New Technique of Geophysical Data Analysis During Forecast-Prospecting Investigations in Nakyn Kimberlite Field (Western Yakutia)

Abstract

Technique, basing on processing of the materials of geophysical investigations of boreholes (GIB) in the areal view, allowing revealing local geophysical indications of primary diamond deposits’ allocation, has been developed and tested on the example of the Nakyn kimberlite field. Data of 4 methods of GIB have served as the material for investigations: logging of magnetic susceptibility, gamma-ray logging, borehole geomagnetics and induction logging.

Most informative are the data of gamma-ray logging on buried rocks of Lower Paleozoic, reflecting important features of geologic-structural constitution of the Nakyn field and its flanks. It was established that the ore-forming system, including kimberlite-controlling and kimberlite-bearing faults, as well as neighboring to the pipes space of all kimberlite bodies of the field, differs, along with the kimberlites, by decreased values of natural radioactivity. Diagonal kimberlite-bearing fault has been distinguished with sufficient confidence, though it is specified by other geologic-geophysical methods unreliably, or practically does not succumb to mapping. Besides known ore-bearing structures, linear zones and anomalies of various morphology and size can be traced within the field, characterized by decreased natural radioactivity, part of which requires a more detailed research.

When employing this technique on other kimberlite fields one should consider that radioactivity and other physical properties of both kimberlites and surrounding them rocks may vary significantly. Involvement of the proposed technique into the complex of prospecting works will allow increasing efficiency of geologicalexploration works on diamonds in “closed” regions of Western Yakutia.