Clusters of Moderate Size Earthquakes along Main Central Thrust (MCT) in Himalaya

In recent years I have been disposed to attach more importance than formerly to the general form and macroscopical characters of Eozoön. The earlier examples studied were, for the most part, imbedded in the limestone in such a manner as to give little definite information as to external form; and at a later date, when Sir William Logan employed one of his assistants, Mr. Lowe, to quarry large specimens at Grenville and Côte St. Pierre, the attempt was made to secure the most massive blocks possible, in order to provide large slabs for showing museum specimens. More recently, when collections have been made from the eroded and crumbling surfaces of the limestone in its wider exposures, it was found that specimens of moderate size had been weathered out, and could, either naturally or by treatment with acid, be entirely separated from the matrix. Such specimens sometimes showed, either on the surfaces or on the sides of cavities and tubes penetrating the mass, a confluence of the laminæ, constituting a porous cortex or limiting structure. Specimens of this kind were figured in 1888, and I was enabled to add to the characters of the species that the original and proper form was “broadly turbinate with a depression or cavity above, and occasionally with oscula or pits penetrating the mass.” The great flattened masses thus seemed to represent confluent or overgrown individuals, often contorted by the folding of the enclosing beds.

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Synchrotron FTIR imaging of OH in quartz mylonites

Solid Earth ◽

10.5194/se-8-1025-2017 ◽

2017 ◽

Vol 8 (5) ◽

pp. 1025-1045 ◽

Cited By ~ 5

Author(s):

Andreas K. Kronenberg ◽

Hasnor F. B. Hasnan ◽

Caleb W. Holyoke III ◽

Richard D. Law ◽

Zhenxian Liu ◽

...

Keyword(s):

Water Content ◽

Point Defects ◽

Fluid Inclusions ◽

Hanging Wall ◽

Molecular Water ◽

Main Central Thrust ◽

Absorption Bands ◽

Uniform Equilibrium ◽

Quartz Grains ◽

Water Contents

Abstract. Previous measurements of water in deformed quartzites using conventional Fourier transform infrared spectroscopy (FTIR) instruments have shown that water contents of larger grains vary from one grain to another. However, the non-equilibrium variations in water content between neighboring grains and within quartz grains cannot be interrogated further without greater measurement resolution, nor can water contents be measured in finely recrystallized grains without including absorption bands due to fluid inclusions, films, and secondary minerals at grain boundaries.Synchrotron infrared (IR) radiation coupled to a FTIR spectrometer has allowed us to distinguish and measure OH bands due to fluid inclusions, hydrogen point defects, and secondary hydrous mineral inclusions through an aperture of 10 µm for specimens > 40 µm thick. Doubly polished infrared (IR) plates can be prepared with thicknesses down to 4–8 µm, but measurement of small OH bands is currently limited by strong interference fringes for samples < 25 µm thick, precluding measurements of water within individual, finely recrystallized grains. By translating specimens under the 10 µm IR beam by steps of 10 to 50 µm, using a software-controlled x − y stage, spectra have been collected over specimen areas of nearly 4.5 mm2. This technique allowed us to separate and quantify broad OH bands due to fluid inclusions in quartz and OH bands due to micas and map their distributions in quartzites from the Moine Thrust (Scotland) and Main Central Thrust (Himalayas).Mylonitic quartzites deformed under greenschist facies conditions in the footwall to the Moine Thrust (MT) exhibit a large and variable 3400 cm−1 OH absorption band due to molecular water, and maps of water content corresponding to fluid inclusions show that inclusion densities correlate with deformation and recrystallization microstructures. Quartz grains of mylonitic orthogneisses and paragneisses deformed under amphibolite conditions in the hanging wall to the Main Central Thrust (MCT) exhibit smaller broad OH bands, and spectra are dominated by sharp bands at 3595 to 3379 cm−1 due to hydrogen point defects that appear to have uniform, equilibrium concentrations in the driest samples. The broad OH band at 3400 cm−1 in these rocks is much less common. The variable water concentrations of MT quartzites and lack of detectable water in highly sheared MCT mylonites challenge our understanding of quartz rheology. However, where water absorption bands can be detected and compared with deformation microstructures, OH concentration maps provide information on the histories of deformation and recovery, evidence for the introduction and loss of fluid inclusions, and water weakening processes.

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Formation of moderate-size bubbles

AIChE Journal ◽

10.1002/aic.690090514 ◽

1963 ◽

Vol 9 (5) ◽

pp. 641-645 ◽

Cited By ~ 7

Author(s):

John F. Mahoney ◽

Leonard A. Wenzel

Keyword(s):

Moderate Size

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V. — On the Occurrence of an Opisthocœlian Dinosaur (Algoasaurus Bauri) in the Cretaceous Beds of South Africa

Geological Magazine ◽

10.1017/s0016756800123891 ◽

1904 ◽

Vol 1 (9) ◽

pp. 445-447 ◽

Cited By ~ 12

Author(s):

R. Broom

Keyword(s):

South Africa ◽

Clayey Rock ◽

Moderate Size ◽

Large Numbers ◽

Port Elizabeth ◽

Brick And Tile ◽

Scientific Value

Last year, while the Port Elizabeth Brick and Tile Company were quarrying a clayey rock at Despatch, near Uitenhage, a number of bones were discovered in the rock. Though the discovery created some little interest, no one seems to have appreciated the scientific value of the find, and large numbers of the bones were made into bricks. A few fragments of vertebræ and ribs have been collected by the Port Elizabeth Museum, and recently an attempt has been made to rescue some more of the bones that still remain in the rock. So far a number of very imperfect fragments of vertebræ—cervical, dorsal, and caudal—a fairly good femur, an imperfect scapula, portions of many ribs, and an ungual phalanx, have been discovered. The examination of these remain leaves no doubt that the skeleton is that of an Opisthoeælian Dinosaur of moderate size.

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