Program, Abstracts, and Guidebooks - University of Minnesota Duluth

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STOP lB XENOLITH-HYBRIDIZED GABBRO—BANDED GABBRO (Fig. 2)
A large, relatively inhomogeneous, xenolith of
anatexite appears to be engulfed within massive, inclusionbearing,
hybridized gabbro.
Massive gabbro is overlain by gabbro with discontinuous
and/or disturbed layering, and moderately well developed
foliation of plagioclase. These gabbros are essentially
two pyroxene, olivine poor, bictite—oxide (magnetite present
up to 15 percent) rich, rocks.
STO? 1C GABBROS - LAURVIKITES (Fig. 2)
Continuation of traverse northward, along Highway 17,
across layered gabbros, with zones of anatexite and intruded
by dikes of laurvikite; and layered laurvikites.
The gabbros show;
(1) rhythmic (and cryptic) layering;
(2) foliated and possibly lineated
fabric as exhibited by plagioclase
and clinopyroxene;
(3) zones of reaction inclusions;
(4) several ring (?) dikes, with
associated apophyses, of láurvikite.
Greater volume of dikes is indicative of the nearness
of contact with overlying laurvikites. Dike emplacement
occurred during periods of gabbro extension.
The gabbros contain pagioclase, clinopyroxene, olivine
(up to Fa75±5) with minor, but significant amounts of
ilmenomagnetite, biotite, sodic amphibole, apatite, idding—
site, sulf ides, and antigorite.
The contact between overlying, layered laurvikites
and layered gabbros appears conformable and gradadional
over a short distance.
The laurvikites show;
(1) zones of abundant xenoliths;
(2) colour variation from dark green to
red corresponding to a transition,
apparently gradational and cyclic,
from a more melanocratic, anhydrous
mineralogy, further characterized by
the presence of hematite perthite;