Mafic Rock Definition

Mafic rocks are igneous rocks characterized by their high content of magnesium (Mg) and iron (Fe), often referred to as 'mafic'. Due to these minerals, they typically have a dark color.

Volcanic Rock Classification

Volcanic rocks, also known as extrusive igneous rocks, form when molten lava cools quickly on the Earth's surface. Their classification depends on mineral and chemical composition:

• Felsic rocks (like Rhyolite) are rich in silica and feldspar, appearing light-colored.
• Intermediate rocks (like Dacite) have compositions between felsic and mafic types.
• Mafic rocks (like Basalt) are lower in silica and higher in iron and magnesium, appearing dark-colored.

Analyzing Options

Evaluating the given options based on their composition:

• Dacite is an intermediate volcanic rock.
• Trachyte is a felsic (alkaline) volcanic rock.
• Rhyolite is a felsic volcanic rock.
• Basalt is a mafic volcanic rock, defined by its low silica content and abundance of mafic minerals.

Conclusion: Mafic Rock Identified

Among the choices provided, Basalt is the mafic volcanic rock. Its mineral composition aligns with the definition of mafic rocks, distinguishing it from the felsic and intermediate rocks listed.