Molybdenum deposits in local anomalies of gravity and magnetic fields

Three-dimensional structures of four ore districts are considered in this paper on the basis of gravimetric and magnetic maps on a 1:200 000 scale. The Zhireken and Orekitkan molybdenum deposits and the Agaskyr and Sorsk copper-molybdenum deposits are associated with these districts. In 25 deposits, the maximum areas of molybdenum-bearing granite plutons, determined as ore districts in local gravity minimums, statistically exceeds by 18 times the minimum areas. However, the average areas of plutons, with which large, medium, and small deposits are correspondingly associated, are practically identical. At the same time, the mean values of the vertical thickness of plutons with large deposits are almost two times greater than those for plutons accompanied by small deposits. Specific magnetic anomalies are distinguished within the ore districts. They are absolute or relative local minima, baylike depressions of field (Ta), and local maxima with areas of up to 60 km(2). By their dimensions, they are commensurate or exceed the area of ore fields. Not less than half of the molybdenum deposits expected in a definite metallogenic area or zone are associated with similar anomalies. The detection probability of large deposits in magnetic prospective areas is close to 40%.