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	15 de Outubro (Fundação do Observatório Nacional em 1827)
	3 de Abril (Proclamação do Ano Internacional da Geofísica pela ONU em 1957)
	23 de Junho (Declaração da Antártida como território de livre pesquisa em 1961)
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	20 de Novembro (Abertura do 1º Congresso da Sociedade Brasileira de Geofísica em 1989)
	30 de Outubro (Fundação da SBGf em 1978)

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litosfera | magnetotelúrico

O método magnetotelúrico na litosfera

O Departamento de Geofísica do IAG/USP promove no dia 23 de maio (segunda-feira), às 16hs, no Auditório 2 do IAG/USP, a palestra: “What does magnetotellurics tell us about the structure and composition of the lithosphere? Examples from Australia, Antarctica and Africa”. A apresentação do trabalho sobre o método magnetolúrgico ficará à cargo da Profa. Dra. Katherine Selway (University of Adelaide).

Resumo da pesquisadora:

Magnetotellurics (MT) is a passive electromagnetic method that is one of only a few geophysical techniques able to image lithospheric-scale structures. MT data are widely relied upon to identify features such as the location and dip of paleo-suture zones, as well as features associated with modern subduction and rifting.

A comparison of contrasting geological evolutions of different terranes in Proterozoic Australia has led to a broad acceptance that the region formed through the assembly of several distinct cratons. The proposed suture zones are hidden beneath significant sedimentary cover, making their identification through traditional geological means impossible.

Results will be presented from several MT profiles crossing major terrane boundaries that show lithospheric-scale structures and are interpreted to represent paleo-suture zones. Likewise, results will be presented from East Antarctica, which similarly suffers from a lack of outcrop and is also an important component of global supercontinent reconstruction models. Inversions show that even in this extreme environment, MT can image suture zones and other major features.

However, despite the demonstrated ability of MT to image such features, many questions remain about the interpretations of MT data and the causes of the imaged conductive zones. Recent advances in petrophysical investigations into the causes for enhanced electrical conductivity at lithospheric pressure and temperature conditions will be discussed, which have important implications for the ways in which we can use MT to understand not only tectonic structures but also mantle composition and ore deposits. Current research around the Olympic Dam iron-oxide-copper-gold system in South Australia and the East African Rift region in Tanzania will be presented which demonstrate how MT may be utilised to improve our understanding of Earth composition and systems.