Geochemistry and petrology of plagiogranites in the ophiolites from the Pollino Massif (Southern Italy): Origin and tectonic significance

Abstract

In the ophiolitic sequences, are widespread low potassium albite-rich granite, trondhjemite, tonalite and granodiorite (e.g. Coleman & Peterman, 1975; Koepke et al., 2007). Concerning the Tethyan realm, plagiogranites have been recognized as dikes and beds in the ophiolithic rocks of the western Alps, in Corsica, and in the northern Apennines (Borsi et al., 1996; Castelli et al., 2002; Montanini et al., 2006). Also if the oceanic plagiogranites are volumetrically minor in the ophiolitic sequences, their origin has been largely debated due to importance of these rocks to understand the Earth’s continental lithosphere evolution of (Marien et al., 2019). Several authors (Beccaluva et al., 1999; Floyd et al., 2000; Niu et al., 2002; Rao et al., 2004; Berndt et al., 2005; Dylek & Thy, 2006) proposed that the plagiogranites are the products of fractional crystallization of mid-ocean ridge basalt (MORB) magma at low pressures conditions including, for instance, those exposed in the Oman, Cyprus, Serbia and Turkey ophiolitic sequences (Dylek and Furnes, 2011; Milovanovic et al., 2012; Kocsal et al., 2017; Marien et al., 2019). Others Authors (Koepke et al., 2004; 2007) have suggested an origin by partial melting (i.e. anatexis) of cumulate gabbro (Koepke et al., 2004; Brophy, 2009; Brophy & Pu, 2012). A further model suggests that plagiogranites formed through the interaction of immiscible liquids with mafic solutions (Floyd et al., 2000; Kiliç, 2009). Geochemical studies (Koepke et al., 2007; Brophy 2009) stated that the distribution of some elements, including SiO2, TiO2, and REE, can be used in order to distinguish among these different processes. The aim of this research is to characterize for the first time, with a petrological and geochemical study, the plagiogranites from the ophiolitic rocks of the North Calabria Unit of Pollino Massif and to discuss their origin and geodynamic significance. We also compare the geochemical data of these plagiogranites with those of Western Alps (Castelli and Lombardo, 2007) and Northern Apennines (Borsi et al., 1996; Montanini et al., 2006) and with further Mediterranean plagiogranites such as Turkey (Koksal et al., 2017), Cyprus (Marien et al., 2019), Serbia (Milovanovic et al., 2012) and Oman (Dylek and Furnes, 2011). The results of this work will provide new contributions and constaints about the geodynamic evolution of the Tethyan realm.