New Paleomagnetic Data on the Anabar Uplift and the Uchur-Maya

ISSN 1069-3513, Izvestiya, Physics of the Solid Earth, 2009, Vol. 45, No. 7, pp. 545–566. © Pleiades Publishing, Ltd., 2009. Original Russian Text © R.V. Veselovskiy, V.E. Pavlov, P.Yu. Petrov, 2009, published in Fizika Zemli, 2009, No. 7, pp. 3–24. New Paleomagnetic Data on the Anabar Uplift and the Uchur-Maya Region and Their Implications for the Paleogeography and Geological Correlation of the Riphean of the Siberian Platform R. V. Veselovskiya, V. E. Pavlova, and P. Yu. Petrovb a Institute of Physics of the Earth, Russian Academy of Sciences, ul. Bol’shaya Gruzinskaya 10, Moscow, 123995 Russia b Geological Institute, Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017 Russia Received May 5, 2008; in final form November 20, 2008 Abstract—The results of paleomagnetic studies of the reference sections of the Riphean and Late Proterozoic intrusive bodies of two remote areas of the Siberian Platform are presented. Within the limits of the Uchur- Maya region the sedimentary rocks of the Gonam, Omakhta, Ennin and Konder formations were studied; and the Riphean sedimentary rocks of the Burdur and Kotuykan formations on the northern and western slopes of the Anabar Uplift and, also, the Late Proterozoic intrusive complexes, located in the basins of the Fomich, Magan, Dzhogdzho and Kotuykan Rivers were studied. The paleomagnetic poles obtained in the course of this work and the present-day geochronological data give grounds to assume that: (1) the accumulation of the Riph- ean of the Anabar Uplift occurred after the formation of the Uchurskaya series of the Uchur-Maya region and was completed in approximately 1.5 Ga; (2) the Konder layers, compared according to the correlation pattern accepted at the present time [Semikhatov and Serebryakov, 1983] with the bottoms of the Totta formation, can be related to the appreciably more ancient stratigraphic level; (3) the intrusion of the studied intrusive bodies of the northern and western slopes of the Anabar Uplift occurred nonsimultaneously, although within close time intervals of approximately 1.5 Ga. The estimates of the kinematic parameters of the drift of the Siberian Plat- form within an interval of 1.7–1.0 Ga is carried out. Key words: Paleomagnetism, Siberian Platform, Riphean, Late Proterozoic, Mesoproterozoic, geochronology, stratigraphy, and paleomagnetic pole. PACS numbers: 91.25 Ng DOI: 10.1134/S1069351309070015 INTRODUCTION paleomagnetic poles (including, also, averaging The new isotopic-geochronological data increas- through their analytical approximation). The APWPs ingly frequently contradicts to the traditional concepts are based on the results of the individual paleomagnetic concerning the Precambrian geological history of vari- determinations: the larger their number and the higher ous key regions and reference sections [Khomen- their quality, the more reliable the corresponding tovskii, 2005; Khudoley, 2003], and with renewed APWP. vigor raise the question about the framework of the The new paleomagnetic determinations presented in applicability in the Precambrian of the traditional his- this work, obtained by us for the Riphean rocks of the torical-geological and biostratigraphic methods. In this Anabar Uplift and the Uchur-Maya region, on the one situation, the vital need of applying the paleomagnetic hand, are intended to make a contribution to the devel- method is obvious, which gives independent informa- opment of the Mesoproterozoic segment of the APWP tion. This information can be of great significance for of the Siberian Platform and, on the other hand, even the comparison and correlation of sections, for dating now they can be used for solving a number of problems species, and for the solution of different paleogeo- of the stratigraphy and the paleogeography of Siberia. graphic and paleotectonic problems. An important, if not the basic instrument of paleo- GEOLOGICAL CHARACTERISTICS magnetic studies of the Precambrian, are the apparent AND THE AGE OF THE OBJECTS STUDIED polar wander path (APWPs) and the development of Paleo- and Mesoproterozoic segments, which are The position of the areas under study is schemati- becoming increasingly urgent. The APWPs are the time cally shown on the diagram of the Siberian Platform series of either the individual or somehow averaged (Fig. 1). More detailed geological diagrams with the 545 546 VESELOVSKIY et al. et al., 2006]. Thus, the available isotopic datings make it Popigai River possible to state that the larger part of the Anabar Riphean 4 was accumulated within the interval between 1690–1380 Ma. This conclusion does not contradict the paleontologi- Lena River 3 cal [Sergeev, 2003; 2005] and chemostratigraphical data [Knoll et al., 1995]. Kotui Anabar Massif the western wing of the Anabar River In the limits of Uplift (Fig. 3), in the valleys of the Magan, Dzhogdzho, Lower Tunguska River Vilui River and Kotuykan Rivers, the intrusive magmatic complex 5a was studied, which is represented by dikes and sills of dol- Lena RiverRiver