I.—Hapalocrinus Victoriæ, N.S., Silurian, Melbourne, and its Relation to the Platycrinidæ

1897 ◽  
Vol 4 (8) ◽  
pp. 337-345 ◽  
Author(s):  
F. A. Bather
Keyword(s):  
Iron Oxide ◽  
Geological Survey ◽  
Fine Grained ◽  
The Matrix

The specimen herein described was sent me by Mr. T. S. Hall, M.A., of Melbourne University. It was found by Mr. F. P. Spry in a rock of supposed Silurian age, at the Yarra Improvement Works, near Prince's Bridge, Melbourne, in November, 1896. The matrix is a fine-grained micaceous sandstone, of a dark purplegrey, weathering yellowish. It often contains crinoid columnals, such as were long ago noticed by the Geological Survey of Victoria, and were figured by W. Blandowski as “Cyatocrinites (probably)pinnatus”; but neither from here, nor from any other Silurian rock of Australia, has a crinoid crown hitherto been recoi-ded. The remains of the crinoid are in the form of an impression, coloured red by iron-oxide; all calcareous matter has been dissolved away. The counterpart of the impression has not been preserved. The specimen was studied by means of wax squeezes; the drawing (Plate XV) represents such a squeeze; and the description follows the drawing.

Microstructure of Friction Stir Processed Mg-Y-Zn Alloy

2007 ◽  
Vol 558-559 ◽  
pp. 777-780 ◽  
Author(s):  
Taiki Morishige ◽  
Masato Tsujikawa ◽  
Sung Wook Chung ◽  
Sachio Oki ◽  
Kenji Higashi
Keyword(s):  
Equal Channel Angular Extrusion ◽  
Second Phase ◽  
Ingot Metallurgy ◽  
Friction Stir ◽  
Fine Grained ◽  
Probe Diameter ◽  
Fine Grain ◽  
Second Phase Particles ◽  
The Matrix ◽  
Zn Alloy

Friction stir processing (FSP) is the effective method of the grain refinement for light metals. The aim of this study is to acquire the fine grained bulk Mg-Y-Zn alloy by ingot metallurgy route much lower in cost. Such bulk alloy can be formed by the superplastic forging. The microstructure of as-cast Mg-Y-Zn alloy was dendrite. The dendrite arm spacing was 72.5 [(m], and there are the lamellar structures in it. FSP was conducted on allover the plate of Mg-Y-Zn alloy for both surfaces by the rotational tool with FSW machine. The stirring passes were shifted half of the probe diameter every execution. The dendrite structures disappeared after FSP, but the lamellar structure could be observed by TEM. The matrix became recrystallized fine grain, and interdendritic second phase particles were dispersed in the grain boundaries. By using FSP, cast Mg-Y-Zn alloy could have fine-grained. This result compared to this material produced by equal channel angular extrusion (ECAE) or rapid-solidified powder metallurgy (RS P/M). As the result, as-FSPed material has the higher hardness than materials produced by the other processes at the similar grain size.

Age and Geochemical Studies of the Snyder Breccia, Coastal Labrador

1975 ◽  
Vol 12 (3) ◽  
pp. 361-370 ◽  
Author(s):  
Jackson M. Barton Jr. ◽  
Erika S. Barton
Keyword(s):  
Trace Element ◽  
North Atlantic ◽  
Layered Intrusion ◽  
Basement Complex ◽  
Fine Grained ◽  
The North ◽  
Isotopic Analyses ◽  
The Matrix ◽  
The North Atlantic ◽  
Geochemical Studies

The Snyder breccia is composed of angular to subrounded xenoliths of migmatites and amphibolites in a very fine grained matrix. It is apparently intrusive into the metasediments of the Snyder Group exposed at Snyder Bay, Labrador. The Snyder Group unconformably overlies a migmatitic and amphibolitic basement complex and is intruded by the Kiglapait layered intrusion. K–Ar ages indicate that the basement complex is Archean in age (> 2600 m.y. old) and that the Kiglapait layered intrusion was emplaced prior to 1280 m.y. ago. Major and trace element analyses of the matrix of the Snyder breccia indicate that while it was originally of tonalitic composition, later it locally underwent alteration characterized by loss of sodium and strontium and gain of potassium, rubidium and barium. Rb–Sr isotopic analyses show that this alteration occurred about 1842 m.y. ago, most probably contemporaneously with emplacement of the breccia. The Snyder Group thus was deposited sometime between 2600 and 1842 m.y. ago and may be correlative with other Aphebian successions preserved on the North Atlantic Archean craton.

