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Hydrothermal
mineralization features of alkali magmatic rocks of North-Pripyat
magmatism area
N.D.
Mikhailov, A.G. Laptsevich
Republican
unitary enterprise “Belarusian Research & Development geological
prospecting institute”, Minsk, Republic of Belarus
mihailov@geology.org.by
Magmatic rocks of North-Pripyat area resume in the north-eastern
direction the territorially uniform Pripyat area of rift magmatism
extending beyond the bounds of Pripyat graben.
Within the territory of this area 2 types of hydrothermal (catagenetic)
mineralization are identified. The former type as to the composition of
mineral association(with certain exceptions) and isotopic-geochemical
properties of minerals is congruent with the hydrothermal association of
the eastern zone of Pripyat graben. The composition of hydrothermal
mineral associations includes quartz, calcite, dolomite, barite,
celestine, hematite, pyrite, chalcopyrite, bornite, antimonite. A
certain composition variation of the association is observed within the
bounds of North-Pripyat area depending on the location.
The latter type of mineralization is to some extent similar in its
manifestation to halocatagenetic rock mineralization peculiar within the
bounds of Pripyat trough which is evidenced in the rocks occurring lower
than evaporate sediments. The distinction lies in the composition of
host rocks – magmatic ones (North-Pripyat area) which provide the
mineralization of the given type with intriguing character.Also the
distinction consists in the mineral association detected in the borehole
cores of the localities prospected for diamonds which is registered in
considerable shows of quartz, hematite, sulfides and occasionally
fluorite. Most probably in terms of depositional environment the given
mineralization has a polygenetic character where both halocatagenetic
and hydrothermal processes were in action. Its specific feature is a
sharp prevalence of gypsum in the composition of rock associations and
predominantly fractural type of localization in the form of vertical,
subvertical and lenticular stringers and pockets. All this is indicative
of postmagmatic activity of fault tectonics in North-Pripyat zone, which
lasted at least up to the Post-Frasnian time. Postmagmatic activity
apparently displayed itself not only in the rock fracturing but also in
hydrodynamic and palaeotemperatural aspects which is confirmed by both
the composition of mineralization and by the geochemical dataof
minerals.
The study of mineralogical and geochemical specific features of
sulfate-type mineralization of North-Pripyat area makes it possible to
assume at least 2 mechanisms of its formation: a) through the
dissolution of sulfate member of Narovsky horizon (D2nr) with
hydrothermal solutions and further sulfate crystallization in the form
secondary minerals in the overlying igneous rocks; b) the formation of
secondary sulfate-containing associations during halocatagenesis owing
to palaeobrines of evlanov-livensky evaporate sediments. A similar type
of gypseous secondary mineralization is observed in
volcanogenic-sedimentary rocks in Arkhangelsk diamondiferous province (Bogatikov
and others, 1999). But in this casethe Permian saliferous sediments
frequently overlapping the Devonian volcanogenic-sedimentary formations
might have servedas a meditated sulfate source served.
The paper is executed with financial support from the Belarusian
Republican Fund of fundamental Research-Russian Fund of Fundamental
Research
Х12Р
– 058.
References:
1. Mikhailov N.D. and others, Stratigraphic significance of gypsum
manifestations in volcanogenic rocks of North-Pripyat area. //
Stratigraphy and palaeontology of geological formations of Belarus. –
Minsk, 2003 – P. 197-201
2. Bogatikov O.A. and others. Arkhangelsk diamondiferous province.Moscow
– 1999 – P. 524. |