Structure of the Castellaccio Pluton (Asinara Island, Italy)

Abstract

This paper illustrates the geological and structural map (scale 1:10,000) of the Castellaccio Pluton (Asinara island-Italy), a peraluminous granodioritic intrusion of Variscan age that belongs to the Corsica-Sardinia Batholith. This small pluton, about 15 km 2 , emplaced within Paleozoic amphibolite-facies rocks during the post-collisional exhumation of the chain. The map shows the fine details of the magmatic structure of the pluton. Field-structural survey, coupled with remote sensing and major-elements geochemical mapping, allowed to recognize the occurrence of five magmatic units and the magmatic flow trajectories within the pluton. These outcomes provide useful insights into the architecture of the magmatic system. The results presented improve substantially the cartographic database of the Variscan crust of Sardinia and, finally, may serve as a robust background supporting further studies on the emplacement mechanism, or targeted to more specific petrologic studies.

Weathering Products of a Dismantled Variscan Basement. Minero-Chemical Proxies to Insight on Cretaceous Palaeogeography and Late Neogene Palaeoclimate of Sardinia (Italy)

“…In present coordinates the tilting results toward the east; progressively older formations are therefore exposed toward the west. The oldest rocks crop out near the coast and comprise mainly phyllite with intercalated metarhyolite and metabasite of the Variscan basement, which northward, due to the prograde metamorphism, pass into gneiss, amphibolite, and anatectic granite (Oggiano and Mameli, 2006;Cuccuru et al, 2018). Late Permian and Mesozoic cover units are exposed along a hilly/flat area to the east of the basement.…”

Shallow geophysics of the Asinara Island Marine Reserve Area (NW Sardinia, Italy)

“…It includes the Corsica-Sardinia massif, which constitutes a microplate drifted away from Europe in the Oligocene (Alvarez, Cocozza, & Wezel, 1974). In Sardinia, the Variscan belt comprises three main tectonic domains: (1) a foreland belt consisting of Upper Cambrian-Lower Carboniferous sedimentary sequence; (2) a SW-verging stack of piled nappes formed by Paleozoic volcano-sedimentary sequences affected by thrusts and folds; (3) an inner zone, characterized by medium-to high-grade metamorphic rocks, and consisting of two different metamorphic complexes separated by the Posada-Asinara Line (Carmignani et al, 2001;Carmignani, Oggiano, Funedda, Conti, & Pasci, 2016;Carosi, Di Pisa, Iacopini, Montomoli, & Oggiano, 2004;Cuccuru, Casini, Oggiano, & Simula, 2018;Frassi, 2015). This tectonic lineament is a km-thick mylonitic belt (Cappelli et al, 1992;Elter, Musumeci, & Pertusati, 1990), which would be part of the South Hercynian Suture Zone between the Armorica and Gondwana continental margins (Cappelli et al, 1992).…”