Basalt Textures from the Southeastern Lower Galilee, Israel

1964 ◽  
Vol 101 (6) ◽  
pp. 548-557
Author(s):  
M. J. Oppenhein
Keyword(s):  
Grain Size ◽  
Flow Characteristics ◽  
Cooling Conditions ◽  
End Members

AbstractBasalt groundmass textural nomenclature is reviewed and revised. The intergranular and ophitic extures are seen as end members of a series with steadily increasing grain-size, the international representative of which is here termed the “isogranular” texture. Undere intrusive conditions the series may be extended to include the poikilitic texture. Ophitic texture is regarded as an intergrowth;the term “sub-ophitic”s not suitable for basalts but may be retained for texturally isotropic rocks. When basalts cool hurriedly they will tend to develop an intergranular texture whereas extension of the crystallization period permits the formation of an ophitic texture. Cooling conditions will be determined by a combination of the effects of the volatile concentration and the flow characteristics, the latter partly depending on topography.

scholarly journals Flow Characteristics and Grain Size Distribution of Granular Gangue Mineral by Compaction Treatment

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Ran Yuan ◽  
Dan Ma ◽  
Hongwei Zhang
Keyword(s):  
Weight Loss ◽  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Water Flow ◽  
Fine Particles ◽  
Flow Characteristics ◽  
Test System ◽  
Chemical Components ◽  
Gangue Mineral

A test system for water flow in granular gangue mineral was designed to study the flow characteristics by compaction treatment. With the increase of the compaction displacement, the porosity decreases and void in granular gangue becomes less. The main reason causing initial porosity decrease is that the void of larger size is filled with small particles. Permeability tends to decrease and non-Darcy flow factor increases under the compaction treatment. The change trend of flow characteristics shows twists and turns, which indicate that flow characteristics of granular gangue mineral are related to compaction level, grain size distribution, crushing, and fracture structure. During compaction, larger particles are crushed, which in turn causes the weight of smaller particles to increase, and water flow induces fine particles to migrate (weight loss); meanwhile, a sample with more weight of size (0–2.5 mm) has a higher amount of weight loss. Water seepage will cause the decrease of some chemical components, where SiO2 decreased the highest in these components; the components decreased are more likely locked at fragments rather than the defect of the minerals. The variation of the chemical components has an opposite trend when compared with permeability.

scholarly journals Sediment transport processes across the Tibetan Plateau inferred from robust grain-size end members in lake sediments

2014 ◽  
Vol 10 (1) ◽  
pp. 91-106 ◽  
Author(s):  
E. Dietze ◽  
F. Maussion ◽  
M. Ahlborn ◽  
B. Diekmann ◽  
K. Hartmann ◽  
...  
Keyword(s):  
Grain Size ◽  
Sediment Transport ◽  
Tibetan Plateau ◽  
Transport Processes ◽  
The Tibetan Plateau ◽  
Dust Deposition ◽  
Northerly Wind ◽  
Near Surface ◽  
Depositional Processes ◽  
End Members

Abstract. Grain-size distributions offer powerful proxies of past environmental conditions that are related to sediment sorting processes. However, they are often of multimodal character because sediments can get mixed during deposition. To facilitate the use of grain size as palaeoenvironmental proxy, this study aims to distinguish the main detrital processes that contribute to lacustrine sedimentation across the Tibetan Plateau using grain-size end-member modelling analysis. Between three and five robust grain-size end-member subpopulations were distinguished at different sites from similarly–likely end-member model runs. Their main modes were grouped and linked to common sediment transport and depositional processes that can be associated with contemporary Tibetan climate (precipitation patterns and lake ice phenology, gridded wind and shear stress data from the High Asia Reanalysis) and local catchment configurations. The coarse sands and clays with grain-size modes >250 μm and <2 μm were probably transported by fluvial processes. Aeolian sands (~200 μm) and coarse local dust (~60 μm), transported by saltation and in near-surface suspension clouds, are probably related to occasional westerly storms in winter and spring. Coarse regional dust with modes ~25 μm may derive from near-by sources that keep in longer term suspension. The continuous background dust is differentiated into two robust end members (modes: 5–10 and 2–5 μm) that may represent different sources, wind directions and/or sediment trapping dynamics from long-range, upper-level westerly and episodic northerly wind transport. According to this study grain-size end members of only fluvial origin contribute small amounts to mean Tibetan lake sedimentation (19± 5%), whereas local to regional aeolian transport and background dust deposition dominate the clastic sedimentation in Tibetan lakes (contributions: 42 ± 14% and 51 ± 11%). However, fluvial and alluvial reworking of aeolian material from nearby slopes during summer seems to limit end-member interpretation and should be crosschecked with other proxy information. If not considered as a stand-alone proxy, a high transferability to other regions and sediment archives allows helpful reconstructions of past sedimentation history.

