Magnetic Mineralogy of the Lower Continental-Crust
Rocks that were once present in the deep continental crust can be found in surface exposure as xenoliths, as parts of high-grade metamorphic and plutonic terrains, and as obducted lower crustal cross sections. A review of magnetic and mineralogic studies of samples representing all such occurrences shows that magnetite is the only magnetic phase present in significant amounts in these rocks. Thermodynamic considerations indicate that Tipoor magnetite is the expected magnetic oxide under equilibrium conditions that exist in the lower crust, regardless of the primary magmatic composition of the ...
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