorphism of Hg-enriched marine black shales at zones of continental convergence. We suggest that Hg was effectively sequestered as insoluble nanoparticles of cinnabar (HgS) or tiemannite (HgSe) during the period of the sulfidic "intermediate ocean" (~1.85-0.85 Ga); consequently, few Hg deposits formed during the aggregation of Rodinia, whereas several deposits date from 800-600 Ma, a period that overlaps with the rifting and breakup of Rodinia.Nearly all Hg mineral species (87 of 90 known), as well as all major economic Hg deposits, are known to occur in formations ≤400 million years old. This relatively recent diversification arises, in part, from the ephemeral nature of many Hg minerals. In addition, mercury mineralization is strongly enhanced by interactions with organic matter, so the relatively recent pulse of new Hg minerals may reflect the rise of a terrestrial biosphere at ~400 Ma.

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“…The I and II domains decipher diagenetic and gouge pyrites, respectively. A -K-feldspars of Cadomian granitoids from Sardinia (Caron, 1994), B -Cambro-Ordivician Pb-Zn sulphides from Sardinia and Montagne Noire (Brévart et al, 1982;Lévêque, 1990;Le Guen et al, 1992;Caron et al, 1997), C -K-feldspars of Variscan granitoids from Southeastern Massif Central (Lévêque, 1990;Le Guen et al, 1991;Caron, 1994;Havard and Lancelot, in prep. ), D -Triassic Pb-Zn sulphides from karst plateau, Southern Massif Central (Brévart et al, 1982;Marcoux, 1987;Le Guen et al, 1991), E -Post-Triassic Pb-Zn sulphides associated with the Cévennes fault, Southern Massif Central (Brévart et al, 1982), F -Cretaceous siltstones 100 Ma ago (this study).…”

Section: Estimation Of the Timing Of Fluid Circulationmentioning

confidence: 97%

Influence of local fluid flow on properties of low permeability Cretaceous siltstones (South-Eastern France): Implications for a nuclear waste deep repository

Rousset¹,

Lancelot²,

Verdoux³

et al. 2005

Journal of Geochemical Exploration

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Role of the Sardic tectonic phase in the metallogenesis of SW Sardinia (Iglesiente): lead isotope evidence

Cited by 10 publications

References 0 publications

Comparative geochemical study on Furongian–earliest Ordovician (Toledanian) and Ordovician (Sardic) felsic magmatic events in south-western Europe: underplating of hot mafic magmas linked to the opening of the Rheic Ocean

Comparative geochemical study on Furongian–earliest Ordovician (Toledanian) and Ordovician (Sardic) felsic magmatic events in south-western Europe: underplating of hot mafic magmas linked to the opening of the Rheic Ocean

Mercury (Hg) mineral evolution: A mineralogical record of supercontinent assembly, changing ocean geochemistry, and the emerging terrestrial biosphere

Influence of local fluid flow on properties of low permeability Cretaceous siltstones (South-Eastern France): Implications for a nuclear waste deep repository

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