An International Journal of Chemistry and Mineralogy of Early Mesozoic
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Per. Mineral. (2000), 69, 1, 19-34 An InternationalJournal of � � PERIODICO di MINERALOGIA MINERALOGY, CRYSTALLOGRAPHY, GEOCHEMISTRY, established in 1930 ORE DEPOSITS, PETROLOGY, VOLCANOLOGY and applied topics on Environment, Archaeomet1y and Cultllral Heritage Chemistry and mineralogy of early Mesozoic pelite layers from continental red beds « Verrucano», Peloritani Mountains, Sicily, Italy PAOLA DI LE01*, GIOVANNI MONGELLI2, SALVATORE CRITELLI\ Rocco LAVIANO\ EMILIA LE PERA3 and VINCENZO PERRONE5 1 C.N.R. Istituto di Ricerca sulle Argille, Via S. Loja-Area Industriale, 1-85050 Tito Scalo (PZ), Italy 2 Centro di Geodinamica, Universita della Basilicata, Via N. Sauro, 1-85100 Potenza, Italy 3 C.N.R. Istituto di Ricerca per la Protezione Idrogeologica nell'Italia Meridionale ed insulare, Via Cavour, I-87030 Roges di Rende (CS), Italy 4 Dipartimento Geomineralogico, Universita di Bari, Via E. Orabona, I-70124 Bari, Italy 5 Istituto di Geologia, Universita di Urbino, Localita Crocicchia, I-61029 Urbino (PS), Italy Submitted, July 1999- Accepted, February 2000 ABSTRACT. - Mineralogical and chemical data on RIASSUNTO. - Nel presente studio sono riportati i eight pelites and two metapelites from the Upper primi dati mineralogici e geochimici delle peliti e Triassic to Lower Jurassic continental sedimentary metapeliti appartenenti alle successioni continentali sequences of the Peloritani Mountains, Sicily, are del Triassico superiore-Giurassico inferiore che reported. In both sediments and metasediments caratterizzano le coperture alpine, talune studied, the mineralogical assemblage is dominated epimetamorfiche, di alcune falde a basamento by illite that prevails over kaolinite and chlorite. cristallino dei Monti Pelori-tani (Sicilia nord Chemical data suggest that a significant diagenetic orientale). L' associazione mineralogica riconosciuta control on the distribution of clay minerals can be sia nelle peliti che nelle metapeliti e dominata excluded. The overall mineralogical features suggest dall'illite che prevale sulla caolinite e sulla clorite, derivation from a source area mostly composed by quest'ultima presente in tracce. La composizione low- and medium- grade metamorphic terrains. The chimica nel suo complesso suggerisce 1' assenza, nei higher kaolinite and hematite abundance in the sedimenti studiati, di rilevanti modificazioni metasediments with respect to pelites, suggests diagenetiche. L' associazione mineralogica indica derivation from a more weathered source. che tali sedimenti provengono da un'area sorgente Metapelites underwent condition of P-T typical of prevalentemene composta da terreni metamorfici di low-grade metamorphism (anchizone) as indicated basso e medio grado. Nelle metapeliti, la presenza in by the occurrence of pyrophyllite, likely deriving quantita piu elevate di caolinite ed ematite form the reaction involving kaolinite and quartz. suggerisce un' origine da una area sorgente che ha subito un piu alto grado di weathering. Le condizioni di P e T che hanno interessato le peliti metamorfosate sono quelle tipiche del metamorfismo di basso grado (anchizona) come * Corresponding author, E-mail: [email protected] testimoniato anche dalla presenza di pirofillite. 2 = E-mail: [email protected] 3 = E-mail: [email protected] KEY WORDS: 3 = E-mail: [email protected] Continental Redbeds; Early Mesozoic; 4= E-mail: Rocco.Laviano@geo min.uniba.it Sicily; pelite and metapelite; low-grade 5 = E-mail: [email protected] metamorphism. 20 P. DI LEo, G. MoNGELLI, S. CRITELLI, R. LAVIANO, E. LE PERA and V. PERRONE INTRODUCTION Jurassic (Baudelot et al., 1988) continental redbeds (conglomerate, sandstone and pelite; The Peloritani Mountains, the south-western Colacicchi, 1960; Colacicchi and Filippello, end of the Calabrian Arc, are formed by a stack 1966; Lentini, 1975; Lentini and Vezzani, of Alpine nappes thrusted, during the Miocene, 1975; Bonardi et al., 1976; Gelmini, 1985) onto Meso-Cenozoic terrains, sedimented in showing the typical facies of the «Verrucano», the Maghrebian Flysch Basin Domain (Bonardi which represents the base of the Alpine cycle et al., 1976 and references therein). The in some domains of both northern Apennines tectonic boundary between these two different and Alps (Rau and Tongiorgi, 1974; Cassinis et domains is recognizable in the so-called al., 1979; Martini et al., 1986). The Tuscan «Taormina line» (fig. 1). « Verrucano», Triassic in age, outcrops in Some Peloritanian nappes only consist of a discontinuous patches throughout the entire pre-Alpine crystalline basement (Fondachelli lenght of the northern Apennines. It and Aspromonte Units), others include also a experienced a wide range of P-T conditions, Meso-Cenozoic