GRANITOIDS IN THE BOLSHEZEMELSKAYA ZONE OF THE PECHORA BASIN BASEMENT: COMPOSITION AND U-Pb AGE
V.L. Andreichev1, A.A. Soboleva1, E.G. Dovzhikova2, Yu.L. Ronkin3, E.L. Miller4, M.A. Coble4
1N.P. Yushkin Institute of Geology, Komi Science Center, Ural Branch of the Russian Academy of Sciences, Syktyvkar, Russia
2Ukhta State Technical University, Ukhta, Russia
3Zavaritsky Institute of Geology and Geochemistry, Ural Branch of the Russian Academy of Sciences, Yekaterinburg, Russia
4Stanford University, Stanford, United States
Keywords: Pechora Basin, Bolshezemel crustal block, basement, granites, zircon, U-Pb age
Abstract
We present the U-Pb (secondary-ion mass spectrometry, SHRIMP-RG) zircon ages and geochemical characteristics of granitoids penetrated by two boreholes at a depth of about 4.5 km in the Bolshezemel zone-the northeasternmost block of the Pechora Basin basement. The age of zircon from granites from the 26-East Khar’yaga borehole is 558 ± 6 Ma. These granites are similar in composition and age to syncollisional granites of the Charkayu granite-granodiorite complex of the Pripechora fault (suture) zone (555-544 Ma). Dating of zircon from granodiorite from the 2-Veyak borehole yielded an age of 607 ± 6 Ma. Potassium-rich granodiorites and granosyenites from this borehole have geochemical features of within-plate granites and are correlated with granites (602-595 Ma) of the southeastern part of the Izhma crustal block of the basement, which is supposed to be a submerged part of the northeastern passive margin of the Baltica paleocontinent.
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