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GEOPHYSICAL SIGNATURE OF THE DEEP LITHOSPHERE UNDERLYING THE ALTO PARANAÍBA IGNEOUS PROVINCE: CONSTRAINING UPPER MANTLE PROPERTIES

2001; Sociedade Brasileira de Geologia; Volume: 31; Issue: 4 Linguagem: Inglês

10.25249/0375-7536.2001314471474

2177-4382

Maurício de Souza Bologna, Antônio L. Padilha, Ícaro Vitorello,

Maritime and Coastal Archaeology

ABSTRA CTMagnetotelluric (MT) so und ings an: pre se nted fo r the re gi on of Alto Parnn utbn Ig neo us Pro vin ce (A P IP), a complex and economically impo rt ant Cret ace ous mag mati c pro vin ce in we stern Minas Gerais state.In add ition to co nventional widcban d so und ings, suitab le for crust al scale investigations.long -period MT was used fo r the first time in Brazil to investigate the mantle lithosphere .T his pa pe r is focu sed on tile inrcrprcnnion o f the long period data, wh ich probe the conductivity struc ture of the uppe r mantle bct ween 4 0 kill and 250 kill.Th e data have incl uded selected sites across the e ntire APJP, in a I SO-krn long SW-NE profile .The res ults show a hete rogeneous mantle , in terms o f electrica l properties, more cond uctive at depths below XO kin bene ath the borde rs of bot h Parun.i and San fronc iscana basi ns and re sistive to depths dow n to 160 kill in the ce ntral part ofth e profi le, ove r the Brasflia fold-thrust kit.Stic h variurions in tile co nd uctivity profile of thc "pJx:r mantle nrc see m ing ly co mpa tible with the tectonic evo lution o f the APIP, developed in the foldbel t and adjacen t two s ub-bas ins (Ubcrabn and Aba ete ) with C retaceous uplift in the central part and sub sidence in the sub-bas ins.T he ele ctrical mantle he terogeneity from XO to l(iOkill appe ars to be in agreement with the petrochemical data, w hic h sugges t that the mafi c-pota ssic associations ori g inate d at distin ct dept hs from hetero gen eo us upper mantle sources .Consequen tly, mugmmisms cfk.unafughic nml carbonutitic affinities wo uld occ ur in re gions coi ncidenta l with enhanced conductivities at sha llowe r uppe r mantle dept hs, whe reas the ones ofkimbcrlitic and lamproitic affinities wou ld occ ur ill re gions with deep re sisti ve keels.T he geo physical signat ure ccrrobonucs the idea of a patchwork lithosp here composed by oldercomincnralblocks merged wi th younger blocks during continental W llvcrgcm:e.The re fore , a new approach in diamond exploration requ ire s the rc-c vnluaticn by deep probing geop hysical methods , such as MT deep sou nd ings, o f tcctcnicull y yo unge r reg ions thru mig ht ha ve ncccnuuodntcd ancient frugmcms.