Uraniferous alaskitic granites with special reference to the Damara Orogenic Belt

International Nuclear Information System (INIS)

Toens, P.D.; Corner, B.

1980-10-01

The control and patterns of uranium mineralisation in the alaskitic granites of the Damara Orogenic Belt are discussed. The polyphase Damara metamorphism produced high-grade metamorphic assemblages, migmatites and syn-, late-, and post-tectonic anatectic granites through reactivation of the basement and overlying Damara rocks. During anatexis the incompatible elements, particularly the uranium derived from these formations, were incorporated into the melts which then rose, in an attempt to attain gravitational equilibrium, by varying distances depending on the depth of origin of the melts, on their water content and on the availability of tensional environments. Fractional crystallisation during ascent and increased water content concentrated the uranium into residual melts which finally crystallised as alaskitic pegmatitic granite. Structural episodes played an important part in the emplacement of the uraniferous granites and the presence of marble bands was an important factor in not only providing a structural trap for the alaskitic melts and associated uranium-rich volatiles, but also by leading to the boiling of the magma and the subsequent deposition of uranium. The present-day level of erosion is considered to be an important factor contributing to the preservation of many of the uraniferous granite bodies. In addition it is suggested that secondary enrichment occurring above the water-table in the prevailing desert environment is an important criterion in enriching the tenor of mineralisation to ore grades. The exploration techniques necessary for the location of uraniferous granite bodies are briefly outlined [af

Preliminary results on the petrology and fluid inclusions of the Rossing uraniferous alaskites

International Nuclear Information System (INIS)

Cuney, M.

1980-01-01

Petrography, radioactivity distribution and fluid inclusions have been studied in three samples of the Rossing alaskites from the S.H. anomaly outside of the Rossing deposit. After the crystallization of the alaskitic magma which involved oligoclase, biotite, orthoclase and quartz, a deuteric alteration produced a quartz, microcline, albite, muscovite, calcite plus minus chlorite mineral association similar to those observed in several French uraniferous granites. Uranium redistribution occurred during this alteration. From fluid inclusions data, the pressure at the time of the intrusion is estimated to have been at least 6kbar for a temperature of 625 degrees Celsius. Reaction of the magma with the marbles of the Rossing formation led to the boiling of the magma by an increase in the CO 2 partial pressure as well as to its crystallization. Immiscibility between a dense saline (more than 30 per cent NaCl) and CO 2 -rich fluid is proposed to have occurred simultaneously or after the fluid oversaturation of the magma. Part of uraninite is formed at the magmatic stage, another part crystallized from the magmatic fluids in the biotite-rich selvages of the alaskites or in the uraninite-fluorite veins. Uraninite crystallization appears to be mainly controlled by the oxygen fugacity prevailing in the magma and in the surrounding rocks

Occurrence of parsonite, a secondary uranium mineral, in alaskite of the Wheeler Creek pluton, Alaska

International Nuclear Information System (INIS)

Miller, T.P.; Johnson, B.

1978-01-01

Reconnaissance investigations in the Purcell Mountains of westcentral Alaska in 1977 revealed the presence of parsonite, a hydrous phosphate of lead and uranium with the formula Pb 2 UO 2 (PO 4 ) 2 2H 2 O. This is the first reported occurrence of parsonite in Alaska. The parsonite occurs as a soft, yellow to chocolate brown coating closely associated with green muscovite on fracture surfaces in a shear zone in alaskite of the Wheeler Creek pluton. Thin magnetite veinlets are also present. The identification of parsonite was confirmed by x-ray diffraction. Delayed neutron analysis were run on samples of the Alaskite

Evaluation of uranium anomalies in the Goodman-Dunbar area, northeastern Wisconsin

International Nuclear Information System (INIS)

Mathews, G.W.; Blackburn, W.H.

