Abstract Carbonatites from the Khibina Alkaline Massif (360–380 Ma), Kola Peninsula, Russia, contain one of the most diverse assemblages of REE minerals described thus far from carbonatites and provide an excellent opportunity to track the evolution of late-stage carbonatites and their sub-solidus (secondary) changes. Twelve rare earth minerals have been analysed in detail and compared with literature analyses. These minerals include some common to carbonatites (e.g. Ca-rare-earth fluocarbonates and ancylite-(Ce)) plus burbankite and carbocernaite and some very rare Ba, REE fluocarbonates. Overall the REE patterns change from light rare earth-enriched in the earliest carbonatites to heavy rare earth-enriched in the late carbonate-zeolite veins, an evolution which is thought to reflect the increasing ‘carbohydrothermal’ nature of the rock-forming fluid. Many of the carbonatites have been subject to sub-solidus metasomatic processes whose products include hexagonal prismatic pseudomorphs of ancylite-(Ce) or synchysite-(Ce), strontianite and baryte after burbankite and carbocernaite. The metasomatic processes cause little change in the rare earth patterns and it is thought that they took place soon after emplacement.
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Journal Article Extrusive Carbonatites from the Uyaynah Area, United Arab Emirates Get access A. R. WOOLLEY, A. R. WOOLLEY 1Department of Mineralogy, British Museum (Natural History)Cromwell Road, London S W7, 5BD, UK Search for other works by this author on: Oxford Academic Google Scholar M. W. C. BARR, M. W. C. BARR 2Hunting Technical Services Limited, Thamesfield HouseBoundary Way, Hemel Hempstead, Hertfordshire HP2 7SR, UK Search for other works by this author on: Oxford Academic Google Scholar V. K. DIN, V. K. DIN 1Department of Mineralogy, British Museum (Natural History)Cromwell Road, London S W7, 5BD, UK Search for other works by this author on: Oxford Academic Google Scholar G. C. JONES, G. C. JONES 1Department of Mineralogy, British Museum (Natural History)Cromwell Road, London S W7, 5BD, UK Search for other works by this author on: Oxford Academic Google Scholar F. WALL, F. WALL 1Department of Mineralogy, British Museum (Natural History)Cromwell Road, London S W7, 5BD, UK Search for other works by this author on: Oxford Academic Google Scholar C. T. WILLIAMS C. T. WILLIAMS 1Department of Mineralogy, British Museum (Natural History)Cromwell Road, London S W7, 5BD, UK Search for other works by this author on: Oxford Academic Google Scholar Journal of Petrology, Volume 32, Issue 6, December 1991, Pages 1143–1167, https://doi.org/10.1093/petrology/32.6.1143 Published: 01 December 1991 Article history Received: 25 September 1990 Accepted: 29 March 1991 Published: 01 December 1991
Life cycle assessments (LCA) are useful to quantify the environmental costs of mining projects, however the application of LCA is often a retrospective environmental measurement of operating mines. This paper presents a novel methodology of carrying out a LCA to generate life cycle impact assessment data that can form an environmental block model of a deposit. These spatially explicit data can then be used as a constraint within long-term mine scheduling simulations. The results indicate that significant reductions in global warming impact can be achieved at a small economic cost. For example using an environmental constraint it was possible to achieve 91.9% of the global warming impact whilst achieving 95.9% of the net present value compared to the baseline. Different constraints and economic scenarios are explored and multi-criteria decision analysis is carried out. This approach enables environmental considerations to be included in strategic mine planning. This is important because mining will continue to form an important part of our society for the foreseeable future. Integrating environmental considerations into the earliest stages of mine planning can assist in driving environmentally responsible raw material extraction.
Abstract The ∽16 Ma Rangwa Caldera Complex, part of the large Kisingiri nephelinite-carbonatite volcano, Homa Bay District, western Kenya (0º34’S; 34º09’E) contains carbonatitic lapilli and ash tuffs, agglomerate and tuffisite, and a number of intrusive calcite carbonatites. A detailed petrographic and electron microprobe study has been performed on 20 fresh samples from the collection at The Natural History Museum, London. Most of the juvenile lapilli and ash particles are either predominantly composed of devitrified silicate glass (now biotite/phlogopite but probably also originally potassic silicate) or calcite carbonatite, which suggests that two molten liquids were erupted simultaneously. Some 10 mm-diameter lapilli contain quench-textured calcite crystals set in devitrified glass. They are interpreted as having crystallized from a molten silicate-carbonate melt at, or very near, the surface. The extrusive carbonate is mostly composed of calcite, consistent with intrusive calcite compositions at Rangwa. Other key minerals are magnetite, two types of mica (magnesian-biotite phenocrysts and phlogopite xenocrysts) and fluorapatite. The pyroclastic rocks contain many calcite carbonatite clasts, and fragments of calcite, aegirine and diopside, fluorapatite, magnetite, plus some phlogopite, titanite, K-feldspar, fenite and glimmerite; ijolite lithics are rare. Thus, there is no evidence for a cognate nephelinitic (ijolitic) or melilitic magma nor evidence for a direct relationship with the nephelinites of the Kisingiri volcano. Two hypotheses are discussed. A rising silicate and K-rich carbonatite liquid may have evolved towards a carbonate-rich K-silicate liquid after crystallization of calcite, phlogopite, apatite and magnetite. Preservation of the the potassic component may be rare, with a more usual scenario being that potassic component separates as fenitizing fluids. The alternative is that the silicate component is remobilized fenite, formed from country rock that was mobilized by supercritical K-rich, fenitizing fluids associated with the carbonatite. Both scenarios require generation of a K-rich carbonatite magma, probably from a carbonated phlogopite-rich metasomatized mantle.
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