UNITED STATES DEPARTMENT OF THE INTERIOR Oscar L. Chapman, Secretary GEOLOGICAL SURVEY W. E. Wrather, Director GEOLOGICAL, SURVEY CIRCULAR PRIELIMINARY SUMMARY FEVIEW OF THORIUM-BEARING MINERAL OCC-NCES IN ALASKA By Robert G. Bab and Welmuth Wedow, Jr. Thw report wncarna work done on behalf of the U. 8.Atomic Energy Cdonand ia published with the permhion of the Commineion Wmd-hgbn, D. C., 1963 Free on amliation to the Geologid Survey, Wlahinotpn 26, D. C. PRELIMINARY S-Y Rl3VIEW OF THORIUM-BEARING MINERAL OCCURRENCES IN ALASKA CONTENTS Fage Fage Abstract..................................... 1 Discussion of data--Continued Introduction.................................. 1 Thorium occurrences worthy of Discussion of data.. .......................... 2 possible further study--Continued Thorium-bearing minerals ............... 2 Buckland-Kiwalik district.. ......... 5 Thorium occurrences worthy of Clem Mountain area.. ......... 5 possible further study .................. 3 Hunter Creek-Connolly Creek- Salmon Bay area ................... 3 Fairhaven Creek area.. ...... 5 Tobin Creek-Big Creek area.. ....... 4 Granite Mountain area. ........ 5 Manley Hot Springs district. ......... 4 Darby Mountains district ........... 5 Eurekaarea, ................. 4 Tubutulik River area.. ........ 5 Tofty tin belt.. ................ 4 Golovin Bay area.. ........... 5 Hot Springs Dome area.. ....... 4 Cape Mountain area.. .............. 6 Long area......,.................. 4 Conclusions.................................. 6 Nixon Fork area. ................... 4 Literature cited.. ............................ 6 ILLUSTRATICN Fage Flate 1. Map of Alaska showing location of thorium occurrences.. ..........................Inside back cover TABLES Fage Table 1. General descriptio? of thorium-bearing minerals belonging to species that are found in Alaska ..... 2 2. Cccurrences of thorium-bearing minerals in Alaska,. .......................................... 8 ABSTRACT The remaining occurrences of thorium-bearing minerals in Alaska are limited to placer deposits and Thorium-bearing minerals are known at 47 lo- disseminations of accessory minerals in granitic rocks. calities in Alaska. At these localities the thorium In most of these occurrences the thorium-bearing occurs as a major constituent or in minor amounts as minerals occur in only trace amounts and consequently an impurity in one or more of the following 12 minerals: warrant little further consideration. More data are allanite, columbite, ellsworthite, eschynite, gummite, needed to determine the possibilities of byproduct monazite, orangite, mrisite, thorianite, thorite, recovery of thorium-bearing minerals from several xenotime, and zircon. In addition other minerals, such of the gold and tin placers. as biotite and sphene, are rackioactive arld may contain thorium. Several unidentified niobate minerals with uranium or uranium and thorium as major constituents INTRODUCTION have been recognized at some localities. Before the beginning of the Trace Elements The distribution, by type of deposit, of the 47 program of the Geological Survey in 1944, little was thorium occurrences is as follows: lode, 3; lode and known about the occurrence of thorium-bearing placer, I; granitic rock, 3; granitic rock and related minerals in Alaska. Mertie (1925, p. 26~)lreported placer, 14; and placer, 26. Of the four lode occur - the presence of monazite in the placers of Big Creek rences only the radioactive veins at Salmon Bay in in the Chandalar district north of Fort Yukon. southeastern Alaska and the contact metamorphic Eschynite, xenotime, and monazite were identified in deposit in the Nixon Fork area of central Alaska the tin-bearing placers of the Manley Hot Springs warrant further consideration as possible commercial district west of Fairbanks (Mertie and Waters, 1934, sources, although insufficient data are available to pp. 229, 239-240). Durinq World War I1 determine whether these two deposits have such possibilities. 'see pge 11 for list of liccrature cited. 1 J. H. Skidmore (1944) reported to the Union Mines DISCUSSION CF DATA Development Corp. on the radioactivity of various Alaskan placers; he noted that concentrates from mining Thorium-bearing minerals operations on Sweepstakes Creek in the eastern Seward Peninsula were especially radioactive, Later work Twelve minerals containing thorium, either (Gault and others, 1946; Killeen and White, 1950) by as a major constituent or in minor amounts as the Geological Survey showed that the chief radioactive an impurity, are known in Alaska, These mineral in the concentrates from Sweepstakes Creek minerals are allanite, columbite, ellsworthite, and other nearby streams is uranothorianite. eschynite, gummite, monazite, orangite, par