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Full-Text Articles in Physical Sciences and Mathematics
Ar-40/Ar-39 Evidence For Middle Proterozoic (1300-1500 Ma) Slow Cooling Of The Southern Black Hills, South Dakota, Midcontinent, North America: Implications For Early Proterozoic P-T Evolution And Posttectonic Magmatism, Daniel Holm, Peter Dahl, Daniel R. Lux
Ar-40/Ar-39 Evidence For Middle Proterozoic (1300-1500 Ma) Slow Cooling Of The Southern Black Hills, South Dakota, Midcontinent, North America: Implications For Early Proterozoic P-T Evolution And Posttectonic Magmatism, Daniel Holm, Peter Dahl, Daniel R. Lux
Peter Dahl
Ar-40/Ar-39 total gas and plateau dates from muscovite and biotite in the southern Black Hills, South Dakota, provide evidence for a period of Middle Proterozoic slow cooling. Early Proterozoic (1600-1650 Ma) mica dates were obtained from metasedimentary rocks located in a synformal structure between the Harney Peak and Bear Mountain domes and also south of Bear Mountain. Metamorphic rocks from the dome areas and undeformed samples of the similar to 1710 Ma Harney Peak Granite (HPG) yield Middle Proterozoic mica dates (similar to 1270-1500 Ma). Two samples collected between the synform and Bear Mountain dome yield intermediate total gas mica …
Petrographic And Physical Factors Controlling Thermal-Conductivity Of Granitic-Rocks In Illinois Deep Holes Uph 1, 2, And 3, Yoram Eckstein, Peter Dahl, Charles J. Vitaliano
Petrographic And Physical Factors Controlling Thermal-Conductivity Of Granitic-Rocks In Illinois Deep Holes Uph 1, 2, And 3, Yoram Eckstein, Peter Dahl, Charles J. Vitaliano
Peter Dahl
Twenty-four granitic core samples from the Illinois deep drill holes yield thermal conductivity values in the range 29.3–37.6 mW/cm °C, wet bulk densities in the range 2.608–2.960 g/cm3, and water accessible porosity in the range 0.12–0.78%. Thermal conductivity values vary with modal quartz content of the rocks at all depths, and both parameters decrease linearly with depth between 673 and 1016 m in drill hole UPH 3. Below 1070 m there is no systematic variation in modal quartz content with depth and hence no systematic variation in thermal conductivity. Similarly, no systematic variations in modal quartz or physical …
Granitic Rocks From 3 Deep Drill-Holes, Illinois, Charles J. Vitaliano, George R. Mccormick, Peter Dahl, Yoram Eckstein
Granitic Rocks From 3 Deep Drill-Holes, Illinois, Charles J. Vitaliano, George R. Mccormick, Peter Dahl, Yoram Eckstein
Peter Dahl
A medium- and coarse-grained granite has been encountered in the lower 914 m of deep drill-holes in northwestern Illinois. The mineralogy and chemistry of both types of granite suggest they are anorogenic A-type granites after the definition of Loiselle and Wones (1979). The major oxide composition for both types is nearly identical. Trace element data (Rb, Y, Th) indicate the medium-grained granite crystallized from a more evolved melt than did the coarse-grained granite. Trace element data (Y, Th, Ba, Sr) for the coarsegrained granite show it to be slightly zoned from the bottom upward to the contact with the medium-grained …
Concentric Slow Cooling Of A Low P-High T Terrain: Evidence From 1600-1300 Ma Mica Dates In The 1780-1700 Ma Black Hills Orogen, South Dakota, Usa, Peter Dahl, K. A. Foland
Concentric Slow Cooling Of A Low P-High T Terrain: Evidence From 1600-1300 Ma Mica Dates In The 1780-1700 Ma Black Hills Orogen, South Dakota, Usa, Peter Dahl, K. A. Foland
Peter Dahl
No abstract provided.
Influence Of F(Oh)(-1) Substitution On The Relative Mechanical Strength Of Rock-Forming Micas, Peter Dahl, Michael J. Dorais
Influence Of F(Oh)(-1) Substitution On The Relative Mechanical Strength Of Rock-Forming Micas, Peter Dahl, Michael J. Dorais
Peter Dahl
Microtextural and experimental studies have yielded conflicting data on the relative mechanical strengths of muscovite and biotite [Wilson and Bell, 1979; Kronenberg et al., 1990; Mares and Kronenberg, 1993]. We propose a crystal-chemical resolution to this conflict, namely, that (001) dislocation glide in biotite is rate-limited by its fluorine content. Significant F(OH)−1 substitution, and concomitant removal of hydroxyl H+ directed into the interlayer cavity, potentially increases mechanical strength of biotite in two ways: (1) it eliminates K+-H+repulsion, thereby strengthening the interlayer bonds, and (2) it allows K+ to “sink” …