--> Abstract: The First Results of the Dating (U/Pb) and Isotopic-Geochemistry Study of the Detrital Zircons from the Neoproterozoic Sandstones of the Southern Timan, by N. B. Kuznetsov, L. M. Natapov, E. A. Belousova, K. V. Kulikova, A. A. Soboleva, and O. V. Udoratina; #90096 (2009)

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The First Results of the Dating (U/Pb) and Isotopic-Geochemistry Study of the Detrital Zircons from the Neoproterozoic Sandstones of the Southern Timan

Nikolay B. Kuznetsov1, Lev M. Natapov3, Elena A. Belousova3, Ksenia V. Kulikova2, Anna A. Soboleva2, and Oxana V. Udoratina3
1Geological Institute, Moscow, Moscow, Russia.
2Instite of Geology, Komi SC, Syktyvkar, Russia.
3GEMOC, National Key Centre, Facul’tet of Earth and Planetary Sciences, Macquarie University, Sidney, ACT, Australia.

The results of study of detrital zircons (Zr) from clastogenic rocks of the Southern Timan Mts. are presented. Zr grains from red-color quartz-clastic sandstones (51 grains) and aleuro-sandstones (10 grains) of the Djejim-Parma Fm. were investigated. The U/Pb-ages of 61 grains range from ~2,97 to ~1,20 Ga. Geochemical composition of the 47 Zr grains were obtained. We conclude that those Zrs occurred from "granites" (22 grains) and "diorites" (12 grains) or their volcanic equivalents, and from "sienites" (5 grains) and "basites" (8 grains). Model ages of magmatic substratum of parental rocks to zircons (TcDm) were estimated from Lu/Hf-isotope data. Archean in age Zr grains are characterized by TcDm ~ 2.84-3.36 Ga. Some Archean grains have TcDm ~ 2.84 Ga, which are very close to Zr grains age (~2.7-2.8 Ga). So, we conclude the "juvenile" type of the substratum for those Zr grains. TcDm of the Proterozoic Zr grains cover interval ~2,00-3.36 Ga. It specifies that Zr parental rocks were formed during recycling the Archean and Paleoproterozoic continental crust.

Obtained parameters of detrital Zr are rather well correlated to known tectonic-magmatic episodes of geodinamical evolution of Baltica - an ancient skeleton of the East European craton. First of all, the most part ages of Zr grains fall into time interval 1,70-2,05 Ga, which is a time interval of Baltica assembling from crustal blocks Sarmatia, Volgo-Uralia and Fennoscandia.
A probable source (magmatic or/and metamorphic complexes into Baltica) can be specified for all (without exeption) Zr. However, the oldest known for Sarmatia ages reaching 3,7 Ga, do not appear among Zr ages (<3 Ga) or TcDm (<3,36 Ga). This mihgt mean that Djejim-Parma Fm was formed predominantly from erosional products of northern and central parts of Baltica - mostly Fennoscandia and areas of its conjagetion with Sarmatia and Volgo-Uralia. As to erosional products of the southern parts of Sarmatia and Volgo-Uralia, they do not reach Timan margin of Baltica (present-day Timan Mnts).

We interprete Djejim Fm as a relictes of clastic complexes into passive Timan margin of Baltica in which erosional products from Archean, Paleo- and Meso-Proterozoic crystalline complexes of Baltica were accumulated. No any signature that it was any other additional sourse of clastic material were revealed. This work was partially supported by Program N16 of Presidium RAS and RFFI grants 09-05-01033 and 09-05-00812.


AAPG Search and Discover Article #90096©2009 AAPG 3-P Arctic Conference and Exhibition, Moscow, Russia