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Emplacement mechanisms and structural influences of a younger granite intrusion into older wall rocks - a principal study with application to the Goetemar and Uthammar granites. Site-descriptive modelling SDM-Site Laxemar  

Energy Technology Data Exchange (ETDEWEB)

The c. 1.80 Ga old bedrock in the Laxemar-Simpevarp area, which is the focus of the site investigation at Oskarshamn, is dominated by intrusive rocks belonging to the c. 1.86-1.65 Ga Transscandinavian Igneous Belt (TIB). However, the site investigation area is situated in between two c. 1.45 Ga old anorogenic granites, the Goetemar granite in the north and the Uthammar granite in the south. This study evaluates the emplacement mechanism of these intrusions and their structural influence on the older bedrock. Field observations and structural measurements indicate that both the Goetemar and the Uthammar granites are discordant and have not imposed any significant ductile deformation on their wall-rocks. The apparent conformity of geological contacts and fabrics in the wall rocks and the southern margin of the Goetemar granite is coincidental and inherited from the pattern of Svecokarelian deformation of the TIB. However, interpretation of regional aeromagnetic data suggests that the granites occur within a broad, NNE-SSW trending linear belt, pointing to deep seated tectonic control on their generation, ascent and emplacement. Thermochronology indicates that the granites were emplaced at depths between 4 and 8 km into brittle wall rocks. The 3-D shape of the Goetemar and Uthammar plutons has been investigated by 2.75D forward modelling of the residual gravity anomalies due to both granites. Both granites are associated with strong residual gravity anomalies of up to -10 mgal. Constraints on the geometry of the plutons at the surface are provided from surface geology maps and several deep boreholes located on or close to the model profiles. A further variable in the gravity modelling is introduced by either allowing the upper contact of the plutons to assume the most suitable orientation to produce the best fit between the modelled and observed gravity ('unconstrained models') or by forcing the near surface orientation of the contacts to be vertical ('constrained models'). The unconstrained model profiles for both plutons are characterized by gently outward dipping upper contacts to depths approx1 km, gently inward dipping lower contacts and a thin, centrally located root extending to depths of 5 to 10 km. However, this geometry is not supported by available boreholes, which do not penetrate the upper contact of the Goetemar pluton as predicted by the models. The constrained models are consistent with borehole data. They characterize the plutons as having vertical contacts in the upper 500 to 1,000 m, a 1,000 to 1,500 m thick mid-level body with outward dipping upper and horizontal and lower contacts, respectively, and broad roots extending to depths of approx4 km. Preliminary observations and gravity modelling results indicate that the Goetemar and Uthammar granites are discordant plutons with geometries most consistent with punched laccoliths, with some modification due to floor subsidence due to root development. Their vertical and lateral dimensions fall in the upper range for laccoliths and lower range for plutons as defined by recent data compilations. Their emplacement required elastic bending and eventual failure of roof rocks that was likely accompanied by reactivation of pre-existing fractures and shear zones and possibly the creation of new brittle fractures. Cooling and crystallization of the granites resulted in thermal resetting of the wall rocks and the establishment of a transient hydrothermal system, now recorded by fracture filling mineral assemblages

Cruden, Alexander R. (Dept. of Geology, Univ. of Toronto (Canada))

2008-12-15

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Emplacement mechanisms and structural influences of a younger granite intrusion into older wall rocks - a principal study with application to the Goetemar and Uthammar granites. Site-descriptive modelling SDM-Site Laxemar  

International Nuclear Information System (INIS)

The c. 1.80 Ga old bedrock in the Laxemar-Simpevarp area, which is the focus of the site investigation at Oskarshamn, is dominated by intrusive rocks belonging to the c. 1.86-1.65 Ga Transscandinavian Igneous Belt (TIB). However, the site investigation area is situated in between two c. 1.45 Ga old anorogenic granites, the Goetemar granite in the north and the Uthammar granite in the south. This study evaluates the emplacement mechanism of these intrusions and their structural influence on the older bedrock. Field observations and structural measurements indicate that both the Goetemar and the Uthammar granites are discordant and have not imposed any significant ductile deformation on their wall-rocks. The apparent conformity of geological contacts and fabrics in the wall rocks and the southern margin of the Goetemar granite is coincidental and inherited from the pattern of Svecokarelian deformation of the TIB. However, interpretation of regional aeromagnetic data suggests that the granites occur within a broad, NNE-SSW trending linear belt, pointing to deep seated tectonic control on their generation, ascent and emplacement. Thermochronology indicates that the granites were emplaced at depths between 4 and 8 km into brittle wall rocks. The 3-D shape of the Goetemar and Uthammar plutons has been investigated by 2.75D forward modelling of the residual gravity anomalies due to both granites. Both granites are associated with strong residual gravity anomalies of up to -10 mgal. Constraints on the geometry of the plutons at the surface are provided from surface geology maps and several deep boreholes located on or close to the model profiles. A further variable in the gravity modelling is introduced by either allowing the upper contact of the plutons to assume the most suitable orientation to produce the best fit between the modelled and observed gravity ('unconstrained models') or by forcing the near surface orientation of the contacts to be vertical ('constrained models'). The unconstrained model profiles for both plutons are characterized by gently outward dipping upper contacts to depths ?1 km, gently inward dipping lower contacts and a thin, centrally located root extending to depths of 5 to 10 km. However, this geometry is not supported by available boreholes, which do not penetrate the upper contact of the Goetemar pluton as predicted by the models. The constrained models are consistent with borehole data. They characterize the plutons as having vertical contacts in the upper 500 to 1,000 m, a 1,000 to 1,500 m thick mid-level body with outward dipping upper and horizontal and lower contacts, respectively, and broad roots extending to depths of ?4 km. Preliminary observations and gravity modelling results indicate that the Goetemar and Uthammar granites are discordant plutons with geometries most consistent with punched laccoliths, with some modification due to floor subsidence due to root development. Their vertical and lateral dimensions fall in the upper range for laccoliths and lower range for plutons as defined by recent data compilations. Their emplacement required elastic bending and eventual failure of roof rocks that was likely accompanied by reactivation of pre-existing fractures and shear zones and possibly the creation of new brittle fractures. Cooling and crystallization of the granites resulted in thermal resetting of the wall rocks and the establishment of a transient hydrothermal system, now recorded by fracture filling mineral assemblages

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The petrogenesis of the Younger granites of Nigeria  

Science.gov (United States)

The occurrence of basic, intermediate and rhyolitic rocks, together with their granitic equivalents in the Younger granites of Nigeria, suggests a basic magmatic parent for the rocks of this province. The evolution is thought to be through plagioclase, fayalite, clinopyrexene, K-feldspar and quartz fractionation. The pervasive alteration of the K-feldspar, turbidity, coalescence of exsolved albitic belbs, albitiztion, degradation of mafic minerals and subsolidus habit of crystallization of biotite, arfvedsonite, riebeckite and albite indicate the involvement of metasomatic reactions in the course of evolution of these rocks. The enrichment of incompatible trace elements in the peralkaline and peraluminous rocks and adjusted REE patterns of their K-feldspar, together with the differential degrees of mineralization of similar rock-types are attributed to the variable rock-fluid interaction of these rocks at variable temperatures and compositions of the fluid. Basaltic magma or magmas probably fractionated to the level of biotite granites, while rocks with secondary biotite, arfvedsonite, riebeckite aegirine and albite granites are products3of K- and Na-metasomatism, thus representing rocks of magmatic origin that have suffered variable rock-fluid interaction. In the course of fractionation, alkaline rich fluids were accumulated and retained at different segments of the evolved melts. Repeated intrusion of such melts and successive rock-fluid interaction led to formation of rocks subsolidus minerals.

Badejoko, T. A.

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Uranium potential of the younger granites of Egypt  

International Nuclear Information System (INIS)

The post-tectonic Pan-African younger granites of Egypt are characterized by abnormal radioactivity. Several plutons of these granites in the Eastern Desert, host a variety of rare metal mineralizations including uranium. Two younger granite plutons, namely El Missikat and El Erediya, in the central part of the Eastern Desert, host siliceous vein-type uranium mineralization, which is structurally controlled by faults and their feather joints associated with NE and NNE trending shear zones. The Gattar granite pluton, at the northern part of the Eastern Desert, hosts vein-type uranium mineralization associated with molybdenite. At the southern part of the Eastern Desert, Um Ara granite pluton hosts uranium as disseminated unconformity contact type. Pitchblende is the primary mineral, while secondary uranium minerals are mainly: uranophane, ?-uranophane, soddyite and renardite. Small amounts of pyrite, chalcopyrite, galena, sphalerite, molybdenite and violet fluorite are present in association with the uranium mineralization in the mineralized zones. Present data suggest an origin by hydrothermal fluids derived from the granitic magma. Redistribution by circulating meteoric water may have taken place as evidenced by widespread alteration, particularly silicification. Exploratory mining resulted in clarifying the possibility of the extension of the uranium mineralization zone laterally and in depth. The estimation of the uranium potentiality of the four younger granite potentiality of the four younger granite plutons is 14000 tons uranium as speculative resources. (author). 25 refs, 1 fig., 1 tab

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Petrogenesis of selected A-type granitic intrusions from Central Eastern Desert of Egypt  

Science.gov (United States)

The Pan-African orogeny in the Arabian-Nubian Shield was terminated by intrusion of A-type granites (~ 595 Ma; Greenberg, 1981) and its volcanic equivalents. Subsequent to the intrusions of these granitic bodies the shield was exhumed. Eroded A-type granite pebbles were found in the molasse sediments that were deposited in intermountain basins. Therefore the A-type granites provide information about the last stage of the Pan-African geochemical system. Preliminary whole-rock geochemical data of three granitic intrusions (Kadabora, Um Naggat and El shiekh Salem) from the Central Eastern Desert of Egypt; indicate that all of them are peraluminous and with A-type characteristics. These intrusions show low CaO content (average 0.43 %wt), high FeOT/MgO ratio (10.46-121.88), high Na2O+K2O (average 8.04 %wt), marked enrichment of high field strength elements (Y, Nb and Ga except Zr), depletion in MgO (0.01-0.11 %wt) and with low concentration of Sr and Ba. The studied granitoids were emplaced in within plate tectonic regime. References: Greenberg, J.K. (1981): Characteristic and origin of Egyptian younger granites. Bull. Geol. Soc. Am. Part 1, v.92: 224-232.

Hassan, Tharwat; Asran, Asran; Amron, Taha; Hauzenberger, Christoph

2014-05-01

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Characteristics and significance of uranium bearing pan african younger granite in the eastern desert, Egypt  

International Nuclear Information System (INIS)

Surficial uranium mineralization was discovered in four pan african younger granite plutons in the eastern desert of egypt. The present study revealed great similarity between these plutons both in petrography and geochemistry. They are two-feldspar, two-mica peraluminous granites which have been formed by melting of crustal materials and emplaced during the late stage stage of a late proterozoic orogenic cycle. Radiometric and geochemical investigations indicate that these granites are fertile with respect to U and form a potential target for primary uranium deposits. Four models are suggested to explain the source and mechanism of the surficial uranium mineralization in these granites. The most applicable model is the oxidation of U+4 found in minute disseminated uraninite grains and its subsequent mobilization. This is supported by petrographic and autoradiographic studies. The bearings of the present study on further exploration for uranium deposits in granites of the arabian- Nubian shield in general are discussed

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Intrusive rocks from Polumir and Željin (Serbia): two contrasting granit?id types  

OpenAIRE

This paper outlines correlation of the most distinctive features of intrusive rocks from Polumir (granite from Polumir, Polumir granite) and from Željin (Željin granitoid). Although these two intrusions are notable similar in space (10-12 km) and time (beginning of Miocene), they are very different, even contrasting concerning their petrography, genesis and geotectonic. Mineralogy, petrology and chemistry of Polumir granite (P?2.5 km2), and of Željin quartz diorite and tonalite, as well ...

Milenko

2014-01-01

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Analysis of magnetic data over part of the Younger Granite Province of Nigeria  

Science.gov (United States)

The results of a magnetic study of part of the Younger Granite Province of Nigeria are presented here. Spectral analysis of the magnetic anomalies over the area has been carried out in an effort to estimate the depth to magnetic sources. Average magnetic source depth of 286 m has been obtained for the area and this is thought to be related to the depth to the top of the main anomalous structures in the area. Observed magnetic anomaly profiels taken across the area have been interpreted in terms of arbitrarily shaped bodies—whose existence was confirmed by 3-D Hilbert transformation-using nonlinear optimization techniques. The modelled bodies occur at depths of 200 760 m and have magnetizations of 0.29 0.47 A/m. The results from the analysis of the magnetic field are discussed in relation to the results from previous gravity studies over the area and the mode of emplacement of the Younger Granites.

Ofoegbu, Charles O.; Hein, Karin

1991-07-01

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Evolution of zircons from postorogenic intrusive series with Li-F granites, Russian Far East  

Science.gov (United States)

The paper discusses the morphology, anatomy, and geochemistry of zircons from granitic rocks of postorogenic intrusive series with Li-F granites in the Russian Far East. The multiphase Upper Urmi pluton in the Amur region and the Severny pluton in the Chukchi Peninsula have been chosen as reference objects. The directed variations of zircon morphology and geochemistry in the history of Pacific postorogenic granitic magmatism reflect decrease in depth of magma generation and crystallization temperature along with an increase in alkalinity, fluid saturation, and rare-metal potential of granitic melts.

Alekseev, V. I.; Polyakova, E. V.; Machevariani, M. M.; Marin, Yu. B.

2014-12-01

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Intrusive rocks from Polumir and Željin (Serbia: two contrasting granit?id types  

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Full Text Available This paper outlines correlation of the most distinctive features of intrusive rocks from Polumir (granite from Polumir, Polumir granite and from Željin (Željin granitoid. Although these two intrusions are notable similar in space (10-12 km and time (beginning of Miocene, they are very different, even contrasting concerning their petrography, genesis and geotectonic. Mineralogy, petrology and chemistry of Polumir granite (P?2.5 km2, and of Željin quartz diorite and tonalite, as well as of granodiorite and granite (P?56 km2, i.e. properties that directly reflect on their genesis and geotectonic setting, are presented in this paper. Chemistry of biotite, the only mineral observed in both plutons, as the direct evidence of different physical-chemical conditions during consolidation and proof for their genetic contrast, is contributed.

Milenko

2014-11-01

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Genesis of Uranium in the younger granites of gabal abu hawis area, central eastern desert of Egypt  

International Nuclear Information System (INIS)

The younger granites cropping out in gabal abu hawis area are considered as uraniferous (fertile) granites (the fertile is mainly is mainly attributed to presence of radioactive zircon). Abu hawis granitic pluton is dissected by joints faults of different trends forming two mineralized shear zones in the northern peripheries and southern border. The younger granites hosting uranium mineralizations along the two mineralized shear zones. The uranium minerals include uranophane and carnotite. The altered granites have much lower Th/U ratios (0.03-0.10) than those of the fresh granites (1.69-2.05), indicating strong mobilization of uranium in this pluton by super-heated solutions that resulted from supergence meteoric water as well as U-addition by hypogene fluids. These solutions could pass through the structural network of fractures, joints and fault planes and have leached some of labile uranium from the surrounding rocks and/or the younger granites themselves. Then, changing in the physicochemical conditions of these solutions caused uranium precipitation as uranium minerals filling the cracks in the rock and/or adsorbed on the surface of clay minerals and iron oxides in the two shear zones

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Variation in composition and delta18O values within the Kaffo albite-riebeckite granite of Liruei complex, younger granites of Nigeria  

International Nuclear Information System (INIS)

Granite is one of the oldest of the ring-complexes in the Younger Granite province of Nigeria. Isotopically the granite is a normal plutonic type with delta18O values of + 8.1 +- 0.2 per mill. The amphibole and pyroxene have low variable delta18O values (+5.3-+6.4 and +4.4-+5.1 per mill, respectively). The low delta18O values are considered to be due to special features of the crystal chemistry of alkali amphiboles and pyroxenes, and the spread of each set of values may be due to sub-solidus isotope exchange between the minerals and albitising fluid

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Oxygen isotope geochemistry of the Granite Harbour Intrusives, Wilson Terrane, Northern Victoria Land, Antarctica  

International Nuclear Information System (INIS)

The oxygen and strontium isotope compositions of the Cambro-Ordovician granitoids cropping out in the Wilson Terrane (Granite Harbour Intrusives-GHI) constrain the petrological evolution of the magmatism in Antarctica, related to the Ross Orogeny. The measured ?18OWR values of three intrusives define three different compositional groups: the metaluminous rocks (MAG), with ?18OWR ranging from 6.9 (olivine gabbro) to 11.4 %o (monzogranite); the unaltered peraluminous granites (PAG), having ?18OWR values ranging from 10.6 to 13.2 %o, and the foliated peraluminous leucogranites (SKG), characterized by ?18OWR values above 14 %o. The analysis of equilibrium mineral assemblages indicates that the high ?18OWR values are magmatic and unaffected by low-temperature processes. A few peraluminous granites sampled in the vicinity of Cenozoic intrusions show anomalously low ?18OWR, due to meteoric-hydrothermal alteration. The isotopic data indicate that the coeval and spatially related metaluminous mafic and felsic intrusives forming the GHI were not comagmatic: the mafic and intermediate rocks were likely derived from lower crustal contamination of a pristine basaltic magma; their ?18OWR values were also increased during emplacement, due to the interaction with the adjacent 18O-rich hydrous felsic magmas (mixing)rich hydrous felsic magmas (mixing). Oxygen isotope data indicate that the crustal sources producing the granite harbor intrusives were not homogeneous: the felsic metaluminous intrusives were produced by partial melting of fertile rock with possible igneous origin, whereas partial melting of a metapelitic source rock is claimed for the genesis of the peraluminous granites. (author)

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Three Paleoproterozoic A-type granite intrusions and associated dykes from Kainuu, East Finland  

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Full Text Available Mafic and felsic intrusive rocks aged 2.5–2.4 Ga have been observed over a large area in eastern and northern Finland, as well as in adjacent northwestern Russia. We describe three granite intrusions and associated dykes from Kainuu, Finland, that belong to this bimodal magmatic event. All these three granites show clear A2-type chemical affinities with high Y/Nb, HREE, Fe/Mg, Ga and Nb. Two of the intrusions, Rasinkylä and Pussisvaara, were dated at 2425±3 and 2427±3 Ma, respectively, using thermal ionisation mass spectrometry utilizing the chemical abrasion method (CA-TIMS. CA-TIMS ages are supported by single-grain age determinations obtained by using Laser Ablation Multicollector Inductively Coupled Plasma Mass Spectrometer (LA-MC-ICPMS. New data on the previously described Rasimäki granite from southern Kainuu is presented, including an age of 2389±5 Ma obtained with LA-MC-ICPMS. The variable magnetite content of the granites is proposed to reflect the differences in the oxidation state of the source, which in our interpretation is the local Archean lower crust. Partial melting and the emplacement of the granites occurred in an extensional environment. Heat for the partial melting was provided by mafic magmas under and intraplating the extended crust.

Hannu Huhma

2010-12-01

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Age of the Mulcahy Lake intrusion, northwest Ontario, and implications for the evolution of greenstone-granite terrains  

International Nuclear Information System (INIS)

Zircon data from a 63 km2 layered mafic intrusion in the Wabigoon subprovince, the Mulcahy Lake gabbro, show that the gabbro crystallized at 2733.2(+1.0-0.9) Ma. The largely unaltered and unmetamorphosed gabbro intrudes tholeiites of the Crow Lake-Savant Lake greenstone belt which were generated over at least a 10 Ma time span. Rb-Sr and Sm-Nd data were obtained for pristine whole rock and mineral separates from the intrusion. The Rb-Sr data show disturbances in the system, particularly in the case of pyroxenes. Samples with low Rb/Sr ratios indicate an initial Sr ratio of 0.7007 for an age of 2733 Ma. The Sm-Nd age is 2744+-55 Ma, and an epsilon Nd value of +2.6+-1.2 indicates a light rare earth element depleted source. The Sm-Nd data shows less disturbance than the Rb-Sr data. Granitic and mafic intrusives with similar initial ratios occur 80 km to the south in the Quetico subprovince. Primary hornblende was analyzed for 40Ar/39Ar. The age obtained is 2703+-20 Ma, clearly younger than the zircon age indicating some argon loss. (orig.)

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Discriminations of Younger Granitic Masses at Gabal Qattar Area, North Eastern Desert, Egypt, Using Remote Sensing Techniques  

International Nuclear Information System (INIS)

Gabal Qattar area is located in the north Eastern Desert of Egypt between Latitudes 26 degree 52 and 27 degree 08 N, and Longitudes 33 degree 13 and 33 degree 25 E. The exposed rock units, there, from the oldest to the youngest, are meta volcanics; granodiorites- diorite complex; Hammamat sediments and younger granites. Most of the area is densely traversed by felsic and mafic dykes. The Qattarian younger granites are divided into seven granitic areas according to their spectral characters to facilitate the studying and delineating physical characteristic differences between these areas as well as to throw a light about the best conditions of exploration for radioactive mineralizations. This study is based on brightness Digital Number values (DNs) of the granitic areas, predominant trends and densities of the structural lineaments, shape and type of weathering products. Three areas of these seven younger granite areas form Gabal (G.) Qattar, and designated Gr 1, Gr 3 and Gr 4, where the other granite areas which form the G. Urn Dissi (Gr 2), G. Thelma (Gr 5), G. Abu Samyuk (Gr 6) and G. Ayn AI Ruwayshed (Gr 7). Photo geologically, these seven granite areas show some differences in shape, texture, predominant trends and densities of structural lineaments and ability of weathering. This study shows that the seven granite areas could be gathered into three main groups according to their DNs values of Landsat ETM+ spectral bands especially of band 5, where these three maispecially of band 5, where these three main groups representing different, and mainly coincide with the three granite phases previously delineated according to chronological field relation, petrographic and geochemical studies. The Gr 1 area contains all uranium occurrences from locations I to V. This area is characterized by semi circular shape of NW trend, massive appearance with high relief peaks, and high fracture density, where the N 55 degree E, N 5 degree E, N 45 degree E and N 45 degree W are the predominant trends. Some of the N 55 degree E fractures form shear zone along the contact with Hammamat sediments. This granitic area displays taffoni weathering with highest clay minerals content in its weathered surfaces. It shows the highest brightness value (DN), especially in band 5 reaching about 152, due to the highest felsic minerals and the lowest ferro magnesian minerals contents relative to the other granite areas. Also, the high fractures density of the Gr 1 area acted as good channels for the hydrothermal ascending fluids and the percolating meteoric water, that leached uranium mineralization and redeposited it in the shear zones especially at sites of intersection of the main fractures. These characteristic features of the Gr 1 area may be responsible for the presence of uranium mineralizations

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Age of Pedra Branca granite (Goias) and possible geotectonic implications  

International Nuclear Information System (INIS)

Rb-Sr geochronologic dating of granites from the Pedra Branca Granite Massif (Nova Roma, Goias) shown an age of 1405 ± 21My. and a questionable initial Sr87/Sr86 ratio of 0,7004 ± 0,006. Rhyolite from the base of the Arai Group is probably of the same age as the granitic intrusion. The 475 ± 19 My. age for the granitic intrusion is evidence of the Brasiliano Cycle imprint in Pedra Branca region. The age attributed to the Pedra Branca Granite is lower than known ages of the Goias tin granites giving rise to new geotectonic interpretations. It is possible that the Pedra Branca Granite represents a low-level intrusion emplaced at the beginning of structuration and deposition of the Arai basin. It may be correlated with granitic intrusions related to a rift stage above mantle hot spots, like the Nigerian tin younger granites. (author)

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Contribution to uranium geochemistry in intrusive granites; Contribution a la geochimie de l'uranium dans les granites intrusifs  

Energy Technology Data Exchange (ETDEWEB)

This work aims to define the position of a certain number of French granitic deposits within the field of the geochemistry of granites in general, and of the geochemistry of uranium in particular. The regions concerned are: - 3 French Hercynian ranges, in the Vendee, in Brittany and in the Morvan, - 1 African range, probably precambrian, of the Hoggar. For each range, the petrochemical framework is first of all determined and then the degree of chemical homogeneity of the rocks is evaluated. In the petrochemical groups thus obtained the geochemical behaviour of the uranium is studied. From a point of view of the geochemistry of the granites under investigation, a comparison of the laws of distribution of the major elements in the 4 ranges shows up a convergence of average composition which was not anticipated by geological and petrographic considerations alone. The statistical and geochemical distribution laws of the total uranium as a function of the petrochemical variations are established. A study of the chemical forms of uranium in the rocks has drawn an attention to the qualitative and quantitative importance of the fraction of this uranium soluble in dilute acids. We have therefore reconsidered on the one hand, the laws of distribution of the insoluble uranium, which represents essentially the uranium fixed in crystalline structures (zircon, allanite...), and we have justified on the other hand the interest presented by the soluble uranium: this, although more complex in character, presents a geochemical unity in post magmatic phenomena which makes possible to find a genetic connection between the uraniferous deposits and the intrusive massifs. Finally we have given a plan of the geochemical cycle of uranium, in which we hope to have provided some more accurate data on the igneous phase. (author) [French] Le but du travail presente est de situer sur le plan de la geochimie des granites en general, sur le plan de la geochimie de l'uranium en particulier, un certain nombre de massifs granitiques francais: - 3 massifs hercyniens francais, en Vendee, en Bretagne et dans le Morvan, - 1 massif africain, probablement precambrien, du Hoggar. Dans chaque massif, nous determinons en premier lieu le cadre petrochimique et evaluons le degre d'homogeneite chimique des roches. Dans les familles petrochimiques ainsi determinees, nous etudions le comportement geochimique de l'uranium. Du point de vue de la geochimie des granites etudies, le comparaison des lois de repartition des elements majeurs fait apparaitre dans les 4 massifs une convergence de composition moyenne que ne laissaient pas prevoir la geologie et la petrographie. Nous etablissons les lois de repartition statistiques et geographiques de l'uranium total en fonction des variations petrochimiques. L'etude des formes de l'uranium a l'interieur des roches a attire notre attention sur l'importance qualitative et quantitative de la fraction de cet uranium soluble dans les acides dilues. Nous reprenons donc, d'un cote les lois de repartition de l'uranium insoluble qui represente pratiquement l'uranium inclus dans les structures cristallines (zircon, allanite...) et justifions d'un autre cote l'interet presente par l'uranium soluble qui, malgre un caractere plus complexe, permet par son unite geochimique dans les phenomenes postmagmatiques, de trouver une liaison genetique entre les gisements uraniferes et les massifs intrusifs. Nous presentons enfin, un schema du cycle geochimique de l'uranium dans lequel nous esperons avoir pu apporter quelques precisions sur la phase ignee. (auteur)

Coulomb, R. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1959-01-15

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Pegmatoid schlieren with tourmaline in granitoids of eastern russia as an attribute of intrusive series completed by ore-bearing Li-F granites  

Science.gov (United States)

Tourmaline schlieren in pegmatoids and host granites are widespread in Cretaceous granitoid plutons occurring in tin districts of eastern Russia. These schlieren were formed under the action of fluoricboron fluids, which are considered to be forerunners of rare-metal granite magmatism. The tourmaline schlieren in adamellites, biotite, and two-mica granites are reliable attributes of intrusive series completed by emplacement of ore-bearing Li-F granites.

Alekseev, V. I.; Marin, Yu. B.

2014-12-01

20

Kuznechensky intrusion of K-rich porphyric granites: U-Pb data and tectonic position (Baltic shield)  

International Nuclear Information System (INIS)

For studying the conditions and age range of formation of the Kuznechensky intrusion (Baltic shield) the U-Pb isotope dating of zircon and monazite within granites of the intrusion mentioned was performed. Bearing in mind the morphological characteristics of the zircon studied, suggesting its magmatic origin, the age value obtained, equal to 1874 ± 4 mln. years, is referred to the time of the massif crystallization. The monazite age (1851 ± 5 mln. years) reflects the period of its U-Pb system closing and corresponds to metamorphism time

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Petrography and major element geochemistry of the younger granites of Sindhudurg district, Maharashtra, India and their bearing on the associated radioactive pegmatites  

International Nuclear Information System (INIS)

The Precambrian metasediments exposed in the Sindhudurg district of Maharashtra are intruded at numerous places by the younger granites and associated pegmatites. The pegmatites are radioactive at a number of places and have analysed 3O8 and 2. The granites are two-mica bearing peraluminous with fairly uniform composition and relatively high uranium (11-21 ppm) content, post-orogenic and appears to have formed by crustal anatexis at a minimal temperature of 685 deg at a relatively PH2O of 5 kb (assumed). The initial granitic melt formed was rich in uranium and its subsequent crystallisation and differentiation resulted in the concentration of U and Th and rare metals of Nb, Ta in the residual and subsequent pegmatitic fluids, manifested mineralogically as uraninite and columbite in pegmatite associated with these granites. (author)

22

Numerical Simulations of the Incremental Intrusion of Granitic Magma into Continental Crust  

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We have employed the visco-elasto-plastic Finite-Element & Marker-in-cell code, MILAMIN_VEP, to carry out a 2D modeling study of the incremental intrusion of granitic magma into continental crust. Algorithms of multiple pulses of magma and pseudo-diking are implemented into the code. New magma of an initial circular shape is regularly replenished at "magma source" regions at sub-crustal depths. Pseudo-dikes of rectangular shapes are added at location where the maximum differential stress along the melt-solid interface is greater than an assigned tensile strength of the surrounding solid host rock. Preliminary results show that when diking and multiple pulses of magma are included, later pulses of magma rise higher and faster and even reach the Earth's surface in some cases by taking advantage of the pre-heated low-viscosity pathways created by earlier dikes and pulses of magma. Host rocks display bedding rotation, and downward flow at two sides of a growing magma chamber but show discordantly truncation when magma ascend through the weak channels made by dikes. The effect of the thermal structure of the crust was tested as well. In a cold crust, "diking" is critical in breaking the high-viscosity crust, guiding the direction of magma rising, and facilitating later magma pulses to form chambers. In a warmer crust, magma rises in the form of diapirs, after which dikes take over in transporting later pulses of magma to the surface. The simulations also suggest that a magma chamber incrementally constructed by multiple magma bathes is a very dynamic environment featuring intra-chamber convection and recycling previous batches of magma. In simulations without diking and multiple pulses, magma is unable to reach the shallow crust. Instead, it is stuck in the middle crust, as the viscosity of the upper crust is too large to permit rapid motion, and at the same time magma-induced stresses are insufficient to deform the upper crust in a plastic manner. Intra-crustal convection in the middle and lower crust occurs regardless of the flow flaws and geothermal gradients employed. Simulations with only one of the algorithms also fail to bring magma to the shallow crust. The simulations suggest that multiple pulses and diking might be two important factors aiding the rise of granitic magma to the uppermost crust. These results have implications for the magmatic evolution of arcs such as the Mesozoic Sierra Nevada arc. They may help us to understand the processes such as the ascent of magma, incremental growth of a large magma chamber, and host rock deformation accompanying with magma ascent and emplacement.

Cao, W.; Kaus, B. J.; Paterson, S. R.

2012-12-01

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Interactions between extensional shear zones and syn-tectonic granitic intrusions: the example of Ikaria Island (Cyclades, Greece)  

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The Aegean domain is an ideal place to investigate the development of Metamorphic Core Complex (MCC) and to study the role of syn-tectonic granites on their development. MCCs of the Aegean domain are dynamically associated with a few major detachments, especially the North Cycladic Detachment System (NCDS) and the West Cycladic Detachment System (WCDS), which have accommodated a large part of the crustal thinning during the Oligocene and Miocene. The NCDS extends toward the East within the Simav Detachment that has exhumed the northern high-temperature part of the Menderes massif. The transition between the NCDS and the Simav Detachments is located above a major tear in the Aegean slab whose effects on lithospheric deformation are far from understood. The Aegean granitoids were emplaced during the Middle Miocene within a zone of high-temperature during the episode of slab tearing and recorded increments of extensional tectonics within this complex zone. Ikaria Island (Cyclades, Greece) is a metamorphic dome intruded by three Miocene granitoid plutons (one I-type intrusion, two S-type ones) including the largest pluton of the Aegean domain. However, geometry, structures and kinematics are still debated with several recent yet conflicting studies. We have reconsidered the geology of Ikaria to settle the geological and structural context of these plutons. The intrusion depth of the Raches granite has been estimated at 10-15 km by the Al-in-hornblende barometer. Our field study has led to the identification of two major structures: the Gialiskari and Kalamos detachments, which we interpret as belonging to the NCDS. A study of deformation in the granites has highlighted a continuum during cooling that can be described in three stages: i) magmatic deformation, ii) high-temperature ductile deformation from late magmatic stage until complete crystallization of the granite, iii) low-temperature brittle deformation. Throughout this evolution, the same top-to-the-NE shearing deformation was active below the Gialiskari and Kalamos detachments with a progressive localization of strain. A scenario of this deformation continuum below the Gialiskari-Kalamos detachments through the ductile-brittle transition is proposed. The granites were emplaced while the exhumation of the Ikaria high-temperature metamorphic dome was already underway. We conclude that the crustal-scale detachment has controlled the localization of the intrusion and not the opposite.

Laurent, Valentin; Beaudoin, Alexandre; Jolivet, Laurent; Arbaret, Laurent; Augier, Romain; Rabillard, Aurelien

2014-05-01

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Gravimetric modeling of the Parguaza granitic intrusion, Guyana Precambrian Shield, southwestern Venezuela using geochronological constraints  

OpenAIRE

A combined gravimetric and geochronological interpretation of the Parguaza intrusion in the Guayana shield, southwestern Venezuela, indicates that there is a pattern of inverse cooling within this pluton. Based on a positive correlation between Rb/Sr whole rock apparent ages and residual Bouguer anomaly, density contrasts over the Parguaza intrusion are linked to temperature and crystallization of mineral phases. This hypothesis is supported by density measurements on hand samples and by inde...

Oscar Mirón-Valdespino; Vincenzo Costanzo-Álvarez; Carlos Izarra; Ja?come, Mari?a I.

2004-01-01

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Gravimetric modeling of the Parguaza granitic intrusion, Guyana Precambrian Shield, southwestern Venezuela using geochronological constraints  

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Full Text Available A combined gravimetric and geochronological interpretation of the Parguaza intrusion in the Guayana shield, southwestern Venezuela, indicates that there is a pattern of inverse cooling within this pluton. Based on a positive correlation between Rb/Sr whole rock apparent ages and residual Bouguer anomaly, density contrasts over the Parguaza intrusion are linked to temperature and crystallization of mineral phases. This hypothesis is supported by density measurements on hand samples and by independent geochemical evidence. A simple 2D gravity model is constrained by surface geology, Rb/Sr apparent ages (whole rock and residual Bouguer anomalies. Gravimetric modeling implies a model of horsts and grabens that accounts for inverse zoning of the intrusion as a result of geological and age contrasts across the faults.

Oscar Mirón-Valdespino

2004-12-01

26

Boron and boron isotope systematics in the peralkaline Ilímaussaq intrusion (South Greenland) and its granitic country rocks: A record of magmatic and hydrothermal processes  

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Concentrations of boron in whole rocks and minerals of the peralkaline, 1.16 Ga Ilímaussaq intrusion and its granitic country rocks (South Greenland) were analysed using secondary ion mass spectrometry (SIMS) and prompt gamma neutron activation (PGNAA) analysis. The intrusion consists of an early augite-syenite shell, a later alkali-granite sheet and still later nepheline syenites, which dominate the Complex. Boron concentrations are high (250-280 ?g/g) in all rocks containing fresh sodalite, whereas boron is constantly low in the sodalite-free augite syenites (4-6 ?g/g) and in the alkali granites (7-22 ?g/g). Rocks with sodalite altered to analcime contain only low amounts of boron (2-7 ?g/g), which records boron extraction by late-magmatic fluids. Concentration profiles of B in the analysed minerals (olivine, amphibole, clinopyroxene, aenigmatite, eudialyte, biotite, feldspar, nepheline and sodalite) record magmatic fractionation to various extents, late-magmatic to hydrothermal fluid/rock interaction, and sub-solidus diffusion. Whole-rock concentration data cannot be directly translated into the geochemical evolution of the peralkaline melts, since they are largely affected by cumulate fractionation of sodalite and amphibole and furthermore by late-stage hydrothermal alteration processes resulting in B loss. However, trace-element concentrations of mineral zones representing equilibrium fractionation from magmatic liquids can be used in combination with mineral-melt partition coefficients to unravel the enrichment processes of elements in the melt. Boron isotope values of minerals from the intrusion and the country rocks resemble the trend observed for Li isotopes in an earlier study. Amphibole and feldspar display a clear trend from light boron in the inner nepheline syenitic part of the intrusion (?11B = -20‰ and -17‰ for amphibole and feldspar, respectively) through intermediate values in the outer augite syenites (?11B = -10‰ and -6‰ for amphibole and feldspar, respectively) to heavy boron with ?11B = + 2‰ for amphibole and + 4‰ for feldspar in the country rock granites close to the contact with the intrusion. The values are interpreted to reflect the entry of meteoric fluids with heavy B along the intrusive contact.

Kaliwoda, Melanie; Marschall, Horst R.; Marks, Michael A. W.; Ludwig, Thomas; Altherr, Rainer; Markl, Gregor

2011-07-01

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Zircon ages of granitic gneisses from the Rhodope (N. Greece), determination of basement age and evidences for a cretaceous intrusive event  

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The Rhodope massif is one of the internal provinces of the Hellenides. This part of the alpine system is traditionally subdivided into the Upper Tectonic Unit and the Lower Tectonic Unit. The UTU is mainly composed of gneisses (ortho and para) and migmatites with occurrences of eclogites and marbles layers. The LTU is characterized by a thick horizon of undated marbles, low-grade calcschistes and orthogneisses. The NE dipping Nestos thrust that shows a top to the SW shearing juxtaposes these two units. The Rhodope massif recently gained attention because of the discovery of diamondiferous UHPM metasedimentary rocks (Kostopoulos et al., 2000). The age of the Rhodopian gneisses as well as the migmatitisation ages can provide important constraints on the pre-alpine evolution of this crustal segment and the geological context of the UHPM event. We dated some basement orthogneisses and granitic bodies by the single zircon Pb-Pb evaporation method. Crystal morphologies confirm the igneous origin of the zircons. Therefore the obtained ages are interpreted as intrusion ages. It appears that the basement ages cluster between 270 and 300 Ma and are homogeneous trough all the Greek Rhodope (including Thassos island) from the Strymon valley to the Evros River at the Turkish border. These ages are similar to those of the Pelagonian zone basement (Anders et al., 2002). One important result is that there is no difference between the basement intrusion ages of the UTU and the LTU. Granitic bodies of the UTU, which were also affected by the regional deformation, such as the southern limb of the Paranesti granite and a mylonitic leucogranite of the eastern Rhodope, were dated at ca. 130 Ma. This implies that an intrusive event took place in the (whole?) Rhodope during the early Cretaceous. In the Xanthi area, another granitic gneiss gave a zircon age of 140 +/- 3 M. (Reischmann and Kostopoulos, 2002) and ages of ca. 139 Ma were obtained on metamorphic rims of zircons (Liati and Gebauer, 2001). Our new data indicate a possible relationship between the widespread migmatitisations, the granite intrusions and the early Cretaceous or late Jurassic UHPM event. References: Anders, B., Reischmann, T. and Poller, U. (2002). Geochim. Cosmochim. Acta 66, A19 (abstr.). Kostopoulos, D.K.,Ionnadis, N.M. and Sklavounos, S.A. (2000), Int. Geol. Rev. 42, 545--554. Liati, A and Gebauer, D. (2001), J.Conf. Abs. 6, 315. Reischmann, T. and Kostopoulos, D.K. (2002). Geochim. Cosmochim. Acta 66, A633.

Turpaud, P.; Reischmann, T.

2003-04-01

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Evidence for exhumation of a granite intrusion in a regional extensional stress regime based on coupled microstructural and fluid inclusion plane studies - An example from the Velence Mts., Hungary  

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A new approach, the fluid inclusion plane technique coupled with fluid inclusion microthermometry and field measurements have been applied to demonstrate the exhumation and relative vertical displacements of an allochthonous, Permian granite intrusion (Velence Mts.) which was situated in the Middle Triassic at the western end of the Neotethys rift system. The pressure and the temperature conditions during the Permian fluid flow (>350 °C and ˜2 kbar) in the granite were considerably higher than during the Triassic fluid flow (<250 °C and ˜0.5 kbar), which indicates the exhumation of the granite intrusion in a primarily extensional tectonic stress regime. The fluid inclusion planes with NE-SW and NW-SE strike prove stress field permutation that can be explained by the exhumation of the host granite during the Middle Triassic fluid flow. It is suggested that the exhumation of the Velence Mts. along with the regional fluid flow can be connected to the passive pre-rift phase of the northern Adriatic Block, during the Middle-Late Triassic. The variations in homogenization temperatures of Triassic regional fluid inclusion assemblages between the blocks of the granite, as well as variations in the fluid inclusion plane orientations, suggest a post-Triassic vertical segmentation and relative block rotation of the granite.

Benkó, Zsolt; Molnár, Ferenc; Lespinasse, Marc; Váczi, Tamás

2014-08-01

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The Oulad Ouaslam Variscan granitic pluton (Jebilets Massif, Southwestern Moroccan Meseta): A forcibly emplaced laccolithic intrusion characterized by its magnetic and magmatic fabrics  

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The study of the magmatic fabrics of the Oulad Ouaslam Variscan granitic pluton, based on the Anisotropy of Magnetic Susceptibility technique, allows us to propose that this 30 km long laccolith corresponds to a forcibly emplaced intrusion which proceeded from west to east into its country rock of Carboniferous metapelites. The fact that the magmatic fabrics measured in this pluton are obliquely cut, in the southwestern part, by solid-state structures (cleavage, shear bands) related to the regional main phase of deformation shows that the pluton was emplaced before this phase. Consequently, the tectonic control of this emplacement appears to have been much less important than it was suggested in the previous interpretations which considered, on the basis of the study of the solid-state fabrics, a syn-tectonic emplacement of this granite, possibly linked to a sinistral NNW-SSE shear zone. Our results contribute to the definition of a new framework for the tectonic history of this part of the Variscan chain.

Boummane, M. H.; Olivier, Ph.

2007-01-01

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Cryogenian transpression and granite intrusion along the western margin of Rodinia (Mt. Abu region): Magnetic fabric and geochemical inferences on Neoproterozoic geodynamics of the NW Indian block  

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The Mt. Abu batholith in NW India comprises variably deformed porphyritic, granophyric to medium-grained granites and granite gneisses. They are intruded by rhyolitic and mafic dykes; the latter also mark the terminal magmatic phase in this batholith. Granitoids and rhyolitic dykes form a coherent group; petrographic and geochemical characteristics indicate high level intrusion of felsic magma generated from high temperature melting of a lower crustal source. Geochemical similarity, spatial contiguity and coeval emplacement (766 to 763 Ma) of Mt. Abu granitoids with the Neoproterozoic (770 to 750 Ma) Malani Igneous Suite (MIS) underline that both are related to the same thermal event with Mt. Abu batholith as southeastern continuity of the MIS. Anisotropy of magnetic susceptibility data shows parallel fabric orientation in all granitoid types (NE trend, steep SW dip) as well as in a prominent shear zone (Delwara Shear Zone) along the western margin of the batholith with continued deformation during and after the emplacement of granitic magma as inferred from deformation of late-stage mafic dykes. Including coeval shear zones and associated melting in the region NE of Mt. Abu shear-controlled magma generation and ascent along a > 50 km NE trending corridor (Mt. Abu-Sirohi fault zone) is inferred. Structural elements and microstructural criteria (steep foliations, vertical lineations, dextral displacement) indicate a transpressional setting for this Cryogenian event. In regional geodynamic context the Mt. Abu-MIS can be regarded as northeastern continuation of the Neoproterozoic (800-700 Ma) magmatic belt extending from northern Madagascar, the Seychelles into NW India. This magmatic belt, located along the western margin of supercontinent Rodinia, was formed during eastward subduction of the Mozambique Ocean. Transpressional forces responsible for shaping the structural architecture in the Mt. Abu-Sirohi region were most likely induced during closure of the Mozambique Ocean and related translation of the Marwar craton.

de Wall, Helga; Pandit, Manoj K.; Dotzler, Ramona; Just, Jana

2012-07-01

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Contrasting fluid/rock interaction between the Notch Peak granitic intrusion and argillites and limestones in western Utah: evidence from stable isotopes and phase assemblages  

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The Jurassic Notch Peak granitic stock, western Utah, discordantly intrudes Cambrian interbedded pure limestones and calcareous argillites. Contact metamorphosed argillite and limestone samples, collected along traverses away from the intrusion, were analyzed for ??18O, ??13C, and ??D. The ??13C and ??18O values for the limestones remain constant at about 0.5 (PDB) and 20 (SMOW), respectively, with increasing metamorphic grade. The whole rock ??18O values of the argillites systematically decrease from 19 to as low as 8.1, and the ??13C values of the carbonate fraction from 0.5 to -11.8. The change in ??13C values can be explained by Rayleigh decarbonation during calcsilicate reactions, where calculated {Mathematical expression} is about 4.5 permil for the high-grade samples and less for medium and low-grade samples suggesting a range in temperatures at which most decarbonation occurred. However, the amount of CO2 released was not anough to decrease the whole rock ??18O to the values observed in the argillites. The low ??18O values close to the intrusion suggest interaction with magmatic water that had a ??18O value of 8.5. The extreme lowering of ??13C by fractional devolatilization and the lowering of ??18O in argillites close to the intrusion indicates oxgen-equivalent fluid/rock ratios in excess of 1.0 and X(CO2)F of the fluid less than 0.2. Mineral assemblages in conjunction with the isotopic data indicate a strong influence of water infiltration on the reaction relations in the argillites and separate fluid and thermal fronts moving thru the argillites. The different stable isotope relations in limestones and argillites attest to the importance of decarbonation in the enhancement of permeability. The flow of fluids was confined to the argillite beds (argillite aquifers) whereas the limestones prevented vertical fluid flow and convective cooling of the stock. ?? 1984 Springer-Verlag.

Nabelek, P.I.; Labotka, T.C.; O'Neil, J.R.; Papike, J.J.

1984-01-01

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Occurrence of ? 1Ga Jambugoda granite in Aravali Craton, a tectonic significance  

International Nuclear Information System (INIS)

The granites and gneisses of southern parts of Aravali Mountain Belt (AMB), NW India, are referred to as Godhra Granite and Gneiss and have an intrusive relationship with the surrounding metasedimentary rocks, which belong to the Lunavada Group in the north and Champaner Group in the south (Fig.1). These two groups comprise the younger part of the Aravali Supergroup. Two granite varieties, coarse and fine, are commonly observed and occupy an area of about 5000 km2. The coarse-grained granite is grayish and porphyritic in nature. It consists phenocrysts of feldspar and quartz, and abundant biotite. Fine grained granite is commonly found to occur in association with coarse grained granite; at places, the former is seen to have an intrusive relationship with the latter. Available age data information is scant, and is mainly based on Rb-Sr wholerock methods. In spite of these limitations, the available data indicate that the granitoids might comprise two or more age groupings. Published Rb-Sr ages for various plutons include Mt. Abu granite 735 ± 15 Ma , Godhra granite 955 ± 20 Ma, Sendra granite 966 ± 250 Ma, and Ambaji granite ?1228 Ma. Godhra granite assumes importance due to its proximity to the Son-Narmada North Fault (SnF) and is believed to have formed during the growth of the Indian shield in Mesoproterozoic times. Further ?1 Ga granites play a vital role in global tectonics therefore an attempt has been made to decipher various episodes of grani decipher various episodes of granitic evolutionary events in these parts of the subcontinent

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The Veikkola granite area in southern Finland: emplacement of a 1.83-1.82 Ga plutonic sequence in an extensional regime  

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Full Text Available Four granite intrusions and coeval small enderbite intrusions, belonging to the lateorogenic (1850–1820 Ma magmatism of the Svecofennian orogeny, are described in the Veikkola area of southern Finland. The granites are leucocratic, heterogeneous and characterizedby abundant garnet. The oldest granite is layered whereas the younger ones are more homogeneous. Geochemically the granites are peraluminous and have high contents of SiO2 (71–76 wt.%. Their major and minor element composition varies significantly but the REE patterns are fairly similar. Garnet mainly crystallized from melt but some garnet in the granites may be restitic. Garnet composition is relatively constant implying slow equilibration with the melt. In addition to garnet-bearing felsic layers in the oldest granite, the granites are crosscut by garnet-bearing dikes and veins. The layers, dikes and veins are higher in REE and Fe/Mg than the host granites and are considered partial melts from the granites. The abundant garnet in the felsic layers, dikes and veins crystallized from melt. Thermobarometry calculations indicate 3.5 – 5 kbar and ~650–700 °C estimates for crystallization of the felsic layers in the oldest granite whereas the host granite yields ~1.5 kbar higher pressure. The granites were probably derived by dehydration melting of layered, metagreywacke-dominated rocks. Melting was fluid-absent both during generation of the granites and during formation of the felsic layers, dikes and veins. The oldest granite (1850 Ma was emplaced at mid-crustal depth before extensional deformation. Layering in the oldest granite is regarded as the result of deformation-induced remelting of the host granite at a higher crustal level, during protracted extension and progressive regional metamorphism. The otherthree granites and the enderbite were emplaced at a late stage of extension, at or close to the peak of metamorphism (1.83 – 1.82 Ga.

Matti Kurhila

2008-01-01

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Mesoproterozoic rapakivi granites of the Rondonia Tin Province, southwestern border of the Amazonian craton, Brazil-I. Reconnaissance U-Pb geochronology and regional implications  

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Rapakivi granites and associated mafic and ultramafic rocks in the Rondonia Tin Province, southwestern Amazonian craton, Brazil were emplaced during six discrete episodes of magmatism between ca 1600 and 970 Ma. The seven rapakivi granite suites emplaced at this time were the Serra da Providencia Intrusive Suite (U-Pb ages between 1606 and 1532 Ma); Santo Antonio Intrusive Suite (U-Pb age 1406 Ma); Teotonio Intrusive Suite (U-Pb age 1387 Ma); Alto Candeias Intrusive Suite (U-Pb ages between 1346 and 1338 Ma); Sao Lourenco-Caripunas Intrusive Suite (U-Pb ages between 1314 and 1309 Ma); Santa Clara Intrusive Suite (U-Pb ages between 1082 and 1074 Ma); and Younger Granites of Rondonia (U-Pb ages between 998 and 974 Ma). The Serra da Providencia Intrusive Suite intruded the Paleoproterozoic (1.80 to 1.70 Ga) Rio Negro-Juruena crust whereas the other suites were emplaced into the 1.50 to 1.30 Ga Rondonia-San Ignacio crust. Their intrusion was contemporaneous with orogenic activity in other parts of the southwestern Amazonian craton, except for the oldest, Serra da Providencia Intrusive Suite. Orogenic events coeval with emplacement of the Serra da Providencia Intrusive Suite are not clearly recognized in the region. The Santo Antonio, Teotonio, Alto Candeias and Sao Lourenco-Caripunas Intrusive Suites are interpreted to represent extensional anorogenic magmatism associated with the terminal stages of the Rondonian-San Ignacio orogeny. At least the Sao Lourenco-Caripunas rapakivi granites and coeval intra-continental rift sedimentary rocks may, in contrast, represent the products of extensional tectonics and rifting preceding the Sunsas/Aguapei orogeny (1.25 to 1.0 Ga). The two youngest rapakivi suites, the Santa Clara Intrusive Suite and Younger Granites of Rondonia, seemingly represent inboard magmatism in the Rondonian-San Ignacio Province during a younger episode of reworking in the Rio Negro-Juruena Province during the waning stages of the collisional 1.1 to 1.0 Ga Sunsas/Aguapei orogeny. The six intra-plate rapakivi granite episodes in the southwestern part of the Amazonian craton form three broad periods of anorogenic magmatism that have age-correlative events composed of similar rocks and geologic environments in eastern Laurentia and Baltica, although the exact timing of magmatism appears slightly different. Recognition of lithologic and chronological correlations between various cratons provide important constraints to models explaining the interplay between rapakivi granite magmatism and deep crustal evolution of an early Mesoproterozoic supercontinent. They are, furthermore, important to plate tectonic models for the assembly, dispersal and reassembly of Amazonia, Laurentia and Baltica in the Mesoproterozoic and Neoproterozoic.

Bettencourt, J.S.; Tosdal, R.M.; Leite, W.B., Jr.; Payolla, B.L.

1999-01-01

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Extreme U-Th disequilibrium in rift-related basalts, rhyolites and granophyric granite and the timescale of rhyolite generation, intrusion and crystallization at Alid volcanic center, Eritrea  

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Rhyolite pumices and co-erupted granophyric (granite) xenoliths yield evidence for rapid magma generation and crystallization prior to their eruption at 15.2 ?? 2.9 ka at the Alid volcanic center in the Danikil Depression, Eritrea. Whole-rock U and Th isotopic analyses show 230 Th excesses up to 50% in basalts <10 000 years old from the surrounding Oss lava fields. The 15 ka rhyolites also have 30-40% 230Th excesses. Similarity in U-Th disequilibrium, and in Sr, Nd, and Pb isotopic values, implies that the rhyolites are mostly differentiated from the local basaltic magma. Given the (230 Th/232Th) ratio of the young basalts, and presumably the underlying mantle, the (230Th/232Th) ratio of the rhyolites upon eruption could be generated by in situ decay in about 50 000 years. Limited (???5%) assimilation of old crust would hasten the lowering of (230Th/232Th) and allow the process to take place in as little as 30 000 years. Final crystallization of the Alid granophyre occurred rapidly and at shallow depths at ???20-25 ka, as confirmed by analyses of mineral separates and ion microprobe data on individual zircons. Evidently, 30 000-50 000 years were required for extraction of basalt from its mantle source region, subsequent crystallization and melt extraction to form silicic magmas, and final crystallization of the shallow intrusion. The granophyre was then ejected during eruption of the comagmatic rhyolites. ?? 2006 Oxford University Press.

Lowenstern, J.B.; Charlier, B.L.A.; Clynne, M.A.; Wooden, J.L.

2006-01-01

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Genetic relationship between L granite body and 3701 uranium deposit  

International Nuclear Information System (INIS)

The ore deposit occurs in carbonate rocks situated in the exocontact zone (0 - 120 m) with the L granite body. The mineralization is hosted by argillaceous limestone of the middle Devonian Yingtang Formation. The ore bodies are in lenticular or stratifed form. The ores are fine vein-type and disseminated type. Four stages of mineralization in the deposit are recognized. Industrial mineral is pitchblende which occurs as micro-impregnation and micro-vein in the calcite, and fills or replaces its associated minerals. Gangue minerals are chiefly calcite, pyrite, galena, sphalerite, chalcopyrite and tennantite etc. The host rocks of the ore-veins show weak hydrothermal alterations with plane and linear distribution. The L granite body with an area of 238 km2 is a single-stage intrusive batholith which mainly consists of coarse-medium grained biotite granites. Because the urnium mineralization age (65.0 - 30.7 Ma) is much younger than that of the L granite (318 -202 Ma), it may be considered that the deposit is genetically not related to activity of the L granitic magma. However, the granitic rocks may play an important role in the formation of the 3701 uranium deposit in following hands: providing a large number of uranium and lead; providing minor amounts of surfur, carbon and trace elements; forming impermeable basement to promote the accumulation of uranium-bearing solution; providing an additional heat source for heating ore-bearing solution and its convectiting ore-bearing solution and its convective circulation

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Petrography and geochemistry of the topaz-bearing granite stocks in Artjärvi and Sääskjärvi, western margin of the Wiborg rapakivi granite batholith  

OpenAIRE

The Artjärvi and Sääskjärvi granite stocks at the western margin of the Wiborg rapakivi batholith are multiphase rapakivi granite intrusions in which the most evolved phase is topaz-bearing granite. The Artjärvi stock is composed of porphyritic and even-grained biotite granite and even-grained topaz granite, and the Sääskjärvi stock comprises even-grained biotite granite and porphyritic topazgranite. The granites are metaluminous to peraluminous A-type granites, showing within-plate (...

Sari Lukkari

2002-01-01

38

Uranium and thorium distribution in the Contreberg granite, Darling  

International Nuclear Information System (INIS)

Two plutons of young granite, intrusive into other members of the Cape Granite suite, occur to the northwest and southeast of Darling, Western Cape Province. In spite of their comparable temporal and structural positions in the granite series, the two granites differ considerably in textural and compositional properties, making a comparative study desirable. Thus the Contreberg granite was compared with the Klipberg granite. The average radioelement content was lower in the Contreberg granite than in the Klipberg granite. For the Contreberg granite the average values are 6,0 ppm U3O8 and 28 ppm ThO2

39

Timing, petrogenesis and tectonic setting of the Late Paleozoic gabbro-granodiorite-granite intrusions in the Shalazhashan of northern Alxa: Constraints on the southernmost boundary of the Central Asian Orogenic Belt  

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The Late Paleozoic tectonic setting and location of the southernmost boundary of the Central Asian Orogenic Belt (CAOB) with respect to the Alxa Block or Alxa-North China Craton (ANCC) are debated. This paper presents new geochronological, petrological, geochemical and zircon Hf isotopic data of the Late Paleozoic intrusions from the Shalazhashan in northern Alxa and discusses the tectonic setting and boundary between the CAOB and ANCC. Using zircon U-Pb dating, intrusions can be broadly grouped as Late Carboniferous granodiorites (~ 301 Ma), Middle Permian gabbros (~ 264 Ma) and granites (~ 266 Ma) and Late Permian granodiorites, monzogranites and quartz monzodiorites (254-250 Ma). The Late Carboniferous granodiorites are slightly peraluminous and calcic. The remarkably high zircon Hf isotopes (?Hf(t) = + 6-+ 10) and characteristics of high silica adakites suggest that these granodiorites were mainly derived from "hot" basaltic slab-melts of the subducted oceanic crust. The Middle Permian gabbros exhibited typical cumulate textures and were derived from the partial melting of depleted mantle. The Middle Permian granites are slightly peraluminous with high-K calc-alkaline and low ?Hf(t) values from - 0.9 to + 2.9. These granites were most likely derived from juvenile materials mixed with old crustal materials. The Late Permian granodiorites, monzogranites and quartz monzodiorites are characterized as metaluminous to slightly peraluminous, with variable Peacock alkali-lime index values from calc-alkalic to alkali-calcic. These rocks were mainly derived from juvenile crustal materials, as evidenced by their high ?Hf(t) values (+ 3.3 to + 8.9). The juvenile sources of the above intrusions in the Shalazhashan are similar to those of the granitoids from the CAOB but distinct from the granitoids within the Alxa Block. These findings suggest that the Shalazhashan Zone belongs to the CAOB rather than the Alxa Block and that its boundary with the Alxa block can be regarded as the southernmost boundary of the CAOB. The recognition of Late Carboniferous typical adakite magmatism in the region provides evidence for the subduction of the oceanic crust of the CAOB. The Middle-Late Permian magmatisms (266-250 Ma) display a bimodal association with high-K calc-alkaline features and are interpreted as forming in a post-collision setting. These studies, by interaction of regional geology, provide new constraints on the tectonic evolution of the southern CAOB during the Late Paleozoic and the location of the southernmost margin of the CAOB.

Shi, Xingjun; Wang, Tao; Zhang, Lei; Castro, Antonio; Xiao, XuChang; Tong, Ying; Zhang, Jianjun; Guo, Lei; Yang, Qidi

2014-11-01

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Geochemistry of granitic rocks in Indian cratons, a prelude for uranium exploration  

International Nuclear Information System (INIS)

Peninsular India constitutes Archaean continental nuclei, supercrustals episodic granitic intrusive and effusives, mobile belts and all are welded together by rifts and sutures. The episodic nature of granitic magmatism is well represented with peak ages recorded around 470, 1100, 1800, 2200, 2500, 3100, 3300, 3500 Ma (1) and played a vital role in crustal growth of Peninsular Indian shield similar to the world wide crustal evolution during the Proterozoic times. These cratonic blocks are stabilized and formed basement for Proterozoic basins. This granite related magmatic events include juvenile granites and reactivated gneisses in several parts of the shield areas. These accretions brought metals from mantle and also helped in their remobilization from early formed crustal blocks. Large Ion Lithoplile elements including U, Th and K thus added to the crust, later formed the potential source for QPC, unconformity related uranium deposits. In this paper, geochemical and petrogenetic evolution of granites of Dharwar, Basta, Sighbhum and Bundelkhand cratons of various ages are presented with an emphasis to narrow down the target areas for uranium exploration. The late phase granites of crustal derived with A and S type characters occurring as younger variants in the craton are favourable horizons for uranium exploration. (author)

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El Granito Calasuya: un intrusivo alcalifeldespático postcolisional en el batolito de Sierra Norte-Ambargasta, Córdoba The Calasuya Granite: a postcollisional alkalifeldspar intrusive in the Sierra Norte-Ambargasta batholith, Córdoba province  

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Full Text Available La zona central del extenso batolito Sierra Norte-Ambargasta, en el bloque más oriental de las Sierras Pampeanas orientales, está representada por granitoides de arco magmático tipo I (granodioritas, monzogranitos, pórfidos dacíticos y riolíticos denominados serie La Isla - Cerro de los Burros, intruidos por cuerpos menores félsicos postcolisionales, químicamente más evolucionados (denominados unidades Puesto de Los Caminos y Cerro Baritina, todos pertenecientes al Neoproterozoico- Cámbrico inferior. Nueva información geológica y geoquímica de la región centro-oriental del mismo batolito permitió identificar un plutón de composición alcalifeldespática, denominado Granito Calasuya, el primero de esta naturaleza en el batolito. Su mineralogía distintiva la constituyen la composición albítica de la plagioclasa magmática (An The central-western portion of the extended Sierra Norte-Ambargasta batholith, in the easternmost block of the eastern Sierras Pampeanas, is largely characterized by pre-collisional I-type magmatic arc granitoids (granodiorites, monzogranites, dacite and rhyolite porphyries named La Isla - Cerro de los Burros series, and by smaller sized postcollisional felsic intrusives of higher evolved chemistry (named Puesto de los Caminos and Cerro Baritina units, all of which crystallized along the Late Proterozoic -Lower Cambrian time span. New geological and geochemical data from the central and oriental areas of the batholith allowed to identify an intrusive body of alkalifeldspar composition (the Calasuya granite, the first of its type in the batholith. Its distinctive mineralogy is highlighted by the albitic composition of magmatic plagioclase (molar An < 6 %, the high #Fe (0.97 of accessory biotite, the presence of accessory late magmatic fluorite, and the conspicuous postmagmatic albitization process. Its highly fractionated nature is shown by high SiO2 and low CaO, MgO, TiO2, MnO and Fe2O3(t contents, also evidenced by Rb, Y and Th enrichment, and Sr, Ba and Zr depletion. The total REE content is low, showing asymmetric spider-type diagrams with predominance of LREE over HREE; positive Ce/Ce* anomalies as well as deep negative Eu/Eu* are also remarkable characteristics of this pluton. The Zr+Nb+Ce+Y versus Ga/Al ratio unequivocally displays its I-type highly fractionated signature. According to some field and geochemical patterns, the Calasuya granite gathers similarities with granites of the Puesto de los Caminos unit, which groups highly evolved postcollisional epizonal granitoids. Notwithstanding, despite these evidences, REE patterns and its accessory mineralogy reveal more affinity with the Cerro Baritina unit which is represented by Lower Cambrian syenogranitic aplites, interpreted together with other highly evolved granitoids as indicators of the Pampean orogeny closure.

