Luc Siebenaller

Cenozoic tectonic evolution of Naxos Island through a multi-faceted approach of fission-track analysis

Abstract New zircon and apatite fission-track ages obtained on samples from all lithotectonic units exposed on Naxos Island are presented. Zircon ages of the exhumed metamorphic rocks range from 25.2 to 9.3 Ma and from 13.0 to 6.4 Ma for apatite. Zircon track-length analysis distinguishes partial overprinting of an earlier event (M1) in the south. Northwards no overprint is seen and the ages there represent rapid exhumation since c. 12 Ma. Both zircon and apatite ages are slightly older toward the north of the island probably due to variation of the geotherm in the proximity of the fault. Zircon fission-track ages of the granodiorite range from 13.7 to 12.2 Ma are statistically identical to previously determined U–Pb ages. Apatite fission-track ages however, yield a younging trend from south to north from 12.9 to 9.0 Ma. This could be due to differential depth of emplacement and/or to differential exhumation during tectonic unroofing by a top-to-the north detachment. Fission-track ages on detrital grains in Lower Miocene sediments indicate a source not identified within the present outcropping rocks of Naxos. Ages on boulders and grains in the Middle to Upper Miocene sediments point to rapid erosion until about 8.5–7 Ma.

The Paleoproterozoic Copper‐Gold Deposit of Gaoua, Burkina Faso: Evidence for A Polyphased Mineralization

Due to increasing gold prices, gold exploration has intensified in the last 10 years, especially in the West African craton where many propects exist. Among these, the three copper-gold occurrences Dienemera, Gongondy and Mont Biri, of the Gaoua district (B2Gold), southern Burkina Faso, are thought to be part of a porphyric system (Sillitoe, 2007) but have not been so far subjected to detailed studies to confirm this hypothesis. This study presents mineralogical and fluid inclusion data for the mineralization and associated gangue phases that allow us to propose a metallogenic model for the formation of the Gaoua copper-gold system. In addition, the age of the mineralizing event was determined by Re-Os dating of sulfides.