Peperites and associated pillow lavas subjacent to the Oman Ophiolite

Peperites are breccias consisting of a mix of cooled magma and sediment. They result from the intrusion of molten rock into water-saturated sediments. We report an occurrence of peperite in the Oman—United Arab Emirates (UAE) border region of Khattm al Shiklah, and characterize samples that have been collected from 6 locations east of Al Ain, UAE at Jabal Um Bak Jabal Hamra, and Jabal Dai in Oman. Geochemical analysis indicates that the magmas represented in these samples are related. In addition, field relations of the pillow lavas surrounded by limestone with deformed bedding and peperite boundaries between the pillows and the limestone are consistent with the pillow lavas forming directly within carbonate sediments. It is likely that the ambient pressure was great enough and cooling of the magma rapid enough to prevent large explosions. The fact that the magma also formed pillows is evidence of this. The rapid quenching of the magma by water-saturated, fine, unconsolidated sediments likely produced conditions similar to those attending pillow lava formation directly into water.