This and several other nearby uranium-thorium-REE deposits (DE015, DE016, and DE18 to DE031) are spatially and genetically related to a stock of Jurassic, peralkaline granite about 2 miles in outcrop diameter centered on Bokan Mountain. It commonly is referred to as the Bokan Mountain peralkaline granite or Bokan Mountain complex. The intrusion and its deposits have been mapped in detail several times using slightly different subdivisions of the granite (MacKevett, 1963; Thompson and others, 1980, 1982; Saint-Andre and others, 1983; Gehrels, 1992; Thompson, 1997). This description largely follows Gehrels' (1992) map units. The intrusion is a ring-dike complex with an outer border zone up to 14 meters thick of pegmatite and aplite; a nearly complete intermediate zone of aegirine granite porphyry, 15 to 180 meters thick; and a core of several varieties of riebeckite granite porphyry. It has been dated by several methods at 151 Ma to 191 Ma (Lanphere and others, 1964; Saint-Andre and others, 1983; Armstrong, 1985; Gehrels, 1992; Thompson, 1997). The peralkaline granite mainly intrudes a regionally extensive body of Silurian or Ordovician quartz monzonite, granite, and quartz diorite that makes up much of the southeast tip of Prince of Wales Island. The south and west sides of the peralkaline granite are in contact with a band up to about 3,000 feet wide of shale and argillite of the Silurian or Ordovician Descon Formation. The Bokan Mountain complex and surrounding Paleozoic rocks are cut by numerous pegmatite, andesite, dacite, and aplite dikes. The dikes are genetically related to the complex and commonly are associated with the uranium, thorium, and REE deposits. The deposits are marked by intense albitization, pervasive or fracture-controlled chloritization, calcite-fluorite replacement of aegirine, and hematitization. Three types of U-Th-REE deposits occur in the Bokan Mountain complex: 1) irregular cylindrical pipes; 2) steep, shear-zone-related pods or lenses ('veins'); and 3) quartz veins.

The Sunday Lake prospect has been explored by two short trenches and a small pit (Warner and Barker, 1989), and three holes were drilled in the fall of 2009 (Ucore Uranium, 2009b). The deposit is controlled by steeply dipping, north-northwest-trending shear zones and fractures which can be traced for about 300 feet in riebeckite granite. Allanite is locally abundant. Where exposed, the deposit is 3 to 7 feet thick and consists of highly radioactive, mottled, iron- and manganese-stained gouge and crushed rock.

In 2009, Ucore Uranium announced that samples taken at or near this prospect contained a significant content of heavy and light rare-earth elements (Ucore Uranium, 2009a). The analyses of the samples were reported as the light rare-earth-element oxides or LREO (lanthanum, cerium, praseodymium, neodymium, and samarium) and the heavy rare-earth-element oxides or HREO (europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and yttrium); together they are termed the TREO, the total rare-earth-element oxides. The two samples contained 7.19 and 0.37 percent HREO and 2.39 and 15.17 percent HREO. The analyses indicate that nearly all of the rare-earth-element oxides are the heavy rare-earth-element oxides. By early fall of 2009, two of the three Ucore holes cut high grade intercepts of rare-element minerals (Ucore Uranium, 2009b). The notable intercepts were 4.80 meters with 0.10 percent LREO and 1.93 percent HREO, 0.80 meters with 0.13 percent LREO and 3.82 percent HREO, and 1.72 meters with 0.07 percent LREO and 0.81 percent HREO. In other words, 92 to 97 percent of the rare-earth-element oxides were the heavy rare-earth-element oxides.