Search

Results:

Vol. 10 (2007 year), No. 1

Chupin V.P., Sorokina G.A., Vetrin V.R.,
On the genesis of zircon from Archaean plagiogneiss of the Kola Superdeep Borehole (thermobarogeochemical data)

The data on geochemical and structural-mineralogical peculiarities of rock-forming minerals from the homologous sedimentary rocks of the Luchlompolo sedimentary Formation were the result of investigation of SG-3 deep rocks, their surface and near-surface homologues. Each of these groups has the same stratigraphic position of samples but a different depth level. These minerals are microclines, carbonates and quartzes. The surface and near-surface samples of microclines, carbonates and quartzes have identical composition and spectroscopy data. But in the context of crystal structure defects they have noticeable distinctions as compared with abyssal homologues. The revealed structural distinctions for microclines and dolomites are manifested in the degree of crystal structure defects: it decreases with depth for microclines and increases for dolomites. This is caused by a different metamorphism grade. The distribution of admixture Mn-ions in the possible structural sites of dolomite may be caused by the combined influence of metamorphism and a "depth factor". Displacement of isomorphism of Al admixture centres in quartz in the direction of alkaline varieties, with increase of the depth level, is connected with an analogous process. The tendencies of decreasing the natural part of paramagnetic Al-centres and oxygen vacancy concentrations in quartz with depth can be explained by the "depth factor".

(in Russian, стр.8, fig. 4, tables. 2, ref 16, Adobe PDF, Adobe PDF 0 Kb)

Vol. 15 (2012 year), No. 2

Vetrin V.R., Yakovlev Yu.N., Chupin V.P.
Sources of the terrigenous material in the formation of metasedimentary rocks of the Archaean basement of the Paleoproterozoic Pechenga structure

The basement of the Paleoproterozoic Pechenga structure was cored by the Kola Superdeep Borehole SD-3 at the depths of 6842-12262 m. It consists of alternating strata of metavolcanic dacite, plagiorhytodacite rocks and high-alumina gneisses; the protoliths of these rocks corresponded mainly to graywackes. Resulting from the examination of zircons from metaterrigenous rocks of the 1st, 3rd, and 9th strata of the SD-3, the detrital, anatectic, metamorphogenic, and contact-metasomatic genetic types have been identified. Detrital zircons include several age groups. The most homogeneous, i.e., comparable to zircons from tonalite gneisses (bottoms of the SD-3 section) and from surrounding rocks, zircons have appeared to be those from gneisses of the deepest 9th stratum. The data on the age of these zircons, along with a poor rounding of the grains, signify formation of the host gneisses' protoliths owing to washing out and redeposition of material. Widening of alimentation areas, which supplied terrigenous material into sedimentation basins, took place during formation of alumina gneisses of the 3rd and especially 1st strata of the section.

(in English, стр.6, fig. 3, tables. 1, ref 14, Adobe PDF, Adobe PDF 0 Kb)