Effect of post-heat treatment cooling on microstructure and mechanical properties of selective laser melting manufactured austenitic 316L stainless steel

2020 ◽  
Vol 26 (10) ◽  
pp. 1739-1749
Author(s):  
Saad Waqar ◽  
Jiangwei Liu ◽  
Qidong Sun ◽  
Kai Guo ◽  
Jie Sun
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Grain Size ◽  
316L Stainless Steel ◽  
Laser Melting ◽  
Content Type ◽  
Post Annealing ◽  
Cooling Conditions ◽  
Microstructure And Mechanical Properties ◽  
Heat Treated

Purpose This paper aims to investigate the influence of different post-annealing cooling conditions, i.e. furnace cooling (heat treatment (HT) 1 – slow cooling) and air cooling (HT 2 – fast cooling), on the microstructure and mechanical properties of selective laser melting (SLM) built austenitic 316L stainless steel (SS). Design/methodology/approach Three sets of 316L SS samples were fabricated using a machine standard scanning strategy. Each set consists of three tensile samples and a cubic sample for microstructural investigations. Two sets were subsequently subjected to annealing HT with different cooling conditions, i.e. HT 1 and HT 2, whereas one set was used in the as-built (AB) condition. The standard metallographic techniques of X-ray diffraction, scanning electron microscopy and electron back-scattered diffraction were used to investigate the microstructural variations induced by different cooling conditions. The resultant changes in mechanical properties were also investigated. Findings The phase change of SLM fabricated 316L was observed to be independent of the investigated cooling conditions and all samples consist of austenite phase only. Both HT 1 and HT 2 lead to dissolved characteristic melt pools of SLM. Noticeable increase in grain size of HT 1 and HT 2 samples was also observed. Compared with AB samples, the grain size of HT 1 and HT 2 was increased by 12.5% and 50%, respectively. A decreased hardness and strength, along with an increased ductility was also observed for HT 2 samples compared with HT 1 and AB samples. Originality/value From previous studies, it has been noticed that most investigations on HT of SLM fabricated 316L were mainly focused on the HT temperature or holding time. However, the post-HT cooling rate is also an equally important factor in deciding the microstructure and mechanical properties of heat-treated components. Therefore, this paper investigates the influence of different post-annealing cooling conditions on microstructure and mechanical properties of SLM fabricated 316L components. This study provides a foundation for considering the post-HT cooling rate as an influential parameter that controls the properties of heat-treated SLM components.

scholarly journals Heavy Mineral Variability in the Yellow River Sediments as Determined by the Multiple-Window Strategy

Minerals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 85 ◽  
Author(s):  
Bingfu Jin ◽  
Mengyao Wang ◽  
Wei Yue ◽  
Lina Zhang ◽  
Yanjun Wang
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Yellow River ◽  
River Sediments ◽  
Size Fraction ◽  
Heavy Mineral ◽  
The Yellow River ◽  
Yellow River Sediment ◽  
Yellow River Sediments ◽  
End Members

