We investigated the relationships among slab geometry, obliquity, and the thermal regime associated with the subduction of oceanic plates using a three-dimensional （3D） parallelepiped thermal convection model. Vario...We investigated the relationships among slab geometry, obliquity, and the thermal regime associated with the subduction of oceanic plates using a three-dimensional （3D） parallelepiped thermal convection model. Various models with convex and concave slab shapes were constructed in the numerical simu- lation, and the temperature and mantle flow distributions were calculated. The results revealed that when the slab dip angle increases, or the obliquity of subduction becomes steeper, the interplate tem- perature decreases remarkably. Cooler （warmer） zones on the plate interface were identified from the modeling where there was a larger （smaller） subduction angle. Consequently, the interplate temperature distribution is partly controlled by the true subduction angle （TSA）, which is a function of the slab dip angle and the obliquity of subduction. The rate of change of the interface temperature for the TSA was 10-50 ℃ （10°〈 TSA 〈 20°） at depths ranging from （TSA 10） × 5 km to 60 ＋ （TSA 10） × 5 km for a fiat slab after a subduction history of 7 Myrs. The along-arc slab curvature affects the variation in TSA. The slab radius also appeared to influence the radius of induced mantle flow.展开更多
The intracontinental subduction of a>200-km-long section of the Tajik-Tarim lithosphere beneath the Pamir Mountains is proposed to explain nearly 30 km of shortening in the Tajik fold-thrust belt and the Pamir upli...The intracontinental subduction of a>200-km-long section of the Tajik-Tarim lithosphere beneath the Pamir Mountains is proposed to explain nearly 30 km of shortening in the Tajik fold-thrust belt and the Pamir uplift.Seismic imaging revealed that the upper slab was scraped and that the lower slab had subducted to a depth of>150 km.These features constitute the tectonic complexity of the Pamirs,as well as the thermal subduction mechanism involved,which remains poorly understood.Hence,in this study,high-resolution three-dimensional(3D)kinematic modeling is applied to investigate the thermal structure and geometry of the subducting slab beneath the Pamirs.The modeled slab configuration reveals distinct along-strike variations,with a steeply dipping slab beneath the southern Pamirs,a more gently inclined slab beneath the northern Pamirs,and apparent upper slab termination at shallow depths beneath the Pamirs.The thermal field reveals a cold slab core after delamination,with temperatures ranging from 400℃to 800℃,enveloped by a hotter mantle reaching~1400℃.The occurrence of intermediate-depth earthquakes aligns primarily with colder slab regions,particularly near the slab tear-off below the southwestern Pamirs,indicating a strong correlation between slab temperature and seismicity.In contrast,the northern Pamirs exhibit reduced seismicity at depth,which is likely associated with thermal weakening and delamination.The central Pamirs show a significant thermal anomaly caused by a concave slab,where the coldest crust does not descend deeply,further suggesting crustal detachment or mechanical failure.The lateral asymmetry in slab temperature possibly explains the mechanism of lateral tearing and differential slab-mantle coupling.展开更多
文摘We investigated the relationships among slab geometry, obliquity, and the thermal regime associated with the subduction of oceanic plates using a three-dimensional （3D） parallelepiped thermal convection model. Various models with convex and concave slab shapes were constructed in the numerical simu- lation, and the temperature and mantle flow distributions were calculated. The results revealed that when the slab dip angle increases, or the obliquity of subduction becomes steeper, the interplate tem- perature decreases remarkably. Cooler （warmer） zones on the plate interface were identified from the modeling where there was a larger （smaller） subduction angle. Consequently, the interplate temperature distribution is partly controlled by the true subduction angle （TSA）, which is a function of the slab dip angle and the obliquity of subduction. The rate of change of the interface temperature for the TSA was 10-50 ℃ （10°〈 TSA 〈 20°） at depths ranging from （TSA 10） × 5 km to 60 ＋ （TSA 10） × 5 km for a fiat slab after a subduction history of 7 Myrs. The along-arc slab curvature affects the variation in TSA. The slab radius also appeared to influence the radius of induced mantle flow.
基金the Chinese Academy of Sciences Pioneer Hundred Talents Program and the Second Tibetan Plateau Scientific Expedition and Research Program(Grant No.2019QZKK0708)supported by a MEXT(Ministry of Education,Culture,Sports,Science and Technology)KAKENHI(Grants-in-Aid for Scientific Research)grant(Grant No.21H05203)Kobe University Strategic International Collaborative Research Grant(Type B Fostering Joint Research).
文摘The intracontinental subduction of a>200-km-long section of the Tajik-Tarim lithosphere beneath the Pamir Mountains is proposed to explain nearly 30 km of shortening in the Tajik fold-thrust belt and the Pamir uplift.Seismic imaging revealed that the upper slab was scraped and that the lower slab had subducted to a depth of>150 km.These features constitute the tectonic complexity of the Pamirs,as well as the thermal subduction mechanism involved,which remains poorly understood.Hence,in this study,high-resolution three-dimensional(3D)kinematic modeling is applied to investigate the thermal structure and geometry of the subducting slab beneath the Pamirs.The modeled slab configuration reveals distinct along-strike variations,with a steeply dipping slab beneath the southern Pamirs,a more gently inclined slab beneath the northern Pamirs,and apparent upper slab termination at shallow depths beneath the Pamirs.The thermal field reveals a cold slab core after delamination,with temperatures ranging from 400℃to 800℃,enveloped by a hotter mantle reaching~1400℃.The occurrence of intermediate-depth earthquakes aligns primarily with colder slab regions,particularly near the slab tear-off below the southwestern Pamirs,indicating a strong correlation between slab temperature and seismicity.In contrast,the northern Pamirs exhibit reduced seismicity at depth,which is likely associated with thermal weakening and delamination.The central Pamirs show a significant thermal anomaly caused by a concave slab,where the coldest crust does not descend deeply,further suggesting crustal detachment or mechanical failure.The lateral asymmetry in slab temperature possibly explains the mechanism of lateral tearing and differential slab-mantle coupling.
