Regional Modeling of the Lithospheric Magnetic Field from Local and Satellite Constraints: A Case Study of the Xinjiang Region

We investigate the total intensity F of the lithospheric field over the Xinjiang region (34-50 degrees N, 73-96.5 degrees E) through a three-dimensional surface spline (3DSS) model with 0.1 degrees x 0.1 degrees resolution, constrained by 296 ground measuring points recorded between 1936.0 and 2000.0, 10,236 aeromagnetic data points during 1970-2011, and 10,236 satellite model predictions of CHAOS-7.5. We compare predictions of the new model against those from the regional spherical harmonic (RSH) model, two-dimensional surface spline and Taylor polynomial models, and global models LCS-1 and NGDC720. We select 13,605, 18,723, and 23,841 points from three altitudes to create 3DSSS (sparse), 3DSSM (middle), 3DSSD (dense) models, allowing for external field contamination and boundary effects. Results show a good agreement between the spatially detailed 3DSS model and aeromagnetic data. The new model reveals lower error after inspecting the residuals and root mean square error (RMSE), the coefficients, and correlation coefficients between 3DSS models. The new model enables useful geological interpretation; four magnetic anomalies of Xinjiang are coincident with geological structures, and anomalies are also consistent with the tectonic facies and especially the geological distribution in eastern Tianshan. The lithospheric magnetic field in the research area reflects the magnetization difference of the basement, and its geological origin is ascribed to multi-stage magmatism. Results imply that the 3DSS model can model the spatial distributions robustly and is not sensitive to the number of modeling points. The induced field dominates the continent and has a magnetization process in the WE direction in Xinjiang.