|
V.I.Dragunov and V.A.Cherepanov in 1971 were the first to propose the idea that the true rock element (component) or subsystem of the "natural rock" object-system will be some minimal mineral grain aggregate or its "unit cell" the propagation of which could give us a whole rock. As it was shown by us (Povarennykh, 1989), the primary element of the object-system - "rock as essentially natural mineral paragenesis" - one should consider not a mineral grain (even for the monomineral rock !) but some minimal by dimensions aggregate of mineral grains (or frustum - lump in Latin), and the phenomenon is proposed to be called frustumation. We treat as our predecessors such investigators as S.M. Beskin, I.S.Delitsyn, M.A.Sadovsky, R.L.Brodskaya,Y.B.Marin, A.N.Nikitin and O.A.Sustavov.
In the report one can observe the first steps of the revealing and visualization of frustums while macrophysiographical petrographical analysis of several rocks. Frustumation has been firstly revealed in several samples of the primarily chemogenic metamorphosed small-medium grained Karrara (Italy) statuary calcite-dolomite marble under the influence of short-wave ultra-violet emanation of mercury-quartz high-pressure lamp as a source of luminescence stimulation, and then in numerous samples of several rocks of different genesis ( Povarennykh, Beskin, 2006 and other). Characteristic dimensions and outlines of the frustums within the rocks investigated vary greatly for mono- and polymineral rocks. The smallest frustums by the amount of mineral grains they contained have been observed in monomineral rocks: datolitic scarn, silicate quartz pegmatite nucleus, galite and marble (about 125-300 grains in volume). The greatest frustums have been observed in polymineral rocks: medium-grained amazonite-albitic and pegmatoid rare-metal granites (more than 3000 grains). Frusumation within the Zashikhinskoye small-grained metasomatically changed granites was observed in the form of the 3-5 sm in diameter subisometrical (in plane) mineral grain aggregates that may be interpreted in volume as untwisting helices about 10 sm in height - analogues of the Benard cells oriented by the dissipation gradient. As it is shown, the later subsequent processes (amazonitization, albitization, and quartzitization in granites as well as ore mineralization development) inherited the frustums boundaries as weakened zones within these rocks and to some extent underlined it by their more abundant occurrence. Features of this firstly discovered macroscopic stereological rock phenomenon and its effect on rock crushing and ore dressing are discussed.
Fig. 1. Frustumation (supertexture) pattern of monomineral rocks inner composition vizualised with the help of laser-ultrasonic echoscopy methode. A - medium-fine grained Kibik-Kordonsky marble, B - medium-fine grained Kyshtymsky granulated quartzite. Specimen width: 13 and 12 mm, relatively. Upper part of picture - original pattern, lower - retouched.
|
