scholarly journals The geochemistry of the northern part of the Ilímaussaq intrusion, S.W. Greenland

1964 ◽  
Vol 42 ◽  
pp. 1-104
Author(s):  
E.I Hamilton
Keyword(s):  
Central Area ◽  
Confining Pressure ◽  
Coarse Grained ◽  
Residual Liquid ◽  
Relative Time ◽  
Central Mass ◽  
Basement Rocks ◽  
Field Evidence ◽  
Show Evidence ◽  
High Level

The Ilímaussaq intrusion (S.W. Greenland) was emplaced into granitic Precambrian basement rocks. The intrusion is of a highly alkaline nature and in terms of rocks types, its major-, minor- and trace elements, may be compared to the Khibina-Lovozero intrusion of the Kola Peninsula, U.S.S.R. The present paper describes the geochemistry of the northern part of the intrusion and the marginal rocks. New total rock analyses are given together with the detailed geochemistry of U, Th, Radioactivity, Nb, Rb, Li and Be. The Ilímaussaq intrusion consists of an early augite syenite chilled against the country rocks. The augite syenite forms a more or less continuous ring around and above the intrusion. The main central mass of the intrusion consists of poorly layered, very coarse-grained, Na-rich "foyaite" containing relatively large amounts of sodalite and eudialyte. Differentiation of the "foyaite magma" gave rise to a volatile rich residual liquid from which lujavrites were formed. Differentiation of the lujavrites in the central area of the intrusion resulted in a lower banded sequence, the kakortokites, and an upper lujavrite liquid. When the confining pressure was exceeded, explosive brecciation occurred and lujavrite was intruded into the surrounding rocks. At a high level in the intrusion a sheet-like body of soda granite was emplaced together with various quart-bearing syenites. The relative time of intrusion of the quartz-bearing syenite is uncertain through lack of field evidence. Emplacement of the early augite syenite may be related to ring faulting followed by cauldron subsidence. The later Na-rich rocks may have replaced the earlier layered augite syenite or have been emplaced into a "magma chamber" developed by cauldron subsidence. The Na-Zr-Cl-rich rocks show evidence of cooling inwards with the development of a central volatile-rich pocket. The Ilímaussaq rocks probably represent a final highly fractionated stage of the more normal augite syenite magma common to the S. W. Greenland alkaline province.

scholarly journals Environmental Sustainability and Economic Growth in Greenland: Testing the Environmental Kuznets Curve

2021 ◽  
Vol 13 (3) ◽  
pp. 1228
Author(s):  
Javier Arnaut ◽  
Johanna Lidman
Keyword(s):  
Environmental Sustainability ◽  
Environmental Kuznets Curve ◽  
Development Stage ◽  
The Arctic ◽  
Kuznets Curve ◽  
Distributed Lag ◽  
Show Evidence ◽  
Per Capita ◽  
Growing Economy ◽  
High Level

The environmental Kuznets curve (EKC) hypothesis assumes there is an inverted U-shape relationship between pollution and income per capita, implying an improvement in environmental quality when a growing economy reaches a high level of economic development. This study evaluated empirically the existence of the environmental Kuznets curve in Greenland for the period 1970–2018. Using an autoregressive distributed lag (ARDL) approach, the results show evidence of a U-shaped EKC in Greenland instead of the hypothesized inverted U-shape. The findings indicate that Greenland had initially experienced a decoupling transition during an early development stage associated with structural conditions of a small subsistence economy. However, once the country began to expand its industry, the trend began to reverse, creating a positive and significant relationship between CO2 emissions and GDP per capita that is potentially detrimental to the Arctic natural environment.

