Gravity anomaly modelling of multiple geological sources having differing strike lengths and arbitrary density contrast variations

Abstract

ABSTRACTA method to compute gravity anomalies of multiple geological sources having variable but finite strike lengths with arbitrary density contrast variations is presented. An ensemble of variable but finite strike limited vertical prisms among which density contrasts vary randomly both with depth and lateral position describes the anomalous source(s). The proposed method has the advantage that it can be applied to compute the gravity anomalies of a variety of geologic sources at both local and crustal scale levels. The applicability of the method is demonstrated with synthetic and real field examples. In the synthetic example, the geology resembles that of a typical rifted sedimentary basin, where thick sectioned sediments with arbitrarily varying density contrasts are concealed under a thick pile of flood basalt. For the real field example, the method is applied to calculate the gravity anomalies of a crustal scale structure across the suture zone between the Superior and Churchill structural provinces in the Canadian Shield. Modelling of real field anomalies reveals that i) the Churchill block is much thicker and ii) the western boundary of the base of the fold belt within the Superior block is shallower than reported in previous studies.