Dr. Pinckston et Dgw. Smith, MINERALOGY OF THE LAKE ZONE, THOR LAKE RARE METALS DEPOSIT, NWT, CANADA, Canadian journal of earth sciences, 32(4), 1995, pp. 516-532
The Proterozoic (ca. 2.1 Ga) Blatchford Lake suite hosts significant c
oncentrations of rare metals at the core of a peralkaline granite- sye
nite pluton. After emplacement of the Grace Lake Granite and the Thor
Lake Syenite within it, bodies of nepheline syenite, ijolite, and urti
te were intruded beneath the present-day Lake zone. This is the larges
t of five zones of mineralization and lies close to the apex of the Th
or Lake Syenite, a region which was then subjected to albitization, mi
croclinization, and, finally, rare-metal mineralization. The underlyin
g silica-undersaturated rocks contain clots of rare-metal-bearing mine
rals, including cerianite-(Ce), britholite-(Ce), thorite, and calcium
catapleiite, interstitial to nepheline and aegirine. The Lake zone its
elf contains major quantities of Zr (in zircon), Nb (in ferrocolumbite
, pyrochlore group minerals, aeschynite group minerals, and fergusonit
e-(Y)), and Ce (in allanite-(Ce), monazite-(Ce), and bastnasite group
minerals). Lesser amounts of Ta, Y, heavy rare earth elements, U, Th,
and Ga are also present, mainly as minor components of rare-metal-bear
ing minerals. Electron microprobe analyses of the major rare-metal-bea
ring minerals are presented.