Question

What are the structures requires to recognize basaltic layer?

Answer 1

Although basaltic and gabbroic rocks are found in nearly all tectonic settings, they are the predominant igneous rock types of the ocean basins.  Furthermore, basaltic and gabbroic rocks of the ocean basins represent magmas that have the least likelihood of being contaminated with continental crustal material, and thus should give us the best clues to the composition of and chemical evolution of the underlying mantle from which the magmas are derived.  We thus start our discussion with the ocean basins.

Answer 2

Answer:

Basalt is an aphanitic (fine-grained) igneous rock that is relatively low in silica and alkali metals. Of its total content of quartz, feldspar, and feldspathoid (QAPF), less than 10% by volume is feldspathoid and less than 20% is quartz, with plagioclase making up at least 65% of its feldspar content.