Moose River Basin: geology and mineral potential - Geology Ontario

Moose River Basin
DRILLHOLE 75-02
Similar trends occur in this other northern hole (Figure 3.2). The upper
most sampled portion, samples 125 to 137, has a fairly uniform total carbonate
content increasing slightly with depth, and whereas dolomite dominates over
calcite, the latter also increases downward until they are nearly equal. Sample
138 is very deficient in carbonate though the calcite: dolomite ratio drops only
slightly. Samples 139 to 144 have fairly consistent total carbonate and calcite:
dolomite ratio values. However, sample 149 is again low in carbonate and cal
cite now dominates over dolomite. In sample 153 a major change appears,
which continues to the Paleozoic contact, as calcite and total carbonate leap
into the 30 or 40 percent range, and calcite greatly exceeds dolomite. Obvious
changes occur at sample 138 and at samples 144-149-153 and the proportions
are similar to those in drillhole 75-03.
DRILLHOLE 75-05
Upper samples 26 and 28 have high total carbonate values similar to those
of other holes but, beneath this, all samples contain very little carbonate and
dolomite generally exceeds calcite. Values are most like the very low ones ob
tained from the several outcrop samples of Cretaceous sands in the southern
parts of the basin. This change occurs between samples 28 and 39.
DRILLHOLE 75-06
This hole, 16 km to the northwest, yielded similar data (Figure 3.3). Sam
ples 57 to 61 display high carbonate values with the two minerals about equal.
From 63 to 93 the totals are much lower, with dolomite values always about
twice those of calcite. Below this, data are incomplete due to lack of fine matrix
material for analysis but still indicate very high and variable total carbonate
and generally equal proportions of calcite and dolomite. The analyses indicate
a dolomitic but carbonate-poor layer between two carbonate-rich units in this
hole.
HORNBLENDE-PYRITE RELATIONSHIPS
Visual survey of the heavy mineral analyses revealed a distinct relation
between these two minerals. At the upper end of the samples in drillholes 75-02
and 75-06 the percentage of blue-green hornblende is rather high (about 30 to
48 percent in drillhole 75-06, about 22 to 40 percent in drillhole 75-02), but the
percentage of pyrite is quite low (about O to 17 percent in 75-06, and O to 7 per
cent in 75-02) (Figures 3.4 and 3.5). At a certain stratigraphic level in each hole
this relationship reverses. In the lower part of 75-06 the proportions are about
60