Paleomagnetic dating of Phanerozoic kimberlites in Siberia |
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| Institution: | 1. Department of Physics, University of Alberta, Edmonton, Alberta, Canada T6G 2E1;2. Amakinskaya expedition, Diamonds Russia-Sakha Enterprise, Aikhal 678190, Russia;3. Department of Physics, Royal Military College of Canada, Kingston, Ontario, Canada;1. Planetary Geosciences Institute, Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN 37996, USA;2. Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada;3. V.S. Sobolev Institute of Geology and Mineralogy, Russian Academy of Sciences, Siberian Branch, Novosibirsk, Russia;1. Institute of Geology and Mineralogy SD RAS, Koptyug ave 3, Russian Federation, 630090 Novosibirsk, Russia;2. Institute of Geochemistry SD RAS, Irkutsk, Russia;3. Vienna University, A-1090 Vienna, Austria;4. Alrosa Stock Company, Mirny, Russia;5. Birkbeck College, University of London, UK;6. Institute of Geology of Diamond and Noble Metals SD RAS, Yakutsk, Russia;1. Vinogradov Institute of Geochemistry SB RAS, Favorskogo str. 1A, Irkutsk 664033, Russia;2. Institute of Geology and Geophysics, Chinese Academy of Sciences, 19 Beitucheng West Road, Chaoyang, Beijing 100029, China;3. Institut für Mineralogie und Kristallographie, Universität Wien, Althanstr. 14, 1090 Wien, Austria;1. School of Physical Sciences, University of Tasmania, Hobart, TAS 7001, Australia;2. ARC Centre of Excellence in Core to Crust Fluid Systems/GEMOC, Department of Earth & Planetary Sciences, Macquarie University, NSW 2109, Australia;3. School of Earth Sciences, University of Melbourne, VIC 3010, Australia;4. Central Science Laboratory, University of Tasmania, Hobart, TAS 7001, Australia |
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| Abstract: | Diamond bearing kimberlite pipes are exposed across the north-central part of the Siberian platform. Three main time intervals are considered to be the age of emplacement: the Devonian–Early Carboniferous, Triassic, and Cretaceous. However, isotopic age data from of the pipes are scattered and provide a very broad age interval for the magmatic activity. New paleomagnetic poles from four kimberlite pipes (Eastern Udachnaya, Western Udachnaya, International and Obnazhennaya) are obtained to estimate their paleomagnetic age. The mean primary magnetization directions for the pipes are as follows: D = 4.3°, I = ? 44.5° (k = 29.4, α95 = 7.4°, N = 14); D = 340.5°, I = ? 65.6° (k = 12.9, α95 = 19.4°, N = 6); D = 291.1°, I = ? 78.1° (k = 27.5, α95 = 14.9°, N = 5); and D = 306.7°, I = ? 82.6° (k = 38.4, α95 = 5.8°, N = 17), respectively. On the basis of a comparison with the Siberian apparent polar wander path (APWP) we estimate the age of kimberlite magmatism, assuming primary magnetizations in these rocks. The paleomagnetic ages are as follows: 428 ± 13 Ma for Eastern Udachnaya; 251 ± 30 Ma for International pipe; and 168 ± 11 Ma for Obnazhennaya pipe. The Western Udachnaya pipe was remagnetized and no clear paleomagnetic age could be determined. The ages of magmatic activity span the Early Silurian to Middle Late Jurassic. Early Silurian magmatism could be associated with the formation of the Viluy rift. Middle to Late Jurassic magmatic activity is most likely related to subduction related to the accretion of surrounding terranes to Siberia. |
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