Composition, technology and provenance of Roman pottery fromNapoca(Cluj-Napoca, Romania)

Clay Minerals ◽  
2018 ◽  
Vol 53 (4) ◽  
pp. 621-641 ◽  
Author(s):  
Ágnes Gál ◽  
Corina Ionescu ◽  
Mátyás Bajusz ◽  
Vlad A. Codrea ◽  
Volker Hoeck ◽  
...  
Keyword(s):  
Middle Miocene ◽  
Raw Materials ◽  
Ceramic Body ◽  
Polarized Light ◽  
Raw Material ◽  
Gradual Transition ◽  
X Ray ◽  
Fine Grained ◽  
The Matrix ◽  
Technological Constraints

ABSTRACTSecond-century CE (common era) household pottery sherds found in the city ofNapoca(present day Cluj-Napoca, Romania) in Roman Dacia were investigated by polarized light optical microscopy, X-ray powder diffraction, Fourier-transform infrared spectroscopy and cold field emission scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy to obtain information on technology, raw materials and site of production. Compositionally, all samples are similar with comparable fine and semi-fine microstructures and oriented microtextures. Optically, there is a gradual transition from microcrystalline to an amorphous illitic-muscovitic matrix. The small aplastic inclusions are mostly quartz and feldspar. Fine-grained carbonate aggregates are distributed inhomogeneously in the ceramic body. Well-preserved Middle Miocene foraminifera tests are characteristic of the ceramics. The gradual thermal changes of the matrix and the newly formed phases upon firing, such as ‘ceramic melilite’, Fe-gehlenite, clinopyroxene, glass, hematite and some maghemite support inferences regarding the technological constraints in producing the pottery. The firing took place in a mostly oxidizing atmosphere and the temperature extended from at least 850°C to >900°C. The Middle Miocene marly clay from the area surrounding the site shows similar mineralogical and micropalaeontological contents to those of the ceramic specimens and is the best candidate for the raw material used for local production of the Roman pottery.

The Microstructure and Superplastic Behavior of Clean Mechanically Alloyed Titanium–Titanium Boride Alloys

1999 ◽  
Vol 601 ◽  
Author(s):  
A.P. Brown ◽  
R Brydson ◽  
C. Hammond ◽  
A. Wisbey ◽  
T.M.T. Godfrey
Keyword(s):  
Sheet Material ◽  
Hot Isostatic Pressing ◽  
Superplastic Forming ◽  
Titanium Boride ◽  
Production Cycle ◽  
Microstructural Development ◽  
Mechanically Alloyed ◽  
Boron Powder ◽  
Fine Grained ◽  
The Matrix

AbstractThe superplastic forming (SPF) of titanium alloys is an established technology. A reduction in grain size from that of the typical sheet materials would lead to enhanced SPF properties and hence a reduction in production cycle times. This study describes the microstructural development and superplastic behaviour of fine-grained Ti-6%Al-4%V alloys. Ball-milling Ti-6%Al-4%V powder produces a nanocrystalline material; however on consolidation by hot isostatic pressing rapid grain growth occurs. Addition of boron powder during milling leads to boride precipitates in the matrix of the consolidated alloy. The precipitates are dispersed inhomogeneously, resulting in localized grain refinement. Superplastic testing revealed cavitation formation but in comparison to conventional sheet material, large elongations were achieved at relatively high strain rates.

The Effect of Iron Oxide on the Mechanical and Ageing Properties of Y-TZP Ceramic

2016 ◽  
Vol 701 ◽  
pp. 225-229 ◽  
Author(s):  
Sivanesan Sivakumar ◽  
Hsien Loong Teow ◽  
Ramesh Singh ◽  
Ali Niakan ◽  
Nobuyuki Mase
Keyword(s):  
Fracture Toughness ◽  
Iron Oxide ◽  
Bulk Density ◽  
Phase Stability ◽  
Vickers Hardness ◽  
Tetragonal Phase ◽  
Superheated Steam ◽  
Matrix Stiffness ◽  
Sintering Aid ◽  
The Matrix

