#igneous

Yes! We have chatted on occasions, I’ve been meaning to catch him up on the Igneous relationship drama but it got away from me and I haven’t gotten around to catch up.

IGNEOUS PETROLOGY: MAFIC ROCKS (45–52% SIO2)

INTRODUCTION

Igneous petrology is the scientific study of rocks formed through the solidification of magma or lava.

Within this branch of geology, mafic rocks represent an essential group because they are among the most abundant rocks on Earth and are fundamental to the formation of oceanic crust and volcanic landforms.

Mafic rocks are defined as igneous rocks with silica contents between 45% and 52%.

They are enriched in magnesium and iron (the word mafic comes from "magnesium" and "ferric") and have relatively low amounts of silica compared to intermediate and felsic rocks.

Their chemical and mineralogical properties give them distinctive textures, colors, and field occurrences.

BASIC CHARACTERISTICS OF MAFIC ROCKS

Mafic rocks are typically dark-colored (black to dark gray) due to the dominance of ferromagnesian minerals.

They are denser than felsic and intermediate rocks but less dense than ultramafic rocks.

Common minerals in mafic rocks include plagioclase feldspar (calcium-rich varieties), pyroxene, and olivine, with minor amounts of amphibole. Quartz is usually absent or very rare.

The typical silica range of 45–52% gives these rocks a balance between high-temperature and moderate-temperature mineral assemblages, making them stable in a variety of tectonic environments.

CLASSIFICATION OF MAFIC ROCKS

Mafic rocks can be grouped into two major categories based on their environment of formation:

Plutonic (intrusive) mafic rocks:

These form when magma cools slowly beneath the Earth’s surface, allowing coarse crystals to grow.

The most common example is gabbro.

Volcanic (extrusive) mafic rocks:

These form when magma erupts and cools rapidly on or near the surface.

Basalt is the most common volcanic mafic rock and is the most abundant volcanic rock on Earth.