Discovery and Significance of the Neoproterozoic Gabbro Intrusion in the Bayan Obo Group Along the Northern Margin of the North China Craton

This is the authors' abstract. We don't add key points for this paper.

The tectonic position of the North China Craton within the Rodinia supercontinent remain unclear due to the scarcity of early Neoproterozoic magmatic rocks in the region, resulting in limited paleomagnetic data. In this study, we report the discovery of a Neoproterozoic metamorphic gabbro intrusion within the Bayan Obo Group, located in the northwestern Bayan Obo rift zone at the northern margin of the North China Craton. This finding offers crucial geological insights into addressing this key scientific question. We utilised petrography, whole‐rock geochemistry, zircon U–Pb geochronology, and Sr‐Nd isotopic analysis to investigate the genesis and source of the gabbroic rock and its tectonic setting. The metamorphosed gabbro has a zircon 206Pb/238U weighted mean age of 925.9 ± 7.2 Ma, with low SiO2 (46.46%–48.28%), high Na2O (2.95%–3.56%), and low K2O (0.761%–1.41%), and has the signature of sub‐alkaline tholeiitic basalt. It is enriched in large‐ion lithophile elements (Rb, Ba, Th, U, K, Pb) and depleted in high‐field‐strength elements (Nb, Ta). The rock is also enriched in light rare earth elements, shows a negative Eu anomaly, and has a positive εNd(t) value (+0.1 ~ +0.8). The metamorphosed gabbro shares geochemical characteristics and Nd isotopic compositions with contemporaneous mafic intrusions, including the 945–890 Ma mafic sills in southeastern North China Craton, the ~925 Ma Dashigou mafic dike swarm in central North China Craton, the ~925 Ma gabbro in Guyang, northern North China Craton, and the 827–819 Ma gabbro in Langshan, western North China Craton. This age suggests that the gabbro may represent a response to a large‐scale mafic magmatic event in central‐eastern North China Craton during the early Neoproterozoic, potentially linked to the initial breakup of the Rodinia supercontinent.