A small amount of iron oxide (Fe2O3) was added to the commercially available 3 mol% Y-TZP as a sintering aid over a temperature range of 1250°C to 1500°C. Sintered samples were then evaluated to determine the bulk density, Vickers hardness, and fracture toughness. In addition, hydrothermal ageing experiments to determine the tetragonal phase stability were performed on selected sintered samples in superheated steam at 180°C / 10 bar for up to 24 hours. Based on the work carried out, it was revealed that additions of Fe2O3 particularly 0.3 wt% was indeed beneficial in aiding densification, improving the matrix stiffness and hardness when compared to undoped Y-TZP sintered at temperatures below 1350°C. Addition of Fe2O3 was found to have negligible effects on the fracture toughness of all samples with the exception of the 0.5 and 1 wt% doped Y-YZP sintered above 1400°C. Hydrothermal ageing resistance of Y-TZP was found to be enhanced with the addition of Fe2O3 in the Y-TZP matrix.

Mineral assemblages and xenolith cargo in the Storkwitz carbonatite (Delitzsch Complex, Germany)

2020 ◽  
Author(s):  
Hripsime Gevorgyan ◽  
Sascha Schmidt ◽  
Ilja Kogan ◽  
Manuel Lapp
Keyword(s):  
Late Cretaceous ◽  
Early Stage ◽  
Soft Rock ◽  
Core Material ◽  
Compositional Variation ◽  
Published Data ◽  
Fine Grained ◽  
Ultramafic Lamprophyre ◽  
The Matrix ◽  
History Of

<p>The multi-compositional carbonatite body of Storkwitz is one of several purported diatremes of the Late Cretaceous Delitzsch Complex, which comprises carbonatites and ultramafic lamprophyres emplaced into a heterogeneous series of volcanic and sedimentary rocks of Precambrian to Early Permian age (Krüger et al., 2013; Seifert et al., 2000). The Late Cretaceous peneplain is covered with about one hundred meters of Tertiary soft rock. According to Röllig et al. (1990), the Delitzsch Complex developed in six stages: (i) hidden intrusion of a dolomite carbonatite (rauhaugite) that led to the formation of a fenite aureole; (ii) ultramafic and alkaline lamprophyre intrusion (alnöite, aillikite, monchiquite); (iii) formation of beforsitic diatremes (intrusive breccias), including xenoliths of dolomite carbonatite and ultramafic lamprophyre; (iv) ultramafic and alkali lamprophyres (dykes within diatremes of 3<sup>rd</sup> stage); (v) formation of beforsite and (vi) alvikite dykes.</p><p>The Storkwitz carbonatite is mainly characterized by beforsitic breccias containing abundant angular xenoliths of metasediments form the complete underlying stratigraphic succession, metamorphic and igneous rocks, as well as rounded xenoliths of ultramafic lamprophyre, rauhaugite, fenite, and glimmerite, which suggest the existence of a deep-seated carbonatite pluton (Seifert et al., 2000). It is remarkable that the fenites exhibit a different degree of fenitization and show occurrence of phlogopite in the strongly fenitized samples. The matrix of the Storkwitz carbonatite is mainly composed of ankerite and calcite/siderite, which corresponds to ferro- or silico-carbonatites.</p><p>Detailed petrographical observations on extensive drill core material, new analyses and a reinterpretation of published data confirm the existence of compositional variation and zonation within the carbonatite body that reflect independent crystallization history and formation due to multiple magmatic events. The different generations of apatite and phlogopite from the early stage of the plutonic dolomite carbonatite through the late-stage beforsite dykes and fine-grained calcite carbonatite veins shed light on the crystallization history and magma development of carbonatites.</p><p> </p><p>References</p><p> </p><p>Krüger, J.C., Romer, R.L., Kämpf, H., 2013. Late Cretaceous ultramafic lamprophyres and carbonatites from the Delitzsch Complex, Germany. Chemical Geology, 353, 140-150.</p><p>Röllig, G., Viehweg, M., Reuter, N., 1990. The ultramafic lamprophyres and carbonatites of Delitzsch/GDR. Zeitschrift für Angewandte Geologie, 36, 49-54.</p><p>Seifert, W., Kämpf, H., Wasternack, J., 2000. Compositional variation in apatite, phlogopite and other accessory minerals of the ultramafic Delitzsch complex, Germany: implication for cooling history of carbonatites. Lithos, 53, 81-100.</p>

On the nature of withamite from Glen Coe, Scotland (With Plate IV.)

