Los Islands (Iles De Los)
The Los Islands are located just off the Guinea coast 5 km southwest of the capital Conakry. The archipelago comprises three major islands together with five islets.
Complete list of alkaline rocks and carbonatites
The Los Islands are located just off the Guinea coast 5 km southwest of the capital Conakry. The archipelago comprises three major islands together with five islets.
An area of aegirine-bearing granite gneiss is described by Obermuller (1941) from 1 km south-southeast of the village of Yoa. The paragenesis of this gneiss is not clear.
This is a peralkaline granite emplaced in Precambrian basement granites and schists. It contains perthitic microcline and aegirine. A photomicrograph is given by Arnould (1961). No other information has been traced.
The Ninakri complex is intruded into Precambrian schists and comprises two centres 1.5 km apart. The northern centre is composed dominantly of aegirine and aegirine-riebeckite syenite with minor micromonzonite.
North of Seguela around Bobi and Toubabouko a number of sheared dikes cut Precambrian granitic rocks and were described by Bardet (1974) as 'meta-kimberlites'. Although much altered the geochemistry and remnant mineralogy indicate that they are lamproitic.
This occurrence consists of granite and microgranite an analysis of which indicates it to be peralkaline (Arnould, 1961) but no petrographic description has been found.
This is a small intrusion of syenite an analysis of which indicates it to be peralkaline (Arnould, 1961). No petrographic details have been traced.
A number of syenite and quartz syenite intrusions of an alkaline character are described as of ‘Mont Troquoi type’ (Papon, 1973). Six such intrusions, all emplaced in Precambrian gneiss or migmatite, are indicated on the 1:500,000 geological map accompanying Papon’s (1973) paper.
The vast area lying north of 3°00’N between Lake Turkana and the northern and western borders of Kenya has been mapped by Walsh and Dodson (1969) and includes numerous volcanic centres, the oupourings from which extend over about one third of the total area.
The large area bounded on the west by Lake Turkana, the north by the Ethiopian border and the south by the 3°N line of latitude is described under the names of the Sabarei and Allia Bay areas in reports by Key and Watkins (1988) and Wilkinson (1988).