Location of the tectonic boundary between the Paleoproterozoic Jiao–Liao–Ji Belt and the Archean Longgang Block in the Lianshanguan area, northeastern China

The tectonic evolution of the Paleoproterozoic Jiao–Liao–Ji Belt, which is located in the North China Craton in northeastern China, is the subject of ongoing debate. Most previous studies on this belt have been based on traditional geological methods, with most of the data being obtained from the surface, leading to uncertainties regarding the deep geological structure of the belt. This has restricted our understanding of the tectonic character and development of the belt; however, this limitation could be overcome by geophysical studies. Here, we analyze and interpret newly collected rock physical property data (density, magnetic susceptibility, and resistivity) and non-seismic geophysical data (gravity, magnetic, and magnetotelluric sounding data) for the Lianshanguan area to infer the location, configuration, and nature of the tectonic boundary between the Paleoproterozoic Jiao–Liao–Ji Belt and the Archean Longgang Block. The Lianshanguan rock mass, which belongs to the Archean Longgang Block, shows a weak gravity anomaly (0–6 mGal) and high resistivity (103.6 to 104 Ω·m). The area south of the Lianshanguan rock mass consists of the Paleoproterozoic Liaohe Group and displays an intermediate magnetic anomaly (0–200 nT) and low resistivity (10–102.5 Ω·m). We therefore infer that the tectonic boundary of the Jiao–Liao–Ji Belt is located along the southern margin of the Lianshanguan intrusion. We also show that the tectonic boundary in the Eastern Liaoning–Southern Jilin area trends E–W and extends from Shuangtaling through Lianshanguan, Caohecheng, Balidianzi, and to Guaimozi. The boundary between the Longgang Block and the Jiao–Liao–Ji Belt dips predominantly to the south, suggesting an extensional tectonic regime during the Paleoproterozoic time.