The Semail Ophiolite of the Hajar Mountains of Oman and the United Arab Emirates is a large slab of oceanic crust, made of volcanic rocks and ultramafic rocks from the Earth's upper mantle, that was overthrust onto continental crust as an ophiolite.[2] It is located on the eastern corner of the Arabian Peninsula[3] and covers an area of approximately 100,000 km2.[2] Based on uranium-lead dating techniques, the Semail Ophiolite formed in the Late Cretaceous.[4] It is primarily made of silicate rocks with (SiO2) content ranging from 45–77 wt%.[5] The Semail Ophiolite is important because it is rich in copper and chromite ore bodies, and because it also provides valuable information about the ocean floor and the upper mantle on land.[2] Geologists have studied the area, attempting to find the best model explaining the formation of the Semail Ophiolite.