WorldWide Drilling Resource

39 WorldWide Drilling Resource ® MAY 2019 Frequently-Used Geological Terms Part 81 Glossary Adapted from the Dictionary of Geological Terms R Residual Soil - Soil formed in place by the decomposition of rocks like those around it. Resistates - Sediments composed of chemically resistant minerals, enriched in weathering residues; highly quartzose sedi- ments characteristically rich also in zircon, ilmenite, rutile, and occasionally cassiterite, monazite, and gold. Resolution - A measure of the ability of geophysical instruments, or of remote sensing systems, to define closely spaced targets. Resorption - The partial or complete refusion or solution, by and in a magma, or previously formed crystals or minerals with which the magma, owing to changes of temperature, pressure, or chemical composition, has ceased to be in equilibrium. Resources - Reserves plus all other mineral deposits which may eventually become available. Either known deposits which are not recoverable at present, or unknown deposits, that may be inferred to exist but have not yet been discovered. They rep- resent the mineral endowment, global, regional, or local, ultimately available for use. Resurgence - The point where an underground stream appears at the surface to become a surface stream. Reticulate - A vein or lode with a netlike structure. This term is also used to describe a rock texture in which crystals are partially altered to a secondary mineral, forming a network that encloses remnants of the original mineral. Reversed Polarity - A natural remanent magnetization opposite to the present am- bient geomagnetic field direction. Also used to describe a configuration of the earth’s magnetic field with the magnetic positive pole, where field lines leave the earth, located near the geographic north pole. Reworked - Said of a sediment, fossil, rock fragment, or other geologic material that has been removed or dis- placed by natural agents from its place of origin and in- corporated in recognizable form in a younger formation, such as a reworked tuff, carried by flowing water and re- deposited in another location. Rg Wave - A slow, short-period Rayleigh wave which only travels along a nonoceanic path. The “g” refers to the granitic layer. Look for more terms next month! This gold vein stockwork is an example of reticulate. Photo by James St. John. C&G