Dike intrusion as a possible cause of linear Martian magnetic anomalies
F. Nimmo,Geology 28, 391-394, 2000.
A model in which the ancient, 100-200-km-wide magnetic lineations in
the southern hemisphere of Mars are formed by repeated dike intrusion is proposed. On the basis of magnetizations observed at terrestrial mid-ocean ridges, a likely upper bound on the Martian crustal magnetization is about 15 A/m. This upper bound gives a minimum magnetized layer thickness of 35-60 km. Because the magnetic material is likely to be magnetite, the long-term
stability of the anomalies probably requires ilmenite lamellae to have exsolved
from the magnetite. This
exsolution process provides an upper bound on the cooling time available
of 10^2 - 10^5 a. These bounds can be satisfied
if the magnetic anomalies are created by successive intrusion of dikes from
20 to 2000m wide. Production of a Martian crust 35-60 km thick by rifting requires either
mantle potential temperatures in excess of 1430 C or stretching
factors greater than 5.
Francis' Page
Department of Earth Sciences
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