High School

Which of the following choices classifies the three listed rocks by composition and texture?

A. Diorite is intermediate with an aphanitic texture; rhyolite is felsic with a phaneritic texture; basalt porphyry is mafic with a porphyritic texture.

B. Diorite is felsic with a phaneritic texture; rhyolite is felsic with an aphanitic texture; basalt porphyry is mafic with a porphyritic texture.

C. Diorite is intermediate with a phaneritic texture; rhyolite is felsic with an aphanitic texture; basalt porphyry is felsic with an aphanitic texture.

D. Diorite is intermediate with a phaneritic texture; rhyolite is felsic with an aphanitic texture; basalt porphyry is mafic with a porphyritic texture.

E. Diorite is intermediate with a phaneritic texture; rhyolite is mafic with an aphanitic texture; basalt porphyry is felsic with a porphyritic texture.

Answer :

Final answer:

D. Diorite is intermediate with a phaneritic texture; rhyolite is felsic with an aphanitic texture; basalt porphyry is mafic with a porphyritic texture.

The correct classification of diorite, rhyolite, and basalt porphyry according to composition and texture would be: diorite as intermediate with a phaneritic texture, rhyolite as felsic with an aphanitic texture, and basalt porphyry as mafic with a porphyritic texture.

Explanation:

Classification of Rocks by Composition and Texture

The composition and texture of rocks are crucial in their classification. Let's examine the rocks listed in the question:

  • Diorite: This is an intermediate igneous rock with a phaneritic texture, meaning it has visible crystals and is characterized by a mix of light and dark minerals.
  • Rhyolite: Rhyolite is a felsic, extrusive igneous rock. It is equivalent to granite in mineral composition but has an aphanitic texture with very fine crystals, usually smaller than 1 mm, due to the quick cooling of lava.
  • Basalt porphyry: It is a mafic rock with a porphyritic texture, which means it contains larger crystals, known as phenocrysts, within a finer-grained groundmass.

Therefore, the correct answer to the classification of these rocks based on their composition and texture is:

Diorite is intermediate with a phaneritic texture; rhyolite is felsic with an aphanitic texture; basalt porphyry is mafic with a porphyritic texture.