Redalyc.New Constraints on the Origin of the Ophiolitic Rocks Within Sin
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Geologica Acta: an international earth science journal ISSN: 1695-6133 [email protected] Universitat de Barcelona España Mazzeo, F.C.; De Vita, P.; Aulinas, M.; Arienzo, I.; Cirillo, G.; Iovine, R.S.; Sparice, D. New constraints on the origin of the ophiolitic rocks within sin-orogenic turbiditic sequences at Cilento region (southern Italy) Geologica Acta: an international earth science journal, vol. 14, núm. 3, septiembre, 2016, pp. 299-314 Universitat de Barcelona Barcelona, España Available in: http://www.redalyc.org/articulo.oa?id=50547614005 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative Geologica Acta, Vol.14, Nº 3, September 2016, 299-314 DOI: 10.1344/GeologicaActa2016.14.3.6 New constraints on the origin of the ophiolitic rocks within sin- orogenic turbiditic sequences at Cilento region (southern Italy) F.C. MAZZEO1 P. DE VITA1 M. AULINAS2 I. ARIENZO3 G. CIRILLO1 R.S. IOVINE4 D. SPARICE1 1Dipartimento di Scienze della Terra, dell’Ambiente e delle Risorse, Università degli Studi di Napoli Federico II Largo S. Marcellino 10, 80134 Napoli, Italy Mazzeo E-mail: [email protected] 2Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Geologia, Universitat de Barcelona (UB) Martí i Franquès s/n, 08028 Barcelona, Spain 3Istituto Nazionale di Geofisica e Vulcanologia, sezione di Napoli Osservatorio Vesuviano Via Diocleziano 328, 80124 Napoli, Italy 4Geowissenschaftliches Zentrum, Georg-August-Universität Goldschmidtstraße 1-3, D37077 Göttingen, Germany ABS TRACT Mafic igneous rocks (pillow lavas and gabbros) embedded as olistoliths within Miocene turbiditic sequences crop out in the Cilento area at the Mount Centaurino (Campania region, Southern Italy). The concentration of major oxides, as well as trace element ratios (Nb/Yb, Nb/Ta, Th/Nb) and the chondrite-normalized Rare Earth Elements (REE) patterns suggest a tholeiitic character with Mid Oceanic Ridge Basalts (MORB) affinity. The chemical composition of pillow lavas is consistent with magmas generated by 10% degrees of non-modal fractional partial melting, of a spinel-bearing MORB-type asthenospheric mantle. Regarding gabbros, the calculated composition of parental melts in equilibrium with the clinopyroxenes show a wide compositional range, and there are very different from the pillow basalts of the Mount Centaurino, suggesting that the clinopyroxenes might have derived from more evolved melts compared to those that produced the basalts. The origin of these olistoliths is not yet understood. Here we suggest that these rocks represent fragment of a dismantled accretionary wedge embedded during the deposition of the Cilento group sedimentary successions in a thrust top basin. KEYWORDS Southern Apennine. Cilento region. Mount Centaurino. Ophiolitic olistoliths. MORB-type rocks. INTRODUCTION original compositions (continental margin and mid-ocean ridge settings). The Jurassic ophiolites of the Alps and Ophiolites are the remnants of ancient oceanic Apennines represent fragments of a slow to ultra-slow lithosphere tectonically emplaced onto continental spreading oceanic basin named Ligurian, Piemonte- margins (Dilek and Furnes, 2014). According to these Ligurian or Alpine Tethys, (e.g. Beccaluva et al., 1984; authors, there are ophiolites that bear geochemical and Rampone and Piccardo, 2000; Piccardo et al., 2004; petrographic evidences of interaction with subduction- Piccardo, 2008; Tortorici et al., 2009; Vignaroli et al., related melts (suprasubduction zone setting), while in 2009; Vissers et al., 2013), located between the southern other cases there are lithologies in ophiolites resembling paleo-European continental margin and the western 299 F.C. Mazzeo e t a l . Petrology of Mount Centaurino ophiolitic rocks margin of the Adria Plate (Stampfli and Hochard, 2009, and sandstones of the Val Marecchia Nappe in northern and references therein), that were obducted, with different Italy (Perrone et al., 2014). In southern Italy, the presence polarity on continental crust during its closure (Bortolotti of basaltic igneous rocks, intercalated/embedded into the and Principi, 2005; Dilek and Furnes, 2011). They occur in Miocene succession of terrigenous turbidites, cropping out scattered outcrops located mainly in the Alps and northern in the Cilento area (Campania) at Mount Centaurino and Apennines (Piccardo et al., 2014, and references therein). subordinately at Mount Sacro (Fig. 1A-B), is well known for In thesouthern Apennines they only crop out in southern more than fifty years (Ietto and Cocco, 1965; Cocco and Di Basilicata and northern Calabria (Beccaluva