[en] The Rasimalai alkali syenite complex is emplaced within Peninsular Gneissic complex and spatially associated with NE-SW trending major Dharmapuri shear zone (DSZ) in the northern part of Tamil Nadu. It is surrounded by epidote hornblend egneiss, which is the fenetised product of Charnockite and occurs about 20 km NE of Alangayam in Vellore district. It is mainly comprised of medium to coarse grained grey syenite (albite and orthoclase) and medium to micro grained pink syenite (orthoclase, microcline and perthite) at places porphyritic in nature with hornblende, riebeckitc, aegirine and acmite as accessory minerals. Grey syenite is non radioactive and uranium mineralisation is associated with pink syenite (syngenetic and disseminated type) and quartz-barite veins (hydrothermal type). Hydrothermal activity is manifested in the form of pyrite, chalcopyrite, galena, barite, calcite and calcian-strontianite which occur in the form of disseminations, stringers, lumps, aggregates, veinlets and veins. Presence of high silica (63.14-75.43%) with high field strength elements (U, Th, Nb and Pb) and large ion lithophile elements (Rb, Sr, K, Ba) possibly indicates that Rasimalai alkali syenite is the product of crustal communication and partial melting of protracted emplacement of parental alkali basaltic magma

[en] Polymetallic, sulfo-arsenidic, vein type mineralization occurs at the roof of the quartz syenite intrusion in the Gavnunim valley, Makhtesh Ramon. Six K-feldspar (probably adularia) samples concentrated from different veins and lenses, where they are intergrown with metallic minerals and quartz, and three hypothermally altered whole rock quartz syenite samples were K-Ar dated. The calculated 40Ar/36Ar versus 40K/36Ar isochron of the six measurements performed on the K-feldspars from the veins yields an early Cretaceous age of 125±2Ma, with 40Ar/36Ar initial value of about 29.5. The three altered quartz syenite samples shoe ages very close to the isochron. The K-Ar dates confirm field relationships which indicates that the mineralization and hypothermal alteration were part of the same geological event, which closely followed the intrusion of the quartz syenite in the Early Cretaceous. (author)

[en] Two superimposed early hydrothermal alterations have been recognized in the Proterozoic Saraya leucogranite. Successively are described a major dequartzification leading to an episyenite infilled with carbonaceous matter and sulfate during an interruption of the system, succeeded by a mobilization of U and other elements during an albitization. A dolomite filling up followed by a silicopotassic feed-back alteration, close down the system

[en] The radon (Rn222) content in the Lower Cretaceous syenite intrusion was measured at 5 sites (G-1 to G-5) spanning a distance of ca 1 km. Two additional sites were located on adjacent Triassic sediments into which the syenite is intruded. Measurements were performed directly in the rocks(50 cm depth), in a 20 m grid, using the nuclear tracks method. The background radon values in the syenite are 45-90 pCi/L. The background uranium content in the same rocks is several ppm. Radon anomalies were encountered in all sites. Site G-3 exhibited the highest concentration of anomalies (22% of the measurements), where the anomalies attain 600-1000 pCi/L and cover 300-1200 m². Sandstone up to a few meters thick, covering the continuation of G-3, shows a similar anomalous concentration. It is concluded that the latter anomalies reflect the radon content in the underlying syenite. No correlation was found between the background radon level and the local content of uranium measured at the radon sampling point, nor can any correlation be established with some high concentrations of uranium connected with vein type polymetallic mineralization, especially at site G-1. Boreholes drilled in the radon anomalous areas at G-3, to a depth of up to 100 m encountered the country rock with its background distribution of uranium and did not reveal a source for the anomalies. In light of the relations it is concluded that: (a) the background values of radon are associated with its local emanation and diffusion; (b) the radon anomalies are due to a source, centered around G-3, situated at a depth > 100 m from which the radon is transported by convection to the surface via joints and fractures in the syenite. (author)

[en] Present work dedicated to determination of chemistry pass processes atinteraction of nepheline syenites with calcium chloride on the baking stage

[en] The Ilimaussaq alkaline complex, the type locality of agpaitic nepheline syenites, is made up of three intrusive phases, 1) augite syenite, 2) alkali acid rocks and 3) agpaitic nepheline syenites which occupy the major part of the complex. The agpaitic phase comprises a roof series, a floor series and an intermediate sequence of rocks. The roof series crystallised from the roof downwards beginning with non-agpaitic pulaskite and ending with distinctly agpaitic naujaite. The exposed part of the floor series is made up of the layered agpaitic nepheline syenite kakortokite. The intermediate sequence consists of several types of distinctly agpaitic lujavrites which are accompanied by occurrences of uranium and other rare elements. The complex was first visited by K.L. Giesecke in 1806 and 1809. The first detailed mapping of the complex was carried out by N.V. Ussing in 1900 and 1908. He presented a precise description of the major rock types and an illuminating discussion of the petrology of the complex in his 1912 memoir. In the period 1912-1955 there was very limited activity in the complex. Exploration for radioactive minerals in Ilimaussaq was initiated in 1955 and in subsequent years followed by geological mapping carried out by the Geological Survey of Greenland. This led to a series of detailed studies of the occurrences of not only U, but also Be, Nb, REE and Zr, and to mineralogical, geochemical and petrological studies as well as commercial evaluation and drilling. (au)

[en] The mineralogical composition of nepheline syenites of Turpe depositdetermined by crystal-optic method. The investigated object representmedium-grained, grey mineral with impurities of black colour

[en] In the southeastern foothills of the Royal Society Range, southern Victoria Land, a diverse array of gabbroic to granitic rocks intrude marbles and schists of the late Proterozoic Skelton Group. A-type characteristics include abundant fluorite, high SiO₂, Na₂O, K₂O, Ga/Al, Y and Nb with low Sr and CaO. A monzogabbro and a monzonite have identical 539 ± 4 Ma ages and a quartz-monzonite is 534 ± 3 Ma. Nearby is a 517 ± 4 Ma A-type granite pluton with more extreme A-type geochemical characteristics. This is the first report of A-type granites from anywhere in the Transantarctic Mountains. The presence of these A-type granitoids in close proximity to contemporaneous nepheline syenites and carbonatites suggests strongly that this area was undergoing extension during pluton emplacement. The occurrence of A-type granitoids at least as far south as the Skelton Glacier suggests that the atypical, extensional province, herein referred to as the Koettlitz Glacier Alkaline Province, extends for at least 60 km parallel to the Transantarctic Mountains. Alkaline magmatism in the Koettlitz Glacier Alkaline Province initiated before the generation of voluminous subduction-related calc-alkaline magmas related to the Ross Orogeny. (author). 38 refs., 7 figs., 2 tabs

No abstract available

[en] For the purpose of investigation of physical and chemical characteristic of mixture of chlorides has been done the treatment of nepheline syenite by using chemical and radiography phase analysis