Petrographic Report: Polished Thin Section ME-02P
Rock Type: quartz-sulphide vein
In hand specimen the quartz hosts large, rounded and fractured pyrite grains (up to 2 cm wide). No
fragments of host rock are preserved in the hand specimen. The thin section comprises only a milky white quartz
sulphide vein. The vein consists of white, bladed to euhedral coarse quartz with abundant sulphides, minor
bladed to fan-shaped muscovite, trace amorphous limonite and iron oxide staining in places, and trace
secondary quartz. Muscovite occurs throughout the thin section, but is more prevalent in fractures and between
quartz grains. Secondary quartz is characterized as short (less than 2 mm), randomly oriented veins (up to 0.25
mm wide) of finer grained quartz which is locally associated with fine-grained, anhedral pyrite (Fig. 1). These
secondary veins cut the main vein with the thin section. They display similar texture and suphide mineralogy and
thus both veins observed in this thin section are interpreted as one sustained quartz veining event. Sulphide
mineralogy in the main vein includes coarse, rounded, irregular to euhedral pyrite which contains inclusions of
sphalerite, galena, chalcopyrite, pyrrhotite, and native gold. Pyrite is typically rounded to euhedral and fractured
or brecciated by quartz veining (Fig 2). Pyrite is locally embayed and partly replaced by quartz locally. Sphalerite
occurs as inclusions along fractures in pyrite and also as intergrowths in pyrite. Sphalerite along fractures postdates pyrite. Sphalerite is colourless to very pale grey-brown and rarely exhibits chalcopyrite disease typically
displayed in other samples from this suite. Galena occurs as larger inclusions in pyrite (Fig. 3) and as infill along
fractures, indicating it post-dates pyrite. Chalcopyrite is observed as isolated rounded inclusions within
unfractured portions of pyrite (Fig. 3). Pyrrhotite is always associated with chalcopyrite in pyrite (Fig. 3). The
chalcopyrite and pyrrhotite are locally syngenetic with pyrite. Two grains of native gold (Fig. 3) are associated
with a sphalerite inclusion in pyrite.
Mineral
Quartz-sulphide vein
Quartz
Pyrite
Muscovite
Galena
Chalcopyrite
Pyrrhotite
Sphalerite
Native gold
Limonite
Modal Percent Abundance
Size Range (mm)
65
32
1
1
1
Trace
Trace
Trace
Trace
Up to 1 cm
Up to 2 cm
Up to 0.15 mm
Up to 0.8 mm
Up to 0.15 mm
Up to 0.25 mm
Up to 0.1 mm
Up to 40 microns
Up to 10 microns
The quartz in this sample hosts abundant fluid inclusions ranging in size up to 20 microns. The fluid
inclusions are two-phase (liquid and vapour) fluid inclusions at room temperature, probably comprised of a
brine and water vapour bubble. This is a typical fluid inclusion assemblage observed in epithermal deposits.
Likewise the observed ore mineral and alteration assemblages are typical of an epithermal ore deposit.
There are minor amounts of deformation visible in the sample: these are brecciated pyrite and parallel
sets of microkinks in quartz.
Cliffmont
Sample ME-02P
Page 1
py
qtz
py
qtz1
qtz2
cpy
po
qtz2
gn
Figure 1: Photomicrograph of secondary quartz (qtz2)
veinlets associated with minor pyrite cutting primary,
main vein quartz (qtz1). Photo taken in plane polarized
transmitted light.
Figure 3: Photomicrograph of inclusions of pyrrhotite
(po) associated with chalcopyrite (cpy), native gold
(au) associated with sphalerite (sph), and coarse,
irregular galena (gn) hosted in fractured, anhedral
pyrite (py). Photo taken in plane polarized reflected
light.
py
po
au
Figure 2: Photomicrograph of brecciated pyrite (py)
cut by fine-grained quartz (qtz) vein. Photo taken in
plane polarized reflected light.
sph
cpy
gn
Cliffmont
Sample ME-02P
Page 2