et al., 1983; Girolamo, 1970; Dietrich and Scandone, 1972; Di Girolamo Spadea, 1994; Liberi et al., 2006; Cristi Sansone et al., 2011; et al., 1991). Various interpretations about their geochemical Mazzeo et al., 2014). The northern Apennines ophiolitic affinity, their stratigraphic/tectonic relationships with massifs show widely variable lithological associations, the surrounding sedimentary rocks, and, therefore, their textural, geochemical and mineralogical features, reflecting geological significance have been proposed in literature. variable histories of petrological evolution undergone during Based on field evidence, especially on a presumed the opening of the Ligurian Tethys (Rampone and Piccardo, metamorphic contact between igneous and sedimentary 2000). For this reason they are divided into in peri-continental rocks, and biostratigraphic data, Cocco and Di Girolamo (marginal) and intra-oceanic (distal) ophiolites on the basis (1970) considered these igneous rocks as the product of a of their inferred paleogeographic position (Rampone et al., hawaiitic volcanic activity occurred simultaneously to the 2014, and references therein). In some cases, the oceanic turbidite sedimentation. This idea was re-proposed by Amore lithosphere has been partially preserved not only in ophiolitic et al. (1988) who hypothesized a link between these igneous massifs, but also as olistoliths enclosed in terrigenous/ rocks and the synorogenic magmatism recorded in the Betic carbonatic sedimentary units, like the Oligocene breccias Cordillera and African Maghrebides. However we want to Va 15°2' Naples 50 km A Mt. Chianello llo B Agropoli d i Dia Alento river n o 40°32 Salerno Mt. Cervati ' Tyrrhenian Sea Mt. Stella 100km 42° Mt. Sacro Mt. Centaurino 40° 40°10' Ascea r N Tyrrhenian Sea 12° 16° 15°55' Lambro rive Mt. Sacro Fm. Quaternary Volcanic deposits Lagonegro Basin deposits (Upper Tortonian) Sapri Mt. Bulgheria Plio-Quaternary sedimentary deposits Apennine Platform carbonates Cilento Group (Upper Burdigalian-Lower Tortonian) Miocene Wedge-top Basin deposits Apulian Platform carbonates Nord Calabrian/Parasicilide Units N (Upper Cretaceous-Burdigalian) 10 km Liguride Units Carbonate Platform (Triassic-Langhian) Mt. Sacro Fm. C N 500m D San Mauro Fm. San Mauro Fm. ortonian) Pillow lavas Pollica Fm. Lower Albidona Fm. Olistostrome Upper Cilento Group (Burdigalian-T Olistostrome Albanella Fm. Mt. Centaurino t (1433m asl) 0 90 Saraceno Fm. 1300 1000 800 1200 celle No 0 elle 70 Mt. Sant’Arcangelo Fm. Scanno d 100 1 Debris 0 60 Upper Jurassic-Burdigalian) Crete Nere Fm. Nord-Calabrese Uni ( Postigione Fm. Rupe di San Paolo Gabbros FIGURE 1. A) Tectonic sketch map of southern Apennines (redrawn after Vitale et al., 2011); B) geological sketch map of the Cilento area (redrawn after Vitale et al., 2011); C) sketch showing stratigraphic relationships of the different tectonic units cropping out in the Cilento area (modified after Vitale et al., 2011); D) simplified geological map of Mt. Centaurino, showing all investigated outcrop locations. Geologica Acta, 14(3), 299-314 (2016) 300 DOI: 10.1344/GeologicaActa2016.14.3.6 F.C. Mazzeo e t a l . Petrology of Mount Centaurino ophiolitic rocks point out that the only hawaiitic volcanism with anorogenic Complex (LAC), Ciarcia et al., 2009). During the orogenic geochemical characteristics of SE Spain occurs at the Tallante- phases, these units overthrust the outer carbonate platform Cartagena area, and has been dated at ~2.3–2.9Ma (Duggen domain to the East, and were unconformably covered by et al., 2005), much later than the main orogenetic phases. the wedge-top uppermost Burdigalian-lower Tortonian The same situation is found in the Moroccan and Algerian turbidite flysch of the Cilento group (Bonardi et al., 1988, Maghrebian Chain, where the anorogenic products, mostly 2009), the Tortonian Piaggine sandstones (Sgrosso, 1981) with sodic alkaline affinity, are late Miocene–Quaternary in and the upper Tortonian Monte Sacro Formation (Selli, age (Coulon et al., 2002; Duggen et al., 2005). A completely 1962). The igneous rocks of Mt. Centaurino are embedded different scenario is that proposed by Dietrich and Scandone into the Langhian-lower Tortonian San Mauro Formation, (1972) who found no evidence of contact metamorphism forming the upper part of the Cilento group turbidite series. between the Mt. Centaurino igneous rocks and the turbidite At this site, pillow lavas, hyaloclastites and pillow breccias series, and proposed that they were ophiolitic olistoliths. form an apparently discordant outcrop because they cut Based on petrographic and geochemical data, Di Girolamo the bedding of the succession (Fig. 2A, B, C). These field