O Depósito Potassífero de Autazes no contexto estratigráfico da Bacia do Amazonas

Abstract

The Autazes Potash Deposit, with more than 767 Mt and average grade of 30.71% of potassium chloride (KCl), corresponds to a sub-horizontal mineralized horizon located in the upper strata of the Nova Olinda Formation, from Pensilvaniana-Permian Sequence of Amazon Basin. This study reports the mineralogical-geochemical, stratigraphic and petrographic features of the potash mineralization, based on the database obtained by Potássio do Brasil Ltd. during a mineral exploration campaign for potash salts undertaken from the years 2008 to 2014, in Autazes region, Amazonas State, Brazil. These data indicate that mineralization covers an area of 155 km2, with an average thickness of 2.07 m and lies at depth from 685 m to 865 m. The mineralized horizon was subdivided from bottom to top as: 1) Lower Mineralized Interval, with predominance of white, fine and laminated sylvinites; 2) Intermediate Mineralized Interval,which mainly presents brown sylvinite and disseminated sulphates; 3) Upper Mineralized Interval, consisting of reddish coarse sylvinites. The KCl content and thickness distributions of the mineralization are related to the distinctive features of these sections along the deposit.