PEGMATITE

Ten (10) samples collected from six (06) different locations around Dagballa area in Akoko-Edo area, Southern Nigeria, were studied using field, geochemical and petrographical analysis to determine the relative abundance and distribution of major and minor elements present in the samples. The ten (10) samples comprise nine (09) pegmatite samples and one augen gneiss (01)sample which is the host rock are delineated as DA1-10 for easy recognition. Sampling interval for the rock samples varied depending on the aerial extent of each outcrop and fieldenvironmental conditions encountered. DA1 and DA2 were obtained from location 1, DA3 and DA4 from location 2, DA5 and DA6 from location 3, DA7 and DA8 from location 4, DA9 was obtained from location 5 and DA10 was obtained from location 6. The pegmatites in the Dagballa, area occurs as intrusions and is hosted by Augen-Gneiss. There is the presence of a sharp zonation and chilled margin in the first three locations encountered. The estimated contact between the pegmatite and the granite-gneiss is 30m. From thin section analysis, the pegmatites from Dagballa consist of quartz and feldspar minerals with microcline and albite being the dominant feldspar minerals present in most of the samples. Also, muscovite, biotite, opaque and other accessory minerals are present in minute quantities. Composite whole-rock samples were analyzed for major and minor oxides using X-Ray Fluorescence Spectrometer (XRF). The results reveal the pegmatites are very siliceous with SiO2 values of 66.75 wt.% to 74.75 wt.%. Al2O3 values are relatively moderate between14.57 wt.% to 15.61 wt.%. Na2O and K2O abundances are low and ranges between 2.76 wt.% to 5.56 wt.% and 3.50 wt.% to 8.43 wt.% respectively. MgO abundances are generally low (0.05-0.20 wt.%). Fe2O3 abundances are generally low between 0.30-0.47 wt.% with the exception been the abundance (5.82 wt.%) probably obtained from the host rock. Alumina saturation index (A/CNK) computation with values ranging from 1.160 to 1.738 indicates the rock samples are all peraluminous and therefore indicate S-type granite.