Investigation of microstructures and mineral growth in olivines from Flores and Corvo Islands - Portugal

Essay on crystallochemistry variation and mineralogenesis.

Abstract

In this study the authors investigate crystallochemical variations and the mineralogenesis of magmatic olivines from volcanic rocks of the islands Flores and Corvo, Archipelago of the Azores-PT. This investigation is carried out by means of scanning electron microscopy and x-ray diffraction with dispersive energy-EDX and aspects of microstructures and chemical signatures registered during the formation of olivines are analyzed. Having knowledge of the rheological characteristics of this mineral, which transcend average pressures from 0.3 to 15 GPa and depths of 400 km, olivines are the key to understanding the dynamics of the upper mantle. Thus, this study makes possible the discussion about the petrogenetic and crystallochemical processes active in the formation of these olivines and, consequently, of the volcanic rocks of the Flores and Corvo islands. Therefore, we discuss here the differentiated processes to which these minerals were subjected, and which remained imprinted in their chemical composition and morphology, such as magmatic fractionation, variations in pressure conditions and, also, temperature for rocks and other products of the two islands of the Azores Archipelago.