Cryptic Mantle Metasomatism: Evidences from Spinel Lherzolite Xenoliths/Al-Harida Volcano in Harrat Al-Shaam, Jordan

Problem statement: Al-Harida volcano is located in the Jordanian parts of the Harrat Al-Shaam plateau and contains considerable amounts of mantle xenoliths within its pyroclastic successions. Approach: These xenoliths are reported for the first time for this area. Mineralogical investigations show that they are composed of olivine, orthopyroxene, clinopyroxene, spinel and phlogopite. Results: The xenoliths range in size from 5-30 cm with an average of 10 cm. They are classified as Type I and belong to the Cr-diopside group and are characterized by high contents of MgO, Cr and Ni. The occurrence of hydrous mineral phases and the enrichment of incompatible elements such as Sr, Rb and Ba indicate a considerable mantle metasomatism. Conclusion/Recommendations: Thermobarometry of the studied xenoliths indicates a temperature ranging from 960-1040°C and pressure ranging from 11-13 Kbar which corresponds to a depth of origin of about 43 km.