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Phase Equilibrium Constraints on Intensive Crystallization Parameters of the Ilimaussaq Complex, South Greenland 总被引：4，自引：1，他引：4
MARKL GREGOR; MARKS MICHAEL; SCHWINN GREGOR; SOMMER HOLGER 《Journal of Petrology》2001,42(12):2231-2257
The 1·13 Ga Ilímaussaq intrusive complex, SouthGreenland, is composed of various types of alkali granite andsilica-undersaturated alkaline to agpaitic nepheline syenitesrelated to three subsequently intruded magma batches. Mineralchemistry indicates continuous fractionation trends within eachrock type, but with distinct differences among them. The last,peralkaline magma batch is the most fractionated in terms ofXFemafic mineral, feldspar composition and mineral assemblage.This indicates that an evolving magma chamber at depth discontinuouslyreleased more highly fractionated alkaline melts. Fluid inclusionsin some sodalites record a pressure drop from 3·5 to1 kbar indicating that crystallization started during magmaascent and continued in the high-level magma chamber. On thebasis of phase equilibria and preliminary fluid inclusion data,crystallization temperature drops from >1000°C (augitesyenite liquidus) to <500°C (lujavrite solidus) and silicaactivity decreases from 相似文献
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LESZEK LINDNER LESZEK MARKS KAZIMIERZ PEKALA 《Boreas: An International Journal of Quaternary Research》1984,13(1):35-47
On the basis of field and laboratory studies supported by thermoluminescence dates, an occurrence of marine and glacial sediments is described from South Spitsbergen. These deposits are thought to date from the Holsteinian interglacial and the Saalian glacial stages respectively. In addition, the evidence and extent of Vistulian and Holoccne glacial advances in South Spitsbergen are presented. These advances occurred at 50,000–43,000, 30,000–10,000, 3,000–2,500 and 600–100 years B.P. The latter have been tentatively correlated with those recorded in other parts of Svalbard, as well as in East Greenland, the Barents Sea, Scandinavia, the Baltic Sea, North Poland and the Russian Plain. 相似文献
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MARKS MICHAEL; VENNEMANN TORSTEN; SIEBEL WOLFGANG; MARKL GREGOR 《Journal of Petrology》2003,44(7):1247-1280
The Puklen complex of the Mid-Proterozoic Gardar Province, SouthGreenland, consists of various silica-saturated to quartz-bearingsyenites, which are intruded by a peralkaline granite. The primarymafic minerals in the syenites are augite ± olivine +Fe–Ti oxide + amphibole. Ternary feldspar thermometryand phase equilibria among mafic silicates yield T = 950–750°C,aSiO2 = 0·7–1 and an fO2 of 1–3 log unitsbelow the fayalite–magnetite–quartz (FMQ) bufferat 1 kbar. In the granites, the primary mafic minerals are ilmeniteand Li-bearing arfvedsonite, which crystallized at temperaturesbelow 750°C and at fO2 values around the FMQ buffer. Inboth rock types, a secondary post-magmatic assemblage overprintsthe primary magmatic phases. In syenites, primary Ca-bearingminerals are replaced by Na-rich minerals such as aegirine–augiteand albite, resulting in the release of Ca. Accordingly, secondaryminerals include ferro-actinolite, (calcite–siderite)ss,titanite and andradite in equilibrium with the Na-rich minerals.Phase equilibria indicate that formation of these minerals tookplace over a long temperature interval from near-magmatic temperaturesdown to 相似文献
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VINCENT R. RINTERKNECHT LESZEK MARKS JAN A. PIOTROWSKI GRANT M. RAISBECK FRANÇOISE YIOU EDWARD J. BROOK PETER U. CLARK 《Boreas: An International Journal of Quaternary Research》2005,34(2):186-191
Rinterknecht, V. R., Marks, L., Piotrowski, J. A., Raisbeck, G. M., Yiou, F., Brook, E. J. & Clark, P. U. 2005 (May): Cosmogenic 10 Be ages on the Pomeranian Moraine, Poland. Boreas , Vol. 34, pp. 186–191. Oslo. ISSN 0300–9483.
