Roedder, Edwin W. (earth scientist)

(1919- ) American Geochemist

When a mineral crystallizes, it can trap a small bubble of fluid and/or vapor that is present in the crystallization process. This completely encapsulated bubble is called a fluid inclusion. The fluid within it tells geologists the composition of the fluid that accompanied the crystallization of a pluton or the metamorphism of a rock or terrane, or the mineralization of a vein among other things. By heating or cooling the inclusion until all of the liquids and gases (and even solids) combine on a stage attached to a microscope (to observe the transformation), an experimentally determined “isochore” may be used to determine the pressure and temperature of formation. Before Edwin Roedder did his pioneering research to establish this great use of fluid inclusions, they were merely curiosities to be viewed under a microscope. They were indeed very curious. The fluid in some of the little bubbles would vibrate furiously. It was assumed that this vibrating was an example of “Brownian Motion” and the result of pent-up energy. Roedder showed that the motion was in fact the result of minute thermal gradients across the inclusions. He even patented an ingenious device to sense tiny thermal gradients based upon this observation entitled “Device for Sensing Thermal Gradients.” No combination of thermocouples or thermometers has the same delicate sensitivity, nor can they match the speed of response of his device. Edwin Roedder is the true “father of fluid inclusion research,” which is now a standard technique for petrologic and ore mineralization research among others. His papers include “Ancient Fluids in Crystals” and “Fluid Inclusions as samples of the Ore Fluids.”

Edwin Roedder had another major research direction. He was an experimental petrologist starting at the Geophysical Laboratory of the Carnegie Institution of Washington, D.C., as a graduate student. He found that by adding iron to a relatively common system, two liquids emerged that were immiscible just like oil and water, as reported in the paper “Silicate Liquid Immiscibility in Magmas.” The importance of this finding was not fully appreciated until the lunar samples were returned to Earth by the Apollo astronauts. Scientists discovered glass globules in the igneous rocks. When they determined the composition of this glass, they found that it was exactly the same as Roedder found in his experiments. This discovery caused Roedder to renew his work and ultimately to propose that liquid immiscibility is a major process in magmatic differentiation, planetary evolution, and the formation of mineral deposits. As if his fluid inclusion work was not enough of a contribution to the science, this work on immiscibility caused another great impact on the profession.

Edwin Roedder was born on July 30, 1919, in Monsey, New York, but he spent his youth in Philadelphia, Pennsylvania. He attended Lehigh

Edwin Roedder performing research on rock compositions on a phase diagram in his laboratory at the U.S. Geological Survey in 1958

Edwin Roedder performing research on rock compositions on a phase diagram in his laboratory at the U.S. Geological Survey in 1958

University, Pennsylvania, where he earned a bachelor of arts degree in geology in 1941. He worked as a research engineer at Bethlehem Steel Corporation from 1941 to 1946. Roedder conducted his graduate studies at Columbia University, New York, where he earned a master of arts degree in geology in 1947 and a Ph.D. in 1950. He joined the faculty at the University of Utah upon graduation. He then moved to the U.S. Geological Survey in 1955 as chief of the Solid State Group of the Geochemical and Petrological Branch, but he also held positions of staff geologist and geologist. He remained at the U.S. Geological Survey until his retirement in 1987, whereupon he became an associate of the department at Harvard University, Massachusetts.

Edwin Roedder has led a very productive career with authorship on numerous articles in international journals, professional volumes, and governmental reports. He also edited and wrote several books and volumes. Several of these papers are benchmark works on fluid inclusions (including the definitive book simply entitled, Fluid Inclusions) and magma immiscibility. In recognition of his research contributions to the profession of geology, he has received several honors and awards. He is a member of the National Academy of Sciences. He was awarded an honorary doctorate from Lehigh University. He also received the Exceptional Scientific Achievement Medal from NASA, the Werner Medal from the German Mineralogical Association, the Roebling Medal from the Mineralogical Society of America, the Penrose Medal from the Society of Economic Geologists and the H.C. Sorby Medal.

Roedder also performed significant service to the geological profession. He served as president (1982-1983) and vice president (1981-1982) of the Mineralogical Society of America, in addition to numerous panel and committee positions. He also served as president of the Geochemical Society in 1976-1977 as well as committee work. Roedder served on numerous panels and commit tees for the National Research Council, National Science Foundation, and several governmental advisory committees, especially with regard to nuclear waste disposal.

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