Experimental Petrology Lab

Many geologic processes, such as the development of magmatic bodies, the formation of mineral deposits, or the metamorphism of rocks, cannot be observed directly because they occur in inaccessible regions of the earth. Experimental petrologists study these processes by replicating high temperature and pressure conditions in the laboratory.

Jim Webster makes adjustments to the furnace temperature settings on the IHPV.

Jim Webster makes adjustments to the furnace temperature settings on the IHPV.

In our lab, we can simulate volcanic conditions with several furnaces that operate at atmospheric pressure. Also, with our three cold-seal hydrothermal pressure vessels and a single internally heated pressure vessel (IHPV) we generate the conditions under which many magmatic and metamorphic reactions occur in the crust. Cold-seal vessels attain a maximum temperature of 800 degrees C at a pressure roughly equivalent to that 7 kilometers below the Earth's surface. The IHPV is capable of operating at temperatures up to 1200 degrees C (2200 F) and pressures as great as that found at 22 km (15 miles) depth within the earth (i.e. 6.5 kilobars or roughly 95,000 psi).

To set up an experiment, we put either a natural rock powder or a powdered mixture of chemicals into centimeter-long metal capsules. We add water to the capsule as well since we wish to understand the interactions between rocks and fluids within earth's crust. The capsules, which are made out of gold, platinum, silver palladium or some other precious metal alloy, are welded shut to prevent the contents from leaking. The capsules are placed within the pressure vessel that is then pressurized and heated.

At the end of the experiment, which generally takes several days, the textures and chemical composition of the capsule contents are observed. Chemical analyses are performed with the aid of a variety of instruments: the electron microprobe, the ion microprobe or SIMS at Woods Hole, the FTIR, and the SEM. Ongoing research projects in this lab include:

  • How much chlorine and water dissolves in magmas?
  • The chemistry of magmas trapped in crystals
  • The nature of tin deposits