Geneza aureoli radowych wokół stref triasowej mineralizacji uranowej w syneklizie perybałtyckiej

Abstract

W drugiej połowie lat 70·tych w Instytucie Geologicznym podjęto poszukiwania złóż rud uranu w syneklizie perybałtyckiej. Na podstawie analizy wyników badań geofizycznych i laboratoryjnych stwierdzono m.in. obecność aureoli radowych (Ra-226) wokół dotychczas wykrytych uranowych ciał rudnych. Wyjaśniono mechanizm powstawania tych aureoli, a także przedstawiono propozycję metodyczną wy· korzystania ich w prospekcji złóż uranu na badanym obszarze.ON ORIGIN OF RADIUM AUREOLES AROUND TRIASSIC URANIUM MINERALlZATION ZONES IN THE PERIBALTIC SYNECLIZE The interest in search for deep-seated, obscure uranium deposits should increase along with depletion of shallow-seated ones. The search and identification of such deposits appears difficult because of the lack of any surface signatures, especially those related to migration of U·238 and products of its decay, which could indicate their presence (l.J. Daniels and others. 1977). Drillings were hitherto used as the only method of search for the deep-seated deposits but they appear very ardous and expensive way to solve this question, mainly because of generally small linear dimensions ore bodies. In the second half of the seventies, the Geological Institute began search for sandstone uranium deposits in the Triassic of the Peribaltic Syneclize. Detailed analysis of both laboratory and geophysical data showed presence of radium (Ra-226) aureoles around uranium ore bodies hitherto found by drillings. The mechanism of origin of the aureoles is explained in this paper and methodological proposal of their use in further search for uranium deposits is given. Theoretical modeling showed that origin of the aureoles is mainly related to movement of deposit waters percolating through uranium ore body. The influence of shape and dimensions of radium aureole-generating ore bodies on extent of the au-reoles appears subordinate. Aureoles interesting from the point of view of prospecting may originate when velocity of percolating waters falls within the range from 10-8 to 10-6 cm/s.