The
gold-scheelite-quartz lodes of the Wakamarina valley were the most productive of
the mesothermal gold-bearing areas in the Marlborough Schist. Most of the
production came from the Empire City and Golden Bar mines which worked the
Golden Bar lode. Only 134 m of its 1800 m strike length are accessible, in the
No.2 level of the Golden Bar Mine. A fault has downthrown the Golden Bar Mine
section by 47 m and displaced it left-laterally by 18 m. The lode is a typical
ribbon-banded mesothermal vein, averaging c. 1.75 m wide, and enclosing narrow
horses of schist country rock. It is composed of bands of milky buck' quartz
with thin laminae of schist. Scheelite occurs in short strings of grains within
quartz on the footwall side of the lode and also in small quartz-carbonate
veinlets in the foot wall and hanging wall schist. The lode quartz contains only
localised traces of pyrite and arsenopyrite. They are more abundant in the
wall-rock schist.

The Golden Bar lode lies within a steeply dipping normal
fault, which, on its footwall side, is adjacent to a 40 m-wide, shallow-dipping
mylonite shear zone. Within 1 m of the lode, the shear foliation has been
dragged down to nearly parallel the lode footwall. Wall rock alteration is
manifested by a marked increase in K and Rb, which correlate with abundant
illite/muscovite and K-feldspar within 2 m of the footwall of the lode.
Amphibole, stilpnomelane, and pumpellyite show a progressive decrease towards
the lode. As and Sb increase close to the lode, but are at background levels
within the lode itself. Enhanced Cr (150-430 ppm) in the quartz, relative to the
schists (~40 ppm), suggests that the source hydrothermal fluids passed through
and leached mafic rocks, such as the metabasites from the hanging wall of the
lode (~400 ppm Cr).