In this study, heavy mineral analysis was carried out in different size fractions of the Yellow River sediment to extract its end-members. It shows that heavy mineral contents, species, and compositions vary in different grain sizes. Distribution curve of heavy mineral concentration (HMC) and particle size frequency curve are in normal distribution. In most samples, the size fraction of 4.5–5.0 Φ contains the maximum HMC (18% on average). Heavy mineral assemblages of the Yellow River are featured by amphibole + epidote + limonite + garnet. Amphibole content is high in coarse fraction of >3.0 Φ and reaches its peak value in 3.5–4.5 Φ. Epidote is rich in a size fraction of >3.5 Φ, and increase as the particle size becomes fine. Micas content is high in coarse subsamples of <3.0 Φ, but almost absent in fine grains of >4.0 Φ. Metallic minerals (magnetite, ilmenite, hematite, and limonite) increase as the sediment particle size become fine, and reach the peak in silt (>4.0 Φ). Other minerals such as zircon, rutile, tourmaline, garnet, and apatite account for about 15%, and mainly concentrate in fine sediment. Further analysis reveals that similarity value between the most abundant grain size group and wide window grain size group is high (0.978 on average). The grain size of 4.0–5.0 Φ ± 0.5 Φ is suitable to carry out detrital mineral analysis in the Yellow River sediments. Our study helps to eliminate cognitive bias due to narrow grain size strategy, and to provide heavy mineral end-members of the Yellow River sediment for provenance discrimination in the marginal seas of East China.

scholarly journals Eolian dust dispersal patterns since the last glacial period in eastern Central Asia: insights from a loess-paleosol sequence in the Ili Basin

2018 ◽  
Vol 14 (3) ◽  
pp. 271-286 ◽  
Author(s):  
Yue Li ◽  
Yougui Song ◽  
Kathryn E. Fitzsimmons ◽  
Hong Chang ◽  
Rustam Orozbaev ◽  
...  
Keyword(s):  
Grain Size ◽  
Magnetic Susceptibility ◽  
Central Asia ◽  
Chinese Loess Plateau ◽  
Magnetic Characteristics ◽  
Magnetic Minerals ◽  
Near Surface ◽  
Siberian High ◽  
End Members ◽  
Eastern Central Asia

Abstract. The extensive loess deposits of the Eurasian mid-latitudes provide important terrestrial archives of Quaternary climatic change. As yet, however, loess records in Central Asia are poorly understood. Here we investigate the grain size and magnetic characteristics of loess from the Nilka (NLK) section in the Ili Basin of eastern Central Asia. Weak pedogenesis suggested by frequency-dependent magnetic susceptibility (χfd%) and magnetic susceptibility (MS) peaks in primary loess suggest that MS is more strongly influenced by allogenetic magnetic minerals than pedogenesis, and may therefore be used to indicate wind strength. This is supported by the close correlation between variations in MS and proportions of the sand-sized fraction. To further explore the temporal variability in dust transport patterns, we identified three grain size end-members (EM1, mode size 47.5 µm; EM2, 33.6 µm; EM3, 18.9 µm) which represent distinct aerodynamic environments. EM1 and EM2 are inferred to represent grain size fractions transported from proximal sources in short-term, near-surface suspension during dust outbreaks. EM3 appears to represent a continuous background dust fraction under non-dust storm conditions. Of the three end-members, EM1 is most likely the most sensitive recorder of wind strength. We compare our EM1 proportions with mean grain size from the Jingyuan section in the Chinese loess plateau, and assess these in the context of modern and Holocene climate data. Our research suggests that the Siberian High pressure system is the dominant influence on wind dynamics, resulting in loess deposition in the eastern Ili Basin. Six millennial-scale cooling (Heinrich) events can be identified in the NLK loess records. Our grain size data support the hypothesis that the Siberian High acts as teleconnection between the climatic systems of the North Atlantic and East Asia in the high northern latitudes, but not for the mid-latitude westerlies.

A 25-kyr record of East African monsoon variability: Insights from grain-size distributions and end-member modeling of siliciclastic sediments from Lake Chala

2020 ◽  
Author(s):  
Inka Meyer ◽  
Maarten Van Daele ◽  
Niels Thange ◽  
Dirk Verschuren ◽  
Marc De Batist
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
East Africa ◽  
Grain Size Distribution ◽  
Transport Processes ◽  
Monsoon Circulation ◽  
East African ◽  
African Monsoon ◽  
Sediment Fraction ◽  
End Members

