Thermal infrared exploration in the Carlin trend, northern Nevada

Geophysics ◽  
1990 ◽  
Vol 55 (1) ◽  
pp. 70-79 ◽  
Author(s):  
Kenneth Watson ◽  
Fred A. Kruse ◽  
Susanne Hummer‐Miller
Keyword(s):  
Physical Properties ◽  
Volcanic Rocks ◽  
Thermal Inertia ◽  
Thermal Infrared ◽  
Silica Content ◽  
Geologic Materials ◽  
Northern Nevada ◽  
Geologic Maps ◽  
High Silica ◽  
First Time

Experimental Thermal Infrared Multispectral Scanner (TIMS) aircraft data have been acquired for the Rodeo Creek NE 7 1/2 minute quadrangle, Eureka County, northern Nevada, covering the Carlin gold mine. A simple model has been developed to extract spectral emissivities for mapping surface lithology and alteration based on the physical properties of geologic materials. Emissivity‐ratio images were prepared that allow generalized lithologic discrimination, identification of areas with high silica content, and the first reported detection of the carbonate secondary reststrahlen feature. Together with thermal‐inertia images, they permit identification of areas of subtle lithologic variation not shown on conventional geologic maps. Emissivity‐ratio spectra extracted from the data compare favorably with modeled laboratory spectra and establish for the first time the link among theory, measured physical properties, and color‐composited TIMS images. Identification of previously unknown silicification in the Tertiary volcanic rocks and mapping of a silicified structure and possible extensions in alluvium indicate that TIMS data can be a valuable tool for detecting subtle alteration associated with mineralization, particularly in less accessible or less well‐known areas.

Regional thermal‐inertia mapping from an experimental satellite

Geophysics ◽  
1982 ◽  
Vol 47 (12) ◽  
pp. 1681-1687 ◽  
Author(s):  
Kenneth Watson
Keyword(s):  
Satellite Data ◽  
Thermal Model ◽  
Thermal Inertia ◽  
Powder River Basin ◽  
Geochemical Data ◽  
Preliminary Assessment ◽  
Geologic Materials ◽  
Thermal Data ◽  
Resource Exploration ◽  
First Time

A new experimental satellite has provided, for the first time, thermal data that should be useful in reconnaissance geologic exploration. Thermal inertia, a property of geologic materials, can be mapped from these data by applying an algorithm that has been developed using a new thermal model. A simple registration procedure was used on a pair of day and night images of the Powder River basin, Wyoming, to illustrate the method. Preliminary assessment of these satellite data suggests that they will be of significant use for resource exploration when used in conjunction with other geologic, geophysical, and geochemical data.

Investigations of electrical properties of weathered layers in the Yala area, western Kenya, using resistivity soundings

Geophysics ◽  
1991 ◽  
Vol 56 (1) ◽  
pp. 133-138 ◽  
Author(s):  
J. O. Barongo ◽  
G. J. Palacky
Keyword(s):  
Electrical Properties ◽  
Volcanic Rocks ◽  
Silica Content ◽  
Data Sets ◽  
Geologic Mapping ◽  
Weathering Profile ◽  
Western Kenya ◽  
Tropical Regions ◽  
Weathered Layer ◽  
First Time

Investigation in many parts of the world have indicated that resistivity of saprolite (a chloritization zone at the base of the weathering profile) depends uniquely on the underlying rock type. A study of electrical properties of the weathered layer was undertaken near Yala in the Nyanzian‐Kavirondian greenstone belt in western Kenya. Resistivity soundings were systematically carried out in a 24 × 40 km area. Saprolite formed over basalt had the lowest resistivity (14 Ω•m), followed by andesite (27 Ω•m) and rhyolite (67 Ω•m). Statistically meaningful data sets conclusively show, for the first time, that saprolite resistivity increases with the silica content of parent volcanic rocks. Plutonic and sedimentary rocks had higher average resistivities (granite 135 Ω•m, mudstone 79 Ω•m, grit 213 Ω•m). Thickness of the weathered layer varied between 10 and 40 m, with the largest values observed over grit (sandstone). Compared with other tropical regions, the saprolite layer in western Kenya appears relatively thin, possibly because of the relatively rapid tectonic uplift of the area which leads to fast erosion. As observed in earlier studies, resistivity and electromagnetic surveys can increase the speed and reliability of geologic mapping in tropical terrains.

