Primary Ore Minerals Research Articles

Geologic Aspects of Uranium Resources of Japan: ABSTRACT

Uranium minerals are widespread in Japan and are present in various geologic environments. Significant concentrations of the element, however, are limited to dissemination in Tertiary sedimentary rocks of small basins. These sedimentary rocks unconformably overlie Cretaceous to Paleogene granitic rocks. The major sources of the uranium of the deposits are believed to be intergranular material and micas of the underlying granitic rocks. The average uranium content of the major granitic bodies in Japan ranges from 1.5 to 5.7 ppm, but in the vicinity of uranium concentration, can be as high as 11 ppm or more. The uranium in the rocks probably was leached by circulating groundwater containing HCO3- ion. Waters within granitic masses contain up to 8.5 ppb uranium whereas the content in average groundwater is less than 0.05 ppb. The element was transported as uranyl bicarbonate complex and deposited under reducing conditions or was adsorbed in clays and other material. The primary ore minerals of the Tono mine are uraninite and coffinite, but the major form of uranium concentration here seems to be adsorption in montmorillonite and other materials. Recently, interesting and unique deposits of the element, such as a very close association with zeolite and concentration in traps between reverse faults and the basement granite, were found in this mine. End_of_Article - Last_Page 1443------------

Sulfur isotope distribution in sulfides and sulfates from Broken Hill South, New South Wales

Sphalerite and galena are the dominant primary ore minerals found in the Broken Hill orebody of western New South Wales and both occur in minor amounts as supergene suifides, especially at Broken Hill South. Isotope values for the primary sulfides sigma S34 range from 0 to +1.7. Secondary sulfates of the same metals (anglesite and goslarite) follow these figures very closely. The sphalerite and galena of supergene origin are among the highest sigma S34 values yet recorded averaging -43.3 and reaching --51.9. This is considered due to near optimum conditions of freedom of circulation of the downward moving ground waters and thus to maximum availability of the two sulfur isotopes.

The lead-arsenic-sulfide ore deposit of Bacu Locci (Sardinia, Italy)

Arsenopyrite and galena, the principal primary ore minerals of the Bacu Locci mine area, Sardinia (Italy), occur in northwest-striking, steeply southwest-dipping fissure veins in Silurian shales and sericite gneisses, in concordant lodes within the shales, and in stockworks in younger Paleozoic lamprophyres emplaced near the end of Hercynian magmatic activity, prior to the pneumatolytic and hydrothermal processes responsible for mineralization.

Mineralogy and paragensis of the uranium ore, Mi Vida Mine, San Juan County, Utah

Ore at the Mi Vida mine, San Juan County, Utah, consists of uraninite, coffinite, montroseite, a new vanadium oxide mineral, 2 corvusite, and minor secondary minerals. The ore occurs within the matrix of the lower Chinle calcareous sandstones and conglomerates, which are colored dark gray to black by ore minerals and carbonaceous material. The primary ore minerals fill interstices in the sandstone and replace calcite and fossil wood. The replacement process was partly selective: much uraninite replaced carbonaceous debris, calcite, and detrital grains, and the vanadium minerals principally replaced calcite of the sandstone matrix. A few sulfides, pyrite, galena, and greenockite, appeared at the same time or slightly later than the primary ore. Replacement textures are common in the ore, but age relations are not clear in all cases.

Uranium ore controls of the Happy Jack deposit, White Canyon, San Juan County Utah

The major uranium ore control of the Happy Jack uranium deposit of White Canyon, San Juan County, Utah, is a paleostream channel containing sediments of the Shinarump conglomerate. Intrachannel controls include organic matter, lithologic variations, and channel lows.Microscopic studies reveal that uraninite, the primary ore mineral, occurs as cement and as a replacement of organic material. Both uraninite and copper sulfides replace secondary quartz overgrowths. Uraninite is dated as later than the secondary overgrowths and of about the same age as the copper sulfides.

Structural and stratigraphic control of zinc deposits in East Tennessee

The East Tennessee zinc district is situated in the valley regions of the Appalachians. The outstanding structural features of the valley are folds and overthrust faults which have distributed the formations into a series of belts parallel with the long axis of the valley. The same formations, duplicated by thrust faulting, outcrop in each belt. All exposed formations are sedimentary, and most of the zinc occurrences are in the Knox dolomite or the Maynardville limestone. The ore mineral is sphalerite\---|lead free, and no other sulphides except minor amounts of pyrite. At present, all producing mines are in the upper 800 to 1,100 feet of the Knox dolomite, and are situated in Knox and Jefferson Counties. Five mines and two mills are in operation. The 4,000-ton Mascot mill of the American Zinc Company is supplied by ore from the Mascot, Grasselli, Athletic and Jarnigan mines. The 900-ton mill of the Universal Exploration Company is supplied by ore from its Davis mine near Jefferson City. Sphalerite is the sole primary ore mineral, and average tenors of crude ore vary from 2.5 per cent Zn to more than 5.00 per cent Zn.The orebodies are of the replacement and breccia filling type and occur in disturbed breccia zones, which are approximately parallel to the bedding. In detail, however, this long axis may be inclined to the bedding strike. The principal structural features of the ore deposits are jointing, tear faulting, low angle thrust faulting, and bedding plane movement. Associated dolomitization is conspicuous. A major overthrust fault bounds the area in semi-circle. Within this compressive area tear fault zones are the vital structural features controlling the ore.