The late Precambrian mafic dikes of the southern Tobacco Root Mountains, Montana: geochemistry, Rb–Sr geochronology and relationship to belt tectonics

1978 ◽  
Vol 15 (4) ◽  
pp. 467-479 ◽  
Author(s):  
Joseph L. Wooden ◽  
Charles J. Vitaliano ◽  
Steven W. Koehler ◽  
Paul C. Ragland
Keyword(s):  
Mantle Material ◽  
Mountain Area ◽  
Precambrian Rocks ◽  
Southwestern Montana ◽  
Late Precambrian ◽  
High K ◽  
Major Period ◽  
Tobacco Root Mountains ◽  
Low K ◽  
East West

During late Precambrian time three sets of mafic dikes were emplaced in southwestern Montana south of the east–west Helena embayment of the Belt Basin. The oldest dikes, intruded approximately 1455 Ma ago into both the southern Tobacco Root Mountains and the adjoining Ruby Range, are low K tholeiite in composition. The two other sets of dikes were intruded at approximately the same time, about 1120–1130 Ma ago. Both are high K quartz normative types: one is strongly enriched in Fe and is most similar to ferrobasalt or ferrogabbro in composition, the other is low in iron and differentiated along strong alkali and silica enrichment trends. The 1455 Ma old dikes and the iron-enriched 1120 Ma dikes have initial Sr ratios in the range 0.7020–0.7030 that indicate probable derivation from mantle material that has maintained a low Rb–Sr ratio (0.024) for much of the Earth's history. This mantle source is much lower in Rb–Sr ratio than that proposed for the source of dikes in the Beartooth–Bighorn Mountain area to the southeast. The iron-poor 1130 Ma old magma has an initial ratio of 0.709, which suggests contamination by crustal Sr.A strong correlation appears to exist between the timing of mafic intrusive events in the older Precambrian rocks to the south of the Belt Basin and tectonic-intrusive events within the basin. Intrusive events are recorded at 1455–1430 Ma ago both inside and outside the basin. A 1330 Ma old mafic intrusive event in the Beartooth Mountains is associated with a period of metamorphism and (or) a period of deposition in the basin. The 1120–1130 Ma old dikes are correlated with mafic flows and sills and another major period of deposition within the Belt Basin.

The geochemistry and structural significance of a set of Middle Precambrian diabase dikes from the Highland Range, southwestern Montana

1989 ◽  
Vol 26 (1) ◽  
pp. 119-128 ◽  
Author(s):  
Eric Lee Johnson ◽  
Susan M. Swapp
Keyword(s):  
Thermal Effects ◽  
Calcic Plagioclase ◽  
Southwestern Montana ◽  
The North ◽  
Metamorphic Assemblage ◽  
The One ◽  
Tobacco Root Mountains ◽  
East West ◽  
Metasomatic Event ◽  
Structural Significance

The Middle Precambrian diabase dikes of the Highland Range in southwestern Montana are moderate- to high-TiO2 continental tholeiites and are related along a differentiation trend involving strong iron enrichment. Postmagmatic metamorphism and K, Rb, and Sr metasomatism have altered the chemical composition of the igneous rocks of some of the samples. The metamorphic assemblage in the diabase dikes belongs to the low-pressure calcic plagioclase – actinolite hornfels facies, and we suggest that thermal effects associated with the intrusion of the Boulder Batholith are responsible for the metamorphic overprints in these rocks.Combined chemical data from the diabase dikes in the Highland Range, the Ruby Range, and the Tobacco Root Mountains produce smooth differentiation trends for most major oxides and trace elements, and we conclude that one magma was responsible for the dikes in the three ranges. Discrepancies in Rb–Sr age dates obtained for the dikes in the Tobacco Root Mountains can be explained if a Rb, Sr, and K metasomatic event like the one observed in the Highland Range had occurred in the Tobacco Root Mountains as well.Structurally, the diabase dikes in the Highland Range intruded into both east–west- and northwest-trending fractures at the same time. All dikes dip steeply to the north or northeast and are believed to have intruded into tensionally opened fractures related to the opening of the Belt Basin.

Electron Probe Analysis of Vertebrate Smooth Muscle: Distribution of Ca and Ci

1976 ◽  
Vol 34 ◽  
pp. 334-335 ◽  
Author(s):  
Avril V. Somlyo ◽  
H. Shuman ◽  
A.P. Somlyo
Keyword(s):  
Smooth Muscle ◽  
Electron Probe ◽  
Preliminary Report ◽  
Cell Damage ◽  
Electron Probe Analysis ◽  
Perinuclear Space ◽  
Probe Analysis ◽  
High K ◽  
Low K ◽  
Initial Results

This is a preliminary report of electron probe analysis of rabbit portal-anterior mesenteric vein (PAMV) smooth muscle cryosectioned without fixation or cryoprotection. The instrumentation and method of electron probe quantitation used (1) and our initial results with cardiac (2) and skeletal (3) muscle have been presented elsewhere.In preparations depolarized with high K (K2SO4) solution, significant calcium peaks were detected over the sarcoplasmic reticulum (Fig 1 and 2) and the continuous perinuclear space. In some of the fibers there were also significant (up to 200 mM/kg dry wt) calcium peaks over the mitochondria. However, in smooth muscle that was not depolarized, high mitochondrial Ca was found in fibers that also contained elevated Na and low K (Fig 3). Therefore, the possibility that these Ca-loaded mitochondria are indicative of cell damage remains to be ruled out.

