Timothy L. Maunula HBSc thesis abstract

Thesis Title: 
Geology and Mineralogy of the Little Pig Vein Mainland Belt Silver Region Thunder Bay District
Timothy L.

The Little Pig Vein, which is thought to be associated with the West Beaver Mine due to its proximity, occurs within the northeast trending Mainland Belt of silver mines.  These deposits are associated with a zone of steeply dipping normal faults within the Southern Province.  These veined faults cut Archean basement rocks, Aphebian metasedimentary and Keweenawan instrusive rocks.

Hand samples and structural data were obtained from the Little Pig Vein and surrounding outcrop.  The sampling was tied into a cut grid.  Investigative methods included hand sample study and petrographic microscopy.

The vein is located within a fault-breccia zone in the Rove argillite.  The vein has a strike of 75 degrees and a dip of 70 degrees to the south.  The argillite is flat-lying with a gentle southerly dip of three to five degrees.  The vein does not enter the diabase.

Within the Little Pig Vein, there appear to have been two pulses of mineralization.  In these open-space filled veins, variable amounts of gangue and sulphide minerals are seen to be present.  The sulphides which are noted in the Little Pig Vein are sphalerite, galena, pyrite and chalcopyrite, in their respective order of abundance.  The gangue minerals which constitute a major portion of the vein are calcite, quartz and fluorite.  No silver was viewed in the samples collected for study.

Migration of metals in the Rove argillite was initiated by cooling diabase dikes and sills.  Faulting formed structural traps for the mineral-bearing solution moving along bedding planes to areas of lower pressures.  Precipitation in the vein proceeded according to sequential deposition.

No silver mineralization was found in the Little Pig Vein.  The silver mineralization may be lacking due to the absence of the mineralization pulse containing the silver metals.  The structural data note the lack of the phase of faulting during which silver mineralization has been noted to occur.  No opening occurred, thus no mineralization was found.  This later stage pulse of silver mineralization has not occurred in the Little Pig Vein.