Cambrian-Ordovician mid-ocean ridge magmatism in the Kyrgyz Middle Tianshan and origin of the Karaterek ophiolite

Hegner, E.; Alexeiev, D. V.; Messling, N.; Tolmacheva, T. Yu und Willbold, M. (2022): Cambrian-Ordovician mid-ocean ridge magmatism in the Kyrgyz Middle Tianshan and origin of the Karaterek ophiolite. In: Lithos, Bd. 410, 106576

Abstract

The Karaterek ophiolite represents a remnant of a previously unknown early Paleozoic ocean basin in the Kyrgyz Middle Tianshan (MTS) and sheds new light on the accretionary history of the western Central Asian Orogenic Belt (CAOB). Late Cambrian (similar to 495-485 Ma, this study) and Middle Ordovician (similar to 470-460 Ma) conodont ages support more than 30 Ma of seafloor spreading. The ophiolite comprises predominantly LREE-depleted midocean ridge basalts (N-MORB) with chemically evolved compositions (Mg# 57-45). La-Th-Nb systematics and Ti/Zr and Ti/V ratios corroborate MORB sources. Al2O3 and FeO variations support plagioclase-controlled and tholeiitic magma fractionation processes, respectively. Initial epsilon(Nd) (i) values of +6 to +8 overlap the range of the contemporaneous global sub-ridge mantle. A section of OIB and N-MORB pillows is interpreted as near-ridge seamount tapping small-scale little (epsilon(Nd) (i) + 1) and highly depleted (epsilon(Nd )(i) + 8) mantle, respectively. Coinciding MORB and arc-features in subordinate basaltic dike samples suggest melting of hydrous residual peridotite (epsilon(Nd (i)) similar to 9) during subduction initiation. We propose a geodynamic model of rifting of the MTS prior to the late Cambrian (similar to 490 Ma), open-ocean seafloor spreading during the late Cambrian to Middle Ordovician, and basin closure and plate collision in the Late Ordovician at similar to 450 Ma.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Geowissenschaften > Department für Geo- und Umweltwissenschaften
• Themengebiete: 500 Naturwissenschaften und Mathematik > 550 Geowissenschaften, Geologie
• ISSN: 0024-4937
• Sprache: Englisch