High breakdown voltage AlGaN/GaN HEMT with high‐K/low‐K compound passivation

2015 ◽  
Vol 51 (1) ◽  
pp. 104-106 ◽  
Author(s):  
Jiangfeng Du ◽  
Nanting Chen ◽  
Peilin Pan ◽  
Zhiyuan Bai ◽  
Liang Li ◽  
...  
Keyword(s):  
Breakdown Voltage ◽  
Gan Hemt ◽  
High Breakdown Voltage ◽  
High K ◽  
Low K

Pre-Katangan geochronology of Zambia and adjacent parts of Central Africa

1968 ◽  
Vol 5 (3) ◽  
pp. 621-628 ◽  
Author(s):  
J. R. Vail ◽  
N. J. Snelling ◽  
D. C. Rex
Keyword(s):  
Lake Tanganyika ◽  
Central Africa ◽  
New Age ◽  
Orogenic Belt ◽  
Eastern Africa ◽  
Sedimentary Sequence ◽  
Precambrian Rocks ◽  
Late Precambrian ◽  
Orogenic Belts ◽  
Age Determinations

The significance of new age determinations on pre-Katangan (Late Precambrian) rocks and minerals from Zambia and adjacent parts of Tanzania and Rhodesia is discussed. In northwestern Rhodesia, the Lomagundi-Piriwiri sediments were deposited between 2500 and 2000 m.y. ago and were folded along meridional trends at circa 1940 m.y. A later episode of folding and metamorphism along similar trends occurred about 1700 m.y. ago, but only affected the western part of the sedimentary sequence (the Piriwiri Series). This latter date is comparable to that which appears to characterize the Tumbide trend, a N- to NE-trending fold system, in Zambia.In Zambia the Tumbide trend is the oldest tectonic episode preserved in the basement and is found only in isolated blocks and cores into which later tectonisms have not penetrated. The dominant pre-Katangan tectonism is represented by the NE to ENE Irumide trend. Such tectonic trends are particularly well developed in the Irumide Orogenic Belt of northern Zambia and adjacent Tanzania. Age determinations set a younger limit of circa 900 m.y. to this trend and the existence of an Irumide Cycle between about 1600 and 900 m.y. is suggested. The possibility that the relatively unmetamorphosed sediments of the Upper Plateau Series and Abercorn Sandstones at the southern end of Lake Tanganyika, the Mafingi Series of northern Malawi, and the Konse Series of Tanzania, represent near-contemporaneous platform deposition associated with the Irumide belt is considered.From this and other recent studies the distribution of orogenic belts in central and eastern Africa can be revised and a number of features of their pattern and inter-relationships noted.

Cardiac fibrillation in batrachia

1959 ◽  
Vol 197 (6) ◽  
pp. 1157-1160
Author(s):  
H. Mazzella
Keyword(s):  
Electric Shock ◽  
Opposite Effect ◽  
Mechanical Responses ◽  
T Wave ◽  
Mammalian Heart ◽  
Cardiac Fibrillation ◽  
High K ◽  
Bufo Arenarum ◽  
Low K ◽  
Toad Bufo

A study was made of fibrillation and its production in the heart of the toad ( Bufo arenarum). Application of a strong electric shock during the interval of the T wave, or just before, produced fibrillatory response in the ventricle. Repetitive stimuli were necessary for production of fibrillation in the auricle. Fibrillation was of a coarse type but at 37°C it occurred more readily and resembled more nearly that of the mammalian heart. At 5°C the opposite effect occurred. Perfusion of the heart with high K+ solution reduced vulnerability while in low K+ fibrillation occurred more readily. Absence of Ca++ shortened durations of induced fibrillations. Changes in mechanical responses were compared with changes in electrograms.

Enhancement and Modeling of Drain Current in Negative Capacitance Double Gate TFET

2021 ◽  
Author(s):  
SHIKHA U S ◽  
Rekha K James ◽  
Jobymol Jacob ◽  
Anju Pradeep
Keyword(s):  
Drain Current ◽  
Gate Oxide ◽  
Negative Capacitance ◽  
Double Gate ◽  
High K ◽  
Gate Control ◽  
Effect Transistor ◽  
Dimensional Simulation ◽  
The Impact ◽  
Low K

Abstract The drain current improvement in a Negative Capacitance Double Gate Tunnel Field Effect Transistor (NC-DG TFET) with the help of Heterojunction (HJ) at the source-channel region is proposed and modeled in this paper. The gate oxide of the proposed TFET is a stacked configuration of high-k over low-k to improve the gate control without any lattice mismatches. Tangent Line Approximation (TLA) method is used here to model the drain current accurately. The model is validated by incorporating two dimensional simulation of DG-HJ TFET with one dimensional Landau-Khalatnikov (LK) equation. The model matches excellently with the device simulation results. The impact of stacked gate oxide topology is also studied in this paper by comparing the characteristics with unstacked gate oxide. Voltage amplification factor (Av), which is an important parameter in NC devices is also analyzed.

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