1982-01-01

Based on this investigation, the Goodman-Dunbar area is considered not to be favorable for the occurrence of uranium deposits of economic potential. Whether one adopts an anatectic or igneous intrusive model for the pegmatites, the area does not meet NURE favorability criteria guidelines because: (1) The apparent average grade of the alaskites will not meet or exceed the 100-ppM minimum cutoff grade; (2) Even if the grade requirements were met, the alaskite is not extensive enough to provide a sufficient volume of endowed rock. It is reasonable to assume that similar alaskites may exist west of this study area, beneath the glacial drift. If the uranium is located in interstitial sites and (or) along fractures, as postulated in this investigation, then it would be readily available for leaching into local surface- and ground-water regimes. This alaskite and other possible alaskites are probably the cause of local stream-water anomalies. The contrasting uranium contents of the alaskites and Dunbar Gneiss also are probable causes for anomalous airborne measurements. The area near Dunbar, Wisconsin, warrents no further study in terms of uranium potential. 4 figures, 2 tables

Magma mixing in granitic rocks of the central Sierra Nevada, California

Science.gov (United States)

Reid, John B.; Evans, Owen C.; Fates, Dailey G.

1983-12-01

The El Capitan alaskite exposed in the North American Wall, Yosemite National Park, was intruded by two sets of mafic dikes that interacted thermally and chemically with the host alaskite. Comparisons of petrographic and compositional data for these dikes and alaskite with published data for Sierra Nevada plutons lead us to suggest that mafic magmas were important in the generation of the Sierra Nevada batholith. Specifically, we conclude that: (1) intrusion of mafic magmas in the lower crust caused partial melting and generation of alaskite (rhyolitic) magmas; (2) interaction between the mafic and felsic magmas lead to the observed linear variation diagrams for major elements; (3) most mafic inclusions in Sierra Nevada plutons represent chilled pillows of mafic magmas, related by fractional crystallization and granitoid assimilation, that dissolve into their felsic host and contaminate it to intermediate (granodioritic) compositions; (4) vesiculation of hydrous mafic magma upon chilling may allow buoyant mafic inclusions and their disaggregation products to collect beneath a pluton's domed ceiling causing the zoning (mafic margins-to-felsic core) that these plutons exhibit.

Rb-Sr geochronolgy of the Jervois Range area in the eastern part of the Arunta Block, NT

International Nuclear Information System (INIS)

Black, L.P.

1980-01-01

New Rb-Sr isotopic data are presented for the Jervois Range area in the eastern part of the Arunta Block. The post-metamorphic Jinka and Jervois Granites yield an age of about 1750 m.y. An alaskitic granite is dated at about 1460 m.y. Pegmatite formation occurred about 1660 m.y. ago. Mineral ages are generally younger than total-rock ages, but no values significantly less than that of the alaskitic granite were found. This means that the Alice Springs Orogeny, which extensively reset large areas of the Arunta Block to the west, did not effect the Jervois area. In this and other geochronological comparisons, the Jervois area seems more akin to the rocks of the Tennant Creek Block, 400 km to the northwest, than to those of the Arunta Block

Results of a paleomagnetic survey undertaken in the Damara mobile belt, South West Africa, with special reference to the magnetisation of the uraniferous pegmatitic granites

International Nuclear Information System (INIS)

Corner, B.; Henthorn, D.I.

1978-10-01

A project study, undertaken by the Geology Division of the AEB, on the correlation between airborne magnetic and radiometric data covering a portion of the Damara Mobile Belt in South West Africa, has revealed that all the known occurrences of uranium in late- to post-tectonic leucogranite (alaskite) of the Damara orogeny are associated with negative geomagnetic anomalies. Although the uranium occurrences themselves do not display marked geomagnetic anomalies, their immediate geological environment is characterised by the negative anomalies, which are semi-regional in extent. To investigate the origin of these anomalies, the Atomic Energy Board and the Geological Survey of South Africa undertook a palaeomagnetic study of the area. Oriented cores were taken from 31 sites in the mobile belt, 18 of which were selected within the negative magnetic zones, mostly in close association with known uraniferous alaskitic granites. Palaeomagnetic evidence suggests that the negative geomagnetic anomalies are associated with a remanent magnetisation, resulting from the Damara orogenic event, whose direction is removed from the earth's present field and which has affected rocks of the Nosib Group. Absence of this stable remanent direction in rocks stratigraphically overlying the Nosib Group accounts for the distinctive geomagnetic signature, in the form of negative anomalies, of the Nosib Group. It is this signature which can be used in airborne surveys to identify rocks of the Nosib Group outcropping, or of shallow suboutcrop, in anticlinal or dome-like structures. Since the uraniferous alaskites are mostly confined stratigraphically to the Nosib Group, the negative geomagnetic anomalies form an important prospecting criterion as they may be used to delineate target areas for further exploration in areas covered by sand, scree and duricrust deposits [af

Uranium occurrence at Sao Teodosio farm, Currais Novos, Rio Grande do Norte, Brazil

International Nuclear Information System (INIS)

Favali, J.C.; Leal, J.R.L.V.