sedimentary cover (Longi linked to the Alpine metamorphism, and its Taormina, Mandanici and AB Units). compositive features have been extensively In these sedimentary covers the oldest strata studied (Franceschelli et al., 1986a, 1986b, are composed of upper Triassic-lowermost 1989; Giorgetti et al., 1998). In the northern TYRRHENIAN SEA � [[]5 09 ffi10 0 ......... W2 llm3s 03 �7 ----13 * 14 + � + + .. + 0:14 �8 10 J: + km + + 4-+ + + + + + Fig. 1 - Schematic geologic map of the northeastern Sicicly: 1) Plio-Quaternary; 2) Etna volcanics; 3) Lower Pliocene Upper Tortonian deposits; 4) Floresta Calcarenite Fm. (Lower Miocene) 5) High-grade metamorphics of the Upper Peloritanian nappes (Aspromonte and Mela Units; Pre-Triassic); 6) Ali Unit (Cretaceous-Triassic); 7) Sedimentary cover of the Lower Peloritanian nappes (Lower Miocene - Upper Triassic); 8) Low-grade metamorphics of the Lower Peloritanian nappes (Mandanici, Fondachelli, Longi-Taormina; Carboniferous-Cambrian); 9) Maghrebian Flysh Basin Units (Monte Soro, Troina-Tusa and Nicosia; Lower Miocene - Upper Triassic); 10) Maghrebian External Units (Panormide and Imerese; Middle Miocene - Middle Triassic); 11) Stratigraphic contacts; 12) Tectonic contacts; 13) Taormina Line; 14) Sampling localities. Chemistry and mineralogy of early Mesozoic petite layers from continental redbeds «Verrucano» ... 21 Apennines the « Verrucano» mineralogical Hettangian greyish continental and coastal assemblage is not necessarily in equilibrium as deposits (Baudelot et al., 1988). These deposits some facies are pre-metamorphic and others gradually pass vertically into developed during the Alpine stage of b) shallow-water limestone and dolostone, metamorphism. about 300 m in thickness, having a The continental redbeds characterizing the Hettangian(?) to Carixian age (Taormina Peloritanian nappes have been studied and Formation; Rigo and Barbieri, 1959); this sampled in all outcrops of the Peloritani carbonate platform facies pass into Mountains, along two WNW-ESE transects c) Pelagic limestone and grey marl 200-300 from the Tyrrhenian Sea to the Ionian Sea. The m in thickness and Carixian-Domerian in age, southern transect, from Sant' Agata di Militello passing into Toarcian-Bajocian ammonite-rich to Taormina (fig. 1), corresponds with the red marls ( «Ammonitico rosso inferiore»; unmetamorphosed outcrops of the Longi Lentini and Vezzani, 1975). This slope facies Taormina Unit, whereas the northern transect, pass into deep-water radiolarian chert, and from Capo Calava to AB, includes few cherty limestone, followed by new strata of outcrops of redbeds, affected by low-grade ammonite-rich marls ( «Ammonitico rosso metamorphism, whose tectonic appartenance is superiore»; Lentini and Vezzani, 1975), about still a matter of debate. 100 m in thickness and Bajocian to Tithonian In these two transects we sampled both in age. These terrains are followed by about unmetamorphosed and metamorphosed pelite 100 m thick Tithonian-Neocomian limestone strata for the compositional study. The present and marly limestone, and then by Cretaceous to paper focuses on the mineralogical and Oligocenic red, green and grey marls (Militello chemical (major and trace elements) features of Formation). The sedimentary succession is the pelite and metapelite layers and its PIT capped by the evolution. d) Turbidite quartzofeldspathic sandstone (Frazzano Formation) having a lower Miocene age (Aquitanian; de Capoa et 1997). GEOLOGICAL AND STRA TIGRAPHIC SETTINGS al., In the Longi-Taormina thrust sheets the The Mesozoic to Tertiary sedimentary continental redbeds are particularly thick (over sequences of the Peloritani Mountains nappes 200 m), whereas they are few meters in the rest unconformably on the pre-Alpine other areas. The Longi section shows Upper crystalline basement of the Longi-Taormina, Triassic lenticular conglomerate and sandstone AB and Mandanici units. The basements of strata, representing fluvial channel-fill, these units consist of low-grade metamorphics interbedded with thin layers of red clays. They (phyllite, metarenite, metalimestone and evolve into lower Hettangian yellow-white metavolcanic rocks) of Paleo zoic age (Majeste sandstone, clays and dolomite, showing the Menjaulas et al., 1986; Spalletta and Vai, 1989; transition from continental to marine deposits Messina et al., 1996). (figs. 2 and 3). The fluvial sandstones are The Longi-Taormina Nappe constitutes the quartzarenite to sublitharenite, with abundant lowermost thrust sheets in the Peloritanian quartz, low-grade metamorphic, felsic volcanic, nappe stack (fig. 1) and shows the most quartzite and chert lithic fragments, and extensive and complete Mesozoic to Cenozoic dominantly quartz cement. The transitional sedimentary successions, which include: sandstones are quartzarenite