Subduction and exhumation mechanisms of ultra‐high and high‐pressure oceanic and continental crust at Makbal (Tianshan, Kazakhstan and Kyrgyzstan)

M. Meyer; R. Klemd; E. Hegner; D. Konopelko

doi:10.1111/jmg.12097

journal article Aug 18, 2014

Subduction and exhumation mechanisms of ultra‐high and high‐pressure oceanic and continental crust at Makbal (Tianshan, Kazakhstan and Kyrgyzstan)

M. Meyer R. Klemd E. Hegner D. Konopelko

Journal of Metamorphic Geology Vol. 32 No. 8 pp. 861-884 · Wiley

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Abstract

AbstractThe Makbal Complex in the northern Tianshan of Kazakhstan and Kyrgyzstan consists of metasedimentary rocks, which host high‐P (HP) mafic blocks and ultra‐HP Grt‐Cld‐Tlc schists (UHP as indicated by coesite relicts in garnet). Whole rock major and trace element signatures of the Grt‐Cld‐Tlc schist suggest a metasomatized protolith from either hydrothermally altered oceanic crust in a back‐arc basin or arc‐related volcaniclastics. Peak metamorphic conditions of the Grt‐Cld‐Tlc schist reached ~580 °C and 2.85 GPa corresponding to a maximum burial depth of ~95 km. A Sm‐Nd garnet age of 475 ± 4 Ma is interpreted as an average growth age of garnet during prograde‐to‐peak metamorphism; the low initial εΝd value of −11 indicates a protolith with an ancient crustal component. The petrological evidence for deep subduction of oceanic crust poses questions with respect to an effective exhumation mechanism. Field relationships and the metamorphic evolution of other HP mafic oceanic rocks embedded in continentally derived metasedimentary rocks at the central Makbal Complex suggest that fragments of oceanic crust and clastic sedimentary rocks were exhumed from different depths in a subduction channel during ongoing subduction and are now exposed as a tectonic mélange. Furthermore, channel flow cannot only explain a tectonic mélange consisting of various rock types with different subduction histories as present at the central Makbal Complex, but also the presence of a structural ‘dome’ with UHP rocks in the core (central Makbal) surrounded by lower pressure nappes (including mafic dykes in continental crust) and voluminous metasedimentary rocks, mainly derived from the accretionary wedge.

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Cited By

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Multi-stage metamorphic evolution and protolith reconstruction of spinel-bearing and symplectite-bearing ultramafic rocks in the Zheltau massif, Southern Kazakhstan (Central Asian Orogenic Belt)

Anfisa V. Pilitsyna, Andrey A. Tretyakov · 2018

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Metrics

27

Citations

104

References

Details

Published: Aug 18, 2014
Vol/Issue: 32(8)
Pages: 861-884
License: View

Authors

M

M. Meyer

GeoZentrum Nordbayern Universität Erlangen‐Nürnberg Schlossgarten 5a D‐91054 Erlangen Germany

R

R. Klemd

GeoZentrum Nordbayern Universität Erlangen‐Nürnberg Schlossgarten 5a D‐91054 Erlangen Germany

E

E. Hegner

Department für Geo‐ und Umweltwissenschaften and GeoBio‐Center Universität München Theresienstraße 41 D‐80333 Munich Germany

D

D. Konopelko

Geological Faculty St. Petersburg State University 7/9 University Embankment St. Petersburg 199034 Russia

Funding

Deutsche Forschungsgemeinschaft Award: KL692/17-3

Saint Petersburg State University Award: 3.38.137.2014

UNESCO-IUGS

Cite This Article

M. Meyer, R. Klemd, E. Hegner, et al. (2014). Subduction and exhumation mechanisms of ultra‐high and high‐pressure oceanic and continental crust at Makbal (Tianshan, Kazakhstan and Kyrgyzstan). Journal of Metamorphic Geology, 32(8), 861-884. https://doi.org/10.1111/jmg.12097

Subduction and exhumation mechanisms of ultra‐high and high‐pressure oceanic and continental crust at Makbal (Tianshan, Kazakhstan and Kyrgyzstan)

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