The Uruana de Minas geomagnetic anomaly remains aligned with mapped geological structures across four decades

Abstract A persistent crustal boundary may preserve its geometry across magnetic surveys that do not reproduce amplitude. We characterize the partial magnetic-gradient envelope at Uruana de Minas, Brazil, using archives from 1971–1972, 2008 and 2011. The 2011 raw-field gradient reversal supplies the geographic anchor. Historical and 2008 reconstructions recover opposed directional-derivative walls in a fixed 7–9 km annulus, with midpoints near Uruana. A historical bilinear model predicts withheld flight lines with a pooled error of 3.34 nT, compared with 5.00 nT for a plane. Magnetic and independently mapped geological orientation domains reconstruct one another with a worst held-out error of 2.287°, ranking first among 28 supported centers. The 1971-to-2008 eigenframe rotates by only 3.328° despite curvature-spectrum change. Raw-to-corrected 2008 Hessian differences are predominantly isotropic at 6–12 km support, separating processing effects from axis orientation. All six outer curvature roots lie within 0.702 km of the frozen 2011 front, the best placement among 65 parallel translations. Upward continuation preserves the central saddle in 100/100 realizations to 12 km, while the external root migrates and disappears near 4 km at standard support. A recovered scalar–triaxial file preserves the geographic contrast on reciprocal traverses. The surveys recover a structurally registered partial envelope and separate persistent geometry from processing-sensitive curvature. Historical line-offset sensitivity and external angular analogues delimit the result. Geographic vector closure and source mechanism remain unresolved.