HomeGeology & Mineralisation
More information about Andy Well
The Wilber quartz reef is hosted within a NNE-SSW striking shear zone and this shear is hosted within a sequence of pillowed and variolitic high-Mg basalt. The basalt is intruded by at least three types of intrusion:
- an early xenolith‐rich intermediate porphyry with prominent biotite,
- younger feldspar‐quartz phyric, and
- a proterozoic dolerite that cross cuts all geology in a NW-SE orientation.
The xenolith‐rich intermediate porphyries are always cut by younger feldspar quartz phyric porphyry dykes.
The high‐Mg basalts are typically chlorite‐carbonate altered, however when incorporated within the shear and proximal to the quartz reef they are replaced by a strong chlorite‐sericite‐carbonate‐pyrite alteration assemblage. Sometimes talc and biotite are included in this assemblage.
The Wilber mineralisation consists of a thin (1-2m wide) zone of steeply dipping quartz-carbonate vein(s) within moderately altered and sheared high-Mg basalts. Mineralisation is associated with disseminated pyrite within the vein and selvedge, with minor amounts of chalcopyrite, galena and sphalerite present. Typical alteration within the host rocks consists of moderate degrees of silicifcation, carbonate alteration, and chlorite/biotite alteration. Trace amounts of fuchsite have been observed in the lode itself.
Where the quartz vein is present in the mineralised structure, Au grades are in general above 10g/t, with extensive fine, disseminated visible Au observed in drill core. Where the quartz vein is not present in the host shear zone, but within the mineralised envelope, grades tend to be in the order of 0.3-0.4g/t. Overall, mineralisation identified to date appears to plunge moderately to the south, with a possible internal high grade plunge.
Figure 2 – Long Section of the Wilber Lode deposit.