erites, intruding on the dolomites of the Kotuykan and Yusmastakh Formations. Over approximately 150 km, Aldan 5b 15 intrusions were sampled. From each body 10–20 Angara River Aldanian oriented samples were selected; in a number of cases, shield the contact zones of intrusions with the host rock were also tested. K/Ar datings, obtained earlier only for two sills and dikes intersecting them of the Dzhogdzho 0 500 km River (Fig. 3, points 4–7, 70), fall in the range from Lake Baikal 1397 ± 4 to 1007 ± 12 Ma [Shpunt et al., 1982]. Accord- ing to [Okrugin, 1999], all intrusive bodies studied by Fig. 1. Map-diagram of the Siberian Platform with the noted us are related to the region of development of the West- position of the study areas: (3) the western slope of the Ana- ern-Anabar dike cluster, which was formed in an inter- bar Uplift (Fig. 3); (4) the northern slope of the Anabar val of 1400–900 Ma. For paleomagnetic studies the Uplift (Fig. 4); the Uchur-Maya region: (5a) the Bol’shoi Aim River, (5b) the Idyum, Gonam, Uchur, and Algama sandstones of the Burdur, Labaztakh, and Ust-Il’ya Rivers (Fig. 5). Formations in the Magan River valley were also tested. On the northern slope of the Anabar Uplift (Fig. 4) in the Fomich River valley, sills with a thickness of sev- investigated outcrops superimposed on them, are pre- eral tens of meters and rare thin (up to 25 m) dikes, sented in Figs. 3–5. composed of dolerites, were sampled. Over more than 150 km, at 15 points, eight intrusive bodies were sampled. In each of them, not less than ten oriented samples The Northern and Western were selected. The intrusive bodies of this region relate slopes of the Anabar Uplift to the North-Anabar dike cluster, whose age is evalu- The central part of the Anabar Uplift is composed of ated in the work [Okrugin, 1999] as 1300-900 Ma. To the high metamorphized Archean and Early Proterozoic obtain a more specific dating, from the intrusive body, rocks, which on its periphery are overlapped by the Riph- investigated by us at points 12 and 13, geochemical ean–Paleozoic sedimentary cover. Here, the terrigenous samples were selected, whose Sm/Nd isotopic age was Mukun and terrigenocarbonate Billyakh series, which bed 1513±51Ma [Veselovskiy et al., 2006]. For the paleo- monoclinally with dip angles of several degrees and at some magnetic analysis the red-colored sandstones of the places contain dikes and sills of the Late Proterozoic age, Burdur Formation (points 11 and 26) and the multicol- are distinguished in the composition of the Riphean [Okru- ored dolomites of the Kotuykan Formation (points 24 gin, 1999; Shpunt et al., 1982] (Fig. 2b). and 25) were sampled. For conducting the baked-con- The datings of the fragmental zircons from the bot- tact test dikes, which intruded on the rocks of both the toms of the Mukun series indicate that its accumulation Burdur (point 11) and the Kotuykan (points 24 and 25) began not earlier than 1690 ± 9 Ma [Khudoley et al., Formations, were sampled. 2007], but judging by the rubidium–strontium and potassium–argon datings of glauconites from the base The Uchur-Maya region (Fig. 5) of the Billyakh series [Gorokhov et al., 1991], was completed up to 1400 Ma ago. Rb/Sr isotopic data on For the Riphean rock masses of the Uchur-Maya the argillites of the Yusmastakhsk formation indicate region and magmatic bodies embedded in them the that the Billyakh series was formed up to 1250 Ma ago present-day isotopic determinations are few in number [Gorokhov et al., 2001]. The U/Pb determination executed (Fig. 2b). In the lower horizons of the Uchur series the by Ernst together with co-authors [Ernst et al., 2000] of the fragmental zircons with a U/Pb age of 1717 ± 32 Ma are isotopic age based on the baddeleyite dikes on the eastern found [Khudoley et al., 1999; 2001], and the dike, slope of the Anabar Uplift, intruding on the lower part of the intruding on these horizons, has a Sm/Nd age of 1339 ± Yusmastakh Formation [Khudoley, 2003], is 1384 ± 2 Ma. 54 Ma [Khudoley et al., 2007]. The youngest granitoid The determination of the isotopic age of the intrusive body rocks of the Ulkanskii graben, overlapped by the Uchur of the Fomich River valley (the Sm/Nd method) intruding series, have an isochronous U/Pb age obtained for zir- on the Ust-Il’ya Formation is 1513 ± 51 Ma [Veselovsky con of 1703 ± 18 Ma [Neimark et al., 1992]. The sand- IZVESTIYA, PHYSICS OF THE SOLID EARTH Vol. 45 No. 7 2009 NEW PALEOMAGNETIC DATA ON THE ANABAR UPLIFT 547 V (a)V (b) V Uy Uy Uy series series series ig ig ig R3 series series series nr nr nr Lakhanda Lakhanda Lakhanda V zp zp zp 1384± 2() 4 ml ml us ml series series series Kerpyl Kerpyl Kerpyl V tt tt series tt R 1 Billyakh 2 kt () 1493± 34() 3 < 1100 8 ul 1513± 51() 2 us sv sv sv 2 lb 2 Aim Aim series Aim km series series br series series tl Billyakh tl tl kt il Mukun <911690± () <4271394± () 1.0 2 en ul en en lb 2 R1 0.5 om br om om series series Uchur series Uchur Uchur series Mukun ± () gn gn gn 1339 54 6 il <3251717± () 0 The first variant The second variant Fig.

Load more