Geology of the Springdale Group: a newly recognized Silurian epicontinental-type caldera in Newfoundland

1987 ◽  
Vol 24 (6) ◽  
pp. 1135-1148 ◽  
Author(s):  
Marylou Coyle ◽  
D. F. Strong
Keyword(s):  
Large Scale ◽  
Basaltic Magma ◽  
Volcanic Rocks ◽  
Sedimentary Facies ◽  
Volcanic Field ◽  
Silica Content ◽  
Large Area ◽  
Basement Rocks ◽  
Iapetus Ocean ◽  
High Silica

Volcanic–sedimentary facies and structural relationships of the Silurian Springdale Group in west-central Newfoundland are indicative of a large collapse caldera with an area of more than 2000 km2. Basaltic flows, andesite flows and pyroclastic rocks, silicic ash-flow tuffs, high-silica rhyolite domes, and volcanically derived debris flows and breccias, fluviatile red sandstones, and conglomerates make up the group. It is bounded on the east and west by up-faulted basement rocks, which include gneisses, amphibolites, and pillow lavas, and in the northwest it unconformably overlies Lower Orodovician submarine volcanics. These margins are intruded by cogenetic and younger granitoid rocks. The volcanic rocks form a calc-alkaline series, although gaps in silica content at 52–56, 67–68, and 73–74% separate them into four groups: basalts, andesites–dacites, rhyolites, and high-silica rhyolites.The high-silica rhyolites are chemically comparable to melts thought to form the upper parts of large, layered silicic magma chambers of epicontinental regions. Such an environment is also suggested by the large area of the Springdale caldera and the fact that it is one of a number of calderas that make up a large Silurian volcanic field in western Newfoundland. An epicontinental tectonothermal environment for central Newfoundland in Silurian–Devonian times is readily explained by the fact that this magmatic activity followed a period of destruction and closure of the early Paleozoic Iapetus Ocean, with trapped heat and basaltic magma causing large-scale melting of thickened and subducted continental crust in an overall transpressional tectonic regime.

Hydration Reactions in Cement Pastes Incorporating Fly Ash and Other Pozzolanic Materials

1986 ◽  
Vol 86 ◽  
Author(s):  
F. P. Glasser ◽  
S. Diamond ◽  
D. M. Roy
Keyword(s):  
Fly Ash ◽  
Physical Properties ◽  
Silica Content ◽  
Cement Pastes ◽  
Blended Cements ◽  
Natural Pozzolans ◽  
High Calcium ◽  
High Silica ◽  
Class F Fly Ash

ABSTRACTA model for reactions that occur in hydrating portland cement is now generally well developed. Incorporation of various by-products to form blended cements modifies both the hydration reactions and the physical properties of the resulting pastes. A review of recent progress in understanding the effects of blending agents on these reactions is presented. The blending agents considered are low-calcium (Class F) fly ash, high calcium (Class C) fly ash, blast furnace slag, silica fume, biosilica and natural pozzolans. Effects of the blending agents on physical properties such as rheology are also considered. Particular attention is given to the essential role of alkalies in pore solutions and the beneficial reactions that occur with high silica content blending agents.

Hydration Reactions in Cement Pastes Incorporating Fly Ash and Other Pozzolanic Materials

1986 ◽  
Vol 85 ◽  
Author(s):  
F. P. Glasser ◽  
S. Diamond ◽  
D. M. Roy
Keyword(s):  
Fly Ash ◽  
Physical Properties ◽  
Silica Content ◽  
Cement Pastes ◽  
Blended Cements ◽  
Natural Pozzolans ◽  
High Calcium ◽  
High Silica ◽  
Class F Fly Ash

ABSTRACTA model for reactions that occur in hydrating portland cement is now generally well developed. Incorporation of various by-products to form blended cements modifies both the hydration reactions and the physical properties of the resulting pastes. A review of recent progress in understanding the effects of blending agents on these reactions is presented. The blending agents considered are low-calcium (Class F) fly ash, high calcium (Class C) fly ash, blast furnace slag, silica fume, biosilica and natural pozzolans. Effects of the blending agents on physical properties such as rheology are also considered. Particular attention is given to the essential role of alkalies in pore solutions and the beneficial reactions that occur with high silica content blending agents.

scholarly journals Geometric correction for thermographic images of asteroid 162173 Ryugu by TIR (thermal infrared imager) onboard Hayabusa2

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Takehiko Arai ◽  
Tatsuaki Okada ◽  
Satoshi Tanaka ◽  
Tetsuya Fukuhara ◽  
Hirohide Demura ◽  
...  
Keyword(s):  
Surface Roughness ◽  
High Surface ◽  
Thermal Inertia ◽  
Thermal Infrared ◽  
Shape Model ◽  
Infrared Imager ◽  
Least Squares Fit ◽  
Temperature Maps ◽  
Pixel Scale ◽  
Thermal Infrared Imager

