Geotectonic significance of the textural evolution of fluid inclusions in Precambrian quartz veins from the "Boutonniere de Zenaga" (Anti-Atlas, Morocco)

In the Precambrian Zenaga inlier (boutonniere) in the Anti-Atlas of Morocco , many quartz veins crosscut the Ebournian (Precambrian) basement. The quar tz veins predate the deposition of the overlying Precambrian III units, and were probably the feeding channels for the overlying jasperoid formation. The fluid inclusion microthermometry and textural studies show the evolutio n in a single crystal, from intensely recrystallized inclusions to almost u ntouched ones recording the uplift of the Ebournian basement. The uplift pr ovoked the over-pressure of the inner fluid inclusions and their "explosion ", giving rise to "hook-like" or "decrepitation cluster" textures, while th e fluid inclusions located in the outer zones only show necking-down phenom ena. (C) 2000 Elsevier Science B.V. All rights reserved.