geochemistry and mineralization of the archean titan (roaring river) intrusion, thunder bay, ontario
abstract
the 2690 ± 3.2 ma titan intrusion is an approximately 7 by 3 km, roughly ovoid,
mafic-ultramafic intrusion, located just north of the inferred boundary between the
winnipeg river and marmion terranes. outcrop in the area is relatively sparse, largely
due to cover from pervasive glacial till and proterozoic diabase sills associated with the
midcontinent rift. titan consists of a variety of lithologies, including leucogabbros,
melagabbros, gabbros, and pyroxenites, which are distributed throughout the intrusion.
both mafic and felsic dikes are observed in outcrop, as are felsic breccias. titan consists
of a single magma body, with one pulse of magma which has subsequently undergone
fractional crystallization within a closed system. this is supported by smooth linear
trends in the major element bivariate plots, with moderate amounts of scatter, and
consistent, tight primitive mantle normalized ree trends. titan samples have a range of
(la/sm)n from 0.7 to 3.8, a range of (gd/yb)n from 2.3 to 7.4, and a range of nb/nb*
values from 0.02 to 0.47. [...]