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Xama Property Assessment Report
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Bedrock geology of the Property is not well known due to minimal bedrock exposure. Four major
plutonic rock groupings have been recognized. The oldest of these are dioritic rocks of the
Jurassic Limit Lake phase of the Stag Lake Suite which underlies most of the high ground along
the southeast portion of the Property. Next are medium to course grained biotite quartz
monzonites that occur in sparsely distributed rock exposures along the east and west flanks of
the Property. Those to the east are correlative with the early Cretaceous Nithi quartz monzonite
of the Glenannan subsuite and that classification is applied to all similar textured quartz
monzonite within the property. A younger unit includes leucocratic, fine grained granite or quartz
monzonite that is correlative with the Casey quartz monzonite unit exposed at Nithi Mountain.
The fourth unit is similar to Casey rocks but is pale red in colour and occurs at contacts with the
older rocks and in dykes cutting the older rocks and it has a close association with hydrothermal
alteration and mineralization.
Figure 3 - Xama property area geology (from BCGS MapPlace). Faults in purple, contacts
in black, see text (Table III) for lithology legend.
The oldest rocks are dark green pyroxene andesite or basalts of the Upper Triassic Takla
Group. Exposures of these rocks occur in the upper valleys of Skip Creek and in road cuts west
of the creek. At contacts with the granitic rocks, the andesites are variously altered by chlorite,
epidote and saussurite.
The following lithology descriptions are taken from Property mapping as described in Bysouth
(2011) and the reader is referred to that report for more detailed descriptions.
Limit Lake Diorite – This locally defined unit may be the oldest rock unit of the map area is a
part of the GSC’s Jurassic Limit Lake sequence (Anderson, et al 1997). These are fresh, dark
rocks consisting essentially of hornblende and plagioclase in varying proportions. The unit
ranges from diorite or gabbro consisting of about 65% subhedral interlocking hornblende prisms
and 30% plagioclase to granitic textured quartz diorite made up of 40% hornblende in a matrix
of mainly plagioclase and minor quartz, with minor pink orthoclase. The diorite is intruded in
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Xama Property Assessment Report
October, 2014
numerous places by alaskite dykes. Irregular patches of red and salmon red orthoclase
alteration have been noted locally.
Eastern Nithi Quartz Monzonite – This is a medium to coarse grained biotite quartz monzonite
similar to that mapped on Nithi Mountain (Anderson et al, 1997). A striking feature of the rock is
an abundance of subhedral orthoclase crystals that reach lengths of about 15 mm. Most of the
other minerals range in size from 3 mm to 9 mm.
Western Nithi Quartz Monzonite – On the west side of the Casey-Nithi contact, quartz
monzonites and granites of varying textures and general appearance have been mapped in
road excavations. To the south, the quartz monzonite appears as a medium grained (2 mm-6
mm) grey rock with a slight pinkish tinge due to approximately equal proportions of pale gray
plagioclase and pale pink orthoclase. Pink orthoclase megacysts are also present as
inconspicuous subhedral prisms up to 2.0 cm in length. About 30% quartz is also present as
individual grains and segregations of grains up to 13 mm in diameter. Biotite and chloritized
hornblende occur as a mafic component often exceeding 10%. To the north, within and around
the Owl Zone molybdenite mineralization, the quartz monzonites are characterized by a deep
pink to salmon red orthoclase feldspars and a general medium to coarse grain size. In most
exposures, the rock has a bleached, crushed appearance with the plagioclase clay altered and
the mafics converted to chloritic wisps. In the Owl Zone, fine grained dark green mafic rock is
commonly observed. These are assumed to be large xenoliths of older rock that had been
intruded by the quartz monzonite and later granitic dykes. Late stage basalt dykes also occur
here but can be distinguished by an overall fresh appearance compared to the pervasive
chlorite-epidote altered mafic rocks.
Casey Quartz Monzonite –This distinctive granitic rock has been identified within the central part
of the Property where it is interpreted to form a core-like pluton intrusive to the older surrounding
rock units. It has been classified as Casey quartz monzonite based on its low mafic content and
total lack of hornblende. Most of the Casey rocks occur as fine grained leucocratic granites and
quartz monzonites and a medium grey, slightly pinkish coloration. Textures appear aplitic in the
finest grained rocks but with increased grain size, the inequigranular nature of the rock becomes
more evident. Random megacrysts of grey quartz and pink orthoclase are common to the fine
grained rocks but rare in the medium grained granites. The quartz megacysts can occur as
either large grains or as aggregates of smaller grains.
Red Granite - A distinctive red granitic rock occurs as dykes in the Owl Zone where it is closely
associated with the molybdenite mineralization. It is considered to be related to the Casey
intrusions, possibly as an earlier magmatic differentiate. In appearance, the red granite
resembles Casey granite but differs from it in pale red colouration and greater mafic content
which may exceed 10% and include hornblende. It commonly contains remnants of corroded
and engulfed red orthoclase megacrysts. The mafics include chloritic patches, usually with
rounded outlines or, more rarely, prismatic outlines. Some relict biotite shows up as ragged
black flakes but the true identity of the dark components is not evident. Overall the rock appears
to consist mainly of quartz and orthoclase, with about 20% to 25% plagioclase.
Pre-Mineral Dike Rocks – The pre-mineralization dike rocks are likely of early Cretaceous age.
The most important of these are the red granites associated with the Owl Zone quartz-
molybdenite vein systems. Beyond the effects of hydrothermal alteration, the dykes are identical
to the red granite found in road exposures in the east-central part of the Property. Another dyke
rock is a siliceous, pale grey, fine grained to aphanitic alaskite or quartz porphyry, commonly
occurring in small dykes within the dioritic rock unit.