Abstract
Background/Objectives: Talcose rocks within Precambrian Basement Complex serve as relics of Archean greenstones. alterations associated with polycyclic-orogenies that affected this complex is studied to understand mineralogical and geochemical alterations. Methods: Five fresh samples of talcose rocks were collected during field mapping. These samples were cut into thin sections to reveal modal mineralogy, altered minerals and degree of alteration of such minerals. Mineral phase identification of the talcose rocks was conducted using X-ray Broker D8 ADVANCE diffractometer while whole rock analysis was carried out using Inductively Coupled Plasma Mass Spectrometry. Findings: Lithological relationship revealed from field evidence showed that the talc bodies occurred in close association with micaceous schist. The mineral assemblage of talc, tremolite, actinolite, chlorite and calcite suggest low grade greenschist metamorphic facies from possible hydrothermal alteration. Geochemical results revealed the following range of concentrations; SiO2 42.19-59.03%; Al2O3 1.1 - 11.8%; Fe2O3 7.64-9.56%; MgO 24.47-26.639%; Ni 594-1207ppm; Co 43.2-113.9ppm; Sn 6-41ppm; V 32-75ppm and Zr 1.3-58.7ppm, and these are typical of talcose rocks. Petrogenetic studies suggest a komatiitic origin with a peridotitic komatiite precursor for the talc-chlorite-tremolite schist. Enrichment in LREE, depletion in HREE and a negative Eu anomaly suggest alteration of the parent magma for the talcose rock and plagioclase fractionation. The trends observed for the LILE, HFSE and REE suggest possible contamination or mixing of crustal and mantle materials during the formation of the protolith. Ni and Co concentrations are higher than average crustal values with implication for ultrabasic to basic magma composition for the komatiitic progenitor and also suggestive of possible mineralisation. Conclusion: Mineralogical examination has revealed a talc-chlorite-tremolite composition for the talcose rocks with peridotitic komatiite precursory while geochemical composition supported ultrabasic magmatism similar to those with the Ilesha schist belt.
Highlights
Talc bearing rocks have been reported within the schist belts; which are mostly restricted to the western part of Nigeria smaller occurrences of schist belts have been reported in the eastern portion of the country. [1]Talcose rocks are metamorphic rocks formed from the alteration of mafic and ultramafic rocks [2] as well as from the metamorphism of siliceous dolomitic carbonate rocks
Talcose rocks have been reported to be in close association with mafic, ultramafic and metasedimentary rock especially within the Ilesha schist that has been widely studied. [3,4]A knowledge of their geology can aid in a better understanding of the associated rocks and the geologic evolution of the areas in which they outcrop
Talc occurrences have been reported within most parts of the Ilesha schist belt, [3,4]and studies have been conducted on their petrology, petrogenesis, mineralogy as well as their industrial applicability and economic potential by several authors from areas like Baba Ode, [5] Erin Omu, [6]Wonu-Apomu, [7,8] Kumaru, [9]Oke-Ila[10], Ile-Ife, Ikirun and Esa Oke,(11) Itagunmodi-Igun [12] and parts of the Ilesha schist belt.[13] there is a dearth of research data on talcose bodies within the Ila Orangun-Oyan area of the Ilesha schist belt
Summary
Talc bearing rocks have been reported within the schist belts; which are mostly restricted to the western part of Nigeria smaller occurrences of schist belts have been reported in the eastern portion of the country. [1]Talcose rocks are metamorphic rocks formed from the alteration of mafic and ultramafic rocks [2] as well as from the metamorphism of siliceous dolomitic carbonate rocks. Talcose rocks have been reported to be in close association with mafic, ultramafic and metasedimentary rock especially within the Ilesha schist that has been widely studied. Talc occurrences have been reported within most parts of the Ilesha schist belt, [3,4]and studies have been conducted on their petrology, petrogenesis, mineralogy as well as their industrial applicability and economic potential by several authors from areas like Baba Ode, [5] Erin Omu, [6]Wonu-Apomu, [7,8] Kumaru, [9]Oke-Ila[10], Ile-Ife, Ikirun and Esa Oke,(11) Itagunmodi-Igun [12] and parts of the Ilesha schist belt.[13] there is a dearth of research data on talcose bodies within the Ila Orangun-Oyan area of the Ilesha schist belt. This study intends to determine the origin, mineralogy and geochemistry of Talcose bodies within Ila Orangun-Oyan area and the extent to which the shearing and hydrothermal processes affected the talc bodies in the area. It aims to establish if the talc bodies in the Ila Orangun-Oyan area are a continuation of the deposits in other parts of the schist belt located south of the area studied
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