Magnetic mineralogy of basalts from Leg 49.

Abstract

Comprehensive investigation of ferromagnetic minerals contained in basalt samples collected on DSDP Leg 49 (Reykkjanes Ridge and northern Mid-Atlantic Ridge traverse), using combined techniques of thermomagnetic measurement, electron microprobe analysis, and reflected light microscopy, suggests the following conclusions: 1) the degree of low-temperature oxidation of titanomagnetite is not necessarily related to the age of the rocks; 2) the degree of low-temperature oxidation does not directly depend upon the sub-bottom depth; 3) the degree of oxidation is surprisingly low at all of the Leg 49 sites except at Site 410, where the rocks are of breccia and closely related origins; 4) the Curie temperature of the basaltic layer was certainly higher than room temperature and possibly higher than 150oC when the rocks initially erupted at the mid-oceanic ridge. The lack of relationships between oxidation and age or depth suggests tha oxidation is probably more influenced by hydrothermal circulation in the basement.-Authors