Geochemical characteristics of mantle xenoliths from the Khamar Daban Ridge, south Russian Siberia
Abstract
Mantle xenoliths from basaltic lava at the Miocene Tumusun Volcano in the Khamar Daban Ridge (KDR), south Russian Siberia have been studied to characterize the subcontinenal lithospheric mantle (SCLM) beneath the Slyudyansky terrane. These xenoliths are dominantly spinel-bearing lherzolites. Equilibrium temperatures of these lherzolies range from 950 to 1100 ˚ C. The Fo contents of olivine in spinel peridotites range from 89.2 to 90.4 with Cr# in spinel ranges from 0.08 to 0.14. Although most lherzolies fall in the field of "Phanerozoic" range of the Boyd diagram, a few plot toward to the Proterozoic range. The Os isotope compositions of sulfides in these lherzolites reveal the presence of Proterozoic SCLM beneath the KDR region. Their in situ Os isotope compositions (187Os/188Os) ranges from 0.1063 (±8) to 0.1431 (±48) with the 187Re/188Os ratios of 0.004-0.862. Both TMA from the least-disturbed sulfides (187Re/188Os<0.07) and TRD from higher Re/Os sulfides without later introduction/loss of Os, yield model ages ranging from 0.7 to 3.0 Ga, with peaks around 2.0 and 1.2-1.0 Ga. These ages suggest that the SCLM beneath the KDR region formed at least by the Proterozoic time, and that some domains are Archean. The sulfide Os ages are consistent with these formation events recorded in the overlying crust. Younger sulfide Os ages (1.2-1.0 Ga) may mark the commencement of the Central Asia Orogeny since the Neoproterozoic and involvement of the mantle as suggested by Sengor et al. (1993) and Jahn (2004). This could be the first result showing ancient root beneath the KDR region, consistent with dating results of detrital zircons up to 2.9 Ga from the Slyudyansky terrane (Kovach et al., 2013). Compiling with other at least Mesoproterozoic lithospheric mantle domains revealed by Os model ages from the Vitim, Tariat and Khanka regions (Wang et al., 2011, 2013, 2014), ancient micro-continents are prevailing in the Central Asia Orogenic Belt, which might diminish extents of juvenile crustal growth in the Orogeny as expected before.
- Publication:
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EGU General Assembly Conference Abstracts
- Pub Date:
- April 2018
- Bibcode:
- 2018EGUGA..20.6006W