&lt;p&gt;Terrigenous particles deposited in all kinds of sedimentary records (terrestrial, marine and lacustrine) have proven to yield valuable information for reconstruction of paleo-climate and paleo-environments. Natural sediments typically represent a mixture of deposits of diverse provenance, potentially supplied by different transport processes, expressed in a bi-or poly-modal grain-size distribution. Recently, complex mathematical-statistical end-member models have been developed to disentangle the different sub-populations within one grain-size distribution, which are then assumed to represent a distinct sediment fraction that has a single provenance and/or was transported by the same process to the site of deposition.&lt;/p&gt;&lt;p&gt;Here we present end-member modeling results of the terrigenous sediment fraction in a 25-kyr sediment sequence from Lake Chala (Kenya/Tanzania), revealing valuable information on climate and environmental change in equatorial East Africa since the Last Glacial Maximum (LGM). Calculated end members could be related to distinct source areas and transport processes, namely to fine aeolian dust, fine-grained soil runoff, coarser aeolian dust from proximal sources and coarse erosive material originating from the crater rim surrounding the lake. Variations in the occurrence of distal versus proximal dust is suggested to be a reliable indicator for changes in East African monsoon circulation. During Northern Hemisphere cold periods, such as the LGM and Younger Dryas (YD), wind systems associated with the Intertropical Convergence Zone (ITCZ) were pushed southward, causing a more intense influence of the NE monsoon at Lake Chala. This resulted in high amounts of fine dust originating from the Horn of Africa region. At the same time, SE monsoon circulation was diminished due to a reduced atmospheric pressure gradient between the Asian/Indian continent and the Indian Ocean. Influx of coarse dust from proximal sources, which are mostly located east of Lake Chala, was impossible due to the weaker SE monsoon circulation. After termination of the YD, rapid reestablishment of the SE monsoon in the Early Holocene is recorded by an abrupt increase in the influx of coarse dust.&lt;/p&gt;&lt;p&gt;Lake Chala sediments contain one of the few continuous and high-resolution climate records in East Africa spanning the past 25 kyr, providing detailed information on long-term climate variation in an area highly sensitive to hydrological variations. Subdividing the clastic sediment fraction into statistically robust end members produces multiple quantitative and independent proxies to help reconstruct this region&amp;#8217;s climate and environmental history.&lt;/p&gt;

Prediction of As-Cast Grain Size of Inoculated Multicomponent Aluminum Alloys

2014 ◽  
Vol 790-791 ◽  
pp. 185-190 ◽  
Author(s):  
Qiang Du ◽  
Yan Jun Li
Keyword(s):  
Numerical Simulation ◽  
Grain Size ◽  
Aluminum Alloys ◽  
Cooling Curve ◽  
Restriction Factor ◽  
Grain Sizes ◽  
Cooling Conditions ◽  
Proposed Model ◽  
Simulation Results ◽  
Melt Composition

In this paper, an extendedMaxwell-Hellawell numerical grain size prediction model is employed to predictas-cast grain size of inoculated aluminum alloys. Given melt composition,inoculation and cooling conditions, the model is able to predict maximumnucleation undercooling, cooling curve and final as-cast grain size of multi-componentalloys. The proposed model has been applied to various binary andmulticomponent alloys. Upon analyzing the numerical simulation results, it isfound that for both binary and multi-component alloys, grain size does not havea one-to-one relation with Growth Restriction Factor, Q, but has a clear ubiquitous correlation with the average diffusivity-weightedQ, defined as W in this paper. This founding helps solve the controversy seen inthe recent work on analytical grain size and Q relations. It also has been used to interpret the scatters seenin the measured grain sizes as a function of Q values reported in the literature.

Effects of Cooling Condition on Hot Tearing during Investment Casting

2011 ◽  
Vol 264-265 ◽  
pp. 355-360 ◽  
Author(s):  
Saeid Norouzi ◽  
Hassan Farhangi
Keyword(s):  
Grain Size ◽  
Fracture Surface ◽  
Surface Morphology ◽  
Thermal Gradient ◽  
Solidification Process ◽  
Surface Characteristics ◽  
Hot Tearing ◽  
Cooling Condition ◽  
Fracture Surface Morphology ◽  
Cooling Conditions

In the present study, the effect of cooling condition on hot tearing tendency and hot tearing fracture surface morphology were investigated. Results show that, the hot tear fracture surface characteristics are nearly similar under different cooling conditions. The hot tear surface exhibits two main features; the brittle region and the ductile region. The results also indicate that cooling condition has multifaceted effects on hot tearing phenomenon. Increasing cooling rate increases the thermal gradient, which raises the hot tearing tendency; concomitantly it decreases the grain size and dendrite arm spacing which increases the strength of the material. The occurrence of hot tearing phenomenon under different cooling conditions is discussed and evaluated based on the competition between these opposing factors during the solidification process.