Javier Elortegui Palacios

2008-09-01

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Geochronology of the Schurwedraai Alkali Granite and associated nepheline syenite and implications for the origin of the Vredefort structure  

International Nuclear Information System (INIS)

New Rb-Sr and Pb-Pb whole-rock and mineral age determinations indicate ages close to 2,2 Ga for the Schurwedraai Alkali Granite and associated nepheline syenite from the northwestern part of the collar around the Vredefort dome. The 2,2 Ga age is consistent with existing age data from another intrusion in the rim of the Vredefort structure and represents a significant upward revision of the age previously accepted for the Schurwedraai Granite. As such it removes the important constraint imposed by the synchronicity of the alkali magmatism and the Vredefort event on meteorite impact theories for the origin of the Vredefort structure. The younger overprint at approximately 2050 Ma can be interpreted to reflect either the age of the Vredefort event and associated deformation/alteration of the alkali intrusives or a thermal overprint related to the emplacement of the Bushveld Complex at this time. 48 refs., 9 figs., 2 tabs

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Structure of the Beariz granite (Ourense, Galicia)  

OpenAIRE

The geological map, cross-sections and structural analysis of the Beariz granite are presented. The Geometric and structural characteristics of this intrusive body are in good agreement with a sinkynematic emplacement within a strike-slip shear zone

Gonza?lez Cuadra, P.; Di?az Garci?a, F.; Cuesta Ferna?ndez, A.

2006-01-01

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Neoproterozoic granitic activities in the Xingdi plutons at the Kuluketage block, NW China: Evidence from zircon U-Pb dating, geochemical and Sr-Nd-Hf isotopic analyses  

Science.gov (United States)

Neoproterozoic igneous rocks are widely distributed in the Kuluketage block along the northern margin of the Tarim Craton. However, the published literature mainly focuses on the ca. 800 Ma adakitic granitoids in the area, with the granites that intrude the 735-760 Ma mafic-ultramafic rocks poorly studied. Here we report the ages, petrography and geochemistry of two granites in the Xingdi mafic-ultramafic rocks, in order to construct a new view of the non-adakitic younger granites. LA-ICP-MS zircon U-Pb dating provided weighted mean 206Pb/238U ages of 743.0 ± 2.5 Ma for the No.I granite (G1) and 739.0 ± 3.5 Ma for the No.II granite (G2). A clear core-rim texture of similar age and a high zircon saturation temperature of ca. 849 ± 14 °C were observed for the No.I granite; in contrast, G2 has no apparent core-rim texture but rather inherited older zircons and a lower zircon saturation temperature of ca. 763 ± 17 °C. Geochemical analysis revealed that G1 is an alkaline A-type granite and G2 is a high-K calc-alkaline I-type granite. Both granites share similar geochemical characteristics of arc-related magmatic rocks and enriched Sr-Nd-Hf isotopes, likely due to their enriched sources or mixing with enriched magma. Whereas G1 and its host mafic rocks form typical bimodal intrusions of the same age and similar Sr-Nd-Hf isotope compositions, G2 is younger than its host mafic rocks and its Sr-Nd-Hf isotope composition indicates a lower crust origin. Although they exhibit arc-related geochemical features, the two granites likely formed in a rift setting, as inferred from thier petrology, Sr-Nd-Hf isotopes and regional tectonic evolution.

Cao, Xiaofeng; Lü, Xinbiao; Yuan, Qian; Wang, Xiangdong; Liu, Hong; Shen, Wen

2014-12-01

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Petrogenesis of the gold bearing Zarrin granite  

OpenAIRE

Zarrin granite intrusion is located in the Central Iran, to west of Chapedoni and Posht-e-Badam faults. It consists of three separate outcrops situated at the northern end of a long mountain range, which is comprised of Mesozoic rocks. Lithologically the intrusion contains granites as well as, gneisses (?) and aplites. Petrographic and geochemical evidence strongly suggest that they are cogenetic. High aluminum contents and other characteristics of these rocks, as well as petrographic evidenc...

Valizadeh, Mohammed-vali; Omrani, Jafar; Moritz, Robert

2002-01-01

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Interacción termal entre magmas graníticos laramídicos y rocas encajonantes mesoproterozoicas: Historia de enfriamiento de intrusivos de la Sierrita Blanca, NW Sonora / Thermal interaction between Laramide granitic magmas and Mesoproterozoic country rocks: thermochronology of intrusives of Sierrita Blanca, NW Sonora  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: Spanish Abstract in spanish Un estudio termocronológico semi-cuantitativo, combinando técnicas geocronológicas de U-Pb y 40Ar/39Ar, permitió evaluar el fenómeno de cristalización y posterior enfriamiento del cuerpo intrusivo laramídico Sierrita Blanca, así como el efecto termal del mismo en las rocas encajonantes mesoproterozo [...] icas (~1.1 Ga) denominadas granito Murrieta. La disparidad en edades U-Pb en zircones para dos muestras del granito Sierrita Blanca (72.6 ± 1.2 Ma y 69.7 ± 1.0 Ma) pudiera estar asociada al enfriamiento más rápido del magma en la zona de contacto con el encajonante mesoproterozoico; pero no se puede descartar que esta unidad granítica esté compuesta por múltiples intrusiones de composición similar y relativamente espaciadas en el tiempo. Las edades de 40Ar/39Ar (biotita y feldespato potásico) de la muestra de granito más cercana al encajonante son también más antiguas que las de la roca recolectada en la zona más interna del intrusivo. El enfriamiento inicial del granito es relativamente rápido desde la temperatura de cierre del zircón hasta la de la biotita (~36-32°C/Ma), para que posteriormente se pase a enfriamientos relativamente lentos desde la biotita hasta el feldespato potásico (~10-9°C/Ma). Estos enfriamientos del granito Sierrita Blanca son comparables, aunque quizá un poco más lentos, a los estimados para otros granitoides laramídicos del NW de México. Tres muestras del granito mesoproterozoico Murrieta, recolectadas a diferentes distancias del intrusivo laramídico, fueron fechadas por U-Pb en zircones (~1.1 Ga), reiterándose la resistencia de esta sistemática a los efectos termales. Sin embargo, se aprecia la presencia de zircones con pérdida evidente de Pb, que se asocian a la exposición de estas rocas al calor y/o fuidos relacionados a la intrusión laramídica, siendo este efecto más pronunciado en la roca recolectada cerca del contacto con el granito. Este efecto de reajuste isotópico es mucho más marcado para la sistemática de 40Ar/39Ar en biotita y feldespato potásico, al encontrarse estos minerales totalmente reajustados a edades laramídicas. Las estimaciones de enfriamiento post-reajuste isotópico entre biotita y feldespato potásico (~18-15°C/Ma) de las rocas encajonantes son, en cierto modo, armónicas con los enfriamientos estimados para estos mismos minerales en el granito laramídico. Esto sugiere que el enfriamiento general del área de la Sierrita Blanca, después de la intrusión granítica lara-mídica, fue coherente, fnalizando este en las zonas más internas del intrusivo. Por último, destacar que el pulso magmático miocénico presente en la Sierrita Blanca no ha causado ningún efecto termal apreciable en las rocas graníticas cretácicas o mesoproterozoicas. Abstract in english A semi-quantitative thermochronological study, combining U-Pb and 40Ar/39Ar geochronology, has allowed assessment of the crystallization and cooling history of the Laramide Sierrita Blanca granite as well as the thermal effects resulting from the intrusion into the Mesoproterozoic host rocks (~1.1 G [...] a Murrieta granite). The U-Pb zircon age discrepancy between two samples of the Sierrita Blanca granite (72.6 ± 1.2 Ma and 69.7 ± 1.0 Ma) could be explained by a process of faster magma cooling in the contact zone with the host Murrieta granite. However, that the Sierrita Blanca granitic unit was made up of multiple intrusions of similar compositions emplaced relatively close in time cannot be discarded. The 40Ar/39Ar ages of both biotite and K-feldspar for the granite collected close to the contact are also signifcantly older than the ages for the sample collected in a more internal zone of the intrusion. The initial cooling of the Sierrita Blanca granite was fairly fast and monotonous from the closure temperature of zircon to that of biotite (~36-32°C/Ma). Subsequently, the cooling of these Laramide rocks became relatively slow (~10-9°C/Ma) between the closure temperature of biotite and K-f

Mónica A., Enríquez-Castillo; Alexander, Iriondo; Gabriel, Chávez-Cabello; Michael J., Kunk.

2009-12-01

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El Granito Calasuya: un intrusivo alcalifeldespático postcolisional en el batolito de Sierra Norte-Ambargasta, Córdoba / The Calasuya Granite: a postcollisional alkalifeldspar intrusive in the Sierra Norte-Ambargasta batholith, Córdoba province  

Scientific Electronic Library Online (English)

Full Text Available SciELO Argentina | Language: Spanish Abstract in spanish La zona central del extenso batolito Sierra Norte-Ambargasta, en el bloque más oriental de las Sierras Pampeanas orientales, está representada por granitoides de arco magmático tipo I (granodioritas, monzogranitos, pórfidos dacíticos y riolíticos denominados serie La Isla - Cerro de los Burros), int [...] ruidos por cuerpos menores félsicos postcolisionales, químicamente más evolucionados (denominados unidades Puesto de Los Caminos y Cerro Baritina), todos pertenecientes al Neoproterozoico- Cámbrico inferior. Nueva información geológica y geoquímica de la región centro-oriental del mismo batolito permitió identificar un plutón de composición alcalifeldespática, denominado Granito Calasuya, el primero de esta naturaleza en el batolito. Su mineralogía distintiva la constituyen la composición albítica de la plagioclasa magmática (An Abstract in english The central-western portion of the extended Sierra Norte-Ambargasta batholith, in the easternmost block of the eastern Sierras Pampeanas, is largely characterized by pre-collisional I-type magmatic arc granitoids (granodiorites, monzogranites, dacite and rhyolite porphyries named La Isla - Cerro de [...] los Burros series), and by smaller sized postcollisional felsic intrusives of higher evolved chemistry (named Puesto de los Caminos and Cerro Baritina units), all of which crystallized along the Late Proterozoic -Lower Cambrian time span. New geological and geochemical data from the central and oriental areas of the batholith allowed to identify an intrusive body of alkalifeldspar composition (the Calasuya granite), the first of its type in the batholith. Its distinctive mineralogy is highlighted by the albitic composition of magmatic plagioclase (molar An

Javier, Elortegui Palacios; Raúl, Lira; Fernanda, Poklepovic; Michael J., Dorais.

2008-09-01

48

P-T path fluid evolution in the Gross Spitzkoppe granite stock, Namibia  

OpenAIRE

The Gross Spitzkoppe granite stock (GSS) is a zoned 30 km^2 epizonal intrusion that consists of three main granites: 1) medium-grained biotite granite (marginal), 2) a coarse-grained biotite granite, and 3) a central, porphyritic granite. The stock contains pegmatites as banded marginal stockscheiders and isolated pockets composed of large alkali feldspar and quartz, dark mica, interstitial fluorite, and euhedral topaz and beryl crystals. In the porphyritic granite there are local wolframite-...

Stephen Frindt; Matti Poutiainen

2002-01-01

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Petrophysical and geochemical characteristics of late Variscan granites in the Karlovy Vary Massif (Czech Republic - implications for gravity and magnetic interpretation in shallow depths  

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Full Text Available The Karlovy Vary Massif (KVM in northern Bohemia is a composite granite body built up of Late Variscan biotite, two mica and lithium mica granites. We summarize the available whole-rock geochemical and petrological data and correlate them with similar information from three boreholes in the northern and southwestern parts of the Massif. The aim of the study was to determine whether various types of granites differ in their physical and chemical properties, and whether any differences in physical characteristics affect the accuracy of geophysical interpretation. In accord with the earlier studies, we distinguish two geochemically and petrophysically contrasting granite suites - the Older Intrusive Complex (OIC and Younger Intrusive Complex (YIC. The geochemical data show that the OIC and YIC granites differ significantly in the content of most major-element oxides (like SiO2, TiO2, FeO, Fe2O3tot, MgO and CaO. As to physical parameters, the granites differ markedly in magnetic susceptibilities and in the contents of radioactive elements (U and Th. From gravity and magnetic data we compiled a 22 km long geophysical profile, which crosses two of the three studied boreholes. For the construction of geological model along this profile, we used the data on the petrophysical properties measured on samples from the boreholes. Densities of the individual granite types are very similar to each other and thus the distinction of the OIC and YIC granites based on gravity data is not possible. Magnetic susceptibility differs markedly for the OIC and YIC granites in the drill logs, but absolute values of magnetic susceptibilities are very low. Modelling showed that neither gravimetry nor magnetometry are suitable methods for distinguishing between the different types of granites. On the other hand, it proved that the spatial distribution of individual granite intrusions does not affect the overall interpretation of the shape, size and depth of the whole granite body.

Blecha V

2012-07-01

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From explosive breccia to unidirectional solidification textures: magmatic evolution of a phosphorus- and fluorine-rich granite system (Podlesí, Krušné hory Mts., Czech Republic  

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Full Text Available The Podlesí granite stock in western Krušné hory Mts. represents the most highly fractionated part of the late Variscan Nejdek-Eibenstock pluton. Internal fabric of the stock has been studied in several boreholes up to 350 m deep. The stock is composed of two tongue-like bodies of albite-protolithionite-topaz granite (stock granite coalesced at depth, which were emplaced into Ordovician phyllite and biotite granite of younger intrusive complex (YIC of the Nejdek pluton. The uppermost part of the intrusion is bordered by a layer of marginal pegmatite (stockscheider up to 50 cm thick. Explosive breccia was found as an isolated block at the southwest contact of the stock. It is comprised of fragments of phyllite several millimetres to 5 cm in size cemented with fine-grained granitic matrix similar to the stock granite, but very fine-grained.
Within the uppermost 100 m, the stock granite is intercalated with several mostly flat-lying dykes of albite-zinnwaldite-topaz granite (dyke granite. Upper and lower contacts of the dykes are sharp, flat, but in detail slightly uneven. The thickest dyke (about 7 m outcrops in an old quarry. A prominent example of layering with unidirectional solidification textures (UST was found in the upper part of this major dyke. Individual Q-Afs laminae are separated by comb quartz layers and/or by layers of oriented fan-like zinnwaldite aggregates. A pegmatite-like layer with oriented megacrysts of Kfs up to 6 cm long was encountered in the uppermost part of the dyke. One thin layer of fine-grained quartz with oriented Kfs-megacrysts was found within the stock granite.
Post-magmatic processes, particularly greisenisation, developed only to a limited degree. The uppermost flat dyke of the dyke granite was partly greisenised into white quartz-rich (+topaz, Li-mica, wolframite greisen. Scarce thin, steep stringers of biotite greisen were encountered over the entire outcrop and in drilled parts of the stock granite and surrounding biotite granite.

Breiter K

2002-06-01

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Rb-Sr age determinations of pre-tectonic granites from the Southern Schwarzwald, SW Germany  

International Nuclear Information System (INIS)

Rb/Sr whole rock isochron ages for pre- and syn-tectonic intrusives have been determined. These are: the Rand Granite 365 +- 50 Ma; the Klemmbach-Schlaechtenhaus Granite 363 +- 19 Ma; Hauenstein Granite 330 +- 23 Ma. A whole rock-mineral isochron yields 329 +- 10 Ma for the age of intrusion of the Hauenstein Granite. This determination together with the intrusion age of the post-tectonic Schluchsee Granite (Brooks et al., 1968; Wendt et al., 1970) dates the cessation of activity in the Sudetan Phase of Tectonism (Metz and Rein, 1958) at 330 +- 10 Ma ago. (orig.)

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The petrogenesis of a wolframite-bearing greisen in the Vykmanov granite stock, Western Krušné hory pluton (Czech Republic  

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Full Text Available A wolframite-bearing greisen at Vykmanov, near Ostrov (Czech Republic occurs at the contact of a small granite stock belonging to the Late Variscan Younger Intrusive Complex (YIC of the Western Krušné hory/Erzgebirge pluton. The stock emerges as an outcrop of 0.8 × 0.3 km size from a hidden granite body in the eastern continuation of the Nejdek-Eibenstock granite massif. The lens-like greisen body consists mainly of quartz, topaz, protolithionite, and muscovite; it also contains wolframite (ferberite and native bismuth mineralization. It was formed by replacement of a medium-grained, equigranular, slightly porphyritic Li-F granite of the Karlovy Vary pluton characterized by weak postmagmatic albitization and pervasive muscovitization. The greisen is geologically and compositionally transitional between the Li-rich greisens in albite granites (e.g. with zinnwaldite such as at Krásno and the Li-poor greisens (e.g. phengite greisens at Gottesberg and P?ebuz associated with weakly albitized granites of the Younger Intrusive Complex. The Vykmanov greisen formed in a subsolidus stage of granite evolution by progressive alkali loss and fluorine metasomatism, leading to the formation of Li-mica quartz greisen subsequently replaced by topaz-quartz greisen at the granite/crystalline contact. These greisens were affected by late-stage muscovitization and argillitization (sericitization, the formation of clay minerals. The Li-Fe mica composition of the greisens corresponds to protolithionite (lithian siderophyllite and is similar to the composition of micas in the enclosing granite. The tungsten-bearing greisenization represents a postmagmatic episode in the development of the Krušné hory/Erzgebirge batholith, and is located at the eastern contact of highly evolved YIC granites of the Western Krušné hory pluton. The greisen formed from CO2 -poor hydrothermal solutions, at about 400 °C, which evolved from highly saline brines as evidenced by fluid inclusion studies. The geological situation suggests that the mineralizing fluids were mostly magmatic and were responsible for the tungsten-bismuth specialization of the greisens, whereas meteoric waters participated in mineralization during later stages.

Štemprok M

2005-09-01

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Magmatic constraints on localization of natural stone deposits in the Vehmaa rapakivi granite batholith, southwestern Finland  

OpenAIRE

The 1580–1570 Ma old Vehmaa rapakivi granite batholith was studied with the aim to define the geological constraints for localization of natural stone deposits in the batholith. The batholith comprises four roughly concentric granite intrusions from the margin inwards: pyterlite, coarse-grained porphyritic rapakivi granite and two types of medium-grained porphyritic rapakivi granite. Also porphyry aplite and even-grained rapakivi granite occur. The batholith has intruded as a succession of ...

Olavi Selonen; Carl Ehlers; Hannu Luodes; Fredrik Karell

2011-01-01

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The petrogenesis of late Neoproterozoic mafic dyke-like intrusion in south Sinai, Egypt  

Science.gov (United States)

New field, petrographical and geochemical studies are presented here for the late Neoproterozoic Rimm intrusion (˜15 km long) exposed in the southern Sinai Peninsula, Egypt in the northernmost Arabian-Nubian Shield (ANS). Field relations indicate that the Rimm intrusion is younger than the surrounding metamorphic rocks and calc-alkaline syn-tectonic granodiorite and it was not affected by regional metamorphism. The anorogenic peralkaline granite of Gebel Serbal crosscuts the Rimm intrusion. The Rimm intrusion is made up of several consanguineous rock types with gradational contacts. It is composed chiefly of pyroxene-hornblende gabbro, hornblende gabbro and minor quartz diorite. The chemical composition of the mafic minerals indicated that the studied rocks derived from calc-alkaline mafic magma. Geochemically, the studied rocks are characterized by enrichment in LILE relative to HFSE and LREE relative to HREE [(Ce/Yb)N = 4.50-6.36]. Quartz diorite display slightly concave HREE pattern and slightly negative Eu-anomaly [(Eu/Eu*)n = 0.91] which may be the result of fractionation of amphibole and plagioclase from the source melt, respectively. The Rimm intrusion evolved from mafic mantle magma into different type rocks by fractional crystallization with minor crustal contamination. The initial magma corresponds to pyroxene-hornblende gabbro and the crystallization of hornblende was caused by slight H2O increase in magma after crystallization of near-liquidus clinopyroxene and Ca-rich plagioclase. Amphiboles geobarometer indicate that the gabbroic rocks of the Rimm intrusion crystallized at pressures between 4.8 and 6.4 Kb, while quartz diorite crystallized at 1.3-2.1 Kb. Crystallization temperatures range between 800 and 926 °C for the gabbros and between 667 and 784 °C for the quartz diorite. The Rimm intrusion represents a post-orogenic phase formed during the crustal thinning and extension of the Arabian-Nubian Shield.

Azer, M. K.; Abu El-Ela, F. F.; Ren, M.

2012-08-01

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Petrochemistry and Rb-Sr isotopic study of bandal granites, district Kulu, Himachal Pradesh  

International Nuclear Information System (INIS)

Bandal granites which form the subject matter of the present study occur as a concordant body of batholithic size and cover an area of about 500 sq. km. consider these granites to be the result of granitization of arkose and pelitie rocks. Whereas treats them as intrusive into the Banjar Formation, recognized two components i.e. foliated and non-foliated which made the Bandal pluton the latter is intrusive into the former. This gave an isochron age of 1220±100 Ma for the foliated granite. This paper presents the results of a petrochemical and Rb-Sr isotopic studies of these granites with a view to understand their petrogenesis

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Zircon geochronology and Hf-O isotope geochemistry from granites in the Iapetus Suture Zone in Ireland and the Isle of Man  

Science.gov (United States)

Late Caledonian syn- to post-orogenic granites located in the Iapetus Suture Zone (ISZ) in Ireland and Britain have been related to A-type subduction and possible slab breakoff [1] following the Laurentia-Avalonian collision. Lack of reliable age data (especially in Ireland) has inhibited petrogenetic investigations of these rocks. Hence, ion microprobe U-Pb and oxygen isotope analyses as well as LA-MC-ICPMS Lu-Hf isotopic measurements on zircons from Irish and Isle of Man granites have been undertaken to provide better constraints on this enigmatic episode of the Caledonian Orogeny. Four stages of Late Caledonian granitic magmatism (c. 435, 417, 410 and 394 Ma) are indicated by U-Pb dating of oscillatory-zoned magmatic zircons. The Crossdoney, Kentstown, Drogheda and Ballynamuddagh granites together with a rhyolite from Glenamaddy have yielded U-Pb concordia ages, interpreted as intrusion-ages, between 419.9 ± 4.3 Ma (Glenamaddy) and 415.8 ± 2.0 Ma (Crossdoney) with a weighted average of 417.5 ± 0.9 Ma (MSWD = 1.3). The Glenamaddy Granite - which intruded the Glenamaddy Rhyolite - yielded an age of 410 ± 2.1 Ma. In addition, the Rockabill Granite yielded a younger age of 393.9 ± 1.9 Ma, whereas the Carnsore Granite yielded an older age of 434.6 ± 1.9 Ma. Inherited zircons (487 to 453 Ma) occur in several of the granites, and are interpreted to have been derived from Ordovician arc magmatic rocks accreted within the ISZ. A younger group of c. 440 Ma inherited zircons occurs in the c. 417 Ma Crossdoney and Ballynamuddagh granites. These grains could be related to continued or renewed Silurian arc magmatism. Hf-O isotopic measurements on the dated zircon grains range between -2 and +7 ?Hfi units and 5.5 to 8.5 o ?18O. These are interpreted to indicate the contribution of juvenile mantle melts - possibly derived from the Ordovician arc - to some of the granites. Significant heterogeneities in zircon oxygen isotopes in at least four of the granites further suggest the involvement of isotopically distinct protoliths. The Dhoon and Foxdale granites in the Isle of Man were previously regarded to be of Late Caledonian age. Surprisingly, zircons from these granites yielded concordant U-Pb ages of 455.6 ± 2.1 Ma (Dhoon) and 455.9 ± 2.1 Ma (Foxdale), respectively. Inherited cores are of Meso- and Palaeoproterozoic age. Hafnium isotopic analyses of the dated magmatic zircon rims from both intrusions are slightly more radiogenic than those from the Late Caledonian granites. Their ?18O values range between 5.5 to 7.5 o. The Isle of Man granites are now suggested to be the plutonic equivalents of a Late Ordovician (Caradocian) volcanic arc generated in the Iapetus Ocean. [1] Atherton & Ghani (2002), Lithos 62, 65-85.

Fritschle, Tobias; Daly, J. Stephen; Whitehouse, Martin J.; McConnell, Brian; Buhre, Stephan

2014-05-01

57

Petrographic and mineralogical features of the uraniferous pink granites in the north eastern desert of egypt  

International Nuclear Information System (INIS)

The present work is concerned with the petrological, mineralogical and geochemical studies of some uranium bearing younger granites in the north eastern desert of egypt particularly Gebel Gattar area. The area around Gebel Gattar comprises the following rock units (starting from the oldest): meta volcanic, diorite-grano-diorite complex- Dokhan volcanics- Hammamat sediments, younger granites and dykes. The most significant structural features are represented by NNE-ENE dominantly trending faults and joints. Petrographicaly, the pink granites are divided into normal and mineralized (uraniferous) granites. Normal granites are classified into three types; a) leucocratic perthitic granite, b) hornblende- biotite perthitic granite and c) two feldspars perthitic granite. Mineralized granites are sheared, deformed, pinkish brown in colour and strongly altered. A remarkable secondary uranium mineralization has been recorded along fault and fracture zones

58

Maurim intrusive suite: a calc-alkacic batholite zoned of catarinense shield  

International Nuclear Information System (INIS)

The geological survey of the Florianopolis Sheet (SG.22-Z-D-V) identified and characterized a calc-alkacic multi-intrusive and polydiapiric suite that occurs as a granitic batholite roughly concentric in texture and composition. This co-magmatic plutonic sequence is intrusive in the granite-gneissic basement of amphibolite facies, with which it was formerly confounded. The initial magmatic terms, put-in-place at the marginal portions of the batholite, are represented by quartz-diorites and tonalites (Forquilha Tonalites), followed by granodiorites (alto da Varginha Granodiorite), granodiorites to monzonites (Rio das Antas Granite) and completed by an inner portions of porphyritic monzonites (Sao Pedro de Alcantara Granite). The identifications of the compositional zoning that results from the development of the magmatic chamber is based on the examination of 74 rock samples that were analysed for major and minor oxides and trace elements (Ba, F, Li, Mo, Sn, W, Y, Rb, Nb, Zr and Sr). The treatment of these data shows the portions where mantle fractions predominate as well as the others where crustal meltings dominate, what demonstrates an origin by in situ differentiation processes, fractioning and different degrees of magmatic mixing. Geochronologic dating by Rb/Sr, K/Ar and U/Pb methods show isochronic and conventional ages of 600 to 700 m.y. that roughly are in accord with the temporal progress towards the younger felsic phases, putting this suite in the Upper Proterozoic age. The initial Sr sup(87) / Sr sup(86) ratios, around 0.710, point to a crustal origin with variable mantle contribution to these rocks. (author)

59

Feel Younger, Live Longer?  

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Full Text Available ... player. Feel Younger, Live Longer? HealthDay December 19, 2014 Related MedlinePlus Pages Healthy Aging Mental Health Seniors' ... up, researchers recorded deaths from all causes. The results? People whose self-perceived age was younger than ...

60

The uranium, thorium and molybdenum distribution in selected leucogranites of the Cape-granite-suite  

International Nuclear Information System (INIS)

Younger intrusions and hydrothermally altered rocks like alkali granite, alaskite, syenite and episyenite resembling uranium ore deposits in France and the Roessing ore body in SWA/Namibia are found within the Saldanha and Darling batholiths of the south-western Cape Province. Two areas were geologically mapped in detail and surveyed with a portable gamma spectrometer in order to establish the regional variation in U and Th concentration. A quantitative study of alpha particle tracks on autoradiographs of selected thin sections led to the determination of the contributions by various minerals to the U and Th content of each individual rock type. The rocks were also investigated petrologically and geochemically with special attention to secondary alteration processes that could have played a part in causing the distribution pattern of U and Th. Radioelement analyses of 45 mineral separates and 51 whole rock analyses were utilised

61

Magmatic constraints on localization of natural stone deposits in the Vehmaa rapakivi granite batholith, southwestern Finland  

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Full Text Available The 1580–1570 Ma old Vehmaa rapakivi granite batholith was studied with the aim to define the geological constraints for localization of natural stone deposits in the batholith. The batholith comprises four roughly concentric granite intrusions from the margin inwards: pyterlite, coarse-grained porphyritic rapakivi granite and two types of medium-grained porphyritic rapakivi granite. Also porphyry aplite and even-grained rapakivi granite occur. The batholith has intruded as a succession of pulses of subhorizontal sheet-like intrusions conceivably through repeated cauldron subsidence. Natural stone quarries are confined only to certain intrusions within the batholith. We show that the medium-grained porphyritic granite body in the centre of the batholith comprises two almost identical but different intrusions, with only slightly different appearances: the inner (IG and the outer (OG granite. The quarries are confined to the outer intrusion which has an appearance more attractive to the market than that of the inner intrusion. The localization of the natural stone deposits in the Vehmaa batholith is a result of the magmatic history of the batholith, producing intrusions of different appearances with different commercial potential.

Olavi Selonen

2011-08-01

62

Rb-Sr and Pb-Pb geochronological studies on the granite gneiss of Kuilapal, Purulia-Bankura Midnapore district, West Bengal  

International Nuclear Information System (INIS)

The number of younger granite plutons intruding the Singhbhum Mobile Belt (SMB) surrounding the Singhbhum-Orissa Craton, viz. Kuilapal granite on the East, Mayurbhanj granite, Soda granite, Arkasoni granite, Chakradharpur granite gneiss and Tamper kola granite on the west. Of these Kuilapal granite body is the largest. Besides small granite bodies intruding the low-grade meta sediments and meta volcanics which occur north of the Dalma volcanic belt. Petrographic and geochemical characters of the minor granite bodies south of Dalma volcanics are similar to those of Kuilapal granite, which is inferred to have been produced by shallow-level fractional crystallisation of a crustally derived granodiorite melt. Dominance of xenoliths in the Kuilapal granite suggest large-scale assimilation of crustal rocks. The radiometric ages vis-a-vis isotope geochemistry of the various granitoid plutons occurring within the mobile belt were used to constrain the evolutionary history of the SMB supracrustals. The Singhbhum Shear Zone which marks the boundary of the SMB with Singhbhum-Orissa Craton, shows multiple reactivation, the oldest being at ? 3.09Ga. Further phases of granite plutonism and/or shearing and mineralisation have been reported along this shear zone occurred in Palaeo-to Mesoproterozoic periods at ? 2.2, 1.8, 1.6-1.5, 1.4 and 1.0 Ga respectively. The present work pertains to the Rb-Sr and Pb-Pb whole rock geochronological studies on Kuilapal granite, which are intrus on Kuilapal granite, which are intrusive into the metasediments of Singhbhum group in the tectonic setup of north Singhbhum Mobile Belt. Fourteen samples were collected, finely powdered form the homgenised representative which were processed further. The dissolution of the rock carried out in a class-100 clean chemical laboratory, followed by the elemental separation using exchange chromatography. The separated pure fractions of the elements were analysed on VG354 Thermal Ionisation Mass spectrometer for their isotopic ratios. The Rb-Sr data on ten samples define an isochron age of 1792±98 Ma, with an initial 87Sr/86Sr of 0.7064±0.0069 (MSWD = 13). The Pb isotopic data on these samples define a Pb-Pb isochron age of 1863 ± 80Ma (MlSWD =11.3) with a model ?1 value of 8.53±0.27. Both the Rb-Sr and the Pb-Pb ages are in agreement within the limits of experimental errors. Since the 87Sr/86Sr initial ratio and model ?1 value are higher than the contemporary mantle sources, the data indicate involvement of enriched crustal sources. This age obtained on Kuilapal granite can be taken as the age of one of those periods of reactivation which occurred during Palaeo-to Mesoproterozoic periods. (author)

63

Tectono-magmatic evolution of the younger Gardar southern rift, South Greenland  

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Full Text Available The 1300–1140 Ma Gardar period in South Greenland involved continental rifting, sedimentation and alkaline magmatism. The latest magmatism was located along two parallel rift zones, Isortoq–Nunarsuit in the north and the Tuttutooq–Ilimmaasaq–Narsarsuaq zone in the south addressed here. The intrusive rocks crystallised at a depth of <4 km and are essentially undisturbed by later events. Magmatism in the southern zone began with the emplacement of two giant, ?800 m wide dykes and involved intrusion of transitional olivine basaltic, high Al/Ca magmas crystallising to troctolitic gabbros. These relatively reduced magmas evolved through marked iron enrichment to alkaline salic differentiates. In the Older giant dyke complex, undersaturated augite syenites grade into sodalite foyaite. The larger, c. 1163 Ma Younger giant dyke complex (YGDC mainly consists of structureless troctolite with localised developments of layered cumulates. A layered pluton (Klokkenis considered to be coeval and presumably comagmatic with the YGDC. At the unconformitybetween the Ketilidian basement and Gardar rift deposits, the YGDC expanded into a gabbroic lopolith. Its magma may represent a sample from a great, underplated mafic magma reservoir, parental to all the salic alkaline rocks in the southern rift. The bulk of these are silica undersaturated; oversaturated differentiates are probably products of combined fractional crystallisation and crustalassimilation.A major dyke swarm 1–15 km broad was intruded during declining crustal extension, with decreasing dyke widths and increasing differentiation over time. Intersection of the dyke swarm and E–W-trending sinistral faults controlled the emplacement of at least three central complexes (Narssaq, South Qôroq and early Igdlerfigssalik. Three post-extensional complexes (Tugtutôq,Ilímaussaq and late Igdlerfigssalik along the former rift mark the end of magmatism at c. 1140 Ma. The latter two complexes have oblate plans reflecting ductile, fault-related strain. The Tugtutôqcomplex comprises quartz syenites and alkali granites. The Ilímaussaq complex mainly consists of nepheline syenite crystallised from highly reduced, Fe-rich phonolitic peralkaline (agpaitic magma,and resulted in rocks with very high incompatible element concentrations.Abundant anorthositic xenoliths in the mafic and intermediate intrusions point to a large anorthosite protolith at depth which is considered of critical importance in the petrogenesis of the salicrocks. Small intrusions of aillikite and carbonatite may represent remobilised mantle metasomites. The petrological similarity between Older and Younger Gardar suites implies strong lithospheric control of their petrogenesis. The parental magmas are inferred to have been derived from restitic Ketilidian lithospheric mantle, metasomatised by melts from subducting Ketilidian oceanic crust and by small-scale melt fractions associated with Gardar rifting.There are numerous analogies between the southern Gardar rift and the Palaeogene East Africanrift.

Brian G.J. Upton

2013-11-01

64

Uranium in granites  

International Nuclear Information System (INIS)

Recent research activities of the Canadian Uranium in Granites Study are presented in 18 papers and 3 abstracts. 'Granites' is used as a generic term for granitoids, granitic rocks, and plutonic rocks

65

Feel Younger, Live Longer?  

Medline Plus

Full Text Available ... than 8 years of follow-up, researchers recorded deaths from all causes. The results? People whose self- ... younger than their real age had a lower death rate from all causes compared to those who ...

66

Feel Younger, Live Longer?  

Science.gov (United States)

... Health Transcript Feeling younger may actually help you live longer, according to a new study. Nearly 6,500 people -- 52 years and older -- were asked how old they felt. About 70 percent of the adults ...

67

Feel Younger, Live Longer?  

Medline Plus

Full Text Available ... Health Transcript Feeling younger may actually help you live longer, according to a new study. Nearly 6,500 people -- 52 years and older -- were asked how old they felt. About 70 percent of the adults ...

68

Pórfiro granítico Mojotoro (Salta: ¿Una cúpula intrusiva o un dique en el ciclo pampeano? The Mojotoro granitic porphyry (Salta: An intrusive roaf or a dike in the Pampean Cycle?  

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Full Text Available El pórfiro granítico Mojotoro, constituye la cúpula de un plutón epizonal, emplazado en un área geológica bien conocida, de la Formación Puncoviscana, en las inmediaciones de la ciudad de Salta (24º47´44,9"S - 65º21´35,9"W, 1.304 m s.n.m.. Sin bien se carece de determinaciones geocronológicas, los caracteres geológicos regionales y situación estratigráfica de no alcanzar los niveles del Grupo Mesón, sugieren edades pampeanas, correspondientes a la orogenia tilcárica. Los caracteres petrográficos corresponden a pórfiros graníticos, con fenocristales de feldespato potásico, acompañados por cuarzo, plagioclasa y biotita. Las rocas han sufrido intensa sericitización, caolinización y limonitización. Asimismo muestra esferulitas recristalizadas, inclusiones fluidas y fragmentos de granófiro, que indican emplazamiento somero, con rápido intercrecimiento conjunto de cuarzo en una masa de feldespato alcalino hipersolvus. La susceptibilidad magnética es baja con valores de 0,11 x 10-3 SI, típicos para granitos corticales formados a partir de protolitos metasedimentarios.The Mojotoro porphyritic granite is located close to the city of Salta (24°47´44,9"S - 65°21´35,9"W, 1304 m.a.s.l., at Cerro Mojotoro in the Eastern Cordillera. The pluton is emplaced in the Puncoviscana Formation (Late Precambrian-Early Cambrian, a lithological unit composed mainly of greenish pelites. The Puncoviscana Formation is covered unconformably by Cambrian quartzites of the Meson Group. Stratigraphic relationships of the granite indicate a Pampean age and emplacement during the Tilcaric orogenic phase. Petrographically it is a porphyritic granite with K-feldspar phenocrysts accompanied by quartz, plagioclase and biotite. The rock is strongly altered by sericitization, kaolinization, and limonitization. Likewise, the granite exhibits recrystalized spherules, fluid inclusions and granophyric fragments, indicative of shallow emplacement, with fast intergrowth of quartz in a mass of K-feldspar hypersolvus. Low magnetic susceptibility, with values of 0.11x10-3 SI, is typical of cortical granite that was formed from a metasedimentary protolith.

A.J. Toselli

2005-06-01

69

Special features of the accessory mineralization of the ore-bearing light-granite formation of the Southern Pamir  

International Nuclear Information System (INIS)

In the article was examined the distribution of the accessory minerals in six intrusive complexes, which relate to one light-granite formation type. According to the elementary sign, all accessory minerals of the light-granite formation of the Southern Pamir are classified to nine groups. It is compared the accessory minerals of the Southern Pamir with the accessory minerals of the light-granites of other regions. The connection between the accessory minerals of intrusive complexes and the mineralization are shown

70

Petrogenesis of magmatic albite granites associated to cogenetic A-type granites: Na-rich residual melt extraction from a partially crystallized A-type granite mush  

Science.gov (United States)

The uncommon association of cogenetic and nearly contemporaneous potassic K-feldspar A-type granites and sodic albite granites is observed within the 347 Ma-old bimodal Saint-Jean-du-Doigt (SJDD) intrusion, Brittany, France. A-type granites outcrop as small bodies (magma. On the other hand, small volumes of hybrid, enclave-bearing granodiorite within the SJDD lopolith suggest mixing processes within a reservoir located at deeper crustal levels. A-type granites may therefore form by magma mixing between the mafic magma and crustal melts. Alternatively, they might derive from the pure melting of an immature biotite-bearing quartz-feldspathic crustal protolith induced by early mafic injections at low crustal levels. Strong field evidences coupled to mineral chemistry and elemental geochemistry strongly support a magmatic origin for the albite granite. Sr, Nd, Hf zircon isotope data, U-Pb zircon ages, as well as data on petrography, mineral chemistry and elemental geochemistry attest that A-type and albite granites are closely related. Our preferred petrogenetic model is to consider the albite granite magma as a compositionally extreme melt that was extracted from a partially crystallized A-type granite mush at a late stage of crystallization. Alternatively, albite granites could form by melting of plagioclase-rich layers formed during A-type granite differentiation.

Barboni, Mélanie; Bussy, François

2013-09-01

71

Ras ed Dom migrating ring complex: A-type granites and syenites from the Bayuda Desert, Sudan  

Science.gov (United States)

A major cluster of anorogenic A-type, subvolcanic ring complexes of Silurian to Jurassic age is emplaced into Proterozoic rocks of the basement complex in the Bayuda Desert of northern Sudan. The complexes belong to the Younger granite association which is widespread throughout the Sudan and environs. The Ras ed Dom complex is a striking example of migrating centres in which intrusive activity shifted eastwards and declined in strength with time. Intrusive rocks predominate and consist of metaluminous and peralkaline syenites and granites. Field relations indicate that the sequence metaluminous syenite-peralkaline syenite-peralkaline granite is a recurrent fractionation series representing high level fractionation of a parental metaluminous syeno-monzonitic magma. The metaluminous syenites contain rare early-formed plagioclase (oligoclase-andesine) but otherwise the suite is typically hypersolvus. The metaluminous rocks are characterised by an early pyroxene zone from ferrohedenbergite to aegirine-augite and enclosed in ferroedenitic amphibole. Microprobe analysis reveals a broad range of amphibole compositions in the peralkaline rocks, comprising ferrorichterite-arfvedsonite-riebeckite solid solutions. Late aegirine, exhibiting marked enrichment in the acmite component, typically replaces the arfvedsonite, especially in the granites. Extremely pure albite accompanies aegirine and the development of these phases is attributed to limited interaction between the rocks and late sodic fluids. Geochemical variation in the suite includes marked depletions of CaO, Ba and Sr with increasing silica, consistent with fractionational removal of alkali-feldspar. The peralkalinity of the later rocks has been enhanced by sodic autometasomatism, reflected in their high contents of REE and HFS elements such as Zr, Nb and Ga, and by the erratic distribution of these elements. LREE-enrichment in the suite is marked and suggests equilibrium with a residual HREE-rich phase such as garnet in the source rocks. The Younger Granite magmas are attributed to melting of a lower crustal mafic-rich source such as garnet-eclogite. The heat for this anatectic event is thought to have come from mantle-derived basalt magma, the uprise of which was largely checked in the lower crust, only minor amounts reaching the surface.

O'Halloran, D. A.

72

The age of the Baerhalde Granite (Black Forest) and the uranium deposit of Menzenschwand  

International Nuclear Information System (INIS)

Rb/Sr total-rock dating of intrusive rocks in the Southern Black Forest yielded ages of 290 +- 6 my (my = millions of years) for the Baerhalde Granite, 315 +- 10 my for the Schluchsee Granite and 274 +- 7 my for the porphyry cutting both granites. Biotite and muscovite Rb/Sr and K/Ar-dates however yielded ages of 325 +- 3 my. Further total rock analyses of the Baerhalde Granite presented in this paper reconfirmed the total rock age previously published and they did not eliminate the discrepancy between the younger total-rock- and the older mineral-ages. Pb/U-dates of two pitchblende-samples from the Krunkelbachtal near the village of Menzenschwand yielded ages of 230 my which were already published previously. Re-analyses of these samples reconfirmed these U/Pb-dates which also agreed with additional 210Pb-dates. However two additional samples of pitchblende yielded higher Pb/U-ages which also are highly discordant in respect to U/Pb and 210Pb-ages indicating a disturbance of the radioactive equilibrium caused by geochemical processes in most recent times. The 207Pb/206Pb-ages of all samples are considerably higher at about 300 my. Although the value of these dates is restricted because of the wide limits of error of this method at young ages, too young Pb/U-ages due to lead loss may be possible. A real age of the U-mineralisation of about 300 my therefore can not be excluded. (orig.))

73

Review of engineering, hydrogeological and vadose zone hydrological aspects of the Lanseria Gneiss, Goudplaats-Hout River Gneiss and Nelspruit Suite Granite (South Africa)  

Science.gov (United States)

Three major basement granites of South Africa, viz. the Lanseria Gneiss of the Johannesburg Dome Granite, the Goudplaats-Hout River Gneiss and the Nelspruit Suite, are compared in terms of existing and new geotechnical and hydrogeological data. Typical weathering profiles based on landform and climate are deduced, denoting typical engineering and hydrogeological behaviour. Finally, the vadose zone behaviour of the basement granites are described with the aim on better understanding of the behaviour of these systems under variable saturation. Ephemeral hillslope wetlands, seepage lines and catenas are specifically addressed as associated hydrological influences, as well as the associated processes of translocation forming duplex soils and pedogenesis forming ferricrete. The final summarised findings depict low plasticity and expansiveness of granites with the most notable geotechnical influences being collapsibility, dispersive behaviour, seepage and difficult excavation. Hydrologically, secondary porosity prevails and younger structures or intrusions govern groundwater occurrence. The vadose zone comprises thick fractured rock to be included in modelling with the soil zone having saturated conductivity typically in the order of 1 × 10-4 to 1 × 10-5 m/d.

Dippenaar, Matthys A.; van Rooy, J. Louis

2014-03-01

74

2005 dossier: granite; Dossier 2005: granite  

Energy Technology Data Exchange (ETDEWEB)

This document makes a status of the researches carried out by the French national agency of radioactive wastes (ANDRA) about the geologic disposal of high-level and long-lived radioactive wastes in granite formations. Content: 1 - advantage of granitic formations for the geologic disposal; 2 - containers; 3 - design study of a disposal facility in granitic environment; 4 - understanding and modelling of granite; 5 - description of disposal concepts in granitic environment; 6 - long-term and safety aspects; 7 - conclusion. (J.S.)

NONE

2005-07-01

75

Geochronology of granitic rocks from the Ruangwa region, southern Tanzania - Links with NE Mozambique and beyond  

Science.gov (United States)

New U-Pb zircon LA-ICP-MS data are presented for 4 granitoid bodies which intrude high grade gneisses of the previously unmapped Ruangwa region in southern Tanzania. The study area forms part of the late Neoproterozoic East African Orogen (EAO). The oldest unit, a coarse-grained migmatitic granitic orthogneiss gave an early Neoproterozoic (Tonian) crystallization age of 899 ± 9/16 Ma, which is similar to, but significantly younger than, Stenian-Tonian basement ages in areas relatively nearby. Crust of this age may extend as far north as the major Phanerozoic Selous Basin, north of which Archaean protolith ages predominate (the "Western Granulites"), except for the juvenile Neoproterozoic "Eastern Granulites", which are not represented in the study area. To the south, the Tonian crust of the study area provides a tentative link with the Marrupa Complex in NE Mozambique. A granite pluton, dated at 650 ± 5/11 Ma is broadly coeval with the main Pan-African tectono-thermal event in the East African Orogen that is recorded across Tanzania north of the Selous Basin. Zircons in this granite contain inherited cores at ca. 770 Ma. This age is within the range of dates obtained from south and west of the study area from juvenile granitoid orthogneisses which might be related to a widespread, but poorly understood, early phase of Gondwana assembly along an Andean-type margin. South of the study area, in NE Mozambique, the latest orogenic events occurred at ca. 550 Ma, and are sometimes attributed to the Ediacaran-aged "Kuunga Orogeny". While metamorphic dates of this age have been recorded from the EAO north of the Selous Basin, magmatic rocks of this event have not been recognized in Tanzania. The two youngest granitoids of the present study are thus the first 500-600 Ma igneous rocks reported from the region. A weakly deformed very coarse-grained granite pluton was dated at 591 ± 4/10 Ma, while a very late, cross-cutting, undeformed granite dyke gave an intrusive age of 549 ± 4/9 Ma. The granitoids ages presented in this study contain elements that are characteristic of the northern, Tanzania-Kenya, segment of the East African Orogen and of the southern, Mozambique, segment. The Tonian orthogneiss sample is typical of (but somewhat younger than) the Marrupa Complex of NE Mozambique. No zircon inheritance was recorded in the sample, typical of the juvenile Marrupa Complex. On the other hand, the ca. 650 Ma granite pluton has an age that is typical of the northern segment of the orogen; this is the first recorded granite of that age intruded into the Tonian-dominated crust of southern Tanzania or NE Mozambique. The two younger granites have provided dates that are typical of the southern segment of the orogen, and that of the Kuunga Orogen. The study area thus appears to represent an area of transitional crust straddling two complex and contrasting segments of the East African Orogen, with elements of both segments present and evidence for a ca. 770 Ma event which appears to be quite widespread and may relate to the early phases of Gondwana amalgamation in southern East Africa.

Thomas, Robert J.; Bushi, Alphonce M.; Roberts, Nick M. W.; Jacobs, Joachim

2014-12-01

76

Pórfiro granítico Mojotoro (Salta): ¿Una cúpula intrusiva o un dique en el ciclo pampeano? / The Mojotoro granitic porphyry (Salta): An intrusive roaf or a dike in the Pampean Cycle?  

Scientific Electronic Library Online (English)

Full Text Available SciELO Argentina | Language: Spanish Abstract in spanish El pórfiro granítico Mojotoro, constituye la cúpula de un plutón epizonal, emplazado en un área geológica bien conocida, de la Formación Puncoviscana, en las inmediaciones de la ciudad de Salta (24º47´44,9"S - 65º21´35,9"W, 1.304 m s.n.m.). Sin bien se carece de determinaciones geocronológicas, los [...] caracteres geológicos regionales y situación estratigráfica de no alcanzar los niveles del Grupo Mesón, sugieren edades pampeanas, correspondientes a la orogenia tilcárica. Los caracteres petrográficos corresponden a pórfiros graníticos, con fenocristales de feldespato potásico, acompañados por cuarzo, plagioclasa y biotita. Las rocas han sufrido intensa sericitización, caolinización y limonitización. Asimismo muestra esferulitas recristalizadas, inclusiones fluidas y fragmentos de granófiro, que indican emplazamiento somero, con rápido intercrecimiento conjunto de cuarzo en una masa de feldespato alcalino hipersolvus. La susceptibilidad magnética es baja con valores de 0,11 x 10-3 SI, típicos para granitos corticales formados a partir de protolitos metasedimentarios. Abstract in english The Mojotoro porphyritic granite is located close to the city of Salta (24°47´44,9"S - 65°21´35,9"W, 1304 m.a.s.l.), at Cerro Mojotoro in the Eastern Cordillera. The pluton is emplaced in the Puncoviscana Formation (Late Precambrian-Early Cambrian), a lithological unit composed mainly of greenish pe [...] lites. The Puncoviscana Formation is covered unconformably by Cambrian quartzites of the Meson Group. Stratigraphic relationships of the granite indicate a Pampean age and emplacement during the Tilcaric orogenic phase. Petrographically it is a porphyritic granite with K-feldspar phenocrysts accompanied by quartz, plagioclase and biotite. The rock is strongly altered by sericitization, kaolinization, and limonitization. Likewise, the granite exhibits recrystalized spherules, fluid inclusions and granophyric fragments, indicative of shallow emplacement, with fast intergrowth of quartz in a mass of K-feldspar hypersolvus. Low magnetic susceptibility, with values of 0.11x10-3 SI, is typical of cortical granite that was formed from a metasedimentary protolith.

A.J., Toselli; R.N., Alonso.

2005-06-01

77

Melting granites to make granites  

Science.gov (United States)

Large-scale partial melting in the continental crust is widely attributed to fluid-absent incongruent breakdown of hydrous minerals in the case of pelites, greywackes and meta-mafic rocks. Granite is a far more common rock in the continental crust, but fluid-absent hydrate-breakdown melting is unlikely to result in significant melting in granites because of their low modal abundance of mica or amphibole. Experiments show that fluid-present melting can produce ~30% melt at low temperatures (690°C). Thus, granites and leucogranites can be very fertile if H2O-present melting occurs via reactions such as plagioclase + quartz + K-feldspar + H2O = melt, because of their high modal proportions of the reactant phases. Our study investigates the Kinawa Migmatite in the São Francisco Craton, southeastern Brazil. This migmatite is derived from an Archaean TTG sequence and can be divided into; 1) pink diatexites, 2) leucosomes, 3) grey gneisses and 4) amphibolites. The migmatite records upper-amphibolite to beginning of granulite facies metamorphism in a P-T range from 5.1-6.6 kbar and ~650-780°C. Pink diatexites are the most abundant rocks, and their appearance varies depending on the amount of melt they contained. Three types are recognised: residual diatexites (low melt fraction (Mf)), schlieren diatexites (moderate Mf) and homogeneous diatexites (high Mf). They are very closely related spatially in the field, with mostly transitional contacts. There is a sequence with progressive loss of ferromagnesian minerals, schollen and schlieren through the sequence to the most melt-rich parts of the diatexites as magmatic flow became more intense. There are fewer ferromagnesian minerals, thus the melt becomes cleaner (more leucocratic) and, because the schlieren have disaggregated the aspect is more homogeneous. These parts are texturally similar to leucogranites in which the biotite is randomly distributed and pre-melting structures are completely destroyed. The likely protolith for the migmatites was a leucocratic granodiorite (with modal K-feldspar up to 30% and biotite up to 5%), and from geochemical modelling the degree of partial melting ranged from 0.21 to 0.25. Furthermore, the residual diatexites show a complementary low modal proportion, or even absence, of K-feldspar, but an increase in modal plagioclase, quartz (up to 56 and 37% respectively) and biotite (5-16%). This suggests that the melting reaction did not involve biotite and that plagioclase and quartz were in excess. As result the melt generated is fairly leucocratic, and most of the mafic phases in it are inherited. Anatectic melts in the Kinawa Migmatite were mildly metaluminous and distinctly leucocratic (A/CNK from 0.97 to 1.01; SiO2 from 72.8 to 75.65%; (FeOT+MgO+TiO2) from 0.49 to 2.3%). Since most granites have a higher (FeOT+MgO+TiO2), additional processes must add the "mafic component" to these melts before they form plutons.

Carvalho, Bruna B.; Sawyer, Edward W.; Janasi, Valdecir de A.

2014-05-01

78

The Younger Dryas Event  

Science.gov (United States)

This topic in depth deals with the Younger Dryas event, a short period of extremely cold temperatures interrupting the current interglacial period. It is currently debated whether the Younger Dryas event occurred solely in parts of the North hemisphere or throughout the world.The first website, (1), created by World History, provides a short, concise summary of the Younger Dryas period. Users can find a brief statement about the prevailing theory of the cause of this event. Lund University offers an amazing image of a stratigraphic record illustrating the Late Glacial sequence at the second website (2). Users can view the impressive Younger Dryas sedimentation layer and also see an image of the flower, _Dryas octopetala_, which the event is named after. Next, the Department of Natural Resources for the Province of Nova Scotia supplies images of the geologic landscape of Nova Scotia (3). Students can find descriptions of the Younger Dryas event and other glacial features. The forth website (4 ), produced by Klaus Keller as part of his lecture materials for classes at Penn State, is an online document illustrating the abrupt changes experienced on earth during the Younger Dryas. This website discusses the theorized relationship between the North Atlantic thermohaline circulation (THC) and the event. Next, the University of Arizona discusses its research on the environmental changes in mid-North America over the last several millennia (5). Users can learn how the researchers are attempting to create the first high-resolution chronology of the transition from the Late Glacial to the Early Holocene. In the sixth website (6 ), the University of Chicago offers an online article addressing the unknowns in our current understanding of climate change. Users can learn how the abrupt climate changes in the past such as the Younger Dryas are still difficult to model. Next, David J. Graham from the University of Wales addresses the importance of examining the moraine morphology and sedimentology in order to gather more knowledge about the climatic and glacio-dynamic conditions that occurred during the Younger Dryas period (7 ). This online poster provides images, figures, and descriptions of the interpretations of the landform-sediment associations present in the upper Ennerdale. Konrad Hughen from the Woods Hole Oceanographic Institution summarizes his group's research which illustrates the effects the northern tropical regions of the Southern Hemisphere experienced during the Younger Dryas event (8). In this downloadable document, users can learn about his group's creation of high-resolution records of tropical vegetation change that demonstrate the synchronization between the climate changes in the high latitude North Atlantic region and in the tropical South America during the event. Lastly, the U.S. Global Change Research Program discusses the classification of an abrupt climate change, the rapidity of past climate change according to the paleoclimatic records, the causes of climate change, and its consequences (9). Visitors can learn about the swiftness of the Younger Dryas event and how another occurrence like this may affect our society and the natural world.

79

Rb-Sr, K-Ar and fission track ages for granites from Penang Island, West Malaysia: an interpretation model for Rb-Sr whole-rock and for actual and experimental mica data  

Science.gov (United States)

Penang Island represents the northwestern extension of the western magmatic belt of Peninsular Malaysia. Thirty-one samples of highly evolved biotite-and biotite-muscovite granites were used in an integrated study to unravel the complex magmatic, tectonic and cooling histories of these rocks. Highly distorted Rb-Sr whole-rock age patterns are evident. These are attributed to the partial post-magmatic Sr homogenization within the granite batholith which led to the rotation of isochrons towards younger ages and higher (87/86)Sr intercepts. The recognition of this mechanism allowed the establishment of a new Rb-Sr interpretation model. The intrusion ages of the granites can be extrapolated based on the evolutionary trend of the initial (87/86)Sr. Including the data of Bignell and Snelling, three episodes of granite emplacement at 307±8 Ma, 251±7 Ma and 211±2 Ma are suggested for Penang and the NW Main Range. The late-Triassic intrusive induced a hydrothermal conductive convection system which affected all the granites. It is considered to be responsible for the Rb-Sr whole-rock age distortion, the Rb-Sr and K-Ar biotite age resetting and the textural and mineralogical changes in the granites. The duration of the hydrothermal convections, deduced from the Rb-Sr whole rock ages, is about 6 Ma and 20 Ma in the northern and southern parts of Penang respectively. Fast regional cooling to 350±50°C within a time span of 1 3 Ma is recognized for the late-Triassic Feringgi intrusive from the mica ages, followed by a generally slow cooling rate of about 1°C/Ma. Fission track ages, in addition, indicate blockwise uplift along the N-S and NW-SE tending faults, thus resulting in the exposure of deeper crustal levels in southern and eastern Penang. A change in the tensional regime since Oligocene/Miocene, accompanied by a southwest tilting of the island, is indicated by the fission track apatite ages. Variable sometimes younger K-Ar, respectively Rb-Sr biotite ages mainly depend on the degree of hydrothermal overprint at different crustal levels. An increase of the reaction surface by grain size reduction influences Rb-Sr and K-Ar mica ages in similar ways, as has been demonstrated by experimental data.

Kwan, T. S.; Krähenbühl, R.; Jager, E.

1992-09-01

80

Petrography and geochemistry of the topaz-bearing granite stocks in Artjärvi and Sääskjärvi, western margin of the Wiborg rapakivi granite batholith  

Directory of Open Access Journals (Sweden)

Full Text Available The Artjärvi and Sääskjärvi granite stocks at the western margin of the Wiborg rapakivi batholith are multiphase rapakivi granite intrusions in which the most evolved phase is topaz-bearing granite. The Artjärvi stock is composed of porphyritic and even-grained biotite granite and even-grained topaz granite, and the Sääskjärvi stock comprises even-grained biotite granite and porphyritic topazgranite. The granites are metaluminous to peraluminous A-type granites, showing within-plate (WPG geochemical characteristics. The topaz granites from the Artjärvi and Sääskjärvi stocks are petrographically and geochemically similar to other topaz-bearing rapakivi granites in Finland. The anomalous geochemistry of the topaz granite is essentially magmatic; postmagmatic reactions have only slightly modified its composition. Greisen veins, some of which are mineralized, are widely found associated with the Artjärvi and Sääskjärvi stocks.The most characteristic feature of the Artjärvi granite stock is a stockscheider at the roof contact of the topaz granite. The stockscheider is composed of schlieren layering and pegmatite layers parallel to the contact. The most probable mechanism for the formation of the schlieren layering is velocity-gradient sorting parallel to the flow, which led to accumulation of mafic minerals along the upper contact of the topaz granite. Cooling and contraction of the topaz granite formed fractures parallel to the roof contact and the residual pegmatite magmas were injected along the fractures forming pegmatite layers. Textures like graphic intergrowths, aplitic groundmass and fan-shaped alkali feldspar crystals associated with the Artjärvi porphyritic biotite granite and pegmatite indicatecrystallization from undercooled magma. Miarolitic cavities found in the porphyritic biotite granite and topaz granite indicate at least local volatile saturation.

Sari Lukkari

2002-01-01

81

U-Pb zircon ages of members of the Salem Granatic Suite along the northern edge of the Central Damaran Granite Belt  

International Nuclear Information System (INIS)

Porphyric Salem Suite granite rocks in the low-grade Northern Zone and adjoining portion of the high-grade Central Zone give respective ages of 589+- 40 and 546+- 30 m.y. (2 omnicron) which are indistinguishable within the limit of uncertainty. A complex, diachronous tectonic history is evident. Ages of deformation and granite intrusion in the Northern Zone and the coastal region of the Huab and Ugab Rivers appear to be similar. Deposition of the Mulden Group, the single intense phase of deformation and the low-grade metamorphism of the Northern Zone were completed between 550 and 600 m.y. ago and prior to the first granite intrusions. This was between 54 and 140 m.y. before completion of deformation in the adjoining, fundamentally different, high-grade, tectonically complex, granite-rich Central Zone. D1 in the southern Central Zone is older than 595 m.y. D2 may have been coeval in both the Northern and Central Zones, but a northward decrease in age across the Central Zone cannot be ruled out. D3 decreases in age northwards across the Central Zone and is at least 20 m.y. and may be as much as 120 m.y. younger in the north. The peak of metamorphism could have been coeval in the Northern and Central Zones. D3 in the northern Central Zone (479+- 16 m.y.) is the youngest major deformation event in the orogen. The Central Zone was finally thrust against and over the Northern Zone subsequent to D3 in the formerent to D3 in the former

82

The Layos Granite, Hercynian Complex of Toledo (Spain): an example of parautochthonous restite-rich granite in a granulitic area  

OpenAIRE

The Layos Granite forms elongated massifs within the Toledo Complex of central Spain. It is late-tectonic with respect to the F2 regional phase and simultaneous with the metamorphic peak of the region, which reached a maximum temperature of 800-850°C and pressures of 400-600 MPa. Field studies indicate that this intrusion belongs to the "regional migmatite terrane granite" type. This granite is typically interJayered with sill-like veins and elongated bodies of cordierite/ gar...

Barbero Gonza?lez, Luis C.; Villaseca Gonza?lez, Carlos

1992-01-01

83

Mineral chemistry, petrology and geochemistry of the Sebago granite-pegmatite system, southern Maine, USA  

OpenAIRE

The Permian (293 ± 2 Ma) Sebago Pluton is a homogeneous, two-mica granite situated in the Oxford pegmatite field, southwestern Maine. Surrounding the pluton is an area designated as the Sebago Migmatite Domain (SMD) dominated by metapelitic migmatites and diatexites with subordinate intrusions of heterogeneous, two-mica and biotite granites, pegmatitic leucogranites and granitic pegmatites. The Sebago Pluton plus the SMD formerly defined the extent of the Sebago Batholith. Mo...

Wise M; Brown C D

2010-01-01

84

Characterization of the granite dyke swarm within the Ronda peridotites (Betic Cordilleras)  

OpenAIRE

This work analyses, from the structural point of view, the granite dyke swarm in the R onda area. Structural features of granite dykes from outcrop to microscopic scale show that their intrusion is controlled by the emplacement of the peridotites over the underlying crustal rocks and prove that granite dyke swarm is not placed randomly. Actually, the orientation of deformed and undeformed dykes provides an indirect but useful tool to determine the kinematic criteria of the hot emp...

