Raman spectroscopic and microthermometric studies of authigenic quartz (the Pepper Mts., Central Poland) as an indicator of fluids circulation

Abstract

Differently colored authigenic quartz crystals were found as the druses compound within mudstone heteroliths from the Pepper Mts. Shale Formation (Cambrian unit of the Holy Cross Mts., Central Poland). The genesis of this mineral was established on the basis of fluid inclusion study. Raman microspectroscopy was the key instrumental technique to identify the nature of the compounds trapped in the fluid inclusions. Methane (2917cm−1) or water vapor (broad band ~2500–3000cm−1) occur within two-phased primary inclusion assemblages, while nitrogen (2329cm−1) associated with methane and trace amount of carbon dioxide (1285, 1388cm−1) occur within secondary fluid inclusion assemblage. Temperatures of homogenization of primary fluid inclusions was obtained on the basis of heating experiments and ranged from 171° to 266°C. These values are much higher than expected for the diagenetic system without metamorphic changes what may imply hydrothermal origin of quartz crystals. The source of fluids is uncertain as in the Holy Cross Mts. there was no volcanic activity to the end of Late Devonian. However, fluids originated in metamorphic basin could use deep faults as the migration paths.