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Glossary

bathymetry--topography of the ocean floor.

chondrule--spheroidal granule or aggregate of olivine and/or orthopyroxene that occur within stony meteorites (also known as chondrites). These spheres are about one millimeter in diameter and are believed to have formed from molten silicate droplets.

Exclusive Economic Zone (EEZ)--This zone extends 200 nautical miles from the coasts of the United States, Puerto Rico, the Northern Mariana Islands, and the U.S. territories and possessions and includes the U.S. continental shelves. It was established by President Reagan in March 1983.

induced polarization (IP)--The IP method measures resistivity and phase shift at a single frequency. Complex or spectral IP measures resistivity and phase shift over a wide range of frequencies. With the wide spectral range, the behavior of the IP effect (the complex resistivity) can be seen for distinct mineral assemblages on a graph of IP effect magnitude vs. phase. The IP method has been used on land for nearly fifty years to search for disseminated (very low-grade) sulfide ore deposits. It works by causing ions in the groundwater to migrate under a high inducing voltage onto individual mineral surfaces. When the inducing electrical field is removed or temporarily turned off, the finite bleed-off time for these charges to move back to the ground water can be measured as a phase-shift (or time-lag between the inducing transmitted voltage and the measured receiver voltage). This finite bleed-off, or time-shift, between the induced and the measured voltages is the IP effect. If an IP effect is detected in the field measurements, there are sulfide minerals or certain other minerals such as ilmenite or clays in the ground between the high-voltage transmitter and the receiver (detector) arrays.

industrial minerals--Rocks, minerals, or other naturally occurring inorganic substances of economic value that are not metallic ores, mineral fuels, or gemstones.

mesostasis--The glassy or very fine-grained portion of an igneous rock. This represents the last portion of the molten material to have solidified.

paleochannel--an ancient stream bed or channel.


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