Crustal magnetic anomaly in the Ordos region and its tectonic implications

• We investigate crustal magnetic anomaly in the Ordos regions.
• Curie surface is calculated using the continual model inversion method.
• The well correlation between the Curie surface and the seismicity.
• The deep materials in the northeast margin of Tibet Plateau mainly flow northward to the Qilian fold belt.

In this paper, the NGDC-720-V3 model is utilized to investigate the distribution of crustal magnetic anomaly and Curie surface in the Ordos block and its surrounding areas. The Curie surface is compared with the regional heat flow, Bouguer anomalies, Moho, and seismicity. The interior block has strong wide-distributed magnetic anomalies, well corresponding to the basement lithofacies. The surrounding areas have weak anomalies of various strikes and intensities. The magnetic anomaly confirms the geological finding that the Yabulai and Bayanhot Basins are small blocks detached from the northern Ordos block. The magnetic anomalies at the satellite altitude reveal that deep materials flow northward from the northeast margin of Tibet Plateau to the Qilian fold belt. The depth of Curie surface ranges from 24 to 42 km, and the Ordos block is dominated by Curie surface depth over 32 km and average heat-flow value of 44 mW/m2. The distribution of Bouguer anomalies is consistent with that of magnetic anomalies. The well correlation between the Curie surface and the seismicity is also explained.

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