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Vol. 10 (2007 year), No. 1
Nikitina L.P., Ovchinnikov N.O., Babushkina M.S., Yakovleva A.K., Yakovlev Yu.N., Chernova O.G., Goilo E.A.
Do Fe-Mg micas from the Archaean rocks of the Kola Superdeep Borehole preserve information about the crystalline substance state during their extraction to the surface in the course of drilling?
A comparative analysis of structural and spectroscopic peculiarities of the rock forming minerals in the SG-3 rocks and their homologues in the Pechenga structure framing allowed obtaining some new results concerning the specific character of buried Archaean units and constructing correlations between deep and surface formations. The investigations were performed with the use of the EPR data on vacancy defects (Р•1-centres) and defects related to the isomorphous incorporation of Al-, Ge-, Ti-ions into the lattice of the rock forming quartz and the X-ray luminescence (XRL) data on the proper and admixture defects in plagioclase. Rank correlations between the qualitative composition of the plagioclase XRL patterns and petrogenetic characteristics of host rocks have been found. Dependence of the system of admixture and proper structural defects in the rock forming minerals along the SG-3 section vs the depth of occurrence and petrogenesis of the Precambrian host rocks has been estimated. Our study showed that the admixture structural defects in the rock forming quartz can serve as a genetic mark of metamorphic rocks in the Precambrian structural-formational complexes. They are one of the criteria for typization and correlation of deeply metamorphosed Early Precambrian units penetrated by SG-3.
(in Russian, стр.13, fig. 8, tables. 6, ref 34, Adobe PDF, Adobe PDF 0 Kb)
Vol. 10 (2007 year), No. 1
Nikitina L.P., Babushkina M.S., Chernova O.G., Ovchinnikov N.O., Yakovleva A.K., Yakovlev Yu.N., Goilo E.A.
Structural state of amphibole from the Archaean rocks of the Kola Superdeep Borehole and their homologues at the surface
Trioctahedral ferromagnesium micas from the SG-3 Archaean rocks and their surface homologues constituting the amphibolite-gneiss complex in the Pechenga structure southern framing (Allarechka block) have been studied. The mineral structure, the nature and degree of structural defects have been investigated by X-ray powder diffractometry, infrared and Mossbauer spectroscopy. The chemical composition of micas was determined by the wet chemistry and microprobe methods. The study showed that with the same fm values, the mica structures from the SG-3 Archaean rocks have higher values of the unit cell volume over those for synthetic micas of the phlogopite-annite series. This is evidence of the mica structural "looseness" and is unexpected for a mineral from deep zones (7900-11350 m) taking into account the presence of trivalent cations to 0.5 AU in the mica octahedral layer. The presence of defects related to the composition non-stoichiometry (the presence of crystalline hydrate water molecules in the alkaline cation site and availability of vacancies in the octahedral sites M1) and defects of "order-disorder" type have been established. Non-stoichiometry of the composition is equally typical of the micas from the SG-3 Archaean rocks and surface homologues and is likely to reflect the metamorphism specific regime of the Archaean complex under amphibolite facies conditions (increased partial water pressure, lack of alkalies). At the same time the content of crystalline hydrate water molecules in the mica structure from the SG-3 Archaean rocks decreases slowly with depth. A various degree of cation order in the octahedral sites of the mica structure from the SG-3 Archaean rocks (disorder or close to disorder distribution) and from the homologous rocks (order distribution with prevailing ferrous iron occupation of the sites M1) has been established. The difference in the order degree most likely results from the different velocity of the Archaean rocks lift in the process of drilling as well as from the erosion processes. This fact supports the assumption that some structural peculiarities of minerals do not alter when extracting the core from the borehole. This provides preservation of the information on the crystalline substance state at depths of the Archaean complex cut by the borehole.
(in Russian, стр.11, fig. 3, tables. 8, ref 13, Adobe PDF, Adobe PDF 0 Kb)
Vol. 10 (2007 year), No. 1
Bayanova T.B., Yakovlev Yu.N., Guberman D.M., Yakovleva A.K., Skufin P.K.
Isotopic investigations of age of the Archaean rocks from the Kola Superdeep Borehole section, Proterozoic Pechenga structure and its framing.
The results of the study of ore mineralization in the rocks from the three lower volcanic formations in the SG-3 Proterozoic complex and in their near-surface homologues cut by the structural boreholes IX and X have been presented. Sulfide specialization of volcanites from the Majarvi Fm has been found. Oxide specialization of rocks from the Pirttijarvi and Orshoaivi Fms has been confirmed. The distribution, evolution conditions and chemical composition of sulfides and oxides from volcanites have been studied. The main features of development, composition and late alterations of ore minerals could be related to two factors. The composition of sulfide from the Majarvi Fm vulcanite and oxide from the Pirttijarvi and Orshoaivi Fms in the SG-3 section is determined by a "depth factor" that caused a widespread occurrence of mineral solid solutions. Intense development of hematite and transformation of magnetite and ilmenite in volcanites of the Pirttijarvi and Orshoaivi Fms in the SG-3 section are explained by the influence of the regional Luchlompolo fault. High contents of isomorphous admixtures – PGE, Se and Co in sulfides, V, Ti and Mn in oxides that were not observed earlier in the SG-3 section and geoblock as a whole have been established in all major minerals from the formations deep levels.
(in Russian, стр.12, fig. 9, tables. 3, ref 29, Adobe PDF, Adobe PDF 0 Kb)
Vol. 10 (2007 year), No. 1
Gordienko V.V., Gordienko Vl.Vl., Kalinicheva G.I., Olkhovaya E.A., Rumayntseva E.V., Timokhina L.A., Guberman D.M., Smirnov Yu.P., Yakovleva A.K., Yakovlev Yu.N.
Granitic pegmatite of the Kola Superdeep Borehole (vertical mineral-geochemical zoning and genesis problems)
The basement of the Early Proterozoic Pechenga palaeorift was penetrated by the Kola Superdeep Borehole (SG-3) at a depth of 6842-12262 m. In contrast to similar rocks framing the Pechenga palaeorift, Archaean rocks of SG-3 were affected by Proterozoic magmatism and metasomatism related to the rift development. The most intense Proterozoic processes were an intrusion of numerous mafic-ultramafic bodies, retrograde metamorphism and synmetamorphic migmatization, and emplacement of postkinematic granites. Most Proterozoic processes were determined to have been related to mantle sources. The overall amounts of Proterozoic material introduced into the Archaean rocks penetrated by the lowermost part of SG-3 coupled with the remobilized material of the Archaean crust is estimated at ?30 % (?12-15 % amphibolites, ~3 % granite veins, ~15 % migmatized rocks). Thus, searching for homologues to the SG-3 Archaean rocks does not lie only in a quest of analogous rocks in the frame of the Pechenga structure, but in the interpretation of the Proterozoic processes that have changed quantitative ratios and composition of the palaeorift basement rocks.
(in Russian, стр.14, fig. 3, tables. 7, ref 11, Adobe PDF, Adobe PDF 0 Kb)