Tim's Gossan

Prospect, Active

Alternative names

TG

Commodities and mineralogy

Main commodities Ag; Pb; Zn
Other commodities As; Au; Cu; Sn
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale NL
Quadrangle map, 1:63,360-scale A-4
Latitude 64.1724
Longitude -157.5841
Nearby scientific data Find additional scientific data near this location
Location and accuracy Tim's Gossan prospect is 2.8 miles west of VABM 1954 'Round Top' in a saddle between hill 1730 and 1560 on an east-west trending ridge in the Kaiyuh Mountains. The prospect drains into the headwaters of California Creek and Minnesota Creek in the southeast corner of section 24, T. 15 S., R. 6 E., of the Kateel River Meridian. The location of the site is where the rubble crop of mineralized gossan is found.

Geologic setting

Geologic description

Outcrop in the prospect area is scarce and the geology is largely defined by rubble. The country rocks in the area of Tim's Gossan prospect are Paleozoic to Proterozoic(?) pelitic schist and quartzite of greenschist- and amphibolite-grade, locally accompanied by blueschist-grade (Patton and others, 2009). Lesser amounts of carbonate rocks and metavolcanic rocks are also present (Gemuts and others, 1983). All rocks have undergone multiple periods of deformation and generally trend northeast. The country rocks are intruded by a large intrusive complex that trends northwest, parallel to a major regional fault about 0.6 mile east of the prospect (Harris, 1985).
Tim's Gossan is interpreted by Harris (1985) to be part of the Round Top system (Flanigan, 1998). The gossan is hosted in locally brecciated quartz-chlorite-muscovite schist. The brecciated schist is mildly bleached, iron-stained, and altered to clay. The gossan is black or gray, massive, and extends over an approximately 250 by 820 foot area. Sooty, amorphous, yellow, black or gray, and red-orange supergene oxides fill 0.6- to 1.2-cubic-inch voids in the gossan. The gossan is composed of a thick, dark, iron and manganese coating on small, foliated siliceous structures (Flanigan, 1998). Work carried out between 1980 and 1983 defined silver-lead-zinc replacement style mineralization in chloritic limestone and dolomite dipping 40 to 50 degrees northeast into a northwest trending fault zone (Ellis and Roberts, 2014).
Tim's Gossan prospect contains high levels of lead, zinc, silver, and manganese and anomalous values of tin and arsenic. Drilling at Tim's Gossan in 1983 intersected graphite-siderite gouge zones containing high levels of zinc, lead, and silver (Ellis and Roberts, 2014).
Geologic map unit (, )
Mineral deposit model Zn-Pb Skarn? or Polymetallic veins? (Cox and Singer, 1986; model 18c or 22c).
Mineral deposit model number 18c? or 22c?
Age of mineralization A K/Ar date on potassium feldspar from the oldest porphyry at the nearby Round Top prospect (NL011) is 74 +/- 2.8 Ma. Mineralization is likely younger than this (Harris, 1985).
Alteration of deposit The brecciated schist is mildly bleached, iron-stained, and altered to clay (Flanigan, 1998). Mineralization in chloritic limestone and dolomite is also observed (Ellis and Roberts, 2014).

Production and reserves

Workings or exploration
Tim's Gossan was first discovered in 1980 during a regional reconnaissance program completed by Anaconda Minerals Company (Anaconda). In 1982 and 1983 Anaconda completed soil sampling at Tim's Gossan and nearby Round Top (NL011), a MaxMin (small loop frequency domain electromagnetics) survey, and a few shallow drill holes (Ellis and Roberts, 2014). The surface gossan and corresponding geochemical anomaly is 30 to 110 meters wide by 800 meters long. Surface gossan samples contain values up to 4.52 percent lead, 0.84 percent zinc, 211 grams per tonne (g/t) silver, 1700 parts per million (ppm) tin, 415 parts per billion (ppb) gold, 1255 ppm copper, and more than 1000 ppm arsenic (Flanigan, 1998; Western Alaska Copper and Gold, 2015). Anaconda drilled 7 shallow holes at Tim's Greisen in 1982 that totaled 400 meters. Four of the shallow drill holes explored the surface anomaly and intercepted gossan zones of 5.9 meters, 7.8 meters and 3.75 meters in width (Western Alaska Copper and Gold, 2015).
In 2012 Western Alaska Copper and Gold completed a soil geochemistry program collecting samples on a 500 by 100 meter grid covering Tim's Gossan, Round Top (NL011), and TG North (NL027) in order to determine the extent of the Round Top geochemical signature. They collected over 1,050 soil samples. Silver and lead were the most anomalous metals in soil samples over Tim's Gossan. Western Alaska Copper and Gold also completed an airborne magnetic and radiometric survey in 2012 over Tim's Gossan (Ellis and Roberts, 2014).
Indication of production None

References

References

Reporters N.V. King (Alaska Earth Sciences)
Last report date 3/15/2016