GGUP SF Mineral

Saint Petersburg, Russia

GGUP SF Mineral

Saint Petersburg, Russia

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Myskova T.A.,Russian Academy of Sciences | Ivanov N.M.,GGUP SF Mineral | Korsakova M.A.,GGUP SF Mineral | Mil'kevich R.I.,Russian Academy of Sciences | And 2 more authors.
Stratigraphy and Geological Correlation | Year: 2013

The geological, geochemical, and isotopic-geochronological data obtained for Sumian moderate-basic metavolcanites of Shombozero and Lekhta structures of the Panayarvi-Vygozero belt shows that the Tunguda Formation is confined to the Paleoproterozoic structural and material complex. This formation is represented by the complex of weakly differentiated andesitobasalts and andesites of calc-alkaline series with higher contents of MgO and moderate contents of Al2O3 and rare earth elements. The rocks of the Tunguda Formation are different from the Late Archean basic rocks of the Hiziyarvi Formation represented mainly by tholeiitic basalts with low REE contents and undifferentiated spectrum of REE distribution. The age of volcanites of the Tunguda Formation was determined to be 2439 ± 21 Ma. The xenogenic zircons from metaandesites of the Tunguda Formation have Neoarchean age according to the 207Pb/206Pb ratio (from 2536 ± 4 to 2825 ± 7 Ma). The Neoarchean zircons, a negative value of e{open}Nd (-3.8), and indicative geochemical parameters are evidence that the crustal component took part in formation of the protolith of the studied rocks. © 2013 Pleiades Publishing, Ltd.


Myskova T.A.,Russian Academy of Sciences | Ivanov N.M.,GGUP SF Mineral | Korsakova M.A.,GGUP SF Mineral | Milkevich R.I.,Russian Academy of Sciences | And 3 more authors.
Stratigraphy and Geological Correlation | Year: 2014

A comparative geochemical, isotopic-geochemical, and geochronological study of Paleoproterozoic acid volcanic rocks and granitoides at the conjunction zone between the Karelian Craton and Belomorian mobile belt was carried out. Acid volcanites comprise the Ozhiyarvi suite (Sumian Superhorizon, Lower Karelian) within the Panayarvi-Vygozero belt of Karelides. In general, the Ozhiyarvi suite is composed of quartz plagioporphyrites, rhyolites, and rhyodacites of the potassium series. Granitoides compose intrusions extending as a parallel belt located northeast of the belt of Karelides. Granitoides are represented by two spatially related associations: early gabbro-diorite-granodiorite-charnockite (vichansky type) and later granosyenite-granite (Topozersky type). Acid volcanites are of Sumian age 2442 ± 17 Ma (U-Pb, SHRIMP-II). The U-Pb age values obtained for granitoides (five determinations, SHRIMP-II) are in the range of 2445 ± 17–2397 ± 30 Ma, which corresponds to the Sumian. General geochemical characteristics of granitoides and acid volcanites are the following: low Al2O3 content, variable low CaO content, higher SiO2 content, higher total alkali with a predominance of K2O over Na2O, low to moderate ferruginosity, and higher Zr, Y, Hf, and Nb contents. These rocks are characterized by a similar distribution of rare and rare earth elements with negative Eu anomaly and distinct minima of Nb, Sr, P, and Y characteristic of A-type granites. The fields of measurement points on the Nb-Y-Ce diagram and Y/Nb and Yb/Ta ratios are evidence that the studied rocks were melted from the continental crust. The studied rocks are characterized by negative ɛNd values (−1.2 to −3.8). Their model age (2.8–3.0 Ga) is much higher than the crystallization age, which may indicate that the magma source had a long geological history. According to similar geochemical peculiarities of granitoides and volcanites, as well as their convergence in space and time, one can suggest that these rocks were melted from the continental sialic crust owing to uplifting of the mantle material into the continental crust; that is, they can be considered to be products of a unified regional magmatic process. © 2014, Pleiades Publishing, Ltd.


Myskova T.A.,Russian Academy of Sciences | Ivanov N.M.,GGUP SF Mineral | Korsakova M.A.,GGUP SF Mineral | Milkevich R.I.,Russian Academy of Sciences | And 2 more authors.
Stratigraphy and Geological Correlation | Year: 2012

During this work, the composition of Sariolian volcanites of the Vermas formationin the Karelian region was studied and the U-Pb age of these rocks was first obtained (SHRIMP-II). In composition these volcanites are andesites and andesite-basalts, as well as, to a lesser extent, trachyandesites and trachyandesitobasalts of the calc-alkaline series. Due to porphyroblast crystallization, widely manifested in this region volcanites are enriched in TiO 2, Al 2O 3, Fe 2O 3total, K 2O, Rb, Cs, Zr, Hf, Y, Nb, Cr, V, Th and REE (primarily La and Ce). Rocks of the Vermas formation formed in the Paleoproterozoic (2412 ± 17 Ma) and were transformed as a result of the Svecofennian metamorphism in the interval of 1970 ± 15 Ma. The source of the melt and inherited zircons with the age of 2630-2760 Ma can be crustal material with the ancient Sm-Nd model age (3-3. 1 Ga). © 2012 Pleiades Publishing, Ltd.

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