Contrasting styles of metamorphic to metasomatic deposits of gemstones in Cabo Delgado, northern Mozambique

Abstract

[Excerpt] From a conceptual point of view, in some ruby and garnet deposits of the Lalamo Supergroup (LL) – Cabo Delgado Nappes Complex, Northern Mozambique – the structural control of the primary mineralization seems to be spatially and geochemically related to the genesis of calcsilicate rocks, also with gemstones. In LL the widespread gneisses are predominantly felsic to intermediate. They occur at lower tectono-stratigraphic levels but were segmented, indented or carried over other formations. The main lithologies correspond to meso-crustal components. The metamorphic features vary from low grade to amphibolite and granulitic facies. The contiguity of these formations is attributed to tectonic transport and carriage overlap.