Geology and Mineralogy of Zeolitic Tuff in Tulul Unuqar Rustum Ash Shmaliyya, NE JORDAN

Detailed geological mapping and drilling campaign in Tulul Unuqar Rustum Ash Shamaliyya (URS) volcanic center have been carried out to evaluate the geology and mineralogy of zeolitic tuff. The most abundant rock type in the volcano is scoriaceous tuff and zeolitic tuff. The zeolites occur as cement to palagonite clasts and as filling inside the vesicles, making about 30% of the rock. Phillipsite is the most abundant zeolites mineral with spherulitic radiating aggregates or stout- prismatic crystals. The second zeolites mineral is chabazite which occurs as rhombohedra with simple penetrating twinning. Chemical analysis of the phillipsite indicates that they are K-rich type with similar Na/K and Ca/K ratios and has small variation in the Si/Al ratio. The zeolitic tuff samples have a wide range of SiO2 content indicating wide range of alteration and formation of authigenic minerals. The model of zeolites formation in the URS volcano is believed to be an open hydrological system model, where soluble elements released from the fresh basaltic glass by the hydrolysis reaction due to the raised higher pH and saline conditions, re-deposited in the of form zeolites, smectite and calcite.