Silicic Bodies Research Articles

Occurrence of central peak craters on the Uranian satellites: Implications for surface structure and comparison with the Jovian and Saturnian systems

Craters with central peaks occur on the Uranian satellites Ariel, Umbriel, Titania, and Oberon; but do not occur on Miranda. The inelastic surface of Miranda is apparently due to the heavy tectonic reworking of its surface. A theory of expansion/contraction is proposed to explain the tectonic history of Miranda. The existence of central peak craters on the four largest satellites of Uranus implies that they have surface strengths similar to those of the Saturnian satellites and silicate bodies of the inner solar system which all have central peak craters. The absence of central peak craters on Miranda implies that it has an inelastic surface similar to those of the Jovian ice satellites Ganymede and Callisto whose surfaces do not contain central peak craters.

Permanent Crystal Lattice Contraction, a Primary Mechanism in Thermally Induced Alteration of Na Bentonite

AbstractThe basic process in thermal transformation of smectite to hydrous mica is generally thought to be a lattice charge change caused by partial replacement of tetrahedral silica by aluminum. This is assumed to yield preferential uptake of potassium with concomitant contraction and loss of expandability of smectite aggregates as well as release of silica that migrates by diffusion from interlayer space into interaggregate voids, where it may form amorphous silica hydrogels and possibly quartz.The latter process was investigated by use of hydrothermal tests of fully water saturated, as well as partly saturated Na-montmorillonite gels, the intention being to identify possible heat-induced changes in expandability on a molecular scale by applying electron microscopy. The gels were exposed to a temperature of 225°C for 18 days in a first test series and the microstructural patterns compared with those of non-heated material.A clear tendency of lattice contraction was observed in the heated clay gels, particularly in the non-saturated one. The microstructure had the form of networks of virtually non-expandable, interwoven dense stacks.A possible physical explanation of the contraction is that the heat caused instability of the interlayer water lattices, yielding dominant interatomic mass forces which caused contraction of the stacks. In connection herewith, silica was released from the smectite lattices and precipitated at the edges of the stacks, which reduced or eliminated the expandability. Minute, precipitated silicic bodies, amorphous as well as crystal-line, appeared in both clays.

Asteroid Families: Observational Evidence for Common Origins

Colors of minor planets in the UBV system indicate compositions quite distinct from those of the field population in each of three Hirayama families. The Eos and Koronis families apparently originated from the collisional fragmentation of undifferentiated silicate bodies, and the Nysa group from a geochemically differentiated parent body.

Fenitization of Mississagi Quartzite, Sudbury Area, Ontario

Two irregular bodies of fenitic breccia are described from the Kusk and Nemag Lakes area, 19 km southwest of Sudbury, Ontario. In each case, the host rock — feldspathic quartzite of the Mississagi Formation (Huronian Supergroup) — is brecciated and extensively replaced by aegirine, riebeckite, and alkali feldspar. Crosscutting relationships have led to a subdivision into mappable stages. The fenitic assemblages are relatively simple, but they are unusually sodic and deficient in calcium, potassium, and carbonate. Only in the most thoroughly fenitized rocks at Kusk Lake is microcline found. Desilication is a major process in the progressive conversion of the sandstone to a rock in equilibrium with the fluid phase. The scarcity of carbonate suggests that the igneous source material was essexitic or ijolitic rather than carbonatitic. The ultrasodic assemblages are interpreted as having formed near the heat source but clearly at subsolidus temperatures. Late introduction of potassium is attributed to changes in the geometry of the thermal gradient as the intrusive body cooled. Fenitization should not be so restrictive a term as to exclude cases where the resultant bulk compositions are ultrasodic or where the source is an alkaline silicate body rather than a carbonatite.

Accretionary Processes in the Early Solar System: An Experimental Approach

Micrometer-size silicate flakes do not accrete during impacts in the velocity range 1.5 to 9.5 kilometers per second. Conventional accretionary theories for silicate bodies are applicable only to particles whose orbits are similar. Metal-silicate fractionation in the solar system may have been affected by differences in the accretionary behavior of the metal and silicate particles.

Anisotropic expansion of siliceous refractories

During a study of the bloating of siliceous bodies we detected anisotropic expansion of the refractories and established its cause. Controlled regulation of the bloating of refractories is found to be possible.

Refractory properties of siliceous bodies for ramming the linings of acid arc steel furnaces

Refractory properties of siliceous bodies for ramming the linings of acid arc steel furnaces

Study of siliceous bodies for monolithic linings and using them in steel ladles

Study of siliceous bodies for monolithic linings and using them in steel ladles

Siliceous bodies for rammed linings of electric arc steel furnaces

Siliceous bodies for rammed linings of electric arc steel furnaces

Use of siliceous body for ramming linings in small steel ladles

Use of siliceous body for ramming linings in small steel ladles

Growth of the Earth's Core

To his recent communication1, proposing that the cause of convection in the mantle is chemical, Dr. Stacey added a note in proof attacking the idea used by me2,3 of a gradual growth of the Earth's core to give a tentative explanation of continental drift. He makes the objection that the settling of the Earth's core from an undifferentiated Earth, formed by the accretion of iron and silicate bodies like the meteorites, would release an amount of energy greater by an order of magnitude thanthat which would have been conducted through the Earth's surface since 3,000 million years ago, when I suggest separation began, supposing the geothermal gradient had always its present value. I do not think Stacey's objection is valid. I have a detailed paper in preparation giving an account of the thermal history of the Earth, assuming that convection in the mantle is possible: naturally this differs radically from the thermal history of the Earth previously presented by those4 who have only assumed conduction in the mantle.

