CH15 Exploration for VHMS Base Metals (Zn, Cu, Pb, Au, Ag) – Pilley’s Island, Newfoundland, Canada

 

Regional, 1000 m line-spaced gamma ray spectrometric/magnetic surveys were completed over much of Newfoundland in the 1980-1990s. Many interesting anomalies were defined in various geological settings, including those over zinc-rich Buchans-type base metal (Zn, Cu, Pb, Au, Ag) prospects on southern Pilley’s Island1 in northern Newfoundland (Figure 1).

GamX CH15 Pilleys Island NF Geology and Airborne Potassium map

Regional ground spectrometric studies (K.L. Ford)2 defined background ranges for eTh and K concentrations within un-altered equivalents of the Robert Arm Group mafic and felsic volcanic rocks (Fig 2 and photo of unaltered basalts below).

GamX CH15 eTh-K chart Roberts Arm Group volcanics

 

 

 

 

 

GamX CH15 altered pillow basalts photo.jpg

GamX CH15 unaltered pillow basalts photo

 

 

 

 

 

GamX CH15 eTh-K chart Spencers Dock Pilleys Island mineralized zones

 

Two of the strongest K anomalies (Fig 1B) are associated with narrow zones of hydrothermally altered pillow basalts, felsic pyroclastics and massive dacitic flows in the hanging walls at Bumble Bee Bight, Mansfield showing and 3B deposits. There, K concentrations are 3 to 4 times background. In the Spencer’s Dock – Old Mine area, potassium reached 12% K (Fig 3).

Maximum K concentrations are associated with an unusual, fine-grained, K-feldspar alteration3 that may precede pervasive sericitization and massive sulphide mineralization4.

Notably, no K enrichment is associated with barren pyritic gossans hosted by pillow basalts on Sunday Cove Island (Fig 4).

GamX CH15 eTh-K chart Boot Harbour Sunday Cove mineralized zones

 

 

 

 

 

 

 

 

 

Although the areas of intense K-feldspar enrichment are less directly associated with VHMS mineralization than sericitic and chloritic alteration, the proximity of potassium anomalies to mineralization provides evidence of significant fluid/rock interaction associated with the mineralizing event.

The ability to detect, map and quantify this potassic hanging wall alteration, from the air and on the ground, provides significant exploration guidance at regional, property and deposit scales. The exploration target outlined in Figure 1, located on the “flank” of the K anomaly by the current (Oct 2014) property operator5 supports this concept. Bear in mind also that the airborne survey was a regional, fixed wing, 1000m line-spaced survey: a more detailed helicopter survey using 50 or 100 m lines would significantly improve K anomaly resolution.

 

 

  1. Ford, K.L., 1992. Airborne gamma ray spectrometer survey of the western Notre Dame Bay area, Newfoundland, 2E/5, 12 and 12H/8,9. Airborne Geophysics Section, Mineral Resources Division, Geological Survey of Canada, 1:100,000.

 

  1. Shives, R.B.K., Charbonneau, B.W., Ford, K.L., 1997, The detection of potassic alteration by gamma-ray spectrometry – recognition of alteration related to mineralization; in “Geophysics and Geochemistry at the Millenium”, Proceedings of the Fourth Decennial International Conference on Mineral Exploration (Exploration 97), September, 1997.

 

  1. Thurlow, J.G., 1996, Geology of a newly discovered cluster of blind massive sulphide deposits, Pilley’s Island, central Newfoundland. Current Research, Newfoundland Department of Natural Resources, Geological Survey, Report 96-1, pp 181-189.

 

  1. Santaguida, F., Hannington, M.D., and Jowett, E.C., 1992, An alteration and sulphur isotope study of the Pilley’s Island massive sulphides, central Newfoundland. In Current Research, Part D, Geological Survey of Canada, Paper 92-1D, pp. 265-274.

 

5. http://www.sokomaniron.com/web/upload/files/Pilley%27s%20Island%20Presentation%20.pdf