First report of occurrence of Mn-mineralization bearing rocks hosted in hoggar cenozoic felsic lavas, hoggar, Algeria

Abstract

For the first time in North Africa, a large field Mn-mineralization bearing felsic lava association is described and located. Significant deposits of manganiferous formations, mainly a potassic manganese dioxide associated with high K alkaline felsic lavas have been discovered in the Tuareg Shield, more specifically in the Aleksod volcanic district of the Central Hoggar. Micro-Raman spectroscopy, ore microscopy and electron microprobe investigations were used to identify the manganese oxide (mainly Mn-K). It was done using felsic ore samples from the Aleksod volcanic area. The most prevalent minerals in the host lavas are quartz, alkali feldspar, and magnesio-mica, with cryptomelane being the predominant manganese mineral in these samples. The chemical composition of the rocks is an indication that they are free from magmatic contamination. Replacement, fluid movement, leaching and precipitation are probably the most common ways in which post-magmatic manganese can be circulated. However, much of the ore appears to have been enriched by mineral leaching and subsequent addition of manganese. The presence of this manganese in the outcrop is a readily exploitable indicator of economic exploitation. These findings are sufficient to characterize the uniqueness of this first significant Mn observation in felsic lavas and confirm the geodynamic model involving a history of sedimentary basins from the late Proterozoic to the Cretaceous, ultimately interacting with Cenozoic volcanism in this part of the Hoggar.