Field evidence for coal combustion links the 252 My-old Siberian Traps with global carbon disruption

2021 ◽  
Author(s):  
Linda Elkins-Tanton ◽  
Steven Grasby ◽  
Benjamin Black ◽  
Roman Veselovskiy ◽  
Omid Ardakani ◽  
...  
Keyword(s):  
Organic Matter ◽  
Carbon Isotope ◽  
Flood Basalts ◽  
Siberian Traps ◽  
Field Evidence ◽  
Carbon Isotope Excursion ◽  
Show Evidence ◽  
Volcaniclastic Rocks ◽  
Atmospheric Changes ◽  
Global Carbon

<p>The Permo-Triassic Extinction was the most severe in Earth history. The Siberian Traps eruptions are strongly implicated in the global atmospheric changes that likely drove the extinction. A sharp negative carbon isotope excursion coincides within geochronological uncertainty with the oldest dated rocks from the Norilsk section of the Siberian flood basalts. The source of this light carbon has been debated for decades.</p><p>We focused on the voluminous volcaniclastic rocks of the Siberian Traps, relatively unstudied as potential carriers of carbon-bearing gases. Over six field seasons we collected rocks from across the Siberian platform and show the first direct evidence that the earliest eruptions particularly in the southern part of the province burned large volumes of a combination of vegetation and coal. Samples from the Maymecha-Kotuy region, from the Nizhnyaya Tunguska, Podkamennaya Tunguska, and Angara Rivers all show evidence of high-temperature organic matter carbonization and combustion.</p><p>Field evidence indicates a process in which ascending magmas entrain xenoliths of coal and carbonaceous sediments that are carbonized in the subsurface and also combusted either through reduction of magmas or when exposed to the atmosphere. We demonstrate that the volume and composition of organic matter interactions with magmas may explain the global carbon isotope signal, and have significantly driven the extinction.</p>

Geochronology of the Belt Series, Montana

1968 ◽  
Vol 5 (3) ◽  
pp. 737-747 ◽  
Author(s):  
J. D. Obradovich ◽  
Z. E. Peterman
Keyword(s):  
Average Rate ◽  
Sedimentary Rocks ◽  
Time Interval ◽  
Depositional History ◽  
Middle Cambrian ◽  
Basement Rocks ◽  
Field Evidence ◽  
Minimum Age ◽  
History Of ◽  
Central Montana

This paper presents new radiometric data that permit some qualified statements to be made on the depositional history of the Belt sedimentary rocks. The period of deposition of sedimentary rocks of the Precambrian Belt Series has been placed within a broad time interval, for they rest on metamorphosed basement rock dated at ~ 1800 m.y. and are overlain by the Middle Cambrian Flathead Quartzite (circa 530 m.y.). Prior geochronometric data gathered during the last decade indicate most of the Belt Series to be older than ~ 1100 m.y.K–Ar and Rb–Sr techniques have been applied recently to a variety of samples selected from the whole gamut of the Belt Series. Glauconite from various formations in the sequence McNamara Formation down to the uppermost beds of the Empire Formation in the Sun River area has been dated at 1080 ± 27 m.y. by the K–Ar method and at 1095 ± 22 m.y. by the Rb–Sr mineral isochron method. A Rb–Sr whole-rock isochron based on argillaceous sedimentary rocks from this 5000-ft section gives an age of 1100 ± 53 m.y. The concordance of the preceding results and the K–Ar ages (1075 to 1110 m.y.) on Purcell sills and lava imply that this age represents the time of sedimentation of these units.A Rb–Sr isochron based on whole-rock samples stratigraphically far below the Umpire Formation— the Greyson Shale, Newland Limestone, Chamberlain Shale, and Neihart Quartzite in the Big Belt and Little Beit Mountains—yields an age of 1325 ± 15 m.y. This result is interpreted as indicating a substantial unconformity beneath the Belt Series, at least in central Montana; it also suggests a major hiatus, unsuspected from field evidence, between the uppermost part of the Empire Formation and the Greyson Shale.The results for the youngest of Belt rocks—the Pilcher Quartzite and the Garnet Range Formation, which are exposed in the Alberton region—are equivocal in that there is widespread dispersion. A large component of detrital muscovite in some of the samples could readily account for the magnitude and sense of this dispersion. A maximum age of ~930 m.y. based on an isochron of minimum slope through the various points may be inferred for this sequence. A K–Ar age of 760 m.y. obtained on biotite from a sill in the Garnet Range Formation provides a minimum age for these younger Belt rocks.Three distinct periods of sedimentation for Belt rocks sampled are suggested at ≥ 1300, 1100, and ≤ 900 m.y., with two substantial hiatuses of 200 m.y. or more. In addition the data for the sequence in the Big and Little Belt Mountains suggest that sedimentation may not have commenced for a period of possibly 400 m.y. after the metamorphism that affected basement rocks, while the data for the Garnet Range and Pilcher sequence suggest that sedimentation ceased some 200 to 400 m.y. prior to the deposition of the Middle Cambrian Flathead Quartzite.To suggest that the Belt sediments were deposited continuously over a period of 400 m.y. or more would imply an unusually low average rate of deposition of ≤ 0.1 ft/1000 yr, and this for the thickest part of the Belt Series. As a realistic expression of the depositional history of the Belt Series, both viewpoints are open to question, but the viewpoint that the Belt basin has been characterized by discontinuous sedimentation would be more in keeping with the principle of uniformity.

