Premineral hydrothermal alteration of host rocks at the Schlema uranium deposit, Erzgebirge, Germany: II. A computer modelingстатья
Информация о цитировании статьи получена из
Web of Science,
Scopus
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:The study of actual premineral alteration of "productive" rocks [1], which host the pitchblende-bearing veins at the Schlema deposit, Erzgebirge, Germany, served as a groundwork for the elaboration of computer models reproducing the interaction between hydrothermal solutions and host rocks at the uranium-ore stage. The first set of models was aimed at the computation and analysis of interaction (mainly at 200 degrees C and 2 kbar) of the water phase with granites of the Aue dome and Ordovician light phyllites of its outer contact zone. The equilibration of the water phase with rocks in the near-contact zone predetermined the composition and properties (pH, Eh, I) of solutions, as well as their saturation with uranium. Such solutions ascended along thousands of steep fractures into the so-called "productive sequence" where the major mass of veined uranium ore was deposited in open fissures. The second set of models dealt with interaction of ascending solutions with acid and basic rocks of the "productive sequence." A series of models describes the mass exchange between ascending solutions and rocks of the "productive sequence" under isothermic conditions; another series of models takes into account the cooling of the solution and pressure drop from P-T conditions of the near-granite region to 150 degrees C and 1000 bar within the "productive sequence". Finally, the third series of models (so-called "layered" models) mimics the intercalation of acid and basic rocks within the "productive sequence." The above models reproduce the main specific feature of premineral alteration of "productive rocks," i.e., the vigorous mass exchange between solutions and basic rocks and almost absolute inertness of solutions with respect to major components at contact with acid rocks. The near-vein alteration haloes in basic rocks best fitting the natural prototypes and containing the typical assemblage of secondary minerals (adular, albite, mica, chlorite, quartz, hematite, etc.) were obtained in models which took into account the T and P drop of the ascending hydrothermal solutions and their intensive interaction with wall rocks.