The Rar 7 or Kechika Yttrium prospect comprises yttrium and rare earth element mineralization associated with a mafic alkalic igneous complex. It is located in the Rar and Ree claims, in rugged terrain, 13 kilometres northeast of the northern end of Dall Lake and 13 kilometres northwest of Mount Skook Davidson in the Kechika Ranges of the Cassiar Mountains, approximately 146 kilometres east of the community of Dease Lake (Assessment Report 20229, Figures 7, 10b).
The region is bounded to the northeast by the Burnt Rose and Northern Rocky Mountain Trench faults and to the southwest by the Kechika fault. It is characterized by a folded and faulted assemblage of mainly siliciclastic and carbonate rock units ranging in age from Upper Proterozoic to Devonian and belonging to the Cassiar terrane (Bulletin 88; Geological Survey of Canada Maps 42-1962, 1712A, 1713A). The metamorphic grade is up to lower greenschist facies and is probably post-mineralization. The oldest rocks are of the Ingenika Group, overlain by quartzite of the Lower Cambrian Atan Group. These are overlain by a thick, southwest-dipping succession of chlorite-sericite schists and phyllites, marble and dolostone correlative with the Cambro-Ordovician Kechika Group.
Most of the Rar and Ree claims are underlain by Kechika Group phyllites, but within them is a northwest-trending, fault-bounded panel composed of massive grey limestone, dolostone, dark green siliceous tuff, chert and pink and black quartzitic sandstone and argillite (Assessment Reports 15220, 16420, 20895, 22746; Bulletin 88; Fieldwork 1988). Based on fossils in the limestone, this tuff-chert-limestone unit outlines a gently northwest-plunging, overturned antiform and is correlated with the Ordovician-Silurian Sandpile Group (Assessment Report 20895).
The mineralization is hosted by an alkalic intrusive-extrusive igneous complex in the tuff-chert-limestone unit. This complex forms a west-northwest–trending belt of probably cogenetic syenites, trachytic volcanics, carbonatites and diatremes that has been mapped for at least 20 kilometres. The belt ranges in surface width from a few hundred metres to a few kilometres.
The central portion of the belt is dominated by a 350-metre thick, moderately southwest-dipping sequence of moderately to strongly sheared igneous and pyroclastic rocks. This area includes the ‘Ridge zone’ on which the occurrence is centred. The base of the sequence comprises calcareous rocks with minor interbeds of grey aplite; fine- to coarse-grained pyroclastic breccia and graded, laminated layers containing flattened pumice fragments. These rocks were interpreted as calcareous crystal, lapilli and welded tuffs, with related sediments and minor sills.
Above this are white to pink-weathering rocks and phyllite containing quartz, potassium feldspar, apatite, carbonate (dolomite and lesser calcite, magnesite) and sericite. Yttrium minerals are also present in this subunit, apparently related to phosphatic zones several tens of metres long and up to a few metres thick, which are rich in apatite (up to 25 per cent) and to a lesser extent the rare earth phosphates monazite and xenotime. Trenching and sampling across these zones assayed 0.89 per cent yttrium (1.13 per cent yttrium (III) oxide) over 1 metre and high values of dysprosium and gadolinium (Assessment Report 18538). The phosphate minerals also contain a significant amount of thorium; some rock samples assayed up to 0.33 per cent thorium (Bulletin 88, pages 32, 33). Radioactivity was observed to be elevated over some horizons, which might be explained by this mineralogy (Assessment Reports 18538, 20229). The rocks in this subunit are foliated to mylonitic. Field evidence indicates that they are conformable with bedding in the host carbonates; they were tentatively interpreted as trachytic or syenitic tuffs or flows. The assessment reports cited contain extensive geochemical analyses.
Near the top of the sequence are intrusive, dark-green mafic syenites, which are structurally overlain by heterolithic, probably volcanic breccias formed of various sedimentary and igneous fragments (but not mafic syenite). Their tuffaceous matrix varies from pumice-rich to calcareous. Both the fragments and the matrix contain fluorite and pyrite as disseminations, hairline fracture-fillings or as a replacement.