Mineralogy of vesicles in an olivine leucitite at Cosgrove, Victoria, Australia

1980 ◽  
Vol 43 (329) ◽  
pp. 597-603 ◽  
Author(s):  
W. D. Birch
Keyword(s):  
Late Stage ◽  
Rock Type ◽  
Early Stage ◽  
Coarse Grained ◽  
Residual Liquid ◽  
Cooling History ◽  
History Of

SummaryAn olivine-titanomagnetite-apatite-clinopyroxene-mica-nepheline-feldspar assemblage occurs in late-stage vesicles in a small outcrop of olivine leucitite at Cosgrove, Victoria. The vesicles were formed by exsolution of volatiles at an early stage in the cooling history of the lava. Subsequently, a volatile-rich residual liquid filled cavities and fractures, giving rise to a coarse-grained pegmatoid rock type similar in over-all mineralogy to the vesicles. The volatiles facilitating crystallization in both the vesicles and the pegmatoid were probably enriched in F, CO2, and P. A number of geothermometers applied to the vesicle assemblage failed to agree on likely crystallization temperatures.

scholarly journals New Structure for Strengthening Soil Embankments

2018 ◽  
Vol 2018 ◽  
pp. 1-16
Author(s):  
Fang Xu ◽  
Wuming Leng ◽  
Rusong Nie ◽  
Qishu Zhang ◽  
Qi Yang
Keyword(s):  
Shear Modulus ◽  
Large Scale ◽  
Dynamic Stress ◽  
Confining Pressure ◽  
Coarse Grained ◽  
Triaxial Tests ◽  
Additional Stress ◽  
Dynamic Shear Modulus ◽  
Dynamic Shear ◽  
Critical Dynamic

A new prestressed reinforcement device (PRD) consisting of two lateral pressure plates (LPPs) and a reinforcement bar is developed to strengthen soil embankments by improving the soil confining pressure and providing lateral constraint on embankment slopes. The reinforcement effects of PRDs were demonstrated by investigating the beneficial effects of increasing confining pressure on the soil behavior via the performance of a series of large-scale static and cyclic triaxial tests on a coarse-grained embankment soil. The results show that PRDs can effectively improve the soil shear strength, bearing capacity, ability to resist elastic and plastic deformation, critical dynamic stress, and dynamic shear modulus, and empirical methods were also developed to determine the critical dynamic stress and initial dynamic shear modulus of the embankment soil. Moreover, 3D finite element analyses (FEAs) with an LPP width of 1.2 m were performed to analyze the additional stress field in a prestressed heavy-haul railway embankment. The FEAs showed that the additional stress at a given external distance from the border of an LPP first increased to a maximum value and then gradually decreased with increasing depth; the additional stress was transferred to the zones where the subgrade tends to have higher stresses with peak stress diffusion angles of 34° (slope direction) and 27° (longitudinal direction); and a continuous effective reinforcement zone with a minimum additional stress coefficient of approximately 0.2 was likely to form at the diffusion surface of the train loads, provided that the net spacing of the LPPs was 0.7 m. The reinforcement zone above the diffusion surface of the train loads can act as a protective layer for the zones that tend to have higher stresses. Finally, the advantages and application prospects of PRDs are discussed in detail. The newly developed PRDs may provide a cost-effective alternative for strengthening soil embankments.