1974-01-01

The areas of certain radiometric anomalies discovered in Serido geosyncline were selected for intensive study because of the similarity of the geology to that of known uranium deposits in other parts of the world. The uranium mineralization at Sao Teodosio farm, near Currais Novos, RN, on the Serrinha anticline axis, occurs in alaskite similar to that at Rossing in Southwest Africa. The Rossing deposit is the best example of the model proposed by Armstrong (1974) as 'porphyry' uranium deposits. That uranium deposit presents low grade of uranium content, about 0,030% U 3 O 8 and hundred thousands tons of uranium oxide. At Sao Teodosio occurs 550 m.y. alaskitic pegmatitic granite and garnet-quartz-biotite-schists of Serido formation, Upper Precambrian. These older rocks are cut by diabases dykes of Upper Terciary age. Uranium mineralization is associated with pegmatitic granite bodies similar to dykes and sills. The most common uranium minerals are: uraninite, meta-autunite and uranophane. Oligoclase, microline and quartz are the most frequent minerals. Acessory minerals are magnetite, titanite and zircon. Uranium oxide content at Sao Teodosio is 0,023% and average thickness is 2,80 m [pt

Uraniferous leukogranites from the Namaqualand metamorphic complex: Pt. 1

International Nuclear Information System (INIS)

Robb, L.J.

1986-01-01

A number of small leucogranite or alaskite bodies intrude the Modderfontein augen gneiss on the farm Nooitgedacht, south-west of Springbok. These intrusions, correlated with the Kweekfontein Granite of the Spektakel Suite, are anomalously enriched in uranium and thorium, and certain of them have been assessed as potential low-grade deposits. The leucogranites are highly differentiated and are characterized by a pervasive alteration which has sericitized the feldspars and propylitized the biotite. Alteration was probably of a deuteric nature, associated with the late magmatic-early subsolidus stages, and was neither a low-temperature, open-system event, nor was it related to regional retrogressive metamorphism. The leucogranite bodies have I-type characteristics and appear to have been derived by partial melting of lower crustal material. A subset of eight leucogranites were analysed by neutron activation analysis for the rare-earth elements. Typical depleted lower crust is ruled out as a source, however, because of the necessity to markedly enrich the leucogranite magma in elements such as K, Rb, U, and Th. Scatter in Rb-Sr isotope ratios for the Nooitgedacht alaskites indicates that the source may have been heterogeneous and/or anomalously fertile in certain selected elements. In addition, a component of scatter was probably introduced during the extensive alteration of the rocks

The Serra do Carambei Granite - PR and the uraniferous anomalism

International Nuclear Information System (INIS)

Pinto-Coelho, C.V.

1986-01-01

The Serra do Carambei Granite forms a pluton relatively homogeneous, covering about 33 km 2 , cropping out as an elongate retangular body trending NE-SW, being emplaced in the Cunhaporanga Granitoid Complex. Its characteristics indicates a kind of hololeucocratic granite, equigranular, medium to coarse-grained, consisting predominantly of microperthitic alkali-feldspar, quartz and a small amount of biotite (less than 1%), thus being classified as an alaskite. Chemical data allows a classification in the group of granite with high contents of silica (74-76% Wt. SiO 2 ), dominantly alkaline chemism and hypersolvus character, derived from a parental magma under saturated in water with distinguished features of granitoids from the magnetite series and types I and A granites. The pluton shows important chemical variations due to weathering processes. However detailed chemical studies reveal the presence of anomalous concentrations of trace elements such as U, Sn, Nb, Y, Zr, the Serra do Carambei Granite lacks economically important mineralizations because of the absence of well-developed tardi/pos-magmatic processes that could concentrate them. The SW side of the granite is cut by leucocratic rhyolite dykes that show some radiometric anomalies. These rocks, which are highly diferentiated, were emplaced contemporaneously to the Serra do Carambei Granite. Although petrographic and chronological similarities are found between the uraniferous alaskite of Roessing (Namibia) and the Serra do Carambei Granite anyhow it was not possible to establish any lateral continuity with the uranifeous Pan-African Province. (Author) [pt

Uranium deposits in granitic rocks

International Nuclear Information System (INIS)

Nishimori, R.K.; Ragland, P.C.; Rogers, J.J.W.; Greenberg, J.K.