In dolostone and dolomitized limestone, approximately 2 kilometres southeast of the Ridge zone on the Rar 5 claim, there is a diatreme breccia pipe composed of xenoliths of a variety of igneous and sedimentary (mostly quartzite and carbonate) rock types and rare chrome spinel xenocrysts in a pale-green, carbonate-rich tuffisitic matrix. It is cut by a rare earth-bearing fluorite-calcite stockwork, locally with pyrite and minor galena and molybdenite, and by carbonatite dikes (Assessment Reports 15220, 18538, 20229). The value of the rare earth-bearing stockwork material was estimated at $440 per tonne in 1987 (Assessment Report 16420, page 8). The diatreme is extremely deformed and foliated at its contacts. The carbonatites, which also occur in the Ridge zone, are generally fine-grained, with a distinctive orange-brown weathering, and are rich in dolomite or ankerite. They are typically less than 1 metre thick and cut both the alkaline suite and the carbonate hostrocks, so appear to be among the youngest components of the complex.
At the north end of the property (Ree 1 to 4 claims), approximately 8 kilometres northwest of the Ridge zone, a thick section of alkalic igneous rocks is exposed, mostly agglomerate and tuff, trachyte, aplite, chlorite schist and phyllite. The area has similar lithologies to the rest of the property but no significant mineralization is documented in this area (Assessment Reports 20229, 20895).
Work History
In 1986 and 1987, helicopter-supported reconnaissance and detailed geological mapping, prospecting, stream silt sampling and rock geochemical sampling were carried out on the property to evaluate the potential for rare earth elements by Golden Rule Resources Ltd. A total of 125 rock samples and 122 stream silt samples were collected.
During 1988 through 1990, Formosa Resources Corp. completed programs of geological mapping, rock sampling, trenching, a 1.5 line-kilometre ground scintillometer survey and a 0.9 line-kilometre airborne radiometric survey on the area as the Kechika property. In 1989, a program was carried out to define the distribution, grade and continuity of yttrium mineralization at the Rar 7 claim. Four short trenches with a combined length of 35.5 metres were chip sampled from outcrop in the 2237 Ridge zone area.
In 1992, a grid-controlled radiometric survey (17.1 line-kilometres) was carried out over portions of the Rar 1 and Rar 4 claims. After the 1992 program was completed, no further work was conducted in the area and the Rar claims were allowed to lapse. In 2000, Andrew Harman staked the Xeno 1-10 claims over the Rar 5 and Rar 7 occurrences and optioned the claims to Pacific Ridge Exploration Ltd.
In April 2001, Pacific Ridge Exploration Ltd. optioned the property and followed up with further staking. An exploration crew was mobilized to the property in July 2001 to do mapping and sampling, with the intention of prioritizing diamond drill targets. Pacific Ridge also assayed for tantalum, which has been visually noted. Pacific Ridge collected a total of 152 rock samples from several zones enriched in rare earth elements along a strike length of 11 kilometres.
A diatreme breccia stockwork, 3 kilometres southeast of the Rar 7 zone, has been identified as a kimberlite with potential for diamonds. In March 2002, results were reported from a small, 32-kilogram surface sample collected from one location within an approximately 2.5-kilometre long, intermittently exposed, kimberlitic diatreme dike that varies in width from a few metres to greater than 50 metres. The kimberlitic sample produced one cuboid microdiamond fragment with dimensions of 0.38 by 0.30 by 0.25 millimetre (Pacific Ridge Exploration Ltd., Press Release - March 13, 2002).
On the Xeno property in 2003, Pacific Ridge Exploration Ltd. carried out additional surface sampling aimed at characterizing rocks associated with the microdiamond it recovered from an earlier sample. The British Columbia Geological Survey also investigated the area to search for kimberlite indicator minerals (Simandl, in Geological Fieldwork 2003).
In 2010, Paget Minerals Corp. acquired the property from Pembrook Mining Corp. and optioned it to Seymour Ventures Corp.
In 2011, Rare Earth Industries Ltd. (previously Seymour Ventures Corp.) completed rock sampling on the property. Highlights include sample L651834, which assayed 0.3799 weight per cent total rare earth oxides plus yttrium (Assessment Report 32772).
In 2012, Rara Terra Capital Corp. completed a 696.4 line-kilometre airborne radiometric survey on the Xeno claims.