Determination of the characteristics of crystalline rocks by field experiments: a review

1986 ◽  
Vol 319 (1545) ◽  
pp. 139-156 ◽  
Keyword(s):  
Radioactive Waste ◽  
Field Experiments ◽  
The United States ◽  
Crystalline Rocks ◽  
Granitic Rocks ◽  
Rock Types ◽  
Basement Rocks ◽  
Deep Boreholes ◽  
High Level ◽  
Underground Research Laboratory

Crystalline rocks, particularly granitic rocks and basalts, are one of the principal rock types under consideration as a potential host rock for a high-level radioactive waste repository. Permeability in such rocks is related to discontinuities of various scales, and the quantification and prediction of groundwater flow within both the fractures and the intact rock between the fractures is the major goal of field experiments. The Canadian Underground Research Laboratory is unique in that the hydrogeological conditions within a large volume of rock surrounding the experimental shaft are being monitored before, during and after excavation and the results compared with model predictions. In Switzerland twelve deep boreholes are being drilled to over 1000 m to investigate crystalline basement rocks beneath a cover of sediments. The Stripa Mine in Sweden has hosted a major experimental programme including heater tests to stimulate the thermal effect of radioactive waste and hydrogeological tests at various scales down to individual fractures. The United States of America, the United Kingdom, France and Finland have also embarked on major experimental programmes. Continuing research is needed, with an emphasis on field experiments and research in underground rooms, to provide the data on which detailed risk assessments can be based.

Soda-granites from South of Tatanagar, Bihar, India

1966 ◽  
Vol 103 (4) ◽  
pp. 340-351 ◽  
Author(s):  
A. K. Banerji ◽  
A. K. Talapatra
Keyword(s):  
Partial Melting ◽  
Shear Zone ◽  
Confining Pressure ◽  
Residual Liquid ◽  
Copper Sulphide ◽  
Granite Magma ◽  
Singhbhum Shear Zone ◽  
Sudden Release ◽  
Singhbhum Granite

AbstractThe nature and origin of some soda-granites from the western part of the Singhbhum shear zone, Bihar, India, are discussed. These soda-granites are responsible for copper sulphide, apatite-magnetite, and uraniferous mineralization within the shear zone. Earlier workers regarded these rocks as sheared materials representing a portion of the high sodic residual liquid from the neighbouring Singhbhum granite magma. The present work indicates that these rocks are migmatitic in nature and are the products of progressive replacement of pre-existing pelitic and semi-pelitic schists by felspathic materials. Migmatization is essentially post-shearing in age while the Singhbhum granite is pre-shearing in age. The migmatitic materials appear to have been derived by the partial melting of the Singhbhum granite during shearing, particularly in depth, as a result of sudden release of confining pressure consequent upon shearing and generation of heat caused by friction at the base of the shear zone. The resulting liquids, which were albite rich, found easy passage through the shear zone and brought about migmatization and mineralization in its wake.

Distractor-Aware Tracking with Multi-Task and Dynamic Feature Learning

2020 ◽  
pp. 2150031
Author(s):  
Weichun Liu ◽  
Xiaoan Tang ◽  
Chenglin Zhao
Keyword(s):  
Correlation Filter ◽  
Coarse Grained ◽  
Dynamic Feature ◽  
Semantic Features ◽  
Low Level ◽  
Fine Grained ◽  
Semantic Embedding ◽  
Training Stage ◽  
Online Tracking ◽  
High Level

Recently, deep trackers based on the siamese networking are enjoying increasing popularity in the tracking community. Generally, those trackers learn a high-level semantic embedding space for feature representation but lose low-level fine-grained details. Meanwhile, the learned high-level semantic features are not updated during online tracking, which results in tracking drift in presence of target appearance variation and similar distractors. In this paper, we present a novel end-to-end trainable Convolutional Neural Network (CNN) based on the siamese network for distractor-aware tracking. It enhances target appearance representation in both the offline training stage and online tracking stage. In the offline training stage, this network learns both the low-level fine-grained details and high-level coarse-grained semantics simultaneously in a multi-task learning framework. The low-level features with better resolution are complementary to semantic features and able to distinguish the foreground target from background distractors. In the online stage, the learned low-level features are fed into a correlation filter layer and updated in an interpolated manner to encode target appearance variation adaptively. The learned high-level features are fed into a cross-correlation layer without online update. Therefore, the proposed tracker benefits from both the adaptability of the fine-grained correlation filter and the generalization capability of the semantic embedding. Extensive experiments are conducted on the public OTB100 and UAV123 benchmark datasets. Our tracker achieves state-of-the-art performance while running with a real-time frame-rate.

