oa An Interpration of Gravity and Magnetic Data for Hydrocarbon Exploration in the Sirt Basin (Central North of Libya)

Gravity and magnetic data for hydrocarbon exploration in the Sirt basin in north central Libya were studied. The study involves analysis of the data to delineate major structures and faults in the study area. The produced Bouguer gravity map shows prominent NW-SE and NE-SW structural/trends. Isostatic residual map for gravity data is characterized by a dominant NW-SE trend in the study area. This is clearly evident in the Isostatic residual map. The main trending anomalies are in the northern and southeastern parts of study area with NW-SE orientation. A strong NW-SE trend is truncated by E-W trending structures in the southeastern and southwestern parts of the area. This is consistent with the change of tectonic zones. The magnetic expression in the northern part of Agedabia trough is characterized by NW-SE trending structures which coincide with late Cretaceous structures of the Sirt basin, while the southern part is characterised by NE-SW trending features which coincide with a late Palaeozoic trend. The northern part of the Agedabia trough is separated from the southern part by a prominent NE-SW lineament that is expressed in both the gravity and magnetic data. It is interpreted as a basement fault, which separates a thicker southern crust from a thinner<br>northern crust. The high gravity anomaly within the northern part of the Agedabia trough is interpreted as a result of mantle upwelling which caused thinning of the continental crust beneath the northern part of the Agedabia trough. Total horizontal derivative of the gravity and magnetic data generally reflect faults or compositional changes which can be seen to describe structural trends. The central part of the basin can be divided into four zones where the eastern and northern zone shows many short anomalies of NW-SE orientation and the southern zone shows N-S orientation, in the northern zone of the central part shows NWSE orientation trends. In the eastern zone strong NW-SE trends cut with NE-SW changing to E-W trends. The NW-SE structural trends of the Sirt basin are related to the late Cretaceous extensional phase and seem to truncate the other tectonic trends. These structures developed the traps and migration of hydrocarbons during Early Oligocene and Paleocene.