Composite grains in Maas (Meuse) sediments: a survey and a discussion of their opaque components

Abstract

The opaque mineralogy of composite grains in acid-treated heavy-mineral concentrates from sediments of the river Maas (Meuse) was studied in reflected light and by SEM-EDXRA analysis. Secondary rutile, secondary ilmenite and hematite constitute the subtranslucent to opaque matter in these composites, which principally represent actual rock fragments. This suggests that the sediments investigated contain products of rather freshly disintegrated rocks. The opaque components enable two important groups of rock fragments to be distinguished: a major group characterized by secondary rutile, secondary ilmenite and their intergrowths; and a minor group with exclusively hematite.