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1.
A. A. Kalinin T. V. Kaulina L. M. Lyalina D. V. Elizarov P. A. Serov 《Geology of Ore Deposits》2016,58(7):594-599
On the basis of U–Pb, Rb–Sr and Sm–Nd isotopic data, it is shown that formation of uranium mineralization in the Paleoproterozoic Salla-Koulajarvinsky belt (Northern Karelia) was a long-lasting mult-stage process that developed over more than 1 Ga: from the Paleoproterozoic to the Paleozoic. The first stage, 1.75 Ga ago, corresponds to the Svekofennian metamorphic event—regional albitization. The process was dated by the Rb–Sr (isochronic age of albitites is 1754 ± 39 Ma) and U–Pb methods (the age of rutile is 1756 ± 8 Ma). At this stage, with a lower temperature limit of 400–450°C, conditions were favorable for the mobilization and migration of uranium, but not for its deposition in minerals. The second stage, 1.62 Ga ago, was a time of alteration of rocks at the regressive stage of the Svekofennian metamorphic event, when carbonate and chlorite rocks formed after albitites. The age of this stage was estimated as 1627 ± 42 Ma according to ThO2, UO2, and PbO contents in uraninite. Probably, the deposition of uraninite took place at this stage at temperature not higher than 300–350°C. The final, third stage, 385 Ma ago, corresponds to the Paleozoic tectonic activation and formation of Caledonian alkaline intrusions. Uranium minerals were probably redeposited at this stage; the U–Pb age of brannerite is 385 ± 2 Ma. 相似文献
2.
Steshenko E. N. Nikolaev A. I. Bayanova T. B. Drogobuzhskaya S. V. Chashchin V. V. Serov P. A. Lyalina L. M. Novikov A. I. Elizarov D. V. 《Doklady Earth Sciences》2018,479(1):366-370
Doklady Earth Sciences - The rocks and minerals of the Kolvitsa massif are studied by complex isotopic–geochronological and geochemical (U–Pb, Sm–Nd, REE contents of zircons)... 相似文献
3.
A. A. Kalinin O. V. Kazanov N. M. Kudryashov G. F. Bakaev S. V. Petrov D. V. Elizarov L. V. Lyalina 《Geology of Ore Deposits》2017,59(6):453-481
Data on gold ore objects in the Strelna Greenstone Belt in the southeastern Kola Peninsula are presented in the paper. The studied Vorgovy and Sergozero ore occurrences are localized in the zone of tectonic contact of the Neoarchean complexes making up the greenstone belt and the volcanic–sedimentary sequences of the Paleoproterozoic Imandra–Varzuga Zone. The Vorgovy gold occurrence is related to stockwork of carbonate–quartz veins and veinlets hosted in a biotite gneiss transformed into chlorite–sericite–quartz metasomatic rock with pyrrhotite–arsenopyrite dissemination. The Sergozero occurrence is localized in amphibolites corresponding to komatiitic and tholeiitic basalts hosted in biotite gneiss (metapelite). Mineralization is confined to the zone of tectonized contact between komatiitic and tholeiitic basalts, where it is controlled by a strip of metasomatic biotite–calcite rock with gersdorffite–arsenopyrite dissemination. The native gold grains medium to high in fineness are up to 0.1 mm in size and mainly localized at the contact of arsenopyrite and gersdorffite with gangue minerals. Gold mineralization is of superimposed character, and, as indicated by isotopic geochronology, was formed at the retrograde stage of the Svecofennian regional metamorphism. Comparison of ore occurrences localized in the Strelna Greenstone Belt with gold deposits in greenstone belts of the western Fennoscandian Shield and the Superior Province in Canada allows us to suggest a high perspective of the entire Strelna Belt for gold. 相似文献
4.
A. I. Nikolaev S. V. Drogobuzhskaya T. B. Bayanova T. V. Kaulina L. M. Lyalina A. I. Novikov E. N. Steshenko 《Doklady Earth Sciences》2016,470(2):1037-1041
The results of the LA-ICP-MS analysis of the concentrations of REEs, U, Th, and Hf in zircon from Paleo- and Neoarchean reference rocks of the Kola region (garnet–amphibole gneiss, basic and acid granulites, and granite pegmatite) are reported. A new methodology of the study of accessory zircons has been validated and modified. The accuracy of the results is confirmed by analysis of standard zircons Temora 1 and 91 500 and by comparison with the data obtained in other laboratories. 相似文献
5.
