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Full-Text Articles in Life Sciences

High Precision, High Spatial Resolution Analysis Of Sulfur Isotopes By Laser Combustion Of Natural Sulfide Minerals, S. P. Kelley, A. E. Fallick, P. Mcconville, A. J. Boyce Mar 1992

High Precision, High Spatial Resolution Analysis Of Sulfur Isotopes By Laser Combustion Of Natural Sulfide Minerals, S. P. Kelley, A. E. Fallick, P. Mcconville, A. J. Boyce

Scanning Microscopy

Laser induced combustion provides a powerful new technique for sulfur isotope measurements in natural sulfides. A high power continuous laser, focused through a modified microscope system onto a sulfide mineral target, produces highly localized heating. The laser beam is focused to a spot 25 μm in diameter at the sample surface. In the presence of low pressure oxygen, temperatures at the centre of the spot are sufficiently high to produce localized oxidation. Resultant SO2 is transferred to a gas source isotope ratio mass spectrometer, where the 𝛿34S can be measured to a precision better than 0.25 ...


Geology Of Iowa Fens, C. A. Thompson, E. A. Bettis Iii, R. G. Baker Jan 1992

Geology Of Iowa Fens, C. A. Thompson, E. A. Bettis Iii, R. G. Baker

Journal of the Iowa Academy of Science: JIAS

Fens are peatlands which are dependent on groundwater discharge to provide nutrient enrichment. Fens are found in a variety of landscape positions and in most Iowa landform regions. This paper presents a classification system for Iowa fens based on landscape position, stratigraphy, and hydrologic factors. Iowa fens can be separated into six categories: 1) fens along valley wall slopes; the groundwater source for these fens is sand and gravel buried between glacial tills (inter-till); 2) fens in hummocky topography on the northwestern margin of the Des Moines Lobe landform region; the water source is sand and gravel buried within glacial ...