Radiometric geological exploration method used in the central part of the State of Sonora

The purpose of this study is to make known the importance of the radiometric data, the physical principles on which they are based and the geological interpretation which will permit in an indirect way to select important radioactive areas in order to carry out verification studies on the ground to see if there are sufficient reasons to show any interest in these areas. Till now this work has been realized in the State of Sonora (Mexico) in an area of 51,000 Km2 subdivided in 14 zones, numbered from 201 to 214, and for the present work the zone 208 has been selected. This Zone is located at the north-west of the City of Hermosillo, and has a total area of 3400 Km2 which has been the object of the study by plane through systematic flights in an east-west direction, in order to obtain the configuration and interpret it from a radiometrical point of view. The obtained isorads configuration plans of 4 channels of detection are the following: total counting, potassium, bismuth and thallium as well as their relations. From the 14 verified anomalies the anomaly Noche Buena was selected in order to carry out reconnaissance surveys and preliminary and detailed geological studies. The geology of the area is represented by extrusive and intrusive igneous rocks as well as sedimentary. The uraniferous mineralization is secondary and is represented by autunite, meta-autunite and torbenite which represent an average of 200 g to 3.08 Kg. of U3O8 per ton. (author)