The American Flag occurrence is part of the Iron Range showings which are located near the crest of the ridge that is west of and parallel to the Goat River. The location is centred on an early 1900s shaft on the American Flag claim, about 2 kilometres north of the headwaters of Crackerjack Creek.
Regionally, the area is underlain by the peri-cratonic Middle Proterozoic Purcell Supergroup, a thick succession of siliciclastic and lesser carbonate rocks. The Purcell Supergroup is well known for hosting a number of significant deposits that include the Sullivan sedimentary-exhalative lead-zinc deposit (082FNE052) and the Troy copper-silver deposit in Montana.
These occurrences are closely associated with the Iron Range fault and the strata here forms part of the core of the Goat River anticline. They comprise a belt of iron oxide mineralization up to 200 hundred metres wide with an intermittent strike length of at least 20 kilometres.
Mineralization occurs within the Middle Aldridge Formation along the north trending, subvertical Iron Range fault zone. The Aldridge Formation in the vicinity of the northern showings consists of well bedded quartzofeldspathic wacke and laminated siltstone, which develop a phyllitic sericite foliation near the fault. Locally, sericite alteration extends preferentially along specific bedding horizons. The gabbro dikes and/or sills in the area, which belong to the Middle Proterozoic Moyie intrusions, are preferentially mineralized.
Mineralization consists of massive to disseminated hematite, locally with magnetite, in steeply dipping, 0.3-0.6 metre wide veins, broader stockworks of thin veinlets, breccia matrix and disseminated grains. Gabbro hostrocks are strongly albitized and the siltstones exhibit sericitic +/- silicic alteration. Sulphide mineralization is sparse except in the area north of the American Flag occurrence where pyrite clots occur within a foliated mafic dike. The zone of mineralization pinches and swells along strike from narrow (0.5 metre wide) veins within sheared rock, to a broad (100 metres or more) zone of multiple veining and alteration. Depth and downdip extension of this system is unknown.
A sample taken across 3 metres of the American Flag shaft contained 55 per cent metallic iron (Geological Survey of Canada, Economic Geology Series 3, page 132).
Crosscutting relationships suggest multiple phases of hydrothermal fluids injected into the fault zone. Early quartz veins are commonly brecciated, with fragments enclosed in a hematite matrix. Early albitization is crosscut by hematite veining and angular albitized clasts float in later hematite veining. Later stage white and colourless quartz veinlets commonly crosscut both albite alteration and hematite veining.
The original Iron Range prospect was discovered and staked in 1897 along an extensive belt of iron oxide showings. In 1939, the Consolidated Mining and Smelting Company of Canada Ltd.—with its parent company, Canadian Pacific Railroad (CPR)—acquired many of the historic Crown grants on the northern part of Iron Range Mountain. The claims were evaluated by CM&S (later known as Cominco Ltd., then Teck Cominco Ltd. and now Teck Ltd.), to assess the potential for a large iron resource. In 1957, Cominco Ltd. completed an extensive trenching program exposing the Iron Range structure and mineralization over more than 4 kilometres strike length. Most of the Iron Range Crown grants were held by Cominco–CPR until 1999, when they were reverted after being held privately for over 100 years. Eagle Plains Resources Limited restaked the original Crown grants on the day they lapsed.
Initial fieldwork by Eagle Plains consisted of a property-scale wide-spaced soil geochemical survey, rock sampling and geological mapping. The work identified iron oxide copper-gold indicators associated with the main Iron Range structure in the area of the historic trenches and along the projections of structural splays. Fieldwork also identified Sedex-style geochemical anomalies along the surface trace of the Lower to Middle Aldridge Contact, the time-equivalent to the Sullivan silver-lead-zinc deposit.
In 2005, Eagle Plains completed four diamond drill holes to test the Lower to Middle Aldridge Contact. All of the holes intersected "Sullivan smoke", including albite and tourmalinite alteration, fragmentals and disseminated and locally laminated and/or bedded sulphides at or near Sullivan time. One of the holes, IR05-003, returned values of 3.83 grams per tonne gold and 46 grams per tonne silver over 2 metres in a fault breccia believed to be a splay from the main Iron Range fault system. Eagle Plains included a high-resolution versatile time domain electromagnetic geophysical survey, detailed soil sampling and trenching (www.eagleplains.bc.ca).
From 2007 to 2009, the exploration focus shifted to evaluating the main Iron Range faults in the area of the historic Cominco trenches. The 2008 drilling by Eagle Plains intersected 51.52 grams per tonne gold and 2.39 grams per tonne silver over 7 metres in a drillhole collared adjacent to the historic O-Ray iron oxide showing. Follow-up drilling by option partner Swift Resources in 2009 intersected 1 metre of 22.5 grams per tonne gold in a drillhole collared in the same area (www.eagleplains.bc.ca).
In September 2010, a two-hole diamond drilling program was initiated and designed to test a potential Sedex target. Hole No. 2 intersected a significant interval located at or near the Sullivan Horizon, containing pervasive tourmaline and albite-altered sediments interlayered with discrete conformable bands of pyrite, pyrrhotite (iron) and chalcopyrite (copper) sulphides (www.eagleplains.bc.ca).
In 2011, Providence Resources Corp. and Eagle Plains Resources Ltd. completed a systematic compilation and analysis of historical soil geochemistry data on the Iron Range property. The analysis confirmed that the property displays an anomalously high background metal endowment and demonstrated that the entire property is prospective for gold mineralization in addition to the traditionally explored Sullivan-style lead-zinc mineralization (V STOCKWATCH, January 17, 2012).
In 2012, a six-week 2411-metre diamond drill program was conducted on the Iron Range property. Highlights included Drillhole IR12-035, which intercepted a 28-metre alteration zone containing elevated gold, silver, zinc, lead and arsenic associated with brittle northeast-trending faults. The best intercept consisted of 7 metres grading 0.19 gram per tonne gold and 1.29 grams per tonne silver (V STOCKWATCH, July 30, 2012).