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Number of results: 28
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Abstract

The Marhřgda Bed occurring at base of the Adventdalen Group in Sassenfjorden, Spitsbergen contains common ankerite–replaced belemnite skeletons. Petrographic, major element geochemical, and stable carbon and oxygen isotopic data indicate that the ankerite originated in a catagenic environment associated with thermal degradation of kerogenan d hydrocarbongen erationinthe sequence. It formed at maximum temperature of 150°C under burial of approx. 2 000 m, most probably during Paleogene filling and subsidence of the Central Spitsbergen Basin. Dissolution of biogenic calcite and precipitation of ankerite reflect extensive heat flow through the Adventdalen Group sequence related to the Cretaceous and Paleogene magmatic and orogenic activity in Svalbard.
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Abstract

Diagenetic carbonate deposits (concretions, cementation bodies and cementstone bands) commonly occur in organic carbon-rich sequence of the Agardhfjellet Formation (Upper Jurassic) in Spitsbergen . They are dominated by dolomite/ankerite and siderite. These deposits originated as a result of displacive cementation of host sediment in a range of post-depositional environments, from shallow subsurface to deep-burial ones. Preliminary results of the carbon and oxygen isotopic survey of these deposits in southern Spitsbergen (Lĺgkollane, Ingebrigtsenbukta, Reinodden, and Lidfjellet sections) show the δ13C values ranging between –13.0‰ and –1.8‰ VPDB, and the δ18O values between –16.0‰ and –7.7‰ VPDB. These results suggest that the major stage of formation of the carbonate deposits occurred during burial diagenesis under increased temperature, most probably in late diagenetic to early catagenic environments. Carbonate carbon for mineral precipitation was derived from dissolution of skeletal carbonate and from thermal decomposition of organic matter.
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Abstract

The organic carbon (OC)-rich, black shale succession of the Middle Triassic Bravaisberget Formation in Spitsbergen contains scattered dolomite-ankerite cement in coarser-grained beds and intervals. This cement shows growth-related compositional trend from non-ferroan dolomite (0–5 mol % FeCO3) through ferroan dolomite (5–10 mol % FeCO3) to ankerite (10–20 mol % FeCO3, up to 1.7 mol % MnCO3) that is manifested by zoned nature of composite carbonate crystals. The d13C (-7.3‰ to -1.8‰ VPDB) and d18O (-9.4‰ to -6.0‰ VPDB) values are typical for burial cements originated from mixed inorganic and organic carbonate sources. The dolomite-ankerite cement formed over a range of diagenetic and burial environments, from early post-sulphidic to early catagenic. It reflects evolution of intraformational, compaction-derived marine fluids that was affected by dissolution of biogenic carbonate, clay mineral and iron oxide transformations, and thermal decomposition of organic carbon (decarboxylation of organic acids, kerogen breakdown). These processes operated during Late Triassic and post-Triassic burial history over a temperature range from approx. 40°C to more than 100°C, and contributed to the final stage of cementation of the primary pore space of siltstone and sandstone beds and intervals in the OC-rich succession.
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Abstract

