Influencia de la mineralogía y del metamorfismo en las propiedades magnéticas de los depósitos alpinos cromoespinelíferos. El Complejo Los Guanacos, Pcia. de Córdoba

MUTTI, D.; GONZÁLEZ CHIOZZA, S.; GEUNA, S. E.; DI MARCO, A.

La Plata

Congreso; Congreso de Mineralogía y Metalogenia; 2000

This paper describes preliminary results about the mineralogy andmagnetic properties of Los Guanacos ultrabasic complex, its host-rock and itsore deposits in a serpentinized matrix. Effects of metamorphism on mineralogyand magnetic properties are discussed. The data support the presence offerromagnetic minerals within the serpentinised ultrabasic complex, whichdisplays bulk susceptibilities ranging between 1 x10-3 and 1x 10-1 (SI), anddefine a broad positive magnetic anomaly related to arborescent secondarymagnetite. The , Mg - Al chromite deposits, typical of alpine magmatic process,are defincd by paramagnetic chromite, showing low susceptibility values, around1 x10-3 , and no conclusive anomalies were found. The high amphibolite togranulite superimposed metamorphic conditions determined two deposit types inthe complex: 1) chromiferous magnetite and ferrian chromite ore, that iscomposed by ferromagnetic minerals, showing the highest susceptibility, around 1x10-1 ; 2) Al - Fe - Mg - Cr - Ti spinel ore, composed by ferromagnetic andparamagnetic minerals, showing variation of the magnetic properties,susceptibility values around 1 x 10-2 ; both 1) and 2) define short wavelenght,high amplitude anomalies. Retrograde metamorphism from amphibolite togreenschist facies determined the formation of ferrichromite rims in chromitegrains together with secondary magnetite and produces conclusive anomaliesassociated to heterogeneous magnetic properties.