Skip to main content

Agents of metamorphism

Short answer

The main agents are heat (provides energy for recrystallization), pressure (confining pressure densifies rocks, directed stress causes foliation), and chemically active fluids (speed up reactions and enable metasomatism). Time allows well‑formed minerals.

Enumerate the various agents (factors) of metamorphism and explain their role.

Metamorphism is the change in mineral composition, texture and structure of a rock in the solid state, due to changes in temperature, pressure and chemical environment.

Agents (factors) of metamorphism

1. Heat (temperature)

  • Source: magma intrusion, deep burial (geothermal gradient), friction on faults.
  • Role: provides energy for chemical reactions, causing recrystallisation and growth of new minerals (e.g. limestone to marble, shale to hornfels). Range roughly 200-800 °C.

2. Pressure

  • Confining (lithostatic) pressure: from the weight of overlying rocks; acts equally in all directions, makes rocks denser and forms minerals with compact structure.
  • Directed (differential) stress: from plate movements; flattens and aligns minerals, giving foliation, slaty cleavage and schistosity.

3. Chemically active fluids

  • Water and gases (CO₂, H₂O, fluorine) carry ions to and from the rock.
  • Role: speed up reactions and introduce new materials (metasomatism).

Time also matters: slow, long action gives well-formed minerals.

✓ Answer checked by Claude Opus 5.5 (high effort)

Related questions

All Engineering Geology I chapter 4 questions →