Esteban, Jose? Julia?n; Cuevas, Julia

2006-01-01

85

A-type granite and the Red Sea opening  

Science.gov (United States)

Miocene-Oligocene A-type granite intrudes the eastern side of the Red Sea margin within the zone of extension from Jiddah, Saudi Arabia south to Yemen. The intrusions developed in the early stages of continental extension as Arabia began to move slowly away from Africa (around 30-20 Ma). Within the narrow zone of extension silicic magmas formed dikes, sills, small plutons and extrusive equivalents. In the Jabal Tirf area of Saudi Arabia these rocks occur in an elongate zone consisting of late Precambrian basement to the east, which is gradually invaded by mafic dikes. The number of dikes increases westward until an igneous complex is produced parallel to the present Red Sea axis. The Jabal Tirf igneous complex consists of diabase and rhyolite-granophyre sills (20-24 Ma). Although these are intrusine intrusive rocks their textures indicate shallow depths of intrusion (granite invaded thick (1500 m) volcanic series, at various levels and times. Erosion within the uplifted margin of Yemen suggests that the maximum depth of intrusion was less than 1-2 km. Granophyric intrusions (20-30 Ma) within mafic dike swarms similar to the Jabal Tirf complex are present along the western edge of the Yemen volcanic plateau, marking a north-south zone of continental extension. The alkali granites of Yemen consist primarily of perthitic feldspar and quartz with some minor alkali amphiboles and acmite. These granites represent water-poor, hypersolvus magmas generated from parent alkali basalt magmas. The granophyric, two-feldspar granites associated with the mafic dike swarms and layered gabbros formed by fractional crystallization from tholeiitic basalt parent developed in the early stages of extension. Initial 87Sr/86Sr ratios of these rocks and their bulk chemistry indicate that production of peralkaline and metaluminous granitic magmas involved both fractio??nation and partial melting as they ascended through the late Precambrian crust of the Arabian plate. ?? 1992.

Coleman, R.G.; DeBari, S.; Peterman, Z.

1992-01-01

86

EXPLOITATION OF GRANITE BOULDER  

OpenAIRE

The processes of forming, petrography, features, properties and exploitation of granite boulders are described. The directional drilling and black powder blasting is the succesful method in exploitation of granite boulders (boulder technology).

Ivan Cotman

1994-01-01

87

EXPLOITATION OF GRANITE BOULDER  

Directory of Open Access Journals (Sweden)

Full Text Available The processes of forming, petrography, features, properties and exploitation of granite boulders are described. The directional drilling and black powder blasting is the succesful method in exploitation of granite boulders (boulder technology.

Ivan Cotman

1994-12-01

88

Geochemistry and Geochronology U-Pb SHRIMP of granites from Peixoto de Azevedo: Alta Floresta Gold Province  

International Nuclear Information System (INIS)

The analysis of petrographic, geochemical and geochronological data of granites in the Peixoto de Azevedo region, Mato Grosso, Brazil, in the eastern portion of the Alta Floresta Gold Province, led to the recognition of two granitic bodies bounded by regional major faults and shear zones. In the northwestern portion a body with featured as biotite granodiorite, coarse-grained, with porphyritic to inequigranular texture, metaluminous to peraluminous, high-K calc-alkaline and magnesium character. In the southeastern portion of the area, a biotite monzogranite coarse-grained, with equigranular to porphyritic texture, slightly peraluminous, high-K calc-alkaline and dominantly of ferrous character. U- Pb dating (SHRIMP) showed that the biotite monzogranite has an age of 1869 ± 10 Ma, similar to the Matupa Intrusive Suite, while the biotite granodiorite has an age of 1781 ± 10 Ma, that is the age expected to Peixoto Granite. Both units show patterns of rare earth elements with enrichment of light over heavy and negative Eu anomaly (LaN/YbN » 7.6 to 17.31 and ratios Eu/EU? between 0.46 – 0.72 for biotite monzogranite and LaN/YbN » 7.13 to 29.09 with ratios Eu/Eu? between 0.25 - 0.40 for the biotite granodiorite). Trace elements pattern for both present negative anomalies of Ba, P, Ti and Nb indicating an evolution from mineral fractionation and subduction related sources. In this paper, it is suggested that the monzogranite Matupa was developed in mature arc tectonic environment. For the Peixoto Granite, two hypotheses are suggested: (a) it was developed in younger magmatic arc environment associated with the Colider Magmatism or (b) it was generated in extensional tectonic environment during the Columbia Super continent break up. (author)

89

2005 dossier: granite  

International Nuclear Information System (INIS)

This document makes a status of the researches carried out by the French national agency of radioactive wastes (ANDRA) about the geologic disposal of high-level and long-lived radioactive wastes in granite formations. Content: 1 - advantage of granitic formations for the geologic disposal; 2 - containers; 3 - design study of a disposal facility in granitic environment; 4 - understanding and modelling of granite; 5 - description of disposal concepts in granitic environment; 6 - long-term and safety aspects; 7 - conclusion. (J.S.)

90

Thorite in an Apollo 12 granite fragment and age determination using the electron microprobe  

Science.gov (United States)

We present the first quantitative compositional analysis of thorite in a lunar sample. The sample, a granitic assemblage, also contains monazite and yttrobetafite grains, all with concentrations of U, Th, and Pb sufficiently high to determine reliably with the electron microprobe. The assemblage represents the first documented occurrence of these three minerals together and only the second reported occurrence of thorite in a lunar rock. Sample 12023,147-10 is a small, monomict rock fragment recovered from an Apollo 12 regolith sample. It comprises graphic intergrowths of K-feldspar and quartz, and plagioclase and quartz, along with minor or accessory hedenbergite, fayalite, ilmenite, zircon, yttrobetafite, thorite, monazite, and Fe metal. Thorite, ideally ThSiO4, occurs in the assemblage adjacent to quartz and plagioclase, and includes a 12% xenotime ([Y,HREE]PO4) component. From quantitative electron-probe microanalysis (EPMA) of Th, U, and Pb in thorite, assuming that all of the measured Pb is radiogenic, we calculate an age of 3.87 ± 0.03 Ga. Yttrobetafite and monazite, which contain lesser concentrations of U, Th, and Pb than the thorite, yield ages of 3.78 ± 0.06 Ga and 3.9 ± 0.3 Ga, respectively. These dates are consistent with formation of the granitic material around 3.8-3.9 Ga, possibly associated with, or after, the formation of the Imbrium basin. This age falls within a group of younger ages for granitic samples, measured mainly by ion microprobe analysis of zircon, compared to a suite of older ages, ca. 4.20-4.32 Ga, also from zircons (Meyer et al., 1996). A 3.8-3.9 Ga age may reflect an origin following the Imbrium event whereby granitic melt formed as a result of heating and melting, and was mobilized and emplaced along an Imbrium-related ring-fracture system. Silicic volcanic or exposed intrusive materials occur in several circum-Imbrium locations such as the Mairan and Gruithuisen Domes and in ejecta excavated by Aristarchus crater. Perhaps sample 12023,147-10 and some of the other granitic materials sampled at the Apollo 12 site represent rocks similar to the rocks that make up these large silicic rock occurrences.

Seddio, Stephen M.; Jolliff, Bradley L.; Korotev, Randy L.; Carpenter, Paul K.

2014-06-01

91

Structural relationship between gebel qattar granite and the associated uraniferous hammamat sediments, north eastern desert, egypt  

International Nuclear Information System (INIS)

Gebel qattar granite is surrounded at its northern borders by the hammamat sediments of gebel U mm Tawat. The nature of the contact between these two different lithological rock units is thoroughly studied in the field. The contact zone is also subjected to an extensive geological, structural and radiometric studies. It is noteworthy to mention that the hammamat sediments at the contact are occasionally hosting uranium minerals with dark violet fluorite. The study revealed that gebel qattar granite forms a very large granitic intrusion which is forcefully intruded into the older rocks including hammamat sediments. The contact between this granite and its surrounding hammamat sediments is normal intrusive contact. The granites at some peripheral parts are occasionally episynitized and some times hosting uranium minerals. 40 figs, 1 tab

92

Metallogenic aspects of Itu intrusive suite  

International Nuclear Information System (INIS)

The integrated use of geological, geochemical, geophysical and remote sensing data is providing interesting new information on the metallogenic characteristics of the Itu Intrusive Suite. During World War II, up to 1959, a wolframite deposit was mined near the border of the northernmost body (Itupeva Granite). This deposit is formed by greisen veins associated with cassiterite and topaz, clearly linked with later phases of magmatic differentiation. Generally those veins are related to hydrothermal alteration of the granites and the above mentioned shear zone. U, Th and K determinations by field and laboratory gammaspectrometry were used for regional distribution analysis of those elements and its ratios and calculation of radioactivity heat production. In this aspects, the Itupeva Granite is the hottest and presents several anomalies in the Th/U ratio, indicative of late or post magmatic oxidation processes. (author)

93

Gamma-spectrometric surveys in differentiated granites. II: the Joaquim Murtinho Granite in the Cunhaporanga Granitic Complex, Parana, SE Brazil  

International Nuclear Information System (INIS)

Detailed mapping at the NW corner of the large Neo proterozoic Cunhaporanga Granitic Complex (CGC), Parana state, SE Brazil, redefined the Joaquim Murtinho Granite (JMG), a late intrusion in CGC with an exposed area of about 10 km2, made up mainly by evolved 'alaskites' (alkali-feldspar leuco granites). This unit is in tectonic contact with the Neoproterozoic-Eocambrian volcano-sedimentary Castro Group, to the W, and is intrusive into other less evolved granitic units of the CGC to the E. Petrographically, JMG shows mainly mesoperthite and quartz, with subordinate amounts of altered micas and some accessory phases, mainly zircon. The equi to inequigranular granites are usually deformed with cataclastic textures, are often brecciated, and may have miarolitic structures. Formation of late albite, sericite, carbonate and hematite was caused by deuteric and hydrothermal alteration. A gamma-ray spectrometric survey at 231 stations which measured total counts (TC), Ueq K%, eU ppm and eTh ppm was used to construct several direct and derived maps. Compared to neighboring units the JMG has significant anomalies, especially in the TC, %K, eTh and eU maps, although the differences are less obvious in some derived maps. These evolved granites are enriched in these three elements. Geochemical behavior of K, Th and U is used to analyse the results observed in maps. Enhanced weathering under a subtropical climate with moderate to high average temperatures and heavy rainfahigh average temperatures and heavy rainfall affects mainly feldspars and biotite, and may also destabilize most U and Th-bearing accessory phases. Th is most likely retained in restite minerals in soils, being relatively immobile, while part of U may migrate as uranyl ion in oxidizing media. K is especially affected by feldspar alteration to K-free clays (mainly kaolinite), and may be completely leached. Gamma-ray spectrometric methods are valid tools to study facies in granitic rocks, especially in those that are enriched in K, Th and U. (author)

94

Experimental investigation on granite emplacement during shortening  

Science.gov (United States)

We present analogue experiments performed to investigate the emplacement of granitic plutons in a shortening upper crust. The models were made of quartz-sand to simulate the brittle crust and a low-viscosity mixture of silicone and oleic acid to reproduce granitic magmas. Shortening of the models was obtained by a moving wall while a special injection apparatus allowed syn-kinematic magma intrusion from the base of the models. Experimental results show that: (1) space for intrusions is achieved during the movement along thrust faults and mostly coincides with low-pressure areas developed into the thrust-anticlines; (2) intrusion shapes are strictly dependent upon the competition between shortening rate (Sh) and injection rate (Inj). For high Sh/Inj values, plutons were elongated with the long axis parallel to the thrust surfaces; (3) magma migrates horizontally away from the injection point and towards the external sector in the direction of tectonic transport a longer distance for high Sh/Inj values; (4) syn-kinematic emplacement is also controlled by model thickness; an increase in this parameter results in an increase in the pluton plan-view aspect ratio. These results support that the final shape of orogenic plutons emplaced at shallow crustal levels may be strongly controlled by deformational features.

Montanari, Domenico; Corti, Giacomo; Sani, Federico; Del Ventisette, Chiara; Bonini, Marco; Moratti, Giovanna

2010-03-01

95

The Neoproterozoic layered mafic-ultramafic intrusion of Gabal Imleih, south Sinai, Egypt: Implications of post-collisional magmatism in the north Arabian-Nubian Shield  

Science.gov (United States)

The Imleih layered mafic-ultramafic body is a Neoproterozoic intrusion covering about 45 km 2 in southern Sinai. The field relations as well as the fine grained chilled margins indicate that the layered intrusion is younger than the surrounding calc-alkaline syn-tectonic granodiorite and Iqna Shar ,a volcanics and older than the post-tectonic Iqna granite. There is a general consensus that there are no ophiolitic rocks younger than the syn-tectonic granitoids in the Arabian-Nubian Shield (ANS), which supports the non-ophiolitic origin of the Imleih layered intrusion. The studied layered intrusion is tilted to the north, with lower layers (peridotite and pyroxenite) exposed to the south and upper layers (cumulus gabbro and anorthosite) exposed to the north. Imleih rocks are cumulates, dominated by cumulus gabbro with subsequent amounts of peridotite, pyroxenite and anorthosite. Pegmatitic gabbro is locally observed. These rocks are unmetamorphosed. In the peridotite, the Fo content of olivine ranges from 0.81 to 0.83. Clinopyroxenes of the studied rocks range in composition from diopside to augite and have subalkaline affinities. Plagioclase in the cumulus gabbro is mostly bytownite (An 73-82). Two types of spinel are observed, chromite and pleonaste. Chromite has Cr# (Cr/(Cr + Al) of 0.60-0.81 whereas pleonaste have Cr# lower than 0.02. The present study revealed that the mafic-ultramafic complex of Gabal Imleih fractionated from a single batch of high Al-basaltic magma and evolved by fractional crystallization at the base of a Neoproterozoic magma chamber. Olivine and chromite were the first crystallized phases followed by pyroxene and plagioclase. Amphibole appears at nearly the same time as plagioclase. The Imleih mafic-ultramafic body was emplaced post-tectonically in a transitional phase between the calc-alkaline and alkaline magmatism.

Azer, M. K.; El-Gharbawy, R. I.

2011-06-01

96

Uranium rich granite and uranium productive granite in south China  

International Nuclear Information System (INIS)

The paper briefly introduces the differences between uranium rich granite and uranium productive granite in the 5 provinces of South China, and discusses their main characteristics in 4 aspects, the uranium productive granite is highly developed in fracture, very strong in alteration, often occurred as two-mica granite and regularly developed with intermediate-basic and acid dikes. The above characteristics distinguish the uranium productive granite from the uranium rich granite. (authors)

97

Hydrothermal alteration of Hercynian granites, its significance to the evolution of geothermal systems in granitic rocks  

Energy Technology Data Exchange (ETDEWEB)

We discuss geochemical and isotopic ({sup 18}O/{sup 16}O, {sup 2}H/{sup 1}H and {sup 87}Sr/{sup 86}Sr) data recording the hydrothermal alteration of northern Portuguese Hercynian granites by Na-HCO{sub 3}-CO{sub 2}-rich mineral waters. Whole-rock samples from drill cores of Vilarelho da Raia granite have {delta}{sup 18}O values in the +11.47 to +10.10 permille range. The lower values correspond to highly fractured granite samples displaying vein and pervasive alteration. In the pervasive alteration stage, which probably results from a convective hydrothermal system set up by the intrusion of the granites, the metamorphic waters are in equilibrium with hydrous minerals. In contrast, the vein alteration of these granitic rocks was caused by water of meteoric origin. The oxygen ratios between water (W) and rock (R), the so-called W/R ratios, obtained for the open system (where the heated water is lost from the system by escape to the surface) range between 0.05 and 0.11, suggesting that the recrystallization of the veins was influenced by a small flux of meteoric water. Stable isotope analyses performed on the cores show that the vein alteration stage relates to post-emplacement tectonic stresses acting on the granite, probably of late Hercynian age. Our results are consistent with the existence of two separate alteration events (pervasive and vein) caused by hydrothermal waters of different isotopic characteristics. The studies presented in this paper should be viewed as a natural analogue that uses the alteration features observed in a fossil geothermal system at Vilarelho da Raia to assess possible water-rock reactions presently occurring at depth in granitic rocks of the nearby Chaves area. (author)

Marques, Jose M.; Matias, Maria J.; Basto, Maria J.; Aires-Barros, Luis A. [Instituto Superior Tecnico, Centro de Petrologia e Geoquimica, Universidade Tecnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon (Portugal); Carreira, Paula M. [Instituto Tecnologico e Nuclear, Estrada Nacional n 10, 2686 - 953 Sacavem (Portugal); Goff, Fraser E. [Earth and Planetary Sciences Department, Univ. of New Mexico, Albuquerque, NM 87131 (United States)

2010-06-15

98

Petrology and geochemistry of the transamazonian granites of Campo Formoso and Carnaiba (Bahia, Brazil) and of the associated emerald-bearing phlogopites  

OpenAIRE

The granitic massifs of Campo Formoso and Carnaiba are located in the Serra de Jacobina (Bahia, Brazil); they are intrusive at 1,9 Ga in the archean basement of the São Francisco craton, and in the Lower Proterozoic cover. The granitic massifs are formed by multi-stage intrusions of two-micas granites, muscovite-garnet granites and aplopegmatites. Geochemical data show that the Campo Formoso massif is made of two non-comagmatic evolutive suites whereas the Carnaiba massif is made of only one...

Rudowski, Luc

1989-01-01

99

Petrology and geochemistry of the Los Cuartos granite, Tafi del Valle, Tucuman, northwest of Argentina: its integration to the regional magmatic layout  

International Nuclear Information System (INIS)

Los Cuartos Granite crops out on the western flank of the Cumbres Calchaquies, east of Tafi del Valle, Tucuman Province, Argentina. It has a granitic to granodioritic composition, of two micas, being biotite dominant. The granite is medium grained and inequigranular, with rare K-feldspar megacrysts. It contains host-rock xenoliths with different degrees of assimilation. The granite intrusion produced contact metamorphism in the surrounding basement, with development of andalucite porphyroblasts and poikiloblastic biotite. The granite is calk-alkaline and peraluminous, and is K- and P-rich and Ca- and Napoor compared to other granitoids of the region. The pluton shows late-tectonic features with regard to the regional deformation. The granite possibly intruded during the Ordovician (Famatinian Cycle) and its emplacement was structurally controlled by the Tafi Megafracture. Los Cuartos Granite and other intrusive bodies of the region share similar petrographical, geochemical, structural and geochronological characteristics. (Author).

100

The GRANIT spectrometer; Le spectrometre GRANIT  

Energy Technology Data Exchange (ETDEWEB)

The existence of quantum states of matter in a gravitational field was demonstrated recently in the Institut Laue-Langevin (ILL), Grenoble, in a series of experiments with ultra cold neutrons (UCN). UCN in low quantum states is an excellent probe for fundamental physics, in particular for constraining extra short-range forces; as well as a tool in quantum optics and surface physics. The GRANIT is a follow-up project based on a second-generation spectrometer with ultra-high energy resolution, permanently installed in ILL. It will become operational in 2011. The spectrometer consists of several neutron-optics elements and UCN detectors installed on a massive granite table in an aluminium vacuum chamber with a volume of about 1.5 m{sup 3}. 3 types of detectors will be used at the first stage of the GRANIT experiment: {sup 3}He gaseous proportional counters with extremely low background, position-sensitive nuclear-track UCN detectors will be used to study the spatial distribution in quantum states, and real-time position-sensitive detectors with a resolution of a few hundred microns to measure velocity distributions of neutrons in quantum states. The key elements of the GRANIT spectrometer is a set of mirrors to shape/analyze neutron spectra and to store neutrons in quantum states

Baessler, St. [University of Virginia, Charlottesville, VA 22904 (United States); Oak Ridge Nat. Lab., Oak Ridge, TN 37831 (United States); Beau, M.; Kreuz, M.; Nesvizhevsky, V.V. [ILL, 6 rue Jules Horowitz, Grenoble, F-3804(France); Kurlov, V.N. [ISSP, 2 Institutskaia, Chernogolovka, RU-142432 (Russian Federation); Pignol, G.; Protasov, K.V.; Vezzu, F. [LPSC/IN2P3-UJF-INPG, 53 rue des Martyrs, Grenoble, F-38026 (France); Voronin, A.Y. [Lebedev Institute, 53 Leninskii pr., Moscow, RU-119991 (Russian Federation)

2010-10-15

101

Petrogenesis of Triassic granites from the Nanling Range in South China: Implications for geochemical diversity in granites  

Science.gov (United States)

A combined study of whole-rock major-trace elements and Sr-Nd isotopes, zircon U-Pb ages, Hf and O isotopes as well as biotite geochemistry was carried out for Triassic granite intrusions from the Nanling Range in South China. The results provide insights into the effects of source composition and melting conditions on the geochemical diversity of granites. The granites of interest are peraluminous, and contain primary muscovite and tourmaline. They are characterized by high zircon ?18O values of > 9.0‰, high initial 87Sr/86Sr values of ~ 0.7200, and homogeneous ?Nd(t) values of - 11.3 to - 9.8, as well as variable zircon ?Hf(t) values of - 12.2 to - 5.8. Biotite geochemistry is similar to that of common peraluminous granites. An integrated interpretation of these petrological, mineralogical and geochemical data indicates that these granites were derived from partial melting of metasedimentary rocks under variable physicochemical conditions. The differences in whole-rock and biotite geochemistry between the intrusions are ascribed to the variable effects of source heterogeneity and melting temperature. The Luxi intrusion exhibits higher contents of MgO, FeOT, TiO2 and CaO than common melts derived from metasedimentary rocks, tight variations in major-trace elements and homogeneous Sr-Nd isotopic compositions, and homogeneous biotite composition with high Mg# [= Mg / (Mg + Fe) in molar] and lower whole-rock A/CNK values [= Al2O3 / (CaO + Na2O + K2O) in molar]. These can be explained by originating from a relatively mafic metasedimentary source. On the other hand, the geochemical diversity of granites can be caused by the difference in melting temperature in addition to the source heterogeneity. This is suggested by the Xiazhuang and Fucheng intrusions which exhibit similar range of SiO2. Nevertheless, the Fucheng intrusion is ferroan, and high in TiO2, (Na2O + K2O)/CaO, TiO2/MgO, Ga/Al and Zr + Nb + Ce + Y, but low in CaO, MgO and Mg#. Most of its major elements and their ratios are similar to those of A-type granites that were generated from F-rich rocks at high temperatures, consistent with the enrichment of Fe and F in its biotite. Thus, partial melting of a metasedimentary restite at reduced conditions after previous melt extraction is suggested to produce the geochemical feature of A-type granites in the Fucheng intrusion. In contrast, partial melting of fertile metasedimentary rocks would produce normal S-type granites like the Xiazhuang intrusion, with its geochemical variations ascrible to source heterogeneity and differential melting. Therefore, the geochemical composition of granites is primarily dictated by the composition of source rocks in addition to the physicochemical conditions of partial melting.

Gao, Peng; Zhao, Zi-Fu; Zheng, Yong-Fei

2014-12-01

102

SHRIMP zircon U-Pb dating of the mafic and felsic intrusive rocks of the Saza area in the Lupa goldfields, southwestern Tanzania: Implication for gold mineralization  

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Full Text Available The Lupa Goldfield (LGF is one of the eight structural terranes in the NW – SE striking Ubendian Belt of SW Tanzania. The LGF is comprised of granitic gneisses with bands of amphibolites which are intruded by mafic intrusions including gabbros, granodiorites, diorites; and various granites as well as metavol-canics. These rocks are cross-cut by narrow mafic dykes and aplites. SHRIMP zircon U-Pb data are presented for the granodiorite and a mafic dyke that cross-cut the granodiorites in the Saza area of the LGF, with the aim of constraining the mafic and felsic magmatism and their implication to gold mineralization. The zircon U-Pb data shows that the Saza granodiorites were emplaced at 1924 ± 13 Ma (MSWD = 2.6 whereas the cross-cutting mafic dyke yielded a zircon U-Pb age of 1758 ± 33 Ma (MSWD = 0.88. The dated granodiorite sample was in sheared contact with an altered mafic intrusive rock, most likely a diorite, along which an auriferous quartz vein occurs. The 1924 ± 13 Ma age of granodiorites is within error of the reported molybdenite Re-Os age of 1937 Ma determined for the gold mineralization event in Lupa Goldfields. Although auriferous quartz veins are younger than the granodiorites, the more or less similar ages between the emplacement of granodiorites and the mineralizing event indicate that the granodiorites might be the heat source (or driver of hydrothermal fluids responsible for gold mineralization in the Lupa goldfields. This would further suggest that gold mineralization in the LGF is intrusion-related type. The mafic dykes represent the youngest rocks to have been emplaced in the area and hence the 1758 ± 33 Ma age of the mafic dykes conclude the magmatic evolution in the Lupa goldfields during the Palaeoproterozoic.

Shukrani Manya

2012-09-01

103

Nuclide sorption on granite  

International Nuclear Information System (INIS)

Some equilibrium sorption experiments were made to evaluate surface and bulk reactions of granite. The nuclides examined are Cs and Np. The granite samples are sliced as thin as 0.7 to 1.3 mm and crushed samples (< 0.105 mm) are also used. The nuclide amount sorbed on granite of unit weight is dependent on the thickness of samples for both Cs and Np. The model that diffusion porosity decreases with the distance from the wall was proposed to explain these experimental results. Also, the error of measurements was examined. (author)

104

The granite system near Betliar village (Gemeric Superunit, Western Carpathians): evolution of a composite silicic reservoir  

OpenAIRE

Boron- and fluorine-rich highly evolved granites in the Betliar area (Gemeric Unit, Western Carpathians) represent composite intrusion that formed probably during two distinct magmatic episodes. During the first stage, evolved granitic magma originating from an underlying volatile-rich reservoir intruded into an open fault system in the form of sill-like bodies and crystallized as equigranular or medium- to fine-grained rocks. The subsequent volatile flux enhanced post-magmatic alte...

Kubiš M; Broska I

2010-01-01

105

Geochemical geochronology and genesis of granite from Coronel Murta, Northeast of Minas Gerais, Brazil  

International Nuclear Information System (INIS)

Geological, petrographic, geochemical (including rare-earth elements) and geochronological data of the Coronel Murta (Northeast Minas Gerais State) post-tectonic intrusive alkalic granites were summarized in order to discuss their genesis. This paper shows that Coronel Murta granites were generated by anatexis of dominantly metasedimentary rocks, in an ensialic environment, as the late results of an intraplate A-type subduction during the Brazilian Cycle. (author)

106

Research on metallogenic specialization and metallogenic prognosis of granite in Nanling region: a case study of hydrothermal uranium deposit and hydrothermal tungsten-tin deposit  

International Nuclear Information System (INIS)

According to the principles of remote sensing information model and stepwise discriminant analysis, the metallogenic specialization discrimnant model of the intrusions rich in uranium and tungsten-tin was established, based on the data of 339 granite samples which consist of 99 granite samples rich in uranium, 89 granite samples rich in tungsten-tin and 151 granite under estimation in Nanling region. F test results showed that this model was applicable and highly significant for the intrusion estimation. The model was used to judge the uranium bearing or tungsten-tin bearing potential of the under estimated intrusions, and supplied a evidence for the further estimation of metallogenic intrusions. The built model has objectivity and operability, implements the quantitative evaluation for metallogenic specialization, and should play an important role on metallogenic specialization researches. (authors)

107

Chemical characteristics of zircon from A-type granites and comparison to zircon of S-type granites  

Science.gov (United States)

The trace element content in zircons from A-type granites and rhyolites was investigated by using back-scattered electron images and electron microprobe analyses. The studied Proterozoic (Wiborg batholith, Finland and Pará, Amazonas and Goiás states, Brazil) and Variscan (Krušné Hory/Erzgebirge, Czech Republic and Germany) plutons cover a wide range of rocks, from large rapakivi-textured geochemically primitive plutons to small intrusions of F-, Li-, Sn-, Nb-, Ta-, and U-enriched rare-metal granites. While zircon is one of the first crystallized minerals in less fractionated metaluminous and peraluminous granites, it is a late-crystallized phase in peralkaline granites and in evolved granites that may crystallize during the whole process of magma solidification. The early crystals are included in mica, quartz, and feldspar; the late grains are included in fluorite or cryolite or are interstitial. The zircon in hornblende-biotite and biotite granites from the non-mineralized plutons is poor in minor and trace elements; the zircon in moderately fractionated granite varieties is slightly enriched in Hf, Th, U, Y, and HREEs; whereas the zircon in highly fractionated ore-bearing granites may be strongly enriched in Hf (up to 10 wt.% HfO2), Th (up to 10 wt.% ThO2), U (up to 10 wt.% UO2), Y (up to 12 wt.% Y2O3), Sc (up to 3 wt.% Sc2O3), Nb (up to 5 wt.% Nb2O5), Ta (up to 1 wt.% Ta2O5), W (up to 3 wt.% WO3), F (up to 2.5 wt.% F), P (up to 11 wt.% P2O5), and As (up to 1 wt.% As2O5). Metamictized zircons may also be enriched in Bi, Ca, Fe, and Al. The increase in the Hf content coupled with the decrease in the Zr/Hf value in zircon is one of the most reliable indicators of granitic magma evolution. In the zircon of A-type granites, the Zr/Hf value decreases from 41-67 (porphyritic granite) to 16-19 (equigranular granite) in the Kymi stock, Finland, and from 49-52 (biotite granite) to 18-36 (leucogranite) in the Pedra Branca pluton, Brazil. In the in situ strongly fractionated Cínovec cupola (Erzgebirge), the Zr/Hf value decreases from 33-51 in the protolithionite granite at a depth of 1255 m to 7.5-25 in the zinnwaldite granite at a depth of 40 m. At the scale of individual crystals, the Zr/Hf value decreases from 86 to 68 from the cores to the rims of the zircons from the Teplice rhyolite and from 64 to 33 in the zircons from the biotite granite at Krupka, Erzgebirge. The contents of Hf and U in zircon are dependent mainly on the degree of granite fractionation and the nature and volume of the volatile phases and are independent of the A- or S-character of the parental melt. The zircon Zr/Hf ratios 55 and 25 are proposed to approximately distinguish common, moderately evolved and highly evolved granites. Zircons from the moderately and highly evolved granites of A- and S-type can be discriminated on the basis of their HREE content and the U/Th ratios. Nb, Ta, and W are present in zircon from the highly evolved granites from all studied areas, while high As, Bi, and Sc contents are typical only for the Erzgebirge.

Breiter, Karel; Lamarão, Claudio Nery; Borges, Régis Munhoz Krás; Dall'Agnol, Roberto

2014-04-01

108

groundwater saline intrusion classification method  

SCPinfonet

...Plans Groundwater Classification Methodology Saline Intrusion December 2014 1 Groundwater Classification...1 Groundwater Classification Methodology Saline Intrusion December 2014 Introduction All groundwater...Group paper 11b(i)]. Saline Intrusion classification The saline intrusion test assesses if an abstraction...

109

Anisotropy of magnetic susceptibility measurements (AMS) and microfabric analyses from the late Variscan North Schwarzwald Granite complex, SW Germany - first results  

Science.gov (United States)

The North Schwarzwald Granite complex (NSGC) comprises Late Variscan (~325 Ma) S-type granites, which are reasonably well exposed over an area of >600 km2 in the northern Schwarzwald in SW-Germany. The granites intruded migmatitic sillimanite-biotite gneisses and are unconformably covered by younger sedimentary rocks. The NSGC marks a phase of late Variscan partial melting of crustal material postdating high-grade eclogite- and granulite-facies metamorphism. The NSGC comprises biotite, muscovite and two-mica granites as major granite types, which can be further subdivided based on grain size and content of porphyric K-feldspars (`megacryst?). 367 samples from 34 sample locations have been analyzed so far for this ongoing study. Mean susceptibilities vary from 28 to 394x10-6 SI. 94% of the samples display low anisotropies (? 1.1) were obtained from locations close to major NNE-striking Variscan shear zones implying syn-intrusive fault activity. 80% of the samples outline oblate AMS ellipsoids. Magnetic foliations show highly variable orientations and dip angles. The carriers of the susceptibility are mainly paramagnetic micas, which is in agreement with the dominantly oblate AMS-ellipsoids and the relatively low susceptibilities. Samples from the NSGC boundaries show ductile deformed quartz at the thin section scale displaying subgrain formation and rotation and the location of micro shear zones. The presence of ductile deformed quartz indicates significant sub-solidus deformation, but anisotropies remain low (?< 1.1). ? alone is thus not a suitable parameter to distinguish between dominantly hyper-solidus or sub-solidus fabrics and thus microfabric analyses are always required. Meso-scale mylonitic shear zones with variable orientations and shear senses are also present within the granites at the outcrop-scale, which may be related to emplacement processes. The AMS-data outline variable orientations of magnetic foliation and lineation, which - together with field observations and micro-fabric analyses - tentatively indicates multiple more or less, interpenetrated cupolas (or polydiapirs) of similar composition and affected by localized large scale Variscan ductile shear zones.

Grimmer, J.-C.

2009-04-01

110

The petrology and geochemistry of alkaline granites from Nigeria  

Science.gov (United States)

The Nigerian younger granites, as well as the petrologically similar but chronologically older northern centres in Aïr and south Niger, constitute the best example of epidosically migrating mid-plate magmatism. The Nigerian anorogenic ring complexes provide a classic example of alkaline granitoid evolution. Each anorogenic centre represents the exposed roots of an eroded volcano. Volcanic assemblages preserved by caldera collapse at some centres confirm that early erupted liquids evolved from olivine basalt through hawaiite, mugearite and trachyte. Although there are volumetrically abundant rhyolitic ignimbrites, there are no volcanic equivalents of biotite granite. However, at the subvolcanic level biotite granites are extensively mineralized with rich deposits of columbite, sphalerite, cassiterite and wolframite. Related peralkaline granites contain enriched concentrations of ore elements but apart from pyrochlore, thorium-rich monazite, and topaz, most potential ores are contained in alkali amphiboles or alkali pyroxene. Fluid interaction in the granite cupolas has caused subsolidus mineral growth and modified original element abundances. In some instances fluid reaction has been so intense that original granite has been locally converted to albite, microclinite, and greisen. These reactions can be monitored by the new mineral assemblages, the major element chemistry, trace elements (e.g., the rare earths) and isotopically by the initial strontium isotopic ratios.

Bowden, P.; Kinnaird, J. A.

1984-10-01

111

Geochemical, zircon U-Pb dating and Sr-Nd-Hf isotopic constraints on the age and petrogenesis of an Early Cretaceous volcanic-intrusive complex at Xiangshan, Southeast China  

Science.gov (United States)

The Late Mesozoic geology of Southeast China is characterized by extensive Jurassic to Cretaceous magmatism consisting predominantly of granites and rhyolites and subordinate mafic rocks, forming a belt of volcanic-intrusive complexes. The Xiangshan volcanic-intrusive complex is located in the NW region of the belt and mainly contains the following lithologies: rhyodacite and rhyodacitic porphyry, porphyritic lava, granite porphyry with mafic microgranular enclaves, quartz monzonitic porphyry, and lamprophyre dyke. Major and trace-element compositions, zircon U-Pb dating, and Sr-Nd-Hf isotopic compositions have been investigated for these rocks. The precise SHRIMP and LA-ICP-MS zircon U-Pb dating shows that the emplacement of various magmatic units at Xiangshan took place within a short time period of less than 2 Myrs. The stratigraphically oldest rhyodacite yielded a zircon U-Pb age of 135 ± 1 Ma and the overlying rhyodacitic porphyry has an age of 135 ± 1 Ma. Three porphyritic lava samples yielded zircon U-Pb ages of 136 ± 1 Ma, 132 ± 1 Ma, and 135 ± 1 Ma, respectively. Two subvolcanic rocks (granite porphyry) yielded zircon U-Pb ages of 137 ± 1 Ma and 137 ± 1 Ma. A quartz monzonitic porphyry dyke, which represented the final stage of magmatism at Xiangshan, also yielded a zircon U-Pb age of 136 ± 1 Ma. All these newly obtained precise U-Pb ages demonstrate that the entire magmatic activity at Xiangshan was rapid and possibly took place at the peak of extensional tectonics in SE China. The geochemical data indicate that all these samples from the volcanic-intrusive complex have an A-type affinity. Sr-Nd-Hf isotopic data suggest that the Xiangshan volcanic-intrusive complex derived mainly from remelting of Paleo-Mesoproterozoic crust without significant additions of mantle-derived magma. However, the quartz monzonitic porphyry, which has zircon Hf model ages older than the whole-rock Nd model ages, and which has ?Nd(T) value higher than the other rocks, may indicate involvement of a subordinate younger mantle-derived magma in its origin. Geochemical data indicate that the various rocks show variable REE patterns and negative anomalies of Ba, Nb, Sr, P, Eu and Ti in the trace element spidergrams, suggesting that these rocks may have undergone advanced fractional crystallization with separation of plagioclase, K-feldspar and accessory minerals such as allanite. We suggest that this Cretaceous volcanic-intrusive complex formed in an extensional environment, and the formation of the Xiangshan mafic microgranular enclaves can be explained by the injection of mafic magma from a deeper seated mantle magma chamber into a hypabyssal felsic magma chamber at the crustal emplacement levels.

Yang, Shui-Yuan; Jiang, Shao-Yong; Jiang, Yao-Hui; Zhao, Kui-Dong; Fan, Hong-Hai

2011-01-01

112

Heater test 1, Climax Stock granite, Nevada  

International Nuclear Information System (INIS)

We conducted a series of in-situ tests in the Climax Stock, an intrusive granite formation at the Nevada Test Site, to validate the concept of housing a nuclear waste repository in granitic crystalline rock. The thermal properties of the granite were measured with resistance heaters and thermocouple frames that had been emplaced in drilled holes in the floor of a drift 420 m below the surface. Data analysis was performed primarily by comparing the measured and calculated temperature histories, varying conductivity and diffusivity in the calculations until reasonable agreement was achieved. The best-fit value for in-situ conductivity was approximately 3.1 W/m x K, and the deduced value for in-situ diffusivity was approximately 1.2 mm2/s. Anisotropic effects in the thermal field were less than 10%. Permeability was determined by sealing off portions of the drilled holes, using inflatable rubber packers and an air-pressurization system. We then compared the resulting decay in pressure with analytic solutions of the pressure loss from a cylindrical source in an infinite isotropic medium, obtaining a permeability of approximately 1 nanodarcy (nD) at about 300C. As the temperature increased, the permeability decreased to about 0.2 nD at about 500C and became too small to measure (<0.02 nD) at higher temperatures. These tests provided new data on the in-situ properties of a granite typical of the Basin and Range province and significantly advanced our understanding of and ability to perform in-situ thermal and permeability measurements. This knowledge will be of considerable value for future spent-fuel tests

113

Metasomatism of ferroan granites in the northern Aravalli orogen, NW India: geochemical and isotopic constraints, and its metallogenic significance  

Science.gov (United States)

The late Palaeoproterozoic (1.72-1.70 Ga) ferroan granites of the Khetri complex, northern Aravalli orogen, NW India, were extensively metasomatised ~900 Ma after their emplacement, at around 850-830 Ma by low-temperature (ca. 400 °C) meteoric fluids that attained metamorphic character after exchanging oxygen with the surrounding metamorphic rocks. Albitisation is the dominant metasomatic process that was accompanied by Mg and Ca metasomatism. A two-stage metasomatic model is applicable to all the altered ferroan intrusives. The stage I is represented by a metasomatic reaction interface that developed as a result of transformation of the original microcline-oligoclase (An12-14) granite to microcline-albite (An1-3) granite, and this stage is rarely preserved. In contrast, the stage II metasomatic reaction front, where the microcline-bearing albite granite has been transformed to microcline-free albite granite, is readily recognisable in the field and present in most of the intrusives. Some of them lack an obvious reaction interface due to the presence of stage II albite granites only. When studied in isolation, these intrusives were incorrectly classified and their tectonic setting was misinterpreted. Furthermore, our results show that the mafic mineralogy of metasomatised granites has a significant impact on the characterisation of such rocks in the magmatic classification and discrimination diagrams. Nevertheless, the stage I metasomatised granites can be appropriately characterised in these diagrams, whereas the characterisation of the stage II granites will lead to erroneous interpretations. The close spatial association of these high heat producing ferroan granites with iron oxide-copper-gold (IOCG), U and REE mineralisation in the region indicates a genetic link between the metasomatism and the mineralisation. World-class IOCG, U and REE deposits are associated with metasomatised ferroan granites, suggesting that such a relationship may act as a critical first-order exploration target for undiscovered mineral deposits.

Kaur, Parampreet; Chaudhri, Naveen; Hofmann, Albrecht W.; Raczek, Ingrid; Okrusch, Martin; Skora, Susanne; Koepke, Jürgen

2014-06-01

114

Unusual titanium-rich oxide mineral from peralkaline granite of Kigom complex, Northern Nigeria  

Science.gov (United States)

A titanium-rich oxide mineral found in a riebeckite aegirine granite contains, apart from Ti, Fe, and Mn; Zn, Pb, Nb and Ta are also present in variable proportions. From the recalculated chemical structure, reflectivity micro hardness and mineral paragenesis, the oxide mineral is tentatively suggested to belong to the ferropseudo-brookite group. This is the first reported occurrence of such an oxide mineral in the non-orogenic Younger granites of Nigeria.

Badejoko, Thompson A.

115

Greisen deposits associated to carboniferous post-orogenic granites with mineralization potential, Sierra de Fiambala, Catamarca, Argentina  

International Nuclear Information System (INIS)

The Fiambala range is located in the central south part of the province of Catamarca, Western Sierras Pampeanas, Argentina. It is largely conformed by Precambrian metamorphic rocks, a Cambrian granitic intrusive, Ordovician basic and ultra basic rocks and epi zonal Carboniferous granites (Los Ratones, El Salto and Ayacucho Granites). The Carboniferous granites are sub alkaline, weakly peraluminous, high silica (except for the porphyritic facies of Los Ratones granite) and moderately enriched in K. Contents of trace elements and REE indicate that El S alto and Ayacucho granites and the granular facies of Los Ratones granite have characteristics of evolved and differentiated granite associated with hydrothermal systems. The variations of trace elements, particularly Sn, W, U, Rb, Ba, Zr and Sr suggest that they correspond to granites with mineralization potential. Genetically linked to these granites there are Sn, W, U and minor base metals greisen deposits. The hydrothermal process that yield to these deposits involved two main alteration stages, beginning with alkali metasomatism follow by greissenization. According to the isotopic ages the hydrothermal processes postdate about 1 Ma the magmatic activity. The analyses of the granites and the associated greisen deposits confirm that the post orogenic carboniferous magmatism is the major metallogenetic control of the ore deposits from the studied area. This metallogenetic control could be a useful tool in prospecting sil could be a useful tool in prospecting similar deposits in the rest of the Western Sierras Pampeanas. (Author)

116

Caracterización geoquímica del granito El Durazno, extremo norte de la sierra de Velasco, La Rioja / Geochemical characterization of El Durazno granite, Northern Sierrra de Velasco, La Rioja  

Scientific Electronic Library Online (English)

Full Text Available SciELO Argentina | Language: Spanish Abstract in spanish El área de estudio se ubica en el norte de la sierra de Velasco, en la provincia de La Rioja. Está compuesta principalmente por rocas graníticas que cristalizaron durante dos eventos magmáticos principales en el Ordovícico y el Carbonífero. Los granitos más antiguos presentan diferentes grados de de [...] formación y los más jóvenes no están deformados. Los granitos datados como carboníferos hasta el presente en este sector son Asha y San Blas. Este último presenta una zona central más evolucionada químicamente, asociado a mineralizaciones de Sn. El granito El Durazno aflora al sureste del granito San Blas, no está deformado e intruye al ortogneis Antinaco, compuesto por rocas deformadas del Ordovícico. Es un granito postorogénico, peraluminoso y fuertemente diferenciado, con contenidos de Na2O>K2O. Presenta altos contenidos en Rb, Li, W, Cs, Nb y Ta y bajos en Ba, Sr, Y, Zr y Ce. El índice de caracterización geoquímica (GCI) para granitos asociados a mineralizaciones de W da valores positivos mayores que 4. Las tierras raras presentan contenidos totales bajos, entre 5,3 y 15,3 ppm, anomalía negativa de Eu y efecto tetrada convexo. En el borde norte del granito El Durazno existen vetas de cuarzo con wolframita y hematita distribuidas irregularmente que intruyen al ortogneis Antinaco. Tienen rumbo aproximado N-S y una corrida irregular. La ausencia de deformación, relaciones de campo y características geoquímicas indican que el granito El Durazno es un intrusivo muy diferenciado asociado a mineralización de W y de posible edad carbonífera. Abstract in english The studied area is located in the north of the sierra de Velasco, La Rioja province. It is mainly composed of granitic rocks that crystallized during two main magmatic events in the Ordovician and Carboniferous. The older granites have different types of deformation whereas the younger granites are [...] not deformed. Two Carboniferous granites have been dated in this area: Asha and San Blas. The latter has a chemically evolved central zone related to Sn mineralization. The El Durazno undeformed granite outcrops southeast of the San Blas granite, and intrudes into the deformed Ordovician Antinaco orthogneiss. It is a postorogenic, peraluminous and strongly differentiated granite, with contents of Na2O>K2O. It has high values of Rb, Li, W, Cs, Nb and Ta, and low values of Ba, Sr, Y, Zr and Ce. The geochemical characterization index (GCI) for W-bearing differentiated granites is positive with values greater than 4. The REE show low total contents, between 5,3 and 15,3 ppm, negative Eu anomalies and a convex tetrad effect. At the northern border of the El Durazno granite, quartz veins with irregularly distributed wolframite and hematite cross-cut the Antinaco orthogneiss. The veins have irregular north-south strike. The absence of deformation, field relations and geochemical characteristics indicate that the El Durazno granite is a highly differentiated intrusive associated with W mineralization and of possible Carboniferous age.

Miguel A, Báez; Ana S, Fogliata; Steffen, Hagemann; Fernando G, Sardi.

2012-12-01

117

Ion Probe U-Pb dating of the Central Sakarya basement: a peri-Gondwana terrane cut by late Lower Carboniferous subduction/collision related granitic magmatism  

Science.gov (United States)

Our aim here is to better understand the age and tectonic history of crystalline basement units in the Sakarya Zone of N Turkey, north of the Neotethyan ?zmir-Ankara-Erzincan Suture Zone, utilising field, petrographic and ion probe dating, the latter carried out at the University of Edinburgh. One of the largest basement units, Central Sakarya, is dominated by paragneisses and schists that are best exposed between Bilecik and Sar?cakaya, forming a belt ~15 km wide x 100 km long. Smaller outcrops of this basement are exposed further north, for instance in the Geyve area. High-grade metamorphic basement is unconformably overlain by Lower Jurassic-Upper Cretaceous cover sediments of the Sakarya Zone and is in tectonic contact with the Late Palaeozoic-Early Mesozoic Karakaya Complex to the south. Ion-probe U-Pb dating of 89 detrital zircons, separated from one garnet micaschist sample, range from 551 Ma (Ediacaran) to 2738 Ma (Neoarchean). 85% of the ages are > 90 % concordant. Zircon populations cluster at ~550-750 Ma (28 grains), ~950-1050 Ma (27 grains) and ~2000 Ma (5 grains), with smaller groupings at ~800 Ma and ~1850 Ma. The first, prominent population (Neoproterozoic) reflects derivation from a source area related to a Cadomian-Avalonian magmatic arc, likely to be associated with a Cadomian/NE African terrane rather than Baltica (Baltica is known to be magmatically inactive during this period), or Avalonia/Amazonia (in view of the absence of Mesoproterozoic ages in Avalonian-Amazonian terranes). The early Neoproterozoic ages (0.9-1 Ga) deviate significantly from the known age spectra of Cadomian terranes (i.e. Armorican Terrane Assemblage) and instead suggest derivation from an original part of NE Africa. The detrital zircon age spectrum of Cambrian-Ordovician sandstones deposited at the northern periphery of the Arabian-Nubian Shield (i.e. the Elat sandstone) is notably similar to that of the Sakarya basement. The Central Sakarya terrane may have rifted in the Early Palaeozoic, relatively early compared to other E Mediterranean inferred Minoan terranes (e.g. Menderes, Crete, Bitlis), and then accreted to the Eurasian margin, possibly in during Late Palaeozoic time. The Central Sakarya metamorphic basement is cut by a number of granitic intrusions (collectively termed the Sö?üt Granite or Sar?cakaya Granite), three of which were dated in this study. Pink, alkali feldspar-rich granite (Küplü granite) yielded an age of 324.3 ±1.5 Ma. Grey, blastomylonitic biotite granite (Çalt? granite) is dated at 327.2 ± 1.9 Ma. Another granitic body with biotite and amphibole (Borçak granite) yielded a significantly younger age of 319.5 ± 1.1 Ma. Thus, late Early Carboniferous granitic magmatism in the Central Sakarya terrane could have persisted for ? 8 Ma, possibly related to subduction or collision of a Central Sakarya terrane with the Eurasian margin. This work was supported by Y?ld?z Technical University Research Fund (Project No: 29.13.02.01) and a Royal Society Travel Grant.

Ayda Ustaömer, P.; Ustaömer, Timur; Robertson, Alastair. H. F.

2010-05-01

118

Friction on a granite to granite interface  

Science.gov (United States)

Direct shear tests were conducted on a granite to granite interface for the purpose of tracing the evolution of frictional resistance as the initially smooth and polished surface wears during continuing shearing displacement. At the moment when sliding on the freshly manufactured interface starts (first slip), the friction angle is very low, between 15° and 20°, but then it increases with displacement rapidly without reaching a peak in the first test (maximum displacement less than 25 mm). Upon repeated shearing of the same surface (without re-finishing), this process of “displacement-strengthening” continues until a total accumulated displacement of about one half of one meter is reached. At this point, the angle of friction would typically be between 42° and 44°. Once the residual surface was established, the effect of time-related parameters, the duration of stationary contact under constant normal and shear load and variable displacement rate, were investigated. The frictional resistance is shown to increase with decreasing displacement rate and to increase with the duration of stationary contact. At a normal load greater than about one half of one MPa, shear displacement on a residual surface proceeds in an unstable, stick-slip manner. The change from stable to unstable sliding, that can be effected by either decreasing the sliding velocity or increasing the normal load, is not instantaneous, but occurs over a finite amount of displacement.

Lajtai, E. Z.; Gadi, A. M.

1989-01-01

119

Geochemistry and Geochronology U-Pb SHRIMP of granites from Peixoto de Azevedo: Alta Floresta Gold Province; Geoquimica e geocronologia U-Pb (SHRIMP) de granitos da regiao de Peixoto de Azevedo: Provincia Aurifera Alta Floresta, MT  

Energy Technology Data Exchange (ETDEWEB)

The analysis of petrographic, geochemical and geochronological data of granites in the Peixoto de Azevedo region, Mato Grosso, Brazil, in the eastern portion of the Alta Floresta Gold Province, led to the recognition of two granitic bodies bounded by regional major faults and shear zones. In the northwestern portion a body with featured as biotite granodiorite, coarse-grained, with porphyritic to inequigranular texture, metaluminous to peraluminous, high-K calc-alkaline and magnesium character. In the southeastern portion of the area, a biotite monzogranite coarse-grained, with equigranular to porphyritic texture, slightly peraluminous, high-K calc-alkaline and dominantly of ferrous character. U- Pb dating (SHRIMP) showed that the biotite monzogranite has an age of 1869 ± 10 Ma, similar to the Matupa Intrusive Suite, while the biotite granodiorite has an age of 1781 ± 10 Ma, that is the age expected to Peixoto Granite. Both units show patterns of rare earth elements with enrichment of light over heavy and negative Eu anomaly (La{sub N}/Yb{sub N} » 7.6 to 17.31 and ratios Eu/EU{sup ?} between 0.46 – 0.72 for biotite monzogranite and La{sub N}/Yb{sub N} » 7.13 to 29.09 with ratios Eu/Eu{sup ?} between 0.25 - 0.40 for the biotite granodiorite). Trace elements pattern for both present negative anomalies of Ba, P, Ti and Nb indicating an evolution from mineral fractionation and subduction related sources. In this paper, it is suggested that the monzogranite Matupa was developed in mature arc tectonic environment. For the Peixoto Granite, two hypotheses are suggested: (a) it was developed in younger magmatic arc environment associated with the Colider Magmatism or (b) it was generated in extensional tectonic environment during the Columbia Super continent break up. (author)

Silva, Fernanda Rodrigues da; Barros, Marcia Aparecida Sant' Ana; Pierosan, Ronaldo; Pinho, Francisco Edigio Cavalcante; Tavares, Carla; Rocha, Jhonattan, E-mail: geologia.fernanda@gmail.com, E-mail: mapabarros@yahoo.com, E-mail: ronaldo.pierosan@gmail.com.br, E-mail: aguapei@yahoo.com, E-mail: carlageologia@hotmail.com, E-mail: geologojrocha@live.com [Universidade Federal de Mato Grosso (UFMT), Cuiaba, MT (Brazil). Inst. de Ciencias Exatas e da Terra; Rocha, Mara Luiza Barros Pita; Vasconcelos, Bruno Rodrigo; Dezula, Samantha Evelyn Max, E-mail: marapita1@yahoo.com.br, E-mail: brunovasc@gmail.com, E-mail: samanthadezula@gmail.com [Universidade de Brasilia (UNB), Brasilia, DF (Brazil). Programa de Pos-Graduacao em Geologia

2014-09-15

120

The assessment of human intrusion into underground repositories for radioactive waste Volume 1: Main report  

International Nuclear Information System (INIS)

This report has been prepared with the primary objective of establishing a methodology for the assessment of human intrusion into deep underground repositories for radioactive wastes. The disposal concepts considered are those studied in the performance assessment studies Pagis and Pacoma, coordinated by the CEC. These comprise four types of host rock, namely: clay, granite, salt and the sub-seabed. Following a review of previous assessments of human intrusion, a list of relevant human activities is derived. This forms the basis for detailed characterization of groundwater abstraction and of exploitation of mineral and other resources. Approaches to assessment of intrusion are reviewed and consideration is given to the estimation of probabilities for specific types of intrusion events. Calculational schemes are derived for specific intrusion events and dosimetric factors are presented. A review is also presented of the capacity for reduction of the risks associated with intrusions. Finally, conclusions from the study are presented

121

The assessment of human intrusion into underground repositories for radioactive waste Volume 2: Appendices  

International Nuclear Information System (INIS)

This report has been prepared with the primary objective of establishing a methodology for the assessment of human intrusion into deep underground repositories for radioactive wastes. The disposal concepts considered are those studied in the performance assessment studies Pagis and Pacoma, coordinated by the CEC. These comprise four types of host rock, namely: clay, granite, salt and the sub-seabed. Following a review of previous assessments of human intrusion, a list of relevant human activities is derived. This forms the basis for detailed characterization of groundwater abstraction and of exploitation of mineral and other resources. Approaches to assessment of intrusion are reviewed and consideration is given to the estimation of probabilities for specific types of intrusion events. Calculational schemes are derived for specific intrusion events and dosimetric factors are presented. A review is also presented of the capacity for reduction of the risks associated with intrusions. Finally, conclusions from the study are presented

122

The Fanos granite: structure, emplacement and geodynamic significance (Eastern Axios/Vardar Zone, Northern Greece)  

Science.gov (United States)

The Fanos granite occurs in the Peonia Subzone of the Eastern Axios-Vardar Zone in Northern Greece. It is a Late Jurassic (158±1 Ma), N-S trending granite, intruding the Mesozoic back-arc Geuvgeuli ophiolitic complex (Peonia Subzone). It is composed of three main rock types namely aplitic granite, granite and microgranite evolved by fractional crystallization. At the eastern contact of the Fanos granite with the host ophiolitic rocks the initial intrusion character of the granitic bodies is well preserved. On the other hand, the western contact is overprinted by a few meters thick, westward-vergent semiductile thrust zone, probably of Late Jurassic-Early Cretaceous age. For the better understanding of the geotectonic evolution of the broader area, the Fanos granite is compared with the Mid-Late Jurassic Kastaneri volcano-sedimentary formation allocated on the eastern part of the Paikon Massif, on which the Guevgeuli ophiolites were obducted. In our study we address three major topics: a) the origin of the Fanos granite, b) the geochemical correlation between Fanos granite and Kastaneri formation and c) the relationship of the granite with the remnants of an oceanic island-arc or an active continental margin geotectonic setting situated in the Neotethys (=Axios/Vardar ocean). The collected rock samples are granites, aplitic granites, microgranites, rhyolites, quartz diorites, migmatites and amphibolites. These samples were analysed by X-ray fluorence for major and trace elements. The granite shows peraluminous characteristics, high-K calc-alkaline affinities and I-type features. The Sr initial isotopic ratios of the granite range between 0.70519 and 0.70559, while the Nd initial isotopic ratios range between 0.51236 and 0.51239, reflecting EM-I (Enriched Mantle-I) component. The trace element patterns along with the isotopic composition of the rocks indicate absence of continental crustal material contamination. Moreover, the geochemical data imply a common origin between the Fanos granite and the Kastaneri formation. Taking into account our structural and geochemical data along with the existing isotopic and geotectonic data of the broader Axios/Vardar Zone, we suggest that the studied granitic rocks were formed during an intraoceanic-subduction within the Neotethys ocean, approximately at the same time with the amphibolite sole formation, rather than during the evolution of an active continental margin. In the Late Jurassic, a general westward ophiolite obduction on the Pelagonian continental margin, resulted to the thrusting of the Fanos granite together with the obducted ophiolites.

Michail, Maria; Kilias, Adamantios; Koroneos, Antonios; Ntaflos, Theodoros; Pipera, Kyriaki

2014-05-01

123

Interior intrusion detection systems  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this NUREG is to present technical information that should be useful to NRC licensees in designing interior intrusion detection systems. Interior intrusion sensors are discussed according to their primary application: boundary-penetration detection, volumetric detection, and point protection. Information necessary for implementation of an effective interior intrusion detection system is presented, including principles of operation, performance characteristics and guidelines for design, procurement, installation, testing, and maintenance. A glossary of sensor data terms is included. 36 figs., 6 tabs.

Rodriguez, J.R.; Matter, J.C. (Sandia National Labs., Albuquerque, NM (United States)); Dry, B. (BE, Inc., Barnwell, SC (United States))

1991-10-01

124

Options for human intrusion  

International Nuclear Information System (INIS)

This paper addresses options for dealing with human intrusion in terms of performance requirements and repository siting and design requirements. Options are presented, along with the advantages and disadvantages of certain approaches. At the conclusion, a conceptual approach is offered emphasizing both the minimization of subjective judgements concerning future human activity, and specification of repository requirements to minimize the likelihood of human intrusion and any resulting, harmful effects should intrusion occur

125

Network Intrusion Detection System  

Directory of Open Access Journals (Sweden)

Full Text Available Attacks on computers and data networks have become a regular and sophisticated issue. Intrusion detection has shifted its attention from hosts and operating systems to networks and has become a way to provide a sense of security to these networks. The aim of intrusion detection is to detect misuse and unauthorized use of the computer systems by internal and external elements. Typically, Intrusion Detection Systems allow statistical anomaly and rule-based misuse models to detect intrusions as the behavior of the intruding element is considered to be different from the authorized user behavior.

