Geodynamic evolution of the western Tien Shan, Uzbekistan: insights from U-Pb SHRIMP geochronology and Sr-Nd-Pb-Hf isotope mapping of granitoids

A. Dolgopolova, R. Seltmann*, D. Konopelko, Yu S. Biske, V. Shatov, R. Armstrong, E. Belousova, R. Pankhurst, R. Koneev, F. Divaev

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

44 Citations (Scopus)

Abstract

Sr-Nd-Pb-Hf isotope mapping combined with U-Pb zircon SHRIMP ages of granitoids from four sampling profiles across terrane boundaries in Uzbekistan reveal distinct reservoir types (cratonic and accretionary), witnessed by the diverse nature and origin of the predominant Paleozoic granitic magmatism that provided hosts for major ore-bodies. The study region comprises four major terranes, including 1) the Sultan-Uvais terrane, 2) the Kyzylkum-Nurata Segment and 3) the Gissar Segment of the South Tien Shan and 4) the Chatkal-Kurama terrane of the Middle Tien Shan. Sr-Nd isotope analyses show a wide range of εNdt (-5 to +7) and (87Sr/86Sr)t of 0.704-0.707, indicating involvement of both mantle-derived material and older crustal sources. A wide range of Hf-isotope compositions found in zircons of Chatkal-Kurama granites, Middle Tien Shan (εHf mainly~-5 to +5), could be due to recycling of older crustal protolith(s); in particular, the earliest (Silurian) granites may be directly derived from 1.5 to 1.7Ga lower crust. In the Southern Tien Shan, some involvement of subducted oceanic crust is evidenced by strongly juvenile εHft values of up to +14 and +16 (Sultan-Uvais, Teskuduk-Kyzylkum). Permo-Carboniferous granitoids, which occur across all terranes also exhibit a wide range of isotope signatures, corresponding to Mesoproterozoic-Neoproterozoic crustal protoliths with a westward increase in juvenile contributions. Pb isotopes (whole-rock) imply the dominance of a crustal component and crust-mantle mixing processes. New age data confirmed: 1) old age of the Turkestan Ocean (505Ma in Sultan-Uvais), 2) fragments of Silurian island arcs in the accretionary complex of the Chatkal-Kurama terrane (granites of 429-416Ma) and in the upper allochthon of the South Tien Shan (gabbro 438Ma in Tamdytau), and 3) a significant volume of granitoid magmatism of subduction or early-collisional stages (around 320-310Ma) in the Chatkal-Kurama Segment and especially in the Gissar Segment. The westernmost part of the Tien Shan is characterized by multiple subduction processes responsible for 300millionyears of geodynamic evolution history (accretionary collage, crustal growth) with the pre-Mesozoic crust formation concluded by Permian post-collisional extensional magmatism.

Original languageEnglish
Pages (from-to)76-109
Number of pages34
JournalGondwana Research
Volume47
Early online date10 Dec 2016
DOIs
Publication statusPublished - Jul 2017

Keywords

  • Tien Shan
  • Uzbekistan
  • Sr-Nd-Pb-Hf isotopes
  • SHRIMP zircon ages
  • Tectonic model

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