Mineral and Geochemical Approaches to Identify the Origin of Analcime in the Middle Carboniferous Dimbabah Formation, South-Western Libya

The Dimbabah Formation, representing the final marine deposits in the Murzuq Basin, is widely exposed in various regions, including Al Awaynat, Wadi Irawan, Hasi Anjiwal, Biʼr Anzawa, Jabal Ati, the Anay region, and Hamadat Tanghirt. The presence of analcime within the Dimbabah Formation has raised questions about its origin, whether volcanic or lacustrine. Therefore, his study aimed to decipher the enigmatic occurrence of the analcime within the formation. X-ray diffraction (XRD) was used to identify the mineral composition of selected samples from representing two distinctive facies from the analcime beds. Also, X-ray flourecence (XRF) was used to investigate the bulk chemical composition. Scanning electron microscopy (SEM) and energy dispersive spectrometry (EDAX) was also used in this study to investigate the mineralogy and the chemistry of the selected samples. Based on these analyses and mineral associations, the analcime bed is interpreted as lacustrine deposits, suggesting the presence of an ancient playa lake or arid lagoon adjacent to the shoreline, potentially fed by one or more river tributaries. These evidences supported sedimentologically by the nature of analcime as oolitic and pseudo-oolitic, and the mud cracks within the facies. Althoght the volcanic ash was not observed in the sediments of the analcime beds, the volcanic materials contribution is not excluded since the eriontite and clinoptilolite zeolites are still recognized through the XRD analysis. Also, the geochemical data of the Dimbabah Formation's sample are nearly paired with igneous-type analcime.