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Are the Chinese Altai 'terranes' the result of juxtaposition of different crustal levels during Late Devonian and Permian orogenesis?
- Source :
- Gondwana Research, Gondwana Research, Elsevier, 2019, 66, pp.183-206. ⟨10.1016/j.gr.2018.11.003⟩, Dipòsit Digital de la UB, Universidad de Barcelona
- Publication Year :
- 2019
- Publisher :
- HAL CCSD, 2019.
-
Abstract
- The general structure of the Chinese Altai has been traditionally regarded as being formed by five tectono-stratigraphic ‘terranes’ bounded by large-scale faults. However, numerous detrital zircon studies of the Paleozoic volcano-sedimentary sequences shown that the variably metamorphosed Cambro-Ordovician sequence, known as the Habahe Group, is present at least in four ‘terranes’. It structurally represents deepest rocks unconformably covered by Devonian and Carboniferous sedimentary and volcanic rocks. Calc-alkaline, mostly Devonian, granitoids that intruded all the terranes revealed their syn-subduction related setting. Geochemistry and isotope features of the syn-subduction granitoids have shown that they originated mainly from the melting of youthful sediments derived from an eroded Ordovician arc further north. In contrast, Permian alkaline granitoids, mostly located in the southern part of the Chinese Altai, reflect a post-subduction intraplate setting. The metamorphic evolution of the metasedimentary sequences shows an early MP-MT Barrovian event, followed by two Buchan events: LP-HT mid-Devonian (ca. 400–380 Ma) and UHT-HT Permian (ca. 300–270 Ma) cycles. The Barrovian metamorphism is linked to the formation of a regional sub-horizontal possibly Early Devonian fabric and the burial of the Cambro-Ordovician sequence. The Middle Devonian Buchan type event is related to intrusions of the syn-subduction granitoids during an extensional setting and followed by Late Devonian-Early Carboniferous NE-SW trending upright folding and crustal scale doming during a general NW-SE shortening, responsible for the exhumation of the hot lower crust. The last Permian deformation formed NW-SE trending upright folds and vertical zones of deformation related to the extrusion of migmatites, anatectic granitoids and granulite rocks, and to the intrusions of gabbros and granites along the southern border of the Chinese Altai. Finally, the Permo-Triassic cooling and thrust systems affected the whole mountain range from ca. 265 to 230 Ma. In conclusion, the Chinese Altai represents different crustal levels of the lower, middle and upper orogenic crust of a single Cambro-Ordovician accretionary wedge, heterogeneously affected by the Devonian polyphase metamorphism and deformation followed by the Permian tectono-thermal reworking event related to the collision with the Junggar arc. It is the interference of Devonian and Permian upright folding events that formed vertical boundaries surrounding the variously exhumed and eroded crustal segments. Consequently, these crustal segments should not be regarded as individual suspect terranes.
- Subjects :
- China
Accretionary wedge
010504 meteorology & atmospheric sciences
Permian
Paleozoic
Geochemistry
Metamorphism
Geologia estructural
010502 geochemistry & geophysics
01 natural sciences
Devonian
Carboniferous
Late Devonian extinction
ComputingMilieux_MISCELLANEOUS
0105 earth and related environmental sciences
Terrane
[SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics
Structural geology
Geology
15. Life on land
Orogènesi
Xina
Geoquímica
Orogeny
Subjects
Details
- Language :
- English
- ISSN :
- 1342937X
- Database :
- OpenAIRE
- Journal :
- Gondwana Research, Gondwana Research, Elsevier, 2019, 66, pp.183-206. ⟨10.1016/j.gr.2018.11.003⟩, Dipòsit Digital de la UB, Universidad de Barcelona
- Accession number :
- edsair.doi.dedup.....88c9548e70a2dfbbf59ee0a699f6169f