In contrast to the Proterozoic, Archean rocks are often heavily metamorphized deep-water sediments, such as graywackes, mudstones, volcanic sediments and banded iron formations. Greenstone belts are typical Archean formations, consisting of alternating high- and low-grade metamorphic rocks. The high-grade rocks were derived from volcanic island arcs, while the low-grade metamorphic rocks represent deep-sea sediments eroded from the neighboring island frogs and deposited in a forearc basin. In short, greenstone belts represent sutured protocontinents. COUNT 5
QSN1 What are Archean rocks composed of, in general? ANS1 metamorphized deep-water sediments QSN2 What type of formation is indicated by low and high grade metamorphic rocks? ANS2 Greenstone QSN3 From where did high grade Archean rocks originate? ANS3 volcanic island arcs QSN4 Low grade metamorphic rocks are composed of what, generally? ANS4 deep-sea sediments QSN5 What is a greenstone belt? ANS5 sutured protocontinents