Novel Grain Refiner for Hypo- and Hyper-Eutectic Al-Si Alloys

2011 ◽  
Vol 690 ◽  
pp. 49-52 ◽  
Author(s):  
Magdalena Nowak ◽  
Nadendla Hari Babu
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Al Alloys ◽  
Grain Structure ◽  
Grain Refiner ◽  
Silicon Alloys ◽  
Fine Grain ◽  
Cooling Conditions ◽  
Wide Range ◽  
Master Alloys

A novel effective grain refiner for hypo and hyper-eutectic Aluminium-Silicon alloys has been developed. The composition of the grain refiner has been optimized to produce a fine grain structure and finer eutectic. Effectiveness of grain size under various cooling conditions has also been investigated to simulate various practical casting conditions. For comparative purposes, a wide range of Al alloys have been produced with the addition of commercially available Al-5Ti-B master alloys. The results show that the addition of novel grain refiner reduces the grain size significantly. As a result of fine grains, the porosity in the solidified alloys is remarkably lower. A notable improvement in mechanical properties has also been observed.

scholarly journals Environmental dynamics since the last glacial in arid Central Asia: evidence from grain size distribution and magnetic properties of loess from the Ili Valley, western China

2017 ◽  
Author(s):  
Yue Li ◽  
Yougui Song ◽  
Kathryn E. Fitzsimmons ◽  
Hong Chang ◽  
Rustam Orozbaev ◽  
...  
Keyword(s):  
Grain Size ◽  
Central Asia ◽  
Polar Front ◽  
Western China ◽  
Weather Data ◽  
Near Surface ◽  
Dust Transport ◽  
Loess Deposition ◽  
Loess Deposits ◽  
End Members

Abstract. The extensive loess deposits of the Eurasian mid-latitudes provide important terrestrial records of Quaternary climatic change. As yet, however, loess records in Central Asia are poorly understood. Here we investigate the grain size and magnetic characteristics of loess from the Nilka (NLK) section in the Ili Basin of eastern Central Asia. Magnetic parameters indicate very weak pedogenesis compared with loess from other regions in Eurasia. The higher χlf values occur in primary loess, rather than in weak paleosols, and the variations in magnetic susceptibility (MS) value correlate closely with the proportions of the sand fraction. We attribute this result to high wind strength at the time of loess deposition. To explore the dust transport patterns further, we identified three grain size end members (EM1, mode size 47.5 µm; EM2, 33.6 µm; EM3, 18.9 µm) which represent distinct aerodynamic environments. EM1 and EM2 represent the grain-size fractions transported from proximal sources in short-term, near-surface suspension during dust outbreaks. EM3 appears to represent the continuous background dust fraction under non-dust storm processes. Of the three end members, EM1 is most likely the most sensitive recorder of wind strength. A lack of correlation between EM1 proportions and GISP δ18O values at the millennial scale, combined with modern weather data, suggests that Arctic polar front predominates in the Ili Basin and the Kyrgyz Tian Shan piedmont during cold phases, which leads to the dust transport and accumulation of loess deposits, while the shift of mid-latitude westerlies towards the south and north controls the patterns of precipitation/moisture variations in this region. Comparison of EM1 proportions with Northern Hemisphere summer insolation clearly illustrate local insolation-based control on wind dynamics in the region, and humdity can also influence grain size of loess over MIS3 in particular. Although, the polar front dominated wind dynamics for loess deposition in the region, the Central Asian high mountains obstructed its migration further south. Our results may also support the significance of the mid-latitude westerlies in transmitting North Atlantic climate signals to East Asia.

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