1977-01-01

This report is a review of published data bearing on the geology and origin of uranium deposits in granitic, pegmatitic and migmatitic rocks with the aim of assisting in the development of predictive criteria for the search for similar deposits in the U.S. Efforts were concentrated on the so-called ''porphyry'' uranium deposits. Two types of uranium deposits are primarily considered: deposits in pegmatites and alaskites in gneiss terrains, and disseminations of uranium in high-level granites. In Chapter 1 of this report, the general data on the distribution of uranium in igneous and metamorphic rocks are reviewed. Chapter 2 contains some comments on the classification of uranium deposits associated with igneous rocks and a summary of the main features of the geology of uranium deposits in granites. General concepts of the behavior of uranium in granites during crustal evolution are reviewed in Chapter 3. Also included is a discussion of the relationship of uranium mineralization in granites to the general evolution of mobile belts, plus the influence of magmatic and post-magmatic processes on the distribution of uranium in igneous rocks and related ore deposits. Chapter 4 relates the results of experimental studies on the crystallization of granites to some of the geologic features of uranium deposits in pegmatites and alaskites in high-grade metamorphic terrains. Potential or favorable areas for igneous uranium deposits in the U.S.A. are delineated in Chapter 5. Data on the geology of specific uranium deposits in granitic rocks are contained in Appendix 1. A compilation of igneous rock formations containing greater than 10 ppM uranium is included in Appendix 2. Appendix 3 is a report on the results of a visit to the Roessing area. Appendix 4 is a report on a field excursion to eastern Canada

Airborne radiometric anomalies caused by late kinematic granite rocks in the Molson Lake-Red Sucker Lake area, east-central Manitoba

International Nuclear Information System (INIS)

Weber, W.; Schledewitz, D.C.P.; Soonawala, N.M.

1982-01-01

Geological mapping with simultaneous ground gamma ray spectrometer surveys in an area with a chain of airborne radiometric anomalies of greater than 2 ppm eU indicate uranium enrichment in late kinematic pink leucogranitic rocks including granites, alaskites, and syenites which form dykes, stocks and small plutons in a batholithic tonalite - granodiorite complex. Field geolocial evidence suggests that the potassium-rich rocks were formed by hydrothermal solutions and that at least some of them are metasomatic replacement bodies. Results of geophysical grid survey over a pronounced anomaly indicate that it is caused by a significant volume of leucogranitic rocks with an unusually high background concentration of uranium averaging 25 ppm eU. The uranium seems to be associated with hematite which coats mineral grains and fills small fractures

Characteristics and its uranium metallogenic potential of the granite belt between Bange and Jiali county, tibet

International Nuclear Information System (INIS)

Zhao Baoguang; Wang Qin; Liu Zhipeng; Chen Yuliang; Xu Wei

2012-01-01

The granite belt between Bange and Jiali county is a composite batholith which intruded at multistage, it con- trolled by several groups of the fault system, the alteration is developed, with the alaskite, aplite, pegmatitic vein intruded, it is type Ⅰ in the beginning of forming, and change to type S in the late time. There is a large of geochemical anomalies of uranium (U>6.8 X 10 -6 ) in Gulu town and Sangba village, of which middle of the granite belt and Bianba county of which east of the granite belt, that anomalies area have 1200 km 2 , 800 km”2 and 1500 km 2 . All the anomalies is considered that its forming relate to batholith and its external contact, so it shows that it has favorite geological conditions for granite type uranium metallogenesis. (authors)

Petrology, geochemistry and source characteristics of the Burpala alkaline massif, North Baikal

Directory of Open Access Journals (Sweden)

