TITANIUM ISOTOPE VARIATIONS IN MAGNETITE FROM ROCKS AND ORES IN THE BUSHVELD COMPLEX

The causes for titanium isotope variability in mineralized systems have not been studied in detail. In this contribution, we provide d⁴⁹Ti (relative to the Uniuversity of Chicago, Origins Laboratory Ti standard) per mil values from magnetite from the Merensky Reef, host rock gabbros and the thick, chromite-rich ore seams in the Bushveld Igneous Complex. Magnetite from the gabbros reveals small variations of d⁴⁹Ti of about 0.5 per mil. In contrast, thed⁴⁹Ti values for magnetite from the ores demonstrate a greater variation, exceeding 2 per mil; there also appears to be systematic spatial (vertical) variation in d⁴⁹Ti values. The Ti isotope variations present are principally caused by the abundance and isotopic partiality of different Ti-bearing minerals such as magnetite, ilmenite and rutileforming during fractional crystallization. Continued study of different Ti-rich minerals should further elucidate magmatic ore forming processes.