Metasediments Covering Ophiolites in the HP Internal Belt of the Western Alps: Review of Tectono-Stratigraphic Successions and Constraints for the Alpine Evolution

Paola Tartarotti,Gianni Balestro,Silvana Martin,Andrea Festa

doi:10.3390/min11040411

Paola Tartarotti, Gianni Balestro + Show 2 more

Open Access

https://doi.org/10.3390/min11040411

Copy DOI

Abstract

Ophiolites of the Alpine belt derive from the closure of the Mesozoic Tethys Ocean that was interposed between the palaeo-Europe and palaeo-Adria continental plates. The Alpine orogeny has intensely reworked the oceanic rocks into metaophiolites with various metamorphic imprints. In the Western Alps, metaophiolites and continental-derived units are distributed within two paired bands: An inner band where Alpine subduction-related high-pressure (HP) metamorphism is preserved, and an outer band where blueschist to greenschist facies recrystallisation due to the decompression path prevails. The metaophiolites of the inner band are hugely important not just because they provide records of the prograde tectonic and metamorphic evolution of the Western Alps, but also because they retain the signature of the intra-oceanic tectono-sedimentary evolution. Lithostratigraphic and petrographic criteria applied to metasediments associated with HP metaophiolites reveal the occurrence of distinct tectono-stratigraphic successions including quartzites with marbles, chaotic rock units, and layered calc schists. These successions, although sliced, deformed, and superposed in complex ways during the orogenic stage, preserve remnants of their primary depositional setting constraining the pre-orogenic evolution of the Jurassic Tethys Ocean.

Highlights

Ophiolites are a major component of the Alpine-Himalayan orogenic belt [1,2,3] (Figure 1A).They represent tectonic slices deriving from the oceanic lithosphere of the Jurassic TethysOcean and have been named Tethyan ophiolites [4,5])
We focus our study on the eclogite facies belt, and on the metaophiolites exposed in the Aosta Valley and in the Monviso Complex because, due to their weak re-equilibration during the Alpine decompression path, they preserve textural records of the pre-orogenic evolution and of the original geological setting
The meta-sedimentary tectono-stratigraphic successions here analyzed belong to the Alpine metaophiolites deriving from the closure of the Jurassic Tethys Ocean

Summary

Introduction

Ophiolites are a major component of the Alpine-Himalayan orogenic belt [1,2,3] (Figure 1A).They represent tectonic slices deriving from the oceanic lithosphere of the Jurassic TethysOcean and have been named Tethyan ophiolites [4,5]). We focus our study on the eclogite facies belt, and on the metaophiolites exposed in the Aosta Valley and in the Monviso Complex because, due to their weak re-equilibration during the Alpine decompression path, they preserve textural records of the pre-orogenic evolution and of the original geological setting. In this context, we concentrated our investigations on metasediments covering the metaophiolites, with particular attention to their pseudostratigraphic sequence and petrographic features

Methods

Discussion

Conclusion