N.V. Vladykin

2017-07-01

Full Text Available The Burpala alkaline massif contains rocks with more than 50 minerals rich in Zr, Nb, Ti, Th, Be and rare earth elements (REE. The rocks vary in composition from shonkinite, melanocratic syenite, nepheline and alkali syenites to alaskite and alkali granite and contain up to 10% LILE and HSFE, 3.6% of REE and varying amounts of other trace elements (4% Zr, 0.5% Y, 0.5% Nb, 0.5% Th and 0.1% U. Geological and geochemical data suggest that all the rocks in the Burpala massif were derived from alkaline magma enriched in rare earth elements. The extreme products of magma fractionation are REE rich pegmatites, apatite–fluorite bearing rocks and carbonatites. The Sr and Nd isotope data suggest that the source of primary melt is enriched mantle (EM-II. We correlate the massif to mantle plume impact on the active margin of the Siberian continent.

U-Pb zircon geochronology and evolution of some Adirondack meta-igneous rocks

Science.gov (United States)

Mclelland, J. M.

1988-01-01

An update was presented of the recent U-Pb isotope geochronology and models for evolution of some of the meta-igneous rocks of the Adirondacks, New York. Uranium-lead zircon data from charnockites and mangerites and on baddeleyite from anorthosite suggest that the emplacement of these rocks into a stable crust took place in the range 1160 to 1130 Ma. Granulite facies metamorphism was approximately 1050 Ma as indicated by metamorphic zircon and sphene ages of the anorthosite and by development of magmatitic alaskitic gneiss. The concentric isotherms that are observed in this area are due to later doming. However, an older contact metamorphic aureole associated with anorthosite intrusion is observed where wollastonite develops in metacarbonates. Zenoliths found in the anorthosite indicate a metamorphic event prior to anorthosite emplacement. The most probable mechanism for anorthosite genesis is thought to be ponding of gabbroic magmas at the Moho. The emplacement of the anorogenic anorthosite-mangerite-charnockite suite was apparently bracketed by compressional orogenies.

Why can rossing uranium mine keep mining even in low price conditions of uranium market

International Nuclear Information System (INIS)

Tan Chenglong

2004-01-01

Rossing uranium mine is the only operating uranium mine in the world where the uranium occurs in intrusive alaskite. In the past 10 years, uranium market regressed in the world, uranium production weakened, expenditures of capital for uranium exploration were insufficient. Uranium spot market price rapidly decreased from $111.8/kg U in late 1970's to $22.1/kg U in mid-1990's. Why can Rossing uranium mine mined with traditional underground and open pit operation can keep running even in low price conditions of uranium market? Augumenting research on the deposit, mineral and technology, decreasing production cost and improving selling strategy can not only maintain Rossing's uranium production at present, but also ensure sustainable development in the coming 15 years. Exploration of low-costed uranium deposits is very important. However, obvious economic benefits can be obtained, as Rossing uranium mine does, by augumenting geological-economical research on the known uranium deposits of hard-rock type and by using new techniques to improve the conventional techniques in the uranium mine development. (authors)

International Uranium Resources Evaluation Project (IUREP) national favourability studies: Greece

International Nuclear Information System (INIS)

1977-10-01

Greece, with an area of 131,944 km 2 , has been actively explored since 1971 under a programme of co-operation with UNDP and IAEA on which close to US $1 million have been spent so far. The programme is focused on the Rhodope Precambrian massif, which is the most attractive structural unit from the geological point of view. The indications available at present, and which have been known for a long time, are also to be found in this unit. They are associated either with Tertiary continental volcanism or with detritic sediments in basins covering this massif. So far there is no evidence of their being of any economic value. The paucity of data available on the basement of the Rhodope precludes any prediction as to the possibility of its containing Pre-cambrian uranium mineralizations. One might perhaps think in terms of mineralizations of the alaskite or alkaline complex type, or also of vein-type deposits. But it is primarily in the deposits associated with tertiary trachy-rhyolitic volcanism that we have most confidence, especially in the Rhodope massif and the Vardar region but possibly elsewhere in the Hellenides as well. All things considered, we place Greece in Group 2 of the IUREP classification. (author)

Uranium exploration (2004-2014): New discoveries, new resources

International Nuclear Information System (INIS)

Polack, C.