1938 ◽  
Vol 25 (162) ◽  
pp. 119-124 ◽  
Author(s):  
C. Osborne Hutton
Keyword(s):  
Satisfactory Agreement ◽  
Geological Survey ◽  
Fine Grained ◽  
Andesitic Rock

In 1824 Henry Witham discovered a beautiful red epidote mineral in the lavas of Glen Coe, Argllshire, which was described by Brewster under the name withamite. An analysis was made by Coverdale of obviously highly impure material, but later a more complete one was carried out by Heddle on carefully hand-picked mineral. Heddle admits, however, that his analysis shows ‘by no means a satisfactory agreement with the composition of epidote’, and from his figures it would seem very likely that his analysed material was also impure. In the Glen Coe Geological Survey Memoir no further data were recorded of this mineral, Heddle's analysis and description merely being quoted.The writer visited Glen Coe and collected material in a cutting on the new road, approximately 5½ miles west of King's House (Geological Survey, sheet 53), where it is fairly well exposed. It occurs in a fine-grained, rather altered andesitic rock, as narrow veinlets up to 120 mm. in length and 50 mm. in width ; also as infillings of vesicles. The veinlets may be straight or highly irregular; in the former case they possibly follow joint-planes, for the rock will often fracture along such a plane, producing one or two surfaces covered with the red epidote mineral. The vesicles vary greatly in size from approximately 0·3 to 70 mm., and in the larger ones calcite is a common associate.

Mineralogy of the near-surface expression of Au-As-Cu mineralization in an arid environment

1994 ◽  
Vol 58 (391) ◽  
pp. 315-323
Author(s):  
R. Bogoch ◽  
M. Shirav ◽  
A. Gilat ◽  
L. Halicz
Keyword(s):  
Iron Oxide ◽  
Surface Expression ◽  
Arid Environment ◽  
Solid Solution Phase ◽  
Near Surface ◽  
Amorphous Phases ◽  
Fine Grained ◽  
Precambrian Terrain ◽  
Spherical Droplets ◽  
Neutral Conditions

AbstractIn the arid, Late Precambrian terrain of southern Israel, a complex suite of minerals and amorphous species were deposited in host gneiss from fluids under near-neutral conditions within 1 m of the surface. The morphology of secondary gold appears to relate to its host mineral (skeletal-dendritic with quartz; multi-faceted crystals with arsenates; spherical droplets with iron oxide). The gold is very fine-grained, and was most likely complexed as a thiosulphate.Three amorphous phases are present (iron oxide, chrysocolla, Cu-Mn-(Fe-As) silicate). At least in part, gold and baryte appear to have crystallized out of a metal-Fe-oxide gel. Other minerals, including apatite, anglesite, and conichalcite, may have grown from appropriate crystallites present in the gel.The conichalcite occurs mainly as bladed to acicular radial spherulites. In the presence of lead, a solid solution phase between duftite and conichalcite (‘Pb-conichalcite’) was formed.

Jadeite–K-feldspar rocks and jadeitites from northwest Turkey

1997 ◽  
Vol 61 (409) ◽  
pp. 835-843 ◽  
Author(s):  
Aral I. Okay
Keyword(s):  
Grain Size ◽  
Debris Flows ◽  
Bulk Rock ◽  
Rock Composition ◽  
Bulk Rock Composition ◽  
Fine Grained ◽  
Fine Grain ◽  
The Matrix ◽  
Mineral Pair

AbstractBlueschist-facies rocks with jadeite-K-feldspar-lawsonite paragenesis occur as exotic blocks in Miocene debris flows in the blueschist belt of northwest Turkey. The jadeite-K-feldspar rocks have a very fine grain size and although recrystallized locally retain a relict porphyritic volcanic texture. The former nepheline microphenocrysts, recognized from their characteristic shapes, are pseudomorphed by jadeite and K-feldspar, while the relict magmatic aegirine has rims of jadeite. The matrix of the rock consists of very fine-grained aggregates of jadeite, K-feldspar and lawsonite. In some blocks, jadeite makes up >60% of the mode. Jadeite, K-feldspar and lawsonite in the blocks are essentially pure end-member in composition. P-T estimates for these rocks are 8 ± 2 kbar and 300 ± 50°C. The preserved volcanic texture, relict aegirine and the bulk rock composition indicate that these rocks represent metamorphosed phonolites. The paragenesis in these rocks shows that jadeite-K-feldspar is a stable mineral pair in blueschist-facies P-T conditions.

Sign in / Sign up

Export Citation Format

Share Document