Ball-shaped concretions ("cannon balls") commonly occur in a marine, organic carbon-rich sedimentary sequence (Innkjegla Member) of the Carolinefjellet Formation (AptianAlbian) in Spitsbergen. The sedimentologic, petrographic and geochemical investigation of these concretions in the Kapp Morton section at Van Mijenfjorden gives insight into their origin and diagenetic evolution. The concretion bodies commenced to form in subsurface environment in the upper part of the sulphate reduction (SR) diagenetic zone. They resulted from pervasive cementation of uncompacted sediment enriched in framboidal pyrite by non-ferroan (up to 2 mol% FeCO3) calcite microspar at local sites of enhanced decomposition of organic matter. Bacterial oxidation of organic matter provided most of carbon dioxide necessary for concretionary calcite precipitation (δ13CCaCO3 ≈ -21%VPDB). Perfect ball-like shapes of the concretions originated at this stage, reflecting isotropic permeability of uncompacted sediment. The concretion bodies cracked under continuous burial as a result of amplification of stress around concretions in a more plastic sediment. The crack systems were filled by non-ferroan (up to 5 mol% FeCO3) calcite spar and blocky pyrite in deeper parts of the SR-zone. This cementation was associated with impregnation of parts of the concretion bodies with microgranular pyrite. Bacterial oxidation of organic matter was still the major source of carbon dioxide for crack-filling calcite precipitation (δ13CCaCO3 ≈ -19% VPDB). At this stage, the cannon-ball concretions attained their final shape and texture. Subsequent stages of concretion evolution involved burial cementation of rudimentary pore space with carbonate minerals (dolomite/ankerite, siderite, calcite) under increased temperature (δ18OCa,Mg,FeCO3 ≈-14% VPDB). Carbon dioxide for mineral precipitation was derived from thermal degradation of organic matter and from dissolution of skeletal carbonates (δ13CCa,Mg,FeCO3≈ - 8‰ VPDB). Kaolinite cement precipitated as the last diagenetic mineral, most probably during post−Early Cretaceous uplift of the sequence.
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Abstract

The Lidfjellet thrust is the most prominent tectonic structure in the Lidfjellet-Řyrlandsodden fold zone, which stretches NNW-SSE along the western coast of Sřrkapp Land in Spitsbergen. This paper provides a reinterpretation of the Lidfjellet structure, with particular reference to lithostratigraphy of the autochthonous and overthrust sequences involved, and to the position of the thrust surface. Geological and palynologicalal data indicate that the sequence attributed previously to the Lower Cretaceous Helvetiafjellet Formation of the autochthonous cover represents in fact the Carboniferous (Viséan) Sergeijevfjellet Formation forming the lower part of the overthrust unit. The youngest deposits involved in tectonic structures of the Lidfjellet-Řyrlandsodden fold zone are of Upper Jurassic age.
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Abstract

The subject of the paper is structural stability of the Zn-26 wt.% Al binary alloys doped with 2.2 wt.% Cu or 1.6 wt.% Ti addition. The structural stability of Zn-Al alloys with increased Al content is connected with stability of solid solution of zinc in aluminium α', which is the main component of these alloys microstructure. Such a solution undergoes phase transformations which are accompanied, among others, by changes in dimensions and strength properties. The structural stability of the ZnAL26Cu2.2 and ZnAl26Ti1.6 alloys was investigated using XRD examinations during long term natural ageing after casting, as well as during long term natural ageing after super-saturation and quenching. On the basis of the performed examinations it was stated that small Ti addition to the binary ZnAl25 alloy, apart from structure refinement, accelerates decomposition of the primary α' phase giving stable structure in a shorter period of time in comparison with the alloy without Ti addition. Addition of Ti in amount of 1.6 wt.%, totally replacing Cu, allows obtaining stable structure and dimensions and allows avoiding structural instability caused by the metastable ε−CuZn4 phase present in the ZnAl26Cu2.2 alloy.
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Abstract

Nine samples of basic (dolerite, gabbro) intrusions collected at Bellsund, South Spitsbergen, have been K−Ar dated. Three dates, between 87.8 and 102.9 Ma, obtained from dolerite sills which intrude Carboniferous and Permian deposits in Van Keulenfjorden point to a Cretaceous age of intrusive activity (Diabasodden Suite). The K−Ar dates obtained from dolerite and gabbro which intrude Upper Proterozoic metasedimentary terrane of Chamber− lindalen form two groups: the dates between 97.1 and 178.6 Ma point to a Mesozoic age of the intrusions (Diabasodden Suite); the dates from a tectonized gabbroid (280.9–402.0 Ma) might point to a Late Palaeozoic age of the intrusion. No K−Ar dates which would indicate a Proterozoic age of the basic intrusions were obtained
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Abstract

