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Paleomagnetism of the Teel basalts from the Zavkhan Terrane; implications for Paleozoic paleogeography in Mongolia and the growth of continental crust

T. M. Kilian, N. L. Swanson-Hysell, U. Bold, J. Crowley and F. A. Macdonald
Paleomagnetism of the Teel basalts from the Zavkhan Terrane; implications for Paleozoic paleogeography in Mongolia and the growth of continental crust
Lithosphere (October 2016) 8 (6): 699-715

Abstract

A narrow extensional basin on the Zavkhan terrane of Mongolia exposes a >1.8-km-thick succession of basalt flows within the Teel Formation, along with rhyolites and interflow sediments. We present new U-Pb zircon ages of 446.03 + or - 0.21 Ma (chemical abrasion-isotope dilution-thermal ionization mass spectrometry) on a rhyolite in the Teel Formation and 286 + or - 5 Ma (laser ablation-inductively coupled plasma-mass spectrometry) on a nearby granitic intrusion (Tonkhil Complex). New paleomagnetic data yield a magnetite remanence that is likely primary, acquired during cooling of flows. The mean direction is statistically improved after tilt corrections; however, the tilt test significance is limited given the low variation in tilt between flows. We interpret a second remanence, held by hematite, as an overprint that was likely acquired later in the Paleozoic Era. The tilt-corrected magnetite direction implies a paleolatitude of approximately 20 degrees , while the hematite overprint is equatorial in both geographic and tilt-corrected coordinates. The ca. 446 Ma Teel remanence is consistent with an Ordovician paleogeographic position near Siberia; however, the hematite direction requires subsequent drift to the equator, indicating that these Mongolian terranes were not continuously connected to Siberia, which moved away from the tropics during the Paleozoic Era. This result is consistent with biogeographic constraints and a previously proposed model wherein Amuria traveled with North China during the Permian Period and collided with Siberia during the Jurassic to Triassic closure of the Mongol-Okhotsk Ocean. In this model, continental growth occurred through the collision and oroclinal buckling of a ribbon continent rather than long-lived accretion on the margin of a major craton.


ISSN: 1941-8264
EISSN: 1947-4253
Serial Title: Lithosphere
Serial Volume: 8
Serial Issue: 6
Title: Paleomagnetism of the Teel basalts from the Zavkhan Terrane; implications for Paleozoic paleogeography in Mongolia and the growth of continental crust
Affiliation: University of California at Berkeley, Department of Earth and Planetary Science, Berkeley, CA, United States
Pages: 699-715
Published: 20161012
Text Language: English
Publisher: Geological Society of America, Boulder, CO, United States
References: 85
Accession Number: 2016-096758
Categories: StratigraphySolid-earth geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables, geol. sketch maps
N46°49'60" - N47°04'60", E95°19'60" - E95°45'00"
Secondary Affiliation: Harvard University, USA, United StatesBoise State University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201647
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