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Experimental Petrology Lab

The Department’s experimental petrology lab is directed by Dr. James Watkins and is very well-equipped for experimental studies at pressures to about 35 kbar (3.5 GPa, ~500,000 psi, equivalent to about 100 km depth in the Earth), temperatures to ~1500°C, and in some circumstances, with controlled oxygen fugacity.

 

The lab houses

Two endloaded, 1/2” solid medium piston cylinder apparatii. The larger has a nested ram design with stacked hydraulic cylinders producing up to 300 tons of endload force and 100 tons of master ram force. The smaller press has opposed hydraulic rams, each with a 50 ton capacity. Experimental temperatures are generated resistively with straight walled graphite heater tubes, usually within CaF2 based pressure cells. Temperature is measured and controlled with W5Re/W25Re thermocouples and Eurotherm 808 p.i.d. controllers. Quench rates of ~250°/second are possible with this equipment.

 

Two Deltec VT-31 one atmosphere gas-mixing vertical quench furnaces. These furnaces operates at ambient pressure and allow control of experimental temperature and oxygen fugacity. The furnaces have internal bores of 1.25” and 1.50”. Experimental oxygen fugacities (fO2) are controlled with CO2/H2 mixtures and are measured with ZrO2-based solid electrolyte fO2 sensors using platinum electrodes and breathable grade air as a reference gas. Temperatures are measured with Pt/Pt10Rh thermocouples.

Deltec furnaces, to the left and right, are capable of temperatures to about 1500°C, achieved with MoSi2 elements. Oxygen fugacity is varied and controlled by mixing CO2 and H2 through the mixing panel in the center. Eurotherm 808 controllers (beneath furnaces) control temperature and the emf of the oxygen sensors is monitored using the multimeter on the shelf in the center.

Two rapid-quench cold-seal apparatii with computer-controlled pressure and temperature cycling. These devices were installed in 2007 and combine commercially available- and UO shop-built components to provide a capability not provided by either of the other types of equipment. In particular, this equipment operates at pressures to 2 kbar, greater than possible in the gas-mixing furnaces, and lower than possible in the piston-cylinders. Samples are contained in hot bombs of Rene 41 Ni/Co-based superalloy, coupled to cold bombs of stainless steel, by a coupling nut through which cooling water flows, enabling the rapid quench. Temperature is generated by external furnaces controlled with chromel/alumel thermocouples. The strength limitations of the Rene 41 material limit these devices to 2 kbar and about 900°C, so they are used primarily in studies of subvolcanic, volcanic conduit, and hydrothermal processes. Automation of P and T cycling is accomplished with PCs running LabView software.

Ancillary equipment. The lab also contains all necessary sample preparation and support equipment including a UO shop-built carbon arc microwelder, microbalance, lathe, drill press, diamond wafering saw, drying furnaces, bench hydraulic press, etc.