Question

Rearrange the following minerals in order of increasing metamorphic grade: biotite, garnet, sillimanite, chlorite.

Short answer

Chlorite, biotite, garnet, sillimanite.

Step-by-step solution

Identify the Minerals

List out the given minerals: biotite, garnet, sillimanite, chlorite.

Understand Metamorphic Grade

Metamorphic grade refers to the degree of metamorphism that a rock has undergone. It is generally determined by temperature and pressure conditions during metamorphism.

Research Metamorphic Grades of the Minerals

Find out the typical metamorphic grades for each mineral: - Chlorite: Low-grade - Biotite: Low to Medium-grade - Garnet: Medium to High-grade - Sillimanite: High-grade

Order the Minerals by Metamorphic Grade

Rearrange the minerals in order of increasing metamorphic grade based on the information gathered: chlorite, biotite, garnet, sillimanite.

Key concepts

metamorphic minerals

Metamorphic minerals form under specific conditions of temperature and pressure. Different minerals are stable under different conditions, which helps geologists determine the metamorphic grade of rocks.
For instance, some common metamorphic minerals include:

• Chlorite: Forms under low-grade metamorphic conditions, typically at lower temperatures and pressures.
• Biotite: Appears under low to medium-grade metamorphic conditions.
• Garnet: Known for forming in a wide range of grades, usually from medium to high.
• Sillimanite: Stable under high-grade metamorphic conditions, where temperatures and pressures are at their peak.

By identifying these minerals in a rock sample, one can infer the metamorphic conditions the rock has experienced.

metamorphism

Metamorphism is the process of changing the mineral composition and texture of a rock by exposing it to different conditions of temperature and pressure. This transformative process does not melt the rock but rearranges the minerals into new structures.
There are different types of metamorphism, including:

• Contact Metamorphism: Occurs when rocks are heated by nearby molten magma, usually involving low pressure but high temperature.
• Regional Metamorphism: Takes place over large areas due to deep burial and tectonic pressures, involving high pressure and variable temperatures.
• Hydrothermal Metamorphism: Happens when hot, chemically active fluids interact with the rock, commonly found near hydrothermal vents.

temperature and pressure conditions

Temperature and pressure are crucial factors in determining the type and grade of metamorphism a rock undergoes. Different minerals are stable only under specific conditions, so knowing these conditions helps in identifying metamorphic grades.

• Low-grade Metamorphism: Characterized by lower temperatures (around 200-320°C) and lower pressures. Minerals like chlorite and muscovite form under these conditions.
• Medium-grade Metamorphism: Occurs at moderate temperatures (around 320-450°C) and pressures. Minerals such as biotite and garnet are typical in these settings.
• High-grade Metamorphism: Involves very high temperatures (above 450°C) and pressures. Minerals like sillimanite, kyanite, and staurolite are stable in these high-grade environments.

These temperature and pressure conditions not only influence the minerals that form but also their size, texture, and other physical properties.