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Rock Types

Posted by on 2/20/2004 2:08:29 PM |

The three major rock types - igneous, meta- morphic and sedimentary - abound in Nigeria. Igneous and metamorphic rocks constitute the Pre- cambrian basement complex which is the oldest, crystalline, solid physical foundation of the country. Sedimentary rocks fill up the basins which are vast depressions between basement landmass. The Basement Complex and the sedimentary basins are equally dispersed in Nigeria, with base- ment most extensive in Northern Nigeria; less so in the south-western part of the country; and least along the eastern margin.

The sedimentary basins occupy the central x-shaped area in the country; they underlie all of southern Nigeria; and are also found in the northwest in Sokoto, and in Borno State and the entire Lake Chad in the north- east. Igneous and volcanic rocks occur mainly on the Jos Plateau, where they are the sources of mineral deposits such as tin, columbite, tantalite, wolframite, monazite and gemstones. Gold, molyb- denite, and non-metallic minerals such as marble, feldspars and talc are among the mineral deposits in the Basement Complex.

Apart from oil and natural gas, groundwater and a host of industrial minerals such as barites, lime- stone and clay, the older sedimentary rocks are mineralised with lead and zinc. Coal and lignite occur extensively in the southern and middle Benue Trough, with the lignite belt extending into Delta State. Bitumen or tar occurs in Cretaceous sedi- ments extending from Ogun to Ondo State. Lateritic superficial deposits are ubiquitous in Nigeria.


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