AUTHOR=Zhang Xiawei , Li Yingjie , Wang Genhou , Wang Shuai , Kong Xingrui , Wang Xiaodong , Liu Zhibin 

TITLE=Intra-oceanic subduction in the southeastern Paleo-Asian ocean: Evidence from early Permian gabbro of the Diyanmiao ophiolite in central Inner Mongolia, North China

JOURNAL=Frontiers in Earth Science

VOLUME=10

YEAR=2023

URL=https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2022.1031842

DOI=10.3389/feart.2022.1031842

ISSN=2296-6463

ABSTRACT=<p>Investigation of intra-oceanic subduction can improve our understanding of plate tectonic processes and the history of continental growth. Evidence for intra-oceanic subduction in the Paleo-Asian Ocean has recently become an important focus of research, including the Diyanmiao ophiolite in central Inner Mongolia, North China. Here, we report a newly discovered occurrence of early Permian gabbro in the Diyanmiao ophiolite zone. The gabbro yields a weighted mean zircon U–Pb age of 294.4 ± 2.2 Ma. The gabbro samples are characterized by moderate SiO<sub>2</sub> (47.32–50.51 wt%), low TiO<sub>2</sub> (0.26–0.54 wt%) and K<sub>2</sub>O (0.04–0.75 wt%), and high Na<sub>2</sub>O (1.84–4.52 wt%) contents, high Na<sub>2</sub>O/K<sub>2</sub>O ratios (2.92–58.29), and depleted chondrite-normalized light rare Earth element patterns that are similar to N-MORB. The gabbros show slightly lower contents of high-field-strength elements (e.g., Nb, Ta, and Ti) and slightly higher contents of large-ion lithophile elements (e.g., K, Rb, Ba, and U) relative to N-MORB. In addition, the gabbros show high ε<sub>Nd</sub> (<italic>t</italic>) values (8.0–9.8) that are similar to those of forearc basalt in the Diyanmiao ophiolite and N-MORB. Integrating these new data with available results for ophiolite and arc-magmatic rocks of central Inner Mongolia, we propose that the studied gabbro was formed during the initial stage of intra-oceanic subduction and that the Paleo-Asian Ocean was still in a subduction setting during the early Permian.</p>