Twenty-five cross-sections are presented that display the detailed igneous geology for
several areas of the Babbitt Cu-Ni deposit. Shown in the cross-sections are the stratigraphic
relationships of at least seven major igneous units - Units I through VII of the Partridge River
Troctolite Series (PRTS). However, not all seven units are equally present throughout the deposit
due to "pinch-out" relationships and lateral gradational rock type changes. In addition to these seven
units, three new units are briefly discussed and include the: 1) Bathtub Layered Series (BTLS) of
Hauck (1993); 2) Basal Ultramafic Unit (BU Unit) of Severson (1994); and 3) Upper Layered Series
(ULS). Small plug-like bodies of Oxide-bearing Ultramafic Intrusions (OUIs) are also locally
present within the Babbitt deposit. They intrude the rocks of the PRTS and are often positioned
adjacent to, or within, fault zones.
Rock types found within the footwall rocks beneath the Complex at the Babbitt deposit are
also described. Metamorphic textural variations are described for select units within the Virginia
Formation (RXTAL, DISRUPTED, and BDD PO units). These textural variations indicate that the
effects of structural deformation, recrystallization, and partial melting are more pronounced than
previously thought. The exact origin of the textures is unknown, but is believed to be associated
with early stages of Duluth Complex emplacement. Also present within the basal portion of the
Virginia Formation are early intrusive rocks that predate emplacement of the Partridge River
intrusion (PRI). These early intrusive rocks are referred to as the Virg Sill and "Massive Gray" Unit
("MG" Unit); both are interrelated and are submembers of a single composite sill.
At least three major structural features are present in the footwall rocks and include the:
Local Boy Anticline, Bathtub Syncline, and Grano Fault (for a more detailed discussion see Part B -
Severson et al., 1994). During intrusion of the Partridge River intrusion, specifically during
emplacement of the lowest unit (Unit I), the Local Boy Anticline and Bathtub Syncline were
important factors controlling how the base of the Complex was formed (see Part B). In addition,
these same structures also appear to have been repeatedly reactivated during continued emplacement
of the Complex and affected the distribution of specific units within overlying Unit III and the
BTLS. Also, the distribution of the "MG" and Virg Sill units are affected by these same two
structures. These relationships suggest that reactivation of the structures created "void spaces" into
which specific PRTS units were emplaced. The exact details and of this complicated emplacement
history have yet to be unraveled.
Natural Resources Research Institute, University of Minnesota, Duluth, 5013 Miller Trunk Highway, Duluth, MN 55811-1442; Funded by Minnesota Technology, Inc., the Iron Range Resources and Rehabilitation Board, and Arimetco International Inc. of Tucson, Arizona
Severson, Mark J; Patelke, Richard L; Hauck, Steven A; Zanko, Lawrence M.
The Babbitt Copper-Nickel Deposit: Part C: Igneous Geology, Footwall Lithologies, and Cross-Sections.
University of Minnesota Duluth.
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