Tantalum-Cesium Potential of the Pakeagama Lake Pegmatite
The potential for economic tantalum and cesium mineralization in the Pakeagama Lake pegmatite arises out of three main factors: the presence of evolved minerals indicating potential for economic concentration of rare metals, zonation which acts to increase the grade of mineralization by focussing rare metals into specific areas, and significant pegmatite size to justify economic exploitation.
Rare Metal Minerals
“Tantalum oxide assays range from 300 to 700 g/t in large and unbiased grab samples. The Wodgina mine in Australia produces tantalum oxide only and contains 2.07 million tonnes grading 525 g/t tantalum oxide.”1
The evolutionary trend from manganocolumbite into manganotantalite is similar to that expressed by the Tanco pegmatite (Tanco deposit). “Such evolutionary trends indicate a high potential for tantalum-rich zones in the pegmatite system.” 2
“An absence of relatively primitive ferrocolumbite compositions in the Pakeagama Lake pegmatite is also notable and supports the high exploration potential for tantalum.” 2
“It can be seen that the Pakeagama Lake pegmatite has a comparable K/Rb ratio but has higher Cs values than the Big Whopper pegmatite and overlaps the lower ranges for Rb, Cs and K/Rb with the Bernic Lake pegmatite group” 2 (Tanco deposit).
“In the Pakeagama Lake pegmatite, the presence of tantalum-rich minerals such as manganotantalite, ferrotantalite, microlite and ferrotapiolite coupled with pollucite and rubidium concentrations that exceed 1% in potassium feldspar, indicate a high potential for zones rich in tantalum, cesium and rubidium-rich feldspar”. 2
“Pakeagama Lake pegmatite has several mineralogical and chemical characteristics that suggest the presence of a Tanco-type pegmatite system.” 3
“This includes a highly evolved tantalum-rich oxide mineralogy and the presence of the rare and valuable cesium mineral pollucite and widespread phosphate phase montebrasite.” 3
The Pakeagama Lake pegmatite “contains the rare mineral stibiotantalite known elsewhere at only 10 localities on a global scale; stibiotantalite is indicative of extremely-fractionated, Ta-rich rare metal pegmatite systems.” 3
Zonation
The Pakeagama Lake pegmatite has a “strong internal zonation marked by an impressive spodumene+quartz core zone that represents replacement of original petalite.” 3
“Zonation could result in cesium-, rubidium- and tantalum-rich units on surface or at depth.” 3
“The wall zone contains highest Ta and Rb values encountered to date; 1% Rb is the highest bulk content for that mineral yet found in NW Ontario.” 3
Size
“Second largest complex-type pegmatite system in Ontario: 250 m strike-length; open to SE and NW”. 3
“Width = 10 to 70 m: pegmatite widens at its NW and SE outcrop limits” 3
An “extensive Li-Cs anomaly occurs in the granite host-rocks adjacent to the SW contact of the Pakeagama Lake pegmatite and is marked by holmquistite, a key exploration indicator mineral of Li-rich pegmatites. Distribution of the holmquistite was traced for a minimum distance of 120 meters normal to the pegmatite which is the most significant variation yet described in the literature; in granitic host-rocks holmquistite is typically quite rare and usually developed only within a few cms of a Li-rich rare metal pegmatite. ” 3
“The occurrence of this aplite unit with such evolved tantalum-rich oxide minerals, suggests a continuation of the rare-metal pegmatite system at least 400 m to the southeast beyond the outcrop containing the spodumene-quartz core unit.” 2
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1 Dr. Fred Breaks, Ontario Geological Survey, personal communication.
2 Breaks, F. W., Tindle, A. G., and Smith, S. R., 1999. Rare-metal Mineralization Associated with the Berens River-Sachigo Subprovincial Boundary, Northwestern Ontario: Discovery of a New Zone of Complex-Type, Petalite Subtype Pegmatite and Implications for Future Exploration, Ontario Misc. Paper 169, pp. 168-182.
3 Breaks, F. W., 1999. Summary of Geology, Mineralogy and Geochemical Work on Pakeagama Lake Rare-metal Pegmatite, North Spirit Lake Area, NW Ontario. Unpublished Handout, 13 pages.
Source: Houston Lake Mining Inc.
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Comment: From the above, it should be obvious that the focus is on cesium and tantalum - and that the potential for a discovery is very real!
DRT |