The Bravaisberget Formation in Spitsbergen embraces an organic carbon-rich, clastic sequence that reflects a general shallow shelf development of the Middle Triassic depositional system in Svalbard . New observations and measurements of the type section of the formation at Bravaisberget in western Nathorst Land allow to present detailed lithostratigraphical subdivision of the formation, and aid to reconstruct its depositional history. The subdivision of the formation ( 209 m thick at type section) into the Passhatten, Somovbreen, and Van Keulenfjorden members is sustained after Mørk et al. (1999), though with new position of the boundary between the Passhatten and Somovbreen mbs. The Passhatten Mb is defined to embrace the black shale-dominated sequence that forms the lower and middle parts of the formation ( 160 m thick). The Somovbreen Mb ( 20 m thick) is confined to the overlying, calcite-cemented sequence of marine sandstones. The Van Keulenfjorden Mb ( 29 m thick) forms the topmost part of the formation composed of siliceous and dolomitic sandstones. The formation is subdivided into twelve informal units, out of which eight is defined in the Passhatten Mb (units 1 to 8), two in the Somovbreen Mb (units 9 and 10), and also two in the Van Keulenfjorden Mb (units 11 and 12). Units 1, 3, 5, 7 and 9 contain noticeable to abundant phosphorite, and are interspaced by four black shale sequences (units 2, 4, 6, and 8). Unit 9 passes upwards gradually into the main sandstone sequence (unit 10) of the Somovbreen Mb. The base of the Van Keulenfjorden Mb is a discontinuity surface covered by thin phosphorite lag. The Van Keulenfjorden Mb consists of two superimposed sandstone units (units 11 and 12) that form indistinct coarsening-upward sequences. The Bravaisberget Fm records two consequent transgressive pulses that introduced high biological productivity conditions to the shelf basin. The Passhatten Mb shows pronounced repetition of sediment types resulting from interplay between organic-prone, fine-grained environments, and clastic bar environments that focused phosphogenesis. The lower part of the member (units 1 to 5) contains well-developed bar top sequences with abundant nodular phosphorite, which are under- and overlain by the bar side sequences grading into silt- to mud-shale. The upper part of the member (units 6 to 8) is dominated by mud-shale, showing the bar top to side sequence with recurrent phosphatic grainstones in its middle part. Maximum stagnation and deep-water conditions occurred during deposition of the topmost shale sequence (unit 8). Rapid shallowing trend terminated organic-rich environments of the Passhatten Mb, and was associated with enhanced phosphogenesis at base of the Somovbreen Mb (unit 9). Bioturbated sandstones of the Somovbreen Mb (unit 10) record progradation of shallow-marine clastic environments. The sequence of the Van Keulenfjorden Mb (units 11 and 12) was deposited in brackish environments reflecting closure of the Middle Triassic basin in western Svalbard .
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Abstract

The paper is devoted to grain-refinement of the medium-aluminium zinc based alloys (MAl-Zn). The system examined was sand cast Zn10 wt. %. Al binary alloy (Zn-10Al) doped with commercial Al-3 wt. % Ti – 0.15 wt. % C grain refiner (Al-3Ti-0.15C GR). Basing on the measured attenuation coefficient of ultrasonic wave it was stated that together with significantly increased structure fineness damping decreases only by about 10 – 20%. The following examinations should establish the influence of the mentioned grain-refinement on strength and ductility of MAl-Zn cast alloys.
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Abstract

The paper presents results of measuring attenuation coefficient of the Al-20 wt.% Zn alloy (AlZn20) inoculated with different grain refiners. During experiments the melted alloys were doped with Al-Ti3-C0.15 refining master alloy. Basing on measurements performed by Krautkramer USLT2000 device with 1MHz ultrasound wave frequency it was stated that grain refinement reduces the attenuation coefficient by about 20-25%. However, the examined alloys can be still classified as the high-damping ones of attenuation greater than 150 dB/m.
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Abstract

