Provenance analysis and gamma-ray spectra of carboniferous flysch sediments (bohemian massif, czech republic)

摘要

We studied the relationships between field- and laboratory gamma-ray spectra (GRS) and mineral and chemical composition (modal analysis, cathodoluminiscence /CL/ microscopy, electron microprobe analysis) of Lower Carboniferous foreland-basin turbidities (Moravice formation, Bohemian Massif). The aim was to trace detrital provenance changes across stratigraphy. The average sandstone modal composition corresponds to quartzofeldspathic arenites with predominantly recycled orogen provenance. There is a net increase of K, U and Th concentrations towards younger strata. Local, facies independent K and Th maxima were found in both shales and sandstones of the middle parts of the formation (Brumovice member), the latter corresponding to transitional continent- and basement uplift tectonic provenance. CL and microprobe analyses revealed that most of the K and Th signal is carried by K-feldspars, musco-vite, sericite and heavy minerals including monazite, thorite, xenotime and apatite, which form frequent inclusions in K-feldspars. We conclude that GRS has a good potential for detrital provenance studies.