Gopalkrishna N. Prabhu,

2014-04-01

126

The regional geological and structural setting of the uraniferous granitic provinces of Southern Africa  

International Nuclear Information System (INIS)

Uranium-bearing granites, comprising both potentially economic deposits and source rocks for uranium deposits is duricrustal and sedimentary sequences, are confined chiefly to the mobile belts of Southern Africa and to the Cape granites emplaced during late Precambrian times. The direct uranium potential of the mobile belts, i.e. the Damara, Namaqua-Natal and Limpopo belts, decreases with an increase in the age of associated ensialic diastrophism. This review paper is thus mainly confined to the Damara Belt, although a brief discussion of the potential of the Namaqua Belt is presented. Aspects of the Damara Belt that are discussed in detail, with particular reference to the occurrence of uraniferous granite, include regional tectonic setting, stratigraphy, structure, metamorphism and the patterns and origin of the uranium mineralization. Initial concentrations of uranium in basement and Nosib rocks have led, through ultrametamorphism and fractionation, to uraniferous granites of both economic and sub-economic grade. These granites, in turn, have acted as source of secondary mineralization in overlying superficial calcareous and gypsiferous deposits. The Damara Belt thus provides a good example of multicyclic processes of ore formation. With regard to the uraniferous granites of Namaqualand it is concluded that the porphyroblastic gneisses and late-intrusive Concordia granites, although not of direct economic interest, represent major sources of uranium for secondary superficial deposits. Smaller bodies of late-phase differentiates associated with the Concordia granitic gneiss may themselves, however, represent potentially economically viable deposits

127

Geochemical and Rb-Sr isotopic study of Kuilapal granite and Arkasani granophyre from the eastern Indian craton  

International Nuclear Information System (INIS)

Minor intrusive bodies of granite occur along the periphery of the Archaean trondhjemitic batholith of the eastern Indian craton. Small granite bodies intruding low-grade sediments and volcanics also occur north of the Dalma volcanic belt. Of these, Kuilapal granite body is the largest. Petrographic and geochemical characters of the minor granite bodies south of Dalma volcanics are similar to those of Kuilapal granite. On the basis of these characters, Kuilapal granite and Arkasani granophyre are inferred to have been produced by shallow-level fractional crystallisation of a crustally - derived granodiorite melt. Dominance of xenoliths in the Kuilapal granite suggests large-scale assimilation of crustal rocks. A Rb-Sr age of 1638 ± 38 Ma with Sr of 0.72173 ± 0.00156 (MSWD=11.3) has been obtained for the Kuilapal granite. This age is strikingly close to the Rb-Sr age of 1677 ± 11 Ma as obtained for the soda granite of Mosabani. The Rb-Sr age of 1638 ± 38Ma, it seems, is the minimum age of emplacement of Kuilapal granite. A Rb-Sr whole-rock age of 1052 ± 84Ma has been obtained for the Arkasani granophyre. Microstructural and textural evidence in some of the samples indicate deformation-induced and fluid-controlled recrystallization. The emplacement age of the Arkasani granophyre is likely to be older than 1052 Ma. (author). 31 refs., 8 figs., 4 tabs

128

Uranium distribution in the Um Samra-Um Bakra granitic plutons and associated pegmatites, Central Eastern Desert, Egypt  

International Nuclear Information System (INIS)

Um Samra -Um Bakra granitic plutons are located in the central Eastern Desert between latitudes 25 degree 15 and 25 degree 19 N and longitudes 34 degree 03 and 34 deg 11 E. The younger granites in the studied area are subdivided into two varieties, monzogranites and syenogranites. The syenogranites could be considered as uraniferous (fertile) granites, originated from highly fractionated, U-rich magma. They contain from 15.5 to 24.5 ppm uranium and from 20.5 to 25.0 ppm thorium. Both U and Th were essentially concentrated during the magmatic stage in accessory minerals as apatite, fluorite and zircon. The secondary processes as fracturing and alteration processes allowed the meteoric water and hydrothermal solutions to liberate labile uranium and redeposited their loads along micro fractures. Pegmatites show higher U-contents relative to both types of the studied younger granites. Pegmatites could be classified into two separate groups: 1) mineralized pegmatites which are located near the contact of Um Samra younger granites; they possess U-mineralization (kasolite) and 2) non-mineralized pegmatites which are distributed within Um Bakra younger granites themselves; they show lower U-contents relative to the first type. (author)

129

Study on Kalimantan uranium province: The assessment on uranium mineralization of metamorphic and granitic rocks at Schwaner mountains  

International Nuclear Information System (INIS)

Uranium exploration activities done by CEA-BATAN had discovered uranium occurrences as the radiometric and uranium content anomalies at metamorphic and granite rocks of Schwaner Mountains, Kalimantan. A part of the occurrences on metamorphic rocks at Kalan basin has been evaluated and be developed onto follow-up step of prospecting by construction of some drilling holes and an exploration adit. In order to increase the national uranium resources, it is necessarily to extent the exploration activity to out side or nearby of Kalan basin. The goal of this assessment is to understand the uranium accumulation mechanism at Pinoh metamorphic rocks of Kalan Kalimantan and to delineate areas that uranium may exist. The assessment was based on the aspect of geology, anomaly of radioactivity and uranium contents, tectonics and alterations. Pinoh metamorphic rocks which is influenced by Sukadana granite intrusion are the high potential rocks for the uranium accumulation, because the intrusion contains a relatively high of U, Th, Cu, Zn, Nb, Mn, and W. The potential rock distributions are in between G. Ransa granite intrusion at the east and Kotabaru granite intrusions at the west. The mineralizations are categorized as vein type deposits of granitic association

130

The rapakivi granite plutons of Bodom and Obbnäs, southern Finland: petrography and geochemistry  

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Full Text Available The Obbnäs and Bodom granite plutons of southernmost Finland show the typical petrographic and geochemical features of the Proterozoic rapakivi granites in Finland and elsewhere: they cut sharply across the 1900 Ma Svecofennian metamorphic bedrock and have the geochemical characteristics of subalkaline A-type granites. The Bodom pluton is composed of porphyritic granites (hornblende-, hornblende-biotite-, and biotite-bearing varieties and an even-grained granite that probably represent two separate intrusive phases. This lithologic variation does not occur in the Obbnäs pluton, which is almost entirely composed of porphyritic hornblende-biotite granite that gradually becomes more mafic to the southwest. Three types of hybrid granitoids resulting from magma mingling and mixing occur on the southwestern tip of the Obbnäs peninsula. The Bodom granites are syenogranites, whereas the composition of the Obbnäs granite varies from syeno- to monzogranite. The main silicates of both the Bodom and Obbnäs granites are quartz, microcline, plagioclase (An1541, biotite (siderophyllite, and generally also amphibole (ferropargasite or hastingsite. Plagioclase-mantled alkali feldspar megacrysts are absent or rare. The accessory minerals are fluorite, allanite, zircon, apatite, and iron-titanium oxides; the Obbnäs granite also contains titanite. The Bodom and Obbnäs granites are metaluminous to weakly peraluminous, with average A/CNK of 1.00 and 1.05, respectively, have high Fe/Mg (average FeOtot/[FeOtot+MgO] is 0.94 for the Bodom and 0.87 for the Obbnäs granites, and high Ga/Al (3.78 to 5.22 in Bodom and 2.46 to 4.18 in Obbnäs. The REE contents are high with LREE-enriched chondrite-normalized patterns and moderate (Obbnäs to relatively strong (Bodom negative Eu-anomalies. The Obbnäs granite is enriched in CaO, TiO2, MgO, and FeO, and depleted in SiO2 and K2O compared to the Bodom granites. Also, there are differences in the Ba, Rb, and Sr contents of the two plutons (Ba and Sr higher, Rb lower in Obbnäs that cannot easily be traced to single parental granite magma. These features, together with the presence of titanite in the Obbnäs pluton, suggest different sources for the granites of the two plutons: a potassium feldspar-rich source for Bodom and potassium feldspar-poor for Obbnäs.

Kosunen, P.

1999-12-01

131

Mushy magma processes in the Tuolumne intrusive complex, Sierra Nevada, California  

Science.gov (United States)

Debates continue on the nature of volcanic-plutonic connections and the mechanisms of derivation of large volcanic eruptions, which require large volumes of magma to be readily available within a short period of time. Our focus to understand these magma plumbing systems has been to study the nature of their mid-to upper crustal sections, such as the 1,000 km2, 95-85 Ma old Tuolumne intrusive complex in the Sierra Nevada, California, USA. The Tuolumne intrusive complex is a great example where the magma mush model nicely explains observations derived from several datasets. These data suggest that a magma mush body was present and may have been quite extensive especially at times when the Tuolumne intrusive complex was undergoing waxing periods of magmatism (increased magma input), which alternated with waning periods of magmatism (decreased magma addition) and thus a smaller mush body, essentially mimicking in style periodic flare-ups and lulls at the arc scale. During waxing stages, magma erosion and mixing were the dominant processes, whereas waning stages allowed mush domains to continue to undergo fractional crystallization creating additional compositional variations. Over time, the imprint left behind by previous waxing and waning stages was partly overprinted, but individual crystals successfully recorded the compositions of these earlier magmas. Waxing periods in the Tuolumne intrusive complex during which large magma mush bodies formed are supported by the following evidence: 1) Hybrid units and gradational contacts are commonly present between major Tuolumne units. 2) CA-TIMS U/Pb zircon geochronology data demonstrate that antecrystic zircon recycling took place unidirectional from the oldest, marginal unit toward the younger, interior parts of the intrusion, where increasing zircon age spread encompasses the entire age range of the Tuolumne. 3) The younger, interior units also show an increasing scatter and complexity in geochemical element and isotope whole rock data. 4) Single mineral geochemistry suggests that this increased heterogeneity in the interior of the complex is likely caused by the presence of mixed mineral populations that acquired their compositional zoning in magmas different than the one they most recently crystallized in. 5) Mixed mineral populations have also been found in places of local magma mixing (e.g., tubes and troughs), and 6) oscillatory trace element zoning in K-feldspar phenocrysts most likely represents magma replenishment. All of these phenomena suggest a fairly dynamic environment of magma replenishment, magmatic erosion and extensive mixing at the locus of chamber growth. Magma replenishment subsided after episodic flare-ups and the magma mush dominantly underwent fractional crystallization and magmatic fabric formation during waning stages, when it was capable of preserving the evidence at map to crystal scale, lacking any later overprint by mixing. Fractionation related evidence is apparent in the presence of 1) map to outcrop scale leucogranite lenses and dikes in all major Tuolumne units (including the Johnson Peak granite itself), 2) the concentric compositional zonation of magmatic lobes (e.g., southern Half Dome lobe), 3) local crystal accumulations and widespread schlieren, and 4) fractionation related single mineral element zoning.

Memeti, V.; Paterson, S. R.

2012-12-01

132

The missing link between granites and granitic pegmatites  

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Full Text Available In this contribution we provide evidence for the extraction of volatile and incompatible element enriched melts from common granites. This provides a mechanism showing that at least a large proportion of granitic pegmatites could be genetically directly connected to a main granite body. In granites there are often two principal types of melt inclusions: (i those that represent the bulk chemistry of the granite and (ii those with very different compositions. In the Variscan Erzgebirge granites, the second type is characterized by the abundance of fluorine. However, in other geodynamic settings inclusions in granites can contain high concentrations of other elements which may take over the function of fluorine. From textural relationships the second inclusion type represents intergranular melts enriched in all elements incompatible with the ideal haplogranite system. Due to the high volatile content of such melts, the viscosity can be several orders of magnitude lower than the quasi-solid bulk system and can therefore move rapidly through the partially or totally crystallized host, and flow together into a separate system forming pegmatite bodies inside or outside the granite body. Another important effect of the high volatile content is the phase separation resulting from the speciation changes OH- ? H2O or CO32- ? CO2 due to temperature and/or pressure changes at different locations within the granite-intergranular melt system. Since melt inclusions provide a means of conserving original un-degassed compositions, they provide important evidence for closing the gap between granites and granitic pegmatites.The paper is dedicated to two Czech colleagues - Petr ?erný and Milan Novák - who have devoted their lives to the study of granitic pegmatites.

Thomas R

2013-07-01

133

Potassium-argon ages of the Amritpur granite, District Nainital, Kumaun Himalaya and its stratigraphic position  

International Nuclear Information System (INIS)

Potassium-argon ages of muscovite and biotite, separated from the Amritpur granite, District Nainital, Kumaun Himalaya, determined in the 'Geochronology Laboratory' of the IGEM Institute of the USSR Academy of Sciences, Moscow, are 1880 +- 40 m.y. and 1330 +- 40 respectively. The granitic body apparently shows intrusive relationship with quartzite-metavolcanic association of the Bhimtal-Bhowali area of which the latter has given a whole rock K-Ar age of 228 +- 10. These reveal that the Amritpur granite is composite in nature intruded in Middle Proterozoic Period (1880 +- 40 m.y.) and later remobilised at different periods with the development of tourmaline granite in the peripheral parts, as the latest phase. (author)

134

Contribution to the uranium geochemistry on granites in Ecuador  

International Nuclear Information System (INIS)

This work aims to define the position of two of Ecuador granitic deposits within the field of the geochemistry of granites in general and of the geochemistry of uranium in particular. The regions concerned are: The Bonita and ABITAGUA. For each range the petrochemical framework is first of all determined and then the degree of chemical homogeneity of rocks is evaluated. In the petrochemical groups thus obtained the geochemical behaviour of the uranium is studied. From the viewpoint of the geochemistry of the granites under investigation, a comparison of the laws of distribution of the mayor elements in two ranges shows up a covergence of average composition which was not anticipated by geological and petrografic considerations alone. The statistical and geochemical distribution laws of the total uranium as a function of petrochemical variations are established. A study of chemical forms of uranium in the rocks has drawn an attention to the qualitative and quantitative importance of the faction of uranium soluble in delute acids. We have therefore reconsidered on the one hand, the laws of distribution of the insoluble and we have justified on the other hand the interest presented by the soluble post magmatic phenomena which makes possible to find a genetic connection between the uraniferous deposits and the intrusive massifs. Finally we have given tables of analytic composition total of the granites. (Author)

135

U-Pb ages and Nd isotope characteristics of the lateorogenic, migmatizing microcline granites in southwestern Finland  

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Full Text Available U-Pb ages and whole-rock Nd isotope data have been obtained from the Paleoproterozoic lateorogenic migmatizing microcline granites of southwestern Finland. Isotope dilution and ion microprobe U-Pb data on zircons and monazites show that the age spectrum of these granites is at least 1.85-1.82 Ga. Commonly, zircons and monazites record the same ages. The age variation in the Veikkola granite area is of the order of 25 Ma and indicates that this seemingly homogeneous granite consists of two separate intrusions. The zircons of the lateorogenic granites are pervasively altered and conventional U-Pb results are commonly discordant. The ion microprobe studies reveal that the granites contain very few inherited zircons with preserved original U-Pb isotope ratios, with the exception of the Oripää granite. Initial ?Nd values, mostly in the range of ?0.5 to ?1.0, imply a moderate input of older crustal material into most of the lateorogenic granites. A shift from more juvenile to less radiogenic Nd isotope composition is observed from north to south, and the variation pattern of ?Nd values of the lateorogenic granites is thus similar to that of the surrounding synorogenic granitoid rocks.

Matti Kurhila

2005-01-01

136

The U-fertility criteria applied to the El Sela granite, Eastern Desert, Egypt  

International Nuclear Information System (INIS)

El Sela area is located in the southern Eastern Desert of Egypt, between Latitudes 22 deg. 13' and 22. deg 19' N and Longitudes 36 deg. 11' and 36 deg. 15' E, about 30 km south west of Abu Ramad City. It occupies about 73.5 km2. For a long time the granite massifs have been considered as resulting from the diapiric emplacement of large magma bodies. Recent studies increasingly show that most granite plutons in fact results from successive accretion of multiple injections of highly variable sizes, not always co-genetic and with highly variable metallogenic potential. Such a conception has very important consequences in exploration because the mineralization may be genetically related only to specific magma intrusion within the large granite complex as shown in Kab Amiri granite central Eastern Desert of Egypt for episyenites and in the Saint Sylvestre granite in the French Massif Central for vein type uranium mineralization. Therefore, detailed mapping and characterization of the different granite phases is decisive to define the most fertile parts of granite plutons for the occurrence of mineralization on which the exploration has to be focused. Such a concept is particularly applicable in the granite plutons of the Eastern Desert of Egypt where outcropping conditions are excellent. The fertility of a granitic pluton is mostly related to the extent of the overlap between the magmatic uranium enrichment, hydrothermal reworking through open fracture system an reworking through open fracture system and the existence of a suitable reservoir for the leached metals and followed eventually by a supergene enrichment phase. The northern part of El Sela granite complex was identified as the most fertile part where many granite intrusions are crosscut by long and wide shear zones associated with a series of alteration processes. The studied example is the ENE-WSW shear zone located in the northern part of El Sela granite pluton. The uranium mineralizations are the result of a succession of reactions between the rocks or minerals and the fluids. Hence, we have carried out detailed geologic and tectonic mapping coupled with laboratory mineralogical and geochemical studies. Field observations has shown that Gabal El Sela granites are highly weathered, cavernous and exposed as low to moderately separated hills which forms the remnants of a circular shaped granite pluton composed of at least two main different granite intrusions. The detailed geological and tectonic studies have shown that El Sela area was affected by at least nine successive tectonic events. These events are reflected by the high fracture intensity and consequently the intense weathering of the granite. It was proposed that the complex magmatic and tectonic history of the northern part of the El Sela granitic complex is highly fertile and represent a promising target for the occurrence of uranium ore deposits which are must be tested by a drilling program to complete the geophysical subsurface studies

137

The GRANIT spectrometer  

Energy Technology Data Exchange (ETDEWEB)

The existence of quantum states of matter in a gravitational field was demonstrated recently in the Institut Laue-Langevin (ILL), Grenoble, in a series of experiments with ultra cold neutrons (UCN). UCN in low quantum states is an excellent probe for fundamental physics, in particular for constraining extra short-range forces; as well as a tool in quantum optics and surface physics. The GRANIT is a follow-up project based on a second-generation spectrometer with ultra-high energy resolution, permanently installed in ILL. It has been constructed in framework of an ANR grant; and will become operational in 2011.

Baessler, Stefan [ORNL; Beau, M [ Inst Max Von Laue Paul Langevin, F-38042 Grenoble 9, France; Kreuz, Michael [ Inst Max Von Laue Paul Langevin, F-38042 Grenoble 9, France; Nesvizhevsky, V. [ Inst Max Von Laue Paul Langevin, F-38042 Grenoble 9, France; Kurlov, V [Institute of Solid State Physics, Russian Ac. Sci., Chernogolovka, Moscow, Russi; Pignol, G [LPSC IN2P3 UJF INPG, R-38026 Grenoble, France; Protasov, K. [LPSC IN2P3 UJF INPG, R-38026 Grenoble, France; Vezzu, Francis [LPSC IN2P3 UJF INPG, R-38026 Grenoble, France; Voronin, Vladimir [Institute of Metal Physics, Russia

2011-01-01

138

The GRANIT spectrometer  

Science.gov (United States)

The existence of quantum states of matter in a gravitational field was demonstrated recently in the Institut Laue-Langevin (ILL), Grenoble, in a series of experiments with ultra cold neutrons (UCN). UCN in low quantum states is an excellent probe for fundamental physics, in particular for constraining extra short-range forces; as well as a tool in quantum optics and surface physics. The GRANIT is a follow-up project based on a second-generation spectrometer with ultra-high energy resolution, permanently installed in ILL. It has been constructed in framework of an ANR grant; and will become operational in 2011.

Baessler, Stefan; Beau, Mathieu; Kreuz, Michael; Kurlov, Vladimir N.; Nesvizhevsky, Valery V.; Pignol, Guillaume; Protasov, Konstantin V.; Vezzu, Francis; Voronin, Aleksey Yu.

2011-10-01

139

Laser surface blasting of granite  

Science.gov (United States)

Granite stones have been used from immemorial times as structural element for the public woks or for the construction of every kind of buildings. At present, granite stones are being used widely for the covering of facades and also as paving and flooring elements, polished being the most commonly used surface finish type.

Pou, Juan; Soto, R.; Trillo, C.; Doval, Angel F.; Boutinguiza, M.; Lusquinos, F.; Quintero, F.; Perez-Amor, Mariano

2001-08-01

140

Yeguang granite and uranium metallogeny  

International Nuclear Information System (INIS)

The geological, petrologic and geochemical characteristics of rock body of yeguang granite are discussed with emphasis on clarification of occurrence of uranium in rock body and uranium deposit characteristics related to rock body, based on extensive field observations and laboratory test. View points are presented that granite refers to genetic series of terrestial crust transformation tye and uranium deposit is hot water deposit

141

Petrology and geochemistry of the Los Cuartos granite, Tafi del Valle, Tucuman, northwest of Argentina: its integration to the regional magmatic layout; Petrologia y geoquimica del granito Los Cuartos, Tafi del Valle, Tucuman, noroeste de Argentina: integracion al esquema magmatico regional  

Energy Technology Data Exchange (ETDEWEB)

Los Cuartos Granite crops out on the western flank of the Cumbres Calchaquies, east of Tafi del Valle, Tucuman Province, Argentina. It has a granitic to granodioritic composition, of two micas, being biotite dominant. The granite is medium grained and inequigranular, with rare K-feldspar megacrysts. It contains host-rock xenoliths with different degrees of assimilation. The granite intrusion produced contact metamorphism in the surrounding basement, with development of andalucite porphyroblasts and poikiloblastic biotite. The granite is calk-alkaline and peraluminous, and is K- and P-rich and Ca- and Napoor compared to other granitoids of the region. The pluton shows late-tectonic features with regard to the regional deformation. The granite possibly intruded during the Ordovician (Famatinian Cycle) and its emplacement was structurally controlled by the Tafi Megafracture. Los Cuartos Granite and other intrusive bodies of the region share similar petrographical, geochemical, structural and geochronological characteristics. (Author).

Lopez, J.P.; Bellos, L.I.

2010-07-01

142

Petrogenesis of Karamaili alkaline A-type granites from East Junggar, Xinjiang (NW China) and their relationship with tin mineralization  

International Nuclear Information System (INIS)

Several types of granites including alkaline granites and alkali feldspar granites are distributed in the Karamaili tectonic belt of East Junggar, Xinjiang, China. Some medium-small tin deposits are located within or near the contact zones of the granitic intrusions. The alkaline granites share all the features commonly observed in peralkaline A-type granites. They contain alkalic mafic minerals such as riebeckite and aegirine; have high contents of SiO2, alkalis, Rb, Th, Zr, Hf, REE (except Eu), and high ratios of FeO/MgO and Ga/Al; and show strong depletions in Ba, Sr, Eu in the spidergrams. Laser ablation-ICPMS U-Pb zircon geochronology indicates a crystallization age of ca. 305 Ma for the granites; TIMS analyses of the granites found high ?Nd(T) values of +5.9 to +6.5. Considering their geochemical features, alkaline granites most likely formed by fractional crystallization of graodioritic magmas, which were probably produced by partial melting of lower crustal basaltic to andesitic rocks formed from oceanic crustal materials that were deeply buried during late Palezoic subduction and accretion. Six molybdenite samples from the Sareshike tin deposit in East Junggar yielded an isochron age of 307±11 Ma (2?) and a weighted mean model age of 306.5±3.4 Ma, consistent with zircon U-Pb ages of the alkaline granites. Low Re contents (0.323-0.961 ppm) in the molybdenite suggest that they originated from crustal sources related to the alkaline graal sources related to the alkaline granites. Considering their identical ages, close spatial distribution, and similar sources, we argue that the A-type granites have a genetic relationship with the tin mineralization, and that the same association may be important elsewhere. (author)

143

The density of dry and hydrous granitic magmas  

Science.gov (United States)

Large volumes of granitic magmas form through partial melting of the lower crust and are subsequently emplaced in the higher crustal levels [1]. In addition, granite-like liquids may form through partial melting of subducted sediments [2] or as an end-product of magmatic differentiation [3]. Moreover, water rich magmas of granitic composition are a major source of explosive volcanism. The physical properties of granitic melts, and particularly their density, are key controls on the migration rate and emplacement depth of granitic intrusions. However, because of the high viscosity of granitic liquids, density and compressibility measurements with the sink/float method and sound velocity measurements are challenging. As a result, the density and compressibility of dry and volatile-bearing granitic liquids is poorly constrained, particularly for the pressure-temperature conditions relevant for their formation and emplacement. In this study, we present in situ experimental data on the density of dry and hydrous haplogranitic melts (5 and 10 wt% water) at pressure and temperature conditions relevant for the crust and the subducting slab (1.0-2.7 GPa, 1350-1720 K). The experiments were performed with a panoramic Paris-Edinburgh press installed at the ID27 beamline of ESRF. The samples were contained in a cylindrical diamond capsule, capped with a platinum disk on either side, surrounded by hexagonal boron nitride (hBN) and placed inside a graphite heater and boron epoxy gasket. Pressure and temperature were determined from the X-ray diffraction patterns of hBN and platinum using the double-isochore method [4]. The density of the melts was determined from the X-ray absorption contrast between the sample and the diamond capsule (Mo edge, 20 keV). The molten state of the sample at the condition of the density measurements was verified by X-ray diffraction. The run products were analyzed by electron microprobe and infrared spectroscopy to verify the chemical composition and volatile content of the samples. Our results, combined with literature data on granite melt density at atmospheric pressure, provides the first experimentally derived equation of state of dry and hydrous granitic liquids at crustal and upper mantle conditions. This equation of state enables the prediction of the partial molar volume of water and granite melt density for the pressures, temperatures and water contents relevant for partial melting in the lower crust, melt migration through the middle crust and the emplacement of intrusions in the upper crust. [1] N. Petford, A.R. Cruden, K.J.W. McCaffrey, J.-L. Vigneresse, 2000, Nature, 408, 669. [2] Y. Tatsumi, 2000, Geology, 29, 323. [3] N.L. Bowen, 1956, The evolution of igneous rocks. [4] W.A. Chrichton, M. Mezouar, 2002, High Temp.-High Press, 34, 235.

Malfait, W. J.; Sanchez-Valle, C.; Seifert, R.; Petitgirard, S.; Perrillat, J.

2011-12-01

144

Geology of the Northern part of the Strath Ossian Granite, Scotland  

International Nuclear Information System (INIS)

The Strath Ossian Granite is made up of granodiorite, dark, variable 'granodiorites' interpreted as mobilised diorite or basic material, appinite and porphyritic granodiorite. Huge rafts of psammitic metasediments occur within the mass and three fracture-zones and numerous dykes, dominantly of porphyrite, cut across it in a north-easterly direction. Granite emplacement may have occurred in stages, early batches being xenolith-rich and later ones xenolith-poor. New batches were intruded centrally, which created strong radial stresses, sufficiently strong to make room for the intrusion by forcing the metasedimentary country rocks downwards and aside. (author)

145

Nuclear techniques used in the localization of fracture zone from granites of Itu-SP  

International Nuclear Information System (INIS)

Nowadays there are many geophysical techniques of rock fractures mapping as GPR, electromagnetic and dipole-dipole geoelectrical sounding. These methods don't give information about the content of fracture zone, that can be fulfilled of clay. Using nuclear methods as gamma spectrometry and radon emanometry become possible to identify the nature of mineral composition of fracture material and to study the freshwater circulation using the radon transport by water. In this work the integration of nuclear, GPR and geoelectric techniques in Itu granitic intrusive became very interesting because it was possible to find and identify fracture in granitic rock with clay and freshwater content. (author)

146

Microprobe monazite dating and the ages of some granitic and metamorphic rocks from southeastern Brazil  

International Nuclear Information System (INIS)

Electron microprobe monazite crystallization ages are presented for selected granite and metamorphic rock samples from the Socorro and Guaxupe Nappes and the Alto Rio grande and Ribeira Belts, southeastern Brazil. Results are consistent with ages close to 625 Myr of the main metamorphic episode in the nappe structures. Anatetic granite magmatic events in these terranes and in the Alto Rio Grande Belt were roughly coeval, most samples sharing ages between 610-625 (± 15) Myr. A crust-derived granite and a granite contact aureole from the Ribeira Belt have ages of 600-608 (± 15) Myr., suggesting that the main granite magmatism in this belt was somewhat younger, probably contemporaneous with the late orogenic phase in the nappe domains. Some regional and granite samples from all these terranes point to possible inheritance or incompletely monazite grains and intra-grain domains giving older ages, up to 690 Myr. The microprobe age results agree very well with independent isotopic data, reinforcing the applicability of the method to highlight an overall picture of main geochronological trends within the continental crust. The high spatial resolution of the probe should play an important role in understanding geochronological patterns of metasedimentary rocks and related migmatites and granites, as these rocks and their minerals often present chemical and isotopic domains related to contrasting geological events, not always recognized by conventional dating schemes. (authod by conventional dating schemes. (author)

147

The Torres del Paine intrusion as a model for a shallow magma chamber  

Science.gov (United States)

The shallow magmatic Torres del Paine Intrusive Complex (TPIC) belongs to a series of sub-volcanic and plutonic igneous bodies in Southern Chile and Argentina. This trench-parallel belt is located in a transitional position between the Patagonia Batholith in the West, and the alkaline Cenozoic plateau lavas in the East. While volumetrically small amounts of magmatism started around 28 my ago in the Torres del Paine area, and a second period occurred between 17-16 Ma, it peaked with the TPIC 12.59-12.43 Ma ago. The spectacular cliffs of the Torres del Paine National park provide a unique opportunity to study the evolution of a very shallow magma chamber and the interaction with its host rocks. Intrusion depth can be estimated based on contact metamorphic assemblages and granite solidus thermobarometry to 750±250 bars, corresponding to an intrusion depth of ca. 3km, ca. 500m above the base of the intrusion. Hornblende thermobarometry in mafic rocks agrees well with these estimates (Leuthold et al., 2014). The TPIC is composed of a granitic laccolith emplaced over 90ka (Michel et al., 2008) in 3 major, several 100m thick sheets, forming an overall thickness of nearly 2 km. Contacts are sharp between sheets, with the oldest sheet on the top and the youngest on the bottom (Michel et al., 2008). The granitic laccolith is under-plated by a ca. 400m thick mafic laccolith, built up over ca. 50ka (Leuthold et al. 2012), constructed from the bottom up. Granitic and mafic sheets are themselves composed of multiple metric to decametric pulses, mostly with ductile contacts between them, resulting in outcrop patterns resembling braided stream sediments. The contact of the TPIC with the Cretaceous flysch sediments document intrusion mechanism. Pre-existing sub-horizontal fold axes are rotated in the roof of the TPIC, clearly demonstrating ballooning of the roof; no ballooning was observed in the footwall of the intrusion. Extension during ballooning of the roof is indicated by dykes emanating from the roof of the intrusion into the host rocks. The dykes are perpendicular to the contact, radially shooting into the country rocks. Since the oldest granite is found in the roof, it is also permeated by dykes of successive intrusions. Contact metamorphism can be used to constrain the granite intrusion temperature to ca. 1000°C. Intrusion occurred in multiple pulses along the granite-host rock contact, in rapid succession, before significant cooling occurred in the aureole. Hydration of the biotite and feldspar of the immature sediments in the outer aureole contributed significantly to the overall thermal signature of the host-rock-TPIC system. In contrast, stable isotopes do not document significant fluid circulation. Leuthold, J., Müntener, O., Baumgartner, L., Putlitz, B., Ovtcharova, M., Schaltegger, U. (2012) Time resolved construction of a granitic to mafic laccolith (Torres del Paine, Patagonia). Earth Plan Sci Lett. 325. 85-92 Leuthold J., Müntener O., Baumgartner L.P., Putlitz B., (2014) Recycling of mafic crystal mush, transport and emplacement in the Torres del Paine mafic complex (Patagonia). J. Petrology; accepted pending revision Michel, J., Baumgartner, L.P. Putlitz, B., Ovtcharova, M., Schaltegger, U. (2008) Incremental growth of a shallow crustal laccolith over 80 kyrs: the Torres del Paine Granite, Patagonia. Geology vol. 36, 459-462

Baumgartner, Lukas; Bodner, Robert; Leuthold, Julien; Muntener, Othmar; Putlitz, Benita; Vennemann, Torsten

2014-05-01

148

Crustal development in relation to granitic magmatism in regard to D/H partition between coexisting hornblende and biotite in the Svecofennian belt  

Directory of Open Access Journals (Sweden)

Full Text Available Tie-lines in the ?D-XFe diagram of hornblende and biotite in Japanese island arc granites give commonly a similar slope to that derived from the equation of Suzuoki-Epstein's experimental work ( 1976. This indicates that in the process of granite intrusion in the island arc environment, the water/rock ratio is high enough to allow the presence of molecular water within and around the rock mass crystallizing from the magma. However, the tie-lines of the anorogenic rapakivi granites of Finland (age 1.65-1.54 Ga are quite different from those of island arc granites, i.e. the ?D of hornblende is much lower than that of biotite and the XFe values of both of the minerals are almost the same and high (0.8-0.9. Thus, the tie-lines are nearly vertical. Moreover, the OH contents of hornblende and biotite are very low and this suggests the absence of molecular water in the ascending and crystallizing granitic magma. This probably suggests that the D/H fractionation factor between the hydrous silicates and hydroxyl (OH in the magma without molecular water is different from that of the island arc granites with plenty of molecular water. For the Svecofennian granitic rocks which are older than the rapakivi, e.g. the Turku, Uppsala, Vänge and Revsund masses, the ?D-XFe relationships of hornblende and biotite change systematically following the chronological order of the intrusion. The ?D-XFe relationships of the granitic rocks around Turku are close to those of the island arc granites, those of the Uppsala and Vänge granites show the intermediate patterns between the Turku and Revsund, and those of the Revsund granites are rather similar to rapakivi. It is considered that the geological settings of granitic magmatism in the Svecofennian belt of the Baltic shield developed from a more mobile to a more continental one.

Kuroda, Y.

1993-12-01

149

Li in minerals from the Ilimaussaq alkaline intrusion, South Greenland  

Energy Technology Data Exchange (ETDEWEB)

Li was analysed by instrumental neutron activation analysis and Cerenkov counting in 120 mineral samples (30 species) from the Ilimaussaq alkaline intrusion, South Greenland. More than 0.23 wt.% Li (0.5 wt.% Li{sub 2}O) is found in polylitionite, meptunite, riebeckite, Na-cookeite, ephesite, arfvedsonite, gerasimovskite and astrophyllite. Arfvedsonite (200-2500 ppm Li) carreis the bulk of Li in most of the highly alkaline rocks. Li-Mg and Li-F relations indicate that the distribution of Li is controlled by the structure of minerals, their absolute contents of Mg and F and the fractionation stage within the intrusion. Li is probably linked with F in the fluid state and this linkage continues into crystallising phases where Li occupies sites which also accommodate Mg. Li/Mg and LI/F ratios of Ilimaussaq rocks and minerals are higher than in equivalent materials from the Lovozero intrusion (Kola, Russia). The Li-Mg-Fe{sup 2+} geochemical association at Ilimaussaq (Fe{sup 2+}>>Mg) and Lovozero (Fe{sup 2+}mG) contrasts with the commercially important Li-rich but Mg-Fe{sup 2+}-poor association found in certain granite pegmatites and greisenised granites. (au) (43 refs.).

Bailey, J.C.; Bohse, H.; Gwozdz, R.; Rose-Hansen, J. [Division for Petrology, Geological Institute, Copenhagen (Denmark)

1993-12-01

150

Uranium enriched granites in Sweden  

International Nuclear Information System (INIS)

Granites with uranium contents higher than normal occur in a variety of geological settings in the Swedish Precambrian, and represent a variety of granite types and ages. They may have been generated by (1) the anatexis of continental crust (2) processes occurring at a much greater depth. They commonly show enrichement in F, Sn, W and/or Mo. Only in one case is an important uranium mineralization thought to be directly related to a uranium-enriched granite, while the majority of epigenetic uranium mineralizations with economic potential are related to hydrothermal processes in areas where the bedrock is regionally uranium-enhanced. (Authors)

151

Early Paleoproterozoic (2.5-2.0 Ga) A-type granite associations  

Science.gov (United States)

A-type granites (including their volcanic equivalents) and related rocks (mafic intrusions, massif-type anorthosite, basaltic dikes and lavas, rare alkaline rocks) form a conspicuous part of the granite spectrum. They have been recognized by the geological community only relatively recently (first definition of A-type granites by Loiselle and Wones in 1979) and they are characterized by several attributes that clearly set them apart from other granitic rocks. A-type granites were originally defined as relatively dry (anhydrous), and they have high contents of alkali metals (either sodium or potassium) and most high field strength trace elements. They commonly have been emplaced in an extensional tectonic regime not directly related to lithospheric convergence (i.e., they have been considered “anorogenic” or “post-tectonic”). In terms of age, the A-type granites span almost three billion years (~2.7 Ga to Recent) of Earth’s history. Known occurrences of early Paleoproterozoic (2.5-2.0 Ga) A-type granites are relatively few and they are dwarfed by the voluminous mid-Proterozoic (1.7-1.0 Ga) A-type associations of Laurentia, Baltica, and Amazonia. 2.5-2.0 Ga A-type granite suites have been described from the North China craton (2.44, 2.16, 2.09 Ga), northwestern China (2.41, 2.34 Ga), central India (2.50, 2.18 Ga), the West Africa craton (2.07 Ga), the Congo craton (2.3 Ga), South Africa (2.05 Ga), the Karelian craton (2.44, 2.43 Ga), and Labrador (2.05 Ga). Three principal lithologic associations can be recognized for these A-type granite suites: (1) A-type granites in South Africa and Karelia represent the felsic component of layered mafic intrusions and may be very extensive (e.g., the ~30,000 km2 Bushveld granites); (2) high-K granites and syenites emplaced in late/post-orogenic or rift-associated settings (China, India, western and central Africa); and (3) a rare example of pre-2.0 Ga anorthosite-mangerite-charnockite-granite (AMCG) suite in Labrador. A common (yet not ubiquitous) feature of these rock associations is their bimodality with mafic magmatism temporally and spatially associated with the granites. The A-type granites typically contain a major crustal source component, which underlines the significance of crustal melting in the petrogenesis of these rocks. The observation that 2.5-2.0 Ga old A-type granite suites are scarce suggests that, during this period of time, conditions for extensive crustal reorganization were not attained on a global scale. Overall, the early Paleoproterozoic has been considered a time of little net crustal growth on Earth and shortage of “juvenile” crust of this age (e.g., Condie et al. 2005). Thus, in early Paleoproterozoic, there probably was a lack of fertile crustal domains that could have provided the crustal source component for A-type granite associations in regions affected by subcontinental thermal perturbations.

Ramo, O. T.

2010-12-01

152

Geology, geochemistry, and geochronology of an A-type granite in the Mulock Glacier area, southern Victoria Land, Antarctica  

International Nuclear Information System (INIS)

On the north side of the Mulock Glacier and at Cape Teall in southern Victoria Land, Antarctica, deformed greenschist facies Skelton Group metasediments are intruded by the post-kinematic A-type Mulock Granite. Geochemical data indicate that this intrusive complex is similar to A-type granitoids previously described both to the north (Glee Intrusives and Penny Hill Granite), where they form part of the Koettlitz Glacier Alkaline Province, and to the south (Foggydog Granite Suite). A U-Pb zircon date of 546 ± 3 Ma on the Mulock Granite places a minimum constraint on the age, and timing of deformation of the Skelton Group rocks in this area, and indicates that the Mulock Granite was emplaced during the initial stages of the Ross Orogeny. This age also confirms that crystallisation of this granite body was synchronous with that of A-type granitoids from the Royal Society Range to Skelton Glacier area immediately to the north. (author). 60 refs., 7 figs., 2 tabs

153

Geochemistry and petrography of U-Th-Y mineralisation in alkali feldspar granite (alaskite) dykes around Dhanota, Mahendragarh district, Haryana, India  

International Nuclear Information System (INIS)

Radioactive alkali feldspar granite (alaskite) occurs as dykes within the Proterozoic granite gneiss around Dhanota. Samples have assayed 0.011 to 0.16% U3O8 and 0.005 to 0.16% ThO2. Yttrium values range from 250 to 800 ppm. Uranothorite occurs in association with zircon, xenotime, magnetite, hematite, sphene and goethite. The U-Th-Y mineralization in alaskites of Dhanota is disseminated syn-magmatic intrusive type. (author)

154

Intrusion Detection in Manet  

Directory of Open Access Journals (Sweden)

Full Text Available TNow days mobile ad hoc networks (MANETs have become a very important research topic as no of mobile users are incremented day by day. MANET will provide communications in the network without any of a fixed infrastructure so it can be used for many applications such as rescue operations, tactical operations, environmental monitoring, conferences, also. But the flexibility in such environment have the challenged of risk of security. Our system supports mainly two parts. 1. To detect intruder attacks in mobile ad hoc network (MANET. 2. To detect the type of attack in mobile ad hoc network (MANET and apply local intrusion detection or network intrusion detection for the attack. It will work for both anomaly detection and misuse detection mechanism. By the Observation of the attack signatures, we find that there are some attack signatures dependent on other previous attack signatures. This is due to the new attack is a derivative from the previous attack. To apply the intrusion detection technique this paper introduces a priory known approach known as acknowledgement based approach which is used to detect intrusion in mobile ad hoc network (MANET and uses intrusion detection technique like matching algorithm. It approaches a technique of developing a network safety by describing network behaviour structure that point out offensive use of the network and also look for the occurrence of those patterns while such an approach may be accomplished of detecting different types of known intrusive actions, it would allow new or undocumented types of attacks to go invisible. As a result, this leads to a system which monitors and learns normal network behavior and then detects deviations from the normal network behaviour.

MRS. MUGDHA KIRKIRE

2013-04-01

155

Mineralogy and geochemistry of the Paleoproterozoic, tin-mineralized Bom Jardim granite of the Velho Guilherme Suite, eastern Amazonian craton  

Science.gov (United States)

The Bom Jardim granite is located to the south of São Felix do Xingu town and is intrusive in the intermediate to felsic volcanic rocks of the Uatumã Group. It is formed dominantly of coarse- to medium-grained isotropic monzogranite and syenogranite, both affected by intense late- to post-magmatic alteration. Biotite, generally chloritized, is the main primary mafic phase, with rare amphibole being found in the monzogranite. Hydrothermally altered and greisenized rocks, containing small primary concentrations of cassiterite + wolframite, as well as quartz veins with millimeter- to centimeter-sized crystals of wolframite + pyrite + fluorite occur in pervasively altered cupolas. Presently, alluvial cassiterite and wolframite (±columbite, tantalite) are mined in the Pedra Preta mine, located in the northern part of the pluton. SEM data showed that Sn-W mineralization is dominantly associated with syenogranite and greisenized rocks. EDS Semi-quantitative analysis revealed that the zircon crystals of the Bom Jardim granite are characteristically enriched in Hf, Y, U, and Th and display Zr/Hf ratios decreasing from monzogranite/leucomonzogranite toward syenogranite and greisenized syenogranite rocks, suggesting that magmatic differentiation significantly contributed for this particular feature. The Bom Jardim granite is slightly peraluminous and displays geochemical affinities with A-type granites. The Bom Jardim granite varieties evolved dominantly by fractional crystallization and their REE patterns are similar to those of the tin-specialized granites of the Velho Guilherme suite. It is concluded that the more evolved granites and associated greisenized rocks of the Bom Jardim pluton are tin-specialized granites. The similarities observed between the granites of the Velho Guilherme suite and the Bom Jardim granite allow to include the latter in this important granite suite.

Lamarão, Claudio Nery; Cordovil Pinho, Sabrina Cristina; de Paiva, Antonio Lima; Galarza, Marco Antônio

2012-10-01

156

Adaptive intrusion data system  

International Nuclear Information System (INIS)

An Adaptive Intrusion Data System (AIDS) was developed to collect data from intrusion alarm sensors as part of an evaluation system to improve sensor performance. AIDS is a unique digital data compression, storage, and formatting system. It also incorporates capability for video selection and recording for assessment of the sensors monitored by the system. The system is software reprogrammable to numerous configurations that may be utilized for the collection of environmental, bi-level, analog and video data. The output of the system is digital tapes formatted for direct data reduction on a CDC 6400 computer, and video tapes containing timed tagged information that can be correlated with the digital data

157

Labile uranium in granitic rocks  

International Nuclear Information System (INIS)

Labile uranium in granitic rocks has been proposed as the source for many ore deposits. Tests of this hypothesis or development of commercial in-situ leaching of uranium from crystalline rocks will require analytical techniques that can be used to identify granites that contain labile uranium. U-Th-Pb isotopic systematics can be used to obtain quantitative or semi-quantitative data on the timing and extent of uranium mobilization, but the technique is limited to Precambrian rocks and is too expensive for general use as an exploration tool. Granite from the Granite Mountains, Wyoming, has been shown to contain labile uranium, and it is proposed that several characteristics of this granite may be typical of other granites that are possible uranium source rocks. Important characteristics for uranium source rocks are inferred to be (1) alkalic affinity and high (>70%) silica content, (2) high Th content, and (3) disequilibria between pairs of long-lived radiogenic daughter products within the 238U-decay chain. This last characteristic may possibly be identified by comparing RaeqU values (radium equivalent uranium obtained by ?-ray spectrometry) with chemical uranium contents. (author)

158

Potassium - argon age data from the Bundelkhand granite and associated rocks and their comparison with the rubidium - strontium isochron ages  

International Nuclear Information System (INIS)

Bundelkhand granitic complex occupies a semi-circular area (north of C.I.S.) of about 25000 sq.km. K-Ar age data on hornblende and biotite from amphibolite and mica schist enclaves in Bundelkhand Granitic Complex from widely separated areas (Aver.c. 2413 Ma) are correlatable with the Rb-Sr (WR) mineral isochron age (c.2402 Av.) of granodiorites and granite, suite II indicating the absence of later thermal events (300 degC, biotite blocking temperature) after the granite (II) emplacement (Rb-Sr data). These K-Ar mineral ages indicate the thermal episodes due to the emplacement of the granite. The younger mineral age (2187 Ma Av) may be correlated with the thermal episodes related to the emplacement of Suite III granite (2130 Ma). Bundelkhand Granitic Complex may broadly be correlated with the lower proterozoic (I) granites of Closepet, Chitradurga, Hyderabad, Karimnagar, (South India), Malanjkhand and Dongargarh covering large areas in Madhya Pradesh, Central India and South India. Thus K-Ar ages may be reliable in case the blocking temperatures of minerals dated keep the 40Ar in the lattice in tact since emplacement. (author). 27 refs., 1 tab., 1 fig

159

Feasibility study of the Conway Granite as a geothermal energy resource  

Energy Technology Data Exchange (ETDEWEB)

The eastern part of the White Mountain batholith is dominated by four intrusive complexes, which contain similar sequences of intrusive rocks. Although the details of the sequence of intrusion differ from complex to complex, the Osceola Granite is generally an early phase, followed by the development of ring dikes of Albany Porphyritic Quartz Syenite and finally the intrusion of Conway Granite. One intrusive complex contains riebeckite granite as a late phase, and at least two complexes fed volcanic eruptions, some of the products of which are preserved in subsided blocks. A specialized study of the orientation of joints was made in the eastern halo of the batholith. Measurement of gravity over the eastern part of the batholith and reduction of these data allows gravity residuals to be calculated and two- and three-dimensional models for the eastern part of the batholith to be constructed. The gravity models are consistent with steeply dipping contacts with the country rocks, and the maximum depth of the eastern part of the batholith is between 4 km and 5.25 km. The temperature distribution within the eastern part of the batholith can be determined using existing parameters for heat flow, heat production, and conductivity augmented by new data for heat production. The geologic boundaries and the gravity model provide the geometric constraints for the temperature distribution. Both one- and two-dimensional models are developed. The temperature distribution varies both vertically and laterally within the batholith. Estimates of temperature beneath the batholith are 170/sup 0/C at 6 km and 220/sup 0/C at 8 km.

Osberg, P.H.; Wetterauer, R.; Rivers, M.; Bothner, W.A.; Creasy, J.W.

1978-08-15

160

Release of uranium through cataclastic deformation of Mansehra granite gneiss and its precipitation in the overlying intramontane basin in northern Pakistan  

International Nuclear Information System (INIS)

The Mansehra pluton belongs to a discontinuous belt of two mica granites of the Lesser Himalayas. The Mansehra granite is generally foliated except in the area around Mansehra. Several phases of granitic activity have been reported from the Mansehra Complex. Shams and Rahman have demonstrated that the younger phases tend to be enriched in Na2O. Ashraf extensively studied minor bodies ranging from albitites through aplites to pegmatites and suggested a late stage albitization event. The northern edge of this sheet-like granitic mass has undergone extensive cataclastic deformation, resulting in the formation of shear zones, mylonites and cataclasites. A chemical comparison of crushed granite with granite outside the shear zone suggests little chemical reconstitution in terms of major elements during cataclastic deformation. A huge shear zone in albitized granite gneiss has yielded secondary uranium minerals at water seepages, suggesting a liberation of uranium. Hydrogeochemical surveys of the crushed granite and adjoining areas suggest that uranium from crushed granite was easily leachable in comparison with rocks outside the shear zone. The uranium thus liberated was trapped in a Pleistocene sequence of clays and unsorted fluviatile sand overlying the granite and country rock metamorphics. (author). 17 refs, 2 figs, 2 tabs

161

Cretaceous evolution of the Adria-Europe plate boundary: succession of events recorded in granites and enclaves of the Moslava?ka Gora (Croatia)  

Science.gov (United States)

Complex Cretaceous S-type granitoid pluton, geotectonically related to an active continental margin, makes a central part of the Moslava?ka Gora (MG) crystalline and hosts two groups of enclaves. Cognate enclaves, genetically related to the granitoid host rocks, comprise different types of microgranular enclaves, tourmaline nodules, K-feldspar megacrysts and other inhomogenities found inside the two-mica granitoids. All of these enclaves provide evidence of the petrogenetic processes that took place inside the MG Cretaceous magmatic system. On the other hand, foreign enclaves, mostly xenoliths of metapelitic and metabasic rocks, hold information about the metamorphic events that preceded or were contemporaneous with the intrusion and solidification of the igneous body. Based on the age data gathered by earlier researchers of the MG crystalline and P-T data extracted from the study of Cretacoeus granitoids and their enclaves, it was possible to characterize multiple episodes of Cretaceous igneous and metamorphic evolution of the MG. Intrusion of the mantle-related mafic magma at pressures ~8 kbar and temperatures ~920 °C has been regarded as the oldest Cretaceous magmatic pulse (~110-90 Ma) recorded in the MG crystalline complex, leaving behind local occurrences of gabbroic rocks. Its relation to the medium-pressure metamorphic event recorded in amphibole-bearing xenoliths reaching ~8 kbar and max. ~800 °C has not been elucidated so far. It was followed by a younger LP-HT event (100-90 Ma), recorded in a sequence of partial melting reactions in the metapelitic rocks reaching granulite facies conditions (2-5 kbar, ~720-790 °C). Such melt-producing reactions documented in the km-sized metapelitic xenoliths point to the nature and extent of processes in the metapelitic source rocks that contributed to the overall production of the granitic magma in this setting. All of the aforementioned events preceded the Late Cretaceous intrusion of the central granitoid body and oscillations of igneous activity recored in the products of mixing and hybridization between granitoids and more mafic magmas (MME enclaves) and the onset of immiscibility (tourmaline nodules) nad the intrusion of leucogranites. According to our data, all of these pulses occurred in a low-pressure crustal setting (<3 kbar, 660-770 °C). Late Cretaceous peak of igneous activity in the MG system was accompanied by a second LP-HT metamorphic event (<2 kbar, <650 °C) that has been recorded in all MG crystalline lithologies and is correlated with the crystallization and cooling of the crystalline complex, following the intrusion of the central granitoid body. Fluids released by its crystallization led to fluid-assisted melting reactions in cm- to m-sized metapelitic enclaves, recording the interaction of granitoid host with the encapsulated fragments of metapelitic rocks and their role in the granite petrogenesis at Moslava?ka Gora. Data gathered by the study of different types of enclaves from the Moslava?ka Gora granitoid rocks are mutually consistent and reflect the complexity of Cretaceous evolution of a small and geotectonically still enigmatic crystalline fragment at the Adria-Europe plate boundary. This approach opens new perspectives for future research of the processes that took place in the mobile zone on the southeastern margins of Mesozoic Europe.

Petrinec, Zorica; Balen, Dražen

2014-05-01

162

Petrochemical characteristics of Serra do Meio alkaline granite (Campo Alegre de Lourdes - Bahia State)  

International Nuclear Information System (INIS)

The Serra do Meio granite outcrops near the town of Campo Alegre de Lourdes, north-northeast of Bahia State. The granite is intrusive into micachists, which are correlatives of the Salgueiro-Cachoeirinha Group (Early Proterozoic), during early to the syn-tectonic shear phase. The geological setting also comprises a phosphatic rock-bearing carbonatitic complex and gabbroid complexes with one of the main world resources of Fe-Ti-V. The granite mineralogical composition grades from Aegerine-augite alkali-feldspar granite/syenites to Leuco alcali-feldspar granite. The geochemical analysis shows SiO2-enrichment (67 to 76%), in alkalis (Na2+K2O, 7,5 to 12,5%), Nb (up to 680ppm), Zr (up to 2,390ppm), Y (up to 250ppm) e REE (up to 796ppm). The geochemical behaviour is peculiar to alkaline series, denoting a silica-oversaturated, potassium-rich, magma. The chondrite-normalized REE patterns display a first group with smooth slopes from the La to Lu, and a second one with negative slopes. Negative Eu anomalies are displayed in all the patterns. The first group is HREE-enriched, with low fractionation ratios. Samples with milonytic fabrics and higher fractionation ratios are related to the second group, suggesting the interaction of metassomatic fluids and the alkaline magma. Discriminant diagrams for Nb, Y and Rb, coupled with geophysical data, point to an intrusive granite in an extensional within a plate tectonic setting of attenuated continental crust. (author)

163

The Rb-Sr age of the Sundsta granite in the Western Pregothian tectonic mega-unit, south-western Sweden  

International Nuclear Information System (INIS)

The Sundsta granite is a reddish, acidic granite, situated in the Western Pregothian mega-unit in Vaermland, south-western Sweden. Its Rb-Sr whole-rock age is 1566+-39 Ma with an initial ratio 0f 0.705 +-0.003. The region is dominated by grey, migmatized granitoids presumably belonging to the Aamaal-I group which has ages of 1650-1700 Ma. The marked difference in degree of migmatization between these two rock-units may indicate that the intrusion of the Sundsta granite post-dates the main migmatization phase of the Aamaal-I granitoid in this region. (Authors)

164

Archaean greenstone belts and associated granitic rocks - A review  

Science.gov (United States)

Archaean greenstone belts and associated granitic rocks comprise some of the most diverse rock types on the Earth's surface and were formed during the early stages of the development of the planet from Eoarchaean to Neoarchaean times - a period extending back from about 4000 to 2500 million years ago. Because of their great age, these rocks have received unprecedented attention from a wide spectrum of Earth scientists striving to learn more about the evolution of the Earth, including its crust, hydrosphere, atmosphere, the commencement of life, and the nature and distribution of mineral deposits. The knowledge gained thus far has accumulated incrementally, beginning with solid field-based studies, the latter being supplemented with increasingly advanced technological developments that have enabled scientists to probe fundamental questions of Earth history. Archaean granite-greenstone terranes display considerable variability of lithologies and geotectonic events, yet there are unifying characteristics that distinguish them from other geological environments. Most greenstone belts consist of a wide variety of volcanic and sedimentary rocks that reflect different evolutionary conditions of formation and all have invariably been influenced by subsequent geotectonic factors, including the intrusion of ultramafic, mafic and granitic complexes, resulting in widespread deformation, metamorphism, metasomatism, as well as mineralization. Geochemical and isotopic age determinations have shown how complex these ancient rocks are and efforts at understanding the nature and evolution of the hydrosphere, atmosphere and primitive life have made Archaean terranes exciting environments in which to study. Conflicting views as to the nature, history and origin of many of the rock types and events in Archaean terranes has been ongoing and stimulating. This review attempts to describe the main lithotypes and other characteristics of granite-greenstone belt geology and points to some areas where contrasting views have been expressed.

Anhaeusser, Carl R.

2014-12-01

165

Petrogenesis and magmatic evolution of ?130 Ma A-type granites in Southeast China  

Science.gov (United States)

A number of Late Mesozoic (?130 Ma) A-type granitic plutons have been identified in Southeast China. Here we investigate the petrogenesis of one of these granitic plutons in Southeast China, the Sanqingshan-Damaoshan (SD) granites in northeastern Jiangxi Province, using zircon U-Pb geochronology, Hf isotopic analyses, and major and trace element analyses. The SD granites are metaluminous to weakly peraluminous and show typical A-type affinity, which is characterized by high SiO2, Na2O + K2O, rare earth element (REE), high field strength element (HFSE) contents, Ga/Al and Fe# [FeOt/(FeOt + MgO)] values. Zircon grains from the SD granites and some other ?130 Ma A-type granites commonly contain oscillatory zoning 'cores' surrounded by unzoned to weakly zoned 'rims'. Detailed studies of zircons from the SD granites show that 'rims' are enriched in LREE, Th and U compared with 'cores'. Chondrite-normalized REE patterns of the 'cores' increase steeply from La to Lu and show pronounced Ce and Eu anomalies, while REE patterns of the 'rims' display higher REE abundances with flatter LREE patterns and moderate Ce anomalies. Nevertheless, Lu-Hf isotopic analyses and Ti-in zircon thermometer show similar characteristics between 'rims' and 'cores', indicating that the 'rims' may crystallize under the effect of internal magmatic hydrothermal fluids. U-rich 'rims' are more susceptible to Pb loss caused by self-irradiation, which may lead to significant younger U-Pb ages. As a result, U-Pb ages of zircon 'cores' (?130 Ma) represent crystallization ages of the SD granites. ?Hf(t) values of zircon grains from the SD granites are between -6.4 and -0.4 with Mesoproterozoic model ages (T2DM) ranging from 1.22 to 1.59 Ga, suggesting that the granites may be formed by partial melting of Proterozoic basement. Compared with other adjacent ?130 Ma A-type granitic plutons in SE China, the SD granites have similar geochemical characteristics and Hf isotopic compositions to those of Xiangshan, Daqiaowu, Yangmeiwan, and Tongshan granites, but different from the Baijuhuajian granite. ?Hf(t) values of the Baijuhuajian granites are higher than other granites, indicating significant participation of juvenile materials. These ?130 Ma A-type granites indicate a back-arc extension setting due to the roll-back of paleo-Pacific plate, where the crust and lithospheric mantle became progressively thinned. The upwelling of asthenosphere triggered the partial melting of crustal rocks and generated the Sanqingshan-Damaoshan, Tongshan, Daqiaowu and Yangmeiwan granitic plutons. With ongoing back-arc extension and increased subduction angle during the roll-back of subducted paleo-Pacific slab, the back-arc extension gradually intensified, resulting in significant additions of mantle juvenile materials to the crustal magma and the formation of the Baijuhuajian granite.

Sun, Fajun; Xu, Xisheng; Zou, Haibo; Xia, Yan

2015-02-01

166

Geochemistry of biotite granites from the Lamas de Olo Pluton, northern Portugal  

Science.gov (United States)

In the Central Iberian Zone (CIZ) extensive crustal recycling occurred during the post-thickening extension stage of the Variscan orogeny (~330-290 Ma). After the ductile deformation phase D3 (~320-300 Ma), characterized by the intrusion of large volumes of highly peraluminous granitic magmas, rapid and drastic tectonic changes at about 300 Ma gave rise to the brittle phase of deformation D4 that controlled the emplacement of Fe-K subalkaline granites (296-290 Ma; Dias et al. 1998). The Lamas de Olo Pluton (LOP) is controlled by NE-SW and NW-SE fracture systems, probably related to the Régua-Verin fault zone (Pereira, 1989). The LOP is a medium to coarse-grained, porphyritic biotite granite, accompanied by medium- to fine grained, porphyritic biotite granite (Alto dos Cabeços- AC) and a more leucocratic, fine-grained, slightly porphyritic biotite-muscovite granite (Barragens- BA). The contacts between LO and AC are generally diffuse, whereas those to BA are sharp. In fact, the BA granite can occur in dykes and sills cutting LO and AC. Microgranular enclaves and xenoliths are very rare. The LOP intrudes the Douro Group, presumably of Precambrian to Cambrian age, and two-mica granites from the Vila Real composite massif. The LOP granites consist of quartz, microcline, plagioclase, biotite, zircon, titanite, tourmaline apatite, fluorite, ilmenite, magnetite, and rutile, with muscovite in BA granite and rare allanite in the LO and AC granites. The plagioclase composition is of oligoclase (An12) - andesine (An35) for LO granite, albite (An9) - andesine (An30) for CA granite and albite (An5) - oligoclase (An20) for BA granite. There are decreases in: a) anorthite content from phenocryst to matrix plagioclase; b) Ba content from phenocryst to matrix microcline in all granites. The Fe2+ biotite has a composition similar to that of biotite from calc-alkaline to sub-alkaline rock series. The LO and AC granites are meta- to peraluminous with ASI variable between 1.05 and 1.21, and display isotopic signatures of (87Sr/86Sr)i = 0.7044-0.7077 and Nd = -2.2 to -1.1. Six samples of LO define a whole rock isochron age of 285±15 Ma with (87Sr/86Sr)i = 0.7051±0.001 (MSWD = 0.11). Two monazite analyses for the LO granite yield an weighted average 207Pb/235U age of 297.19±0.73 Ma, consistent with the preliminary ID-TIMS U-Pb analyses of two transparent and euhedral prisms of zircon that define a concordia age of 296.37 ±0.52 Ma (MSWD = 0.66). The linear trends of major and trace elements variation diagrams of LO and AC granites and their similar mean values of (87Sr/86Sr)i point, at this stage, to an involvement of mid-crustal sources, probably mixed with asthenospheric material. Therefore, LOP consists of post-D3 biotite granites installed in higher structural crustal levels, testifying the occurrence of a crustal growth episode after the major recycling processes that occurred during the deformation phase D3. We thank Prof. J.F. Santos and Dr. S. Ribeiro and Petrochron project (PTDC/CTE-GIX/112561/2009) for the Rb-Sr isotopic data obtained at LGI of University of Aveiro, Portugal. Dias, G. et al. 1998. Lithos, 45, 349-369. Pereira, E., 1989. Serviços Geológicos de Portugal.

Fernandes, Susana; Gomes, Maria; Teixeira, Rui; Corfu, Fernando

2013-04-01

167

Experimental and geochemical evidence for derivation of the El Capitan Granite, California, by partial melting of hydrous gabbroic lower crust  

Science.gov (United States)

Partial melting of mafic intrusions recently emplaced into the lower crust can produce voluminous silicic magmas with isotopic ratios similar to their mafic sources. Low-temperature (825 and 850°C) partial melts synthesized at 700 MPa in biotite-hornblende gabbros from the central Sierra Nevada batholith (Sisson et al. in Contrib Mineral Petrol 148:635 661, 2005) have major-element and modeled trace-element (REE, Rb, Ba, Sr, Th, U) compositions matching those of the Cretaceous El Capitan Granite, a prominent granite and silicic granodiorite pluton in the central part of the Sierra Nevada batholith (Yosemite, CA, USA) locally mingled with coeval, isotopically similar quartz diorite through gabbro intrusions (Ratajeski et al. in Geol Soc Am Bull 113:1486 1502, 2001). These results are evidence that the El Capitan Granite, and perhaps similar intrusions in the Sierra Nevada batholith with lithospheric-mantle-like isotopic values, were extracted from LILE-enriched, hydrous (hornblende-bearing) gabbroic rocks in the Sierran lower crust. Granitic partial melts derived by this process may also be silicic end members for mixing events leading to large-volume intermediate composition Sierran plutons such as the Cretaceous Lamarck Granodiorite. Voluminous gabbroic residues of partial melting may be lost to the mantle by their conversion to garnet-pyroxene assemblages during batholithic magmatic crustal thickening.

Ratajeski, Kent; Sisson, Thomas W.; Glazner, Allen F.

