Trace element geochemistry of dispersed organic matter in Western Mecsek uranium ore deposit, Southern Hungary

Abstract

This paper provides analytical insights into the geochemical composition, particularly focusing on gold, of dispersed organic matter (DOM) mainly present within vitrinite and solid bitumen. This DOM is closely associated with uranium ores located within the Late Permian Kővágószőlős Sandstone Formation in Western Mecsek, South-West Hungary. The presence of DOM is notable in the uranium-rich formation of the deposit. However, crucial aspects such as its morphological characteristics, trace element composition, and its relationship with ore minerals are still largely unexplored. The study utilizes a range of techniques, including optical microscopic analysis, maceral and vitrinite reflectance analyses; and trace element measurement using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The analytical data show that DOM has six different morphologies: primary vitrinite, secondary (reworked) vitrinite, inertinite, solid bitumen, pyrobitumen, and graphite. Vitrinite reflectance of DOM ranges from 1.7% to 2.9%. The DOM has average content of Au 0.67 ppm, Ag 7.7 ppm, U 58.8 ppm and Th 22 ppm, As 256 ppm, Cu 91 ppm, Ni 61 ppm, and P 259 ppm. We conclude that DOM exhibits elevated levels of gold and uranium, likely attributed to its deposition under reducing conditions. These findings support the potential use of DOM's trace element composition as an indicator of the formation conditions of ore mineralization. Specifically, our data suggest that using LA-ICP-MS to analyze trace elements, within DOM could serve as a valuable exploration tool within the Kővágószőlős Sandstone Formation in the Western Mecsek deposit.