TY - JOUR
T1 - Seismological evidence for a remnant oceanic slab in the western Junggar, northwest China
AU - Wu, Shucheng
AU - Huang, Rong
AU - Xu, Yixian
AU - Yang, Yingjie
AU - Jiang, Xiaohuan
AU - Zhu, Lupei
PY - 2018/5
Y1 - 2018/5
N2 - The western Junggar is situated in the southwestern Central Asian Orogenic Belt, and its origin is believed to be related to either intracontinental arc or intraoceanic arc-related subduction system. However, the mode of subduction is still contentious. In this study, we build a high-resolution 3-D model of the crust of the western Junggar to constrain the subduction mode. By deploying a seismic array consisting of 31 portable broadband seismic stations from September 2013 to December 2013, we determine the Moho depth beneath every station using a H-κ method and the Moho variations along three NW-SE profiles using a common conversion point stacking method. We also construct a 3-D crustal S wave velocity model using ambient noise tomography. Our results reveal significant variations of Moho depths across the study region and a pronounced Moho offset between the Zaire mountains and the western Junggar basin. Ambient noise tomography shows that a high shear velocity layer (>3.9 km/s) is observed in the middle/lower crust of the western Junggar Basin, which is overlaid by a low velocity upper crust. The high-velocity body gradually dips northwestward with depth beneath the Zaire mountains. The speed of this high-velocity body is consistent with the calculated S wave speed of various metamorphic facies of mid-ocean ridge basalt under the P/T conditions of middle/lower crust in the western Junggar. Our seismic observations support a northwest paleosubduction model for the evolution of the western Junggar, in which a remnant oceanic slab is still trapped in the western Junggar.
AB - The western Junggar is situated in the southwestern Central Asian Orogenic Belt, and its origin is believed to be related to either intracontinental arc or intraoceanic arc-related subduction system. However, the mode of subduction is still contentious. In this study, we build a high-resolution 3-D model of the crust of the western Junggar to constrain the subduction mode. By deploying a seismic array consisting of 31 portable broadband seismic stations from September 2013 to December 2013, we determine the Moho depth beneath every station using a H-κ method and the Moho variations along three NW-SE profiles using a common conversion point stacking method. We also construct a 3-D crustal S wave velocity model using ambient noise tomography. Our results reveal significant variations of Moho depths across the study region and a pronounced Moho offset between the Zaire mountains and the western Junggar basin. Ambient noise tomography shows that a high shear velocity layer (>3.9 km/s) is observed in the middle/lower crust of the western Junggar Basin, which is overlaid by a low velocity upper crust. The high-velocity body gradually dips northwestward with depth beneath the Zaire mountains. The speed of this high-velocity body is consistent with the calculated S wave speed of various metamorphic facies of mid-ocean ridge basalt under the P/T conditions of middle/lower crust in the western Junggar. Our seismic observations support a northwest paleosubduction model for the evolution of the western Junggar, in which a remnant oceanic slab is still trapped in the western Junggar.
UR - http://www.scopus.com/inward/record.url?scp=85048769215&partnerID=8YFLogxK
UR - http://purl.org/au-research/grants/arc/FT130101220
U2 - 10.1029/2017JB015332
DO - 10.1029/2017JB015332
M3 - Article
AN - SCOPUS:85048769215
SN - 2169-9356
VL - 123
SP - 4157
EP - 4170
JO - Journal of Geophysical Research: Solid Earth
JF - Journal of Geophysical Research: Solid Earth
IS - 5
ER -