Clastic metasediments of the Khamar-Daban Group (Central Asian orogenic belt); chemical composition and isotope systematics
Clastic metasediments of the Khamar-Daban Group (Central Asian orogenic belt); chemical composition and isotope systematics
Russian Geology and Geophysics (October 2017) 58 (10): 1188-1198
- absolute age
- Asia
- Baikal region
- Buryat Russian Federation
- chemical composition
- clastic rocks
- Commonwealth of Independent States
- dates
- flysch
- gneisses
- granites
- igneous rocks
- isotope ratios
- isotopes
- Khamar-Daban Range
- mafic composition
- major elements
- Mesoproterozoic
- metals
- metamorphic rocks
- metasedimentary rocks
- Nd-144/Nd-143
- neodymium
- Paleoproterozoic
- plutonic rocks
- Precambrian
- Proterozoic
- protoliths
- provenance
- rare earths
- Russian Federation
- schists
- sedimentary rocks
- Sm/Nd
- stable isotopes
- tectonics
- trace elements
- ultramafics
- upper Precambrian
- Western Transbaikalia
- Central Asian orogenic belt
- Dzhida Terrane
- Kornilova Formation
- Shubutuy Formation
New data have been obtained on major- and trace-element compositions and Sm-Nd isotope systematics of clastic metasediments that belong to the Kornilova and Shubutui Formations in the Khamar-Daban terrane. The Kornilova Formation flysch derived from felsic mature crust, while the Shubutui Formation, with 4.5-7.5 wt.% MgO and higher Cr and Ni contents, had a mafic-ultramafic protolith of an island-arc setting. Isotope data indicate significant inputs of Precambrian crustal material (epsilon Nd(T) = -10 to -6.2) to the protolith of the Kornilova rocks and of high amounts of synsedimentary juvenile material to the protolith of the Shubutui Formation (epsilon Nd(T) = -2.9 to -1.5). Different model ages (1.7-2.0 and 1.3-1.4 Ga, respectively), compositions, and provenances of the Kornilova and Shubutui rocks, as well as a prolonged deposition gap (>100 Myr), evidence that the two formations were deposited in different basins and tectonic settings. The rock compositions and Nd isotope signatures suggest an island arc setting for the Shubutui deposition in the Dzhida terrane and a continental-margin setting for the deposition of the Kornilova Formation, which is the uppermost stratum of the Khamar-Daban terrane.