Gravity And Magnetic Characteristics Of The Gamburtsev Subglacial Mountains, East Antarctica: Implications For Crustal Structure

Seated in the middle of East Antarctica,the Gamburtsev Subglacial Mountains are completely buried by the East Antarctic Ice Sheet and hence are one of the most enigmatic tectonic features on the earth.The mountain range is underlain by 58 km thick crust and 200 km thick lithosphere,but little is known about its crust structure and uplift mechanism.Here I carry out a comprehensive geological and geophysical study on Gamburtsev Subglacial Mountains,based on the airborne geophysical data,satellite gravity and magnetic data?bedmap2?GAMSEIS passive seismic,and the surrounding geological information.Starting with the geological and structural background of the East Antarctica and supercontinent assembly and breakup,I have made a detailed study on the characteristics of potential field and crust structure.Some interesting anomalous regions are delineated by analyzing the potential field anomaly features of airborne/satellite magnetic and gravity anomaly(free air gravity and Bouguer gravity)and the surrounding geological information.Edge detection methods(Total horizontal derivative,Analytic signal,Tilt derivative,Theta map and Eigenvalue analysis)are used to characterize the special condition of faults and geological bodies.Some fault zones and its secondary fractures and thrust structures are found in Gamburtsev Province.In order to get the Curie surface relief and thermal dynamic structure,1D and 2D radical logarithmic average power spectrum method and Parker-Oldenburg iterative inversion method are adopted to the aeromagnetic anomaly of Gamburtsev Subglacial Mountains.Some suspicious intrusions are found and their positions are calculated by Magnetic Dipole Localization and 3D Euler Deconvolution,which possibly are linked with Grenvillian magma intrusion and reactivated during late Neoproterozoic-early Paleozoic higher tectonism.In general,Bouguer gravity anomaly reflect the relief information of lower crust density interface.As one of important constraints on potential work,the GAMSEIS passive seismic data can be used to detect the deep architectures of lower crust and mantle.Here I study the lower crust density interface of Gamburtsev Province by using GAMSEIS passive seismic data and Bouguer gravity anomaly.Multi-scale wavelet decomposition is performed to analyze the Bouguer gravity anomaly of Gambutsev Subglacial Mountains,levelling 3-6 are performed to discuss the regional field and local field.9 faults are revealed from the high gradients of local gravity anomaly of levelling 5.Gravity high blocks are enhanced by the local gravity anomaly in levelling 6,linked with the high density lower crust of Gamburtsev Province.Based on the passive seismic points,wavelet decomposition and radical logarithmic average power spectrum,I adopt Parker-Oldenburg density interface iterative inversion method to calculate the Moho depth to get the crust structure and lithosphere features in Gamburtsev Province.Finally,the crust root is calculated by Airy isostatic model to speculate the effect of upper thick ice sheet to the thick crust in Gamburtsev Province.In order to obtain more information about the crust structure of Gamburtsev Subglacial Mountains,2D geological and geophysical models are carried out,combined with the passive seismic points,inversion results of airborne gravity and magnetic anomalies and the surrounding geological background.Based on the results of our previous studies,the magnetic and gravity anomalies reveal some geological domains on the models.Finally,the origin and evolution of Gamburtsev Subglacial Mountains are discussed systematically on the basis of previous work.The old Gamburtsev Mountains are formed during Pan-African collisional events linked to Gondwana assembly(ca 600-500 Ma).Subsequently,Gamburtsev Mountains suffer an intense erosion as the old climate,but the crust root is kept.With the intensification of erosion,a rift is formed alone the graben caused by the fracture in the brittle and weak zone of crust during early Triassic(ca 250 Ma).High density and thick lower crust result from the mafic magma underplating from upper mantle.Meantime,the massif uplift and denudation reach a dynamic equilibrium,despite the erosion is still going on.A further uplifting of Gamburtsev mountains is possibly reactivated during Cretaceous(ca 130 Ma)linked with Gondwana breakup,which is effected by the upwelling of Kerguelen mantle plume from the button of lithosphere.After the breakup of Gondwana,Antarctica drift southward into high latitudes,a dry climate decelerate the erosion rate.In Oligocene(ca 34 Ma),the ice sheet is growing in Antarctica,glacial denudation cause the Alpine terrain.With the thickening of ice cover,glacial denudation gradually diminished and the heavily incised landscape is preserved.