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Tectonic Position of the Neoproterozoic Gabbro-Ultrabasite and Gabbroid Complexes of the Bayan Nuur Block of the Songino Ledge, Central Asian Orogenic Belt.
- Source :
- Stratigraphy & Geological Correlation; Mar2019, Vol. 27 Issue 2, p159-180, 22p
- Publication Year :
- 2019
-
Abstract
- The Early Caledonian folded region of the southern framing of the Siberian platform, between the Zavkhan and Tuva-Mongolian terranes, contains blocks of the Songino ledge crystalline rocks. In the Bayan Nuur block (southern part of the Songino ledge), the Neoproterozoic (890–780 Ma) Bayan Nuur gneiss-migmatitic and Kholbo Nuur metaterrigenous-volcanogenic complexes are distinguished. The zone of their junction is traced by thrust structures, which are reflected in all structural-material complexes of the Bayan Nuur block. There are tectonic slabs in the junction zone. Their peculiarity is the presence of rocks formed before the formation of thrust gabbro-ultrabasite complex and post-thrust gabbroids and gabbro-diorites. The upper limit of the thrust formation interval is defined by Bayan Nuur pluton granitoids having the age of 790 ± 3 Ma and by gabbroids and anorthosites of Onzula tectonic plate giving the ages of 785 ± 3 and 784 ± 3 Ma. The lower limit of the thrust formation interval is determined by the age of the Bayan Nuur ultrametamorphic granitoid complex (802 ± 6 Ma). Bodies of massive (post-thrust) pegmatoid gabbros and rocks of gabbro-ultrabasite complex possessing clearly manifested thrust-associated structures are recognized in the tectonic slab of the ridge reaching the area of Mount Sant Uul. These rocks are dated at 782 ± 2 and 806 ± 10 Ma, respectively (ID-TIMS). The data indicate that the post-thrust and pre-thrust units cannot be parts of a united layered complex. In turn, pre-thrust units can be considered as paleooceanic fragments in the accretionary structure of the Bayan Nuur block, Songino ledge. [ABSTRACT FROM AUTHOR]
- Subjects :
- CRYSTALLINE rocks
PLATE tectonics
GEOCHRONOMETRY
OROGENIC belts
ANORTHOSITE
THRUST
Subjects
Details
- Language :
- English
- ISSN :
- 08695938
- Volume :
- 27
- Issue :
- 2
- Database :
- Complementary Index
- Journal :
- Stratigraphy & Geological Correlation
- Publication Type :
- Academic Journal
- Accession number :
- 136585047
- Full Text :
- https://doi.org/10.1134/S0869593819020059