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File Created: 24-Jul-1985 by BC Geological Survey (BCGS)
Last Edit:  26-Feb-1989 by Wim S. Vanderpoll (WV)

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NMI
Name NORTH FORK, BIG ONION Mining Division Alberni
BCGS Map 092L006
Status Prospect NTS Map 092L02W
Latitude 050º 04' 23'' UTM 09 (NAD 83)
Longitude 126º 48' 06'' Northing 5549068
Easting 657302
Commodities Gold, Silver, Copper, Zinc Deposit Types I06 : Cu+/-Ag quartz veins
Tectonic Belt Insular Terrane Wrangell
Capsule Geology

The North Fork occurrence is located north of the Zeballos gold camp, an area underlain by Lower Jurassic Bonanza Group basaltic to rhyolitic volcanic rocks. Conformably underlying the Bonanza rocks are limestones and limy clastics of the Quatsino and Parson Bay formations, and the tholeiitic basalts of the Karmutsen Formation, all belonging to the Upper Triassic Vancouver Group. Dioritic to granodioritic Jurassic plutons of the Zeballos intrusion phase of the Island Intrusions have intruded all older rocks. The Eocene Zeballos stock, a quartz diorite phase of the Catface Intrusions, is spatially related to gold-quartz veining in the area. Bedded rocks are pre- dominantly northwest striking, southwest dipping, and anticlinally folded about a northwest axis.

The North Fork occurrence consists of a 2.5 to 14 centimetre lensy quartz vein that follows a 010 degree striking, vertically dipping 15 to 25 centimetres wide shear zone, hosted in green amygda- loidal andesite of the Karmutsen Formation. Amygdules are 0.3 to 2 centimetres and are filled with quartz, epidote and calcite. The quartz vein hosts abundant arsenopyrite and sphalerite with minor chalcopyrite and pyrrhotite. The vein has been traced over 100 metres and is thought to be an extension of the King Midas Trial vein (092L 217). A sample taken over 10 centimetres, 4 metres from the face of the Main adit assayed 217.4 grams per tonne gold, 17.1 grams per tonne silver (Bulletin 27, page 117).

Bibliography
EMPR BULL 20-V; *27, p. 117
EMPR FIELDWORK 1982, p. 290; 1983, p. 219
GSC EC GEOL 1-1947
GSC MAP 4-1974; 255A; 1028A; 1552A
GSC MEM 204; 272, p. 59
GSC OF 9; 170; 463
GSC P 38-5; 40-12; 69-1A; 70-1A; 72-44; 74-8; 79-30
GSC SUM RPT 1929A; 1932A
CIM Trans. Vol. 42, 1939, pp. 225-237; 1948, pp. 78-85; 72, pp. 116-125
N MINER Apr. 1938, pp. 39-45
Carson, D.J.T., (1968): Metallogenic Study of Vancouver Island with emphasis on the Relationship of Plutonic Rocks to Mineral Deposits, Ph.D. Thesis, Carleton University, Ottawa
Stevenson, J.S., (1938): Lode Gold Deposits of the Zeballos Area

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