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Vol. 10 (2007 year), No. 1
Skufin P.K., Lyutoev V.P., Yakovlev Yu.N., Smirnov Yu.P., Glukhov Yu.V., Kotova E.N.
Properties and structural peculiarities of rock forming minerals and Early Proterozoic sedimentary rocks in the SG-3 section and their homologues at the surface
Actinolites and hornblendes from the SG-3 Archaean rocks and from the surface Archaean complex (Allarechka block) have been studied. The Allarechka block used to be considered a surface analogue of the SG-3 Archaean complex. 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 was determined by the wet chemistry and microprobe methods. The comprehensive investigations resulted in establishing composition stoichiometry of deep and surface amphiboles. Vacancies are present only in rare samples and in minor amounts. The majority of the studied amphiboles had a high degree of the unit cell deformation and its elongation along the c axis. A high and about the same degree of Fe2+ and other cations was observed in both groups of specimens. At the same time the patterns of the site occupation by Fe2+ are slightly different: Fe(M3)>Fe(M2)?Fe(M1) – for deep samples and Fe(M3)>Fe(M1)>Fe(M2) – for surface ones. The degree of iron oxidation is established to be similar (from 5 to for 20 %) for both surface and deep samples. Actinolite and low-alumina hornblende have no marked difference in their structural state at a depth of 7900-11350 m and at the surface. The data on the crystalline substance state at the crust deep zones may be useful for reliable interpretation of geophysical measurements, development of correct models of the crust structure and for choosing the proper sites for disposal of radioactive wastes. The structural state of amphibole (actinolite, low-alumina hornblende) from amphibolite and crystalline schist of the SG-3 Archaean complex and their surface homologues has been studied. The aim was to elucidate whether the structural state of those amphiboles differs and whether the amphiboles from the SG-3 Archaean rocks preserve any information about the physical state of the crystalline substance at great depths during their extraction to the surface. We have studied the composition, degree of iron oxidation, nature and degree of structural defects and the availability of various forms of water in the structure of amphiboles from the SG-3 Archaean rocks (7930-11330 m) and their surface homologues from the Allarechka block (southern framing of the Pechenga structure). According to the modern nomenclature (Leake, 1997), the actinolite and hornblende pertain to the calcic amphibole group.
(in Russian, стр.19, fig. 11, tables. 8, ref 25, Adobe PDF, Adobe PDF 0 Kb)
Vol. 10 (2007 year), No. 1
Yakovlev Yu.N., Skufin P.K.
Ore mineralization of Proterozoic rocks from the lower volcanic formations in the SG-3 section and their homologues in the near-surface zone
Inclusions in zircon of magmatic and metamorphic genesis from biotite-plagioclase gneiss in SG-3 Archaean unit VIII have been studied. A criterion of magmatic zircon genesis is the presence of melted inclusions in them, the study of which allows determining the composition and evolution of the primary melts. The study of the inclusion composition showed that crystallization of plagiorhyodacitic melts started with formation of micro grains of potassium-bearing plagioclase (Ab61, An26, and Or13) and titanomagnetite. At the same stage zircon grains were likely to be formed. Some of them trapped liquid СО2 inclusions and syngenetic melted inclusions. The presence of such inclusions points to crystallization of early zircon from СО2-saturated magmas at P ~3.5 kbar. During metamorphism of plagiogneiss protoliths, isometric crystals of zircon cut in a complicated manner were formed. They contained primary inclusions of chloride solutions similar to those in plagioclase and quartz from plagiogneiss. The fluid pressure, assessed by inclusions of water solutions and СО2 rich inclusions in the zircons under study, reached 2.8-4.0 kbar at Т = 540-620°С.
(in Russian, стр.16, fig. 0, tables. 10, ref 12, 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. 2
Skufin P.K., Yakovlev Yu.N.
Geological setting and petrological peculiarities of volcanic rocks from the Majarvi, Pirttijarvi and Orshoaivi Formations in the Kola Superdeep Borehole and in the near-surface zone
The problem of systematics of amphibolite from the Kola Superdeep Borehole (SG-3) Archaean section has been discussed. An integrated petrogeochemical approach allows classifying these rocks with a high degree of reliability and distinguishing among them varieties dated presumably as Archaean and Proterozoic. Proterozoic rocks among the basic rocks in the Archaean section range from 52 to 67 %. Homologues to metavolcanites from the Matert Formation are present among the Proterozoic metamagmatites in the SG-3 Archaean section. This has cast some doubt on the conclusion drawn by N.P. Vinogradova and V.V. Melezhik about the allochthonous origin of the upper layers of the North Pechenga section, including its producing horizons. This is of great importance in terms of metallogeny
(in Russian, стр.25, fig. 5, tables. 13, ref 32, Adobe PDF, Adobe PDF 0 Kb)