NEW INSIGHTS INTO THE AGE OF BURIED CONTINENTAL LITHOSPHERE OF ARABIA

Crustal geophysical studies like those of Randy Keller’s groups at UTEP and Oklahoma U have provided important new insights into the structure of continental crust but always we need to study samples of geophysically-imaged crust in order to determine its age and thus its significance. Getting this information for continental crust buried beneath water or sediments poses special challenges; without radiometrically samples it is equally reasonable to assume that buried crust must be very like or very different from that of the nearest exposed crust. Where there are marine shelves or thick sediments there is often drilling for oil but the barriers to academic and industrial geoscientific co-operation seem to get stronger with time. Instead, academic geoscientists can exploit accidents of Nature and amazing advances in microanalytical techniques to resolve the age of buried crust. These insights can be include obtained using from diverse samples, such as detrital zircons in sandstones and xenoliths brought up by volcanoes and salt domes. Three examples of our advancing understanding of buried Arabian continental crust show how much we have to learn and how we can learn it. 1. Ages of detrital zircons in the well-studied Neoproterozoic Huqf Group of Oman along with scattered basement exposures in Oman demonstrate that buried crust east of the Arabian Shield is also a Neoproterozoic construct that differs from that of the Shield to the west in having stabilized earlier, by ~750 Ma, with a major N-S crustal structure (the Central Magnetic Anomaly) separating crust of the Arabian Shield from deeply buried of the Arabian Platform to the east. 2. Neogene lava flows in Jordan and Syria north of the Arabian Shield bring up crustal xenoliths that sample Carboniferous and Cadomian (520-600 Ma) crust beneath northern Arabia. 3. Thomas et al. (2015) studied rocks brought to the surface by salt domes in the United Arab Emirates, documenting the presence of Cadomian crust 8 km deep.