Description
A previously unnamed and unstudied gabbroic pluton was partially mapped and geochemically and petrographically studied for evidence of contamination from the metapelitic component of the country rock. The surrounding moderately foliated granitic rocks are mainly adamellite and granodiorite. The metasedimentary rocks consist of gneisses . and cordierite-sillimanite-mica schists which exist as steeply dipping screens subparallel to the regional foliation and as inclusions and screens in association with the margins of the gabbro. The gabbro is a layered, funnel-sha-ped amphi bole gab bro with large horn bl en de oikocrysts and a coarse homblendite cumulate graning upward into anorthositic gabbro. The gabbro is extensively cut by massive pegrnatite-aplite dike complexes. Field observations and petrographic examination indicate an increase in biotite, potassium-feldspar, tremolit.e and to a lesser extent ouartz in the gabbro border facies adjacent to the rnetasedimentary rocks. Geochemical analysis of the gabbroic and rnetapelitic rocks showed general groupings correlatable to the gabbroic and rnetapelitic rocks with an intermediate group that correlates to the border facies in the gabbroic system and a group of metapelitic gneisses altered to gabbroic chemical composition. These data suggest that the gabbroic melt reacted with the pelitic metasedim entary units to produce a metasomatic exchange in MgO and Cao and to a lesser extent KO and S1O1 •
