Author Question: How are basalt and gabbro similar, and how are they different? How about andesite and diorite? ... (Read 62 times)

magmichele12 · **on:** Jul 15, 2018

How are basalt and gabbro similar, and how are they different? How about andesite and diorite?
Rhyolite and granite? How are basalt, andesite, and rhyolite the same, and how are they different?
How about gabbro, diorite, and granite? What will be an ideal response?

Question 2

What are aphanitic and phaneritic textures, and what do they say about the way the rock formed? What will be an ideal response?

itsakadoozi · **Reply #1 on:** Jul 15, 2018

Answer to Question 1

Basalt and gabbro are both felsic rocks, but basalt is aphanitic due to rapid cooling and gabbro is
phaneritic due to slower cooling. The same is true for composition but not cooling rate of andesite, the
fine-grained, and diorite, the coarse-grained, equivalents. Rhyolite is a fine-grained, rapid cooling
felsic rock, and granite is a coarse-grained, slow cooling felsic rock too. Basalt, andesite, and rhyolite
are increasingly felsic fine-grained rocks, and gabbro, diorite, and granite are increasingly felsic
coarse-grained rocks. The first set is extrusive, and the second set is intrusive

Answer to Question 2

Aphanitic rocks are so fine-grained that the individual minerals are too small to be seen with the naked
eye. They form when the rate of nuclei formation exceeds the rate of crystal growth, and an aggregate
of small mineral grains forms. Phaneritic rocks are coarse-grained; the rate of growth exceeds the rate
of nuclei formation, and large mineral grains form.