TY - JOUR
KW - Chinese Altai
KW - orthogonal compression
KW - pegmatite dyke
KW - Permian collision
KW - Petrochronology
KW - Structural synthesis
AU - Yingde Jiang
AU - Karel Schulmann
AU - Min Sun
AU - Roberto Weinberg
AU - Pavla Štípská
AU - P. Li
AU - J. Zhang
AU - Francis Chopin
AU - S. Wang
AU - X. Xia
AU - Wenjiao Xiao
AB - Abstract Kinematic significance and time scales of geodynamic processes forming the Altai Orogenic Belt are addressed through structural and petrological analysis combined with zircon and monazite geochronology. The study area is composed of orogenic lower crust represented by a Devonian migmatite-magmatite complex and orogenic middle and upper crust formed by an amphibolite-facies Ordovician sedimentary sequence and a weakly to unmetamorphosed Devonian volcano-sedimentary cover, respectively. The orogenic lower and middle crust were first affected by moderate thickening, which formed subhorizontal Barrovian metamorphic schistosity. This fabric was reworked by deep crustal melting and intrusion of granite sheets during horizontal extension at 400–380 Ma. Soon after, this horizontal fabric was affected by NW-SE shortening generating crustal-scale upright folding associated with subvertical flow of still partially molten orogenic lower crust. During this event, the orogenic lower and middle crust were tightly juxtaposed with upper crustal sedimentary rocks. The last event was related with a NE-SW oriented convergence resulting in large-scale folding and megafold interference pattern in the Permian at 280–273 Ma. Combined with existing regional data, our results allow proposing a Devonian tectonic switching from compression to extension and back to compression, as a response to variations of subduction dynamics between slab advance and retreat in a Pacific-type suprasubduction system. The Permian folding was associated with the progressive northward exhumation of thermally softened crust. This tectonic evolution is in response to the indentation of the rigid Junggar arc domain into the weak Altai wedge.
BT - Tectonics
DO - 10.1029/2018TC005231
N2 - Abstract Kinematic significance and time scales of geodynamic processes forming the Altai Orogenic Belt are addressed through structural and petrological analysis combined with zircon and monazite geochronology. The study area is composed of orogenic lower crust represented by a Devonian migmatite-magmatite complex and orogenic middle and upper crust formed by an amphibolite-facies Ordovician sedimentary sequence and a weakly to unmetamorphosed Devonian volcano-sedimentary cover, respectively. The orogenic lower and middle crust were first affected by moderate thickening, which formed subhorizontal Barrovian metamorphic schistosity. This fabric was reworked by deep crustal melting and intrusion of granite sheets during horizontal extension at 400–380 Ma. Soon after, this horizontal fabric was affected by NW-SE shortening generating crustal-scale upright folding associated with subvertical flow of still partially molten orogenic lower crust. During this event, the orogenic lower and middle crust were tightly juxtaposed with upper crustal sedimentary rocks. The last event was related with a NE-SW oriented convergence resulting in large-scale folding and megafold interference pattern in the Permian at 280–273 Ma. Combined with existing regional data, our results allow proposing a Devonian tectonic switching from compression to extension and back to compression, as a response to variations of subduction dynamics between slab advance and retreat in a Pacific-type suprasubduction system. The Permian folding was associated with the progressive northward exhumation of thermally softened crust. This tectonic evolution is in response to the indentation of the rigid Junggar arc domain into the weak Altai wedge.
PY - 2019
SP - 253
EP - 280
T2 - Tectonics
TI - Structural and Geochronological Constraints on Devonian Suprasubduction Tectonic Switching and Permian Collisional Dynamics in the Chinese Altai, Central Asia
UR - https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018TC005231
VL - 38
ER -