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Mineralogic Data and Geochemical Characteristics of the Berrahal Banded Iron Formations (Edough Massif. NE of Algeria)

  • Bachir HenniEmail author
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Part of the Advances in Science, Technology & Innovation book series (ASTI)

Abstract

The aim of this work is to characterize Berrahal magnetite ± hematite deposits, which are located in the southern area of the Edough massif. The ore bodies appear in the form of iron lenticular stratiform layers with a calcitic or calc-silicate global composition, and are hosted in kyanite-staurolite-garnet schists. The main minerals of the ore bodies are magnetite, hematite, siderite, quartz, calcite, fayalite, hedenbergite and garnet (almandine). Three types of facies can be distinguished on petrographic and geochemical observations: The first facies designated Mc corresponds to a carbonate ore. This ore is characterized by a carbonate gangue with alternating layers of calcite and calcite + magnetite. Siderite is sporadically present. Quartz is also present. The second facies, Ms, is a silicate ore characterized by a fayalite and hedenbergite gangue. Amphibole occurs as ferroedenitic to hastingsitic hornblende, while garnet is present as almandine. The third facies, denoted Mi, is considered as intermediate facies because of its lower silica content compared to that of Ms. The gangue consists of olivine and calcite, with some intercalated calcitic bands. Calcite and fayalite are at equilibrium. The early minerals are affected by Mn+2 metamorphism expressed by a N130-140 lineation on the surface of ore bodies, and a concordant foliation with hosting micaschists. The geochemical data show that the deposits of Berrahal correspond to a mixing in variable proportions, of a chemical iron-calcic pole with a pelitic detrital pole or volcano-sedimentary origin (mixing of iron-calcic pole with a volcano-sedimentary pole). The ore bodies are located at several sites and petro-geochemical similarities of Berrahal banded iron formations suggest that regional extent of mineralization is inherited from protolithes of sedimentary or volcano-sedimentary nature, which were subsequently transformed by regional isochemical metamorphism.

Keywords

Berrahal Edough Massif BIF Magnetite Metamorphism Metasedimentary 

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© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.Sciences Department, High School of TeachingEcole Normale Supérieure (ENS- Kouba)AlgerAlgeria

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