Plant Opal in Soil

IN many soils there are small siliceous bodies showing optical isotropy, low refractive index and low density, which identify them with the mineral opal, SiO2.nH2O1. Some are diatoms or diatom fragments. Others are simple or ornamented rods, tubes, hooks, etc., resembling the opaline bodies which are components of many plants2–4. Van Rummelen5 has figured rods and tubes of isotropic silica from Indonesian soils and has suggested that such particles are always of inorganic origin, being deposited around root hairs which afterwards decay or in soil capillaries. Oosov6 has observed biologically accumulated silica in Russian soils.

Progressive metasomatism in the flint nodules of the Scawt Hill contact-zone

In describing the chief assemblages of the Scawt Hill contact-zone in Co. Antrim brief reference was made to the occurrence of wollastonite and xonotlite associated with the flint nodules of the contact-altered chalk. A more detailed examination of these nodules has now been made and the study of a large number of examples has revealed an interesting group of mineral assemblages which have developed by a progressive metasomatism of these siliceous bodies.

USE OF SPECIAL OXIDES IN PORCELAIN BODIES1

Substitution of special oxides for flint.—The oxides of thorium, titanium and zirconium and the silicate of zirconium were used. Variations in composition were based on batch weights, the percentage of oxide (or silicate) increasing from 27 to 49% with a corresponding decrease in feldspar content. A similar series using flint was also made a basis for comparison. Effect of special oxides on drying and burning behavior, dielectric strength and resistance to spang.—(1) Rutile causes high drying and burning shrinkage. The burning range is long but softening in every case results above cone 12. Resistance to spalling is above normal. (2) Thoria produces a body with a long burning range and great refractoriness. Drying shrinkage is normal, burning shrinkage very high, resistance to spalling very low, and the bodies warp badly. (3) Zirconia bodies have a normal drying shrinkage and a high burning shrinkage, no warping, long firing range, and the highest resistance to spalling. (4) Zircon.—The zirconium silicate bodies soften at temperatures below cone 18 and the firing range is short. Drying and burning shrinkage are similar to flint bodies but resistance to spalling is above normal. Effect of oxides on dielectric resistance.—No effect on dielectric resistance is obtained through the use of the special oxides mentioned.

XXXI.—On the siliceous bodies of the chalk and other formations, in reply to Mr. J. Toulmin Smith

XXXI.—<i>On the siliceous bodies of the chalk and other formations, in reply to</i> Mr. J. Toulmin Smith

XIV.—On the spongeous origin of Moss Agates and other siliceous bodies

(1842). XIV.—On the spongeous origin of Moss Agates and other siliceous bodies. Annals and Magazine of Natural History: Vol. 10, No. 63, pp. 84-91.

IV.—On the spongeous origin of Moss Agates and other siliceous bodies

IV.—On the spongeous origin of Moss Agates and other siliceous bodies

XVII.—On the Siliceous Bodies of the Chalk, Greensands, and Oolites.

Plates XVIII. and XIX. The singular forms presented by the tuberous masses of flint found in the upper chalk have long induced naturalists and geologists to imagine that their forms were derived from Alcyonic or spongeous bodies, but I am not aware that this has hitherto been demonstrated to be the actual fact. Professor Ehrenberg’s observations on siliceous bodies first induced me, in common with many other persons, to cause thin slices of flints to be made, with the intention of procuring specimens of Xanthidia ; and in the examination of these slices I was struck with the frequent occurrence of small patches of a brown reticulated tissue, which always presented nearly the same appearance. The occurrence of this tissue, combined with the circumstance of finding spicula exhibiting nearly the same form and size; and always occurring in about the same proportion, along with numerous foraminated shells and other extraneous bodies, strongly induced me to believe that the brown reticulated tissue was a portion of the remains of the organized body, the shape of which was represented by the flint nodules; and the indications thus observed equally inclined me to believe, that if these flints were fossil organized bodies, they would almost inevitably prove to be sponges. With these views I commenced the investigation of the flints of the chalk, and as a preliminary measure I first examined, in a cursory manner, thin slices of flint nodules from various localities, especially of those from the neighbourhoods of Gravesend and Brighton, and

XXV. Description of the Paramoudra, a singular fossil body that is found in the Chalk of the North of Ireland; with some general Observations upon Flints in Chalk, tending to illustrate the History of their formation.

Among the organic remains of the chalk in the North of Ireland, are large siliceous bodies of a very peculiar character, which I believe have not hitherto been described, and of which the annexed drawing, copied from a sketch I made of them as they appeared, four years ago in some chalk pits near Moira, will give a more correct idea than can be conveyed by any description. * These singular fossils are found in many of the chalk pits from Moira to Belfast and Larne, (see the Map, pl. 8, vol. 3, of the Geol. Trans.) but are most numerous at Moira. They are known at Belfast by the name of Paramoudra, a word which I could trace to no authentic source, but shall adopt because I find it thus appropriated. They have, I believe, never yet been found in the chalk of England, except at Whitlingham near to Norwich, and at some other places in the same neighbourhood, from whence there is a good specimen in the collection of the Geological Society, equal in size to the largest I have seen in Ireland, being about two feet long and one foot in diameter. Through the kindness of my learned friend Dr. Bruce of Belfast, a still more perfect specimen from Moira has been deposited in the Ashmolean Museum at Oxford. * The usual forms of these bodies are modifications of those drawn, more or less elongated or compressed. No two of them are to be found exactly alike in all