Alteration and fluid characteristics of a mineralised shear zone in the Lower Palaeozoic of the Anglo-Brabant belt, Belgium

In the Lower Palaeozoic rocks of the Brabant Massif (Belgium), a recently d iscovered polysulphide mineralisation is intimately related to a high strai n zone. Data from drillings, completed with outcrop data allow a detailed i nvestigation of mineralisation, alteration and fluid characteristics of thi s high strain zone, currently interpreted as a low-angle reverse shear zone and attributed to the main Early to early Middle Devonian Acadian deformat ion event. Ore mineralisation occurred synkinematically and was closely ass ociated with the shear zone. I,ow saline H2O-CO2(-CH4)-NaCl fluids with tem peratures >260 degrees C were involved in the hydrothermal circulation, whi ch caused alteration of the host rock and extensive sericidsation in the sh ear zone. Isotope data and the general setting indicate a metamorphic-drive n system. (C) 2000 Elsevier Science B.V. All rights reserved.