See:zone axis
A term used esp. in miscroscopic work to describe those minerals whose
cross sections show their successive concentric layers of growth.
Fay
A theory of hypogene mineral-deposit formation, and the spatial
distribution patterns of mineral sequences to be expected from change in a
mineral-bearing fluid as it migrates away from a magmatic source. It also
deals with thermal-chemical gradients associated with the genesis of ore
deposits, whether of direct magmatic origin or not, and with metallogenic
zoning on a regional scale. AGI
a. A belt, band, or strip of earth materials, however disposed;
characterized as distinct from surrounding parts by some particular
property or content; e.g., zone of saturation, fault zone, or a zone of
secondary enrichment. CF:belt
b. See:aureole
c. A minor interval in any category of stratigraphic classification. There
are many kinds of zones, depending on the characteristics under
consideration--biozones, lithozones, chronozones, mineralized zones,
metamorphic zones, zones of reversed magnetic polarity, etc. The term
should always be preceded by a modifier indicating the kind of zone to
which reference is made. AGI
d. A metal zone is equivalent to a mineral zone, yet the terms mineral and
metal are not synonymous. Ricketts
e. The ground or mass bounded by horizontal or inclined planes or curved
surfaces in which given chemical or physical conditions exist, such as
zone of saturation or zone of weathering. Nelson
f. A group of beds characterized by the presence of one or more specific
fossils; e.g., zonal fossil or fossils. BS, 11
g. Geologically, a distinctively mineralized area, region, or level. In a
specific lode or other deposit, the progressive change from upper to lower
horizons. At the top is outcrop or gossan, oxidized or weathered. Next is
the leached zone, impoverished by dissolution of its values (or part of
them), which may be redeposited below in the zone of secondary enrichment.
Below this is the primary, or unaltered zone, which consists of the
original sulfide formation. Pryor, 3
h. An area or region more or less clearly set off or characterized as
distinct from surrounding or adjoining parts; e.g., the mineral zone in a
metalliferous region. Webster 2nd
i. A series of faces of a crystal whose intersection lines with each other
are all parallel. Webster 3rd
j. See:zones
That crystallographic direction through the center of a crystal which is
parallel to the intersection edges of the crystal faces defining the
"crystal zone." Syn:crystal axis; zonal axis.
Highly localized melting, usually by induction heating, of a small volume
of an otherwise solid piece. By moving the induction coil along the rod,
the melted zone can be transferred from one end to the other. In a binary
mixture where there is a large difference in composition on the liquidus
and solidus lines, high purity can be attained by concentrating one of the
constituents in the liquid as it moves along a rod. ASM, 1
See:B-horizon
A subsurface zone containing water under pressure less than that of the
atmosphere, including water held by capillarity, and containing air or
gases generally under atmospheric pressure. This zone is limited above by
the land surface and below by the water table. It contains vadose water.
CF:zone of capillarity
A subsurface zone that overlies the zone of saturation in which capillary
voids hold water above the zone of saturation by molecular attraction
acting against gravity. CF:zone of aeration
The layer of the Earth's crust below the zone of weathering in which
percolating waters cement unconsolidated deposits by the deposition of
dissolved minerals from above. AGI
A term suggested for that part of the zone of saturation having a means of
horizontal escape. AGI
See:zone of secondary enrichment
All faces, belonging to one or more forms, the normals to which lie in one
plane (the zone plane) and whose edges of intersection are parallel to the
zone axis. See also:zone axis
a. The outer, rigid part of a glacier, in which the ice is much fractured.
AGI
b. The upper, brittle part of the Earth's crust in which deformation is by
fracture rather than by plastic flow; that region of the crust in which
fissures can exist. CF:zone of plastic flow
Syn:zone of rock fracture
See:B-horizon
The zone of rock surrounding an excavation, in which the additional
stresses caused by the excavation are above a certain arbitrary value, is
termed the zone of influence. Spalding
See:asthenosphere
See:oxidized zone
That part of the Earth's crust that is under sufficient pressure to
prevent fracturing, i.e., is ductile, so that deformation is by flow.
CF:zone of fracture
AGI