Mineralogy, Geochemistry and Volcanology of Volcanic Tuff Rocks from Jabal Huliat Al-Gran, South of Jordan (New Occurrence)

Abstract

Jabal Huliat Al-Gran (HG) volcano is one of several volcanic eruptions belonging to south Jordanian basaltic eruptions. Thick pyroclastic deposits of volcanic tuff layers alter slowly to complex mineralogical zonations in closed hydrological alkaline environments, and relatively pure deposits can be formed. Hydrological system and temperature are the principal controls over the zeolitization process. This process involves reactions between the vitric silicic volcanic glass and the percolating water in a closed hydrological system to form distinctive zeolite assemblages. Judging from field and experimental data, formation of phillipsite, chabazite and other secondary rock forming minerals probably took place by reaction of percolating water with vitric tuff units. The petrographical, mineralogical and geochemical investigations include thin section, XRD and SEM-EDX to determine the nature, geneses, along with mineralogical and geochemical properties of this new zeolitic occurrence. This work reveals the presence of zeolites in Huliat Al-Gran taffacious materials. Also, the results indicated that the volcanic tuff is highly altered to zeolites and other minerals. The main zeolites are phillipsite Ca-heulandite (mean Si/Al: 3.30) and chabazite Ca-clinoptilolite (mean Si/Al: 4.35). Zeolite minerals compose 10–60% of the whole volcanic tuff rocks. Thermal analysis indicates high stability for temperature difference. The deposit might be of great importance for Jordan, considering its enormous zeolitized outcrop area. However, the quantitative estimation still needs further investigation.