The Silver Bird area is underlain by regionally metamorphosed Paleozoic sedimentary and volcanic rocks (Whitewater Metamorphic Complex) which consist largely of gneisses with augin-shaped porphyroblasts of feldspar and large amounts of quartz occurring as veins, lenses, and irregular patches throughout the gneiss. As well coarse-grained amphibolite and garnet-bearing quartz-biotite schists occur with several lenses of coarsly crystalline limestone, locally with tremolite. South of the Polaris-Taku Mine (104K 003) the phyllitic sediments have a very high silica content and the presence of limestone suggests a correlation with the Permo-Pennsylvanian chert-limestone succession (Stikine Assemblage).
There are two main showings on the Silver Bird. These occur in sheared and altered volcanics over widths from 61 to 305 metres. The first showing occurs along a small creek, known as Sulphide Creek, within a shear zone that cuts sericitic schist. The shear strikes 080 degrees and dips steeply southward. Mineralization within the shear consists of pyrite and arsenopyrite across a width of about 20 centimetres and a length of about 46 metres. In 1947, a hand picked sample assayed 7.5 grams per tonne gold and trace silver (Minister of Mines Annual Report 1947).
There has been considerable fracturing along this shear and in places it is filled by a quartz-cemented breccia which is mineralized with arsenopyrite, together with some pyrite and stibnite. The arsenopyrite occurs disseminated and as crystals up to 0.6 centi- metres in length. The stibnite is described as fairly massive and irregularly distributed.
The second showing, occurs in another shear zone on Middle Creek, about 1.6 kilometres north-northwest of the first shear. The host rock is a quartz-biotite schist, striking northwest and dipping southwest which is crosscut by a shear zone located about 3 metres west of a 0.6 metre wide felsite dyke. Both the shear and the dyke strike northwards.
The shear zone, which ranges from 0.9 to 1.5 metres in width, consists of a very dark, partly leached silicified zone containing pyrite and arsenopyrite. At the southern end of its exposed length, the shear dips moderately westward. In 1947, a 121 centimetre chip sample taken across the shear assayed 5.14 grams per tonne gold and 6.86 grams per tonne silver. At the northern end of the shear, the mineralized zone dips gently westward and in 1947, a 106 centimetre sample assayed 0.34 grams per tonne gold and no silver (ibid.).
Late in 1931 the mineralized zone was discovered by R.G. Wilms & associates who staked 20 claims in the Silver Bird, Mineral Mountain, and Golden Star groups. The property was optioned to the Alaska Juneau Gold Mining Company, who carried out some trenching on the shear zones. No further work was reported and the property lay idle for a number of years. The South Slope group of claims was located on the showings in 1940 by Misters Bacon, MacDonald, and Smith, however, no development work was reported at this time.
An airborne geophysical survey flown in 1990 by Dighem Surveys for KRL Resources Corp. indicated several anomalies over the SEA property.
A preliminary exploration program was carried out on the Sea claim on behalf of KRL Resources Inc. during 1991. The claims covered the Silver Bird MINFILE occurrence but these were not visited due to topographic and vegetative constraints. A total of 42 stream silt samples, 43 rock samples, and 106 soil geochem samples were collected. Assay results were generally discouraging, although there were anomalous copper and zinc values in many of the samples. The fine arsenopyrite found in some of the outcrops is encouraging, since gold at the nearby Polaris - Taku deposit is closely associated with similar arsenopyrite mineralization.
