89

strike and low dip to the west; numerous other fault planes do not appear to
follow any systematic plan. The dense serpentine outcropping in the hills
on both sides of the creek at the tunnel lies in bands trending just west of
north and dipping for the most part steeply to the west. South of the
tunnel, in the cliff east of the creek, the dense bands swing around to the
west and east. If these bands represent structural zones in the-original
igneous rock, if, for instance, they were the dense edges of flows or intru-
sions, they here indicate a system of close folds trending west of north,

pitching southerly, and partly overturned to the east. The maim faults, ©

some of which are of the overthr ist type, presumably, would have accom-
panied this folding. There is no proof, however, that the various bands do
represent such structural zones. The serpentine is similac to the serpentines
in the adjacent Bonaparte valley, classed by Dawson! in the Cache Creek
series of Carboniferous age.

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Entrance
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S © 2 S _-st Ore nodule with parallel streaks
SING 1S) eae of ore in rock below
Z = efi eS Ls
/, 12? AN
Tunnel floor =e Y well_ £2 ) 7 “
Ye. C7 Sf Vis y 4
F Acid iatrusion
1. Dense dark serpentine. : _ & Dense serpentine. :
Z. Yellow, green, altered serpentine ore in scattered grains) 5. Mostly dense serpentine. :
3. Dense serpentine 6. Yellow, green, altered serpentine, stained reddish.
Fractures shown by, heavy line.
Scale of feet
10 o 10 20 30

Figure 15. Fracturing of serpentine at north wall of tunnel, chromite occurrence near
Scottie creek (Figure 14, locality 2), Kamloops district, British Columbia.

The mineral chromite appears to be extremely resistant to secondary
alteration, the processes of serpentinization, and the further change of
serpentine to carbonate and quartz, leaving the chromite unaltered. In
some places, however, veinlets and scattered spots of green, chromiferous
garnets and pink, chromiferous chlorites, traverse the ore-bodies, proving
that slight, secondary alterations of the original chromite have taken place.
The chlorites and garnets, together with veinlets of opaline silica, are
apparently related to the intrusion of quactz diorite and aplitic dykes that
occur nearby cutting the serpentine body. The alteration is not related
to surface weathering. Veinlets of magnesium sulphate found in the
serpentine are probably the products of descending sulphated waters

acting on the serpentine (Plate X).

The chromite is believed to have been formed during the cooling and
crystallization of the original igneous rock from which the serpentine was
derived, the richer ore-bodies forming by the collection of chromite crystals
(segregation) ducing the cooling. This is proved by the association of
chromite with diamonds at this place, page 88. Diamonds are
formed under conditions of great heat and pressure and must have been
one of the original minerals of the rock body. Moreover, the ore lies within

1Dawson, G. M., ‘‘Report on the area of the Kamloops map-sheet.’’ Geol. Surv., Can., vol. VI, pt. B, p. 86B.

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