Olusegun Dada

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  Article: GEOCHEMISTRY OF BIOTITE AND ITS IMPLICATIONS TO THE ORIGIN OF BAUCHI AND SAMINAKA CHARNOCKITES, NORTH CENTRAL NIGERIA.

  Olusegun, Adekoyejo Dada
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  ABSTRACT: Biotites from the charnockites of Bauchi and Saminaka in the Basement Complex of north central Nigeria have been examined. The microprobe data of the analyzed biotites are presented. The behavior of major elements in the examined biotites is discussed according to different discrimination models. Based on the geochemical and petrographical characteristics of the biotites analyzed, the biotite of Bauchi charnockite is transitional in nature and may have been associated with magmas having physicochemical properties between calc-alkaline and peraluminous series while those of Saminaka charnockite is peraluminous in nature. This may have resulted from either magma differentiation by mixing or large-scale crustal contamination.
  International Journal of Geology, Earth and Environmental Sciences. 08/2012; ISSN(2 (2) pp.162-172):2277-2081.
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  Article: ON THE CHEMISTRY AND GEOTHERMOBAROMETRY OF AMPHIBOLES OF CHARNOCKITES FROM BAUCHI AND SAMINAKA, NORTHCENTRAL NIGERIA: GENETIC IMPLICATIONS

  Olusegun Adekoyejo Dada, Edafetano Christopher Ashano, Shekwonyadu Iyakwari
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  ABSTRACT: Amphibole compositions of the charnockites from Bauchi and Saminaka, North-central Nigeria have been studied by electron probe micro analysis. Generally, the amphiboles are all calcic, silica and magnesia poor, ferroan rich weakly titaniferous and have most of their aluminum in tetrahedral site. Si contents average 6.35 apfu (Bauchi) and 6.42 apfu (Saminaka). Ca is always above 1.7 apfu for both areas. NaA is always > Na M4 . K 2 O contents are high. All samples exhibit low Al VI and high Al IV contents equate to more than 90% of Al to the tetrahedrical site. TiO 2 contents average 1.60% (Bauchi) and 1.65% (Saminaka). FeO T contents are high. Most of the amphiboles are characterized by low Fe 3+ and high Fe 2+ contents. Xmg ratio varies between 0.18 and 0.64 (Bauchi) and 0.26 to 0.37 (Saminaka). They may be divided into two sub-groups: On the one hand the magnesio-hastingsite -hastingsite and pargasite group and on the other hand the tschermakite group. The amphiboles from Bauchi and Saminaka charnockites plot in the igneous field of the diagram. From thermobarometric investigations, Amphiboles in the charnockites solidified between 4.4 to 7.2 kbar (Bauchi) and 5.3 to 5.6 kbar as estimated by its Al contents, while temperature of crystallization range from 826º to 599º C (Bauchi) and 826º to 650º C (Saminaka). Nevertheless, Bauchi charnockite's amphibole-core temperatures decrease continuously from 826º C for hastingsite to magnesio-hornblende 599º C. These conditions correspond to a shallow crustal chamber (15-20 km depth).
  International Journal of Basic and Applied Chemical Sciences. 09/2012; ISSN(2-3):2277-2073.
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  Article: Application of Biotite Composition in Determination of Petrogenesis of Diorites from Toro and Dass, North Central, Nigeria

  O Dada, E Ashano
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  ABSTRACT: The compositional systematics of biotites from diorites of Toro and Dass, north Central Nigeria have been examined for the purpose of describing the nature of the granitic magma. Based on chemistry of biotites, Toro and Dass diorites are formed from the transition between peraluminous and calc-alkaline magmas. This type of magma is typically produced in subduction environments. It means that the diorites could have formed in an orogenic suit from calc-alkaline magma derived from melting in a subduction zone slab. There is little evidence of either magma mixing or large-scale crustal contamination. The petrographic studies of the representative samples of diorite from Toro show biotite replacing pyroxenes, which necessarily produce a biotite-pyroxene-plagioclase paragenesis from pre-existing assemblage. The Dass diorite samples show biotite overgrowing amphiboles and also replacement of biotite by chlorite.
  International Journal of Science and Technology. 04/2012; 1(4-4):164-169.