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- Title
Circum‐Cratonic Triassic Syenite Province of North China Craton Reveals Heterogeneous Lithospheric Mantle Related to Dual Subduction.
- Authors
Liu, Xu; Peng, Peng; Mitchell, Ross N.; Wang, Chong; Kang, Jianli
- Abstract
Subduction‐induced metasomatism may increase heterogeneity in the subcontinental lithospheric mantle (SCLM) over time. Syenite and its relevant varieties are typically derived from the most metasomatized portions of the SCLM and thus provide a key to decipher its heterogeneity. The only circum‐cratonic syenite province in the world, the Late Triassic belt around North China craton, is unique and offers an opportunity to investigate heterogeneity of the SCLM right before its destruction in the Mesozoic. New and previous data of whole‐rock Sr‐Nd and zircon in situ Hf‐O isotopes of syenite intrusions encircling the craton indicate two distinct types of metasomatism characterized by an alteration of juvenile or ancient materials. The spatiotemporally distinct sources can be discriminated by melts from oceanic slabs subducting beneath much of North China followed by deep subduction of South China craton only in the south. This unique setting of a circum‐cratonic syenite belt proves in a single case study that subduction‐induced metasomatism may cause craton‐scale SCLM heterogeneity. Plain Language Summary: The subcontinental lithospheric mantle (SCLM), comprising the roots of cratons, is depleted, rigid, and buoyant, all of which contribute to maintaining the stability of a craton. However, the SCLM can be replenished and destroyed by melts from recycled subducting slabs, known as mantle metasomatism. SCLM heterogeneity can be caused by metasomatism by carbonate and silicate melts derived from subducted oceanic and continental plates. It can then be recorded by mantle xenoliths or mantle‐derived rocks, but such records are typically either highly localized or asynchronous with other such records. In this study, Triassic syenites of North China craton that are distributed craton‐wide and coeval provide a chance to investigate SCLM heterogeneity through whole‐rock Sr‐Nd isotopes and zircon in situ Hf‐O isotopes. We propose that the contrasting subduction systems related to the Paleo‐Asian and Paleo‐Qinling oceanic plates subducting on the northern and southern margins of North China craton, respectively, as well as the deep continental subduction of South China craton to the southeast of North China, gave rise to the observed SCLM heterogeneity during the Permo–Triassic, which provided a preconditioning for the later Mesozoic lithospheric destruction of the cratonic root. Key Points: A unique circum‐cratonic Triassic syenite belt from North China craton (NCC) reveals heterogeneity of the subcontinental lithospheric mantleDifferential subduction systems surrounding NCC during the Permo–Triassic caused the heterogeneity through mantle metasomatismEarly Mesozoic mantle metasomatism served as a preconditioning for lithospheric destruction of NCC before the effect of the Pacific Ocean
- Subjects
CHINA; SYENITE; METASOMATISM; SUBDUCTION; CRATONS; INCLUSIONS in igneous rocks; MESOZOIC Era; HETEROGENEITY
- Publication
Journal of Geophysical Research. Solid Earth, 2023, Vol 128, Issue 11, p1
- ISSN
2169-9313
- Publication type
Article
- DOI
10.1029/2023JB027084