CHEMICAL AND STRUCTURAL CONSTRAINTS ON THE PAIOL GOLD DEPOSIT, ALMAS GREENSTONE BELT, BRAZIL

Abstract

This paper presents new structural, chemical and fluid inclusion data for the volcanic sequences of the Almas greenstone belt (AGB), Tocantins State. The volcanic rocks were metamorphosed up to amphibolite facies, during a regional tectono-metamorphic event (DN ) and then retrogressed to greenschist facies assemblages along with later hydrothermal alteration, associated to sinistral strike-slip shear zones (D|i+|). Chemical composition of the rocks of the volcanic sequence show that it has continental affinity, probably related to a continental rift environment. In the Paiol gold mine of AGB the mineralized zones are associated with metabasaltic rocks. A detailed structural study shows that the gold mineralization can be related to the intersection of penetrative SN+1 mylonitic foliation with extensional faults (SN+2 A filling open spaces in transtension zones through which hydrothermal fluids passed resulting in ore shoot zones. INTRODUCTION