Sialic

Near-synonym: ensialic

The total volume of these felsic rocks, variously estimated at 3 to 9 percent of the Cenozoic section, is much greater in Iceland than on other oceanic islands, and their abundance led early geologists to speculate that Iceland might be a small continental fragment covered by a thin veneer of basalt. Geophysical and petrologic evidence now rules out any possibility of sialic crust under the island. The siliceous differentiates have little or no potassium feldspar and differ from typical continental rhyolites and granites in their trace-element abundances and isotopic ratios.