2005-08-01

168

New methodical developments for GRANIT; Nouveaux developpements methodologiques pour GRANIT  

Energy Technology Data Exchange (ETDEWEB)

New methodical developments for the GRANIT spectrometer address further improvements of the critical parameters of this experimental installation, as well as its applications to new fields of research. Keeping in mind an extremely small fraction of ultra cold neutrons (UCN) that could be bound in gravitational quantum states, we look for methods to increase statistics due to: developing UCN sources with maximum phase-space density, counting simultaneously a large fraction of neutrons using position-sensitive detectors, and decreasing detector backgrounds. Also we explore an eventual application of the GRANIT spectrometer beyond the scope of its initial goals, for instance, for reflectometry with UCN. (authors)

Baessler, S. [University of Virginia, Charlottesville, VA-22904 (United States); Oak Ridge Nat. Lab., Oak Ridge, TN-37831 (United States); Gagarski, A.M.; Toperverg, B.P. [PNPI, Orlova Roscha, Gatchina, RU-188300 (Russian Federation); Lychagin, E.V.; Muzychka, A.Y.; Strelkov, A.V. [JINR, 6 Joliot-Curie, Dubna, RU-141980 (Russian Federation); Mietke, A. [Faculty of Science, Department of Phys., Technical University, Dresden, G-01062 (Germany); Nesvizhevsky, V.V. [ILL, 6 rue Jules Horowitz, Grenoble, F-38042 (France); Pignol, G. [LPSC/IN2P3-UJF-INPG, 53 rue des Martyrs, Grenoble, F-38026 (France); Toperverg, B.P.; Zhernenkov, K. [Ruhr Univ. Bochum, 150 Universitatstrasse, Bochum, G-44780 (Germany)

2010-10-15

169

Patherns in the rare earth elements of the Serra do Carambei granite (Parana) and the others associated ignous rocks  

International Nuclear Information System (INIS)

The rare earth elements (REE) distribution patters in igneous rocks of the Serra do Carambei Granite area (Parana) were a very important tool to elucidate the genetic processes and the cogenetic relationships between these rocks. The porphyroid facies of the Cunhaporanga Granitoid Complex has a REE distribution pattern characterized by decreasing concentrations in direction to the heavy rare earth elements (HREE) and the smooth Eu negative anomalie, compatible with amphibole fractionation during the magma ascent and the incipient plagioclase fractionation. The REE pattern of the Serra do Carambei Granite is characterized by the strong Eu negative anomalie, by the light rare earth element (LREE) depletion and by the HREE increase. This shape of the REE patterns is frequently observed in Sn-W granites, according to French authors. However in the igneous rocks of the Serra do Carambei Granite area this is not true. ''Rhyolite'' dytes intrusives in the Serra do Carambei Granite exhibit REE pattern similar to the wall rock, indicating then the same genetic processes. The Castro Group rhyolites have REE patterns with decreasing concentrations in direction to the HREE and smooth Eu negative anomalie. The REE distribution patterns is against the consanguinity between the ''rhyolites'' intruded in the Serra do Carambei Granite and the rhyolites of the Castro Group and also between these rhyolites and the above mentioned Granite. (author)

170

Groundwater evolution of the granite area, Korea  

International Nuclear Information System (INIS)

The geochemistry and environmental isotopes of groundwater in the Cretaceous granite of the Yeongcheon area has been investigated. The hydrochemistry of groundwater belongs to the Ca-HCO3 type. The oxygen-18 and deuterium data are clustered along the meteoric water line, indicating that the groundwater is of meteoric water origin. Tritium data show that the groundwaters were mostly recharged before pre-thermonuclear period and have been mixed with younger surface water flowing rapidly along fractured zones. Based on the mass balance and reaction simulation approaches using both the hydrochemistry of groundwater and the secondary mineralogy of fracture-filling materials, the low-temperature hydrogeochemical evolution of groundwater in the area has been modeled. The results of geochemical simulation show that the concentrations of Ca, Na and HCO3 and pH of waters increase progressively owing to the dissolution of reactive minerals in flow paths. The concentrations of Mg and K first increase with the dissolution of reactant minerals, but later decrease when montmorillonite and illitic material are precipitated respectively. The continuous adding of reactive minerals, i. e. the progressively larger degrees of water/rock interaction, causes the formation of secondary minerals with the following sequence: hematite > gibbsite > kaolinite > montmorillonite > illitic material > microcline. The results of reaction simulation agree well with the observed water chemistry and secondary mineralogy, indicating the successful applicability of this simulation technique to delineate the complex hydrogeochemistry of bedrock groundwaters. (author)

171

Spatial and temporal relationships between granites and porphyry copper deposits in northern Chile  

Science.gov (United States)

Chile is the leading copper producing country in the world, hosting ~30% of known worldwide copper reserves. Subduction-related magmatism in Chile has been ongoing since at least Mesozoic time, with progressive inland migration of the magmatic arc from the Jurassic coast eastward to the active western cordillera in the high Andes. Porphyry copper deposits (PCDs) in Chile are spatially and temporally related to emplacement of shallow, felsic to intermediate composition plutons that sourced the ore-forming magmas and mineralising fluids. However, not every such intrusion in Chile is associated with a mineralised deposit, suggesting that there are other controls on whether or not an intrusion hosts a PCD. Models for porphyry copper formation typically assume emplacement of these felsic to intermediate intrusions at shallow crustal levels (5-15 km depth) [1], but absolute constraints on emplacement depths for both mineralised and barren systems are lacking. In order to explore the relationship between granite emplacement depths and occurrences of PCDs in northern Chile, we have created a geospatial database that compares the age, geochemistry, and depth of mapped felsic to intermediate plutons (e.g. granites, tonalities, and diorites) with the locations of known PCDs, as well as major fault zones and volcanic centres. Emplacement depths have been calculated from published geochemical analyses using existing calibrations of the Al-in-hornblende barometer, which is widely used for calc-alkaline granitic rocks [2]. We are also developing a new experimental calibration of the barometer using a combination of piston cylinder experiments (5, 7, and 10 kbar), externally heated pressure vessel experiments (0.5-2 kbar), and electron microprobe analyses on a granitic sample of the Lluta batholith, collected in northern Chile. This improved Al-in-hornblende barometer, calibrated for shallow intrusions, will provide a viable alternative to estimating depths of PCD formation from fluid inclusions, which is often hampered by alternations between lithostatic and hydrostatic pressure. Furthermore, the results of this study will be broadly applicable to investigating the potential links between intrusion depth, PCD formation, and parameters such as regional tectonic patterns and fluid/melt interactions. References: [1] Sillitoe, 2010, Porphyry Copper Systems, Ec. Geol., 105, 3-41. [2] Anderson et al., 2008, Thermometers and Thermobarometers in Granitic Systems, Rev. Min. Geochem., 69, 121-142.

Jiskoot, Courtney; Mutch, Euan; Cooper, Frances; Tattitch, Brian; Matjuschkin, Vladimir; Blundy, Jon

2014-05-01

172

Interior intrusion alarm systems  

International Nuclear Information System (INIS)

In meeting the requirements for the safeguarding of special nuclear material and the physical protection of licensed facilities, the licensee is required to design a physical security system that will meet minimum performance requirements. An integral part of any physical security system is the interior intrusion alarm system. The purpose of this report is to provide the potential user of an interior intrusion alarm system with information on the various types, components, and performance capabilities available so that he can design and install the optimum alarm system for his particular environment. In addition, maintenance and testing procedures are discussed and recommended which, if followed, will help the user obtain the optimum results from his system

173

WLAN Intrusion Detection System  

Directory of Open Access Journals (Sweden)

Full Text Available This is an implementation of the Wireless LAN Intrusion Detection System (WIDS using clock-skews as a fingerprinting property as suggested by Jana-Kasera [1]. Our objective is to detect the presence of a fake access point (AP in a Wireless LAN (WLAN. Use of clock -skew enables us to effectively detect Medium Access Control (MAC Address spoofing. The principle used in this project is that clock s k e w s remain consistent over time for the same AP but vary significantly across AP’s. We have also tried to exploreprobable points of failure and implemented algorithms to overcome these problems. Advantage of this implementation is that fake AP can be detected very quickly as WLAN Intrusion Detection System needs only 100 -200 packets in most cases.

Ms. Sushama Shirke

2011-08-01

174

Intrusion detection system elements  

International Nuclear Information System (INIS)

This report highlights elements required for an intrusion detection system and discusses problems which can be encountered in attempting to make the elements effective. Topics discussed include: sensors, both for exterior detection and interior detection; alarm assessment systems, with the discussion focused on video assessment; and alarm reporting systems, including alarm communication systems and dislay/console considerations. Guidance on careful planning and design of a new or to-be-improved system is presented

175

New methodical developments for GRANIT  

Energy Technology Data Exchange (ETDEWEB)

New methodical developments for the GRANIT spectrometer address further improvements of the critical parameters of this experimental installation, as well as its applications to new fields of research. Keeping in mind an extremely small fraction of ultra cold neutrons (UCN) that could be bound in gravitational quantum states, we look for methods to increase statistics due to: developing UCN sources with maximum phase-space density, counting simultaneously a large fraction of neutrons using position-sensitive detectors, and decreasing detector backgrounds. Also we explore an eventual application of the GRANIT spectrometer beyond the scope of its initial goals, for instance, for reflectometry with UCN.

Baessler, Stefan [ORNL; Nesvizhevsky, V. [ Inst Max Von Laue Paul Langevin, F-38042 Grenoble 9, France; Toperverg, B [Ruhr University, Bochum, Germany; Zhernenkov, K. [Ruhr University, Bochum, Germany; Gagarski, A [Petersburg Nuclear Physics Institute, Gatchina, Russia; Lychagin, E [Joint Institute for Nuclear Research, Dubna, Russia; Muzychka, A [Joint Institute for Nuclear Research, Dubna, Russia; Strelkov, A [Joint Institute for Nuclear Research, Dubna, Russia; Mietke, A [Technische Universitat Dresden

2011-01-01

176

New methodical developments for GRANIT  

Science.gov (United States)

New methodical developments for the GRANIT spectrometer address further improvements of the critical parameters of this experimental installation, as well as its applications to new fields of research. Keeping in mind an extremely small fraction of ultra cold neutrons (UCN) that could be bound in gravitational quantum states, we look for methods to increase statistics due to: developing UCN sources with maximum phase-space density, counting simultaneously a large fraction of neutrons using position-sensitive detectors, and decreasing detector backgrounds. Also we explore an eventual application of the GRANIT spectrometer beyond the scope of its initial goals, for instance, for reflectometry with UCN.

Baessler, S.; Gagarski, A. M.; Lychagin, E. V.; Mietke, A.; Muzychka, A. Yu.; Nesvizhevsky, V. V.; Pignol, G.; Strelkov, A. V.; Toperverg, B. P.; Zhernenkov, K.

2011-10-01

177

Status of LLNL granite projects  

International Nuclear Information System (INIS)

The status of LLNL Projects dealing with nuclear waste disposal in granitic rocks is reviewed. This review covers work done subsequent to the June 1979 Workshop on Thermomechanical Modeling for a Hardrock Waste Repository and is prepared for the July 1980 Workshop on Thermomechanical-Hydrochemical Modeling for a Hardrock Waste Repository. Topics reviewed include laboratory determination of thermal, mechanical, and transport properties of rocks at conditions simulating a deep geologic repository, and field testing at the Climax granitic stock at the USDOE Nevada Test Site

178

Colorectal cancer in younger population: our experience  

International Nuclear Information System (INIS)

Objective: To promote awareness regarding increased occurrence of colorectal cancer in younger population and its clinicopathological features compared to older patients. Methods: The cross-sectional study was conducted from February 2010 to January 2011 on patients with diagnosis of colorectal carcinoma admitted through emergency or outpatient departments to Surgical Unit 5, Civil Hospital, Karachi. Data regarding age, gender, presentation, site of tumour, surgery performed and Dukes staging was collected and analysed. Results: A total of 23 patients were operated during the study period: 13 (56.52%) males and 10 (43.47%) females. Of them 12 (52.17%) were below the age of 40 years, while 3 (13.04%) patients were in the 11-20 age group. In 7 (30.4%) patients, tumour was irresectable at the time of presentation so a palliative procedure (diversion colostomy or ileostomy) was performed. There was a higher proportion of younger patients with metastatic disease at the time of presentation (n=9; 75%) while 10 out of 12 patients in the younger age group (83.3%) had a tumour of left colon, particularly rectum. Conclusion: Although colorectal cancer is usually a disease of older patients, it is increasingly becoming more common in younger population. Data suggests a leftward distribution for colorectal carcinoma and that younger patients present with more advanced disease and poorer prognosis. (author)

179

Origin of postcollisional intrusions in NW Anatolia, Turkey: Implications for magma chamber processes  

Science.gov (United States)

Post-collisional magmatic activities of NW Anatolia are represented by a series of granitic intrusions and volcanic successions in the Biga Peninsula, NW Turkey. These plutonic rocks have distinct textures, chemical compositions and Sr-Nd isotope characteristics. They consist of coarse grained, equigranular and/or hypidiomorphic textured granite, gronodiorite, monzogranite, quartz-monzonite, pyroxene-monzonite and leucocratic alkali feldspar granites. These intrusions are composed of quartz, K-feldspar, plagioclase, hornblende, pyroxene and biotite. However, leucocratic facies rocks contain tourmaline with minor amount of mafic minerals. Accessory phases are represented by zircon, apatite, monozite, magnetite, sphene and rarely allanite. ASI values of the plutonic rocks vary between 0.7 and 1.24. These intrusive rocks are therefore classified as metaluminous-peraluminous with I-type affinity. K2O contents show that the intrusive rock samples show calc-alkaline, high K-calc-alkaline and shoshonitic character. Initial 87Sr/86Sr(t) (0.69980-0.70835), 143Nd/144Nd(t) (0.51238-0.51247) isotope ratios and negative ?Nd(t) (-4.4 - -2.6) values imply that these intrusive rocks could have been derived from enriched mantle sources. N-MORB normalized spidergrams of NW Anatolian plutonic rocks display enrichments in large ion lithophile elements (LILE), light rare earth elements (LREE) and depletion in high field strength elements (HFSE) indicating hydrous melting of a mantle wedge in a subduction zone and/or enrichment of the mantle source with an inherited subduction component from an ancient arc magmatism. Chondrite-normalized Rare Earth Element spidergrams are indicative of the importance of plagioclase and amphibole fractionation. On tectonic discrimination diagrams, all granite samples fall into the volcanic arc granite, syn and post-collisional granite fields. The geochemical data also indicate that a number of magma chamber processes involving magma mixing, fractional crystallization (FC) and assimilation with fractional crystallization (AFC, EC-AFC) might have been operational during the magma chamber evolution. These stocks were dated by using K/Ar method on hornblende, biotite and whole rock samples and U/Pb LA-ICP-MS zircon dating, yielding ages between 20.2±0,9 Ma and 27.89±0,17 Ma (Upper Oligocene - Lower Miocene). The widespread Upper Oligocene - Lower Miocene plutonism in NW Turkey is thought to be linked to crustal thinning resulted from slab roll-back and syn-convergent extensional regime after the collision between the Sakarya Zone and Anatolide-Tauride platform.

Aysal, Nam?k

2013-04-01

180

MORPHOMETRY OF ZIRCON FROM BETLIAR GRANITE  

OpenAIRE

Morphometrical analyse has been provided, using the method of [10] , on zircon from granite porphyry at Betliar. The result of this investigation indicate a comagmatic origin of Betliar and other granite bodies in the Gemericum. The source materila for at the granite magma formation originated by hybridization of crust-mantle rocks.

Jakabská Katarína

1997-01-01

181

MORPHOMETRY OF ZIRCON FROM BETLIAR GRANITE  

Directory of Open Access Journals (Sweden)

Full Text Available Morphometrical analyse has been provided, using the method of [10] , on zircon from granite porphyry at Betliar. The result of this investigation indicate a comagmatic origin of Betliar and other granite bodies in the Gemericum. The source materila for at the granite magma formation originated by hybridization of crust-mantle rocks.

Jakabská Katarína

1997-10-01

182

Geochronological and geological studies on a granite of higher Himalaya, North-East of Manikaran, Himachal Pradesh  

International Nuclear Information System (INIS)

Rb-Sr whole-rock data is presented for a biotite-granite of Central Crystallines. The whole-rock isochron age is found to be 467 +- 45 m.y. This should represent the time of intrusion of the granite. A brief account of the geology and petrography is also presented. The age of the biotite is found to be 8.8 +- 2.0 m.y., which is the youngest Rb-Sr age reported so far for a mineral from the Himalaya. This fixes the period when the rocks of this area, after being heated and uplifted, cooled to a temperature of about 3000C. (author)

183

Charnockites and granites of the western Adirondacks, New York, USA: a differentiated A-type suite  

Science.gov (United States)

Granitic rocks in the west-central Adirondack Highlands of New York State include both relatively homogeneous charnockitic and hornblende granitic gneisses (CG), that occur in thick stratiform bodies and elliptical domes, and heterogeneous leucogneisses (LG), that commonly are interlayered with metasedimentary rocks. Major- and trace-element geochemical analyses were obtained for 115 samples, including both types of granitoids. Data for CG fail to show the presence of more than one distinct group based on composition. Most of the variance within the CG sample population is consistent with magmatic differentiation combined with incomplete separation of early crystals of alkali feldspar, plagioclase, and pyroxenes or amphibole from the residual liquid. Ti, Fe, Mg, Ca, P, Sr, Ba, and Zr decrease with increasing silica, while Rb and K increase. Within CG, the distinction between charnockitic (orthopyroxene-bearing) and granitic gneisses is correlated with bulk chemistry. The charnockites are consistently more mafic than the hornblende granitic gneisses, although forming a continuum with them. The leucogneisses, while generally more felsic than the charnockites and granitic gneisses, are otherwise geochemically similar to them. The data are consistent with the LG suite being an evolved extrusive equivalent of the intrusive CG suite. Both CG and LG suites are metaluminous to mildly peraluminous and display an A-type geochemical signature, enriched in Fe, K, Ce, Y, Nb, Zr, and Ga and depleted in Ca, Mg, and Sr relative to I- and S-type granites. Rare earth element patterns show moderate LREE enrichment and a negative Eu anomaly throughout the suite. The geochemical data suggest an origin by partial melting of biotite- and plagioclase-rich crustal rocks. Emplacement occurred in an anorogenic or post-collisional tectonic setting, probably at relatively shallow depths. Deformation and granulite-facies metamorphism with some partial melting followed during the Ottawan phase of the Grenville Orogeny, yielding the present migmatitic granitic and charnockitic gneisses. ?? 1992.

Whitney, P.R.

1992-01-01

184

Naturally occurring radionuclides in Malaysian granites  

International Nuclear Information System (INIS)

The concentration of radium, a naturally occurring radionuclide, in Malaysian granite was analysed using a hyper-pure germanium gamma spectrometer. The results show that Cretaceous granites from southern part of Peninsula has lower radium concentration compared to Triassic granites from the Western Belt of Peninsular Malaysia. The mean concentrations of Ra-226 and Ra-228 in peninsular granites are 0.20 Bq/g and 0.16 Bq/g respectively. Absorbed dose rate from granite was estimated to be 190 nGy/h with a maximum value of 490 nGy/h. (Author)

185

Hybrid network intrusion detection  

Science.gov (United States)

We report on a machine learning classifier that can be used to discover the patterns hidden within large networking data flows. It utilizes an existing intrusion detection system (IDS) as an oracle to learn a faster, less resource intensive normalcy classifier as a front-end to a hybrid network IDS. This system has the capability to recognize new attacks that are similar to known attack signatures. It is also more highly scalable and distributable than the signature-based IDS. The new hybrid design also allows distributed updates and retraining of the normalcy classifier to stay up-to-date with current threats.

Tahmoush, David

2014-05-01

186

Distributed Intrusion Detection System  

Science.gov (United States)

Internet worms and other malicious code often scan firewalls to determine which ports are unprotected. While firewall users have access to their port scanning data in the form of log files, most do not make use of it. The Distributed Intrusion Detection System remotely monitors trends in worldwide port scanning, and the data it has collected is available at this site. The data can be used by Internet professionals for early detection of worms or for implementing improved security measures. Firewall users can contribute to this project by downloading the free DShield Client, which automatically sends log reports for inclusion in worldwide data or by submitting logs online via a Web interface.

187

Geochemical investigations on some of the Infra Cambrian Acid intrusive and volcanic rocks in Iran  

International Nuclear Information System (INIS)

Geochemical investigations on some of the acid intrusive and volcanic rocks of Iran, which are attributed to the Infra cambrian, have been carried out to reveal their possible genetic relationships. These igneous rocks include: Do ran, Shah-Bolaghi, Sarve-Jahan, NE Ardakan - Yazd (Darbastegoon), south Mahabad, Bornavard (Tak nar), Zarigan, Narigan, Chardormaloo granites, Rizo and De zoo micro granites and volcanic rocks, Ga chin rhyolites (Bandar-Abass), and Ghareh-Dash (east of Sae en-De j). These intrusive s, except south Mahabad granodiorite, belong to the class of the alkali feldspathic granite to granitic rocks. Most of these rocks are hololeucocratic and devoid of ferro magnesian minerals. The volcanic rocks are mainly felsic (Rhyolite and Quartz porphyra) associated with vacillation's rocks. These suites of rocks plot on the chemical diagrams in sub alkaline field. Regarding to variations of Na2O, K2O and Ca O contents, they can further be subdivided into sodi c, potas sic, sodi-potas sic and sodi-calci c subgroups. The normalized values (MORB and chondritic) of their trace elements on the spider diagrams overlap each other indicates that some genetic relations ships exist among samples of white Doran Granite, Shahbolaghi, Sarve-Jahan and some Darbastegoon, in one hand, and Taknar, Narigan Granites, Gachin, Rizoo and Dezoo Rhyolites, on the other hand. The overlap also shows that the mentioned igneous bodies have been originated from contious bodies have been originated from continental crust and the samples of each groups, at least belong to a distinct tectonic al regime

188

Network Intrusion Forensic Analysis Using Intrusion Detection System  

Directory of Open Access Journals (Sweden)

Full Text Available The need for computer intrusion forensics arises from the alarming increase in the number of computer crimes that are committed annually. After a computer system has been breached and an intrusion has been detected, there is a need for a computer forensics investigation to follow. Computer forensics is used to bring to justice, those responsible for conducting attacks on computer systems throughout the world. Because of this the law must be follow precisely when conducting a forensics investigation. It is not enough to simple know an attacker is responsible for the crime, the forensics investigation must be carried out in a precise manner that will produce evidence that is amicable in a court room. For computer intrusion forensics many methodologies have been designed to be used when conducting an investigation. With the birth of the Internet and networks, the computer intrusion has never been as significant as it is now. There are different preventive measures available, such as access control and authentication, to attempt to prevent intruders. Intrusion detection systems (IDS are developed to detect an intrusion as it occurs, and to execute countermeasures when detected. Intrusion detection (ID takes over where preventive security fails. In order to choose the best IDS for a given system, one should be aware of the advantages and disadvantages of the each IDS. This paper views a forensic application within the framework of Intrusion Detection and details the advantages and disadvantages of IDS.

Manish Kumar

2011-05-01

189

Geology and geochemistry of the Redrock Granite and anorthosite xenoliths (Proterozoic in the northern Burro Mountains, Grant County, New Mexico, USA  

Directory of Open Access Journals (Sweden)

Full Text Available Mineral ages from the A-type granites and anorthosite xenoliths in the Redrock area in the northwestern Burro Mountains in southwestern New Mexico cluster around ~1220–1225 Ma and provide yet another example of bimodal igneous activity during this time period in the southwestern United States. The metaluminous to peraluminous, marginally alkaline to subalkaline Redrock Granite exhibits the textural, mineralogical, and geochemical features of A-type granitethat was emplaced at a relatively high crustal level. Field relationships, whole rock and mineral geochemical and isotopic trends suggest that the four phases of the Redrock Granite are genetically related, with the miarolitic biotite/alkali feldspar granite being the youngest phase. Spatial relationships and geochemical data suggest that the anorthosite xenoliths were coeval with the RedrockGranite, which is consistent with the anorthosite being derived from the upper mantle, possibly due to deep mantle upwellings, and the Redrock Granite from the lower crust. The process involved melting in the upper mantle, emplacement of anorthosite in the crust resulting in partial crustal melting and thinning, and, finally, intrusion of shallow silicic plutons, the Redrock Granite. The Redrock Granite and anorthosite were presumably derived from sources characterized by subtle, long-term LREE depletion, with ?Nd (at 1220 Ma values on theorder of +1 to +2.

Virginia T. McLemore

2002-01-01

190

Igneous phenocrystic origin of K-feldspar megacrysts in granitic rocks from the Sierra Nevada batholith  

Science.gov (United States)

Study of four K-feldspar megacrystic granitic plutons and related dikes in the Sierra Nevada composite batholith indicates that the megacrysts are phenocrysts that grew in contact with granitic melt. Growth to megacrystic sizes was due to repeated replenishment of the magma bodies by fresh granitic melt that maintained temperatures above the solidus for extended time periods and that provided components necessary for K-feldspar growth. These intrusions cooled 89-83 Ma, are the youngest in the range, and represent the culminating magmatic phase of the Sierra Nevada batholith. They are the granodiorite of Topaz Lake, the Cathedral Peak Granodiorite, the Mono Creek Granite, the Whitney Granodiorite, the Johnson Granite Porphyry, and the Golden Bear Dike. Megacrysts in these igneous bodies attain 4-10 cm in length. All have sawtooth oscillatory zoning marked by varying concentration of BaO ranging generally from 3.5 to 0.5 wt%. Some of the more pronounced zones begin with resorption and channeling of the underlying zone. Layers of mineral inclusions, principally plagioclase, but also biotite, quartz, hornblende, titanite, and accessory minerals, are parallel to the BaO-delineated zones, are sorted by size along the boundaries, and have their long axes preferentially aligned parallel to the boundaries. These features indicate that the K-feldspar megacrysts grew while surrounded by melt, allowing the inclusion minerals to periodically attach themselves to the faces of the growing crystals. The temperature of growth of titanite included within the K-feldspar megacrysts is estimated by use of a Zr-in-titanite geothermometer. Megacryst-hosted titanite grains all yield temperatures typical of felsic magmas, mainly 735-760 ??C. Titanite grains in the granodiorite hosts marginal to the megacrysts range to lower growth temperatures, in some instances into the subsolidus. The limited range and igneous values of growth temperatures for megacryst-hosted titanite grains support the interpretation that the megacrysts formed ag igneous sanidine phenocrysts, that intrusion temperatures varied by only small amounts while the megacrysts grew, and that megacryst growth ceased before the intrusions cooled below the solidus. Individual Ba-enriched zones were apparently formed by repeated surges of new, hotter granitic melt that replenished these large magma chambers. Each recharge of hot magron offset cooling, maintained the partially molten or mushy character of the chamber, stirred up crystals, and induced convective currents that lofted, settling megacrysts back up into the chamber. Because of repeated reheating of the magma chamber and prolonged maintenance of the melt, this process apparently continued long enough to provide the ideal environment for the growth of these extraordinarily large K-feldspar phenocrysts. ??2008 Geological Society of America.

Moore, J.G.; Sisson, T.W.

2008-01-01

191

Localisation of deformation in the thermal contrast at a granite batholith margin, New Zealand  

Science.gov (United States)

The Wainui Shear Zone is a ˜ 1.2 km wide steeply dipping ductile shear zone that is intimately associated with the western margin of a very extensive granite batholith in central New Zealand. Shear sense indicators and lineation orientations within the central high-strain portion of shear zone consistently show a reverse dip-slip east-side-up sense of motion. Shallower foliation in the margins of the shear zone is interpreted to pre-date the central high-strain zone. However, U-Pb and Ar-Ar data reveal that all ductile deformation occurred between ˜114 and 109 Ma (and probably between 114 and 111 Ma) requiring: (1) that deformation kinematics within the shear zone changed over a short time period, and (2) the shear fabrics formed immediately after emplacement of the voluminous granite batholith. The temporal and spatial link between the deformation and plutonism is hypothesised to be a result of thermal weakening of the cooler Paleozoic crust by Cretaceous granite intrusion, which promoted localisation of deformation onto the intrusive contact. Deformation was initially distributed over a wide zone but became focused into a central mylonite zone. Continental-scale shortening is recorded as a network of ductile shear zones that formed on thermal contrasts within the upper, middle and lower crust along the New Zealand Gondwana margin.

Scott, J. M.; Borcovsky, D. A.; Palin, J. M.; Toy, V. G.

2014-07-01

192

Intrusion detection sensor testing tools  

Energy Technology Data Exchange (ETDEWEB)

Intrusion detection sensors must be frequently tested to verify that they are operational, and they must be periodically tested to verify that they are functioning at required performance levels. Concerns involving this testing can include: The significant amount of manpower required, inconsistent results due to variability in methods and personnel, exposure of personnel to hazardous environments, and difficulty in obtaining access to the areas containing some of the intrusion sensors. To address these concerns, the Department of Energy directed Sandia National Labs. to develop intrusion detection sensor testing tools. Over the past two years Sandia has developed several sensor testing tool prototypes. This paper describes the evolution of an exterior intrusion detection sensor tester and automatic data logger, and also describes various interior intrusion detection sensor test fixtures that can be remotely activated to simulate an intruder.

Hayward, D.R.

1994-08-01

193

Origin of a late Neoproterozoic (605 ± 13 Ma) intrusive carbonate-albitite complex in Southern Sinai, Egypt  

Science.gov (United States)

New geochemical, isotopic, and geochronological data and interpretations are presented for late Neoproterozoic intrusive carbonates and related rocks of southern Sinai, Egypt (northernmost Arabian-Nubian Shield). The Tarr carbonates are coarsely crystalline and related to explosive emplacement of hypabyssal and volcanic albitite at 605 ± 13 Ma. The carbonates associated with the albitites are divisible into two types: primary dolomitite and secondary breunneritite (Fe-rich magnesite). The dolomitite was clearly intrusive but differs from classic igneous carbonatites, containing much lower abundances of incompatible elements, such as REE, U, Th, Rb, Nb, Y, P, Sr, Zr, Ba, and total alkalies. The breunneritite is a secondary replacement of dolomitite, probably marking the roots of a vigorous hydrothermal system. Albitites show pristine abundances of major and trace elements and were not subjected to a major metamorphic overprint. They are relatively more fractionated, alkaline and related to within-plate A-type magmas, were emplaced in an extensional or non-compressive tectonic regime in the cupola of high-level A-type granite. Tarr albitites may represent residual magma remaining after near-total crystallization of an A-type granite pluton at depth, forcibly emplaced into the roof above the cooling pluton. The intrusive dolomitite exsolved from highly differentiated albitite melt, in the apical regions of a still-buried alkaline “A-type” granite pluton that was rich in CO2; these volatiles migrated upwards and towards the cooler margins of the magma body. Late NNE-SSW extension allowed a shallow-level cupola to form, into which albitite melts and carbonate fluids migrated, culminating in explosive emplacement of albitite breccia and intrusive carbonate. Isotopic compositions of Tarr dolomitite and albitite indicate these are consanguineous and ultimately of mantle origin. Magmatic volatiles fenitized the wall rock, while submarine hydrothermal activity transformed some of the dolomitite into breunneritite. Recognition of Tarr-type should encourage similar hypabyssal complex intrusions to be sought for in association with A-type granitic plutons elsewhere.

Azer, Mokhles Kamal; Stern, Robert J.; Kimura, Jun-Ichi

2010-03-01

194

A hybrid composite dike suite from the northern Arabian Nubian Shield, southwest Jordan: Implications for magma mixing and partial melting of granite by mafic magma  

Science.gov (United States)

The Arabian Nubian Shield is an exemplary juvenile continental crust of Neoproterozoic age (1000-542 Ma). The post-collisional rift-related stage (~ 610 to 542 Ma) of its formation is characterized among others by the intrusion of several generations of simple and composite dikes. This study documents a suite of hybrid composite dikes and a natural example of partial melting of granite by a mafic magma from the northernmost extremity of Arabian Nubian Shield in southwest Jordan. The petrogenesis of this suite is discussed on the basis of field, petrographic, geochemical, and Rb/Sr isotopic data. These dikes give spectacular examples of the interaction between basaltic magma and the granitic basement. This interaction ranges from brecciation, partial melting of the host alkali feldspar granite to complete assimilation of the granitic material. Field structures range from intrusive breccia (angular partially melted granitic fragments in a mafic groundmass) to the formation of hybrid composite dikes that are up to 14 m in thickness. The rims of these dikes are trachyandesite (latite) with alkali feldspar ovoids (up to 1 cm in diameter); while the central cores are trachydacite to dacite and again with alkali feldspar ovoids and xenoliths from the dike rims. The granitic xenoliths in the intrusive breccia have been subjected to at least 33% partial melting. A seven-point Rb/Sr isochron from one of these composite dikes yields an age of 561 ± 33 Ma and an initial 87Sr/86Sr ratio of 0.70326 ± 0.0003 (2?) and MSWD of 0.62. Geochemical modeling using major, trace, rare earth elements and isotopes suggests the generation of the hybrid composite dike suite through the assimilation of 30% to 60% granitic crustal material by a basaltic magma, while the latter was undergoing fractional crystallization at different levels in the continental crust.

Jarrar, Ghaleb H.; Yaseen, Najel; Theye, Thomas

2013-03-01

195

The use of the Martinamor tourmaline granite in the historic buildings of Salamanca and Alba de Tormes  

OpenAIRE

ABSTRACT: The Martinamor quarries, consisting of tourmaline leucogranites, have been documented as a source material for many post-medieval historical buildings of Salamanca and Alba de Tormes. The granite itself outcrops as a thin, shallowly northward-dipping sheet-like intrusion, belonging to a phase-3 Variscan antiform. Apart from its short distance from the city of Salamanca, several significant criteria can be considered to account for the successful use of the Martinam...

Lo?pez Plaza, M.; Sa?nchez, M. G.; In?igo, A. C.

2010-01-01

196

Electric properties of granitic rocks  

OpenAIRE

The objective of this work is to clarify the role of water content on the charge trans- port mechanisms of different granitic rocks. The mineralogical content of the rocks will also be taken into account. From the electrical point of view these materials are rather insulating porous media where charge injection creates different phenomena like build-up charges, space charge limited currents, surface effects and other behav- iors that resemble much a variety of oxides, like AlO.

Silva, H. G.; Tlemc?ani, M.; Albino, A.; Bezzeghoud, M.; Rosa, R.; Caldeira, B.; Borges, J. F.

2010-01-01

197

Extra-terrestrial igneous granites and related rocks: A review of their occurrence and petrogenesis  

Science.gov (United States)

The telluric planets and the asteroid belt display the same internal structure with a metallic inner core and a silicate outer shell. Experimental data and petrological evidence in silicate systems show that granite can be produced by extreme igneous differentiation through various types of igneous processes. On Moon, 4.4-3.9 Ga granite clasts display dry mineral assemblages. They correspond to at least 8 discrete intrusive events. Large K/Ca enrichment and low REE abundances in granite relative to KREEP are consistent with silicate liquid immiscibility, a process observed in melt inclusions within olivine of lunar basalts and in lunar meteorites. Steep-sided domes identified by remote sensing can represent intrusive or extrusive felsic formations. On Mars, black-and-white rhythmic layers observed on the Tharsis rise along the flanks of the peripheral scarps of the Tharsis Montes giant volcanoes suggest the possible eruption of felsic pyroclastites. Though no true granites were found so far in the Martian SNC meteorites, felsic glasses and mesostases were identified and a component close to terrestrial continental (granitic) crust is inferred from trace element and isotope systematics. Venus has suffered extensive volcanic resurfacing, whereas folded and faulted areas resemble terrestrial continents. Near large shield volcanoes, with dominant basaltic compositions, steep-sided domes have been interpreted as non-degassed silicic extrusions. The hypothesis of a granitic component is "tantalising". Extra-terrestrial granite is frequently found as clasts and mesostases in asteroidal meteorites. Porphyritic textures, with alkali feldspar crystals up to several centimetres in size, were observed in silicate enclaves within iron meteorites. In the chondrite clan, polymict breccias can contain granitic clasts, whose provenance is debated. One clast from the Adzhi-Bogdo meteorite yields a 4.53 ± 0.03 Ga Pb-Pb age, making it the oldest known granite in the solar system. The vast majority of granitic materials recognised so far in the extra-terrestrial record are characterised by ferroan A-type compositions, characterised by high to very high K2O and medium CaO contents, sodic varieties being exceedingly rare. Textural evidence of graphic quartz-alkali feldspar intergrowths within crystallised products suggests that they are igneous in origin and crystallised quickly from a liquid. In water-depleted to water-free environments, fluorine and chlorine can play significant roles, as their effects on liquidus temperatures and crystallising assemblages are nearly identical to those of water. The distribution of alkalis and alkaline earths cannot be related only to extensive crystal fractionation, but is likely induced by supplementary silicate liquid immiscibility. Medium-temperature silicate liquid immiscibility is well known as a mode of differentiation in experimental petrology studies at very low pressures on systems dominated by Fe, Ti, K, and P as major elements. The ultimate question is, therefore, not whether granite (s.l.) occurs in any given planetary body, but if sufficient volumes of granitic materials could have been produced to constitute stable continental nuclei.

Bonin, Bernard

2012-11-01

198

Meltwater routing and the Younger Dryas  

OpenAIRE

The Younger Dryas—the last major cold episode on Earth—is generally considered to have been triggered by a meltwater flood into the North Atlantic. The prevailing hypothesis, proposed by Broecker et al. [1989 Nature 341:318–321] more than two decades ago, suggests that an abrupt rerouting of Lake Agassiz overflow through the Great Lakes and St. Lawrence Valley inhibited deep water formation in the subpolar North Atlantic and weakened the strength of the Atlantic Meridional Overturning C...

Condron, Alan; Winsor, Peter

2012-01-01

199

Natural radionuclide distribution in Brazilian commercial granites  

International Nuclear Information System (INIS)

The dimension stones sector in Brazil produces several varieties of granites, marbles, slates and basalts. More than half of this production corresponds to around 200 different commercial types of granites with specific names, geographical and geological origins and mineral compositions. The well-known natural radioactivity present in rocks, where high radiation levels are associated with igneous rocks such as granite, can be used to determine their general petrologic features. This subject is important in environmental radiological protection, since granites are widely used as building and ornamental stones. In this paper, it is applied to correlate the petrographic characteristics of commercial granites with their corresponding dose rates for natural radioactivity. Amounts of thorium, uranium and potassium concentrations have been reported in several Brazilian commercial granite samples

200

Geochemistry and petrogenesis of the proterozoic granites from Jhabua and Dhar districts, Madhya Pradesh, India and their bearing on uranium mineralisation  

International Nuclear Information System (INIS)

In the western part of Madhya Pradesh a number of small plutonic granites occur as intrusive into the gneisses and Aravalli metasediments. Granites are of grey, pink colour and gneissic varieties. Mineralogically, the granites are two mica bearing. Chemically they are K2O rich, calc-alkaline, metaluminous to peraluminous and differentiated in nature. Tectonically they are volcanic arc types with an affinity to syn-collisional setup. Basement reactivation may be the cause of the emplacement of these granites as the area is traversed by a number of basement lineaments. They are enriched in light REE with Ce/Yb ratio ranging from 1.4 to 8.4. Negative Eu anomaly (Eu/Eu* 0.2 to 0.8) suggests that they are fractionated. High Th/U ratio (1-18) indicates that uranium has been leached out. Hence the overlying infratrappeans hold potential for litho/structural controlled uranium mineralisation.(author)

201

Contrasting zircon morphology and UPb systematics in peralkaline and metaluminous post-orogenic granite complexes of the Arabian Shield, Kingdom of Saudi Arabia  

Science.gov (United States)

Uzircon ages are reported for seven metaluminous-to-peralkaline post-orogenic granites from the Late Proterozoic Arabian Shield of Saudi Arabia. Zircons from the metaluminous rocks are prismatic, with length-to-width ratios of ??? 2-4: 1 and small pyramidal terminations. In contrast, zircons from three of the four peralkaline complexes either lack well-developed prismatic faces (are pseudo-octahedral) or are anhedral. Some zircons from the peralkaline granites contain inherited radiogenic Pb and have very high common Pb contents (206Pb/204Pb Zircons in the metaluminous granites do not contain inheritance and yield well-defined concordia intercepts. The span of ages of the seven complexes (670-470 Ma) indicates that post-orogenic granitic magmatism was not a singular event in the Arabian Shield but rather occurred as multiple intrusive episodes from the Late Proterozoic to the Middle Ordovician. ?? 1989.

Aleinikof, J.N.; Stoeser, D.B.

1989-01-01

202

TOWARD A NEW PARADIGM FOR GRANITE GENERATION  

OpenAIRE

Ideas about granite generation have evolved considerably during the last two decades. The present paper lists what ideas were accepted and later modified, concerning the processes acting during the four stages of granite generation: melting, melt segregation and ascent, and emplacement. The active role of the mantle constitutes a fifth stage. Fluid assisted melting, deduced from metamorphic observations, was used to explain granite and granulite formation. Water seepage into meta-sedimentary ...

Vigneresse, Jean Louis

2004-01-01

203

Granite Sludge Reuse in Mortar and Concrete  

OpenAIRE

The disposal of solid wastes produced in granite industry to the environment without any treatment cause not only economical but also serious environmental problems. In this study Granite Powder (GP) which produced as solid waste from the cutting and polishing of granite rocks was reused as additive to mortar and concrete cement. Incorporation of GP in mortar and concrete in ratios of 10, 20, 30 wt.% improved mortar and concrete compressive strengths and the concrete workability. The experime...

Al- Hamaiedeh, Husam D.; Khushefati, Waleed H.

2013-01-01

204

Contrasting Structures and Deformational History of Syntectonic Granites of Campina Grande and Serra Redonda, Borborema Province, NE Brazil  

Directory of Open Access Journals (Sweden)

Full Text Available The Campina Grande and Serra Redonda Granites are intrusive along the contact of the Paleoproterozoic basement(Alto Moxotó Domain with the Tonian gneisses (Alto Pajeú Domain of the Borborema Province (northeast Brazil. TheCampina Grande Granite (U-Pb age = 581± 2 Ma shows a concentric oval-shaped structure whereas the Serra RedondaGranite (U-Pb age = 576 ± 3 Ma has a tabular shape, elongated in the NE-SW direction. The plutons are separated bythe left-lateral Galante transcurrent shear zone. In this study, the anisotropy of magnetic susceptibility (AMS was appliedto 64 outcrops of granites to determine the internal structures of these plutons and to explore the relationship betweenmagmatism and deformation in an orogenic setting. The magnetic fabrics are concordant with the metamorphic structure ofthe host rocks. Strike-slip shear zones controlled the emplacement of the Serra Redonda Granite, as indicated by sigmoidalfoliation, defining shear bands associated with the Galante shear zone. In contrast, the magmatic/magnetic fabric of theCampina Grande granite seems to have been produced by body (ascensional forces. The pluton displays an inward dipping, concentric planar fabric parallel to the wall rock contact and lineations highly oblique to the foliation trend. The fabric of the Campina Grande pluton is consistent with a magma moving over a ramp dipping to southwest, with the lineation at high angle to the NE-trending flow direction. The contrasting structures of the plutons reflect the episodic nature of orogenic deformation, which was punctuated by the alternation of weak and strong strains, affecting the fabric development of the syntectonic intrusions.

Sérgio Wilians de Oliveira Rodrigues

2011-04-01

205

Two Appollo 12 Granit Rock Fragments: Evidence for the Priximal Coexistence of High-Th Impact Melt Breccia and Granite  

Science.gov (United States)

We characterize a lunar granite fragment and a granitic breccia. The breccia’s granitic component is that of the granite fragment if it equilibrated with a more mafic lithology. We infer a source region with granite and high-Th impact melt breccia.

Seddio, S. M.; Korotev, R. L.; Jolliff, B. L.

2012-03-01

206

Uranium-lead age determinations on granitic rocks from the eastern Bushveld Complex  

International Nuclear Information System (INIS)

Uranium-lead age determinations were carried out on four types of granitic rocks from the eastern Bushveld Complex. The oldest rocks in the area are gneisses and felsites - 2604 plus minus 100 m.y. old - which form the centre of the Dennilton dome. The Rooiberg felsites could not be dated directly because of the absence of zircon, however a porphyritic granite sill, which shows intrusive relations with the Rooiberg felsites, was dated at 2090 plus minus 40 m.y., an age which can also be regarded as a minimum age for the Rooiberg felsites. No reliable age could be determined for the granophyres because of the large amount of lead-loss reflected in the zircon. The majority of zircons from these granophyres showed a peculiar hieroglyphic texture, a phenomena which has not yet been recorded in literature. The samples collected from the granites gave an age of 1950 plus minus 80 m.y. and thus form part of the Nebo Granite. Attempts have been made to obtain more concordant zircon ages throughout the present study. Although some success was achieved by analysing different size fractions of a zircon population, the non-magnetic fractions gave the most promising results

207

Hercynian late-post-tectonic granitic rocks from the Fornos de Algodres area (Northern Central Portugal)  

Science.gov (United States)

The Fornos de Algodres Complex (FAC) comprises several intrusions of late-post-tectonic Hercynian granitic rocks ranging in composition from hornblende granodiorites and quartz monzodiorites, through coarse porphyritic biotite granites and two-mica granites (coarse-, medium- and fine-grained), to muscovite-rich leucogranites. Field and regional constraints show that the emplacement of this large, composite, batholithic complex post-dates the main Variscan regional deformation phases (D 1+D 2+D 3) and associated metamorphic events. Field, petrographic and geochemical data suggest a strong genetic relationship between most of the members of the FAC. However, their Rb-Sr and Sm-Nd isotopic signatures appear to rule out any genetic process involving a single homogeneous source and/or closed-system fractional crystallization of the same parental magma. A model involving hybridization of mantle-derived basaltic liquids with crustal anatectic melts followed by further contamination and fractional crystallization is proposed to explain the isotopic and geochemical variation trends defined by the FAC granitic rocks.

Azevedo, M. R.; Nolan, J.

1998-10-01

208

Network Intrusion Forensic Analysis Using Intrusion Detection System  

OpenAIRE

The need for computer intrusion forensics arises from the alarming increase in the number of computer crimes that are committed annually. After a computer system has been breached and an intrusion has been detected, there is a need for a computer forensics investigation to follow. Computer forensics is used to bring to justice, those responsible for conducting attacks on computer systems throughout the world. Because of this the law must be follow precisely when conducting a forensics investi...

Manish Kumar; Hanumanthappa, Dr M.; Suresh Kumar, Dr T. V.

2011-01-01

209

Archean high-Mg monzodiorite-syenite, epidote skarn, and biotite-sericite gold lodes in the Granny Smith-Wallaby district, Australia: U-Pb and Re-Os chronometry of two intrusion-related hydrothermal systems  

Science.gov (United States)

The Granny Smith (37 t Au production) and Wallaby deposits (38 t out of a 180 t Au resource) are located northeast of Kalgoorlie, in 2.7 Ga greenstones of the Eastern Goldfields Province, the youngest orogenic belt of the Yilgarn craton, Western Australia. At Granny Smith, a zoned monzodiorite-granodiorite stock, dated by a concordant titanite-zircon U-Pb age of 2,665 ± 3 Ma, cuts across east-dipping thrust faults. The stock is fractured but not displaced and sets a minimum age for large-scale (1 km) thrust faulting (D2), regional folding (D1), and dynamothermal metamorphism in the mining district. The local gold-pyrite mineralization, controlled by fractured fault zones, is younger than 2,665 ± 3 Ma. In augite-hornblende monzodiorite, alteration progressed from a hematite-stained alkali feldspar-quartz-calcite assemblage and quartz-molybdenite-pyrite veins to a late reduced sericite-dolomite-albite assemblage. Gold-related monazite and xenotime define a U-Pb age of 2,660 ± 5 Ma, and molybdenite from veins a Re-Os isochron age of 2,661 ± 6 Ma, indicating that mineralization took place shortly after the emplacement of the main stock, perhaps coincident with the intrusion of late alkali granite dikes. At Wallaby, a NE-trending swarm of porphyry dikes comprising augite monzonite, monzodiorite, and minor kersantite intrudes folded and thrust-faulted molasse. The conglomerate and the dikes are overprinted by barren (1,600-m-long replacement pipe, which is intruded by a younger ring dike of syenite porphyry pervasively altered to muscovite + calcite + pyrite. Skarn and syenite are cut by pink biotite-calcite veins, containing magnetite + pyrite and subeconomic gold-silver mineralization (Au/Ag = 0.2). The veins are associated with red biotite-sericite-calcite-albite alteration in adjacent monzonite dikes. Structural relations and the concordant titanite U-Pb age of the skarn constrain intrusion-related mineralization to 2,662 ± 3 Ma. The main-stage gold-pyrite ore (Au/Ag >10) forms hematite-stained sericite-dolomite-albite lodes in stacked D2 reverse faults, which offset skarn, syenite, and the biotite-calcite veins by up to 25 m. The molybdenite Re-Os age (2,661 ± 10 Ma) of the ore suggests a genetic link to intrusive activity but is in apparent conflict with a monazite-xenotime U-Pb age (2,651 ± 6 Ma), which differs from that of the skarn at the 95% confidence level. The time relationships at both gold deposits are inconsistent with orogenic models invoking a principal role for metamorphic fluids released during the main phase of compression in the fold belt. Instead, mineralization is related in space and time to late-orogenic, magnetite-series, high-Mg monzodiorite-syenite intrusions of mantle origin, characterized by Mg/(Mg + FeTOTAL) = 0.31-0.57, high Cr (34-96 ppm), Ni (22-63 ppm), Ba (1,056-2,321 ppm), Sr (1,268-2,457 ppm), Th (15-36 ppm), and rare earth elements (total REE: 343-523 ppm). At Wallaby, shared Ca-K-CO2 metasomatism and Th-REE enrichment (in allanite) link Au-Ag mineralization in biotite-calcite veins to the formation of the giant epidote skarn, implicating a Th + REE-rich syenite pluton at depth as the source of the oxidized hydrothermal fluid. At Granny Smith, lead isotope data and the Rb-Th-U signature of early hematite-bearing wall-rock alteration point to fluid released by the source pluton of the differentiated alkali granite dikes.

Mueller, Andreas G.; Hall, Gregory C.; Nemchin, Alexander A.; Stein, Holly J.; Creaser, Robert A.; Mason, Douglas R.

2008-03-01

210

Rb-Sr age of Godhra and related granites, Gujrat, India  

International Nuclear Information System (INIS)

Rubidium and strontium determinations are reported for Godhra and geographically related granites from central Gujarat. The whole rock data define a Rb-Sr isochron corresponding to a common age of 955 +- 2O m.y. and initial Sr ratio of 0.7130 +- 0.0O1. This age is distinctly older than the age of 735 m.y. reported for the Erinpura suite of rocks from Mount Abu in western Rajasthan and from Idar in nothern Gujarat. There are at least two generations of post-Delhi intrusive rocks in the Gujarat precambrian. Boitites associated with these granites have the same age as the whole-rocks within experimental error indicating the absence of significant metamorphic heating since the time of emplacement. It is significant that rocks of similar age occur in the Rajasthan Precambrian mainly in the axial zone of the Aravalli Mountains. (author)

211

Intrusion Detection A Machine Learning Approach  

CERN Document Server

This important book introduces the concept of intrusion detection, discusses various approaches for intrusion detection systems (IDS), and presents the architecture and implementation of IDS. It emphasizes on the prediction and learning algorithms for intrusion detection and highlights techniques for intrusion detection of wired computer networks and wireless sensor networks. The performance comparison of various IDS via simulation will also be included.

Tsai, Jeffrey JP

2011-01-01

212

Application of Sm/Eu/, Rb/Sr, Ce/Yb and F-Rb ratios to discriminate between Tin mineralized and non-mineralized S-type granites  

International Nuclear Information System (INIS)

Mash had granites and Gran diorites are divided into three groups bas sed on their ages and composition: (1) Deh Now-Vakilabad-Kuhsangi Granodiorites and Quartz monzodiorites, (2) Sang bast Granite and (3) Khalaj- Gheshlagh Biotite-muscovite Granite. All these intrusive s belong to S-type granite, The oldest are in the range of intermediate and the youngest are acidic in composition. Intrusive rocks in the area of Deh now to Kuhsangi show trend of differentiation. Major, trace and rare earth elements within the source rocks of porphyry Sn, Mo, and Cu deposits were compared and very distinct differences were noticed. Differentiation index, Rb/Sr, Ce/Yb, and (Sr87/Sr86) ratios can be used to identify the source rocks for porphyry Sn, Mo, or Cu. Major, as well as trace and rare earth elements of Mash had Granites and Granodiorites were compared with tin mineralized granites of the world. As a result, four diagrams were presented to be utilized in order to discriminate between Sn mineralized and non-mineralized granites. Such as Rb to the ratio of Sm/Eu, F to Rb and the three angle of F, Rb, Sr + Ba

213

Gravity data inversion as a probe for the 3D shape at depth of granitic bodies  

International Nuclear Information System (INIS)

Granitic intrusions represent potential sites for waste disposal. A well constrained determination of their geometry at depth is of importance to evaluate possible leakage and seepage within the surroundings. Among geophysical techniques, gravity remains the best suited method to investigate the 3D shape of the granitic bodies at depth. During uranium exploration programmes, many plutons emplaced within different geochemical and tectonic environment have been surveyed. The quality of gravity surveying depends on the intrinsic accuracy of the measurements, and also on their density of coverage. A regularly spaced and dense coverage (about 1 point/km2) of measurements over the whole pluton and its nearby surroundings is needed to represent the gravity effect of density variations. This yields a lateral resolution of about 0.5 kilometer, or less depending on depth and roughness of the floor, for the interpretation of the Bouguer anomaly map. We recommend the use of a 3D iterative method of data inversion, simpler to run when the geometry and distribution of the sources are already constrained by surface data. This method must take into account the various density changes within the granite and its surroundings, as well as the regional effect of deep regional sources. A total error in the input data (measurements, densities, regional field) is estimated at 6%. We estimate that the total uncertainty on the calculated depth values does not exceed ± 15%. Because th values does not exceed ± 15%. Because of good coverage of gravity measurements, the overall shape of the pluton is certainly better constrained than the depth values themselves. We present several examples of gravity data inversion over granitic intrusions displaying various 3D morphologies. At a smaller scale mineralizations are also observed above or close to the root zones. Those examples demonstrate the adequacy of joint studies in constraining the mode of magma emplacement before further studies focussing to environmental problems. 59 refs, 9 figs

214

Integration of remote sensing data and ground data as an aid to exploration for granite related mineralization, Salamanca Province, W Spain  

International Nuclear Information System (INIS)

This paper reports that the major geological features associated with the Los Santos tungsten skarn are: vicinity of the intrusive granite contact: geochemical zoning within the granite; anomalous width of the contact aureole; presence of fault zones; development of limonitic soil; presence of limestone horizons. Digital image processing techniques are applied to recognize and enhance these features in satellite images and airborne geophysical datasets. In satellite images the granites are textually distinct from other terrains, due to a higher degree of variation between adjoining pixels and a higher density of lineaments. Supervised classification of TM-bands 3,4,5 and 7 allows discrimination of granite and regional metamorphic terrain, while contact-metamorphic and limonitic soils are classified better using bands 1,3,4 and 7. Airborne magnetometry discriminates well between granites and sediments. The magnetization of the sedimentary rocks in the contact aureole is reset due to thermal and chemical overprinting. This is visible in the magnetic image. Large faults are detected. Radiometric data allow distinction between granite and sediments and recognition of the geochemical zoning within the granite

215

Conventional U-Pb dating versus SHRIMP of the Santa Barbara Granite Massif, Rondonia, Brazil  

Science.gov (United States)

The Santa Ba??rbara Granite Massif is part of the Younger Granites of Rondo??nia (998 - 974 Ma) and is included in the Rondo??nia Tin Province (SW Amazonian Craton). It comprises three highly fractionated metaluminous to peraluminous within-plate A-type granite units emplaced in older medium-grade metamorphic rocks. Sn-mineralization is closely associated with the late-stage unit. U-Pb monazite conventional dating of the early-stage Serra do Cicero facies and late-stage Serra Azul facies yielded ages of 993 ?? 5 Ma and 989 ?? 13 Ma, respectively. Conventional multigrain U-Pb isotope analyses of zircon demonstrate isotopic disturbance (discordance) and the preservation of inherited older zircons of several different ages and thus yield little about the ages of Sn-granite magmatism. SHRIMP U-Pb ages for the Santa Ba??rbara facies association yielded a 207Pb/206Pb weighted-mean age of 978 ?? 13 Ma. The textural complexity of the zircon crystals of the Santa Ba??rbara facies association, the variable concentrations of U, Th and Pb, as well as the mixed inheritance of zircon populations are major obstacles to using conventional multigrain U-Pb isotopic analyses. Sm-Nd model ages and ??Nd (T) values reveal anomalous isotopic data, attesting to the complex isotopic behaviour within these highly fractionated granites. Thus, SHRIMP U-Pb zircon and conventional U-Pb monazite dating methods are the most appropriate to constrain the crystallization age of the Sn-bearing granite systems in the Rondo??nia Tin Province.

Sparrenberger, I.; Bettencourt, J.S.; Tosdal, R.M.; Wooden, J.L.

2002-01-01

216

Status of the GRANIT facility  

CERN Document Server

The GRANIT facility is a follow-up project, which is motivated by the recent discovery of gravitational quantum states of ultracold neutrons. The goal of the project is to approach the ultimate accuracy in measuring parameters of such quantum states and also to apply this phenomenon and related experimental techniques to a broad range of applications in particle physics as well as in surface and nanoscience studies. We overview the current status of this facility, the recent test measurements and the nearest prospects.

Roulier, Damien; Baessler, Stefan; Clément, Benoît; Morton, Daniel; Nesvizhevsky, Valery; Pignol, Guillaume; Rebreyend, Dominique

2014-01-01

217

Thermomechanical properties of Stripa granite  

International Nuclear Information System (INIS)

The Stripa material properties testing program was initiated to study, by laboratory testing, the thermomechanical behavior of the Stripa rock mass and to provide material properties for input into numerical programs for simulation of the in situ heater experiments at Stripa. The portion of the program dealing with measurement of elastic moduli and coefficients of thermal expansion of dry, intact samples of Stripa granite was completed in fiscal year 1980. A summary of the most significant findings resulting from tests on six samples are presented in this report

218

Open magma chamber processes in the formation of the Permian Baima mafic-ultramafic layered intrusion, SW China  

Science.gov (United States)

The Baima mafic-ultramafic layered intrusion of the 260-Ma Emeishan Large Igneous Province (ELIP) hosts the second largest Fe-Ti-(V) oxide deposit in the Panxi region, SW China. It is a ~ 1600-m-thick layered body intruded by slightly younger syenitic and granitic plutons. The intrusion includes the Lower and Upper Zones. Troctolite and olivine pyroxenite of the Lower Zone contains conformable oxide ore layers, whereas the Upper Zone consists of olivine gabbro and gabbro with abundant apatite in the higher level. The crystallization order of the silicates in the Baima intrusion is olivine ? plagioclase ? clinopyroxene. Fe-Ti oxides (titanomagnetite and ilmenite) crystallized after olivine, and possibly plagioclase. The oxide ores in the Lower Zone show slightly LREE enriched patterns with (La/Yb)N values between 2.0 and 6.4, and positive Eu anomalies (Eu/Eu*) of 1.0 to 2.7. In contrast, olivine gabbros in the Lower Zone display stronger LREE enrichments (La/YbN = 7.7-14.0) and positive Eu anomalies (Eu/Eu* = 2.8-3.3). Gabbros in the Upper Zone have REE profiles characterized by intermediate LREE enrichments with (La/Yb)N values of 3.2 to 11.2 and positive Eu anomalies of 2.1 to 3.0. Primitive mantle-normalized trace element patterns are characterized by negative La-Ce, Th, Sm and positive Nb-Ta, Ba and Ti anomalies in oxide ores and negative Th-U, Zr-Hf and positive Ba, Sr and Ti anomalies in olivine gabbro and gabbro. Fo of olivine and An of plagioclase remain roughly constant from 0 to ~ 90 m in the Lower Zone, indicating that the magma chamber was continuously filled by compositionally similar magmas during the initial stage. Three magma replenishments occurred afterwards in the upper part of the Lower Zone and the Upper Zone based on compositional reversals of plagioclase, olivine and Sr isotope. Mass balance calculations show that the Baima parental magma can produce all oxide ores under closed system conditions. A wide range of An values of plagioclase within thin sections and disequilibrium Sr isotopic compositions of plagioclase both along the stratigraphic profile (87Sr/86Sri = 0.70312-0.70510) and within thin sections indicate convection and co-accumulation of cumulus plagioclase that had crystallized from different magmas. We propose that the ~ 1600m-thick Baima intrusion formed in an open and isotopically heterogeneous magma chamber that was periodically recharged by compositionally similar or more primitive magmas. In each replenishment cycle, the magma underwent progressive crustal contamination and fractional crystallization. Convection and sorting of crystals based on density differences result in igneous layering characterized by intervals of oxide ores, troctolite and olivine gabbro.

Liu, Ping-Ping; Zhou, Mei-Fu; Wang, Christina Yan; Xing, Chang-Ming; Gao, Jian-Feng

2014-01-01

219

Thermal History and Crystallinity of Sheet Intrusions  

Science.gov (United States)

Magma emplaced in a sheet intrusion has two potential fates: to crystallize, or quench to glass. Rapidly chilled sheet margins are typically glassy or microcrystalline, while interiors are coarser-grained. The actual textures result from a combination of thermal history and crystallization kinetics, which are related by various feedback mechanisms. The thermal history of cooling sheet intrusions is often approximated using the analytical solution for a semi-infinite half-space, which uses constant thermal properties such as heat capacity (CP), thermal diffusivity (D) and thermal conductivity (k = D?CP), where ? is density. In reality, both CP and D are strongly T-dependent for glasses and crystals, and melts have higher CP and lower D than crystals or glasses. Another first-order feature ignored in the analytical solution is latent heat of crystallization (?Hxt), which can be implemented numerically as extra heat capacity over the crystallization interval. For rhyolite melts, D is ~0.5 mm2s-1 and k is ~1.5 Wm-1K-1, which are similar to those of major crustal rock types and granitic protoliths at magmatic temperatures, suggesting that changes in thermal properties accompanying partial melting of the crust should be relatively minor. Numerical models of hot (~920°C liquidus for 0.5 wt.% H2O) shallow rhyolite intrusions indicate that the key difference in thermal history between bodies that quench to obsidian, and those that crystallize, results from the release of latent heat of crystallization, which enables bodies that crystallize to remain at high temperatures for much longer times. The time to solidification is similar in both cases, however, because solidification requires cooling through the glass transition (Tg ~620°C) in the first case, and cooling only to the solidus (~770°C) in the second. For basaltic melts, D is ~0.3 mm2s-1 and k is ~1.0 Wm-1K-1, compared to ~0.6 mm2s-1 and 2.5 Wm-1K-1 for crystalline basalt or peridotite at magmatic temperatures, suggesting that changes in thermal properties accompanying partial melting of the mantle or crystallization of basalt may be important. Numerical models of basaltic sheet intrusions indicate that they will almost always crystallize, even at sheet margins, because their emplacement temperature (~1220°C) is sufficiently high that the country rock adjacent to the sheet will be raised above the Tg of the melt (~650°C). The long period of time spent above Tg, combined with the rapid crystallization kinetics of basaltic melts, ensures that crystallization is near-complete, even if the crystal size is small, except where unusually rapid chilling occurs due to efficient convective or radiative losses (for example subaerial, subaqeous or subglacial lava flows).

Whittington, A. G.; Nabelek, P. I.; Hofmeister, A.

2011-12-01

220

Gas intrusion into SPR caverns  

Energy Technology Data Exchange (ETDEWEB)

The conditions and occurrence of gas in crude oil stored in Strategic Petroleum Reserve, SPR, caverns is characterized in this report. Many caverns in the SPR show that gas has intruded into the oil from the surrounding salt dome. Historical evidence and the analyses presented here suggest that gas will continue to intrude into many SPR caverns in the future. In considering why only some caverns contain gas, it is concluded that the naturally occurring spatial variability in salt permeability can explain the range of gas content measured in SPR caverns. Further, it is not possible to make a one-to-one correlation between specific geologic phenomena and the occurrence of gas in salt caverns. However, gas is concluded to be petrogenic in origin. Consequently, attempts have been made to associate the occurrence of gas with salt inhomogeneities including anomalies and other structural features. Two scenarios for actual gas intrusion into caverns were investigated for consistency with existing information. These scenarios are gas release during leaching and gas permeation through salt. Of these mechanisms, the greater consistency comes from the belief that gas permeates to caverns through the salt. A review of historical operating data for five Bryan Mound caverns loosely supports the hypothesis that higher operating pressures reduce gas intrusion into caverns. This conclusion supports a permeability intrusion mechanism. Further, it provides justification for operating the caverns near maximum operating pressure to minimize gas intrusion. Historical gas intrusion rates and estimates of future gas intrusion are given for all caverns.

