Experimental Petrology Lab

Museum Specialists Saebyul Choe and Keiji Hammond checking run conditions for IHPV 1 in the experimental petrology laboratory.

Many high-pressure and/or high-temperature geologic processes, such as the generation of magma in Earth’s crust, release of magmatic fluids that drive volcanic eruptions, formation of metallic mineral deposits by hot fluids, and the metamorphism of rocks by fluids cannot be observed directly because they occur in inaccessible regions of the Earth’s interior.  We apply experimental petrology to study these processes in the lab by replicating the pressures, temperatures, fluids, melts, and rock compositions involved.

In the experimental petrology laboratory, we can simulate volcanic conditions at surface pressure by conducting experiments in high-temperature furnaces that operate at atmospheric pressure.  We also conduct experiments in other equipment that can operate at higher pressures.  This lab also two Internally Heated Pressure Vessels (IHPVs) that are capable of operating up to 5000 bars (equivalent to 72520 pounds per square inch) which is the pressure magma would experience at 16 kilometers, or 10 miles depth, below Earth’s surface.  Electrical furnaces for the IHPVs can be run at temperatures up to 1150°C (2100°F) to provide the heat required.  The lab also includes three Cold Seal Pressure Vessels (CSPVs) that attain a maximum temperature of 800°C for pressures of 2000 bars (equivalent to 7 kilometers below Earth’s surface).

Experimental run products including silicate glass (the quenched silicate melt = purple phase) and experimentally crystallized grains of apatite (brightly colored crystals and finer-grained dark needles) contained within the silicate glass. Long dimension of field of view = 1 millimeter.

Experimental run product consisting of brown silicate glass (the quenched silicate melt) containing small to large spherical and elliptical gas bubbles. The glass was generated by melting and quickly cooling and quenching a Mt. Vesuvius, Italy, volcanic rock sample. Field of view diameter = 2 millimeters.

Experiments are conducted in small cylindrical precious metal capsules made of nearly pure gold, platinum, or alloys of silver-palladium or gold-palladium (depending on the experimental temperatures involved).  Rock powders - with or without added water, carbon dioxide, sulfur, chlorine or other volatile components – are loaded into the metal capsules, and the capsules are welded shut and loaded into the IHPVs or CSPVs.  The IHPVs are pressurized with argon gas and the CSPVs are pressurized with water to the pressure required and then heat is applied.  Experiments may be conducted for hours to weeks, depending on the experimental objectives.  At the conclusion of an experiment, the capsule is cooled rapidly to room temperature while pressure is held constant.  The capsule is then opened and the experimental materials inside studied with a microscope and analyzed by electron microprobe or Fourier-Transform Infrared Spectroscopy at the museum and/or by ion microprobe at the Woods Hole Oceanographic Institute or with LA-ICPMS at the Lamont-Doherty Earth Observatory.

 Ongoing research projects in this lab include:

• How do the volatiles water, carbon dioxide, sulfur dioxide, hydrogen sulfide, and chlorine dissolve in magma as a function of pressure, temperature, melt composition, and the composition of magmatic fluids present?

• How do economic deposits of ore metals including copper, molybdenum, lithium, tantalum, beryllium, and others form in igneous environments?

• How does the common phosphate mineral apatite (Ca₅[PO₄]₃[OH,F,Cl]) crystallize in magmas and how does its chemical composition provide important information on water, fluorine, and chlorine contents of magmatic melts and fluids?

• What conditions influence the nucleation, sizes, and shapes of magmatic fluid bubbles in silicate melts?