AbstractThe thermal infrared imager (TIR) onboard the Hayabusa2 spacecraft performed thermographic observations of the asteroid 162173 Ryugu (1999 JU$$_3$$ 3 ) from June 2018 to November 2019. Our previous reports revealed that the surface of Ryugu was globally filled with porous materials and had high surface roughness. These results were derived from making the observed temperature maps of TIR using a projection method onto the shape model of Ryugu as geometric corrections. The pointing directions of TIR were calculated using an interpolation of data from the SPICE kernels (NASA/NAIF) during the periods when the optical navigation camera (ONC) and the light detection and ranging (LIDAR) observations were performed. However, the mapping accuracy of the observed TIR images was degraded when the ONC and LIDAR were not performed with TIR. Also, the orbital and attitudinal fluctuations of Hayabusa2 increased the error of the temperature maps. In this paper, to solve the temperature image mapping problems, we improved the correction method by fitting all of the observed TIR images with the surface coordinate addressed on the high-definition shape model of Ryugu (SFM 800k v20180804). This correction adjusted the pointing direction of TIR by rotating the TIR frame relative to the Hayabusa2 frame using a least squares fit. As a result, the temperature maps spatially spreading areas were converged within high-resolved $$0.5^\circ$$ 0 . 5 ∘ by $$0.5^\circ$$ 0 . 5 ∘ maps. The estimated thermal inertia, for instance, was approximately 300$$\sim$$ ∼ 350 Jm$$^{-2}$$ - 2 s$$^{-0.5}$$ - 0.5 K$$^{-1}$$ - 1 at the hot area of the Ejima Saxum. This estimation was succeeded in case that the surface topographic features were larger than the pixel scale of TIR. However, the thermal inertia estimation of smooth terrains, such as the Urashima crater, was difficult because of surface roughness effects, where roughness was probably much smaller than the pixel scale of TIR.

scholarly journals ASKAP observations of multiple rapid scintillators reveal a degrees-long plasma filament

2021 ◽  
Vol 502 (3) ◽  
pp. 3294-3311
Author(s):  
Yuanming Wang ◽  
Artem Tuntsov ◽  
Tara Murphy ◽  
Emil Lenc ◽  
Mark Walker ◽  
...  
Keyword(s):  
Physical Properties ◽  
Angular Width ◽  
Scattering Medium ◽  
Central Frequency ◽  
Linear Arrangement ◽  
Plasma Filament ◽  
Kinematic Models ◽  
Tidal Stream ◽  
First Time ◽  
Insight Into

ABSTRACT We present the results from an Australian Square Kilometre Array Pathfinder search for radio variables on timescales of hours. We conducted an untargeted search over a 30 deg2 field, with multiple 10-h observations separated by days to months, at a central frequency of 945 MHz. We discovered six rapid scintillators from 15-min model-subtracted images with sensitivity of $\sim\! 200\, \mu$Jy/beam; two of them are extreme intra-hour variables with modulation indices up to $\sim 40{{\ \rm per\ cent}}$ and timescales as short as tens of minutes. Five of the variables are in a linear arrangement on the sky with angular width ∼1 arcmin and length ∼2 degrees, revealing the existence of a huge plasma filament in front of them. We derived kinematic models of this plasma from the annual modulation of the scintillation rate of our sources, and we estimated its likely physical properties: a distance of ∼4 pc and length of ∼0.1 pc. The characteristics we observe for the scattering screen are incompatible with published suggestions for the origin of intra-hour variability leading us to propose a new picture in which the underlying phenomenon is a cold tidal stream. This is the first time that multiple scintillators have been detected behind the same plasma screen, giving direct insight into the geometry of the scattering medium responsible for enhanced scintillation.

Influence of alteration on physical properties of volcanic rocks

2012 ◽  
Vol 566-567 ◽  
pp. 67-86 ◽  
Author(s):  
Antonio Pola ◽  
Giovanni Crosta ◽  
Nicoletta Fusi ◽  
Valentina Barberini ◽  
Gianluca Norini
Keyword(s):  
Physical Properties ◽  
Volcanic Rocks

Strontium 87 abundance in a suite of Hawaiian volcanic rocks of varying silica content

1965 ◽  
Vol 70 (6) ◽  
pp. 1509-1513 ◽  
Author(s):  
J. L. Powell ◽  
G. Faure ◽  
P. M. Hurley
Keyword(s):  
Volcanic Rocks ◽  
Silica Content

scholarly journals Background Error in WRF Model

2020 ◽  
Vol 16 ◽  
Keyword(s):  
Data Assimilation ◽  
Physical Properties ◽  
Covariance Matrix ◽  
Numerical Weather Prediction ◽  
Weather Prediction ◽  
Wrf Model ◽  
Background Error ◽  
Numerical Weather ◽  
Error Covariance ◽  
First Time

WRF model have been tuned and tested over Georgia’s territory for years. First time in Georgia theprocess of data assimilation in Numerical weather prediction is developing. This work presents how forecasterror statistics appear in the data assimilation problem through the background error covariance matrix – B, wherethe variances and correlations associated with model forecasts are estimated. Results of modeling of backgrounderror covariance matrix for control variables using WRF model over Georgia with desired domain configurationare discussed and presented. The modeling was implemented in two different 3DVAR systems (WRFDA andGSI) and results were checked by pseudo observation benchmark cases using also default global and regional BEmatrixes. The mathematical and physical properties of the covariances are also reviewed.

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