Olivo, G.R., Chang, F., and Kyser, T.K., 2006. Formation of the ...

614 OLIVO ET AL.
layers of quartz and tourmaline and centimeter-sized slabs of
foliated, pyrite-rich wall rock. Elongated crystals of quartz
and tourmaline oriented at high angle to the vein margins
occur locally, close to the footwall contact. In the Central
zone, the North Dipper vein is mainly layered with tourmaline
and quartz ribbons oriented parallel to subparallel to the
vein margins (Fig. 5D). The North Dipper vein in the Sigma
mine pit comprises calcite (5 vol %), pyrite (2–5 vol %), rutile
(1–3 vol %), and minor amounts of chlorite, muscovite,
pyrrhotite, chalcopyrite, galena, bismuth tellurides, and gold.
Locally the sulfide content can be as high as 10 vol percent
(mainly pyrite). The modes of occurrence of the vein filling
minerals are described below and illustrated in Figure 6A-F,
and the interpreted paragenetic sequence is summarized in
Figure 7A.
In the milky irregular zones, quartz occurs either as grains
up to 5 mm long or as fine-grained (