Hinkebein, T.E.; Bauer, S.J.; Ehgartner, B.L.; Linn, J.K.; Neal, J.T.; Todd, J.L.; Kuhlman, P.S.; Gniady, C.T. [Sandia National Labs., Albuquerque, NM (United States). Underground Storage Technology Dept.; Giles, H.N. [Dept. of Energy, Washington, DC (United States). Strategic Petroleum Reserve

1995-12-01

221

Space-time variations in British Caledonian granites: some geophysical correlations  

International Nuclear Information System (INIS)

The characteristics of 30 'granites' from the postulated Caledonian (Iapetus Ocean) suture zone of mainland Britain are discussed. Geophysical (gravity, aeromagnetic), geochemical (U/Pb and initial 87Sr/86Sr) and isotopic age data indicate that these British Caledonian intrusions (390-600 Ma) can be divided into two distinct groups temporally, each of which is further subdivided spatially. The temporal division applies throughout the British province and separates a pre-Silurian (group 1) suite of low-volume, low-mobility magmas, which were intruded under compressive conditions, from a Siluro-Devonian (group 2) suite of large volume, mobile magmas intruded under tensional conditions. The spatial subdivisions of groups 1 and 2 are made between intrusions emplaced to either side of the postulated ENE-WSW Iapetus Ocean suture which runs through the Solway Firth. (Auth.)

222

Head and neck malignancies in younger patients  

International Nuclear Information System (INIS)

We treated 23 (1.4% of all our primary cases) younger patients who are from 15 years old to 29 years old with head and neck malignancies at the Department of Head and Neck Surgery of the Miyagi Cancer Center Hospital for the past 12 years. There were 12 male and 11 female, and the sex ratio was approximately 1:1. There were 12 oral cancer patients, 6 epipharyngeal cancer patients and so on. There were 14 squamous cell carcinomas, 3 nasopharyngeal carcinomas and so on. 60% of all cases were squamous cell carcinomas. Clinically, advanced stage (stage III and IV) was diagnosed in 70% of patients at presentation. Although 19 patients had no past history, 2 patients had bronchial asthma, one had schizophrenia, and one had psychological disorder. Radical treatment was performed in 20 of 23 examples. The estimated Kaplan-Meier 5-year cause-specific survival rates for all patients were 76% and the 10-year cause-specific survival rates were 63%, respectively. It was thought that survival consequence was excellent in the whole. The problems of head and neck tumor treatment in a younger patient were thought about with late effect by radioactive rays and genital disorder by cancer chemotherapy. (author)

223

Rhyolite intrusions in the intracaldera Bishop Tuff, Long Valley Caldera, California  

Science.gov (United States)

Drilling of the Long Valley Exploratory Well on the resurgent dome in the Long Valley Caldera revealed > 300 m cumulative thickness of granophyric intrusions within the 1180-m-thick, 760 ka intracaldera Bishop Tuff. The intrusions are aphyric to sparsely plagioclase-phyric, high-silica, high-barium and low-strontium rhyolites. They resemble the lavas of the Early Rhyolite, the first phase of post-caldera volcanism. A mean 40Ar/39Ar age of 590 ± 17 ka from a part of a shallow intrusion is coeval with Early Rhyolite volcanism. A second mean age of 454 ± 17 ka from the same intrusion may reflect either younger Early Rhyolite activity with no external equivalent or hydrothermal resetting of the argon system. Hydrothermal alteration of the intrusions is characterized by introduction of quartz, calcite and pyrite and formation of illite/smectite. High CO2 content of fluids apparently inhibited zeolite formation. Alteration varies locally within intrusions and intrusive groups and does not vary systematically with depth. Oxygen shows consistent depletion of the 18O isotope from an initial magmatic composition of + 6.0 to + 8.5‰ to values ranging from +1.4 to -0.4‰. The constant oxygen isotope depletion most likely reflects alteration of intrusions due to local emplacement-induced hydrothermal circulation rather than a caldera-scale hydrothermal system. In contrast, 18O depletion of the host Bishop Tuff increases regularly with depth (except at an intrusive contact). A pre-Early Rhyolite geothermal gradient of approximately 70 °C/km was inferred. This is substantially higher than the current gradient but substantially lower than expected for the case of a conductive regime over a shallow residual magma chamber. Either the intrusions were fed from a deep chamber, or a cool hydrologic recharge regime was established early in caldera history. The age, thickness and suspected lateral extent of these shallow intrusions are such that emplacement of the intrusions, rather than inflation of a shallow chamber, is responsible for resurgence of the central Long Valley Caldera. Similar intrusions occur in another well on the resurgent dome ( LV13-21 ) but not in wells located off the dome.

McConnell, V. S.; Shearer, C. K.; Eichelberger, J. C.; Keskinen, M. J.; Layer, P. W.; Papike, J. J.

1995-08-01

224

Shrimp U-Pb age and Sr-Nd isotopes of the Morro do Baú mafic intrusion: implications for the evolution of the Arenópolis volcano-sedimentary sequence, Goiás Magmatic Arc  

OpenAIRE

The Arenópolis volcano-sedimentary sequence is located in the southern part of the Goiás Magmatic Arc and includes a ca. 900 Ma calc-alkaline arc sequence made of volcanic rocks ranging in composition from basalts to rhyolites, metamorphosed under greenschist to amphibolite facies. Small calc-alkaline gabbro to granite sub-volcanic bodies are also recognized. The Morro do Baú intrusion is the largest of these intrusions, and is made of gabbros and diorites. Zircon grains separated from one...

Pimentel, Ma?rcio M.; Hollanda, Maria Helena B. M.; Richard Armstrong

2003-01-01

225

The Mount Kinabalu Granite of North Borneo: Result and Cause of Orogenic Deformation  

Science.gov (United States)

Mount Kinabalu is a granite body in north Borneo that intrudes rocks deformed in the Early Miocene Sabah Orogeny following subduction of the South China continental margin beneath the north Borneo margin. Kinabalu is the highest mountain in SE Asia at 4100m and ice action during Pleistocene glaciations has resulted in excellent exposure of the summit area. The granite has previously been interpreted as a compositionally zoned, steeply sided pluton with a central biotite granodiorite, surrounded by hornblende granite and a marginal porphyritic facies. New zircon U-Pb SHRIMP ages record emplacement and crystallization. Zircon fission track data and apatite (U-Th)/He dates record the development and exhumation of the orogen. U-Pb SHRIMP analyses of concentric growth zones in zircon date crystallisation of the granite at between 7.85 and 7.22 Ma. The ages support models relating the Kinabalu granite to anatexis not subduction. Inherited zircon ages suggest melting of deep crust, including South China continental crust and arc basement rocks. SHRIMP dating provides insight into rates of magmatic processes. The entire pluton was emplaced and crystallised within a period of less than 700,000 years, with at least four pulses of magmatism, each lasting about 100,000 yrs. Zircon fission track data record post-crystallisation cooling but abundant dislocations make apatite fission track data unreliable. Apatite (U-Th)/He ages have a broadly concentric pattern. The thermochronological data indicate cooling of the granite was a response to growth of topography and rapid exhumation of the orogen. We interpret all these data to indicate that Kinabalu has a sheet-like character with the oldest biotite granite near the summit. The porphyritic facies represents the last and deepest major intrusive pulse. There was significant topographic expression by around 6 Ma with subsequent NE-SW trending extensional faulting on the south side of the body. The granite is the product of collision-related thickening in the Sabah orogeny, but is now itself driving fold and thrust deformation offshore after rapid uplift and exhumation following loss of a deep lithospheric root.

Cottam, M.; Hall, R.; Sperber, C.; Armstrong, R.

2008-12-01

226

P-T path fluid evolution in the Gross Spitzkoppe granite stock, Namibia  

Directory of Open Access Journals (Sweden)

Full Text Available The Gross Spitzkoppe granite stock (GSS is a zoned 30 km^2 epizonal intrusion that consists of three main granites: 1 medium-grained biotite granite (marginal, 2 a coarse-grained biotite granite, and 3 a central, porphyritic granite. The stock contains pegmatites as banded marginal stockscheiders and isolated pockets composed of large alkali feldspar and quartz, dark mica, interstitial fluorite, and euhedral topaz and beryl crystals. In the porphyritic granite there are local wolframite-bearing greisens and hydrothermal fluorite and topaz-rich veins.Fluid inclusion studies were conducted on: 1 topaz and quartz crystals from the marginal stockscheider; 2 quartz, topaz, fluorite and beryl crystals from isolated pegmatites; 3 topaz from a miarolitic pegmatite; 4 beryl and quartz veins from greisenized porphyritic granite; and 5 fluorite from a late fluorite vein inthe coarse-grained biotite granite. Preliminary data indicate the presence of three compositionally distinct primary and pseudosecondary inclusion types that are of late magmatic-hydrothermal origin.Type 1. Low salinity (0–10 eq. wt% NaCl H2O (± CO2 inclusions that homogenize to the liquid phase in the temperature range of 300 to 550?C. These inclusions are from quartz, topaz and beryl. Inclusions in fluorite from the fluorite vein homogenize at ~170?C and have a salinity of ca. 1–2 eq. wt% NaCl.Type 2. Saline (25–30 eq. wt% NaCl halite-bearing H2O (± CO2 inclusions that homogenize to the liquid phase in the temperature range of 300 to 400?C. These inclusions are from quartz.Type 3. Low salinity (0–3 eq. wt% NaCl H2O-CO2 inclusions that homogenize to vapor phase in the temperature range of 330 to 550?C. These inclusions are from quartz and topaz.Hydrothermal fluids from greisen minerals are represented by type 1 and type 2 H2O inclusions. They are predominantly of low salinity (~8 eq. wt% NaCl and homogenize to the liquid phase in the temperature range of 300 to 500?C. Isochores for contemporaneous type 2 and type 3 inclusions with homogenization temperature range of 330 to 400?C indicate a maximum trapping pressure of about 900 bar for the marginal stockscheider.

Stephen Frindt

2002-01-01

227

Incorporation of granite waste in red ceramics  

International Nuclear Information System (INIS)

This work has as its objective to evaluate the effect of granite powder waste incorporation in a red ceramic body. The granite waste came from an industry of stone sawing operations located in the municipal area of Santo Antonio de Padua, State of Rio de Janeiro, Brazil. Initially the granite sawing waste was characterized in terms of chemical composition, particles size distribution and X-ray diffraction. After that, clay mixtures with 0, 10, 20, 30 and 40 wt.% of granite waste were prepared. Red ceramic specimens were fabricated by extrusion and then fired in an industrial furnace at 970 deg. C. The specimens were also tested to determine the water absorption, linear shrinkage and three points bending flexural strength. Microstructural evaluation was carried out by scanning electron microscopy, X-ray diffraction and mercury porosimetry. The results indicate that granite waste presents favorable characteristics for addition into red ceramics due to facilities on the drying stages and decrease in porosity

228

Garnet geochemistry of tungsten-mineralized Xihuashan granites in South China  

Science.gov (United States)

The Xihuashan complex intrusion in South China, which is emplaced at ca. 154 Ma, mainly comprises medium-grained porphyritic biotite granite, medium-grained biotite granite, and fine-grained two-mica granite. Medium-grained biotite and fine-grained two-mica granites are important tungsten-bearing granites and contain an unusual amount of garnet. Garnets from this intrusion are dominated by almandine and spessartine, which constitute 94% to 99% of the total molecular composition of the garnet. These garnets display unusual compositional zoning. The cores of these garnets are rich in heavy rare earth element (HREE), Y, Ca, and contain abundant HREE- and Y-rich mineral inclusions. Their rims are free of mineral inclusions and have low of these elements. Two types of fluorite inclusions exist in garnet: Y fluorite and Y-poor fluorite. Garnet exhibits specific Mn zoning with a relatively Mn-poor core but a relatively Mn-rich rim, thus constituting a specific “spessartine inverse bell-shaped profile” that belongs to typical magmatic garnets. All analyzed garnets have high REE content and exhibit HREE-enriched and LREE-depleted patterns with strong negative Eu anomalies. The incorporation of REE into garnet is in part controlled by its crystal chemistry, with REE3 + following a coupled substitution of the type [Fe2 +,Mn2 +]- 1VIII[REE3 +]+ 1VIII[Si4 +]- 1IV[Z3 +]+ 1IV. The texture and compositional zoning of garnet suggest that garnet growth is largely controlled by the pressure-temperature-composition condition of magmatic evolution, internal crystal-chemical parameters, and kinetics during mineral growth. The garnet core grows in near equilibrium with magmatic melt under a relatively high pressure-temperature (P-T) condition. By contrast, the garnet rim grows rapidly by the coexisting melt-fluid phase and CO2-rich volatile environment under a relatively low P-T condition, which is virtually unfavorable for the incorporation of REE into the magmatic garnet structure. Garnet fingerprints the magmatic-hydrothermal transition during crystallization of these granites.

Yang, Jie-hua; Peng, Jian-tang; Hu, Rui-zhong; Bi, Xian-wu; Zhao, Jun-hong; Fu, Ya-zhou; Shen, Neng-Ping

2013-09-01

229

Late-Archaean Potassic Granite from the Bundelkhand Craton, Central India  

Science.gov (United States)

Late-Archaean granitoids, show wide range of compositional variation: (i) TTG like granitoids with strongly fractionated REE patterns, which can be both Na-rich and K-Mg-rich (Sanukitoids) (ii) K-rich, Mg-poor biotite granites with less fractionated REE patterns and showing negative Eu-anomalies (type area, the Closepet Granite, Eastern Dharwar Craton, India). Amongst them Late-Archaean Sanukitoid or K-rich Closepet-type granitoids are most widely reported from the Archaean Cratons world-wide: Superior Province, Canada, Pilbara Craton, Yilgarn Craton, Antarctica, Limpopo Belt, Dharwar Craton. Several models proposed so far for the origin of these granitoids mostly include partial melting of hydrated basalts, reaction of slab melts with mantle wedge peridotites, re-melting of an enriched mantle and then mixing of the resulting melt with the anatectic melt generated during the melting of continental crust in subduction zone settings. The Closepet-type potassic biotite-rich granites were mostly produced by re-melting of TTG-like continental basements most likely in a subduction zone setting. Most of the proposed models suggest such partial melting to have taken place in garnet-stability field and some in orthopyroxene-stability field. In this study we report late-Archaean (~2.61-2.5 Ga) potassic granite from the Bundelkhand Craton in central India. The Late-Archaean granitoids recorded from the craton are intrusive into the high-grade supracrustal rocks of the craton. They are classified as coarse grained grey, pink porphyritic granite, medium granied pink granite, granite porphyry and fine-grained pink granite. The supracrustal rocks of the craton have been metamorphosed at ~2.78 Ga under high-pressure conditions (~17-18 kbar)- medium temperature (600ºC) in a subduction zone setting. The intrusions of the granitoids at ~2.6-2.5 Ga mark the stability of the craton. The pink-porphyritic granite studied here preserves plagioclase-potash feldspar-orthopyroxene-muscovite-biotite-quartz. Plagioclase megacrysts mostly contain orthopyroxene inclusions and are rimmed by anti-perthite and potash feldspar. Biotite and muscovite mostly occur along the potash feldspar grain boundaries or along the grain fractures. The textural observations hence indicate that these granitic rocks are formed in two stages: (i) initial TTG-like melts formed by partial melting of pre-existing mafic supracrustal rocks in the orthopyroxene-stability field, as evidenced by orthopyroxene inclusions in the plagioclase megacrysts, followed by (ii) fractionation of plagioclase crystals, thus making the melt progressively enriched in potassium that led to rimming of the plagioclase megacrysts by anti-perthite or potash feldspar. Biotite and muscovite were formed during later retrogression due to fluid ingression. Whether such magma-forming processes were related to the ~2.78 Ga tectonics recorded from the craton or may be related to a short phase of collision tectonics post to that, needs further investigation.

Sarkar, Saheli; Saha, Lopamudra; Nasipuri, Pritam; Pati, Jayanta Kumar; Patole, Vishal

2014-05-01

230

Geochemical studies of granitic rocks of Kallur area, Manvi Taluk, Raichur district, Karnataka (India).  

Science.gov (United States)

The geochemical data is much widely used in establishing the overall chemical relation existing between the different rock types with their parentage. A major impetus for this shift comes not only from the need to understand and quantify better the spatial and temporal evolution, with emphasis on the younger greenstone belts (Kallur copper formations), but also from the recognition that such knowledge could form the basis for the sustainable development of our natural resources. In addition, the recurrence of natural hazards has reinforced the need to learn more about the mechanics and to develop predictive modeling with advanced technical tools. This paper is emphasizing on Granodiorites of Kallur area of Manvi Taluk, Raichur District to substantiate the classical approaches of exploration and data gathering through quantitative methods of data processing and interpretation. The trilinear diagram indicates that the granites are rich in Potash and Soda. This clearly indicates that Granites are fairly rich in K2O than Na2O. PMID:22324155

Raghavendra, N R; Reddy, R Purushottam; Nijagunappa, R

2011-01-01

231

Geology and mineral and hydrocarbon potential of northern Yukon Territory and northwestern District of Mackenzie. Chapter Fourteen:Petrology of the northern Yukon intrusive suite  

Energy Technology Data Exchange (ETDEWEB)

An exploratory study of the petrology and geochemistry of the intrusive rocks of northern Yukon was undertaken using samples from Operation Porcupine and from the collections of the University of Alberta in an effort to study the intrusive relationships between several of the plutons and mapped stratigraphic units. The intrusive rocks of the northern Yukon appear to represent two distinct petrogenetic suites. With the exception of the Dave Lord, which is a nepheline-normative rock, all other plutons belong to the late orogenic granite-granodiorite association. The nepheline-normative rocks, consists largely of perthite, crystallized from an undersaturated high potassic magma, which are normally generated in the mantle and are emplaced in the rigid plate during crustal extension. The geochronologic data is not sufficiently precise to establish the relative ages of the various plutons. If all are essentially coeval, juxtaposition of different tectonic environments after intrusion provides the most plausible explanation. An alternative hypothesis suggests that a spread of 80 million years allowed time for intrusion of synkinematic and late kinematic granites, followed by an episode of post-kinematic extensional syenite intrusion. 12 refs., 2 tabs.

Burwash, R. A. [Geological Survey of Canada, Ottawa, ON (Canada)

1997-06-01

232

Is stratospheric air getting younger with time?  

Science.gov (United States)

Most climate models have predicted that with the increase in greenhouse gases concentrations, the stratospheric circulation will intensify, showing younger age-of-air (AoA) values in this region (e.g. Butchart et al., 2010; WMO, 2011). However, balloon and satellite observations do not agree with the widespread modelled trend towards younger age-of-air (Engel et al., 2009; Stiller et al., 2012). To increase our confidence in climate-chemistry projections, the causes for the apparent age-of-air disagreement between observations and most models need to be identified. Here we have carried out stratospheric simulations with a chemistry transport model (CTM) to evaluate the stratospheric circulation with the ERA-Interim dataset produced by the European Centre for Medium-Range Weather Forecasts (ECMWF). The ERA-Interim reanalysis provides age-of-air (AoA) distributions in very good agreement with observations in the lower stratosphere. Given this agreement, we have used our simulations to quantify interannual variability and trends in the stratospheric AoA for the whole ERA-Interim period (1979-present). Our model results with ERA-Interim fields disagree with the decreasing tendency in age-of-air widespread in most models, but are in good agreement with the recent age-of-air studies based on observations. To explore potential causes for the AoA trends in our model, Lagrangian calculations are also performed to assess mixing processes for the ERA-Interim period. Potential links between our modelled AoA trends and stratospheric ozone evolution are also shown. References: Butchart, et al., 2010. J. Climate, 23, 5349-5374, doi:10.1175/2010JCLI3404.1. Engel et al., 2009. Nat. Geosci. 2: 28-31, doi:10.1038/ngeo388. Stiller et al., 2012. Atmos. Chem. Phys. 12: 3311-3331, doi:10.5194/acp-12-3311-2012. WMO. 2011. Global Ozone Research and Monitoring Project -Report No. 52.

Monge-Sanz, Beatriz; Chipperfield, Martyn; Dee, Dick; Simmons, Adrian; Stiller, Gabriele

2014-05-01

233

AMS studies in Portuguese variscan granites  

Science.gov (United States)

A large volume of Variscan granitic rocks outcrop in Central Iberian Zone which are well documented concerning geological mapping, petrography and geochemistry but whose magnetic characteristics and fabric remain unknown. In this study we summarize the available AMS data from approximately 644 sampling stations (5152 samples) on different massifs of Variscan Portuguese granites. Despite their different geological, petrographic and geochemical characteristics, magnetic susceptibility (K) values obtained for the majority of the studied granites range from 15 to 300 × 10-6 SI. The dominant paramagnetic behaviour of the granite bodies reflects the presence of ilmenite as the main iron oxide. This feature indicates the reduced conditions involved in the granite melt formation during the Variscan orogeny. The two-mica granites show K values ranging between 15 to 70 × 10-6 SI which are lower than values displayed by the biotite-rich facies scattered within the interval of 70 and 300 × 10-6 SI. The magnetite-bearing granites are scarce but represented in Lavadores, Gerês and Manteigas. Even so, only the Lavadores body could be considered as a true magnetite-type granite (K >3.0 × 10-3 SI) in face of its K, comprised between 1550 and 19303 × 10-6 SI. Magnetic anisotropy can be used as a "marker" for the deformation experienced by granite mushes during their crustal emplacement and further cooling. Magnetic anisotropy can thus be correlated with the finite deformation of a rock, as record by mineral fabrics. Post-tectonic granites, such as those from Vila Pouca de Aguiar, Pedras Salgadas, Caria, Vila da Ponte, Chaves and Lamas de Olo, have a magnetic anisotropy solid-state deformation microstructures (like square-shaped quartz subgrains, recrystallized quartz grains, coupled by kinked biotites and bands of quartz surrounded by mica flakes). In the late to post-tectonic granite bodies, such as those from Castro Daire, Valpaços, Castelo Branco, Mangualde-Trancoso or Serra da Estrela, the magnetic anisotropy falls within the 2.5% and 5% range. The magnetic anisotropy of the Lavadores granite is always higher than 10%. This feature, however, reflects the presence of rough alignments of magnetite co-existent with magmatic to submagmatic microstructures. The shape parameter T is quite variable; however, the average values, for all the massifs, are always higher than zero, suggesting the presence of oblate AMS ellipsoids due to the magnetocrystalline anisotropy of biotite. The values of magnetic susceptibility and magnetic anisotropy allowed a petrophysical characterization of the paramagnetic Variscan granites as was proposed by Sant'Ovaia & Noronha (2005).

Sant'Ovaia, Helena; Martins, Helena; Noronha, Fernando

2014-05-01

234

Site selection methods for nuclear waste storage in sub-schistic granites  

International Nuclear Information System (INIS)

Intrusive granites in schists, where most of the roof is at a depth of several hundred metres can be regarded as favourable sites for storing radioactive waste since the schistic cover has extremely low permeability. This configuration exists in various parts of France. In this paper the authors describe methods which can be applied to the study of such structures, taking a region in the Armorican Massif as a reference example. The geological evidence here showed an extensive zone with a slight gravimetric anomaly around a few granite outcrops dispersed in the schists. This structure gave reason to believe that a shallow granite mass would be found under the schistic cover, and geological and gravimetric surface studies did indeed prove that this supposition was correct. Apart from the slight gravimetric anomaly, the extent of which has been confirmed and the outlines determined, the transformations (contact metamorphism and hydrothermalism) of the enclosing schists are particularly indicative of the presence of granite. The gravimetric model shows that the thickness of the granite is at least 2.3 km and provides an initial representation of the shape and depth of the roof. These results, together with those of the structural analysis, can be used to demarcate a favourable region for investigations at depth which will make it possible: to monitor the geological structures; to define the geotechnical characteristics of the formations; to analyse and model the hydrogeological behaviour, at present known only from surface studies which do not appear to indicate any circulation of water upwards towards the surface

235

Archaean tonalitic-trondhjemitic and granitic plutonism in the Gaviao block, Sao Francisco craton, Bahia, Brazil: geochemical and geochronological characteristics  

International Nuclear Information System (INIS)

The granitic-gneissic terranes of the Gaviao Block in the central-southern Sao Francisco Craton are a Key area to the understanding of the evolution of the South American Platform. The Archaean granitic-gneissic rocks are intimately associated with the Umburanas and Contendas Mirante greenstone belts. The metamorphic grades vary from greenschist to amphibolite facies. These rocks were intensely deformed and intruded by Paleoproterozoic granites. The main evolution of the Gaviao Block is market by the formation of granitoid nuclei during various episodes of TTG plutonism between 3.2 and 3.4 Ga. The TDM Sm-Nd model ages for these granitoids range from 3.2 and 3.6 Ga, indicating involvement of sialic crust in their genesis, in agreement with the ?Nd(t) values between -4.0 and -1.3. Between 3.1 and 2.5 Ga, the Gaviao Block was affected by volcanic and sedimentary activity associated with the formation of the Umburanas and Contendas Mirante greenstone belts, intruded by granites about 2.75 and 2.5 Ga ago. During the paleoproterozoic, the Gaviao Block was regionally deformed and metamorphosed, and intruded by granites between 2.1 and 1.9 Ga. During the mesoproterozoic, tectonic and metamorphic activity occurred between 1.2 and 1.0 Ga as suggested by resetting of Rb-Sr and K-Ar systematics. Finally, regional tectono-thermal overprints in the areas occurred during the Neoproterozoic. These episodes are accompanied by the intrusion of mafic dikes at aboud by the intrusion of mafic dikes at about 0.9 Ga K-Ar ages given by biotites fall within the range 0.5-0.7 Ga and mark the end of the cratonization stage. (author)

236

Radioactive waste disposal in granite  

International Nuclear Information System (INIS)

Within the framework of completing its knowledge of various rock formations, the Federal Government also considers the suitability of granite for radioactive waste disposal. For this purpose, the Federal Minister of Research and Technology participated from 1983 to 1990 in relevant research and development activities in the NAGRA rock laboratory at Grimsel, Switzerland. After about 17 field tests, it can be stated that the understanding of basic connections and interactions between the mechanical behaviour of the rock, which is determined, for instance, by natural or artificially induced rock movements, and the hydrogeological or rock hydraulic relations could be clearly improved. So far, the German share in the project costs amounts to a total of approximately DM 20.7 million. Till the end of 1993, further activities are scheduled to be carried out which will require financial funds of about DM 6.3 million. (orig./HSCH)

237

Crustal growth and reworking during Lapland-Kola orogeny in northern Fennoscandia: U-Pb and Lu-Hf data from the Nattanen and Litsa-Aragub-type granites  

Science.gov (United States)

In this paper we present new zircon U-Pb, Lu-Hf and REE data for Palaeoproterozoic intrusions (Nattanen- and Litsa-Aragub-type granites) of the Fennoscandian shield, to obtain a more detailed understanding of their petrogenesis. The intrusions form a chemically homogenous group of SiO2-rich A-type, post-kinematic granites that were emplaced between 1.79 and 1.76 Ga. The Hf isotopes indicate that the source was dominated by an Archaean crustal component although a mantle contribution cannot be ruled out. The isotopic data further constrain the evolution of the Archaean and Palaeoproterozoic crust and the assembly of the Nuna (Columbia) supercontinent. The Nattanen- and Litsa-Aragub-type granites are part of a voluminous phase of granitoid magmatism in Fennoscandia at 1.8-1.75 Ga, reflecting large-scale processes at the margin of the Nuna supercontinent.

Heilimo, Esa; Elburg, Marlina A.; Andersen, Tom

2014-09-01

238

Shoshonitic intrusion magmatism in Pajeu-Paraiba belt: the Bom Jardim complex  

International Nuclear Information System (INIS)

The Bom Jardim complex is a multi phase intrusion emplaced within the basement of the Pajeu-Paraiba belt, in the Borborema province, N.E., Brazil, during the Pan African (Brasiliano) orogeny, 600 Ma ago. The Bom Jardim complex is primarily composed of monzonites and syenites with subordinated granites. The major and trace elements geochemistry has established a shoshonitic affinity for the monzonite-syenite assemblages, whereas the granites are clearly of a high-K calc-alkaline character. The main geochemical trends determined for the complex are the result of fractionation of mainly amphibole, biotite, alkali feldspar ±clinopyroxene within the developing magmas. The enrichment in transition metal elements, LILE and high LILE/HSFE ratios, coupled with an initial Sr sup(87)/Sr sup(86) ratio of 0.70709 is consistent with a subduction related magma source. (author)

239

The Maua granitic massif, Central Ribeira Belt, Sao Paulo, Brazil: petrography, geochemistry and U-Pb dating  

Energy Technology Data Exchange (ETDEWEB)

The Maua granitic massif is an elongated body dominated by a porphyritic biotite monzogranite which grades, in its southwestern extremity, to lighter equi granular granite and greisenized (tourmaline)-biotite-muscovite leuco granite. Abundant enclaves can be divided in three types: grey micro granular enclaves, with rounded shapes and igneous textures, are compositionally similar to the enclosing porphyritic granites; dark, rounded, micaceous enclaves have high K/Na, and may correspond to highly assimilated meta sedimentary xenoliths; and angulous gneiss xenoliths seem to be fragments of an unexposed type of country rock. The primitive magmas that formed the massif were Zr, P and LREE-saturated, and became progressively enriched in U, Cs, Y, HREE, F and possibly Ta. Geochemical data show that most of the observed compositional variation can be a reflection of crystal fractionation at the level of emplacement. However, other processes such as magma mixing, contamination and post-magmatic alteration seem to respond for local chemical variations. U-Pb monazite dating point to a crystallization age of 588 {+-} 2 Ma which is ca. 20 myr. younger than those of nearby crust-derived syn-orogenic granites. (author)

Filipov, Marcelo [Sao Paulo Univ., SP (Brazil). Escola Politecnica. Dept. de Engenharia de Minas]. E-mail: filipov@usp.br; Janasi, Valdecir de Assis [Sao Paulo Univ., SP (Brazil). Inst. de Geociencias]. E-mail: vajanasi@usp.br

2001-09-01

240

Geochronology and tectonic significance of Middle Proterozoic granitic orthogneiss, North Qaidam HP/UHP terrane, Western China  

Science.gov (United States)

Amphibolite-facies para- and orthogneisses near Dulan, in the southeast part of the North Qaidam terrane, enclose minor ultra-high pressure (UHP) eclogite and peridotite. Field relations and coesite inclusions in zircons from paragneiss suggest that felsic, mafic, and ultramafic rocks all experienced UHP metamorphism and a common amphibolite-facies retrogression. Ion microprobe U-Pb and REE analyses of zircons from two granitic orthogneisses indicate magmatic crystallization at 927 ?? Ma and 921 ?? 7 Ma. Zircon rims in one of these samples yield younger ages (397-618 Ma) compatible with partial zircon recrystallization during in-situ Ordovician-Silurian eclogite-facies metamorphism previously determined from eclogite and paragneiss in this area. The similarity between a 2496 ?? 18 Ma xenocrystic core and 2.4-2.5 Ga zircon cores in the surrounding paragneiss suggests that the granites intruded the sediments or that the granite is a melt of the older basement which supplied detritus to the sediments. The magmatic ages of the granitic orthogneisses are similar to 920-930 Ma ages of (meta)granitoids described further northwest in the North Qaidam terrane and its correlative west of the Altyn Tagh fault, suggesting that these areas formed a coherent block prior to widespread Mid Proterozoic granitic magmatism. ?? Springer-Verlag 2006.

Mattinson, C.G.; Wooden, J.L.; Liou, J.G.; Bird, D.K.; Wu, C.L.

2006-01-01

241

The University of Texas at Austin - Rob's Granite Page  

Science.gov (United States)

Robert Reed, a structural geologist from the University of Texas at Austin, presents research and educational materials about granite at this website. At the General Info link, users can learn about granitic phases, llano uplift, and aplites. Students can discover some of the minerals in granite through a clickable granite image. With the help of numerous pictures, visitors can discover the diversity of granite and many of its locations throughout the world. Users can take a virtual tour of the Enchanted Rock, a granite dome in central Texas. The site features a simple explanation about the color and identification of minerals. Reed also educates visitors as to how granites are like ice cream.

242

Precambrian crustal evolution and Cretaceous–Palaeogene faulting in West Greenland: Pre-Nagssugtoqidian crustal evolution in West Greenland: geology, geochemistry and deformation of supracrustal and granitic rocks north-east of Kangaatsiaq  

Directory of Open Access Journals (Sweden)

Full Text Available The area north-east of Kangaatsiaq features polyphase grey orthogneisses, supracrustal rocks and Kangaatsiaq granite exposed within a WSW–ENE-trending synform. The supracrustal rocks are comprised of garnet-bearing metapelites, layered amphibolites and layered, likewise grey biotite paragneisses. Their association and geochemical compositions are consistent with a metamorphosed volcano-sedimentary basin (containing both tholeiitic and calc-alkali lavas and is similar to other Archaean greenstone belts. The Kangaatsiaq granite forms a 15 × 3 km flat, subconcordant body of deformed,pink, porphyritic granite occupying the core of the supracrustal synform, and is demonstrably intrusive into the amphibolites. The granite displays a pronounced linear fabric (L or L > S. Thepost-granite deformation developed under lower amphibolite facies conditions (400 ± 50°C, and is characterised by a regular, NE–SW-trending subhorizontal lineation and an associated irregular foliation, whose poles define a great circle; together they are indicative of highly constrictional strain. The existence of a pre-granite event is attested by early isoclinal folds and a foliation within the amphibolites that is not present in the granite, and by the fact that the granite cuts earlier structures in the supracrustal rocks. This early event, preserved only in quartz-free lithologies, resulted in high-temperature fabrics being developed under upper amphibolite to granulite facies conditions.

Watt, Gordon R.

2006-12-01

243

Locally advanced breast cancer in younger women  

Directory of Open Access Journals (Sweden)

Full Text Available Background: Standard treatment of locally advanced breast cancer is not yet established. In most institutions treatment is multimodal and consists of primary chemotherapy, surgical treatment with or without radiotherapy (RT and hormonal therapy. To find out whether the age influences the kind of surgical treatment in a group of locally advanced breast cancer patients (LABC patients responding to neo-adjuvant chemotherapy. Methods: Analysis included 39 LABC patients treated from January 2000 till January 2003 with neo-adjuvant chemotherapy and surgical treatment in Clinical Center of Montenegro, Podgorica. All patients had locally advanced disease (T2, T3 or T4b and/or N1-2 M1 sc. Patients with T4d tumors were excluded. The treatment consisted of neo-adjuvant chemotherapy, mostly anthracycline based, and surgical treatment - radical mastectomy or breast conserving surgery. Additional procedures after surgical treatment included 3-4 cycles of the same chemotherapy, hormonal treatment and/or RT. Results: Median age of patients was 47 years (range: 24-67 years. Thirty patients were initially in stage IIIA (14 post- and 16 premenopausal patients respectively, 6 patients in stage IIIB (2 post- and 4 premenopausal respectively, and 3 patients in stage IV, with supraclavicular node involvement (M1+sc, 2 post- and 1 premenopausal, respectively. Applied preoperative chemotherapy was anthracycline-based regimen (FAC, 3-6 cycles except in one patient in premenopausal group and 2 patients in postmenopausal group, who had been treated with CMF chemotherapy due to anthracycline contraindications. All analyzed patients responded to neo-adjuvant chemotherapy, mostly with partial or minimal remission of their tumors. In a whole group 15/39 (38% patients had breast conserving surgery (8 pre-, 7 postmenopausal, respectively, 24/39 (61% patients radical mastectomy (13 pre-, 11 postmenopausal, respectively. In a group of patients old 40 years and younger only 2 partial resections were performed (2/9, 22%, and 7 radical mastectomies. Conclusion: Although in a small group of patients, our results confirmed that effective neo-adjuvant chemotherapy enabled breast surgery of LABC, even breast conservative procedure in some patients. However, breast conservation was not possible in majority of young patients. This suggests the investigation of more aggressive neo-adjuvant treatments, especially in patients old 40 years or younger.

Laki?evi? Jadranka

2003-01-01

244

Analysis of the Younger Dryas Impact Layer  

Energy Technology Data Exchange (ETDEWEB)

We have uncovered a thin layer of magnetic grains and microspherules, carbon spherules, and glass-like carbon at nine sites across North America, a site in Belgium, and throughout the rims of 16 Carolina Bays. It is consistent with the ejecta layer from an impact event and has been dated to 12.9 ka BP coinciding with the onset of Younger Dryas (YD) cooling and widespread megafaunal extinctions in North America. At many locations the impact layer is directly below a black mat marking the sudden disappearance of the megafauna and Clovis people. The distribution pattern of the Younger Dryas boundary (YDB) ejecta layer is consistent with an impact near the Great Lakes that deposited terrestrial-like ejecta near the impact site and unusual, titanium-rich projectile-like ejecta further away. High water content associated with the ejecta, up to 28 at. percent hydrogen (H), suggests the impact occurred over the Laurentide Ice Sheet. YDB microspherules and magnetic grains are highly enriched in TiO{sub 2}. Magnetic grains from several sites are enriched in iridium (Ir), up to 117 ppb. The TiO{sub 2}/FeO, K/Th, TiO{sub 2}/Zr, Al{sub 2}O{sub 3}/FeO+MgO, CaO/Al{sub 2}O{sub 3}, REE/ chondrite, FeO/MnO ratios and SiO{sub 2}, Na{sub 2}O, K{sub 2}O, Cr{sub 2}O{sub 3}, Ni, Co, U, Th and other trace element abundances are inconsistent with all terrestrial and extraterrestrial (ET) sources except for KREEP, a lunar igneous rock rich in potassium (K), rare-earth elements (REE), phosphorus (P), and other incompatible elements including U and Th. Normal Fe, Ti, and {sup 238}U/{sup 235}U isotopic abundances were found in the magnetic grains, but {sup 234}U was enriched over equilibrium values by 50 percent in Murray Springs and by 130 percent in Belgium. 40K abundance is enriched by up to 100 percent in YDB sediments and Clovis chert artifacts. Highly vesicular carbon spherules containing nanodiamonds, glass-like carbon, charcoal and soot found in large quantities in the YDB layer are consistent with an impact followed by intense burning. Four holes in the Great Lakes, some deeper than Death Valley, are proposed as possible craters produced by the airburst breakup of a loosely aggregated projectile.

Firestone, Richard B.; West, Allen; Revay, Zsolt; Hagstrum, Jonathon T,; Belgya, Thomas; Hee, Shane S. Que; Smith, Alan R.

2010-02-27

245

Granite fracture index to check suitability of granite outcrops for quarrying  

OpenAIRE

the general characterization of the discontinuities of 10 granite rock masses in NE Portugal. During the study some discontinuity characteristics such as orientation, persistence, aperture, trace length and spacing were evaluated. The differences in the characteristics of the selected granites were described, and the most important exploration factors were identified. In the granites studied, most of the joints are oriented from N10°E to N50°E, which is compatible with the regional...

Sousa, L. M. O.

2007-01-01

246

NETWORK INTRUSION DETECTION AND PREVENTION ATTACKS  

OpenAIRE

Intrusion detection is an important technology in business sector as well as an active area of research. It is an important tool for information security. A Network Intrusion Detection System is used to monitor networks for attacks or intrusions and report these intrusions to the administrator in order to take evasive action. Today computers are part of networked; distributed systems that may span multiple buildings sometimes located thousands of miles apart. The network of such a system is a...

Harpreet kaur

2012-01-01

247

Survey paper on intrusion detection techniques  

OpenAIRE

Network security has been one of the most important problems in Computer Network Management and Intrusion is the most publicized threats to security. In recent years, intrusion detection has emerged as an important field for network security. IDSs obtain better results when each class ofattacks is treated as a separate problem and handled by specialized algorithms. Now in days various model and method are available for intrusion detection. In this paper, we present a study of intrusion...

Rachna Kulhare; Dr. Divakar Singh

2013-01-01

248

Grusification of granite (scheme based on the study of granites from Sudety Mts., SW Poland)  

Science.gov (United States)

Gruses that are developed on the Karkonosze granite (three outcrops) and the Izera granite (one outcrop) were investigated using optical microscope, scanning electron microscope equipped with EDS and electron microprobe, X-ray diffraction, IR spectrometry, chemical analysis (ICP-AES and ICP-MS), hydrogen and oxygen isotopic ratio determination and K-Ar dating. Three groups of samples were distinguished according to the degree of grusification (group I - compact granite; group II - friable granite; group III - granitic grus). The results of the examination allowed to present the simplified scheme of the grusification: 1. Development of microcracks (caused by tectonic stress, mechanical upload or magma cooling processes) promote circulation of hydrothermal fluids in granites; 2. The presence of the microcracks in granite facilitate the circulation of low-temperature fluids (low-temperature hydrothermal or weathering fluids). Fluids cause hydration and expansion of primary biotite (vermiculitization), what leads to development of secondary cracks in a rock. Fluids can also induce advanced alteration of plagioclases into clay minerals (mainly smectite or vermiculite). Expansion of biotite during vermiculitization is the most important factor in grusification. Other processes of alteration also contribute to grusification. Hydrothermal fluids in granite contribute the increase of alteration degree of primary minerals (e.g. sericitization and albitization of feldspar, chloritization or muscovitization of biotite, decomposition of monazite-(Ce) and formation of secondary REE phosphates). If primary biotite is subjected to muscovitization or chloritization, complete grusification of granite does not occur because of lack of vermiculitation.

Kajdas, Bartlomiej; Michalik, Marek

2014-05-01

249

Bokan Mountain peralkaline granitic complex, Alexander terrane (southeastern Alaska): evidence for Early Jurassic rifting prior to accretion with North America  

Science.gov (United States)

The circular Bokan Mountain complex (BMC) on southern Prince of Wales Island, southernmost Alaska, is a Jurassic peralkaline granitic intrusion about 3 km in diameter that crosscuts igneous and metasedimentary rocks of the Alexander terrane. The BMC hosts significant rare metal (rare earth elements, Y, U, Th, Zr, and Nb) mineralization related to the last stage of BMC emplacement. U–Pb (zircon) and 40Ar/39Ar (amphibole and whole-rock) geochronology indicates the following sequence of intrusive activity: (i) a Paleozoic basement composed mainly of 469 ± 4 Ma granitic rocks; (ii) intrusion of the BMC at 177 ± 1 Ma followed by rapid cooling through ca. 550 °C at 176 ± 1 Ma that was synchronous with mineralization associated with vertical, WNW-trending pegmatites, felsic dikes, and aegirine–fluorite veins and late-stage, sinistral shear deformation; and (iii) intrusion of crosscutting lamprophyre dikes at >150 Ma and again at ca. 105 Ma. The peralkaline nature of the BMC and the WNW trend of associated dikes suggest intrusion during NE–SW rifting that was followed by NE–SW shortening during the waning stages of BMC emplacement. The 177 Ma BMC was synchronous with other magmatic centres in the Alexander terrane, such as (1) the Dora Bay peralkaline stock and (2) the bimodal Moffatt volcanic suite located ~30 km north and ~100 km SE of the BMC, respectively. This regional magmatism is interpreted to represent a regional extensional event that precedes deposition of the Late Jurassic – Cretaceous Gravina sequence that oversteps the Wrangellia and Alexander exotic accreted terranes and the Taku and Yukon–Tanana pericratonic terranes of the Canadian–Alaskan Cordillera.

Dostal, Jaroslav; Karl, Susan M.; Keppie, J. Duncan; Kontak, Daniel J.; Shellnutt, J. Gregory

2013-01-01

250

Geochemistry and Rb-sr geochronology of associated proterozoic peralkaline and subalkaline anorogenic granites from Labrador  

Science.gov (United States)

Anorogenic granites of middle to late Proterozoic age in the Davis Inlet — Flowers Bay area of Labrador are subdivided on the basis of petrology and geochemistry into three coeval suites. Two of these are high-temperature anhydrous hypersolvus granites: a peralkaline aegirine-sodic-calcic to sodic amphibole-bearing suite and a non-alkaline fayalite-pyroxene-bearing suite. The third is a group of non-alkaline subsolvus hornblende-biotite-bearing granites. Associated with the hypersolvus peralkaline suite is a group of genetically related syenites and quartz syenites. The granites cut ca. 3,000 Ma old Archaean gneisses as well as Elsonian layered basic intrusions of the Nain Complex. One of these, a crudely layered mass which ranges in composition from gabbro to diorite and monzonite, appears to be related to the syenites. The peralkaline granites and some of the syenites are extremely enriched in the high field-strength elements such as Y, Zr, Nd, as well as Rb, Ga and Zn, and have low abundances of Ba, Sr and most of the transition elements. In contrast, the non-alkaline hypersolvus and subsolvus granites do not show the same degree of enrichment. Concentration of the highly charged cations in the peralkaline suite is believed to be the result of halogen-rich fluid activity during fractionation of the magma. The sodic evolution trend in the peralkaline suite is reflected mineralogically by the development of aegirine and aegirine-hedenbergite solid solutions, and by a spectacular amphibole compositional range from katophorite through winchite, richterite, riebeckite to arfvedsonite and ferro eckermannite. Accessory phases which are ubiquitous in these rocks include aenigmatite, astrophyllite, fluorite, monazite and zircon. The non-alkaline hypersolvus granites typically contain iron-rich phases such as fayalite, eulite, ferrosilite-hedenbergite, and annite rich biotite. In the subsolvus granites, amphiboles range in composition from edenite through common hornblende to actinolite and also coexist with annite-rich biotite. Whole-rock and mineral isotopic data for the different suites yield isochrons that are within error of ca. 1,260 Ma, but they have variable initial 87Sr/86Sr ratios. The initial 87Sr/86Sr of the syenites and peralkaline granites (0.7076±11) is significantly lower than the initial 87Sr/86Sr of the subsolvus granites (0.7138±22). These isotopic data provide further confirmation of the importance of a late Elsonian alkaline event in Labrador which can be correlated with Gardar igneous activity in south Greenland. The petrogenesis of the peralkaline suite is interpreted to reflect the effects of fractionation of anhydrous phases from mantle derived basic magma which was contaminated during ascent by radiogenic partial melts of crustal derivation. The non-alkaline hypersolvus and subsolvus granites are interpreted as crustal melts which formed under conditions of variable P_{{text{H}}_{text{2}} {text{O}}} in response to the same thermal event, and which subsequently experienced feldspar fractionation during crystallization.

Collerson, Kenneth D.

1982-12-01

251

Limit of the radionuclides in granite  

International Nuclear Information System (INIS)

Granite is an important sort of building materials. Their radionuclide contents are limited by the national standard GB6566-2001 just as other building materials. This standard divides them into main materials and decorative materials, and relaxes the limit of the latter obviously. Owing to the consideration of public dose limit and environment protection, this method needs discussion. Otherwise, red granite contains high radionuclide contents relatively, especially the sort of Indian Red, and need be paid more attention

252

Mineralogy, chemistry, and age of granitic veins at Nicholson's Point, South Coast, Natal  

International Nuclear Information System (INIS)

Undeformed granitic veins exposed at Nicholson's Point, southern Natal, intrude nearly all the foliated rock types between Drakes Beach and Leisure Bay and therefore appear to post-date the major deformation episodes. The veins define an en echelon array and appear to have been emplaced syn-tectonically to post-tectonically. In addition to quartz and feldspar, the veins are characterized by variable ferro magnesian minerals, namely, tourmaline, magnetite, dumortierite, and biotite. A Rb/Sr isotope study yields a date of 960 ± 32 Ma which is within error of the date of the nearby deformed Glenmore Granite. These results imply that much of the deformation history recorded in the southern sector of Natal Structural and Metamorphic Province either occurred within a relatively short period or that the age of the Glenmore Granite is a reset age. The veins represent one of the youngest events recognized in the tectonic and intrusive history of the Natal Structural and Metamorphic Province. 18 refs., 7 figs., 5 tabs

253

A study of the existing forms of uranium and its distribution in Chengshan granitic body  

International Nuclear Information System (INIS)

The existing forms of uranium and its distribution in Chengshan granitic body and country rocks have been investigatsed by the methods of fission-track and uranium maceration. Uranium can be divided into two groups, mobile and inert, according to the possibility of the maceration from rocks. Primary uranium exists mainly in two forms, simple oxides and solid solution and crystal structural incorporation. Whether it appears chiefly in the former form or latter one depends on uranium abundance and contents of accessory minerals in whole rock. Uranium enrichment, both in granite and country rocks, is closely associated with Fe. It is noteworthy that secondary Fe oxides absorb more uranium because of primary uranium mobilization. From country rocks (sedimentary rocks) to the intrusive contact zone, as the grain in ground mass increases in size, uranium bearing point sources decrease in number, and the remaining sources become more intense. Uraniumm contents in the country rocks close to the contact zone increase significantly under the influence of postmagmatic hydrothermal solution. Mean while, the ratio of uranium maceration becomes greater from the centre of the granitic body to the contact zone. Contents of mobile uranium increase from early to late in different intrusive stages. The change pattern of the existing forms of uranium is inert uranium, dispersive mobile uramium and concentrated mobile uranium. Only the rock high both in uranium contents and ratio of maceroth in uranium contents and ratio of maceration may produce more mobile uranium. There is a little possibility to leach enough uranium from the rock of the third stage to form deposits. The source of uranium is mainly due to magmatic differentiation

254

SHRIMP zircon U-Pb dating of the mafic and felsic intrusive rocks of the Saza area in the Lupa goldfields, southwestern Tanzania: Implication for gold mineralization  

OpenAIRE

The Lupa Goldfield (LGF) is one of the eight structural terranes in the NW – SE striking Ubendian Belt of SW Tanzania. The LGF is comprised of granitic gneisses with bands of amphibolites which are intruded by mafic intrusions including gabbros, granodiorites, diorites; and various granites as well as metavol-canics. These rocks are cross-cut by narrow mafic dykes and aplites. SHRIMP zircon U-Pb data are presented for the granodiorite and a mafic dyke that cross-cut the granodiorites in the...

Shukrani Manya

2012-01-01

255

Dioritic intrusions of the Slavkovský les (Kaiserwald), Western Bohemia: their origin and significance in late Variscan granitoid magmatism  

Science.gov (United States)

Mafic and intermediate intrusions occur in the Slavkovský les as dykes, sills and minor tabular bodies emplaced in metamorphic rocks or enclosed in late Variscan granites near the SW contact of the Western Krušné hory/Erzgebirge granite pluton. They are similar in composition and textures to the redwitzites defined in NE Bavaria. Single zircon Pb-evaporation analyses constrain the age of a quartz monzodiorite at 323.4 ± 4.4 Ma and of a granodiorite at 326.1 ± 5.6 Ma. The P- T range of magma crystallization is estimated at ~1.4-2.2 kbar and ~730-870°C and it accords with a shallow intrusion level of late Variscan granites but provides lower crystallization temperatures compared to the Bavarian redwitzites. We explain the heterogeneous composition of dioritic intrusions in the Slavkovský les by mixing between mafic and felsic magmas with a minor effect of fractional crystallization. Increased K, Ba, Rb, Sr and REE contents compared to tholeiitic basalts suggest that the parental mafic magma was probably produced by melting of a metasomatised mantle, the melts being close to lamprophyre or alkali basalt composition. Diorites and granodiorites originated from mixed magmas derived by addition of about 25-35 and 50 vol.%, respectively, of the acid end-member (granite) to lamprophyre or alkali-basalt magma. Our data stress an important role of mafic magmas in the origin of late Variscan granitoids in NW Bohemian Massif and emphasize the effect of mantle metasomatism on the origin of K-rich mafic igneous rocks.

Ková?íková, Pavla; Siebel, Wolfgang; Jelínek, Emil; Štemprok, Miroslav; Kachlík, Václav; Holub, František V.; Blecha, Vratislav

2010-04-01

256

Evolution of silicic magma in the upper crust: the mid-Tertiary Latir volcanic field and its cogenetic granitic batholith, northern New Mexico, USA  

Science.gov (United States)

Structural and topographic relief along the eastern margin of the Rio Grande rift, northern New Mexico, provides a remarkable cross-section through the 26-Ma Questa caldera and cogenetic volcanic and plutonic rocks of the Latir field. Exposed levels increase in depth from mid-Tertiary depositional surfaces in northern parts of the igneous complex to plutonic rocks originally at 3-5 km depths in the S. Erosional remnants of an ash-flow sheet of weakly peralkaline rhyolite (Amalia Tuff) and andesitic to dactitic precursor lavas, disrupted by rift-related faults, are preserved as far as 45 km beyond their sources at the Questa caldera. Broadly comagmatic 26 Ma batholithic granitic rocks, exposed over an area of 20 by 35 km, range from mesozonal granodiorite to epizonal porphyritic granite and aplite; shallower and more silicic phases are mostly within the caldera. Compositionally and texturally distinct granites defined resurgent intrusions within the caldera and discontinuous ring dikes along its margins: a batholithic mass of granodiorite extends 20 km S of the caldera and locally grades vertically to granite below its flat-lying roof. A negative Bouguer gravity anomaly (15-20 mgal), which encloses exposed granitic rocks and coincides with boundaries of the Questa caldera, defined boundaries of the shallow batholith, emplaced low in the volcanic sequence and in underlying Precambrian rocks. Paleomagnetic pole positions indicate that successively crystallised granitic plutons cooled through Curie temperatures during the time of caldera formation, initial regional extension, and rotational tilting of the volcanic rocks. Isotopic ages for most intrusions are indistinguishable from the volcanic rocks. These relations indicate that the batholithic complex broadly represents the source magma for the volcanic rocks, into which the Questa caldera collapsed, and that the magma was largely liquid during regional tectonic disruption. -from Author

Lipman, P.W.

1988-01-01

257

Rare metal granites and related rocks of the Ukrainian shield  

Directory of Open Access Journals (Sweden)

Full Text Available Two rare metal leucocratic granites, Perga and Kamennaya complexes, can be distinquished on the Ukrainian shield. The Perga complex consists of medium- and coarse grained, mainly porphyric, biotite, riebeckite and aegirine granites, granite porphyries, microclinites and albitites with rare metal mineralization (genthelvite, phenacite, tantalite, cassiterite and wolframite etc.. Granites from several stocks (up to 30 km2 in the northwestern part of the shield, situated along the fracture zone, restricted the large Korosten pluton of rapakivi granites to the northwest. The age of these granites (Pb-Pb and U-Pb methods on zircon and monazite practically coincide with the age of rapakivi granites being 1750 Ma. Within the Korosten complex of rapakivi granites we consider that zinnwaldite granites, which are characterized by fluorite and topazine mineralization, represent the final phase of pluton. These granites differ from the Perga ones by their low content of rare metals. The Kamennaya Mogila complex lies in the southeastern part of the Ukrainian shield. It consists of biotite and muscovite-biotite, medium- and coarse-grained (also porphyric, and occasionally greisining granites with rare metal mineralization (cassiterite, columbite, molybdenite, wolframite and beryl. Granites form several stocks (5-30 km2 situated 10-30 km to the west-northwest of the South-Kalchik gabbro-syenite-granite pluton. Granitoids in both of these complexes have similar isotopic ages (1800 Ma. Leucocratic subalkaline granites (the Novoyanisol type are known within the pluton itself, occupying an intermediate position between the above mentioned in terms of mineral and geochemical composition. The gabbro-syenite-granite formation of the Nearazov region has a substantial similarity to the anorthosite-rapakivi-granite formation. In this respect the relation of each of them to rare metal granites is rather remarkable. This relation is, most probably, not only spatial, but also genetic. The typical rare metal granites are situated not in the parent plutons but at some distance from them.

Esipchuk, K.Ye.

1993-12-01

258

Magnetic fabric and modeled strain distribution in the head of a nested granite diapir, the Melechov pluton, Bohemian Massif  

Science.gov (United States)

The Melechov pluton, Bohemian Massif, is interpreted as a mid-crustal nested granitic diapir with an apical part exposed at the present-day erosion level. The diapir head exhibits a concentric structure defined by lithologic zoning and by the anisotropy of magnetic susceptibility (AMS). In concert with theoretical models, outward-dipping margin-parallel magnetic foliations are associated with oblate shapes of the susceptibility ellipsoids and higher degree of anisotropy, passing inward into weaker triaxial to prolate fabric. By contrast, magnetic fabric in an inner granite unit is in places oriented at a high angle to internal contacts and is interpreted as recording an internal diapir circulation. We use inverse modeling to calculate strain variations across the diapir from the AMS data. The magnetic fabric parameters and calculated strains are in agreement with strain distribution in heads of model Newtonian diapirs traveling a distance of two body radii and suggest granitic magma ascent as a crystal-poor suspension followed by crystallization of fabric markers and their response to strain near the final emplacement level. The intrusive fabric thus formed late but, though generally weak, was still capable of recording incremental strain gradient in the granite diapir.

Truba?, Jakub; Žák, Ji?í; Chlupá?ová, Marta; Janoušek, Vojt?ch

2014-09-01

259

Archean and paleoproterozoic granitoids and crustal evolution of the Rio Maria granite-greenstone terrane, Eastern Amazonian craton Brazil  

International Nuclear Information System (INIS)

The Rio Maria Granite-Greenstone Terrane (RMGGT) is situated in the Caraj Province, which is the most important Archean domain of the Amazonian craton (Machado et al., 1991; Macambira and Lafon, 1995; Tassinari and Macambira, 1999; Santos et al., 2000; Dall'Agnol et al., 2000). Several Archean granitoid suites and supracrustal sequences have been described in the RMGGT (Dall'Agnol et al., 1997; Althoff et al., 2000; Souza et al., 2001). Geochemical and isotopic data are now available allowing a better evaluation of the crustal evolution of this terrane. Paleoproterozoic, A-type oxidized granites (Dall'Agnol et al., 1999a) are intrusive in the Archean rocks of the RMGGT and their evolution will also be discussed (au)

260

Sorption behaviour of granite for radionuclides in groundwater condition  

International Nuclear Information System (INIS)

The sorption behavior of granite for Cs and Nd in the underground water condition was investigated as the function of mineralogical alteration of granite and particle size. The physicochemical characterization of the granite samples was carried out in terms of mineral phase, pore structure and elements eluted by soft acid treatment as the function of alteration of the granite. The increase of porosity of granite, and phase change of biotite and plagioclase into chlorite and illite, respectively were observed with the increase of alteration degree. The sorption capacities of the series of granites slightly increased with the increase of alteration degree. (authors)

261

Adaptive Intrusion Data System (AIDS)  

International Nuclear Information System (INIS)

The adaptive intrusion data system (AIDS) was developed to collect data from intrusion alarm sensors as part of an evaluation system to improve sensor performance. AIDS is a unique data system which uses computer controlled data systems, video cameras and recorders, analog-to-digital conversion, environmental sensors, and digital recorders to collect sensor data. The data can be viewed either manually or with a special computerized data-reduction system which adds new data to a data base stored on a magnetic disc recorder. This report provides a synoptic account of the AIDS as it presently exists. Modifications to the purchased subsystems are described, and references are made to publications which describe the Sandia-designed subsystems

262

Adaptive Intrusion Data System (AIDS)  

Energy Technology Data Exchange (ETDEWEB)

The adaptive intrusion data system (AIDS) was developed to collect data from intrusion alarm sensors as part of an evaluation system to improve sensor performance. AIDS is a unique data system which uses computer controlled data systems, video cameras and recorders, analog-to-digital conversion, environmental sensors, and digital recorders to collect sensor data. The data can be viewed either manually or with a special computerized data-reduction system which adds new data to a data base stored on a magnetic disc recorder. This report provides a synoptic account of the AIDS as it presently exists. Modifications to the purchased subsystems are described, and references are made to publications which describe the Sandia-designed subsystems.

Corlis, N. E.

1980-05-01

263

NAVEGANTE : an intrusive browsing framework  

OpenAIRE

NAVEGANTE is a generic framework to build superior order proxies for intrusive browsing. This framework provides the means for developing tools that behave as proxies, but perform some processing task on the content that is being browsed. Parallel to this content processing, applications can also run other user-defined functions with different purposes and interfaces, but we'll explain those later. Currently, NAVEGANTE only builds applications that run as CGIs, but this is intended to change ...

Carvalho, Nuno; Almeida, J. J.; Sim Es, Alberto

2008-01-01

264

Towards an Effective Intrusion Response Engine Combined with Intrusion Detection in Ad Hoc Networks  

CERN Document Server

In this paper, we present an effective intrusion response engine combined with intrusion detection in ad hoc networks. The intrusion response engine is composed of a secure communication module, a local and a global response module. Its function is based on an innovative tree-based key agreement protocol while the intrusion detection engine is based on a class of neural networks called eSOM. The proposed intrusion response model and the tree-based protocol, it is based on, are analyzed concerning key secrecy while the intrusion detection engine is evaluated for MANET under different traffic conditions and mobility patterns. The results show a high detection rate for packet dropping attacks.

Mitrokotsa, Aikaterini; Douligeris, Christos

2008-01-01

265

Radiometric analysis of Chinese commercial granites  

International Nuclear Information System (INIS)

Due to the widespread use of granites as building and ornamental materials, measurements of 226Ra, 232Th and 40K activities in commercial granites have been carried out using a NaI(Tl) ?-ray spectrometer with a matrix-inversion-based spectral stripping technique. The concentrations of 226Ra, 232Th and 40K in Chinese commercial granite range from 14.5 to 204.7 Bq x kg-1, 16.7 to 186.7 Bq x kg-1 and 185.7 to 1745.6 Bq x kg-1, respectively. The mean values of the activity concentrations of 226Ra, 232Th and 40K in red and pink commercial granites are all higher than those in black and gray commercial ones. The radium equivalent activity (Raeq), the external hazard index (Hex), the internal hazard index (Hin ) and the annual gonadal dose equivalent (AGDE) were also calculated and compared to the international recommended values. Six types of red commercial granites (CBR, MLR, QXR, PBR, JXR, LQR, YDR and TSR) of China do not satisfy the universal standards. (author)

266

Shrimp U-Pb age and Sr-Nd isotopes of the Morro do Baú mafic intrusion: implications for the evolution of the Arenópolis volcano-sedimentary sequence, Goiás Magmatic Arc  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese A seqüência vulcano-sedimentar de Arenópolis, localizada na porção sul do Arco Magmárico de Goiás, inclui uma associação de rochas vulcânicas calci-alcalinas de arco com ca. 900 Ma de idade, constituída de rochas variando em composição entre basaltos e riolitos, metamorfisados em fácies xisto verde [...] a anfibolito. Pequenos corpos sub-vulcânicos de gabros a granitos calci-alcalinos são também reconhecidos. A intrusão do Morro do Baú é a maior dessas intrusões, compreendendo dioritos e gabros. Cristais de zircão separados de uma amostra de gabro e analisados no SHRIMP I indicaram a idade 206Pb/238U média de 890 +/- 8 Ma, mostrando que a intrusão é grosseiramente contemporânea, ou talvez um pouco mais jovem que as rochas vulcânicas. Ao contrário das rochas metavulcânicas, que são juvenis, a composição isotópica de Nd do gabro do Morro do Baú indica forte contaminação com material siálico arqueano (T DM de 2.8 Ga e EpsilonNd(T) igual a -9.7), representado na área por uma pequena fatia tectônica de rocha gnáissica arqueana/paleoproterozóica (gnaisse Ribeirão), e que representa a rocha encaixante da intrusão gabro-diorítica. A idade de cristalização de ca. 890 Ma representa, portanto, um limite mínimo para a acresção tectônica do gnaisse Ribeirão às rochas mais jovens da seqüência de Arenópolis. Os dados sugerem que esse evento foi precoce na evolução da seqüência vulcano-sedimentar de Arenópolis, provavelmente entre ca. 920 e 890 Ma. Abstract in english The Arenópolis volcano-sedimentary sequence is located in the southern part of the Goiás Magmatic Arc and includes a ca. 900 Ma calc-alkaline arc sequence made of volcanic rocks ranging in composition from basalts to rhyolites, metamorphosed under greenschist to amphibolite facies. Small calc-alkali [...] ne gabbro to granite sub-volcanic bodies are also recognized. The Morro do Baú intrusion is the largest of these intrusions, and is made of gabbros and diorites. Zircon grains separated from one gabbro sample and analyzed by SHRIMP I yielded the mean 206Pb/238U age of 890 +/- 8 Ma, indicating that the intrusion is roughly coeval or only slightly younger than the Arenópolis volcanics. Contrary to the metavolcanics, which are juvenile, the Nd isotopic composition of the Morro do Baú gabbro indicates strong contamination with archean sialic material (T DM of 2.8 Ga and EpsilonNd(T) of -9.7), represented in the area by an allochthonous sliver of archean/paleoproterozoic gneisses (Ribeirão gneiss) which are the country-rocks for the gabbro/dioritic intrusion. The emplacement age of ca. 890 Ma represents a minimum age limit for the tectonic accretion of the gneiss sliver to the younger rocks of the Arenópolis sequence. The data suggest that this happened early in the evolution of the Goiás Magmatic Arc, between ca. 920 and 890 Ma.

