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Geodynamics of the Mongol-Okhotsk belt in NE Mongolia

English title Geodynamics of the Mongol-Okhotsk belt in NE Mongolia
Applicant Winkler Wilfried
Number 113645
Funding scheme Project funding
Research institution Geologisches Institut ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Geology
Start/End 01.10.2006 - 31.12.2008
Approved amount 217'926.00
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Keywords (17)

Mongolia; Mongol-Okhotsk belt; collisional belt; geodynamics; terranes; pre-and post-collisional sediments; Central Asian Orogenic Belt; Devonian-Jurassic; sedimentary record; stratigrapghy; sedimentology; provenance analysis; heavy minerals; detrital zircon U/Pb dating; plate tectonic evolution; Devonian-Jurassic terranes; detrital zircon U/Pb laser ablation ICMS dating

Lay Summary (English)

Lead
Lay summary
Mongolia lies in the heart of the Central Asian Orogenic Belt or Altaid Tectonic Collage, depending on the terminology of authors. It is a spectacular example of long lasting orogenic continental growth from Late Proterozoic until Jurassic. In a recent overview of tectono-stratigraphic units, Badarch et al. (2002) recognized in this country 44 non-metamorphic and partly metamorphosed terranes (we prefer the term blocks because the “exotic” nature is not always constrained).

The project carries out a detailed study of Mongol-Okhotsk belt in NE Mongolia. This belt extends from central Mongolia across eastern Siberia towards the Okhotsk Sea in the northwestern Pacific. Earlier workers suggested that it formed in a late stage of Jurassic orogeny in the Central Asian Orogenic Belt during the final consumption of the proto-Okhotsk ocean.

In order to constrain and/or modify previously described geodynamic models for the Mongol-Okhotsk belt, in particular we investigate the sedimentary formations that are comprised within the suture zone and the adjacent tectono-stratigraphic units (blocks). According to our working idea, sedimentary systems closely record with their facies, detrital content, inferred depositional environment, their stratigraphic age and bedding relationships with either basement or sedimentary formations, the contemporaneous tectonic processes of basin formation and inversion. The combined approach of (1) genetic facies analysis, (2) quantitative provenance analysis (sandstone framework grains, heavy minerals - enhanced by microprobe single grain analyses), and (3) single detrital zircon grain U/Pb laser ablation ICPMS dating (reflecting the age of source rocks) is expected to provide a clear description of the supplying source terranes, and an improved framework of the involved sedimentary systems. These analyses eventually will be complemented by radiometric dating (40Ar/39Ar, zircon U/Pb SHRIMP) on associated basement rocks. The obtained data will be synthesized into a geodynamic model for the Mongolian occurrence of the belt, which will be discussed in the larger frame of the Central Asian Orogenic Belt.

The preliminary results suggest that the Devonian-Jurassic Okhotsk ocean temporarily was fringed to the N (Hangai-Hentei zone) and S (South Hentei zone) by active continental margins. The identified turbiditic fore-arc series depict different periods of subduction-related volcanism. Along the northern margin Devonian subduction prevailed, whereas the southern margin at that time possibly represented a passive continental margin. The southern margin turned to an active continental margin during the Carboniferous and Permian.
Direct link to Lay Summary Last update: 21.02.2013

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105168 Cretaceous and Tertiary geodynamic evolution of the Andean forearc in Ecuador 01.10.2004 Project funding
121712 Geodynamics of the Mongol-Okhotsk belt in NE Mongolia 01.01.2009 Project funding

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