A contribution to sustainable mining

Background/Summary

For more than 100 years, the saline deposits of the Werra-Fulda-Potassium district are mined. These salts are mainly used for mineral fertilizers and the chemical industry. During volcanic phases in the Paleogene and Neogene (Rhön and Vogelsberg volcanism) mafic rocks intruded into the salt rocks (Zechstein) of the Werra Formation. Diagenesis and the mafic intrusions are accompanied by a fluid and gas flux. For safety reasons, potential occurrences of CO₂ and other gases within the salt-rocks must be explored and monitored in the mining process. At lithostatic pressure the gases may be in a liquid or in an overcritical state. If the pressure decreases due to mining and drilling activities, the gases can be released causing safety risks.

To better predict potential gas occurrences and their hazardous potential, a cooperation between the Institute of Geosciences (research groups “Thermochronology und Archäometry”, (Prof. Dr. U. A. Glasmacher) and “Biogeochemistry” (Prof. Dr. F. Keppler)) and the K+S Aktiengesellschaft was formed.

The Biogeochemistry group analyzes the gas content of mafic and salinar rocks. We analyze atmospheric gases as well as hydrocarbons and methyl chloride (GC-BID; GC-FID; GC-MS). Additionally, we analyze the ratio of the stable isotopes of CO₂ and CH₄ (GC-IRMS), hoping to find the origin of these gases and their area of distribution to ensure safe and sustainable mining. As a reference and for a better understanding of volcanic gases we, additionally, analyze the outgassing of the Laacher See region.

Another focus of interest is the ratio of O₂ to N₂ within the salt rocks’ fluid inclusions. With the O₂ to N₂ ratio of fluid inclusions in unaltered salts we hope to analyze and reconstruct the oxygen level between the Permian and and the Muschelkalk. This could potentially be one of the oldest direct atmospheric archive so far.