Márcio M., Pimentel; Maria Helena B. M., Hollanda; Richard, Armstrong.

2003-09-01

267

Shrimp U-Pb age and Sr-Nd isotopes of the Morro do Baú mafic intrusion: implications for the evolution of the Arenópolis volcano-sedimentary sequence, Goiás Magmatic Arc  

Directory of Open Access Journals (Sweden)

Full Text Available The Arenópolis volcano-sedimentary sequence is located in the southern part of the Goiás Magmatic Arc and includes a ca. 900 Ma calc-alkaline arc sequence made of volcanic rocks ranging in composition from basalts to rhyolites, metamorphosed under greenschist to amphibolite facies. Small calc-alkaline gabbro to granite sub-volcanic bodies are also recognized. The Morro do Baú intrusion is the largest of these intrusions, and is made of gabbros and diorites. Zircon grains separated from one gabbro sample and analyzed by SHRIMP I yielded the mean 206Pb/238U age of 890 +/- 8 Ma, indicating that the intrusion is roughly coeval or only slightly younger than the Arenópolis volcanics. Contrary to the metavolcanics, which are juvenile, the Nd isotopic composition of the Morro do Baú gabbro indicates strong contamination with archean sialic material (T DM of 2.8 Ga and EpsilonNd(T of -9.7, represented in the area by an allochthonous sliver of archean/paleoproterozoic gneisses (Ribeirão gneiss which are the country-rocks for the gabbro/dioritic intrusion. The emplacement age of ca. 890 Ma represents a minimum age limit for the tectonic accretion of the gneiss sliver to the younger rocks of the Arenópolis sequence. The data suggest that this happened early in the evolution of the Goiás Magmatic Arc, between ca. 920 and 890 Ma.A seqüência vulcano-sedimentar de Arenópolis, localizada na porção sul do Arco Magmárico de Goiás, inclui uma associação de rochas vulcânicas calci-alcalinas de arco com ca. 900 Ma de idade, constituída de rochas variando em composição entre basaltos e riolitos, metamorfisados em fácies xisto verde a anfibolito. Pequenos corpos sub-vulcânicos de gabros a granitos calci-alcalinos são também reconhecidos. A intrusão do Morro do Baú é a maior dessas intrusões, compreendendo dioritos e gabros. Cristais de zircão separados de uma amostra de gabro e analisados no SHRIMP I indicaram a idade 206Pb/238U média de 890 +/- 8 Ma, mostrando que a intrusão é grosseiramente contemporânea, ou talvez um pouco mais jovem que as rochas vulcânicas. Ao contrário das rochas metavulcânicas, que são juvenis, a composição isotópica de Nd do gabro do Morro do Baú indica forte contaminação com material siálico arqueano (T DM de 2.8 Ga e EpsilonNd(T igual a -9.7, representado na área por uma pequena fatia tectônica de rocha gnáissica arqueana/paleoproterozóica (gnaisse Ribeirão, e que representa a rocha encaixante da intrusão gabro-diorítica. A idade de cristalização de ca. 890 Ma representa, portanto, um limite mínimo para a acresção tectônica do gnaisse Ribeirão às rochas mais jovens da seqüência de Arenópolis. Os dados sugerem que esse evento foi precoce na evolução da seqüência vulcano-sedimentar de Arenópolis, provavelmente entre ca. 920 e 890 Ma.

Márcio M. Pimentel

2003-09-01

268

Vertical structure of a caldera-filling pyroclastics and post-caldera granitic sill: the Middle Miocene Kumano Acidic Rocks emplaced in the Paleogene Shimanto accretionary complex, Japan  

Science.gov (United States)

A 600m all-core drilling penetrated a volcano-plutonic complex associated with middle Miocene Kumano caldera, Kii Peninsula, Southwest Japan. It shows us the vertical cross section of the caldera-filling pyroclastic deposit and granitic sill intruded inside the caldera. The drilling site is located in the southern rim of the north body of Kumano igneous complex. The drilling core consists of the granite porphyry intrusion (Kumano Granite Porphyry) in the upper part (from surface to 464.3 m depth) and the welded tuff (Owase-Shirahama Pyroclastic Rocks) beneath them (464.3 and 600 m depth), which are associated with the caldera formation. The welded tuff in the core sample consists mainly of well-sorted coarse-grained volcanic ash of crystal fragments and lithic fragments. Subordinate amount of pumice fragment more than 10 cm across are scattered. Though most part of the welded tuff in the core sample is massive as observed in the surface outcrops, some parts show remarkable bedding structure. These structural characters suggest that the welded tuff is a pile of many flow units with several 10s meters thick each, which consists of basal pumice-concentrated bed, main massive tuff, and upper bedding part. The lower intrusion boundary of the Kumano Granite Porphyry is exposed at 464.3 m deep, where the granite porphyry intrudes into the host welded tuff with about 10 m thick chilled margin, in which the granite porphyry has very-fine groundmass. The groundmass texture of the granite porphyry shows systematic variation with the distance from the intrusion contact. Within about 20 m from the contact, the groundmass consists of very-fine crystals and entirely shows volcanic rock texture. For 150 m above them, the groundmass consists mainly of quartz and plagioclase and shows equigranular texture. In the upper part (less than 300m deep), the groundmass shows graphic texture with quartz and alkali feldspar. The vertical variation of the groundmass texture indicates upward migration of interstitial vapor-rich fluid during the cooling of the sill from its basement. Mineralogically and geochemically, the Kumano Granite Porphyry is nearly homogeneous. The size and contents of phenocryst is almost constant through the drilling core sample. A lot of metasedimentary xenoliths and mafic magmatic enclaves are included in the Kumano Granite Porphyry. The mafic enclave consists mainly of porphyritic tonalite and quartz diorites. Gabbro is rare. The metasedimentary xenolith consists of pelitic-psammitic gneisses and nearly unmetamorphosed mud- and siltstones. Xenocrysts of cordierite, andalusite and garnet are observed. The Kumano Acidic Rock and other Miocene acidic rocks in Southwest Japan are generated with a near-trench magmatism due to the subduction of a young hot Philippine Sea plate beneath the Southwest Japan arc. The S-type-like mineralogy and rather enriched isotopic character of the Kumano Acidic Rocks imply a magma source involving the component of the Shimanto accretionary complex. Displacement of the basement of volcanic tuff layer suggests a subsidence of caldera floor during the igneous activity. At the bottom of the drill hole, about 500 m below sea level, the basement of the tuff layer did not expose, whereas basement of the tuff layer distributes almost flat at the ground surface 2 - 3 km south of the well about 400 -500 m a.s.l.. This relationship indicates more than 1000 m of vertical displacement of the tuff layer between these two areas. This displacement could be explained by the existence of caldera wall between two areas, which associates the eruption of the welded tuff. No remarkable deformation is observed in the Kumano Granite Porphyry. The Kumano Granite Porphyry is a post-caldera intrusion possibly associated with the caldera resurgent activity.

Nakajima, T.; Geshi, N.; Oikawa, T.; Shinjoe, H.; Miura, D.; Koizumi, N.

2009-04-01

269

Fluid inclusion planes and paleofluid records in the Podlesí granite, Krušné hory Mts., Czech Republic  

Directory of Open Access Journals (Sweden)

Full Text Available Three generations of fluid inclusion planes (FIP were distinguished in rocks of the PTP-3 borehole from the Podlesí granite stock (Krušné hory Mts.. The oldest generation of FIP is believed to have followed the propagation of proto-tectonic subhorizontal aplite dykes and steep veinlets of greisen mineralization, at temperatures of about 400 °C and pressures less than 100 MPa. The later FIP contain fluid inclusions with homogenization temperatures from 140 to 270 °C, and likely represent hydrothermal fluids associated with the repeated opening of fractures during the late stages of intrusive complex development.

Dobeš P

2005-06-01

270

Zircon Recycling in Arc Intrusions  

Science.gov (United States)

Recycling of zircon has been well established in arc intrusions and arc volcanoes, but a better understanding of where and how zircons are recycled can help illuminate how arc magma systems are constructed. To that end, we are conducting age, trace element (including Ti-in-zircon temperatures; TzrnTi) and isotopic studies of zircons from the Late Cretaceous (95-85 Ma) Tuolumne Intrusive Suite (TIS) in the Sierra Nevada Batholith (CA). Within the TIS zircons inherited from ancient basement sources and/or distinctly older host rocks are uncommon, but recycled zircon antecrysts from earlier periods of TIS-related magmatism are common and conspicuous in the inner and two most voluminous units of the TIS, the Half Dome and Cathedral Peak Granodiorites. All TIS units have low bulk Zr ([Zr]825°C), [Zr] in the TIS is a factor of 2 to 3 lower than saturation values. Low [Zr] in TIS rocks might be attributed to a very limited supply of zircon in the source, by disequilibrium melting and rapid melt extraction [1], by melting reactions involving formation of other phases that can incorporate appreciable Zr [2], or by removal of zircon at an earlier stage of magma evolution. Based on a preliminary compilation of literature data, low [Zr] is common to Late Cretaceous N.A. Cordilleran granodioritic/tonalitic intrusions (typically Lake Intrusive Suite (BLIS) in the San Bernardino Mountains (CA), is especially illuminating. Like the TIS the BLIS zircons also have low TzrnTi values (at or below Tzrnsat). However, unlike in the TIS, inherited zircons (or zircon cores) are common (BLIS is intruded into Paleoproterozoic basement). This comparison suggests that lack of abundant inherited or xenocrystic zircon in TIS rocks may be a function of whether they are in high abundance in the melt source or host rocks rather than strong initial undersaturation, and that low [Zr] might reflect melting at temperatures below biotite or amphibole dehydration. The high abundance of zircons with low TzrnTi could also reflect low anatectic temperatures as intermediate-felsic magmas that are initially undersaturated should be dominated by zircons with TzrnTi > Tzrnsat [3]. A corollary is that slightly older zircon antecrysts that are common in the inner units of the TIS could be considered inherited if they are derived from remelting of slightly older intrusions. Remelting at such low temperatures in the arc would require a source of external water. Refs: [1] Sawyer, J.Pet 32:701-738; [2] Fraser et al, Geology 25:607-610; [3] Harrison et al, Geology 35:635- 638

Miller, J.; Barth, A.; Matzel, J.; Wooden, J.; Burgess, S.

2008-12-01

271

The GRANIT project: Status and Perspectives  

CERN Document Server

The GRANIT project is the follow-up of the pioneering experiments that first observed the quantum states of neutrons trapped in the earth's gravitational field at the Institute Laue Langevin (ILL). Due to the weakness of the gravitational force, these quantum states exhibit most unusual properties: peV energies and spatial extensions of order 10 $\\mu$m. Whereas the first series of observations aimed at measuring the properties of the wave functions, the GRANIT experiment will induce resonant transitions between states thus accessing to spectroscopic measurements. After a brief reminder of achieved results, the principle and the status of the experiment, presently under commissioning at the ILL, will be given. In the second part, we will discuss the potential of GRANIT to search for new physics, in particular to a modified Newton law in the micrometer range.

ler, Stephan Baeß; Grigorieva, Ludmilla; Kreuz, Michael; Naraghi, Fabrice; Nesvizhevsky, Valery; Pignol, Guillaume; Protassov, Konstantin; Rebreyend, Dominique; Vezzu, Francis; Voronin, Alexei

2012-01-01

272

Granite Sludge Reuse in Mortar and Concrete  

Directory of Open Access Journals (Sweden)

Full Text Available The disposal of solid wastes produced in granite industry to the environment without any treatment cause not only economical but also serious environmental problems. In this study Granite Powder (GP which produced as solid waste from the cutting and polishing of granite rocks was reused as additive to mortar and concrete cement. Incorporation of GP in mortar and concrete in ratios of 10, 20, 30 wt.% improved mortar and concrete compressive strengths and the concrete workability. The experimental results show that GP can be used to replace cement or fine aggregate in concrete which provide not only solve an environmental problem by safe disposal of GP but also reduce the stress on the limited natural resources and the cost of concrete production.

Husam D. Al- Hamaiedeh

2013-01-01

273

Retention of Anionic Species on Granite: Influence of Granite Composition - 12129  

International Nuclear Information System (INIS)

Technetium (Tc-99, T1/2 = 2.1.105 yrs) and selenium (Se-79, T1/2 = 6.5.104 yrs) belong among fission products, being produced by fission of nuclear fuel. Both elements can significantly contribute to risk due to their complicated chemistry, long life times, high mobility and prevailing anionic character. Therefore, knowledge of migration behaviour under different conditions can significantly improve input into performance and safety assessment models. Granite is considered as a potential host rock for deep geological disposal of radioactive waste in many countries. Granitic rocks consist usually of quartz, feldspar, plagioclase (main components), mica, chlorite, kaolinite (minor components). The main feature of the rock is advection governed transport in fractures, complemented with diffusion process from fracture towards undisturbed rock matrix. The presented work is focused on interaction of anionic species (TcO4-, SeO42-, SeO32-) with granitic rock. Furthermore, the importance of mineral composition on sorption of anionic species was also studied. The batch sorption experiments were conducted on the crushed granite from Bohemian Massive. Five fractions with defined grain size were used for static batch method. Mineral composition of each granitic fraction was evaluated using X-ray diffraction. The results showed differences in composition of granitic fractions, even though originating from one homogenized material. Sorption experiments showed influence of granite composition on adsorption of both TcO4- and SeO32- on granitic rock. Generally, Se(IV) showed higher retention than Tc(VII). Se(VI) was not almost sorbed at all. Fe containing minerals are pronounced as a selective Se and Tc sorbent, being reduced on their surface. As micas in granite are usually enriched in Fe, increased sorption of anionic species onto mica enriched fractions can be explained by this reason. On the other hand, fractions enriched in feldspar did not show increased sorption affinity to Tc and Se. (authors)

274

Wireless Intrusion Detection and Logging System  

Directory of Open Access Journals (Sweden)

Full Text Available Intrusion detection is the security patrol, and become the eyes and ears of the network, alerting the potential vulnerabilities and intrusion attempts. Monitoring can help to spot problems in the network, as well as identify performance problems, but watching every second of traffic that passes through the network, manually searching for attacks, would be impossible. This is why there is need of specialized network intrusion detection software. This software inspects all network traffic, looking for potential attacks and intrusions. Wireless Intrusion Detection System (WIDS is wireless network sniffing tool. It is used for securing the WLAN. And it generates the alarms to the administrator as soon as something goes wrong in the WLAN.WIDS attempts to identify computers system, network intrusions and misuse by gathering and analyzing data.WIDS can monitor and analyze user and system activities. It generates the alerts based either on predefined signatures or on anomalies in the traffic.

SURAJ KENDHEY

2013-03-01

275

Fracture toughness of Stripa granite cores  

International Nuclear Information System (INIS)

Fracture parameters of rock material are of interest in the field of radioactive waste disposal in geologic formations. The paper concerns the measurement of fracture toughness of Stripa granite cores, and focuses on the specimen size requirements. The test procedures presented are for producing representative plane strain fracture toughness values in stress intensity terms. The three round specimen configurations used were a notched beam bend specimen, a round compact specimen and a short rod. Fracture toughness data obtained from compact tension tests, short rod tests and three point bend tests, on Stripa granite are presented in tabular form. (UK)

276

Fracture toughness of Stripa granite cores  

Energy Technology Data Exchange (ETDEWEB)

Fracture parameters of rock material are of interest in the field of radioactive waste disposal in geologic formations. The paper concerns the measurement of fracture toughness of Stripa granite cores, and focuses on the specimen size requirements. The test procedures presented are for producing representative plane strain fracture toughness values in stress intensity terms. The three round specimen configurations used were a notched beam bend specimen, a round compact specimen and a short rod. Fracture toughness data obtained from compact tension tests, short rod tests and three point bend tests, on Stripa granite are presented in tabular form.

Sun, Z.; Ouchterlony, F.

1986-12-01

277

The Younger Dryas age of the Salpausselkä moraines in Finland  

OpenAIRE

The late-glacial Younger Dryas Stadial, as defined over seventy years ago in Denmark, was compared with the withdrawal of the Scandinavian ice sheet and correlated in Finland in 1951 with the formation of the Salpausselkä moraines. Since then a great number of studies of Younger Dryas has eventually led to its definition in the Event Stratigraphy for the North Atlantic region, based on the oxygen isotope stratigraphy in the Greenland ice-core NGRIP. The age of the Younger Dryas / Preboreal b...

Joakim Donner

2010-01-01

278

Integrated Intrusion Detection System Using Soft Computing  

OpenAIRE

Intrusion Detection systems are increasingly a key part of system defense. Various approaches to Intrusion Detection are currently being used but they are relatively ineffective. Among the several soft computing paradigms, we investigated genetic algorithms and neural networks to model fast and efficient Intrusion Detection Systems. With the feature selection process proposed it is possible to reduce the number of input features significantly which is very important due to the fact that the...

Selvakani Kandeeban, S.; Rajesh, Rengan S.

2010-01-01

279

Strengthening intrusion detection techniques through emerging patterns  

OpenAIRE

In todays world where nearly every company is dependent on the Internet to survive, it is not surprising that the role of intrusion detection has become extremely important within the last decade. Intrusion detection involves determining whether some entity has attempted to gain, or worse, it has gained unauthorized access to the system. The task of current intrusion detection systems is detect possible threats not only from insiders but also from outsiders. Based on our current knowledge,...

Grandinetti, Walter M.

2004-01-01

280

Identification of Granite Varieties from Colour Spectrum Data  

OpenAIRE

The granite processing sector of the northwest of Spain handles many varieties of granite with specific technical and aesthetic properties that command different prices in the natural stone market. Hence, correct granite identification and classification from the outset of processing to the end-product stage optimizes the management and control of stocks of granite slabs and tiles and facilitates the operation of traceability systems. We describe a methodology for automatically identifying gr...

José Antonio Vilán; Javier Martínez; Celestino Ordóñez; María Araújo

2010-01-01

281

Behaviour of three different types of granite under forced alteration  

OpenAIRE

The effect of salt crystallization inside the porous networkof three types of granitic rocks has been studied. Specimen of Grey Granite, Ochre Granite and red/White Granite have been submitted to salt crystallization treatments, following the standard and modified procedures, The decay degree reached is different in each type of stone, according to their petrophysical properties. A surface stone decay is found first when following the standard procedure; the modified procedure leads to a l...

Trujillano, Raquel; In?igo, A. C.; Rives, V.; Vicente Herna?ndez, M. A.

1996-01-01

282

Rare metal granites and related rocks of the Ukrainian shield  

OpenAIRE

Two rare metal leucocratic granites, Perga and Kamennaya complexes, can be distinquished on the Ukrainian shield. The Perga complex consists of medium- and coarse grained, mainly porphyric, biotite, riebeckite and aegirine granites, granite porphyries, microclinites and albitites with rare metal mineralization (genthelvite, phenacite, tantalite, cassiterite and wolframite etc.). Granites from several stocks (up to 30 km2) in the northwestern part of the shield, situated along the fracture zon...

Esipchuk, K. Ye; Sheremet, Ye M.; Sveshnikov, K. I.

1993-01-01

283

Accretionary history of the Altai-Mongolian terrane: perspectives from granitic zircon U-Pb and Hf-isotope data  

Science.gov (United States)

The Central Asian Orogenic Belt (CAOB) consists of many tectonic terranes with distinct origin and complicated evolutionary history. Understanding of individual block is crucial to reconstruct the geodynamic history of the gigantic accetionary collage. This study presents zircon U-Pb ages and Hf isotopes for the granitoid rocks in the Russian Altai mountain range (including Gorny Altai, Altai-Mongolian terrane and CTUS suture zone between them), in order to clarify the timing of granitic magmatism, source nature, continental crustal growth and tectonic evolution. Our dating results suggest that granitic magmatism of the Russian Altai mountain range occurred in three major episodes including 445~429 Ma, 410~360 Ma and ~241 Ma. Most of the zircons within the Paleozoic granitoids present comparable positive ?Hf(t) values and Neoproterozoic crustal model ages, which favor the interpretation that the juvenile crustal materials produced in the early stage of CAOB were probably dominant sources for the Paleozoic magmatism in the region. The inference is also supported by widespread occurrence of short-lived juvenile materials including ophiolites, seamount relics and arc assemblages in the north CAOB. Consequently, the Paleozoic massive granitic rocks maybe not represent continental crustal growth at the time when they were emplaced, but rather record reworking of relatively juvenile Proterozoic crustal rocks although mantle-derived mafic magma was possibly involved to sever as heat engine during granitic magma generation. The Early Triassic granitic intrusion may be product in an intra-plate environment, as the case of same type rocks in the adjacent areas. The positive ?Hf(t) values (1.81~7.47) and corresponding Hf model ages (0.80~1.16 Ga) together with evidence of petrology are consistent with the interpretation that the parental magma of the Triassic granitic intrusion was produced from enriched mantle-derived sources under an usually high temperature condition which is likely due to basaltic magma that underplated the lower crust. Our data combined with evidence of the regional geology enable us to conclude that the Gorny Altai and Altai-Mongolian terranes possibly have similar tectonic natures, but represent two separate accretionary systems before Devonian collision. The accretion and amalgamation processes resulted in the Paleozoic granitoid magmatism and caused the two terranes to merge as a composite tectonic domain at the Siberian continental margin.

Cai, Keda; Sun, Min; Xiao, Wenjiao

2014-05-01

284

Interaction between magmatic and tectonic stresses during dyke intrusion Interacción entre esfuerzos magmáticos y tectónicos durante la intrusión de diques  

OpenAIRE

Cataclastic and mylonitic rocks exposed in the southwestern part of the Peninsula de Mejillones, northern Chile, are intruded at high angles of the foliation by younger, steeply inclined (±70°) basaltic dykes that resemble intrusive tension gashes with knife-edge contacts with the country rocks. These late dykes developed sigmoidaly-shaped, preferred orientation paths defined by oriented pyroxene phenocrysts that vary in size, aspect ratio, concentration and distribution across the width of...

Jorge Skarmeta

2011-01-01

285

Zircon geochronology of Berach granite of Chittorgarh, Rajasthan  

International Nuclear Information System (INIS)

Discordant ages of zircons from Berach granite suggest that this granite crystallized around 2610 m.y. ago and lost lead during an episodic event around 710 m.y. The 710 m.y. date probably reflects a response to a regional thermal event also recorded in the 730 m.y. zircon age for the Mt. Abu 'Erinpura type' granite. (author)

286

Geoquímica e geocronologia U-Pb (SHRIMP) de granitos da região de Peixoto de Azevedo: Província Aurífera Alta Floresta, Mato Grosso / Geochemistry and geochronology U-Pb Shrimp of granites from Peixoto de Azevedo: Alta Floresta Gold Province  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese A análise de dados petrográficos, geoquímicos e geocronológicos de granitos do Domínio Peixoto de Azevedo, Mato Grosso, na porção leste da Província Aurífera Alta Floresta, conduziu ao reconhecimento de dois corpos graníticos limitados por grandes falhamentos e zonas de cisalhamento regionais. Na po [...] rção noroeste ocorre biotita granodiorito de granulação grossa, textura inequigranular a porfirítica, metaluminoso à peraluminoso, calcialcalino de alto potássio e magnesiano. Na porção sudeste da área ocorre um biotita monzogranito de granulação grossa, textura equigranular a porfiritica, levemente peraluminoso, calcialcalino de alto potássio e caráter dominantemente ferroso. Datações U-Pb (SHRIMP) mostraram que o biotita monzogranito apresenta uma idade de 1869 ± 10 Ma, similar à Suíte Intrusiva Matupá, enquanto que o biotita granodiorito apresenta idade de 1781 ± 10 Ma, que é a idade esperada para o Granito Peixoto. As duas unidades mostram padrões de elementos terras raras com enriquecimento de leves sobre pesados e anomalia negativa de Eu (LaN/YbN " 7,6 a 17,31 e Eu/Eu* entre 0,46 - 0,72 para o biotita monzogranito e LaN/YbN " 7,13 a 29,09 com razões Eu/Eu* entre 0,25 - 0,40 para o biotita granodiorito). O padrão dos elementos traço para ambos apresenta anomalias negativas de Ba, P, Ti e Nb, indicando uma evolução por fracionamento mineral e associação com fontes modificadas por subducção e envolvimento crustal. Neste trabalho, sugere-se que o monzogranito Matupá foi gerado em ambiente de margem continental ativa, num estágio maduro. Para o biotita-granodiorito Peixoto, duas hipóteses são sugeridas: (a) formação num ambiente de arco magmático mais jovem associado ao Magmatismo Colíder ou (b) gerado em ambiente extensional, relacionado à quebra do efêmero Supercontiente Columbia. Abstract in english The analysis of petrographic, geochemical and geochronological data of granites in the Peixoto de Azevedo region, Mato Grosso, Brazil, in the eastern portion of the Alta Floresta Gold Province, led to the recognition of two granitic bodies bounded by regional major faults and shear zones. In the nor [...] thwestern portion a body with featured as biotite granodiorite, coarse-grained, with porphyritic to inequigranular texture, metaluminous to peraluminous, high-K calc-alkaline and magnesium character. In the southeastern portion of the area, a biotite monzogranite coarse-grained, with equigranular to porphyritic texture, slightly peraluminous, high-K calc-alkaline and dominantly of ferrous character. U- Pb dating (SHRIMP) showed that the biotite monzogranite has an age of 1869 ± 10 Ma, similar to the Matupá Intrusive Suite, while the biotite granodiorite has an age of 1781 ± 10 Ma, that is the age expected to Peixoto Granite. Both units show patterns of rare earth elements with enrichment of light over heavy and negative Eu anomaly (LaN/YbN " 7.6 to 17.31 and ratios Eu/Eu* between 0.46 - 0.72 for biotite monzogranite and LaN/YbN " 7.13 to 29.09 with ratios Eu/Eu* between 0.25 - 0.40 for the biotite granodiorite). Trace elements pattern for both present negative anomalies of Ba, P, Ti and Nb indicating an evolution from mineral fractionation and subduction related sources. In this paper, it is sugested that the monzogranite Matupá was developed in mature arc tectonic environment. For the Peixoto Granite, two hypotheses are suggested: (a) it was developed in younger magmatic arc environment associated with the Colider Magmatism or (b) it was generated in extentional tectonic environment during the Columbia Supercontinent break up.

Fernanda Rodrigues da, Silva; Márcia Aparecida Sant' Ana, Barros; Ronaldo, Pierosan; Francisco Edígio Cavalcante, Pinho; Mara Luiza Barros Pita, Rocha; Bruno Rodrigo, Vasconcelos; Samantha Evelyn Max, Dezula; Carla, Tavares; Jhonattan, Rocha.

2014-09-01

287

Early Precambrian crustal evolution in Eastern India: The ages of the Singhbhum granite and included remnants of older gneiss  

Science.gov (United States)

Geochronology of samples from the Indian Shield was discussed. New Sm-Nd data was given for the Singhbhum granite, which give model ages (T sub DM of 3.36 to 3.40 Ga, essentially equivalent to ages of included gneissic remnants of the older metamorphic group (OMG) (T sub DM = 3.35 to 3.41 Ga). Lead-lead and Rb-Sr ages of the granite and OMG range between 3.28 to 3.38 Ga. These results are considerably younger than the 3775 + or - 89 Ma Sm-Nd isochron of Basu et al., which Taylor and colleagues interpret as an artifact caused by regressing two suites of unrelated rock samples.

Moorbath, Stephen; Taylor, Paul N.

288

Uncoupled O and Hf isotopic systems in zircon from the contrasting granite suites of the New England Orogen, eastern Australia: Implications for studies of Phanerozoic magma genesis  

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The Permo-Triassic granites of the New England Orogen, eastern Australia, were emplaced into a volcanic arc complex accreted to the eastern Gondwana margin in the Late Devonian or Early Carboniferous. Zircon U-Pb dating shows that the S-type Hillgrove (?297 Ma) and Bundarra (?287 Ma) Supersuites predated intrusion of the I-type Moonbi Supersuite (?250 Ma) by up to 50 Ma. The high ?18Ozrn of the S-type granites (10.0-11.5‰), and range of U-Pb ages (?370-300 Ma) and ?18Ozrn (?5-10‰) of their inherited zircon cores, show that their source rocks were predominantly weathered Carboniferous volcaniclastics, the youngest deposited < 25 Ma before the granites were emplaced. In contrast, the lower ?18Ozrn (6.9-7.8‰) and lack of inheritance in the I-type granites is consistent with a zircon poor, more juvenile source, probably a mafic igneous underplate mixed with a small amount of volcanogenic and/or oceanic sediment. Despite the differences in source materials, the ?Hf(t) values of all granites, both S- and I-type, are similar (+5.0 ± 0.5 cf. +5.9 ± 0.5), consistent with both the mafic and sedimentary components in the granite sources being relatively young and similar in Hf isotopic composition at the time of granite genesis. In young, isotopically juvenile orogens, the O isotopic composition of well-dated igneous and inherited zircon can be a much more sensitive indicator of petrogenetic processes than the zircon Hf isotopic compositions alone.

Jeon, Heejin; Williams, Ian S.; Bennett, Vickie C.

2014-12-01

289

The distribution of radioelements in archaean granites of the Kaapvaal Craton, with implications for the source of uranium in the Witwatersrand Basin  

International Nuclear Information System (INIS)

Approximately 500 samples from the Archaean granitic basement of the southern Kaapvaal Craton have been analysed, for U and Th. When viewed in conjunction with geological relationships, the radioelement distribution patterns in the Archaean basement provide contraints regarding the origin of uranium in the Witwatersrand Basin. Granites in the Baberton region are sub-divided into three magnetic cycles, the earliest cycle comprising tonalite-trondhjemite gneisses, the intermediate cycle comprising literally extensive K-rich batholiths and the final stage consisting of discrete intrusive granitic plutons. Uranium and thorium contents vary as a function of age and rock type, an increase progressively from the first cycle through to the third cycle. Certain of the late granite plutons may have been S-type in origin, have relatively low Th/U ratios, high U contents, and are characterized by accessory minerals dominated by monazite-like phases. The late granite plutons with highest radioelement contents appear to have formed circa 2,8 Ga, an age which coincides with granulite facies metamorphism and uranium-thorium depletion in the lower crust, as recrorded in the Vredeford crustal profile. Uranium has been leached from portions of the regolith profile, but also concentrated into leucoxene-rich zones derived from the breakdown of pre-existing titanium-bearing phases. The widespread development of an uraniferous leucoxene protore in weathered source rocks of the Witwatersrandeathered source rocks of the Witwatersrand Basin has relevance to the genesis of authigenic U-Ti phases (brannerite) in the reefs themselves. The study of radioelement distribution in Archaean granites adjacent to the Witwatersrand Basin provides a framework within which considerations regarding the origin of the uranium deposits in the basin can be viewed. The secular evolution of the Archaean granitic basement, hydrothermal processes, and palaeoweathering all played a role in the formation of the Witwatersrand deposits

290

Subchondral insufficiency fracture of the femoral head in younger adults  

Energy Technology Data Exchange (ETDEWEB)

We report two cases of subchondral insufficiency fracture of the femoral head observed in younger adults without any history of overexertion. In both cases, MRI revealed an irregular, discontinuous low-intensity band on the T1-weighted images. Both patients were treated operatively, and histological examination confirmed the diagnosis of subchondral fracture. A diagnosis of subchondral insufficiency fracture needs to be put in as one of the diagnoses in younger patients with a hip pain. (orig.)

Yamamoto, Takuaki; Nakashima, Yasuharu; Shuto, Toshihide; Jingushi, Seiya; Iwamoto, Yukihide [Graduate School of Medical Sciences, Kyushu University, Department of Orthopaedic Surgery, Fukuoka (Japan)

2007-06-15

291

Subchondral insufficiency fracture of the femoral head in younger adults  

International Nuclear Information System (INIS)

We report two cases of subchondral insufficiency fracture of the femoral head observed in younger adults without any history of overexertion. In both cases, MRI revealed an irregular, discontinuous low-intensity band on the T1-weighted images. Both patients were treated operatively, and histological examination confirmed the diagnosis of subchondral fracture. A diagnosis of subchondral insufficiency fracture needs to be put in as one of the diagnoses in younger patients with a hip pain. (orig.)

292

Learning Dialogue Strategies from Older and Younger Simulated Users  

OpenAIRE

Older adults are a challenging user group because their behaviour can be highly variable. To the best of our knowledge, this is the first study where dialogue strategies are learned and evaluated with both simulated younger users and simulated older users. The simulated users were derived from a corpus of interactions with a strict system-initiative spoken dialogue system (SDS). Learning from simulated younger users leads to a policy which is close to one of t...

Kallirroi, Georgila; Wolters, Maria K.; Moore, Johanna D.

2010-01-01

293

Scaling property of ideal granitic sequences  

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Full Text Available Quantification of granite textures and structures using a mathematical model for characterization of granites has been a long-term attempt of mathematical geologists over the past four decades. It is usually difficult to determine the influence of magma properties on mineral crystallization forming fined-grained granites due to its irregular and fine-grained textures. The ideal granite model was originally developed for modeling mineral sequences from first and second-order Markov properties. This paper proposes a new model for quantifying scale invariance properties of mineral clusters and voids observed within mineral sequences. Sequences of the minerals plagioclase, quartz and orthoclase observed under the microscope for 104 aplite samples collected from the Meech Lake area, Gatineau Park, Québec were used for validation of the model. The results show that the multi-scale approaches proposed in this paper may enable quantification of the nature of the randomness of mineral grain distributions. This, in turn, may be related to original properties of the magma.

D. Xu

2007-06-01

294

Granite School District First Grade Reading Study.  

Science.gov (United States)

A comparative study of first-grade reading instructional methods was undertaken with the support of the Granite School District Exemplary Center for Reading Instruction. This study was conducted in 19 schools of the district and involved approximately 1,295 students. Nine hypotheses concerning the various approaches used in reading instruction…

Castner, Myra H.; And Others

295

The geology and petrogenesis of the southern closepet granite  

Science.gov (United States)

The Archaean Closepet Granite is a polyphase body intruding the Peninsular Gneiss Complex and the associated supracrustal rocks. The granite out-crop runs for nearly 500 km with an approximate width of 20 to 25 km and cut across the regional metamorphic structure passing from granulite facies in the South and green schist facies in the north. In the amphibolite-granulite facies transition zone the granite is intimately mixed with migmatites and charnockite. Field observations suggests that anatexis of Peninsular gneisses led to the formation of granite melt, and there is a space relationship between migmatite formation, charnockite development and production and emplacement of granite magma. Based on texture and cross cutting relationships four major granite phases are recognized: (1) Pyroxene bearing dark grey granite; (2) Porphyritec granite; (3) Equigranular grey granite; and (4) Equigranular pink granite. The granite is medium to coarse grained and exhibit hypidiomorphic granular to porphyritic texture. The modal composition varies from granite granodiorite to quartz monzonite. Geochemical variation of the granite suite is consistent with either fractional crystallization or partial melting, but in both the cases biotite plus feldspar must be involved as fractionating or residual phases during melting to account trace element chemistry. The trace element data has been plotted on discriminant diagrams, where majority of samples plot in volcanic arc and within plate, tectonic environments. The granite show distinct REE patterns with variable total REE content. The REE patterns and overall abundances suggests that the granite suite represents a product of partial melting of crustal source in which fractional crystallization operated in a limited number of cases.

Jayananda, M.; Mahabaleswar, B.; Oak, K. A.; Friend, C. R. L.

1988-01-01

296

Geochronological (Rb-Sr and Sm-Nd) studies on intrusive gabbro and dolerite dykes from parts of Northern and Central Indian cratons: implications for the age of onset of sedimentation in Bijawar and Chattisgarh basins and uranium mineralisation  

International Nuclear Information System (INIS)

The Dargawan gabbros intrusive into the Moli Subgroup of Bijawar Group, yielded Rb-Sr whole rock isochron age of 1967 ± 140 Ma. Based on the oldest age from overlying Lower Vindhyan (1.6 Ga) and the underlying youngest basement ages (2.2 Ga), the time range of Bijawar sedimentation may be assigned as 2.1-1.6 Ga (Paleoproterozoic). Sm-Nd Model ages (TDM), obtained, for Dargawan gabbros, is c. 2876-3145 Ma. High initial 87Sr/86Sr ratio of 0.70451 (higher than the contemporary mantle) and negative ?Ndi (at 1.9 Ga) value of -1.5 to - 4.5, indicate assimilation of Archaean lower crustal component by the enriched mantle source magma at the time of gabbroic intrusion. The dolerite, from Damdama area, which is intrusive into the basement and overlying sediments of Chandrapur Group in the central Indian craton, yielded Rb-Sr internal isochron age of 1641 ± 120 Ma. The high initial 87Sr/86Sr ratio of 0.7098 and ?Ndi value of -3.5 to -3.7 (at 1.6 Ga) is due to contamination of the mantle source magma with the overlying sediments. These dolerites have younger Sm-Nd Model ages (TDM) than Dargawan gabbros as c. 2462-2675 Ma, which is similar to the age of the Sambalpur granite, from which probably sediments to this part of Chattisgarh basin are derived. Hence mixing of sediments with the Damdama dyke during its emplacement, gives rise to high initial 87Sr/86Sr and low ip>87Sr/86Sr and low initial 143Nd/144 ratios for these dykes. The c. 1600 Ma age indicates minimum age of onset of the sedimentation in the Chandrapur Group of Chattisgarh basin. Both the above mafic intrusions might have taken place in an intracratonic rift related (anorogenic) tectonic setting. This study is the first reliable age report on the onset of sedimentation in the Chandrapur Group. The total minimum time span of Chandrapur and Raipur Group may be 1.6 Ga to 1.0 Ga (Mesoproterozoic). The unconformably underlying Shingora Group of rocks of Chattisgarh Supergroup thus indicates Paleoproterozoic age (older than 1.6 Ga). Most part of the recently classified Chattisgarh Supergroup and Bijawar-Vindhyan sequence are of Mesoproterozoic-Paleoproterozoic age and not of Neoproterozoic-Mesoproterozoic age as considered earlier. Petrographic study of basic dykes from Damdama area (eastern margin of Chattisgarh Supergroup) indicated presence of primary uranium mineral brannerite associated with goethite. This is the evidence of mafic intrusive providing geotherm and helping in scavenging the uranium from the surrounding and later alterations causing remobilisation and reconcentration of pre-existing uranium in host rocks as well as in mafic dyke itself otherwise mafic rocks are poor source of uranium and can not have primary uranium minerals initially. It can be concluded that mafic dykes have role in uranium mineralisation although indirectly. (author)

297

Gamma radiation measurements in Brazilian commercial granites  

International Nuclear Information System (INIS)

Full text of publication follows: Gamma radiation from radionuclides which are characterized by half lives comparable to the age of the earth, such as 40 K and the radionuclides from the 238 U and 232 Th series, and their decay products, represent the main terrestrial source of irradiation to the human body. Their concentrations vary for different types of rocks, where high radiation levels are associated with igneous rocks such as granite. Thorium, uranium and potassium concentrations of granitic rocks are intimately related to their mineral compositions and general petrologic features. Then, these features associated with effects of weathering and metamorphism produce expressive alterations in the relationship between the natural radionuclides (Th, U, K, Th/U and Th/K). Consequently, the measurements of thorium, uranium, and potassium concentrations of different granite samples result on individual differentiation sequences. From the 232 Th, 238 U and 40 K activity concentrations obtained for each sample, it is possible to evaluate their respective dose rates in air, when these stones are used as tiling rocks. These results are of great interest in the environmental radiological protection study, since granites are widely used as building and ornamental materials, including as indoor covering. In this way, the Laboratory of Radioecology (L.A.R.A.) of the Physics Institute of the Universidade Federal Fluminense (I.F. -U.F.F.) has been performing analyzes on more than has been performing analyzes on more than one hundred differ ent types of the main Brazilian commercial granites in last two years [1]. Using NaI and HP Ge gamma-ray spectrometers to determine the concentration of natural radionuclides in these samples, the annual effective dose rates and the gamma activity concentration index have been evaluated and compared to the limits proposed by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) and European Commission (E.C.). In addition, the correlations between thorium, uranium and potassium have been obtained with the aim of correlating the petrographic characteristics of commercial granites with their corresponding dose rates for natural radioactivity. Our results show, contrary to what some works have reported in international literature, that the Brazilian granites are not composed by minerals which could produce high levels of dose rates when used as covering material. (authors)

298

Nature and origin of Proterozoic A-type granitic magmatism in the southwestern United States of America  

Science.gov (United States)

The mountain ranges of Arizona and adjacent California and Nevada contain large areas underlain by Proterozoic anorogenic granites comprising the southwesternmost portion of a transcontinental belt of 1.4-1.5-Ga-old anorogenic complexes that extends across North America northeast into Labrador. Of these, a two-mica, monazite-bearing granitic suite resides in central and southeastern Arizona as part of a peraluminous subprovince that is bordered on the south (southern Arizona to Sonora) and west (western Arizona and adjacent portions of California and Nevada) by marginally metaluminous granites bearing biotite-sphene ± hornblende and fluorite. All of these 1.4-Ga granites are distinctly more potassic, iron-enriched (relative to Mg), and depleted in Ca, Mg and Sr in contrast to typical orogenic granitoids. In general, the large-ion lithophile-element enriched composition is a consequence of limited melting of a water-deficient crustal source at depths greater than 25-37 km. For the peraluminous granites, this contrast is less extreme, perhaps resulting from a larger degree of melting as a consequence of a greater metasedimentary component and water in its crustal source. The anorogenic granitic magmas intruded into the upper crust at depths of 8-17 km or shallower at temperatures up to 790°C. The most dramatic variation in the crystallization-intensive parameters resides in the oxygen fugacity, which spans three orders of magnitude. Relative to other anorogenic suites, all of the magmas crystallized at elevated levels of ƒ O 2 as reflected in their assignment to the anorogenic magnetite series. Yet a regionally significant rise in primary ƒ O 2 levels, unmatched elsewhere in the transcontinental belt, occurs for plutons in western Arizona, including the Holy Moses and Hualapai granites. The most extreme case is the Hualapai granite whose biotite {Fe}/{( Fe + Mg)} ratios drop (due to high ƒ O 2) to a low of 0.27, down from more typical levels of 0.54 to 0.75. Such extreme variations in primary levels of oxygen fugacity must be an indirect imprint of regional changes of the level of oxidation of the lower crust. The high-f O 2 Holy Moses and Hualapai plutons have intruded near the regional boundary between the metaluminous and peraluminous granites and appear to be imaging a major change in the level of oxidation of the lower crust. This boundary is also approximately equivalent to significant changes in the Nd and Pb isotopic compositions of these granites and the metamorphic and magmatic character of the older orogenic terrane. On a global scale, the crust-forming orogenies ended by 1.6 Ga ago and the continents entered a long-lived era dominated by localized extension and transcontinental intrusion of anorogenic potassic rapakivi granite, mafic dike swarms, charnockite and anorthosite. The absence of orogenic deformation implies that plate consumption became intraoceanic during this time. The profuse and widespread nature of the igneous activity has no Phanerozoic analogue and is considered to be unique to the Proterozoic. A crustal overturn model ties the magmatism to heating within a largely undepleted subcontinental mantle, the eventual rise of mantle plumes, and the transfer of heat into the youthful, undifferentiated Proterozoic crust. Subsequent melting and rise of potassic granitic magmas from the lower crust leads to considerable crustal reorganization, a process that would continue until both the mantle and crust reached a stable configuration.

Anderson, J. Lawford; Bender, E. Erik

1989-06-01

299

Identification of Granite Varieties from Colour Spectrum Data  

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Full Text Available The granite processing sector of the northwest of Spain handles many varieties of granite with specific technical and aesthetic properties that command different prices in the natural stone market. Hence, correct granite identification and classification from the outset of processing to the end-product stage optimizes the management and control of stocks of granite slabs and tiles and facilitates the operation of traceability systems. We describe a methodology for automatically identifying granite varieties by processing spectral information captured by a spectrophotometer at various stages of processing using functional machine learning techniques.

José Antonio Vilán

2010-09-01

300

Ragnar Granit 100 years--memories and reflections.  

Science.gov (United States)

The Swedish-Finnish Nobel laureate Ragnar Granit, born 100 years ago, is commemorated in a brief article by one of his former PhD students and collaborators. After a short account of Granit's life and scientific career, special attention is given to Granit's role as a teacher in research training and his published thoughts on this matter, partly reflecting Granit's own experience as a "postdoc" in the laboratory of Sherrington (Oxford). The article includes personal recollections of how it was to work together with Granit in his laboratory. PMID:11232369

Kernell, D

2000-12-01

301

Assessment of radiological hazard of commercial granites from Extremadura (Spain).  

Science.gov (United States)

The term "commercial granite" comprises different natural stones with different mineralogical components. In Extremadura, western Spain, "commercial granites" can be classified in three types: granite s.s. (sensus stricti), granodiorite, and diorite. The content of naturally occurring radionuclides depended of the mineralogy. Thus, the (40)K content increased as the relative content of alkaline feldspar increased but decreased as the plagioclase content increased. The radioactive content decreased in the following order: granite s.s. > granodiorite > diorite. In this work, the radiological hazard of these granites as building material was analyzed in terms of external irradiation and radon exposure. External irradiation was estimated based on the "I" index, ranged between 0.073 and 1.36. Therefore, these granites can be use as superficial building materials with no restriction. Radon exposure was estimated using the surface exhalation rates in polished granites. The exhalation rate in granites depends of their superficial finishes (different roughness). For distinct mechanical finishes of granite (polish, diamond sawed, bush-hammered and flamed), the surface exhalation rate increased with the roughness of the finishes. Thermal finish presented the highest exhalation rate, because the high temperatures applied to the granite may increase the number of fissures within it. The exhalation rates in polished granites varied from 0.013 to 10.4 Bq m(-2) h(-1). PMID:24583635

Guillén, J; Tejado, J J; Baeza, A; Corbacho, J A; Muñoz, J G

2014-06-01

302

2005 dossier: granite. Tome: phenomenological evolution of the geologic disposal  

International Nuclear Information System (INIS)

This document makes a status of the researches carried out by the French national agency of radioactive wastes (ANDRA) about the phenomenological aspects of the geologic disposal of high-level and long-lived radioactive wastes (HLLL) in granite formations. Content: 1 - introduction: ANDRA's research program on disposal in granitic formation; 2 - the granitic environment: geologic history, French granites; 3 - HLLL wastes and disposal design concepts; 4 - identification, characterization and modeling of a granitic site: approach, geologic modeling, hydrologic and hydro-geochemical modeling, geomechanical and thermal modeling, long-term geologic evolution of a site; 5 - phenomenological evolution of a disposal: main aspects of the evolution of a repository with time, disposal infrastructures, B-type wastes disposal area, C-type wastes disposal area; spent fuels disposal area, radionuclides transfer and retention in the granitic environment; 6 - conclusions: available knowledge, methods and tools for the understanding and modeling of the phenomenological evolution of a granitic disposal site. (J.S.)

303

Efficient Intrusion Detection Scheme based on SVM  

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Full Text Available The network intrusion detection problem is the focus of current academic research. In this paper, we propose to use Support Vector Machine (SVM model to identify and detect the network intrusion problem, and simultaneously introduce a new optimization search method, referred to as Improved Harmony Search (IHS algorithm, to determine the parameters of the SVM model for better classification accuracy. Taking the general mechanism network system of a growing city in China between 2006 and 2012 as the sample, this study divides the mechanism into normal network system and crisis network system according to the harm extent of network intrusion. We consider a crisis network system coupled with two to three normal network systems as paired samples. Experimental results show that SVMs based on IHS have a high prediction accuracy which can perform prediction and classification of network intrusion detection and assist in guarding against network intrusion.

Guangping ZHOU

2013-09-01

304

The Riviera Deposit: Endo-skarn and Vein-hosted W-MO-REE Mineralization in I-type Granites of the Cape Granite Suite, South Africa  

Science.gov (United States)

The blind Riviera deposit is located in the western Cape Province and was discovered by stream sediment sampling in the mid 1970's. Resources total 46 million metric tons assaying 0,216 per cent tungsten and 200 parts per million molybdenum, a marginal grade that has prohibited development into an open cast mine. Mineralization is mainly hosted by granitoids of the Riviera Pluton which intruded the regionally metamorphosed volcano-sedimentary Malmesbury Group. These granitoids form part of the Cape Granite Suite, a series of batholiths and plutons with S-, I- and A-type characteristics. The composite Riviera Pluton comprises a suite of metaluminous to slightly peraluminous granitoids. The rocks least affected by hydrothermal alteration are granodioritic to adamelitic in composition whereas the more altered host rocks include quartz-monzonite, granite and quartz syenite. As a whole the suite is subalkaline to K-calcalkaline and conforms to the characteristics of I-type granites. The pluton was emplaced into a dome-shaped interference structure, late in the Neoproterozoic Saldanian orogenic cycle. Alteration, particularly prevalent in the roof or cupola of the pluton, occurs as zones of pervasive sericitization, argillization, silicification and potassic alteration. Their spatial and temporal relationship is complex and indicates several superimposed alteration events. Wall rocks display limited alteration and have acted as an impermeable cap. The cross-cutting granitoid intrusions produced wall rock xenoliths of various dimensions consisting mainly of meta-carbonates displaying various stages of digestion. Economic concentrations of scheelite are spatially linked to these assimilations, particularly proximal to the wall rock contact. The occurrence of diagnostic minerals such as vesuvianite, hornblende, hedenbergite, grandite garnets define a typical endo-skarn association. Accessory minerals include pyrite, pyrrhotite, chalcopyrite, sphalerite and the LREE enriched mineral allanite. Scheelite and molybdenite occurs as fine disseminations, but also as coarse grains within cross-cutting, late stage quartz and calcite veins in the granite and the wall rocks. No spatial or paragenetic correlation exists between the concentration of tungsten and molybdenum, suggesting that their distribution is related to sequential introduction of multiple magmatic phases and associated mineralizing fluids.

Rozendaal, A.; Moyen, J.

2009-05-01

305

Sr and Nd isotopic characteristics of 1.77-1.58 Ga rift-related granites and volcanics of the Goias tin province, Central Brazil  

International Nuclear Information System (INIS)

Supracrustal rocks of the Arai Group, together with coeval A-type granites represent a ca. 1.77-1.58 Ga old continental rift in Brazil. Two granite families are identified: the older (1.77 Ga) group forms small undeformed plutons, and the younger granites (ca. 1.58 Ga) constitute larger, deformed plutons. Sr-Nd isotopic data for these rocks indicate that the magmatism is mostly produced of re-melting of Paleoproterozoic sialic crust. Initial Sr ratios for both granite families are ca 0.276 and 0.720. Most TDM model ages are between 2.58 and 1.80 Ga. ?Nd (T) values are between +3.6 and -11.9. Arai volcanics are bimodal, with basalts and dacites/rhyolites interlayered with continental sediments. The felsic volcanics show Nd isotopic characteristics which are very similar to the granites, and are also interpreted as reworking of Paleoproterozoic crust. Detrital sediments of the Arai Group revealed TDM model ages between 2.4 and 2.16 Ga., indicating that they are the product of erosion of Paleoproterozoic crust. The data indicate that the Arai rift system was established on crust that had just become stable after the Paleoproterozoic orogeny. (author)

306

Relationships between deformation and magmatism in the Pan-African Kandi Shear Zone: Microstructural and AMS studies of Ediacaran granitoid intrusions in central Bénin (West Africa)  

Science.gov (United States)

Relationships between the metamorphic basement, granitic intrusions and the Kandi Shear Zone (KSZ) in central Bénin have been investigated using petrological and structural approaches, in order to better understand the space and time parameters of the Pan-African shear deformation and the Ediacaran magmatism. In central Bénin, metamorphic rocks from the KSZ display a steep to vertical N-S trending foliation, a sub-horizontal mineral lineation together with kinematic indicators in agreement with a dextral transcurrent mega-shear zone. Four granitic intrusions (Dassa, Tré, Gobada and Tchetti) show many petrological similarities. They are biotite ± amphibole - ilmenite ± magnetite monzogranites with ferrous and metaluminous I-type features derived from high-K calk-alkaline magma. A fifth intrusion (Fita) is an alkali-feldspar, biotite, magnetite and ilmenite bearing granite crystallized from an alkaline magma. Moreover, high K2O, Zr, Y, Nb and low CaO, MgO and Al2O3 contents together with high (FeOt/MgO) and low LIL/HFS elements ratios suggesting an A-type granite affinity. Microstructural and AMS investigations presented in this paper show (i) solid-state deformation evidence for Dassa pluton and (ii) a magmatic deformation for the Tré, Tchetti, Gobada and Fita granitoids. Foliation in Dassa is parallel to the mesoscopic planar mylonitic foliation of the metamorphic basement. In the Tré, Tchetti, Gobada and Fita granitoids, magmatic textures and magnetic fabrics are coherent with the KSZ activity. These data suggest (i) a syn-kinematic nature for most of the intrusions (Tré, Gobada, Tchetti and Fita), except Dassa which correspond to an earlier event (ii) the succession of high-K calk-alkaline (Dassa, Tré, Gobada, Tchetti) evolves toward alkaline magmas (Fita) during the KSZ strike-slip tectonics. These observations highlight the changing nature of magma composition, magmatic processes and the different sources during KSZ activity in the Bénin Nigerian Shield. These new results suggest that the previous geodynamic interpretations, which assume a post-tectonic emplacement for the Gobada intrusion or an active continental margin setting for most of the late Pan-African (Ediacaran) granites intruded in central Bénin, has to be re-examined.

Adissin Glodji, L.; Bascou, J.; Yessoufou, S.; Ménot, R.-P.; Villaros, A.

2014-09-01

307

The Pedregal granite (Portugal: petrographic and geochemical characterization of a peculiar granitoid  

Directory of Open Access Journals (Sweden)

Full Text Available The Pedregal granite outcrops in the Central Iberian Zone, northern Portugal, in the eastern border of a synorogenic variscan granite-migmatite complex sub-concordant with the regional metamorphic structures. It is a granitoid (ca. 3 km2 with an elongated NW-SE shape intruded in staurolite-micaschist and banded gneiss-migmatite rocks, with local igneous breccias in the contact. The country rocks belong to a metapelitic and metasammitic sequence of Edicarian-Cambrian age, known as the “Complexo Xisto-Grauváquico” (CXG which shows a main regional foliation with a NW-SE to NNW-SSE direction. The Pedregal granite is peraluminous (its A/CNK parameter ranges from 1.18 to 1.62, with a magnesian and alkali to alkali-calcic signature. The peculiar features of the granite are high contents of Zr (389 to 435 ppm and a LREE flat pattern, which are uncommon characteristics for granitic rocks, as well as the corroded shape of the biotite, and the large amount of secondary muscovite. These peculiar features distinguish it from the adjacent synorogenic granites. The field, petrographical and chemical features of the Pedregal granite are in accordance with a second phase of partial melting of a residuum, depleted by melt segregation during a first melting episode with the involvement of peritectic garnet and abundant residual biotite with LREE- and Zr-bearing accessory minerals. Besides, the intrusive character of the granite, and the presence of metasedimentary xenoliths point out to a secondary diatexite.El granito de Pedregal aflora en la Zona Centro-Ibérica, en el norte de Portugal, en el borde oriental de un complejo granito-migmatítico sinorogénico varisco, subconcordante con las estructuras metamórficas regionales. Es un granitoide (ca. 3 km2 de forma elongada NW-SE, que intruye en micaesquistos estaurolíticos y en rocas gneissico- migmatíticas bandeadas, con brechas ígneas locales en el contacto. Las rocas encajantes pertenecen a una secuencia metapelítica-metasamítica de edad Ediacariense - Cámbrico, conocida como el “Complejo Esquisto-Grauváquico” (CEG, que muestra una foliación regional principal NW-SE a NNW- SSE. El granito de Pedregal es peralumínico (el parámetro A/CNK oscila desde 1.18 hasta 1.62, con una composición magnesiana, entre alcalina y alcalino-cálcica. Sus características peculiares son el alto contenido de Zr (389–435 ppm y de tierras raras ligeras (LREE que presentan un patrón plano, la forma corroída de la biotita, y la gran cantidad de moscovita secundaria. Estas características peculiares lo distinguen de los otros granitos sinorogénicos adyacentes. Las características de campo, petrográficas y químicas del granito de Pedregal parecen apuntar a una segunda fase de fusión parcial de un residuo, empobrecido por la segregación de fundido durante una primera fase de fusión con participación de granate peritéctico y abundante biotita residual con minerales accesorios portadores de LREE y Zr. Además, el carácter intrusivo del granito, y la presencia de xenolitos metasedimentarios sugieren una diatexita secundaria.

Ferreira, J. A.

2014-12-01

308

Performance assessment of geological isolation systems for radioactive waste. Disposal in granite formations  

International Nuclear Information System (INIS)

In the framework of the PAGIS project of the CEC Research Programme on radioactive wastes, a performance assessment of a repository of vitrified HLW in granite was carried out. Three disposal sites were considered: the reference site Auriat and two alternative sites, Barfleur and a site in the U.K. The report describes the methodology adopted (a deterministic and a stochastic approach) with the corresponding data base and the models used. A parametric study of sub-systems (near field, far field and biosphere) was carried out by CEA-ANDRA using AQUARIUS, DIMITRIO and BIOS. A global evaluation of the performances was carried out by CEA-IPSN using MELODIE code. The results of deterministic calculations showed for Auriat a maximum dose equivalent evaluated at 6.10-3m Sv/a arising 3 millions years after disposal. Results of human intrusion scenario analyses, uncertainty analyses and global sensitivity analyses are presented. This document is one of a set of 5 reports covering a relevant project of the European Community on a nuclear safety subject having very wide interest. The five volumes are: the summary (EUR 11775-EN), the clay (EUR 11776-EN), the granite (EUR 11777-FR), the salt (EUR 11778-EN) and the sub-seabed (EUR 11779-EN)

309

Rock physics characterization of Conway granite from a DOE borehole, Conway, New Hampshire  

Energy Technology Data Exchange (ETDEWEB)

The Conway granite of New Hampshire is a highly radioactive intrusive into which a 1-km-deep borehole was drilled and continuously cored in 1975. There are two major granitic units, the Osceola and the Conway. The Conway is cut by three lamprophyre dikes. Elastic moduli and petrographic studies were on 14 samples from the core. These data and observations have been used to determine groupings in the rocks by characterizing microstructure. An important result is that carefully taken physical properties data (for example, velocities and strains) are sensitive indicators of microstructure. Based on velocity and strain data, three distinct groups are found: the lamprophyre dike rocks and two groups each of which contain samples from both the Osceola and Conway formations. These groups are also distinguished by petrographic observations of microcrack patterns. The groups are apparently controlled by grain size and by uniformity of the mixing of the mineral phases in the samples, and not by mineral modes or depth. This last result implies the coring of the Conway samples may have intensified the amount of cracking over that in the rocks in situ, but not the type of cracking. Coring does not apparently induce a distinct population of very thin (low aspect ratio) cracks; that is, such cracks are not needed to explain the low pressure stress and velocity data of these samples.

Warren, N.

1979-11-01

310

Data Access by Data Intrusion  

Directory of Open Access Journals (Sweden)

Full Text Available The mining is a source for the data base as it requires several elements and techniques for the retrieval operations. Some techniques and their corresponding technologies have an important role in the database which is required in large amounts for data access. The primary method is to retrieve the relevant data and the secondary is retrieval of the matched data. Generally the data ware houses is much more than an information technology project for the companies embracing the concept of mass customization. The Armed data warehouses filled with quality information but one has to use mass customization techniques and scientific testing methods to expand the customer based from one million to 10 million in 10 year’s period. The mass customization is ultimate use of data ware housing and the mining techniques which are making the integral part of the business process. Just like the arms, a data ware house and data mining increases the strength with the active use. With every new test and new product valuable information is added and at the same time information is retrieved, modified which allows the analysts to learn from the successes and the failures of the past. The paper is mainly concerned with retrieval operation by enforcing these failures and successful operation in the form of data intrusion. The data intrusion helps in recognizing the data in the form of mass storage and can be retrieved the relevant data. It is simple and one of the techniques which can cope up with the business market.

SarathChand P.V

2011-09-01

311

The Paleoproterozoic Nattanen-type granites in northern Finland and vicinity – a postcollisional oxidized A-type suite  

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Full Text Available The ~1.8 Ga Nattanen-type granites in the Finnish Lapland and western Kola Peninsula are found as several relatively small, high-level, discordant plutons that are easily discernible as weak maxima on aeromagnetic maps. We present U–Pb mineral isotope data on the Finnishplutons. The concordia ages are in the 1.79?1.77 Ga range and there is little evidence for inheritance. Initial radiogenic isotope compositions (our common-Pb data combined with previously published whole-rock Nd and Hf data imply a major, yet varying, Archeansource component. Elemental geochemical data on five Finnish intrusions (the Nattanen stock, the Tepasto and Pomovaara complexes, the Riestovaara and Vainospää batholiths, as well as associated dyke rocks allow the Nattanen-type granites to be classified as oxidizedA-type granites. Their petrogenesis may be related to partial melting of the lower crust by mafic underplating (extensional setting or as a result of thermal relaxation in thickened crustal setting.

