rmotectonic controls of the locals mineralizations: a work hypothesis.

Abstract

The volumetric and morphological changes undergone by rock forming minerals due to their relative differencial thermal dilatation (contractional) coeficients are described as mineralization emplacement control. This way, the contrasting thermal dilatation data for quartz and felspar are reviewed by volumetric modeling the effect of a significant variation of −quartz transition arround 575°C. The proposed dilatation of the whole rock body resulting by this phenomena could range from 0.4 % for a granitoid with a poor quartz content to 1.2% for a tipically acid rock. Thus, the strong microtectonic changes resulting from these processes on acid rocks (granites to rhyolythes) are asumed to contribute to the generation, transport and spatial distribution of late magmatic mineralization fluids. As a working hypothesis, the thermal dilatation is proposed as an important factor controlling diseminated deposits (also pegmatites, greisen and skarn mineralization) as well as their coeval deformation mechanics during both increasing or decreasing temperature changes. Keywords: thermal expansion, structural control, ore emplacement, mineralizations.