isite, thorianite, thorite, xenotime, and zircon. For Considerable information has been collected on the convenience of the reader, brief general the occurrence of thorium-bearing minerals during descriptions of these minerals, summarized from the course of the Survey's reconnaissance investiga- Ford (1932), Frondel and Fleischer (1950), tions for uranium in Alaska. All available data on George (1949), and Falache and others (1951) are thorium-bearing minerals in Alaska are now being given in table 1. It should be emphasized that compiled, and the purpose of this report is to present these mineral descriptions, particularly the a preliminary surr,mary of the data compiled to date. thorium percentages, refer to mineral occurrences The spectrographic and chemical analyses, and most outside Alaska; few data are available on the of the radiometric analyses and mineral identifications thorium-bearing minerals in Alaska beyond the used in this report, were made in the Trace Elements fact that their presence at a particular locality has Section Washington Laboratory; a few of the radiomet- been noted. In addition, other minerals, such as ric analyses and mineral identifications were made biotite and sphene, are radioactive and may contain by members of the Survey's Alaskan 'I'race Elements thorium. Several unidentified niobate minerals with Unit. This work was done on behalf of the Division of uranium or uranium and thorium as major constituents Raw Materials of the U. S. Atomic Energy Comrr~ission. have been recognized at some localities. Table 1.--General description of thorium-bearing minerals belonging to species that are found in Alaska Thorium Mineral Chemical composition (percent) Description Hydrous silicate of as much as 3 Color: brown to black. aluminum, calcium, Luster: resinous to submetallic. and the cerium metals Fracture: uneven to subconchoidal. Habit: tabular, also Long and slender, also masslve. Specific gravity: 2.7-4.2. Nlobate of iroq and Color: black, grayish and brownish black. manganese. Luster: submetalllc to subresinous. Fracture: subconchoidal to uneven. Habit: short prismatic grains. Specific gravity: 5.2-7.9. Complex hydrous oxides Color: amber yellow to dark brown. of niobium, tantalum, Luster: adamantine. sodium, calcium, with Fracture: subconchoidal to splintery, hydroxyl and fluorine uneven. may contain as much Habit: rounded grains, also massive. as 17 percent uranium Specific gravity: 3.8-4.2. Complex oxide of nlc- Color: brownish yellow to black. bium, tantalum, and Luster: submetallic to resinous, nearly the rare earths with dull. varying amounts of Fracture: small conchoidal. thorium and uranium. Habit: mostly masslve, also prismatic. Specific gravity: 4.9-5.2. Uranium with minor much as 22 Color: orange, yellow, orange yellow. amounts of thorium, Luster: dull to greasy. lead, and hydroxyl. Fracture: uneven to subconchoidal. Habit: massive, dense, also in rounded or flattened masses or crusts. Speclflc gravity: 3.9-6.4. 3are-earth phosphate CoLol: yellowish or reddish brown, golden with some thoria and yellow. silica. Luster: resinous. Fracture: concholdal to uneven. Habit: small, often flattened grains. Specific gravity: 4.9-5.3. Table 1.--General description of thorium-bearing minerals belonging to species that are found in Alaska--Continued Thorium Mineral Chemical composition (percent) Description Oranglte------ Thorium silicate, a 63 Color: bright orang& or orange yellow. variety of thorite. Luster: vltreous to glassy when fresh, dull to greasy when altered. Fracture: conchoidal. Hablt: square prismatic crystals, also massive. Specific gravity: 4.1-6.3. Papisite------ Fluocarbonate of calcium 0-? Color: brownish yellow, brown, wax :ellow. and the cerium group. Luster: vitreous to resinous. Fracture: subconchoidal to splintery. Habit: crystals small and slender, pyramidal or prismatic. Specific gravity: 4.4. Thorianite---- Oxide of thorium and 34-63 Color: black, brownish,or grayish. uranium. Luster: submetallic to dull or g~asy. Fracture: uneven to subconchoidal. Habit: cubic. SpBcific gravity: 9.3. Thorite------- Thorium silicate-------- 25-63 Color: commonly black, brown, less commonly green. Luster: vitreous to glassy when fresh, dull to greasy when altered. Fracture: conchoidal. Habit: square prismatic crystals, also massive. Specific gravity: 4.1-6.4. Xenotime------ Essentially yttrium 0.4-3.3 Color: shades of brown, yellow, green, phosphate. grayish white, pink. Luster: resinous to dull or earthy. Fracture: uneven and splinter7 Habit: long or short prismatic crystals. Specific gravity: 4.5-4.6. Zircon-------- Zirconium silicate, Usually low, Color: various shades of red, brown, usually with some ferric but as much and gray when thorium bearing. oxide and often some as 13.1 Luster: usually