TY - JOUR

T1 - Late Mesozoic rifting and its deep dynamic mechanisms in the central Sulu orogenic belt

T2 - Records from Lingshan Island

AU - Zhou, Tengfei

AU - Zhou, Yaoqi

AU - Søager, Nina

AU - Holm, Paul Martin

AU - Zhang, Zhenkai

AU - Wang, Jun

AU - Liang, Zhao

AU - Mu, Hongyu

AU - Cheng, Yanjun

AU - Liu, Feifei

AU - Wang, Miao

AU - Zhang, Yue

AU - Zhang, Hui

AU - Gu, Yangjian

AU - Dong, Shihui

AU - Zhao, Hanjie

AU - Li, Manjie

AU - Chen, Yang

AU - Liu, Yanzi

PY - 2022

Y1 - 2022

N2 - The Lingshan Island scientific drill confirms that two episodes (Laiyang period and Qingshan period) of rifting developed in the central Sulu orogenic belt (SOB) in Late Mesozoic. With a set of methods including fieldwork, drilling, core logging, zircon U-Pb dating and whole rock geochemistry applied, the age, the depositional sequence and the deep dynamic mechanisms of rift evolution were unraveled. The stratigraphic sequence of the Laiyang-Qingshan Groups on Lingshan Island was composed of two different rifting sequences: (1) Laiyang Group (147-125 Ma), which consists of deep-water gravity flow deposits with interlayers of intermediate volcanic rocks; and (2) Lower Qingshan Group (125-119 Ma), which unconformably overlies the former sequence and contains subaerial volcanic deposits and terrestrial deposits. The tectonic environment changed during the evolution of these two episodes of rifting: the rift was in a NNW-SSE extensional environment in the Laiyang period and showed the typical passive rifting character that "lithospheric extension and rifting preceded volcanism". The passive rifting period was ended by a short WNW-ESE compression at about 125 Ma. After that, the tectonic environment transferred to a strong NW-SE extensional environment and the rifting evolved into a volcanic arc basin in the Qingshan period. The igneous rocks are shoshonitic to high-K calc-alkaline trachyandesites to trachytes with a few intercalated lamprophyres and a rhyolite. The geochemical characteristics of the igneous rocks indicate that they are mantle-derived melts with a metasomatized mantle source and/or crustal contamination. In addition, an increased thinning of the lithosphere happened during the rifting episodes. The low-angle subduction of the Paleo-Pacific plate in the Jurassic weakened the thickened SOB lithospheric mantle. The rollback of the subducting plate started in late Jurassic to early Cretaceous, and the SOB lithospheric mantle was delaminated synchronously because of the gravity collapse. Thus, this caused passive rifting in the Laiyang period. Thereafter, the rollback and trench retreat of the high-angle subducting Paleo-Pacific plate would have achieved its climax, resulting in the strong regional extension. Passive rifting was ended by the crustal uplift caused by asthenospheric upwelling beneath the rift. The lower crust was heated by the upwelling asthenosphere and partially melted to form felsic melts, which were emplaced upwards and erupted explosively. The rift evolved into a volcanic arc basin in the Qingshan period and showed some characteristics of active rifting. Above all, a passive rifting in the Laiyang period and a volcanic arc basin in the Qingshan period developed successively in the Lingshan Island area (the central SOB). This records the transfer of the study area from the Paleo-Tethys tectonic domain to the circum-Pacific tectonic domain. The delamination of SOB lithospheric mantle and the upwelling of asthenospheric material were the deep dynamic mechanisms driving the development and evolution of two rift episodes. Additionally, the rift development was controlled remotely by the subduction of the Paleo-Pacific plate.

AB - The Lingshan Island scientific drill confirms that two episodes (Laiyang period and Qingshan period) of rifting developed in the central Sulu orogenic belt (SOB) in Late Mesozoic. With a set of methods including fieldwork, drilling, core logging, zircon U-Pb dating and whole rock geochemistry applied, the age, the depositional sequence and the deep dynamic mechanisms of rift evolution were unraveled. The stratigraphic sequence of the Laiyang-Qingshan Groups on Lingshan Island was composed of two different rifting sequences: (1) Laiyang Group (147-125 Ma), which consists of deep-water gravity flow deposits with interlayers of intermediate volcanic rocks; and (2) Lower Qingshan Group (125-119 Ma), which unconformably overlies the former sequence and contains subaerial volcanic deposits and terrestrial deposits. The tectonic environment changed during the evolution of these two episodes of rifting: the rift was in a NNW-SSE extensional environment in the Laiyang period and showed the typical passive rifting character that "lithospheric extension and rifting preceded volcanism". The passive rifting period was ended by a short WNW-ESE compression at about 125 Ma. After that, the tectonic environment transferred to a strong NW-SE extensional environment and the rifting evolved into a volcanic arc basin in the Qingshan period. The igneous rocks are shoshonitic to high-K calc-alkaline trachyandesites to trachytes with a few intercalated lamprophyres and a rhyolite. The geochemical characteristics of the igneous rocks indicate that they are mantle-derived melts with a metasomatized mantle source and/or crustal contamination. In addition, an increased thinning of the lithosphere happened during the rifting episodes. The low-angle subduction of the Paleo-Pacific plate in the Jurassic weakened the thickened SOB lithospheric mantle. The rollback of the subducting plate started in late Jurassic to early Cretaceous, and the SOB lithospheric mantle was delaminated synchronously because of the gravity collapse. Thus, this caused passive rifting in the Laiyang period. Thereafter, the rollback and trench retreat of the high-angle subducting Paleo-Pacific plate would have achieved its climax, resulting in the strong regional extension. Passive rifting was ended by the crustal uplift caused by asthenospheric upwelling beneath the rift. The lower crust was heated by the upwelling asthenosphere and partially melted to form felsic melts, which were emplaced upwards and erupted explosively. The rift evolved into a volcanic arc basin in the Qingshan period and showed some characteristics of active rifting. Above all, a passive rifting in the Laiyang period and a volcanic arc basin in the Qingshan period developed successively in the Lingshan Island area (the central SOB). This records the transfer of the study area from the Paleo-Tethys tectonic domain to the circum-Pacific tectonic domain. The delamination of SOB lithospheric mantle and the upwelling of asthenospheric material were the deep dynamic mechanisms driving the development and evolution of two rift episodes. Additionally, the rift development was controlled remotely by the subduction of the Paleo-Pacific plate.

KW - Sulu orogenic belt

KW - Lingshan Island

KW - Late Mesozoic

KW - Rifting

KW - Slab subduction

KW - Basin dynamics

KW - SEDIMENT DEFORMATION STRUCTURES

KW - EASTERN NORTH CHINA

KW - SUBDUCTED CONTINENTAL-CRUST

KW - U-PB AGE

KW - SHANDONG PROVINCE

KW - TECTONIC EVOLUTION

KW - JIAODONG PENINSULA

KW - JIAOLAI BASIN

KW - GEOCHEMICAL CONSTRAINTS

KW - ISOTOPIC CONSTRAINTS

U2 - 10.1007/s11430-021-9925-y

DO - 10.1007/s11430-021-9925-y

M3 - Journal article

VL - 65

SP - 1751

EP - 1771

JO - Science in China, Series D: Earth Sciences

JF - Science in China, Series D: Earth Sciences

SN - 1674-7313

IS - 9

ER -