A category in the hierarchy of plant and animal classification
intermediate in rank between family and species. Adj: generic. Plural:
genera. AGI
Prefix from the Greek "ge," meaning land, of the land, or Earth.
Pryor, 3
Some plants develop peculiar diagnostic symptoms that can be interpreted
directly in terms of probable excesses of a particular element in the
soil. Geobotanical indicators are either plant species or characteristic
variations in the growth habits of plant species that are restricted in
their distribution to rocks or soils of definite physical or chemical
properties. They have been used in locating and mapping ground water,
saline deposits, hydrocarbons, and rock types, as well as ores.
Hawkes, 2
a. The visual study of plants, their morphology, and their distribution as
indicators of such things as soil composition and depth, bedrock
lithology, the possibility of orebodies, and climatic and ground-water
conditions. CF:biogeochemical prospecting
See also:botanical anomaly
b. Prospecting in which visual observation of plants is used as a guide to
finding buried ore. Whereas biogeochemical methods require chemical
analysis of plant organs, the geobotanical methods depend on direct
observations of plant morphology and the distribution of plant species.
Hawkes, 2
The study of plants as related specif. to their geologic environment.
Hawkes, 2
See:geocerite
A white, flaky, waxlike resin of approximate composition C27 H (sub
53) O2 in brown coal. Also spelled geocerain, geocerin.
CF:geomyricite
A concentration of one or more elements in rock, soil, sediment,
vegetation, or water that is markedly higher or lower than background. The
term may also be applied to hydrocarbon concentrations in soils.
See also:significant anomaly
The phenomenon of the intimate occurring together of certain chemical
elements in nature because of their similar chemical properties, as, for
example, the group of the lanthanides, zirconium-hafnium,
niobium-tantalum, etc. Schieferdecker
The sequence of stages in the migration of elements during geologic
changes. Rankama and Sahama distinguish a major or endogenous cycle,
proceeding from magma to igneous rocks to sediments to sedimentary rocks
to metamorphic rocks and possibly through migmatites back to magma, and a
minor or exogenic cycle proceeding from sediments to sedimentary rocks to
weathered material and back to sediments again. AGI
Pressure, temperature, and the availability of the most abundant chemical
components are the parameters of the geochemical environment that
determine which mineral phases are stable. On the basis of these
variables, it is possible to classify all the natural geochemical
environments of the Earth into two major groups--primary and secondary.
The primary environment extends downward from the lower levels of
circulating meteoric water to the deepest level of the crust and may
extend into the mantle. It is an environment of high temperature and
pressure, restricted circulation of fluids, and relatively low free-oxygen
content. The secondary environment is the environment of weathering,
erosion, and sedimentation at the surface of the Earth. It is
characterized by low temperatures, nearly constant low pressure, free
movement of solutions, and abundant free oxygen, water, and carbon
dioxide.
The search for economic mineral deposits or petroleum by detection of
abnormal concentrations of elements or hydrocarbons in surficial materials
or organisms, usually accomplished by instrumental, spot-test, or quickie
techniques that may be applied in the field.
Syn:geochemical prospecting
The pattern, in any given area, in which the net effect of all the dynamic
forces concerned in the movement of earth materials will be reflected in
the overall pattern of distribution of the elements. Hawkes, 2
The systematic collection and processing of a very large number of samples
accompanied by the proper presentation and interpretation of the resulting
analytical data, usually with reference to a topographic map or other
geographic coordinate system. Hawkes, 2
A little-used term for the variation in metal values in varied geographic
settings. Geochemical contrast.
A survey involving the chemical analysis of systematically collected
samples of rock, soil, stream sediments, plants, or water; this expression
may be further modified by indicating specif. the material sampled, as,
for example, geochemical soil survey. Hawkes, 1
An individual who studies the chemistry of earth materials. May be
qualified by the term "inorganic" for the study of nonbiological
materials, "organic" for the study of plants and hydrocarbons, and
"isotope" for the study of nuclides of the elements. Generally, the
geochemist is concerned with the distribution of elements in exploration
application or with the cycles of elements in basic science.
The study of the relative and absolute abundances of the elements and
their nuclides (isotopes) in the Earth; the distribution and migration of
the individual elements or suites of elements in the various parts of the
Earth (the atmosphere, hydrosphere, lithosphere, etc.), and in minerals
and rocks, and also the study of principles governing this distribution
and migration. Geochemistry may be defined very broadly to include all
parts of geology that involve chemical changes, or it may be focused more
narrowly on the distribution of the elements, as in Mason's definition;
the latter is commonly understood if the term is used without
qualification. AGI
See:geochronologic
A monoclinic mineral, Pb14 (Sb,As)6 S23 ; forms a
series with jordanite; soft; sp gr, 6.4 to 6.5; associated with galena,
jamesonite, and boulangerite; in lead ores in Bolivia, Germany, Sweden,
and the United States. Syn:kilbrickenite