Th∕K and Th∕U Ratios from Spectral Gamma-Ray Surveys Improve the Mapped Definition of Subsurface Structures

Abstract

Spectral gamma-ray data can be obtained by non-destructive, automated, rapid and inexpensive survey methods. Previous studies utilise only total count, or total count as well as K, U and Th data. This work examines the use of [Formula: see text] and [Formula: see text] ratios to define the subsurface extent of partially-buried features at the centimeter to meter scale. On-site results are presented from two case studies as two-dimensional cross-sections. Changes in [Formula: see text] and [Formula: see text] ratios coincide with the known location of buried structures to within [Formula: see text] horizontal resolution. Gradual changes in total count, K, U and Th measurements give a lower horizontal accuracy of [Formula: see text]. Grids of data were manipulated in ArcGIS™ using a thin plate spline function to maximise information use and provide ‘easy to interpret’ maps of the survey areas. Unlike total count or individual element maps, [Formula: see text] and [Formula: see text] ratio maps can be compared to the known location of subsurface structures, vindicating the use of ratio cross-sections and maps in archaeological, geotechnical and forensic applications. It is concluded that the capacity to observe sub-surface features is enhanced through the use of [Formula: see text] and [Formula: see text] ratios.

Evaluation of shales of the Belaga Formation in Central Sarawak, Malaysia, using the Spectral Gamma Ray method

“…Th/K can be used as a proxy for paleoclimate analysis (Ruffell & Worden, 2000;Ruffell et al, 2006). Most likely, the 30Ma interval of sediment deposition of the Belaga Formation recorded varied climatic conditions of which clay minerals of the shales are instrumental proxies as directly relational to Th/K.…”

“…The advent of various instrumentation such as the Spectral Gamma Rays (SGR) detector has gained acceptance in the global energy industry as an important non-destructive, automated, rapid and inexpensive survey tool for petro-mineralogical and geophysical assessment using radio-isotropy as its mode of determination of clay content, evaluation of clay mineralogy, identification of fissure zones, organic matter quantification, reservoir characterization, source rock evaluation and depiction of sedimentary conditions and processes which proves their wide acceptance in the areas of sedimentology and stratigraphy (Ruffell et al, 2006;Schnyder et al, 2006;Klaja & Dudek, 2016).…”

Identification of Clay Mineral Content Using Spectral Gamma Ray on Y1 Well in Karawang Area, West Java, Indonesia.

“…The measuredenergy spectrum is transformed into Schlumberger 1982). The advent of various instrumentation such as the detector has gained acceptance in the global energy industry as an destructive, automated, rapid and inexpensive surveytool for petromineralogical and geophysical assessment using radioisotropy as its mode of determination of clay content, evaluation of clay mineralogy, identification offissure zones, organic matter quantification, reservoir charac source rock evaluation and depiction of sedimentary conditions and processes which proves their wide acceptance in the areas of sedi stratigraphy (Ruffell et al, 2006;Schnyder et al, 2006;Klaja & Dudek, 2016).…”

“…The RCIII has supported texture and most of the K is hosted in feldspar. Overall, the laboratory measurements appear to be applicable to the log data, and, using SEM or XRD, the detail facies subdivision can be extended clay mineralogy, identification offissure zones, organic matter quantification, reservoir characterization, source rock evaluation and depiction of sedimentary conditions and processes which proves their wide acceptance in the areas of sedimentology and Ruffell et al, 2006;Schnyder et al, 2006; Karawang area, SNG core was performed in order todifferentiate micaceous sand from shale. The purpose ofthis study the radioactive minerals in the shale and to estimate their contribution to ray spectrum.…”

(Ijcesen)

“…Radiometry is one of the most powerful and rapid methods to obtain information about the distribution and concentration of radionuclides (eU, eTh and K (%)) at any location [2]. Thus some previous researches [12][13][14][15][16][17] using this method indicate that it is also possible to perform radiological hazard, geological, geotechnical and geochemical mapping of a study area.…”