Petrography and Geochemistry of Granitoids associated with Gold Mineralisation at Mpohor area in southeastern Ashanti Belt of Birimian, Ghana


  • George Mensah Tetteh University of Mines and Technology (UMaT), Tarkwa


Petrography, Geochemistry, Gold mineralisation, Granitoids, Southeastern Ashanti belt, Birimian, Ghana


Mpohor area in Western Region of Ghana is located within the Birimian at the southeastern corridor of Ashantibelt. Diamond drilling in the area which encloses Father Brown concession intersected steeply dipping igneous rocks on which petrographic and whole rock XRF analyses were conducted to describe the rock types according to mineralogy, texture, alteration and mode of mineralisation. The study showed that gabbro and diorite are weakly deformed, partially altered and of greenschist facies. These rocks intruded into belt granitoids which accompanied metavolcanic rocks (well exposed at a coastal region at the southeast). Subsequent tonalite and granodiorite intrusives, into sheared areas of gabbro are deformed with foliation being parallel to the major foliation in the host rock. This ductile deformation was accompanied by brittle deformation and infiltrated by hydrothermal fluids leading to silicification, carbonatisation, sericitisation, pyritisation of second and third generations and gold mineralisation. On the contrary, chloritisation with fine chalcopyrite together with pyrite of first generation characterise host gabbro and diorite. Hence deformed pyrite porphyroblast of second generation is found in tonalite and partly in contact with magnetite and also associated with gold. The ore zone (Au grade between 1.78 to 48.80 g/t) in tonalite is characterised by lower TiO2 content (<0.73 wt %) in addition to Fe/Mg ratio above 2.4 and Zr values less than 100 ppm which may suggest that mineralised fluid was depleted of Ti and Zr and accompanied the more mafic host rocks.

Author Biography

George Mensah Tetteh, University of Mines and Technology (UMaT), Tarkwa

Geology Lecturer


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Geological Eng. Article