Metamorphic evolution and P–T path of the Posada Valley amphibolites: new insights on the Variscan high pressure metamorphism in NE Sardinia, Italy

Massimo Scodina,Marcello Franceschelli,Gabriele Cruciani

doi:10.5802/crgeos.65

Abstract

Metamorphic evolution and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>P</mml:mi></mml:math>–<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>T</mml:mi></mml:math> path of the Posada Valley amphibolites: new insights on the Variscan high pressure metamorphism in NE Sardinia, Italy

Highlights

Retrogressed eclogites are widespread in the internal zone of the Variscan chain of Sardinia within the low- to medium-grade metamorphic complex (L-MGMC) and in the high-grade metamorphic complex (HGMC) [ known as migmatite complex; Carmignani et al, 2001]
In this paper we present a detailed petrological investigation of the Posada Valley amphibolites in order to reconstruct their metamorphic history and P
Selected samples were cut in thin slices and pulverized for major elements whole-rock analyses, which were performed at ALS-Laboratories (Seville) by X-ray fluorescence (XRF) after lithium-borate fusion

Summary

Introduction

Retrogressed eclogites are widespread in the internal zone of the Variscan chain of Sardinia within the low- to medium-grade metamorphic complex (L-MGMC) and in the high-grade metamorphic complex (HGMC) [ known as migmatite complex; Carmignani et al, 2001].In the high-grade metamorphic complex hectometre-size lenses of eclogites crop out at Golfo Aranci, Punta Tittinosu, and Punta de li Tulchi (Figure 1(a)). Eclogites of the HGMC are characterized by the occurrence of omphacite relics. Only the metabasite rocks from Giuncana [Cortesogno et al, 2004, Cruciani et al, 2015a] preserve true relics of eclogite facies assemblages (i.e., ISSN (electronic) : 1778-7025 https://comptes- rendus.academie- sciences.fr/geoscience/. The other metabasites from the L-MGMC are still considered eclogites, as well, due to their position along the Posada–Asinara shear zone (Figure 1(a)). The protoliths of Sardinian eclogites are mostly midocean ridge basalt (MORB)-type tholeiites [Cappelli et al, 1992], with the exception of the metabasite from Punta Orvili that exhibits an alkaline affinity [Cruciani et al, 2010], considered by many authors as part of the oceanic crust subducting under the peri-Gondwanan terranes (previously accreted to Laurussia) during the Variscan orogeny

Methods

Findings

Discussion

Conclusion