Rare Element Resources
Bear Lodge Project
Canadian NI 43-101 Technical Report
October 9
th
, 2014
10135-200-46 - Rev. 0
7-9
ferric iron metasomatism), an alteration type often associated with carbonatites, is
spotty in the Bull Hill area, based on petrographic examination of drill core and K
abundance measurements made at the surface with a gamma ray spectrometer.
Pyrite is essentially the only sulfide phase in the breccia matrix and clasts, although
a variety of sulfide phases occurs in the carbonatite.
FeOx
‐
MnOx
‐
REE (FMR) dikes and veins are interpreted to represent primary
carbonatite that was subjected to heavy supergene oxidation and weathering. They
consist primarily of iron and manganese oxides and amorphous silica, along with
variable abundances of silicate and accessory minerals. Silicate and accessory
minerals include biotite, quartz, chalcedony, K feldspar, apatite, barite, and
celestite. The FMR veins and dikes can also host significant supergene REE
minerals, generally of the bastnasite group. The FMR material occurs as stockwork
veinlets, veins and dikes throughout the oxidation zone. Toward the bottom of the
oxidation zone, the FMR veins become transitional to carbonatite and carry
residual carbonate and sulfide, along with mixed primary and supergene REE
mineralogy. In some of the drill holes, friable FMR and transitional carbonatite dike
material were washed away during the drilling process, and a negative sampling
bias is likely in the zones of more friable FMR.
Fenitization, or alkali
‐
ferric iron metasomatism, is widespread across the Bear
Lodge property and may be genetically related to carbonatite intrusion. Fenitized
rocks are often difficult to recognize in the field or in drill core, except in the case of
altered Precambrian granitic rocks, where the dissolution of quartz strongly
suggests interaction with alkali
‐
ferric iron
‐
rich fluids. The effect of fenitization in the
Bear Lodge alkaline igneous rocks is the destruction of primary magnetite, the
replacement of primary plagioclase by K feldspar, and the substitution of Fe3+ for
Al3+ in the lattice structures of the feldspars. Fenitization was identified across the
Bear Lodge property in a series of studies that utilized the cathodoluminescence
petrographic method. The fenite alteration may be accompanied by the
precipitation of LREE
‐
enriched apatite or the LREE enrichment of primary apatite,
and by sulfide deposition. This alteration, its distribution, and paragenesis were
described in a Newmont
‐
sponsored M.S. thesis at the University of Idaho (J.
Felsman, 2009). Duval drill hole WBD
‐
12, collared south of Carbon Hill, intersected
high
‐
grade copper
‐
silver mineralization in a massive fenite halo on a carbonatite
dike.
