Syenite

Intrusive Deposits. Deposits included in the intmsive deposit type are those associated with intmsive or anatectic rocks of different chemical composition, eg, alaskite, granite, monzonite, peralkaline syenite, carbonatite, and pegmatite. Examples include the uranium occurrences in the porphyry copper deposits such as Bingham Canyon and Twin Butte in the United States, the Rossing Deposit in Namibia, and Ilimaussaq deposit in Greenland, Palabora in South Africa, and the deposits in the Bancroft area, Canada (15). 

Zirconium occurs naturally as a siUcate in zircon [1490-68-2] the oxide baddeleyite [12036-23-6] and in other oxide compounds. Zircon is an almost ubiquitous mineral, occurring ia granular limestone, gneiss, syenite, granite, sandstone, and many other minerals, albeit in small proportion, so that zircon is widely distributed in the earth s cmst. The average concentration of zirconium ia the earth s cmst is estimated at 220 ppm, about the same abundance as barium (250 ppm) and chromium (200 ppm) (2). 

The actual name dry scrubbing was first publicized by Teller [U.S. Patent no. 3,721,066 (1973)]. He worked both with classical Army-type soda-lime and with his patented water-activated form of the alkaline feldspar nepheline syenite as a flow agent and feedstock sorbent for HF and SO9 in hot, sticky fumes from glass melting furnaces. He claimed capture of more than 99 percent of 180 ppm HF and SO9 for more than 20 hours in a packed bed of 200 X 325 mesh hydrated nephehne syenite at 42,000/hr. 

Valuable mineral deposits which form by residual concentration pertain to iron, manganese, aluminum, nickel, clays, tin and gold. Aluminum comes almost exclusively from residual concentrations of bauxite, which result from the laterihsation of alumina rich igneous rocks like syenites under tropical and subtropical climatic conditions. Laterites also contribute nearly 80% of the world s reserves of nickel at grades better than 1% Ni. They form by residual concentrations as a result of weathering of mafic and ultramafic igneous rocks, which are relatively enriched in nickel. 

Silicates Clays, napheline-syenite beryllium ores serpentine... 

Bedrock and surficial Geology At Shiko Lake (Fig. 1) a Jurassic complex composed of diorite, monzonite, and syenite intrudes basalt and volcaniclastic rocks. Chalcopyrite, bornite, and gold occur disseminated and in veins mainly within the syenite (Fig. 2). 

Sapphires are naturally occurring gem stones, and are transparent to translucent. We know from ancient records that they have always been highly prized. Natural sapphires are found in many igneous rocks, especially syenites and pegmatites. Alternatively, synthetic sapphires may be made by doping aluminium oxide AI2O3 with a chro-mophore. 

Vidal, P., Dosso, L., Bowden, P. Lameyre, J. (1979). Strontium isotope geochemistry in syenite-alkaline granite complexes. In Origin and Distribution of the Elements, ed. L. H. Ahrens, pp. 223-31. Oxford Pergamon. 

Aegiiine NaFeSi206 Nepheline syenites hypersodic granites... 

Fig. 4. Lower part of the Horne deposit depioting relationships between synvoloanic mafio dykes (green), late syenite dykes (yellow) and high grade Cu mineralization (red bodies). Struotural oontours are 200 feet.

The mineralized district is restricted by two main strike-slip faults of Kubanan to the east and Posht e Bdam to the west (Fig. la). The host rocks are a thick sequence of Upper Precambrian-Cambrian rhyolite, tuff, alkali granite, syenite, mafic dykes, magnetitite, dolomite, gypsum, limestone, black shale, and sandstone. The Upper Percambrian-Cambrian sequence is overlain unconformably by Mesozoic and... 

Syenite, lamprophyre, and carbonatite dykes of the Moose Creek Valley, Ice River Alkaline Complex, southeastern British Columbia, Canada ... 

Keywords dykes, alkaline, carbonatite, syenite, lamprophyre... 

The IRAC can be intrusive subunits, emplacement these feldspar-free layered mafic (LMSC), (2) a large carbonatite lens, (3) a zoned nepheline syenite sub-complex (ZSSC), and (4) a dyke suite consisting of syenitic dykes, carbonatites, and alkaline... 

The contacts between lamprophyres and the IRAC range from planar to very irregular. The lamprophyres typically exhibit a chilled margin. However, at both the hand sample and thin-section scale, a sannaite lamprophyre sample exhibits a cuspate boundary against a nepheline syenite dyke, indicative of two partially molten materials. Lamprophyre dykes cross-cutting syenitic dykes have also been observed. 

Based on mineralogical and textural similarities (supported by geochemistry), the rocks of the syenitic dyke swarm can be subdivided into three groups (1) nepheline syenite - nephelinolite group (NS-N), (2) syenite - monzodiorite group (SM), and (3) an alkali feldspar granite dyke. 

The rocks of the NS-N dyke group range from nepheline syenite to sodalite-bearing nephelinolite. The primary phases in the NS-N dyke group are k-feldspar and nepheline, with variable abundances of amphibole, plagioclase, phlogopite, calcite, sodalite, titanite, cancrinite, apatite, clinopyroxene, zircon, chlorite, quartz, pyrochlore, and opaque phases. 

As the sannaites have moderate to high Mg (27-54), Nb/U (26-48), and no xenoiiths (all consistent with minimal crustal contamination) they can be used to assess the nature of the mantle source. Regardless of the variation between groups, the low Sr/ Sr368Ma values suggest that the sannaites (and syenites) were derived from partial melting in the mantle, and the nci values indicate that the mantle source was depleted relative to bulk earth. 

Monazite crystals within the ferrocarbonatite sample were dated using CHIME U-Th-Pb, and an age of 165 8 Ma was calculated. This age was used to evaluate the Sm-Nd ( nci= -6.0) and Rb-Sr ( Sr/ Sri65 = 0.71061) data these values are considerably different than the syenites and the sannaites. The high initial "sr/ Sr and low nci indicate that the... 

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