ARCTIC AND ASIA LITHOSPHERIC SATELLITE MAGNETIC-ANOMALIES

The polar regions present special problems in magnetic studies because they are largely inaccessible and contain the most disturbed magnetic fields on earth (e.g., effects from auroral phenomena). A processing method, previously developed for south polar satellite magnetic data ( e.g., Magsat), is applied to north polar data to separate the core and external fields from the lithospheric anomalies. The core field is re moved with a least-squares procedure and Fourier correlation coefficie nt filtering effectively reduces the external field signatures. As dem onstrated by improved correlation coefficients and reduced sum-of-squa red differences between passes and between dawn and dusk maps, the pro cessing effectively extracts the static geologic signal from the dynam ic noise (e.g., external fields). Quantitative comparisons of the resu lting lithospheric anomaly map with previous maps suggest that the pro cessing maintains anomaly amplitude while significantly reducing non-l ithospheric energy. The map shows a long-wavelength contrast across th e Ural mountains, the suture zone between the east European craton (+4 nT) and the west Siberian platform (-4 nT). This contrast night be in dicative of significant petrologic differences between these large cru stal blocks. If the steepest portion of the magnetic gradient is marki ng the main Uralian fault, then the fault may extend southward to a la titude coincident with the middle of the Aral sea. The easternmost sec tion of the intraplate Tien Shan is marked by a +3 nT anomaly whereas the remainder of the mountain belt is not associated with a significan t anomaly. This pattern agrees with previous interpretations that sugg est the eastern Tien Shan is supported by a lithospheric root and the rest of the belt is held up by a positive buoyancy force, i.e., it lac ks a root. (C) 1998 Elsevier Science B.V. All rights reserved.