Petrology and Cu-Ni-PGE Mineralization of the Bovine Igneous ...

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mineralization in many of the other mineralized mafic-ultramafic intrusions of the MCR (Rossell, 2008). Figure 6. Generalized cross-section of the BIC intrusion along section line A-A’ (Fig. 2). Blue bars denote sulfide concentration in drill cores BIC02-02, BIC01-01, and BIC-2 (from Rossell, 2008). 1.2 Previous Studies Previous studies of the BIC have been limited to 1) reconnaissance mapping by Dean Rossell (1990-1996), 2) exploration drilling by Kennecott Mineral Company (1995 to present), 3) brief company reports on the petrography of select samples by Barnett (1995), Hauck (2002), and Johnson (2007), and 4) a field trip guide for the 2008 Institute on Lake Superior Geology by Dean Rossell (2008). More recently, whole rock geochemistry and samples collected for geochronology have been collected by the USGS (Schulz and Nicholson, 2009) 10
and a sulfur isotope study is underway by a student at Indiana University under the supervision of Dr. Ed Ripley. No detailed geologic map of the BIC or its surrounding geology exists. Dean Rossell compiled a reconnaissance map of the intrusion between 1990 and 1996. He distinguished three units on the elongate hill that makes up the surface expression of the intrusion (Fig. 2). The best exposure of outcrops occurs around the flanks of the hill, where the topography is steepest. Since it was first drilled in 1995, over 66 holes have been drilled by Kennecott Exploration into the BIC intrusion and surrounding country rock. Every drill hole was logged for lithology, structure, and mineralization and measured for magnetic susceptibility. Sulfidebearing intervals were assayed for base and precious metals. Three petrographic reports have been prepared for Kennecott Mineral Company. These reports were written by Barnett (1995), Hauck (2002), and Johnson (2007) and consist of descriptions of thin sections taken of intrusion rock types and footwall samples from several drill cores. Mineralogy and textural associations were noted in detail for both sulfide and silicate minerals, and were used to characterize the three basic stratigraphic units of the intrusion defined by Rossell (2008). In 2008, Dean Rossell compiled a field trip guide on the BIC for the 2008 Institute on Lake Superior Geology meeting held in Marquette, Michigan. In the guide, Rossell summarizes the current state of knowledge on the BIC, which includes his earlier field mapping, a cross-section based on core logging descriptions of three drill core, and the company petrographic reports. Rossell concludes that the intrusion is made up of the three 11
Page 1 and 2: Petrology and Cu-Ni-PGE Mineralizat
Page 3 and 4: Acknowledgements I would like to th
Page 5 and 6: While this cumulate stratigraphy of
Page 7 and 8: 4.6.1 Little BIC...................
Page 9 and 10: Figures 1 Geologic Map of Southwest
Page 11 and 12: 1.0 Introduction The failed rifting
Page 13 and 14: 08BIC044 • Figure 2. Geology of t
Page 15 and 16: 1.1.2 Baraga Group Collision of an
Page 17 and 18: lithosphere and the lower crust (Ni
Page 19: 1.1.4 Bovine Igneous Complex The (B
Page 23 and 24: those goals will be to characterize
Page 25 and 26: 2.1 Core Logging and Sampling Three
Page 27 and 28: exporting data layers from ArcMap a
Page 29 and 30: Figure 7. Modal rock type classific
Page 31 and 32: were chosen from each rock type whi
Page 33 and 34: outcrops are very coarse-grained an
Page 36 and 37: Figure 12. Bedrock geologic map of
Page 38 and 39: The feldspathic wehrlite is in turn
Page 40 and 41: unit to subprismatic at the top (Fi
Page 42 and 43: Figure 15. Stratigraphic variation
Page 44 and 45: 3.2.2 08BIC044 This 731m long hole
Page 46 and 47: The lower feldspathic wehrlite unit
Page 48 and 49: the dramatic increase in clinopyrox
Page 51 and 52: Figure 17. Generalized lithostratig
Page 55 and 56: Figure 21. Lithostratigraphy of dri
Page 57 and 58: Figure 23. Modal mineralogy of plag
Page 59 and 60: A B Figure 25. A.) Photomicrograph
Page 61 and 62: A B Figure 27. A.) Photomicrograph
Page 63 and 64: 3.3 Mineral Chemistry and Cryptic L
Page 67 and 68: All values in parts per million (pp
Page 69 and 70: 4.0 Discussion The petrographic, mi
Page 71 and 72:
the lower feldspathic wehrlite unit
Page 73 and 74:
would expect from the fractional cr
Page 75 and 76:
Cumulate Stratigraphy Pl+Cpx+Ox Cpx
Page 77 and 78:
orthocumulate zone similarly increa
Page 79 and 80:
upper slate of the Michigamme forma
Page 81 and 82:
C. Emplacement of upper ultramafic
Page 83 and 84:
Figure 34. Normalization spider dia
Page 85 and 86:
aluminum but higher titanium, iron,
Page 87 and 88:
B. QFM C. QFM-2 Figure 36. Mineral
Page 89 and 90:
Figure 37. Mineral paragenesis calc
Page 91 and 92:
Figure 38. Plot of Cu, Ni, Pd, and
Page 93 and 94:
wehrlite followed by a feldspathic
Page 95 and 96:
Johnson, R.C., 2007, Petrography an
Page 97 and 98:
Appendix A Petrographic Description
Page 99 and 100:
Appendix A-1 Bulk Rock Petrography
Page 101 and 102:
044-414.7 fwer med crs to crs wehrl
Page 103 and 104:
Appendix A-2 SILICATE MINERAL PETRO
Page 105 and 106:
044-497.5 fwer med to med crs calci
Page 107 and 108:
Appendix B Mineral Chemical Data Py
Page 109 and 110:
Spectrum 3 53.26 0.94 2.43 7.6 0 15
Page 111 and 112:
Average 86.1 50.1 8.1 41.8 SD 0.37
Page 113 and 114:
Spectrum 3 54.15 0.84 1.64 5.3 0 16
Page 115 and 116:
Spectrum 5 55.36 1.56 5.96 0 19.97
Page 117 and 118:
Ol.2 40.99 16.16 0 42.84 100.0 82.5
Page 119:
Spectrum 6 53.95 0.95 2.41 6.92 17.
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Petrology and Cu-Ni-PGE Mineralization of the Bovine Igneous ...

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