Download manganese mineralisation in metamorphic terrains, case study

MANGANESE MINERALISATION IN METAMORPHIC TERRAINS,
CASE STUDY NGUUNI AREA, MAKUENI COUNTY
Manganese occurs in various ores in metamorphic terrains. The major ores in which they occur
include Pyrolusite, Psilomelane, Manganite, Hausmannite, Braunite, Rhodochrosite and
Rhodonite. The case study area of this project research, Nguuni area; is located in Makueni
county, Kilungu sub-county. It is lies at a distance of approximately 170km on average from
Nairobi. The main ore from which the manganese minerals in Nguuni area occur is of the
Psilomelane type. These ores are often found in bedded deposits and clays. Since metamorphic
terrains are often areas which were initially of sedimentary or volcanic origin before being acted
upon by P/T conditions, the ores may therefore have been of either of the above mentioned
origins before metamorphism. The ores found in Nguuni area occurred in sedimentary rocks of
the orthoquartzite-glauconite clay association before the metamorphism processes. These
manganese in the case study area are not very extensive in distribution. They measure
approximately 5m by 2m on average. The composition of the soils in the surrounding area based
on the geochemical analysis reveals that the Psilomelane ore weathers to give rise to very high
percentages of manganese in the surrounding soils. The high levels of manganese tends to
greatly affect the plants around. Some of the major symptoms of the toxicity caused by high
manganese levels in the soils include marginal chloroses, necrotic lesions and the distorted
development of leaves.