Doklady Earth Sciences - 相似文献
6.
M. Z. Glukhovskii M. I. Kuz’min T. B. Bayanova L. M. Lyalina V. A. Makrygina T. F. Shcherbakova 《Doklady Earth Sciences》2017,476(1):1026-1032
For the first time in Russia, a Hadean zircon grain with an age of 3.94 Ga (ID-TIMS) has been discovered in high-aluminous garnet granulites of the Aldan Shield among the U–Pb zircons with an age from 1.92 Ga. In this connection, the problems of its parental source, the petrogenesis of granulites that captured this zircon, and the mechanism of occurrence of these deep rocks in the upper horizons of the crust have been solved. The comparison of the geochemistry of garnet granulites and the middle crust has shown that the granulites are enriched in the entire range of rare-earth elements (except for the Eu minimum), as well as in Al2O3, U, and Th and are depleted in the most mobile elements (Na, Ca, Sr). In the upper part of the allitic weathering zone of the middle crust, which formed under conditions of arid climate, this zircon grain was originated from the weathered granites from the middle crust. In the latter case, they were empleced discretely in the upper granite–gneiss crust under high pressure conditions (the rutile age is 1.83–1.82 Ga). The zircon with an age of 3.94 Ga is comparable to the Hadean zircons from orthogneisses of the Acasta region (Canadian Shield, 4.03–3.94 Ga). 相似文献
7.
8.
The Sakharjok Y-Zr deposit in Kola Peninsula is related to the fissure alkaline intrusion of the same name. The intrusion
∼7 km in extent and 4–5 km2 in area of its exposed part is composed of Neoarchean (2.68–2.61 Ma) alkali and nepheline syenites, which cut through the
Archean alkali granite and gneissic granodiorite. Mineralization is localized in the nepheline syenite body as linear zones
200–1350 m in extent and 3–30 m in thickness, which strike conformably to primary magmatic banding and trachytoid texture
of nepheline syenite. The ore is similar to the host rocks in petrography and chemistry and only differs from them in enrichment
in zircon, britholite-(Y), and pyrochlore. Judging from geochemical attributes (high HSFE and some incompatible element contents
(1000–5000 ppm Zr, 200–600 ppm Nb, 100–500 ppm Y, 0.1–0.3 wt % REE, 400–900 ppm Rb), REE pattern, Th/U, Y/Nb, and Yb/Ta ratios),
nepheline syenite was derived from an enriched mantle source similar to that of contemporary OIB and was formed as an evolved
product of long-term fractional crystallization of primary alkali basaltic melt. The ore concentrations are caused by unique
composition of nepheline syenite magma (high Zr, Y, REE, Nb contents), which underwent subsequent intrachamber fractionation.
Mineralogical features of zircon-the main ore mineral—demonstrate its long multistage crystallization. The inner zones of
prismatic crystals with high ZrO2/HfO2 ratio (90, on average) grew during early magmatic stage at a temperature of 900–850°C. The inner zones of dipyramidal crystals
with average ZrO2/HfO2 = 63 formed during late magmatic stage at a temperature of ∼500°C. The zircon pertaining to the postmagmatic hydrothermal
stage is distinguished by the lowest ZrO2/HfO2 ratio (29, on average), porous fabric, abundant inclusions, and crystallization temperature below 500°C. The progressive
decrease in ZrO2/HfO2 ratio was caused by evolution of melt and postmagmatic solution. The metamorphic zircon rims relics of earlier crystals and
occurs as individual rhythmically zoned grains with an averaged ZrO2/HfO2 ratio (45, on average) similar to that of the bulk ore composition. The metamorphic zircon is depleted in uranium in comparison
with magmatic zircon, owing to selective removal of U by aqueous metamorphic solutions. Zircon from the Sakharjok deposit
is characterized by low concentrations of detrimental impurities, in particular, contains only 10–90 ppm U and 10–80 ppm Th,
and thus can be used in various fields of application. 相似文献
9.
Doklady Earth Sciences - The U, Th, and 4He contents of meliphanite correspond to an age of metamorphism (1800 Ma) indicating good preservation of radiogenic 4He in mineral but contradicting the... 相似文献