The concentration of diamond-bearing tagamite from the Popigai impact crater produces large amounts of graphite in addition to impact diamonds (1:100, respectively). The question arises of whether this is residual graphite not converted to diamond at the time of the Popigai impact or is a retrograde form resulting from back-conversion of impact diamond to graphite in a high-temperature tagamite melt. Experiments show that graphite from tagamite is a residual phase. Coexistence of lonsdaleite, cubic diamond, and single-crystal graphite within a limited volume may be due to different orientations of the graphite base plane relative to the impact stress direction. Thus, the diamond-bearing rocks may contain significant amounts of residual graphite, which is consistent with published evidence.

An..l.iTH.ACr Garne ts from couc eru ratc fro m the varg cm l kimberl ite pipe sho w a long co mpos itional range and reveallong lincar tre nd s withi n the lherzolite field in a Cr~Ol -Ca O% dia gram (Sobolcv et til. 1974) (lip (0 11% MgO). fon ned by grains o f d ifferent d ime nsions w ith fcw deviations to harzburg itcs . La rger g rains (fractio n +3 ) arc higher in CaO with less Cr~01 (to 5.5%). TIle C r 2 0 1 freq uen cy reduc es in hy perbo lic function for each fraction . IIme nites re ve;114 2· 56% Ti0 2 l..'Olllpositio nai range with linear FeO -MgO correhuions but 3(4) separate g roups for A I~01 sugge st different proport ion o f co -prccipimted gimlet , probably d ue to polybn ric Irncnonanon. lncreasing Cr~O l nnd r"t..-Q% co nte nt (fractionatio n ue gn:e ) with red ucing TiO~is in accord with Ar c mod el.• .Ganict xeno lith fnnnldnin II pipe with large Ga r-Cpx grains and fine Mica-Curb bearing matrix refer to 60 kbcr and 35 mv/ m2 gcothcrm . 11displays enr iched trace c lement patter ns but no t co mpletel y equilibrate d co mpositions for Ga r anti C px. sugg es ting lo w deg ree me lting o f rela tively fertile ma ntle. St ud ied uuuc rinlmay s ugg csrmcrasomu tized, relat ively fertile and irre gularly heated mantle bene ath So mbcrn Bra zil as fo und by (Carva-lho & Lccnnrdos 1997 ).

No abstract

The process of producing finely dispersed Ba 1-x Sr x TiO 3, BaTiO 3 and (Bi 1-ɯ La ɯ ) 4 Ti 3 O 12 powders with ultra-and nanosized particles by chemical reactions in multi-component salt melts is developed. Also the opportunities of sol-gel method for the film structures formation are used by means of ferroelectric powders inclusion in an oxide silicate matrix. The optimal syntheses condition of film glass-ceramical structures formation are determined.

In 1972, a great deal of Cr-spinels were found near the town of Mirny, Western Yakutia. Compositionally, they were similar to kimberlitic varietes but drastically differed from them in morphology. Up to 30% of these spinellide corresponded in composition to chromite inclusions in diamonds. This suggested the existence of unknown bodies with an unusual morphological variety of Cr-spinels, and some geologists believe that these bodies are diamondiferous kimberlites. Later on, similar Cr-spinels were found in placers throughout the Yakutian diamondiferous province, in the Arkhangelsk Region, in many places beyond Russia, and on other continents. Nevertheless, none of the kimberlite sources of these Cr-spinels has been found yet. In all the known kimberlites and lamproites Cr-spinels are of different morphology. The challenge was to establish the type of sources of the new variety of Cr-spinels. The crystalline inclusions present in these Cr-spinels are olivine, Opx, Cpx, mica, amphibole, and plagioclase. Investigations in this direction permitted us to demonstrate that in morphology they are completely analogous to and in composition overlaps the Cr-spinels from ultrabasic intrusions of the type of Kempirsai, Chad, Konder, and many other plutons (see Table). This suggests that the new variety of Cr-spinels originated from intrusions of ultrabasic rocks. These intrusions are not diamondiferous, but close compositions of their Cr-spinels with those from kimberlites and lamproites (with morphology ignored) are misleading in exploration for diamonds. Geologists used these Cr-spinels as indicators of kimberlites or lamproites and, to follow them, pursue diamonds with no result. Therefore, in exploration for kimberlites and lamproites the ultrabasic Cr-spinels may play the role of false indicators. Each ultrabasic intrusion contains Cr-spinels of specific composition, but these compositions overlap with kimberlitic (lamproitic) varieties. Therefore, the main difference between two types of Crspinels mantle-derived type from kimberlites (lamproites) and crust-derived type from ultrabasic intrusions lies in morphology. Differences in morphology are, probably, due to differences in processes of crystallization: under conditions of the upper mantle for the first type and under conditions of the crust, for the second. The Cr-spinels from intrusions of ultrabasic rocks are significantly more widespread in sedimentary collectors than the Cr-spinels from kimberlites and lamproites. Therefore, the problem of false indicators has come into importance in searching for diamonds. On the basis of chemical composition only, one cannot always discriminate between the "mantle" and the "crustal" Cr-spinels, but the additional study of morphology permits them to be discriminated in a reliable way.