ANCIENT OXIDE-MINERALIZATION AND SULFIDE-MINERALIZATION IN THE ISLANDS OF TENERIFE AND LA-GOMERA (CANARY ARCHIPELAGO, SPAIN)

The alkaline intrusive complexes of Tenerife and La Gomera (Canary Arc hipelago, Spain) are formed by nepheline syenites and alkali gabbroids , and represent part of the oldest magmatic episodes in both islands. This work presents new studies of the petrographic and geochemical fea tures of these rocks, and offers the first data about their respective ore minerals (iron oxides and sulphides). Mineralization is represent ed in both complexes by iron-rich patches and veins displaying a simpl e paragenesis of magnetite, ilmenite, pyrite and pyrrhotite, in associ ation with widespread chloritic alteration of the intrusive host rocks . The comparative study of the mineralogical, textural and chemical ch aracteristics of the ore minerals allows a metallogenetic model to be proposed which comprises two stages (magmatic and hydrothermal) in La Gomera and only one (magmatic) in Tenerife. The migration of the sulph ide-bearing hydrothermal fluids far from the intrusive complex in Tene rife, and/or possible re-melting process could explain the apparent ab sence of the later hydrothermal stage in Tenerife.