The paper presents relationships between the degree of structure fineness and feeding quality of the Al – 20 wt.% Zn (Al-20 Zn) alloy cast into a mould made from sand containing silica quartz as a matrix and bentonite as a binder, and its damping coefficient of the ultrasound wave at frequency of 1 MHz. The structure of the examined alloy was grain refined by the addition of the refining Al-3 wt.% Ti – 0.15 wt.%C (TiCAl) master alloy. The macrostructure analysis of the initial alloy without the addition of Ti and the alloy doped with 50-100 ppm Ti as well as results of damping experiments showed that the structure of the modified alloy is significantly refined. At the same time, its damping coefficient decreases by about 20-25%; however, it still belongs to the so called high-damping alloys. Additionally, it was found that despite of using high purity metals Al and Zn (minimum 99,99% purity), differences in the damping coefficient for samples cut from upper and bottom parts of the vertically cast rolls were observed. These differences are connected with the insufficient feeding process leading to shrinkage porosity as well as gases present in metal charges which are responsible for bubbles of gas-porosity.
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Abstract

Radiometric and geochemical studies were carried out at Red Hill in the southern part of King George Island (South Shetland Islands, northern Antarctic Peninsula) on the Bransfield Strait coast. The rock succession at Red Hill has been determined to represent the Baranowski Glacier Group that was previously assigned a Late Cretaceous age. Two formations were distinguished within this succession: the lower Llano Point Formation and the upper Zamek Formation. These formations have stratotypes defined further to the north on the western coast of Admiralty Bay. On Red Hill the Llano Point Formation consists of terrestrial lavas and pyroclastic breccia; the Zamek Formation consist predominantly of fine to coarse tuff, pyroclastic breccia, lavas, tuffaceous mud− , silt−, and sandstone, locally conglomeratic. The lower part of the Zamek Formation contains plant detritus (Nothofagus , dicotyledonous, thermophilous ferns) and numerous coal seams (vitrinitic composition) that confirm the abundance of vegetation on stratovolcanic slopes and surrounding lowlands at that time. Selected basic to intermediate igneous rocks from the succession have been analysed for the whole−rock K−Ar age determination. The obtained results indicate that the Red Hill succession was formed in two stages: (1) from about 51–50 Ma; and (2) 46–42 Ma, i.e. during the Early to Middle Eocene. This, in combination with other data obtained from other Baranowski Glacier Group exposures on western coast of Admiralty Bay, confirms the recently defined position of the volcano−clastic succession in the stratigraphic scheme of King George Island. The new stratigraphic position and lithofacies development of the Red Hill succession strongly suggest its correlation with other Eocene formations containing fossil plants and coal seams that commonly occur on King George Island.
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Abstract

The paper presents results of measuring heat diffusivity and thermal conductivity coefficients of used green foundry sand in temperature range ambient – 600 o C. During the experiments a technical purity Cu plate was cast into the green-sand moulds. Basing on measurements of the mould temperature field during the solidification of the casting, the temperature relationships of the measured properties were evaluated. It was confirmed that the obtained relationships are complex and that water vaporization strongly influences thermal conductivity of the moulding sand in the first period of the mould heating by the poured and solidified casting
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Abstract

