Magnetic studies in Cyprus and the Biga Peninsula, Turkey.

The low-level (150 metres mean terrain clearance) aeromagnetic maps of Cyprus and the Biga peninsula, Turkey have been analysed to determine the structure and the location of the mineralized areas. The aeromagnetic data was digitized at 0.5 and 1.0 km intervals reduced to pole, filtered, continued upwards and downwards, and the second vertical derivative determined, all using programs written for the purpose. The resulting maps were broadly similar but the most useful was that resulting from the application of the Fuller 2-D filter (Fuller, 1967) whose pass-band characteristics could be adjusted as required. The magnetic properties of the main rock types were determined on cores in the laboratory using a PAR spinner magnetometer and a Sharpe SM4 susceptibility bridge. These were used in the interpretation of the filtered maps by using the methods of Talwani et al. (1964) and Koulomzine et al. (1970). In Cyprus, the positive anomalies were attributed to the Pillow Lavas which had a mean total magnetization of 9.0 x 10-3 e.m.u./cm3 in the direction 280°/42° down. The negative anomalies were attributed to the intrusive gabbros which had a mean total magnetization of 1.4 x 10-3 e.m.u./cm3 in the direction 300°/66° down. The "Sheeted Intrusive Complex" has a moderate total magnetization of 4.1 x 10-3 e.m.u./cm 3 in the direction 329°/56° down. The anomalies were therefore interpreted in terms of the Pillow Lavas of thicknesses varying up to 500 metres and variation in the depth to the gabbros. The trends of the magnetic anomalies reflect two main trends - NW and ENE of the mineralization which is believed to have originated from the gabbros The orebodies are usually located at the faulted zones in the Lower Pillow Lavas on the down-throwside and the aeromagnetic data could be used to assist in the location of these faults. Gossanized zones cap gabbroic intrusions which may have massive sulphides on the flanks where they intrude the Pillow Lavas and are indicated by negative anomalies. In the Biga peninsula, the magnetic anomalies are attributed to the granodiorites which have a mean total magnetization of 4.09 x 10-3 e.m.u./cm 3 in the direction 344°/60° down. The granodiorites intrude a metamorphic basement series which is faulted into a series of NE-SW striking horsts and grabens and this is reflected in the trending of the magnetic anomalies. The magnetic interpretation shows that there is a deep basinal area extending to the Sea of Marmara northeastwards from the Bay of Edremit with maximum depth of 5 km. The principal orebodies are hydrothermal originating from the granodiorites and are found in the basement. The aeromagnetic data may therefore be used to locate underground granodiorite cupolas around which mineralization may exist