HR: 0800h
AN: GP11A-0010    [Abstracts]
TI: Paleomagnetism and K/Ar Dating of Two Cretaceous and Tertiary Localities From Mongolia: Implications on The Large Scale Deformation of Eurasia
AU: * Hankard, F
EM: hankard@ipgp.jussieu.fr
AF: Laboratoire de Paléomagnétisme, Institut de Physique du Globe de Paris & Université Paris 7, 4, Place Jussieu, Paris, 75252 France
AU: Cogné, J
EM: cogne@ipgp.jussieu.fr
AF: Laboratoire de Paléomagnétisme, Institut de Physique du Globe de Paris & Université Paris 7, 4, Place Jussieu, Paris, 75252 France
AU: Quidelleur, X
EM: quidel@geol.u-psud.fr
AF: Laboratoire de Géochronologie Multi-techniques U.P.S. - I.P.G.P., Bat. 504, Sciences de la Terre, Université Paris Sud, Orsay, 91405 France
AU: Lklagvadorj, P
GP11A-0010 AF: Mongolian university of Science and Technology, 8th khoroo, Baga toiruu, Sukhbaatar district, Ulaanbaatar, 210349 Mongolia
AU: Bayasgalan, A
EM: bayas@must.edu.mn
AF: Mongolian university of Science and Technology, 8th khoroo, Baga toiruu, Sukhbaatar district, Ulaanbaatar, 210349 Mongolia
AU: Kravchinsky, V
EM: vkrav@phys.ualberta.ca
AF: Physics Department, University of Alberta, Edmonton, AB, T6G2J1 Canada
AB: The Asian continent has been considered, in the last 20 years, as an exceptional natural laboratory for understanding geodynamic processes involved in intracontinental collision. Great efforts have been made, to sort out the complex history of Asia's amalgamation by successive accretion of lithospheric microblocks since the Cretaceous and profoundly modified by the India-Asia collision during the Tertiary. Numerous Cretaceous paleomagnetic studies constrain the history of the deformation of this mosaic. However, a problem arises with Tertiary data from Central Asia, for which the paleomagnetic inclinations are systematically shallower than those deduced for Central Asia from the European reference apparent polar wander path (APWP). The amount of intracontinental shortening between southwestern mobile blocks (Tibet, Tarim, Qaidam, etc...) and northeastern stable blocks (e.g. Siberia, North and South China...) inferred from the anomalously shallow Cenozoic inclinations is about twice the amount deduced from the Cretaceous data. Geologic evidence supporting such a dramatic shortening does not exist, justifying the acquisition of new high quality reference poles from the northern regions of this system. We present new paleomagnetic results obtained at two localities of Tertiary (Khaton-Sudal; 44.504^oN; 101.364^oE) and Cretaceous (Shovon; 44.424^oN; 103.788^oE) volcanic rocks from the Amuria block. Classical paleomagnetic methods isolated a high temperature component (HTC) carried by magnetite, which allows two new Tertiary and Cretaceous paleopoles to be calculated for this block. These paleopoles are interpreted based on accurate K/Ar ages determined using the Cassignol-Gillot technique applied on carefully isolated groundmass from effusive rocks of the studied localities. Our results should be critical in understanding the low-inclination controversy of Central Asia.
DE: 1525 Paleomagnetism applied to tectonics: regional, global
DE: 8102 Continental contractional orogenic belts and inversion tectonics
DE: 8110 Continental tectonics: general (0905)
DE: 8157 Plate motions: past (3040)
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005