Buchan type metamorphism in the Pingtan-Dongshan metamorphic belt, SE China: Evidence from combined EMP monazite and U-Pb zircon ages of mica schists. (15th September 2021)

• Record Type: Journal Article
• Authors: Lin, Jian-Wei; Lee, Chi-Yu; Chen, Cheng-Hong; Kato, Takenori; Sano, Yuji; Naoto, Takahata
• Is Part Of: Journal of Asian earth sciences. Volume 218(2021)
• Publication Date: 2021-09-15
• Subjects: U-Pb zircon age -- EMP monazite age -- Mica schist -- Pingtan-Dongshan Metamorphic Belt -- Cathaysia block; Earth sciences -- Asia -- Periodicals; Sciences de la terre -- Asie -- Périodiques; Earth sciences; Asia; Periodicals; 555.05
• DOI: 10.1016/j.jseaes.2021.104891
• Languages: English
• ISSNs: 1367-9120

Abstract

Graphical abstract: Highlights: New ages of mica schist in PDMB are obtained via monazite and zircon inclusions. Unusual zircon ages (~1.8 Ga and ~190 Ma) need exotic source other than Cathaysia. Monazites included in sillimanite constrain a HT/LP metamorphism at ~100 Ma. The youngest age population of zircon inclusions supports the monazite age results. A regional post-orogenic magmatism made up the Buchan type metamorphism of PDMB. Abstract: Detailed age information of the Pingtan-Dongshan Metamorphic Belt in the coastal Cathaysia Block is important in understanding geodynamics of the Late Mesozoic South China continental margin. Geochronological determinations on monazite and zircon inclusions and zircon separates from five mica schists and two granites intruding schists are used to constrain the timing of metamorphism and sediment sources. Common ages of monazite and zircon inclusions within major constituents (quartz, muscovite, sillimanite and K-feldspar) in schists define a high temperature/low pressure metamorphic event at ~100 Ma. Along with zircon ages of granites (106 and 101 Ma), a Buchan type metamorphism is proposed regarding a heat source from the post-orogenic magmatism in the neighboring igneous province. Based on the age distribution patterns of discrete zircons, two groups of schist are distinguished by sources of sediments prior to metamorphism. One group has a simple age cluster (145–130 Ma) inferring proximal magmatic rocks in the Cathaysia Block. The other group shows a widespread age spectrum with two particular populations of ~1.8 Ga and ~190 Ma that are uncommon in the Cathaysia Block but comparable to schists in the Tailuko Metamorphic Belt of eastern Taiwan. This may suggest a general source between these two belts in which a now-concealed microcontinent would play a role. Such a new tectonic framework can account for the two provenances of sediments in schists of this belt, and its structural configuration is influenced by a high temperature regime caused by mantle upwelling as a reflection of slab rollback of the subducted Paleo-Pacific Plate during 110–90 Ma.