Esa Heilimo

2009-06-01

312

Retention of Anionic Species on Granite: Influence of Granite Composition - 12129  

Energy Technology Data Exchange (ETDEWEB)

Technetium (Tc-99, T{sub 1/2} = 2.1.10{sup 5} yrs) and selenium (Se-79, T{sub 1/2} = 6.5.10{sup 4} yrs) belong among fission products, being produced by fission of nuclear fuel. Both elements can significantly contribute to risk due to their complicated chemistry, long life times, high mobility and prevailing anionic character. Therefore, knowledge of migration behaviour under different conditions can significantly improve input into performance and safety assessment models. Granite is considered as a potential host rock for deep geological disposal of radioactive waste in many countries. Granitic rocks consist usually of quartz, feldspar, plagioclase (main components), mica, chlorite, kaolinite (minor components). The main feature of the rock is advection governed transport in fractures, complemented with diffusion process from fracture towards undisturbed rock matrix. The presented work is focused on interaction of anionic species (TcO{sub 4}{sup -}, SeO{sub 4}{sup 2-}, SeO{sub 3}{sup 2-}) with granitic rock. Furthermore, the importance of mineral composition on sorption of anionic species was also studied. The batch sorption experiments were conducted on the crushed granite from Bohemian Massive. Five fractions with defined grain size were used for static batch method. Mineral composition of each granitic fraction was evaluated using X-ray diffraction. The results showed differences in composition of granitic fractions, even though originating from one homogenized material. Sorption experiments showed influence of granite composition on adsorption of both TcO4{sup -} and SeO3{sup 2-} on granitic rock. Generally, Se(IV) showed higher retention than Tc(VII). Se(VI) was not almost sorbed at all. Fe containing minerals are pronounced as a selective Se and Tc sorbent, being reduced on their surface. As micas in granite are usually enriched in Fe, increased sorption of anionic species onto mica enriched fractions can be explained by this reason. On the other hand, fractions enriched in feldspar did not show increased sorption affinity to Tc and Se. (authors)

Videnska, Katerina [Institute of Chemical Technology, Prague (Czech Republic); Havlova, Vaclava [Nuclear Research Institute Rez, Rez, 25068 (Czech Republic)

2012-07-01

313

Episodic granitoid emplacement in the western Kaapvaal Craton: evidence from the Archæan Kraaipan granite-greenstone terrane, South Africa  

Science.gov (United States)

Field, petrological, geochemical, isotopic and geophysical data have been assembled to determine the nature and extent of Archæan Kraaipan granite-greenstone rocks on the western edge of the Kaapvaal Craton, southern Africa. The Kraaipan greenstone belts, consisting of metamorphosed mafic volcanic rocks and interlayered metasediments (mainly banded iron formations, jaspilites and ferruginous cherts), occur poorly exposed beneath cover sequences comprising mainly Neoarchæan Ventersdorp Supergroup volcanic rocks and a blanket of Tertiary-Recent Kalahari sediments. A variety of granitoid rocks intruded the Kraaipan greenstones, which, on the basis of whole rock Pb?Pb dating of banded iron formations, have yielded an age of 3410+61/-64 Ma. The earliest granitic rocks, which comprise tonalites and trondhjemitic gneisses, were dated using the single grain Pb evaporation technique on zircons, and yielded minimum ages ranging from 3162±8 to 3070±7 Ma in the study area. This, coupled with 3250-3030 Ma ages reported for gneisses in the Kimberley and other areas on the western edge of the Kaapvaal Craton, suggests a prolonged evolution for the basement gneisses which were also disturbed between 2940 and 2816 Ma ago, probably during episodes of migmatisation. Potassium-rich granitoids, also dated using the single grain Pb evaporation method, range in age from 2880±2 to 2846±22 Ma and extend from the Schweizer-Reneke area in the south to the Botswana border and beyond in the north. Geophysical evidence (aeromagnetic and Bouguer gravity data) suggest that the intrusions may be interconnected and might have been emplaced episodically across the study area. A close spatial relationship exists between these granodiorites and adamellites, and known Au mineralisation present in the Kraaipan-Madibe areas in the north and the Amalia area in the south. This suggests a possible genetic link which could be of significance in mineral exploration. Lastly, a late granitoid pluton, the Mosita Adamellite, yielded a Pb evaporation age of 2749±3 Ma and is the youngest intrusive body recorded in the Kraaipan granite-greenstone terrane. Its presence beneath Kalahari sand cover is defined by Bouguer gravity data. The Kraaipan granite-greenstone terrane, with a prominent north-south trend, appears to represent an Archæan crustal segment that may have accreted episodically on to the western edge of the Kaapvaal Craton. In a manner similar to the Murchison granite-greenstone terrane in the northeastern part of the craton, the region may also have constituted an important potential source of placer Au mineralisation found in the Witwatersrand Basin.

Anhaeusser, Carl R.; Walraven, Feo

1999-02-01

314

Innovative Method for Saltwater Intrusion Control  

Directory of Open Access Journals (Sweden)

Full Text Available Salt water intrusion is the migration of saltwater into freshwater aquifers under the influence of groundwater development (Freeze and Cherry, 1979. The most detrimental effect that ground water depletion causes lowering of water table. Another problem due to saltwater intrusion is changing saltwater freshwater interface. Methods for controlling intrusion vary widely depending on the source of the saline water, the extent of intrusion, local geology, water use and economic factors. The proposed methodology to control saltwater intrusion is (ADR Abstraction, Desalination and Recharge. The proposed methodology interplays between the major parameters of the system to control saltwater intrusion. These parameters include the soil/aquifer properties, the well locations, the well depths, the rates and the relation between the abstraction and recharge rates which depends on the recovery rate and the salinity degree. It is capable of completely preventing saltwater intrusion because it increases the volume of fresh groundwater and decreases the volume of saltwater, while considering economical aspects, environmental impact and sustainable development of water resources.

Z. Payal

2014-02-01

315

Transition from oceanic to continental lithosphere subduction in southern Tibet: Evidence from the Late Cretaceous-Early Oligocene (~ 91-30 Ma) intrusive rocks in the Chanang-Zedong area, southern Gangdese  

Science.gov (United States)

Little is known about the detailed processes associated with the transition from oceanic to continental lithosphere subduction in the Gangdese Belt of southern Tibet (GBST). Here, we report zircon U-Pb age, major and trace element and Sr-Nd-Hf isotopic data for Late Cretaceous-Early Oligocene (~ 91-30 Ma) intermediate-acid intrusive rocks in the Chanang-Zedong area immediately north of the Yarlung-Tsangpo suture zone. These rocks represent five magmatic episodes at ~ 91, ~ 77, ~ 62, ~ 48, and ~ 30 Ma, respectively. The 91-48 Ma rocks have slightly lower initial 87Sr/86Sr (0.7037 to 0.7047), and higher ?Nd(t) (+ 1.8 to + 4.3) and ?Hf(t) (+ 3.5 to + 14.7) values in comparison with those (0.7057 to 0.7062, - 3.3 to - 2.5 and + 2.2 to + 6.6) of the ~ 30 Ma intrusive rocks. The ~ 91, ~ 62 and ~ 30 Ma rocks are geochemically similar to slab-derived adakites. The ~ 91 Ma Somka adakitic granodiorites were likely derived by partial melting of the subducting Neo-Tethyan oceanic crust with minor oceanic sediments, and the ~ 91 Ma Somka dioritic rocks with a geochemical affinity of adakitic magnesian andesites likely resulted from interactions between adakitic magmas and overlying mantle wedge peridotite. The ~ 77 Ma Luomu diorites were probably generated by partial melting of juvenile basaltic lower crust. The ~ 62 Ma Naika and Zedong adakitic diorites and granodiorites were likely generated mainly by partial melting of thickened juvenile mafic lower crust but the source region of the Zedong adakitic rocks also contained enriched components corresponding to Indian continental crust. The ~ 48 Ma Lamda granites were possibly generated by melting of a juvenile basaltic crust. The younger (~ 30 Ma) Chongmuda adakitic quartz monzonites and minor granodiorites were most probably derived by partial melting of Early Oligocene northward-subducted Indian lower crust beneath the southern Lhasa Block. Taking into account the regional tectonic and magmatic data, we suggest that the Gangdese Belt of southern Tibet (GBST) underwent a tectonodynamic transition from oceanic subduction to continental subduction between 100 and 30 Ma. It evolved through four stages: 100-65 Ma roll-back of subducted Neo-Tethyan oceanic lithosphere; 65-60 Ma initial collision between Indian and Asian continents; 60-40 Ma breakoff of subducted Neo-Tethyan oceanic lithosphere; and ~ 30 Ma northward subduction of the Indian continent.

Jiang, Zi-Qi; Wang, Qiang; Wyman, Derek A.; Li, Zheng-Xiang; Yang, Jin-Hui; Shi, Xiao-Bing; Ma, Lin; Tang, Gong-Jian; Gou, Guo-Ning; Jia, Xiao-Hui; Guo, Hai-Feng

2014-05-01

316

The Younger Dryas age of the Salpausselkä moraines in Finland  

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Full Text Available The late-glacial Younger Dryas Stadial, as defined over seventy years ago in Denmark, was compared with the withdrawal of the Scandinavian ice sheet and correlated in Finland in 1951 with the formation of the Salpausselkä moraines. Since then a great number of studies of Younger Dryas has eventually led to its definition in the Event Stratigraphy for the North Atlantic region, based on the oxygen isotope stratigraphy in the Greenland ice-core NGRIP. The age of the Younger Dryas / Preboreal boundary, the beginning of the Holocene, is in this stratigraphy dated at 11 653 yr. BP, an age close to the age deter-mined for the drainage of the Baltic Ice Lake and the beginning of the rapid retreat of the ice margin from Salpausselkä II in Finland and the corresponding Billingen moraine in Sweden. This leads to the conclusion that the Salpausselkä moraines Ss I and Ss II were formed during Younger Dryas, according to the revised varve chronology between c. 12 260 and c. 11 600 yr. BP. The third Salpausselkä, Ss III, was according to this dating formed in early Holocene. After the 1950s, when the Salpausselkä moraines were dated as having been formed during the Younger Dryas Stadial, the ages of the boundaries of Younger Dryas changed as a result of revisions of the time scales of varved clays and the use of radiocarbon ages and their calibrations. As a result of these changes the age of the two main Salpausselkä moraines, Ss I and Ss II, is older than assumed 60 years ago on the basis of the varve chronology.

Joakim Donner

2010-12-01

317

Total exploitation of an ornamental granite quarry  

OpenAIRE

In this paper we propose a methodology to estimate the recovery percentage for each of the products which can be obtained from the exploitation of an ornamental granite quarry: block, semiblock, masonry-transverse stone, and the smaller materials that can be used to obtain construction aggregates. This methodology ensures that quarry exploitation is exhaustive, thereby minimising the production of spoils and the consequent negative impact on the environment. The analysis is based on a detaile...

Taboada, J.; Alejano, L. R.; Bastante, F. G.; Ordo?n?ez, C.

2005-01-01

318

Comparison of specularly reflecting mirrors for GRANIT  

Science.gov (United States)

The specularity of ultracold neutron reflection was compared for different "promising" surfaces, including sapphire, silica, silica with carbon (diamond-like), and copper coatings with very small roughness. The probability of total losses of ultracold neutrons (UCN) from a specular trajectory was dominated by diffusive (non-specular) elastic scattering of UCN. In all the cases considered the quality of reflection was sufficiently high for storage of UCN at specular trajectories for the first stage of GRANIT experiment.

Nesvizhevsky, V. V.; Pignol, G.; Protasov, K. V.; Quemener, G.; Forest, D.; Ganau, P.; Mackowski, J. M.; Michel, Ch.; Montorio, J. L.; Morgado, N.; Pinard, L.; Remillieux, A.

2007-08-01

319

Diffusion of uranium in the granite rock  

International Nuclear Information System (INIS)

In the safety assessment of high level radioactive waste disposal, a significant retardation factor of radionuclides leaking from an underground repository can be expected. When radionuclides released from an underground repository are transported with the moving groundwater along cracks in the rock, the radionuclides will be retarded by not only adsorption on the surface of the cracks but also by process diffusion into submicron pores of rock matrix. In this experiments have been performed by process diffusion of uranium in water saturated granite. The measured penetration profile of uranium was composed of two parts. This profile was successfully explained by considering two diffusion paths in granite rock. One diffusion path was possibly a fissure with a width of few microns and another was a submicron pores of granite rock. The orders of magnitude of diffusivities for uranium were 10-12 m2/sec through the fissure and 1015 m2/sec through the submicron pores. The difference between the diffusivities of two path is thought to be caused by small geometrical factor of submicron pores, if to compared with fissures. (author)

320

Advanced technologies for perimeter intrusion detection sensors  

Energy Technology Data Exchange (ETDEWEB)

The development of integrated circuit fabrication techniques and the resulting devices have contributed more to the advancement of exterior intrusion detectors and alarm assessment devices than any other technology. The availability of this technology has led to the improvements in and further development of smaller more powerful computers, microprocessors, solid state memories, solid state cameras, thermal imagers, low-power lasers, and shorter pulse width and higher frequency electronic circuitry. This paper presents information on planning a perimeter intrusion detection system, identifies the site characteristics that affect its performance, and describes improvements to perimeter intrusion detection sensors and assessment devices that have been achieved by using integrated circuit technology.

Williams, J.D.

1995-03-01

321

Geochronological and geochemical study of the Pan African intrusive rocks along the Najd Fault system in El Wajh area, Saudi Arabia  

Science.gov (United States)

In the active tectonic regions, shear zones play an important role to re-configure the structure of the lithosphere. One of the largest shear zones on the Earth is the Najd Fault system of the Arabian-Nubian Shield. Literature data record the main active phase of this shear zone during the last stages of the Pan-African Orogeny (ca. 650-550 Ma). Compilation of new geochronological and geochemical data in addition to field relation is used to figure the tectonic history of the Najd Fault system. Different relationships between igneous intrusions and the Najd Fault System are observed. Some igneous bodies predate the activity of the shear zone, others intruded during the shearing process and a later phase intruded after the activity of the Najd Fault system ceased. The intrusive rocks in the study area show a geochemical and compositional diversity. Intrusives with dioritic composition were derived from a metaluminous tholeiitic magma around 700 Ma, and granodiorite-tonalite intrusions have calcalkaline characters and display a metaluminous to peraluminous character (ca. 740 and 660 Ma) then the magmatic activity terminated with peraluminous calcalkaline intrusives which formed granitic rocks with intrusion ages of 605-580 Ma. These magmatic events are identical for the Arabian-Nubian Shield but contamination from the crust or different rates of fractionation are recorded in our samples which are responsible for variations in the geochemical signature of the intrusive rocks. Based on field observations and contact relations, the intrusive rocks within the Ajjaj shear zone were studied in details in order to determine the age and the tectonic history of this shear zone that marks the termination of the Najd System against the eastern margin of the Red Sea. The provided zircon U-Pb dating by LA-ICP-MS and field relationships confine the activation age of the Ajjaj shear zone in limited period between 605 Ma and 580 Ma.

Hassan, Mahmoud; Abu-Alam, Tamer; Hauzenberger, Christoph; Stüwe, Kurt; Tiepolo, Massimo

2014-05-01

322

U-Th-Pb systematics in hydrothermally altered granites from the Granite Mountains, Wyoming  

International Nuclear Information System (INIS)

U-Th-Pb systematics were investigated in 15 samples representing two types of deuterically altered Archean granite from Wyoming. The loss of K-feldspar during both types of deuteric alteration was accompanied by an extreme reduction of Pb content from roughly 40 ppm to less than 12 ppm in the most altered samples. Nine of the 15 samples yield anomalously young whole-rock Pb-Pb and Th-Pb ages compared to concordia ages for zircons and to whole-rock Pb-Pb and Th-Pb ages for samples of unaltered granite. The young ages are interpreted to be the result of radiogenic Pb loss during a middle Proterozoic metamorphism that disturbed several isotopic systems in the unaltered granite. The results are discussed. (author)

323

Mobile Agents in Intrusion Detection System: Review and Analysis  

Directory of Open Access Journals (Sweden)

Full Text Available Intrusion Detection System (IDS is used to detect intrusion and then alert the system administrator about the intrusion. This is what traditional IDS is all about. It is then up to the system administrator to deal with the intrusion. Human intervention is still needed when it comes to dealing with intrusion. This is because traditional IDS could only detect the intrusion but could not, on its own respond towards the intrusion. IDS is only able to alert the system administrator when it detects an intrusion. How and when the intrusion is dealt with is up to the system administrator. Human intervention when dealing with intrusion is not a problem if the person assigned to that task is always reliable. Therefore, this paper analyzes the evolution of IDS and how mobile agents such as SNORT could increase the integrity of traditional systems without human intervention.

Kamaruzaman Maskat

2011-11-01

324

Binaural Advantage for Younger and Older Adults with Normal Hearing  

Science.gov (United States)

Purpose: Three experiments measured benefit of spatial separation, benefit of binaural listening, and masking-level differences (MLDs) to assess age-related differences in binaural advantage. Method: Participants were younger and older adults with normal hearing through 4.0 kHz. Experiment 1 compared spatial benefit with and without head shadow.…

Dubno, Judy R.; Ahlstrom, Jayne B.; Horwitz, Amy R.

2008-01-01

325

Older and Younger Workers: The Equalling Effects of Health  

Science.gov (United States)

Purpose: The purpose of this paper is to consider the statistical evidence on the effects that ill health has on labour market participation and opportunities for younger and older workers in the East Midlands (UK). Design/methodology/approach: A statistical analysis of Labour Force Survey data was undertaken to demonstrate that health issues…

Beck, Vanessa; Quinn, Martin

2012-01-01

326

Gypsum-induced decay in granite monuments in Northwestern Spain  

OpenAIRE

One of the most common forms of decay in granite monuments is the detachment of the superficial layer of the stone (plaques, plaquettes and scales). Previous studies of granite monuments in the northwest Iberian Peninsula revealed a direct relation between this type of weathering and the presence of calcium sulphate, and a mechanism whereby the salt causes this type of decay was suggested. In the present study, various hypotheses as regards the origin of the gypsum found in granite monuments ...

Silva Hermo, B.; Prieto Lamas, B.; Rivas Brea, T.; Pereira Pardo, L.

2010-01-01

327

The use of the Los Santos granite stone in Salamanca  

OpenAIRE

[ENG]The still active Los Santos granite quarries, about 50 km to the south of Salamanca, have been documented as a source material for many historical buildings in Salamanca. The excellent conditions of the natural outcrops, together with activation of the Vía de la Plata Roman route, are essential factors in explaining the competitive use of the Los Santos granite. Two different granite facies, both belonging to the Spanish Central System Batholith, have been distinguished: an external fac...

Lo?pez Plaza, M.; Garci?a Los Rios Cobo, J. I.; Lo?pez Moro, F. J.; Sa?nchez, M. G.; In?igo, A. C.; Vicente Tavera, Santiago; Jime?nez Fuentes, Emiliano

2009-01-01

328

Prevention and analysis of hacker's intrusion  

International Nuclear Information System (INIS)

The author analyzes the behavior characteristics and relevant technologies about the hacker's intrusion, and gives some corresponding solutions pertinently. To the recent events about hackers, the author gives detailed introduction and puts forward the relevant advice and valuable consideration

329

On Younger Stakeholders and Decommissioning of Nuclear Facilities  

Energy Technology Data Exchange (ETDEWEB)

In modern democratic countries, information sharing and effective and open communication concerning dismantling and decommissioning of of nuclear facilities as well as the management of nuclear waste are essential for the task to build the confidence required for any further development of nuclear energy. At the same time, it is often perceived that all decision making processes about nuclear energy policies are probably increasingly influenced by public opinion. Nuclear and radiation safety Authorities have a clear role in this regard to provide unbiased information on any health and safety related issues. In order to meet this need, it is necessary for Authorities and others to understand the values and opinions of the citizens, and especially the younger ones. They hold the key to the future at the same time as their perspective on these issues is the least understood. The need of greater public participation in decision making is becoming increasingly recognised the scientific as well as the political community. Many activities are carried out in order to stimulate to higher levels of public involvement in decision making in this active research area. Younger citizens is a stakeholder group that is often excluded in decision- making processes. The existence of large gaps between the involvement of older and younger stakeholders in decision making processes needs to be addressed, since such imbalances might otherwise lead to unequal opportunities between generations and limit the future consumption level of the coming generations. Another demanding task for the present generation is to assure that appropriate financial resources are injected into the Swedish Nuclear Waste Fund. It will thereby be possible for coming generations to undertake efficient measures in the decommissioning and dismantling of older nuclear facilities. To undertake such measures in line with the environmental and health codex is essential. An appropriate balance in this regard must be based on a proper understanding of the values and value functions of younger citizens. Such information must thus be an integral part of the knowledge base to be used when plans and processes are being developed for dismantling and decommissioning of nuclear power plants and other older nuclear facilities. In the present project, empirical data have been collected and compiled in a survey of the values of younger citizens with regard to decommissioning and dismantling of older nuclear facilities. The survey constitutes a stratified sample from three towns in Poland. They are Lublin, Olsztyn and Gdansk. A total of 780 students in the age group 14-19 years participated in the Survey. The results are compared to those from a similar study in the County of Kalmar in Sweden in the year 2006. The results include some major lesson learned. These may be summarised as follows: - Younger citizens tend to base their values regarding decommissioning on safety, and environmental aspects. Aspects like future economic growth and technological processes are less influential on the values. - Younger citizens tend to express a lack of information and debate as a basis of their value functions. Likewise, they tend to express interest in the topic and are open to become more included in the processes. - Younger citizens have suggestions on how more information can be made accessible to the general public. - Younger citizens need to be better included in the stakeholder process. This can be achieved by allowances from the Swedish Nuclear Waste Fund to support groups of younger citizens to follow the Swedish process of research, development and demonstration of a concept for the management of spent nuclear fuel. Less than fully accessible information campaigns about nuclear power and associated nuclear waste may result in differences in confidence levels between different groups of stakeholders. By finding out more about the values of different stakeholders it will be possible for the Swedish Radiation Safety Authority as well as for Society as a whole to enhance the possibility t o de

Tyszkiewicz, Bogumila; Labor, Bea

2009-08-15

330

On Younger Stakeholders and Decommissioning of Nuclear Facilities  

International Nuclear Information System (INIS)

In modern democratic countries, information sharing and effective and open communication concerning dismantling and decommissioning of of nuclear facilities as well as the management of nuclear waste are essential for the task to build the confidence required for any further development of nuclear energy. At the same time, it is often perceived that all decision making processes about nuclear energy policies are probably increasingly influenced by public opinion. Nuclear and radiation safety Authorities have a clear role in this regard to provide unbiased information on any health and safety related issues. In order to meet this need, it is necessary for Authorities and others to understand the values and opinions of the citizens, and especially the younger ones. They hold the key to the future at the same time as their perspective on these issues is the least understood. The need of greater public participation in decision making is becoming increasingly recognised the scientific as well as the political community. Many activities are carried out in order to stimulate to higher levels of public involvement in decision making in this active research area. Younger citizens is a stakeholder group that is often excluded in decision- making processes. The existence of large gaps between the involvement of older and younger stakeholders in decision making processes needs to be addressed, since such imbalances might otherwise lead to unequal opportunities between generations and limit the future consumption level of the coming generations. Another demanding task for the present generation is to assure that appropriate financial resources are injected into the Swedish Nuclear Waste Fund. It will thereby be possible for coming generations to undertake efficient measures in the decommissioning and dismantling of older nuclear facilities. To undertake such measures in line with the environmental and health codex is essential. An appropriate balance in this regard must be based on a proper understanding of the values and value functions of younger citizens. Such information must thus be an integral part of the knowledge base to be used when plans and processes are being developed for dismantling and decommissioning of nuclear power plants and other older nuclear facilities. In the present project, empirical data have been collected and compiled in a survey of the values of younger citizens with regard to decommissioning and dismantling of older nuclear facilities. The survey constitutes a stratified sample from three towns in Poland. They are Lublin, Olsztyn and Gdansk. A total of 780 students in the age group 14-19 years participated in the Survey. The results are compared to those from a similar study in the County of Kalmar in Sweden in the year 2006. The results include some major lesson learned. These may be summarised as follows: - Younger citizens tend to base their values regarding decommissioning on safety, and environmental aspects. Aspects like future economic growth and technological processes are less influential on the values. - Younger citizens tend to express a lack of information and debate as a basis of their value functions. Likewise, they tend to express interest in the topic and are open to become more included in the processes. - Younger citizens have suggestions on how more information can be made accessible to the general public. - Younger citizens need to be better included in the stakeholder process. This can be achieved by allowances from the Swedish Nuclear Waste Fund to support groups of younger citizens to follow the Swedish process of research, development and demonstration of a concept for the management of spent nuclear fuel. Less than fully accessible information campaigns about nuclear power and associated nuclear waste may result in differences in confidence levels between different groups of stakeholders. By finding out more about the values of different stakeholders it will be possible for the Swedish Radiation Safety Authority as well as for Society as a whole to enhance the possibility t o de

331

Tourmaline occurrences within the Penamacor-Monsanto granitic pluton and host-rocks (Central Portugal): genetic implications of crystal-chemical and isotopic features  

Science.gov (United States)

Tourmalinization associated with peraluminous granitic intrusions in metapelitic host-rocks has been widely recorded in the Iberian Peninsula, given the importance of tourmaline as a tracer of granite magma evolution and potential indicator of Sn-W mineralizations. In the Penamacor-Monsanto granite pluton (Central Eastern Portugal, Central Iberian Zone), tourmaline occurs: (1) as accessory phase in two-mica granitic rocks, muscovite-granites and aplites, (2) in quartz (±mica)-tourmaline rocks (tourmalinites) in several exocontact locations, and (3) as a rare detrital phase in contact zone hornfels and metapelitic host-rocks. Electron microprobe and stable isotope (?18O, ?D, ?11B) data provide clear distinctions between tourmaline populations from these different settings: (a) schorl-oxyschorl tourmalines from granitic rocks have variable foititic component (X? = 17-57 %) and Mg/(Mg + Fe) ratios (0.19-0.50 in two-mica granitic rocks, and 0.05-0.19 in the more differentiated muscovite-granite and aplites); granitic tourmalines have constant ?18O values (12.1 ± 0.1 ‰), with wider-ranging ?D (-78.2 ± 4.7 ‰) and ?11B (-10.7 to -9.0 ‰) values; (b) vein/breccia oxyschorl [Mg/(Mg + Fe) = 0.31-0.44] results from late, B- and Fe-enriched magma-derived fluids and is characterized by ?18O = 12.4 ‰, ?D = -29.5 ‰, and ?11B = -9.3 ‰, while replacement tourmalines have more dravitic compositions [Mg/(Mg + Fe) = 0.26-0.64], close to that of detrital tourmaline in the surrounding metapelitic rocks, and yield relatively constant ?18O values (13.1-13.3 ‰), though wider-ranging ?D (-58.5 to -36.5 ‰) and ?11B (-10.2 to -8.8 ‰) values; and (c) detrital tourmaline in contact rocks and regional host metasediments is mainly dravite [Mg/(Mg + Fe) = 0.35-0.78] and oxydravite [Mg/(Mg + Fe) = 0.51-0.58], respectively. Boron contents of the granitic rocks are low (tourmaline saturation in granitic melts, implying loss of B and other volatiles to the surrounding host-rocks during the late-magmatic stages. This process was responsible for tourmalinization at the exocontact of the Penamacor-Monsanto pluton, either as direct tourmaline precipitation in cavities and fractures crossing the pluton margin (vein/breccia tourmalinites), or as replacement of mafic minerals (chlorite or biotite) in the host-rocks (replacement tourmalinites) along the exocontact of the granite. Thermometry based on 18O equilibrium fractionation between tourmaline and fluid indicates that a late, B-enriched magmatic aqueous fluid (av. ?18O ~12.1 ‰, at ~600 °C) precipitated the vein/breccia tourmaline (?18O ~12.4 ‰) at ~500-550 °C, and later interacted with the cooler surrounding host-rocks to produce tourmaline at lower temperatures (400-450 °C), and an average ?18O ~13.2 ‰, closer to the values for the host-rock. Although B-metasomatism associated with some granitic plutons in the Iberian Peninsula seems to be relatively confined in space, extending integrated studies such as this to a larger number of granitic plutons may afford us a better understanding of Variscan magmatism and related mineralizations.

da Costa, I. Ribeiro; Mourão, C.; Récio, C.; Guimarães, F.; Antunes, I. M.; Ramos, J. Farinha; Barriga, F. J. A. S.; Palmer, M. R.; Milton, J. A.

2014-04-01

332

U?Pb zircon and monazite ages of the La Angostura granite and the orogenic history of the northwest Argentine basement  

Science.gov (United States)

In the Cordillera Oriental of northwest Argentina, plutonic complexes of varying surface extent are aligned from NNE to SSW: Cañaní, Tipayoc, Fundición, Santa Rosa de Tastil, La Poma, Palermo, Cachi, La Paya, Molinos. They intrude the pelitic-psammitic series of the latest Precambrian-Early Cambrian Puncoviscana Formation in many places. Intrusion of the La Angostura granite (15 km south of Molinos) is believed to be post-kinematic to a second deformation (D 2) in the Sierra de Cachi. U-Pb isotopic ages of zircons and monazites have been determined on the La Angostura granite, formerly considered as Precambrian. The lower concordia intercept age of 453 + 25/-27 Ma is interpreted as the time of zircon crystallization during emplacement of the granitic complex. Within the limits of error, this Late Ordovician intercept age is confirmed by a monazite crystallization age of 462 ± 1 Ma. Thus, a Precambrian age for the granite at La Angostrua and for the minimum age of sedimentation of the Puncoviscana Formation in this area of the Cordillera Oriental must be excluded.

Lork, A.; Miller, H.; Kramm, U.

333

Trusted Computing Based Collaborative Intrusion Detection System  

OpenAIRE

Collaboration and information sharing has obliged participating parties to look for improved detection accuracy and reaction speed in Distributed Intrusion Detection Systems (DIDS) solutions. This is mainly due to the increasing number of attacks as well as increasingly sophisticated intrusions and more alarmingly various critical components of a system can be targeted. This is further exasperated by the fact that most DIDS models do not consider the attacks targeting the collaborative networ...

Jamalul-Lail Ab Manan; Norbik Bashah Idris; Hadi KhorasaniZadeh

2012-01-01

334

Using CLIPS to detect network intrusions  

OpenAIRE

This paper shows how to build a network intrusion detection system by slightly modifying NASA's CLIPS source code, introducing features such as single and multiple string pattern matching, certainty factors and time-stamp operators. Several Snort functions and plugins were adapted and used for packet decoding and preprocessing to provide the basic requirements for such a system. The integration of CLIPS and Snort features allows the specification of complex stateful network intrusion detectio...

Ali?pio, Pedro; Carvalho, Paulo; Neves, Jose?

2003-01-01

335

Using Jquery with Snort to Visualize Intrusion  

OpenAIRE

The explosive growth of malicious activities on worldwide communication networks, such as the Internet, has highlighted the need for efficient intrusion detection systems. The efficiency of traditional intrusion detection systems is limited by their inability to effectively relay relevant information due to their lack of interactive / immersive technologies. Visualized information is a technique that can encode large amounts of complex interrelated data, being at the same time easily quantifi...

Alaa El - Din Riad; Ibrahim Elhenawy; Ahmed Hassan; Nancy Awadallah

2012-01-01

336

Gravity evidence for diapiric ascent of the Northern Arran Granite.  

OpenAIRE

The Northern Arran Granite has a sub-circular form in outcrop with a diameter of about 11 km. We have acquired six gravity profiles across the margin of the granite with an average station spacing of less than 250 m, two of which were extended to give an approximately diametric profile across the whole body. Simple modelling indicates that the granite ranges in thickness between 0.3 km and 1.2 km close to the margin, and that the base of the granite is approximately horizontal. Furthermore,...

Goulty, N. R.; Dobson, A. J.; Jones, G. D.; Al-kindi, S. A.; Holland, J. G.

2001-01-01

337

Portuguese granites associated with Sn-W and Au mineralizations  

Directory of Open Access Journals (Sweden)

Full Text Available In northern and central Portugal, there are different tin-bearing granites. Most of them are of S-type, others have mixed characteristics of I-type and S-type granites and a few are of I-type. Tin-tungsten deposits are commonly associated with Hercynian tin-bearing S-type granites. Some quartz veins with wolframite are associated with an I-type granite, which has a low Sn content. In suites of tin-bearing S-type granitic rocks, Sn content increases as a function of the degree of fractional crystallization. Greisenizations of two-mica S-type granites associated with tin-tungsten mineralizations are accompanied by an increase in SiO2, H2O+, Sn, W, Nb, Ta, Rb, Zn, and Pb and decrease in MgO, Na2O, V, Sc,Zr, and Sr. The granite associated with the Jales gold deposit is of S-type and strongly differentiated like the tin-bearing S-type granites, but it has a very low Sn content. During fractional crystallization, Si, Rb, Sn, Pb, Au, As, Sb, and S increase. During increasing degree of hydrothermal alteration of this granite at the gold-quartz vein walls, there are progressive increases in K2O, H2O+, Sn, Cs, Cu, Pb, Au, Sb, As, and S.

Ana M.R. Neiva

2002-01-01

338

A Comprehensive Study in Data Mining Frameworks for Intrusion Detection  

OpenAIRE

Intrusions are the activities that violate the security policy of system. Intrusion Detection is the process used to identify intrusions. Network security is to be considered as a major issue in recent years, since the computer network keeps on expanding every day. An Intrusion Detection System (IDS) is a system for detecting intrusions and reporting to the authority or to the network administration. Data mining techniques have been successfully applied in many fields like Network Management,...

R Venkatesan, R. Ganesan

2012-01-01

339

A-type and I-type granitoids and mylonitic granites of Hassan Salaran area of SE Saqqez, Kurdistan, Iran  

Science.gov (United States)

The Hassan Salarn area is located 20km to southeast of Saqqez city in Kurdistan Province, western Iran. In this area there are two distinct granitic rock suites consisting A-type and I-type granites and also mylonitic granites. These A-type and I-type granites have various petrological and geochemical characteristics. They also have different origins and petrogenesis. A-type granitoids comprise alkali feldspar granite, syenogranite and quartz alkali feldspar syenite, whereas I-type granitoids are composed of monzogranite, granodiorite and tonalite. Geochemically, A-type granitoids are peralkaline and acmite-normative but I-type granitoids are subalkaline (calc-alkaline), metaluminous and diopside-normative. A-type granitoids are also ferroan alkali and ferroan alkali-calcic whereas I-type granitoids are magnesian and calcic. A-type granitoids resemble to within plate granites and post-orogenic granites whereas I-type granitoids resemble to volcanic arc granites. A-type granitoids contain higher concentrations of alkalies, Zr, Rb, Nb, Y, Th, Ce, high FeO/MgO ratios and lower concentrations of Mg, Ca and Sr, resembling post-orogenic A-type granites. It is possible that heat from a mantle-derived magma which intruded into the lower crust, and/or rapid crustal extension have been essential generation of approriate melts producing A-type granitoids. Thus we can conclude that A-type granitoids were generated from a mixed mantle-crust source. Negative Nb anomalies and low contents of Ti and P probably indicate a subduction-related origin for protolith of I-type granitoids. Negative Nb anomalies and enrichment in Ce relative to its adjacent elements can be related to involvement of continental crust in magmatic processes. I-type granitoids are also enriched in Rb, Ba, K, Th, Ce and depleted in Nb, Zr and Y, indicating that they have had interacted with crust. I-type granitoids may result from contamination of mantle-derived magmas by continental crust during a subduction event. The mylonitic granites are elongated masses with a NE-SW trend and their contacts with the A-type and I-type granitoids are fault contact. Hand specimens have a layered appearance with green bands made from chlorite and epidote and grey to white bands with quartz and feldspar. These rocks contain plagioclase, quartz and orthoclase under the microscope. Also fine-grained minerals such as quartz, sericite, epidote, chlorite and opaque minerals make the groundmass wrapping the porphyroclasts. Pressure shadows around porphyroclasts of plagioclase and quartz and crystallization of fine-grained quartz and sericite in these places along with intense alteration of plagioclase to epidote and sericite, existence of quartz with different sizes, andaluse extinction in quartz crystals, and elongation of chlorites, resulted from dynamic recrystallisation of biotites all indicate effect of stresses on the rocks. Considering the similar mineralogical composition of the mylonitic rocks with I-type granitoid, it could be concluded that the granodioritic magma, after intrusion and solidification, is changed to mylonite in a shear zone due to tectonical forces.

Abdullah, Fakhraddin Mohammad; Saeed Ahmad, Sheler

2014-05-01

340

A system for distributed intrusion detection  

Energy Technology Data Exchange (ETDEWEB)

The study of providing security in computer networks is a rapidly growing area of interest because the network is the medium over which most attacks or intrusions on computer systems are launched. One approach to solving this problem is the intrusion-detection concept, whose basic premise is that not only abandoning the existing and huge infrastructure of possibly-insecure computer and network systems is impossible, but also replacing them by totally-secure systems may not be feasible or cost effective. Previous work on intrusion-detection systems were performed on stand-alone hosts and on a broadcast local area network (LAN) environment. The focus of our present research is to extend our network intrusion-detection concept from the LAN environment to arbitarily wider areas with the network topology being arbitrary as well. The generalized distributed environment is heterogeneous, i.e., the network nodes can be hosts or servers from different vendors, or some of them could be LAN managers, like our previous work, a network security monitor (NSM), as well. The proposed architecture for this distributed intrusion-detection system consists of the following components: a host manager in each host; a LAN manager for monitoring each LAN in the system; and a central manager which is placed at a single secure location and which receives reports from various host and LAN managers to process these reports, correlate them, and detect intrusions. 11 refs., 2 figs.

Snapp, S.R.; Brentano, J.; Dias, G.V.; Goan, T.L.; Heberlein, L.T.; Ho, Che-Lin; Levitt, K.N.; Mukherjee, B. (California Univ., Davis, CA (USA). Div. of Computer Science); Grance, T. (Air Force Cryptologic Support Center, San Antonio, TX (USA)); Mansur, D.L.; Pon, K.L. (Lawrence Livermore National Lab., CA (USA)); Smaha, S.E. (Haystack Labs., Inc., Austin, TX (USA))

1991-01-01

341

Network Intrusion Detection using Support Vector Regression  

Directory of Open Access Journals (Sweden)

Full Text Available Data Mining is the use of algorithms to extract the information and patterns derived by the knowledge discovery in databases process. Classification maps data into predefined groups or classes. It is often referred to as supervised learning because the classes are determined before examining the data. This paper addresses using ensemble approach of Support Vector Regression for intrusion detection. Due to increasing incidents of cyber attacks, building effective intrusion detection systems (IDS are essential for protecting information systems security, and yet it remains an elusive goal and a great challenge. The feasibility and the benefits of the proposed approach are demonstrated by means of data mining problem: Network Intrusion Detection. Intrusion detection systems help network administrators prepare for and deal with network security attacks. These systems collect information from a variety of systems and network sources, and analyze them for signs of intrusion and misuse.  We show that proposed ensemble of Support Vector Regression is superior to individual approach for intrusion detection in terms of classification rate.

Govindarajan Muthukumarasamy

2011-04-01

342

Cluster based Intrusion Detection System for Manets  

Directory of Open Access Journals (Sweden)

Full Text Available Manets are the ad hoc networks that are build on demand or instantly when some mobile nodes come in the mobility range of each other and decide to cooperate for data transfer and communication. Therefore there is no defined topology for Manets. They communicate in dynamic topology which continuously changes as nodes are not stable. Due to this lack of infrastructure and distributed nature they are more vulnerable for attacks and provide a good scope to malicious users to become part of the network. To prevent the security of mobile ad hoc networks many security measures are designed such as encryption algorithms, firewalls etc. But still there is some scope of malicious actions. So, Intrusion detection systems are proposed to detect any intruder in the network and its malicious activities. Cluster based intrusion detection system is also designed to restrict the intruders activities in clusters of mobile nodes. In clusters each node run some intrusion detection code to detect local as well as global intrusion. In this paper we have taken insight of intrusion detection systems and different attacks on Manet security. Then we proposed how overhead involved in cluster based intrusion detection system can be reduced.

Nisha Dang

2012-07-01

343

Alpha intrusion on ovenight polysomnogram  

Directory of Open Access Journals (Sweden)

Full Text Available No abstract available. Article truncated after 150 words. A 30 year-old Army veteran with a past medical history significant for chronic lumbar back pain stemming from a fall-from-height injury sustained in 2006 was referred to the sleep laboratory for evaluation of chronic fatigue and excessive daytime hypersomnolence. His Epworth sleepiness scale score was 16. He denied a history of snoring and witnessed apnea. Body Mass Index (BMI was 25.7 kg/m2. His main sleep related complaints were frequent nocturnal arousals, poor sleep quality, un-refreshing sleep, prolonged latency to sleep onset, and nightmares. An In-lab attended diagnostic polysomnogram was performed. Sleep efficiency was reduced (73% and overall arousal index was not significantly elevated (3.2 events/hour. The sleep study showed rapid eye movement (REM related sleep disordered breathing that did not meet diagnostic criteria for sleep apnea. There was no evidence for period limb movement disorder. However, the study was significant for alpha wave intrusion in stage N2 non-REM and stage ...

Nahapetian R

2014-06-01

344

AIDE - Advanced Intrusion Detection Environment  

Energy Technology Data Exchange (ETDEWEB)

Would you like to know when someone has dropped an undesirable executable binary on our system? What about something less malicious such as a software installation by a user? What about the user who decides to install a newer version of mod_perl or PHP on your web server without letting you know beforehand? Or even something as simple as when an undocumented config file change is made by another member of the admin group? Do you even want to know about all the changes that happen on a daily basis on your server? The purpose of an intrusion detection system (IDS) is to detect unauthorized, possibly malicious activity. The purpose of a host-based IDS, or file integrity checker, is check for unauthorized changes to key system files, binaries, libraries, and directories on the system. AIDE is an Open Source file and directory integrity checker. AIDE will let you know when a file or directory has been added, deleted, modified. It is included with the Red Hat Enterprise 6. It is available for other Linux distros. This is a case study describing the process of configuring AIDE on an out of the box RHEL6 installation. Its goal is to illustrate the thinking and the process by which a useful AIDE configuration is built.

Smith, Cathy L.

2013-04-28

345

Pan-African alkali granites and syenites of Kerala as imprints of taphrogenic magmatism in the South Indian shield  

Science.gov (United States)

Granite and syenite plutons with alkaline affinities ranging in age from 550 to 750 Ma sporadically puncture the Precambrian granulites of the Kerala region. All the bodies are small (20 to 60 sq km), E-W to NW-SE elongated elliptical intrusives with sharp contacts and lie on or close to major late Proterozoic lineaments. Geochemical plots of A-F-M and An-Ab-Or relations show an apparent alkali enrichment trend on the former, but the plutons define relatively distinct fields on the latter. Most of the plutons are adamellitic to granitic by chemistry. The variations of SiO2 with log sub 10 K2O/MgO (1) brings out the distinct alkaline nature of the plutons. Some of the granites are extremely potassic, like the Peralimala pluton, which shows up to 11.8 percent K2O. On a SiO2-Al2O3-Na2O+K2O (mol percent) plot, the plutons vary from peraluminous to peralkaline, but none are nepheline normative. Low MgO, low to moderate CaO and high Fe2O3/FeO values are other common characteristics. Among trace elements, depletion of Ba, Sr and Rb with high K/Ba and K/Rb values are typical. Overall, the plutons show a trend of decreasing K/Rb ratio with increasing K content. Individual plutons show more clearly defined trends similar to those from granitic masses characterized by plagioclase fractionation.

Santosh, M.; Drury, S. A.; Iyer, S. S.

1988-01-01

346

High temperature hydrothermal fibrolite in «El Payo Granite», Cadalso-Casillas de Flores granitic complex (Salamanca-Caceres, Spain)  

OpenAIRE

Subsolidus replacements of fibrolite after biotite, muscovite, andalusite and feldspars have been recognized in El Payo granite near the contact with the more evolved Casillas granite. Both granites form part of the late-Variscan Cadalso-Casillas de Flores plutonic massif. Replacements follow microfractures and grain boundaries and are associated with fibrolite-quartz and less commonly fibrolite-tourmaline intergrowths. The limits of the altered zone are imprecise but the latter seems to be a...

Hassan Mohamud, A.; Casquet Marti?n, Ce?sar; Pe?rez Del Villar, L.; Cozar, J.; Pellicer Bautista, Mari?a Jose?

2002-01-01

347

The Phalaborwa Syenite Intrusions along the West-Central Boundary of the Kruger National Park  

Directory of Open Access Journals (Sweden)

Full Text Available The geology of the Phalaborwa Complex is described and emphasis placed on the distribution of the large number of syenite intrusions. The petrography of the different textural types of syenites is discussed and it is shown that porphyritic, granular, gneissic and hypidiomorphic syenites are present. The petrography shows that the deformation textures, which are present in some of the syenites, may have formed during the emplacement of syenitic magmas which contained a high concentration of crystals. The geochemistry of the syenites is discussed and it is shown that they were not derived from an alkali basaltic magma through fractional crystallisation, but that they may rather represent alkali basaltic magmas which were contaminated by granitic material. The mode of emplacement of the Phalaborwa Complex is discussed and the relationship between the pyroxenites is explained.

C. Frick

1986-12-01

348

76 FR 62758 - Wallowa-Whitman and Umatilla National Forests, Oregon Granite Creek Watershed Mining Plans  

Science.gov (United States)

...and Umatilla National Forests, Oregon Granite Creek Watershed Mining Plans AGENCY...approval of mining Plans of Operation in the Granite Creek Watershed Mining Plans analysis...proposed mining Plans in the portions of the Granite Creek Watershed under their...

2011-10-11

349

Generating contrasting granitic melts from the same source: the ca. 3.1 Ga Heerenveen and Mpuluzi batholiths, South Africa  

Science.gov (United States)

The Mpuluzi and Heerenveen batholiths of the Barberton Granite-Greenstone Terrain (BGGT), South Africa, belong to the post-tectonic, ca. 3.1 Ga GMS (granite-monzogranite-syenite) suite. They are complex batholiths formed by successive intrusion phases; and they include a range of granitoid phases, defining at least three main magmatic series: (1) leucogranites and granites; (2) quartz-monzonites and syenogranites; (3) tonalites and relatively mafic granodiorites. Despite their close spatial and temporal association, each series is very distinct geochemically, demonstrating the coexistence of various magma types. The emplacement sequence starts with leucogranites, moving on to (slightly porphyritic) granites forming the bulk of the batholiths; to late leucogranites, syenogranites/monzonites and dark granodiorites emplacing in late, syn-magmatic shear zones. However, despite the clear emplacement sequence and the well identified, successive emplacement phases, the isotopic characteristics of the GMS batholiths are strikingly homogeneous. Zircons from 18 samples of the Mpuluzi and Heerenveen batholiths, representative of all phases and magmatic series, were dated and analysed for Hf isotopes. Regardless of the relative age and petrological type, they demonstrate emplacement ages identical within error (3106 ± 8 Ma); and, perhaps more surprinsingly, similar Hf isotopic values (?Hf(T) = -1.5 ± 0.7, corresponding to model ages of ca. 3520 Ma). This would suggest that a diverse range of granitoids, ranging from leucogranites to syenites, including both peraluminous and metaluminous compositions, and spanning both sodic and potassic compositions (0.9 TTG plutonic rocks (Steynsdorp pluton and component of the Ancient Gneiss Complex of Swaziland, ACG), and felsic volcaniclastics and amphibolites of the Theespruit formation emplaced at ca. 3.52 Ga, and represent potential sources. In all geochemical diagrams, the different rock types do not define single trends; rather, each magmatic series define its own, individual trend, precluding the different facies to be represent a single differentiation (or mixing) series. We suggest that the various component of the GMS granitoids mirror fast melting of a composite crust. Melting of the Theespruit volcaniclastics resulted in the generation of leucogranites and granites. Melting of amphibolitic portions of the Theespruit group yielded granodiorites and tonalites. Finally, the syenogranites are the result of melting of dry lithologies - either a dry tonalitic basement (ACG), or melt-depleted portions of Theespruit volcaniclastics, that lost melt due to the extraction of the leucogranites and granites.

Moyen, Jean-François; Carrouée, Simon; Cuney, Michel; Zeh, Armin

2014-05-01

350

Age and origin of coeval TTG, I- and S-type granites in the Famatinian belt of NW Argentina  

International Nuclear Information System (INIS)

Full text: Located on the Palaeozoic Pacific margin of Gondwana, at the opposite extreme to the Lachlan Fold Belt, the Sierras Pampeanas of central and NW Argentina also constitute a large granitic province displaying the coeval concurrence of I and S-type magmas. The Famatinian magmatic belt consists mostly of granitoids emplaced in Early Ordovician times, after Cambrian accretion of the Pampean terrane and before the Late Ordovician/Silurian accretion of the Precordillera terrane. New SHRIMP U-Pb zircon ages, isotope and geochemical data are used to interpret the petrogenesis of this belt. Three types of granitoid are recognized in the Famatinian belt, based on lithology and geochemical data. These are (a) a minor trondhjemite-tonalite-granodiorite (TTG) group, which occurs only in the Pampean foreland, (b) a metaluminous I-type gabbromonzogranite suite, and (c) S-type granites, which occur both as small cordieritic intrusions associated with l-type granodiorites and as large batholithic masses. Twelve new SHRIMP U-Pb zircon ages establish the contemporaneity of all three types in Early Ordovician times (mainly 470-490 Ma ago). Sr- and Nd-isotopic data suggest that, apart from some TTG plutons with asthenospheric characteristics, the remaining magmas were derived from a Proterozoic crust-lithospheric mantle section (Nd model ages of 1500-1700 Ma). Granulite xenoliths in Cretaceous alkalic rocks that have been described by other authors may represent samples of this her authors may represent samples of this source region. Trace element modelling suggests that the TTG and I-type gabbros originated by variable melting of a lithospheric gabbroid source at 10-12 kbar and ca. 5 kbar, respectively. The voluminous intermediate and acidic I-types, which show a trend to slightly more evolved isotopic signatures than the inferred source, probably represent hybridization of the most primitive magmas with lower and middle crustal melts. The highly peraluminous S-type granites have similar isotopic and inherited zircon patterns to Cambrian supracrustal metasedimentary rocks deposited in the Pampean cycle, and were derived from them by local anatexis. Other major components of the S-type batholiths, including porphyritic biotite granites, probably involved melting of deeper crust and mixing with the l-type magmas, leading to an isotopic and geochemical continuum. This model is similar to others that have been advanced for the I- and S-type granites of the Lachlan Fold Belt of Australia and the Hercynian granites of Spain, but we argue that in the Famatinian belt at least no juvenile mantle source was involved. Copyright (1999) Geological Society of Australia

351

Characterization of Climax granite ground water  

International Nuclear Information System (INIS)

The Climax ground water fails to match the commonly held views regarding the nature of deep granitic ground waters. It is neither dilute nor in equilibrium with the granite. Ground-water samples were taken for chemical analysis from five sites in the fractured Climax granite at the Nevada Test Site. The waters are high in total dissolved solids (1200 to 2160 mg/L) and rich in sodium (56 to 250 mg/L), calcium (114 to 283 mg/L) and sulfate (325 to 1060 mg/L). Two of the samples contained relatively high amounts of uranium (1.8 and 18.5 mg/L), whereas the other three contained uranium below the level of detection (< 0.1 mg/L). The pH is in the neutral range (7.3 to 8.2). The differences in composition between samples (as seen in the wide range of values for the major constituents and total dissolved solids) suggest the samples came from different, independent fracture systems. However, the apparent trend of increasing sodium with depth at the expense of calcium and magnesium suggests a common evolutionary chemical process, if not an interconnected system. The waters appear to be less oxidizing with depth (+ 410 mV at 420 m below the surface vs + 86 mV at 565 m). However, with Eh measurements on only two samples, this correlation is questionable. Isotopic analyses show that the waters are of meteoric origin and that the source of the sulfate is probably the pyrite in the fracture-fill material. Analysis of the measured water characteristics using the chemical equilibrium computer program EQ3 indicates that the waters are not in equilibrium with the local mineral assemblage. The solutions appear to be supersaturated with respect to the mineral calcite, quartz, kaolinite, muscovite, k-feldspar, and many others

352

Resaturation of backfilled tunnels in granite  

International Nuclear Information System (INIS)

Highly compacted bentonite clay is proposed for use as a backfill material around high level waste overpacks to be placed in excavated tunnels in the crystalline bedrock of Northern Switzerland. Initially the bentonite will have a low residual water content and with time the bentonite will resaturate due to the influx of water from the crystalline rock. The time and degree of bentonite saturation are important for safety assessment because of their effect on the corrosion of the waste overpack, on the leaching of the waste matrix, and on the radionuclide transport in the backfill. A three-dimensional, two-phase flow model (FAMOS) is used to quantify the expected resaturation under the conditions outlined above. The time required for complete saturation simulated using FAMOS ranges from less than 100 to more than 1000 years. These results are comparable to the results of diffusive models of bentonite saturation when using a diffusion coefficient of 3x10-10 m2s-1. The time depends on the hydraulic properties of the bentonite as well as the saturated hydraulic conductivity of the crystalline rock. At saturated granite hydraulic conductivities of the order of 10-9 ms-1 the bentonite becomes fully saturated in less than 100 years. For saturated granite hydraulic conductivities of the order of 10-12 ms-1 the bentonite becomes fully saturated in several hundred to over 1000 years. For a given granite hydraulic conductivity the degree of saturation depends on the bentonite capillary pressure versus water saturation characteristic relationships. For high capillary pressures (of the order of 105 kPa) the bentonite saturates relatively quickly; with lower capillary pressures the time for complete saturation increases

353

Simulation of bentonite colloid migration through granite  

International Nuclear Information System (INIS)

Document available in extended abstract form only. Full text of publication follows: Colloidal bentonite particles generate at the interface of buffer and host rock in spent nuclear fuel repository due to an erosion process and migrate through granite by the water flow. Stability of these colloids and their migration possibilities have been studied on account of radionuclide transport possibility as colloid could carry adsorbed radionuclides in groundwater through granite. That is why a simulation of bentonite colloid migration in the surrounding of a repository might be requested. According to chemical condition as ionic strength and pH, the colloidal particles coagulate into clusters and that influence the migration of particles. The coagulation kinetics of natural bentonite colloids were experimentally studied in many articles, for example by light scattering techniques. We created a model of coagulation of bentonite colloids and simulation of a chosen experiment with use of the multicomponent reactive transport equation. The coagulation model describes clustering of particles due to attractive van der Waals forces as result of collision of particles due to heat fluctuation and different velocity of particles during sedimentation and velocity gradient of water flow. Next, the model includes influence of repulsive electrostatic forces among colloidal particles leading to stability of particles provided high surface charge of colloids. In the model, each group of clu colloids. In the model, each group of clusters is transported as one solution component and the kinetics of coagulation are implemented as reactions between the components: a shift of particles among groups of particles with similar migration properties, according to size of the clusters of colloids. The simulation of migration of bentonite colloid through granite using the coagulation model was calibrated according to experiment results. On the basis of the simulation, one can estimate the basic processes that occur during bentonite colloid migration. That could be useful for prediction of spent nuclear fuel repository safety with the help of model of bentonite colloid behavior during migration. (authors)

354

Petrogenesis of Tin-bearing Granites from Ervedosa, Northern Portugal: The Importance of Magmatic Processes  

OpenAIRE

Three Hercynian highly peraluminous tin-bearing granites define a sequence ranging from muscovite-biotite granite to muscovite granite. Tin-bearing quartz veins are genetically related to this sequence. Variation diagrams of most major and trace elements of granites, biotite and muscovite show fractionation trends. Least squares analysis of major elements and modelling of trace elements indicate that the muscovite-biotite granite M2 and the muscovite granite M3 were derived from the slightly ...

Gomes, M. E. P.; Neiva, A. M. R.

2002-01-01

355

Characterization of mechanical damage in granite  

Directory of Open Access Journals (Sweden)

Full Text Available This paper aims to illustrate the use of infrared thermography as a non-destructive and non-contact technique to observe the phenomenological manifestation of damage in granite under unconfined compression. It allows records and observations in real time of heat patterns produced by the dissipation of energy generated by plasticity. The experimental results show that this technique, which couples mechanical and thermal energy, can be used for illustrating the onset of damage mechanism by stress concentration in weakness zones.

Minh-Phong Luong

2014-01-01

356

Rare accessory uraninite in a Sierran granite  

Science.gov (United States)

One grain of uraninite was found in a single thin-section of Sierran granite. Electron and ion microprobe analysis were used to determine the composition. Since the U-Pb age calculated for the uraninite does not differ greatly from the K-Ar age of the unit in which it occurs, it is suggested that the mineral is primary and not reworked from a preexisting rock. No uraninite has been detected in heavy mineral concentrates from other rocks of the local area.

Snetsinger, K. G.; Polkowski, G.

1977-01-01

357

Strain localization during deformation of Westerly granite  

Science.gov (United States)

A specimen of Westerly granite was cyclically loaded to near failure at 50 MPa confining pressure. Holographic interferometry provided detailed measurements of localized surface deformations during loading and unloading. The data are consistent with deformation occurring primarily elastically at low differential stress; in conjunction with one incipient fault zone between approximately 350 and 520 MPa differential stress; and in conjunction with a second incipient fault zone above 580 MPa and/or during creep. During unloading only one fault zone, that which is active at the intermediate stress levels during loading, is seen to recede.

Brodsky, N. S.; Spetzler, H. A.

1984-01-01

358

Microstructural modeling of Vienne granite damage  

International Nuclear Information System (INIS)

The microstructural approach in damage modeling, which is presented in this paper describes the evolution of micro-crack geometry as a function of history loading. If the crack geometry is known, the effective properties could then be calculated foe any cracked rock by the mean of a micro-mechanical model. The PL evolution law which is necessary in the describing of crack geometry evolution is hardly based on the crack microscope observation as well as on the theory of fabric tensors. This approach is applied in the modeling of mechanical behaviour of Vienne granite. The result of model simulations are compared with laboratory tests. (author)

359

In-situ experiments in fractured granite  

International Nuclear Information System (INIS)

Two heater tests, a migration test and several corrosion tests were performed in fractured granite near surface. Predicted rock temperatures agreed well with those observed at no fracture zone. On the other hand, measured rock temperatures were lower than predicted temperatures at fracture zone because of the heat convection due to groundwater flow in a fracture zone. Migration tests were carried out in a single fracture zone of experimental room, and the results were analyzed by a single fracture model. Stress corrosion cracking test for ten kinds of metal for candidate canister materials was carried out under in-situ condition

360

GRANITE- A steroscopic imaging Chernkov telescope system  

International Nuclear Information System (INIS)

A second 10 meter class imaging telescope was constructed on Mt. Hopkins, Arizona, the site of the original 10 meter Whipple Cherenkov telescope. The twin telescope system with a 140 meter base line will allow both a reduction in the energy threshold and an improvement in the rejection of the hardonic background. The new telescope started operation in December 1991. With the final completion of the first installation stage (GRANITE I) during spring 92, it is now operating simultaneously with the orginal reflector. We describe in this paper design and construction of the new instrument and demonstrate the capability of the experiment to record coincident events

361

Thermoluminescence of the mineral components in granite  

International Nuclear Information System (INIS)

The thermoluminescence (TL) of the minerals in Climax Stock (Nevada, USA) granite has been studied. The principal mineral constituents are plagioclase, quartz, potassium feldspar and biotite. Pyrite, sphene apatite and zircon occur at one percent or less. All exhibit TL except biotite. The TL kinetics were determined for plagioclase, quartz, potassium feldspar and pyrite. Plagioclase and potassium feldspar exhibit second order and pyrite first orker kinetics. Natural TL of quartz follows second order and artificial TL first order kinetics. However, in these four minerals unrealistic kinetic parameters are often obtained; thus more general kinetics, e.g. interactive kinetics, may apply. 8 figures

362

Hippocampal sclerosis in children younger than 2 years  

Energy Technology Data Exchange (ETDEWEB)

Hippocampal sclerosis (HS) is rarely considered as a diagnosis in children younger than 2 years. To describe imaging features in conjunction with clinical information in patients with hippocampal sclerosis who are younger than 2 years. We retrospectively reviewed MR brain imaging and clinical information in five children in whom the diagnosis of HS was made both clinically and by MRI prior to 2 years of age. Imaging features establishing the diagnosis of hippocampal sclerosis were bright T2 signal and volume loss, while the internal architecture of the hippocampal formation was preserved in almost all children. Clinically, all children had an infectious trigger. It is necessary for radiologists to consider HS in children with certain clinical features to plan an MRI protocol that is appropriate for detection of hippocampal pathology. (orig.)

Kadom, Nadja [Children' s National Medical Center, Department of Diagnostic Imaging and Radiology, Washington, DC (United States); Tsuchida, Tammy; Gaillard, William D. [Children' s National Medical Center, Department of Neurology, Washington, DC (United States)

2011-10-15

363

Geochemistry and zircon geochronology of the Archean granite suites of the Rio Maria granite-greenstone terrane, Carajás Province, Brazil  

Science.gov (United States)

The Archean granites exposed in the Mesorchean Rio Maria granite-greenstone terrane (RMGGT), southeastern Amazonian craton can be divided into three groups on the basis of petrographic and geochemical data. (1) Potassic leucogranites (Xinguara and Mata Surrão granites), composed dominantly of biotite monzogranites that have high SiO2, K2O, and Rb contents and show fractionated REE patterns with moderate to pronounced negative Eu anomalies. These granites share many features with the low-Ca granite group of the Yilgarn craton and CA2-type of Archean calc-alkaline granites. These granites result from the partial melting of rocks similar to the older TTG of the RMGGT. (2) Leucogranodiorite-granite group (Guarantã suite, Grotão granodiorite, and similar rocks), which is composed of Ba- and Sr-rich rocks which display fractionated REE patterns without significant Eu anomalies and show geochemical affinity with the high-Ca granite group or Transitional TTG of the Yilgarn craton and the CA1-type of Archean calc-alkaline granites. These rocks appear to have been originated from mixing between a Ba- and Sr-enriched granite magma and trondhjemitic liquids or alternatively product of interaction between fluids enriched in K, Sr, and Ba, derived from a metasomatized mantle with older TTG rocks. (3) Amphibole-biotite monzogranites (Rancho de Deus granite) associated with sanukitoid suites. These granites were probably generated by fractional crystallization and differentiation of sanukitoid magmas enriched in Ba and Sr. The emplacement of the granites of the RMGGT occurred during the Mesoarchean (2.87-2.86 Ga). They are approximately coeval with the sanukitoid suites (˜2.87 Ga) and post-dated the main timing of TTG suites formation (2.98-2.92 Ga). The crust of Rio Maria was probably still quite warm at the time when the granite magmas were produced. In these conditions, the underplating in the lower crust of large volumes of sanukitoid magmas may have also contributed with heat inducing the partial melting of crustal protoliths and opening the possibility of complex interactions between different kinds of magmas.

Almeida, José de Arimatéia Costa de; Dall'Agnol, Roberto; Leite, Albano Antonio da Silva

2013-03-01

364

Sexuality and body image in younger women with breast cancer.  

Science.gov (United States)

Breast cancer has the potential to be most devastating to the sexual function and self-esteem of premenopausal women. Nevertheless, not one study has systematically compared the impact of breast cancer treatment on sexual issues across age groups. Research shows that younger women with breast cancer have more severe emotional distress than older cohorts. In a group of patients seeking sexual rehabilitation in a cancer center, younger couples were more distressed, but also had the best prognosis with treatment. In theory, loss of a breast or poor breast appearance would be more distressing to women whose youth gives them high expectations for physical beauty. Seeking new dating relationships after breast cancer treatment is a special stressor for single women. Potential infertility also may impact on a woman's self-concept as a sexual person. Systemic treatment disrupts sexual function by causing premature menopause, with estrogen loss leading to vaginal atrophy and androgen loss perhaps decreasing sexual desire and arousability. Research on mastectomy versus breast conservation across all ages of women has demonstrated that general psychological distress, mari