We measured the10 Be concentrations in boulders collected from the Pomeranian Moraine in Poland, providing the first direct dating of the southern margin of the Scandinavian Ice Sheet (SIS) in the Polish Lowland. The mean age of 8 10 Be ages of the Pomeranian Moraine in northwestern Poland is 14.30.8 10 Be ka, while in northeastern Poland the mean age of 19 10 Be ages of the moraine is 15.00.5 10 Be ka. Given the excellent agreement between the two age groups, we calculate a mean age of 14.80.4 10 Be ka for final deposition of the Pomeranian Moraine of northern Poland. The age of the Pomeranian Moraine suggests that the southern margin of the SIS was near its maximum extent in Poland at a younger time than previously inferred, and that retreat from the moraine at 14.80.4 10 Be ka probably occurred in response to the onset of the Bølling interstade. 相似文献
We measured the
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The early augite syenite unit in the 1·13-Ga-old Ilímaussaqintrusive complex, South Greenland, consists of a magmatic assemblageof ternary alkali feldspar + fayalitic olivine + augite + titanomagnetite+ apatite + baddeleyite ± nepheline ± quartz ±ilmenite ± zircon. Feldspar, nepheline and QUILF thermometryyield T = 1000–700°C, at P = 1 kbar, which is derivedfrom fluid inclusion data from other parts of the complex. Ternaryfeldspar was the first major liquidus phase. It crystallizedat temperatures between 950 and 1000°C from a homogeneousmagma with aSiO2 = 0·8 and fO2 about 1·5–2log units below the fayalite–magnetite–quartz (FMQ)buffer. Later, closed system fractionation produced nepheline-bearingassemblages with aSiO2 = 0·4 and log fO2 = FMQ –3 to FMQ – 5. Assimilation of wall rocks produced localvariations of melt composition. Four traverses through the unitwere sampled parallel to the assumed direction of crystallization.They exhibit significant differences in their mineral assemblagesand compositions. The chemical zoning and calculated intensiveparameters of four sample suites reflect both closed systemfractional crystallization and local assimilation of wall rocks. KEY WORDS: alkaline magmatism; assimilation; fractionation; redox equilibria; QUILF 相似文献
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LESZEK LINDNER LESZEK MARKS 《Boreas: An International Journal of Quaternary Research》1985,14(2):139-153
A proposal for the classification of accumulations formed at the foot of mountain slopes and glacier snouts is presented for South Spitsbergen. Simple (talus cones) and complex (protalus ramparts, protalus rock glaciers, moraine rock glaciers) landforms are distinguished. The homogeneity of the features deposited at the foot of mountain slopes on a bedrock as well as on a glacial ice is noted, although the latter are more easily destructed due to melting of the buried ice. A significance of the ice core (interstitial or glacial ice) for a development of protalus rock glaciers and moraine rock glaciers is emphasized. 相似文献
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LESZEK MARKS IRINA E. PAVLOVSKAYA 《Boreas: An International Journal of Quaternary Research》2003,32(2):337-346
The Holsteinian drainage system in mid-eastern Poland and western Belarus has been reconstructed using palaeogeographical analysis based on abundant boreholes. The stratigraphic setting and palaeogeography are determined by correlation with Holsteinian marine sediments in the Kaliningrad District of Russia and the Late Elsterian glaciolacustrine series in the southern peribaltic region. At the beginning of the Holsteinian there were numerous residual overflow lakes at the Polish-Belarusian border area that gradually became interconnected with the Holsteinian Neman River and its tributaries. The base level of erosion is located in river beds of Holsteinian valleys slightly beneath beds of the recent rivers and indicates that Holsteinian sea level was apparently lower than the present Baltic Sea level. The Holsteinian Neman flowed southwestwards across the Biebrza River Basin to the Warsaw Basin. The main watershed between the Baltic Sea and the Black Sea was further to the west than its present location. The secondary watershed in northern Poland has only been slightly modified since that time. 相似文献
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We used the landscape model PAYSAGE to demonstrate the use of GIS and simulation models for ecosystem management over a portion of Mitkof Island in the Tongass National Forest. The objectives of the study were to: 1) depict the natural heterogeneity in environment and resource distributions across the study area; 2) quantify changes in vegetation and vertebrate habitats (brown creeper, orange-crowned warbler, marten) during the period of commercial timber harvest (1954 to the present); and 3) simulate likely long-term changes in vegetation and vertebrate habitat under three management scenarios – the Tongass Forest Plan, the wildlife habitat conservation strategy, and the Pacific Fisheries Task Force strategy. The results indicated that productive forest lands and vertebrate habitats are naturally patchy in the study area due to topography and climate. This natural fragmentation was exacerbated by past logging, which targeted high-productivity old growth stands. This stand type was reduced in area by 76 per cent from 1954 to 1994. Patch density and mean patch size decreased during this time while mean nearest neighbour distance increased. Simulations of the three management scenarios for a 200-year period projected relatively minor differences in landscape patterns among the scenarios. This is because the forest plan scenario is relatively restrictive in timber harvest and because most of the area protected in the other two scenarios does nor currently support old growth. We discuss the role of decision-support tools such as PAYSAGE in adaptive ecosystem management and evaluate limitations of the model. 相似文献
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