scholarly journals A low-to-high friction transition in gradient nano-grained Cu and Cu-Ag alloys

Friction ◽  
2020 ◽  
Author(s):  
Xiang Chen ◽  
Zhong Han
Keyword(s):  
Subsurface Layer ◽  
Coarse Grained ◽  
Structure Evolution ◽  
Wear Loss ◽  
Strongly Correlated ◽  
Low Friction ◽  
Coarse Grained Sample ◽  
Low Wear ◽  
High Level ◽  
Worn Surface

AbstractA unique low-to-high friction transition is observed during unlubricated sliding in metals with a gradient nano-grained (GNG) surface layer. After persisting in the low-friction state (0.2–0.4) for tens of thousands of cycles, the coefficients of friction in the GNG copper (Cu) and copper-silver (Cu-5Ag) alloy start to increase, eventually reaching a high level (0.6–0.8). By monitoring the worn surface morphology evolution, wear-induced damage accumulation, and worn subsurface structure evolution during sliding, we found that the low-to-high friction transition is strongly correlated with distinct microstructural instabilities induced by vertical plastic deformation and wear-off of the stable nanograins in the subsurface layer. A very low wear loss of the GNG samples was achieved compared with the coarse-grained sample, especially during the low friction stage. Our results suggest that it is possible to postpone the initiation of low-to-high friction transitions and enhance the wear resistance in GNG metals by increasing the GNG structural stability against grain coarsening under high loading.

Lead–zinc–barite veins of the Dorion Area, Thunder Bay District, Ontario

1977 ◽  
Vol 14 (9) ◽  
pp. 1963-1979 ◽  
Author(s):  
James M. Franklin ◽  
Roger H. Mitchell
Keyword(s):  
Lead Isotopes ◽  
Central Zone ◽  
Chloride Ion ◽  
Coarse Grained ◽  
Vein Wall ◽  
Sulphur Isotope ◽  
Thunder Bay ◽  
Basement Rocks ◽  
Lake Formation ◽  
Lead Zinc

The lead–zinc–barite deposits of the Dorion region are spatially associated with the unconformity between the Sibley Group (Helikian) and Archean and Aphebian basement rocks. The veins are coarse grained, and mineralogically zoned with galena–calcite in the central zone, sphalerite–quartz surrounding the central zone, and barite (±chalcopyrite) in the vein extremities. Veins occur near the pinch-out of the "Pass Lake formation" (basal Sibley Group), within the dolomite of the overlying "Rossport formation", or in nearby basement fractures. Rossport dolomite, where it forms a vein wall, is highly altered to metal-enriched chert and calcite. Archean wall rocks are not altered.Potassium–argon isotopic determinations on mica in Archean pegmatite immediately adjacent to a vein indicate that the transporting solutions were too cool to cause re-equilibration of the Ar within the mica. Sulphur-isotope data indicate equilibrium between galena and sphalerite yielding a depositional temperature range of 35–135 °C, and disequilibrium between sulphide–sulphate pairs. Lead isotopes are highly anomalous, yielding a secondary isochron which indicates either an Archean, or more probably a mixed Archean–Aphebian, source of lead.The deposits formed from metal leached from either basement rocks or breakdown of Sibley sandstone matrix. Metals and sulphate moved through the permeable sandstone, probably as chloride-ion complexes, and precipitated at the sandstone pinch-out. Reduced sulphur, possibly derived from organic decay, and probably held in a gas trap at the sandstone pinch out, caused precipitation of the sulphides by reaction with metal-bearing brines.

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