LP-HT anatectic processes and lithological heterogeneity in the Mindelo Migmatite Complex (NW Portugal)

M Areias,A Dória,M A Ribeiro,J F Santos

doi:10.3989/egeol.41730.323

Abstract

The Mindelo Migmatitic Complex crops out in the coastal zone north of Porto (Portugal) and consists of a set of migmatitic and granitic lithologies. Field relationships, petrography, geochemistry and isotopic signature of the various lithologies allow inferring the sequence of anatectic processes that resulted in their characteristic lithological heterogeneity. The metasedimentary sequences (Schist-Greywacke Complex) show chemical composition and isotopic signature identical to the metatexites. So is suggested to be the protolith of Mindelo Migmatite Complex lithologies. The melting has occurred in several structural levels and thus at different pressure and temperature conditions, resulting in rocks with specific characteristics. In shallow levels ( 3 ). The several pulses of different fluids that affected the Mindelo Migmatitic Complex probably are related to the emplacement of the syn and late- D3 variscan granites. The Mindelo Migmatite Complex represents an example of migmatites formed in low pressure conditions and illustrates some of the reactions involving melting in high grade pelitic rocks and subsequent mineral alterations due to infiltration of late different fluids.

Highlights

Geological settingThe Mindelo Migmatite Complex (MMC) is a migmatite massif associated with a syn-orogenic granite in the western border of the Central Iberian Zone (CIZ), the axial zone of the Iberian Variscan Orogen (Fig.1A)
This paper aims to infer the protolith and sequence of anatexis processes that gave rise to the migmatization and production of various granitic rocks that crop out in Mindelo Migmatitic Complex based on field relationships, petrography, geochemistry and isotopic signature
The isotopic composition of the MMC samples, compared with the values obtained by other authors for the granitic and metasedimentary rocks of the CIZ in the diagram εSr325 versus εNd325 (Fig. 7A), show that the Schist-Greywacke Complex (SGC) schists of the Group I coincide with the values found by Beetsma (1995) for Beiras Group (SGC.bg)

Summary

Introduction

Geological settingThe Mindelo Migmatite Complex (MMC) is a migmatite massif associated with a syn-orogenic granite in the western border of the Central Iberian Zone (CIZ), the axial zone of the Iberian Variscan Orogen (Fig.1A). In the Variscan Belt the metamorphism occurred mostly under low pressure and high temperature (Martínez et al, 2001; Valle Aguado et al, 2005; Ribeiro et al, 2008; Catalán et al, 2014). In CIZ the high-grade rocks, belonging mainly to the Schist-Greywacke Complex (SGC), are associated with peraluminous granitic plutons and anatectic complexes, materializing thermal domes developed in a late stage of the Variscan Orogeny (Escuder Viruete et al, 1994; Martínez et al, 2001; Bea et al, 2003; Valle Aguado et al, 2005; Ribeiro et al, 2008; Catalán et al, 2014). This paper aims to infer the protolith and sequence of anatexis processes that gave rise to the migmatization and production of various granitic rocks that crop out in Mindelo Migmatitic Complex based on field relationships, petrography, geochemistry and isotopic signature

Objectives

Discussion

Conclusion