Middle Paleozoic mafic magmatism and ocean plate stratigraphy of the South Tianshan, Kyrgyzstan

I. Safonova, G. Biske, R. L. Romer, R. Seltmann, V. Simonov, S. Maruyama

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Abstract

The tectonic history of the Kyrgyz South Tianshan in the western Central Asian Orogenic Belt (CAOB) remains controversial, first of all, due to the limited amount of geochemical and isotope data. Our paper presents the first results of a detailed geochemical study (major and trace elements, Sr, Nd and Pb isotopes) of Middle Paleozoic mafic volcanic and subvolcanic rocks of the Ferghana and Atbashi-Kokshaal accretionary belts of the South Tianshan orogen in Kyrgyzstan, which formed during the evolution of the Turkestan Ocean. A special focus is given to the relation between magmatic rocks and sedimentary units of marine origin, chert, siliceous shale/mudstone, volcanogenic-carbonate clastics, seamount carbonates, and turbidites, which we consider as elements of Ocean Plate Stratigraphy (OPS). The age range of marine sediments is Late Silurian to Early Carboniferous, but the age of the most volcanic rocks associated with fossil-bearing OPS sediments is Devonian. The magmatic rocks have geochemical affinity to oceanic island basalts (OIB-type) and, to a lesser extent, mid-oceanic ridge (MORB-type) basalts associated with hemipelagic siliceous mudstone and pelagic chert. The rocks with OIB-type affinity are associated with chert, siliceous shale and carbonaceous clastics and carbonates. They are enriched in TiO2, LREE (La/Smn = 1.9), and Nb (Zr/Nbav. = 10), have differentiated HREE (Gd/Ybn = 2.0), medium to low εNd (~5.7) and are characterized by clear Nb positive anomalies in normalized multi-element plots (Nb/Thpm = 1.3, Nb/Lapm = 1.1). The OIBs formed by relatively low degrees of melting (

Original languageEnglish
Pages (from-to)236-256
Number of pages21
JournalGondwana Research
Volume30
DOIs
Publication statusPublished - Feb 1 2016
Externally publishedYes

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Keywords

  • Central Asian Orogenic Belt
  • Ferghana-Atbashi-Kokshaal
  • Geochemistry
  • Petrogenesis
  • Sr-Nd-Pb isotopes
  • Turkestan Ocean

ASJC Scopus subject areas

  • Geology

Cite this

Safonova, I., Biske, G., Romer, R. L., Seltmann, R., Simonov, V., & Maruyama, S. (2016). Middle Paleozoic mafic magmatism and ocean plate stratigraphy of the South Tianshan, Kyrgyzstan. Gondwana Research, 30, 236-256. https://doi.org/10.1016/j.gr.2015.03.006