The Panorama Point Beds represent a subfacies of the Early to Middle Permian Radok Conglomerate, which is the oldest known sedimentary unit in the Prince Charles Mountains, MacRobertson Land, East Antarctica. This unit records clastic sedimentation in fresh−water depositional system during the early stages of development of the Lambert Graben, a major structural valley surrounded by crystalline highlands in the southern part of Gondwana. It contains common siderite precipitated through early diagenetic processes in the swamp, stagnant water, and stream−flow environments. There are two types of siderite in the Panorama Point Beds: (1) disseminated cement that occurs throughout the sedimentary suc− cession; and (2) concretions that occur at recurrent horizons in fine−grained sediments. The cement is composed of Fe−depleted siderite (less than 90mol%FeCO3)with an elevated con− tent of magnesium, and trace and rare earth elements. It has negative #2;13CVPDB values (−4.5 to −1.5‰). The concretions are dominated by Fe−rich siderite (more than 90mol% FeCO3),with positive 13CVPDB values (+1 to +8‰). There are no noticeable differences in the oxygen (18OVPDB between −20 and −15‰) and strontium (87Sr/86Sr between 0.7271 and 0.7281) iso− topic compositions between the siderite types. The cement and concretions developed in the nearsurface to subsurface environment dominated by suboxic and anoxic methanic degrada− tion of organic matter, respectively. The common presence of siderite in the Panorama Point Beds suggests that fresh−water environments of the Lambert Graben were covered by vegetation, starting from the early history of its development in the Early Permian.
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Abstract

The Marhegda Bed is a carbonate-dominated Uthostratigraphic unit occurring locally at base of the Middle-Late Jurassic organic-rich sequence of the Agardhfjellet Formation in Spitsbergen, Svalbard. It has been interpreted to represent oolitic limestone facies deposited during an initial stage of Late Jurassic transgression. Petrographic, major element geochemical, and stable carbon and oxygen isotopic data presented in this paper indicate that this litho-stratigraphic unit is not a depositional limestone, but a diagenetic cementstone band originated in organic-rich sediment containing glauconite pellets and phosphatic ooids and grains. Two ep­isodes of carbonate diagenesis, including early precipitation of siderite and burial precipitation of ankerite, have contributed to the development of this cementstone. Extensive siderite precipi­tation occurred at sedimentary temperatures in nearsurface suboxic environment in which microbial reduction of ferric iron was the dominant diagenetic process. Precipitation of ankerite occurred at temperatures of about 80-100°C in burial diagenetic environment overwhelmed by thermal decarboxylation processes. Formation of ankerite was associated with advanced alteration of glauconite, dissolution of apatite and precipitation of kaolinite.
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Abstract

One of the most significant global climatic events in the Cenozoic was the transition from greenhouse to icehouse conditions in Antarctica. Tectonic evolution of the region and gradual cooling at the end of Eocene led to the first appearance of ice sheets at the Eocene/Oligocene boundary (ca. 34 Ma). Here we report geological record of mountain glaciers that preceded major ice sheet formation in Antarctica. A terrestrial, valley-type tillite up to 65 metres thick was revealed between two basaltic lava sequences in the Eocene– Oligocene Point Thomas Formation at Hervé Cove – Breccia Crag in Admiralty Bay, King George Island, South Shetland Islands. K-Ar dating of the lavas suggests the age of the glaciation at 45–41 Ma (Middle Eocene). It is the oldest Cenozoic record of alpine glaciers in West Antarctica, providing insight into the onset of glaciation of the Antarctic Peninsula and South Shetland Islands.
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Abstract

The paper presents results of measuring thermal conductivity and heat capacity of bentonite foundry sand in temperature range ambient – 900 OC. During the experiments a technical purity Cu plate was cast into the green-sand moulds. Basing on measurements of the mould temperature field during the solidification of the casting, the temperature relationships of the measured properties were evaluated. It was confirmed that water vaporization strongly influences thermal conductivity of the moulding sand in the first period of the mould heating by the poured casting.
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Abstract

The subject of this study is the presentation of relation between the degree of structure fineness and ultrasonic wave damping coefficient for the high-zinc aluminium alloys represented in this study by the sand mould cast alloy Al - 20 wt% Zn (AlZn20). The studied alloy was refined with a modifying (Al,Zn)-Ti3 ternary master alloy, introducing Ti in the amount of 400 pm into metal. Based on the analysis of the initial and modified alloy macrostructure images and ultrasonic testing, it was found that the addition of (Al,Zn)-Ti3 master alloy, alongside a significant fragmentation of grains, does not reduce the coefficient of ultrasonic waves with a frequency of 1 MHz.
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