Metallogenesis in the Brabant Massif: physico-chemical conditions and timing.

The drilling campaign, which started in 1996 at the initiative of the "Ministerie van de Vlaamse Gemeenschap" clearly confirmed the importance of the sulfide mineralisations in the Brabant Massif. A comparison which similar basement rocks in the British Isles and along the eatern coast of the U.S. helps to clarify the geological situation. Indeed, during the Acadian phase (about 390 MA ago) of the Caledonian orogeny several continental plates and platelets merged into a single land mass, the remnants of which are presently found on both sides of the Atlantic. The geotectonic evolution could thus be retraced in the great lines. However, the conditions of ore genesis remain to be precised, as well as the possible role of a postulated granitic pluton which, according to geophysic evidence, would extend at depth to the west of Brussels up to the coastal area. other possibilities are a relation with older ocanic arc magmatism or no relation at all with a magmatic event. The detail mineralogic and geochemical investigation will be carried out at the KUL, while the VUB team will take care of the datings. The age of the deposits can be brought in relation with its origin: arc magmatism (420 Ma), Acadian phase (390 Ma), late wrench faulting (370 Ma).