2014-01-01

The last decade has demonstrated the dynamic of the mining industry to respond of the need of the market to explore and discover new deposits. For the first time in the uranium industry, the effort was conducted not only by the majors but by numerous junior mining companies, more than 800 companies where involved. Junior miners introduced new methodologies, innovations and fresh approach. Working mainly on former prospects of the 70’s and 80’s they discovered new deposits, transformed historical resources into compliant resources and reserves and developed new large resources in Africa, North America and Australia. In Australia, the Four Mile, Mt Gee, Samphire (SA), Mount Isa (Qld), Mulga Rock, Wiluna-Lake Maitland, Carley Bore-Yanrey-Manyingee (WA) projects were all advanced to compliant resources or reserves by junior mining companies. In Canada, activity was mainly focused on Athabasca basin, Newfoundland and Québec, the results are quite amazing. In the Athabasca 2 new deposits were identified, Roughrider and Patterson South Lake, Whilst in Québec the Matouch project and in New Foundland the Michelin project are showing good potential. In Namibia, alaskite and surficial deposits, extended the model of the Dalmaradian Central belt with the extension of rich alaskite of Z20, Husab, Omahola and large deposits of Etango and Norasa. A new mine commenced production Langer Heinrich and two are well advanced on way to production: Trekkopje and Husab. The ISL model continues its success in Central Asia with large discoveries in Mongolia and China. Europe has been revisited by some juniors with an increase of resources in Spain (Salamanca) and Slovakia (Kuriskova). Some countries entered into the uranium club with maiden resources namely Mali (Falea), Mauritania and Peru (Macusani caldeira). The Karoo formation revitalised interest for exploration within Paraguay, South Africa (Rieskuil), Botswana (Lethlakane), Zambia (Mutanga, Chirundu) and the exploitation

Holocene evolution of Dahab coastline - Gulf of Aqaba, Sinai Peninsula, Egypt

Science.gov (United States)

Torab, Magdy

2018-03-01

Dahab is a little Bedouin-village in Sinai Peninsula on the east coast of the Gulf of Aqaba and it lies approximately 90 km north of Sharm-el-Sheikh City. Dahab means "gold" in the Arabic language; over the past 20 years it has become one of the most visited tourist sites in Egypt. The basement complex is composed mostly of biotite aplite-granite, mica-aplite granite, granodiorite, quartz diorite, alaskite, and diorite. This composition correlates to similar igneous rocks in the most southern areas of Sinai and the Red Sea. Wadi Dahab is composed of igneous and metamorphic rocks and the coastline is formed of fragments of its rocks mixed with fragments of coral reef. The morphology of Dahab's coastline is characterized by a hooked marine spit composed of fluvial sediments carried by marine currents from the mouth of Wadi Dahab. This spit encloses a shallow lagoon, but the active deposition on the lagoon bottom will turn it into saline marsh. This paper investigates the evolution of the Dahab spit and lagoon during the Holocene and over the last 100 years, as well as the potential impacts of future management of the coastal area. The coastline mapping during the study was dependent on GIS techniques and data were collected by using total station, aerial photographs and satellite image interpretation as well as soil sample dating.

International Uranium Resources Evaluation Project (IUREP) national favourability studies: Burma

International Nuclear Information System (INIS)

1977-10-01

Kyatpyin, near Mogok; radioactive iron ore at Pangpet, near Taunggyi, Southern Shan States and radioactive fossil wood from Central Burma. From structural point of view the most favourable geological environments for new discoveries are those in the Central, Basin, or as it is named Irrawaddy Basin and Shan Plateau massif. Sedimentary rocks of enormous thickness were formed, in the intramountain Irrawaddy Basin during the Tertiary Period. There is no information about the facies of the sediments but it could be supposed that most of these strata were deposited either in fans or rivers and have features of fluvial facies which is most favourable for uranium concentration leached from surrounding granites and alaskite in Shan plateau massif. The radioactive fossil wood from Central Burma may be an indication for uranium favourability of this basin. The known uranium occurrences in Mogok Belt could be considered, as indicative of some uranium potential of the region mainly of the alaskite and the areas around it. There is also potential in the Tawang Peng area of the Northern Shan States, where the famous multi-metal Bawdwin mine is located in a series of rhyolitic tuffs, lava flows and breccias, interspersed with coarse feldspathic grits of early Paleozoic age. The speculative potential could be about 10,000 tonnes uranium