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Prediction of gravity anomaly from calculated densities of rocks

Omosanya K. O., Mosuro G. O, Laniyan T. A and Ogunleye D.

Density and density contrasts of rocks controls gravity anomalies and is an important physical property of geologic material which aids in the identification of rocks, estimation of ore abundances, and assessing rock conditions. The study was carried out with the aim of modeling gravity anomaly from calculated densities. Dry density of twenty five (25) rock samples collected randomly during the geological mapping exercise were analyzed in the laboratory using traditional dry and wet method. The particle density was estimated using the relationship (m2 - m1) / (m4-m1) - (m3-m2). Rocks identified in the area include Granite (av. ρ ~2.72 gm-3), Biotite granite (av. ρ ~2.7213gm-3), and Pegmatite (av. ρ ~ 2.7125 gm-3). Anomaly types described along selected gravity profiles include S, M, Concave up, UL, Zig-Zag Flat top and Stair case anomalies. The 3D modeled gravity anomaly map of the upper part of the study area shows that peaks in the map correspond to the location of the pegmatite outcrop. Along the profiles the pegmatite outcrop are shown as concave up anomalies. Gravity anomalies in the study area are associated with mineralization and ambiguity in the anomalies calculated result from variation in the porosity of the different rock samples.