Geology of Ascension Island other volcanic islands, which only have a few mafic and felsic endmembers such as basalt or rhyolite, Ascension has a full-range from some of the most mafic to most felsic. This includes basalt, hawaiite, mugearite, benmoreite,trachyte and rhyolite. Potassium-argon dating indicates that the oldest rocks exposed above the water are one million year old rhyolites. Geologists have divided the island's mafic and felsic rocks into different named sequences and sub-divided mafic rocks based on their ratio of zirconium and niobium. The Sister's Peak region in northwest Ascension has intermediate mafic lava flows, scoria cones and mafic ash fall deposits near
North China Craton Eastern Block is made up of early to late Archean (3.8-3.0 billion years ago) tonalite-trondhjemite-granodiorite gneisses, granitic gneisses, some ultramafic to felsic volcanic rocks and metasediments with some granitoids which formed in some tectonic events 2.5 billion years ago. These are overlain by Paleoproterozoic rocks which were formed in rift basins. The Western Block consists of an Archean (2.6-2.5 billion years ago) basement which comprises tonalite-trondhjemite-granodiorite, mafic igneous rock, and metamorphosed sedimentary rocks. The Archean basement is overlain unconformably by Paleoproterozoic khondalite belts, which consist of different types of metamorphic rocks, such as graphite-bearing sillimanite garnet gneiss. Sediments were widely