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In geology, a vein is a finite volume within a rock, having a distinct shape, filled with crystals of one or more minerals, which were precipitated from an (aqueous) fluid. Veins are formed by fluids carrying mineral constituents into a rock mass as a consequence of some form of hydraulic flow within the rock. Usually this is the result of hydrothermal circulation. This article includes a list of works cited but its sources remain unclear because it lacks in-text citations. ...
For other uses, see Rock (disambiguation). ...
For other uses, see Crystal (disambiguation). ...
A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure and specific physical properties. ...
Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ...
A fluid is defined as a substance that continually deforms (flows) under an applied shear stress regardless of the magnitude of the applied stress. ...
Fluid dynamics is the sub-discipline of fluid mechanics dealing with fluids (liquids and gases) in motion. ...
Hydrothermal circulation in the oceans is the passage of the water through mid-ocean Ridge (MOR) systems. ...
Veins are classically thought of as being the result of growth of crystals on the walls of planar fractures in rocks, with the crystal growth occurring normal to the walls of the cavity, and the crystal protruding into open space. Two intersecting planes in three-dimensional space In mathematics, a plane is a two-dimensional manifold or surface that is perfectly flat. ...
For fractures in geologic formations, see Rock fracture. ...
Fig. ...
This certainly is the method for the formation of some veins. However, it is rare in geology for significant open space to remain open in large volumes of rock, especially several kilometres below the surface. Thus, there are two main mechanisms considered likely for the formation of veins: open-space filling and crack-seal growth. This article includes a list of works cited but its sources remain unclear because it lacks in-text citations. ...
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Open space filling
Open space filling is the hallmark of epithermal vein systems, such as a stockwork, in greisens or in certain skarn environments. For open space filling to take effect, the confining pressure is generally considered to be below 0.5 GPa, or less than 3-5 kilometres. Veins formed in this way may exhibit a colloform, agate-like habit, of sequential selvedges of minerals which radiate out from nucleation points on the vein walls and appear to fill up the available open space. Often evidence of fluid boiling is present. Vugs, cavities and geodes are all examples of open-space filling phenomenon in hydrothermal systems. A stockwork is a complex system of randomly oriented veins. ...
Greisen is a highly altered granitic rock or pegmatite. ...
Skarn is a fine grained metamorphic rock that is usually variably colored green or red, occasionally grey, black, brown or white. ...
The use of water pressure - the Captain Cook Memorial Jet in Lake Burley Griffin, Canberra. ...
The pascal (symbol: Pa) is the SI derived unit of pressure or stress (also: Youngs modulus and tensile strength). ...
Agate is a type of quartz (silica), chiefly chalcedony, characterised by its fineness of grain and brightness of color. ...
The Selvage of a piece of curtain fabric. ...
Bubbles in a soft drink each nucleate independently, responding to a decrease in pressure. ...
In the lower left, a spherule, or sphere-shaped grain, can be seen penetrating the interior of a small cavity called a vug. ...
Geode, halved and polished Geode, halved and polished Geodes (Greek geoides, earthlike) are geological rock formations which occur in sedimentary and certain volcanic rocks. ...
Hydrothermal circulation in the oceans is the passage of the water through mid-ocean Ridge (MOR) systems. ...
Alternatively, hydraulic fracturing may create a breccia which is filled with vein material. Such breccia vein systems may be quite extensive, and can form the shape of tabular dipping sheets, diatremes or laterally extensive mantles controlled by boundaries such as thrust faults, competent sedimentary layers, or cap rocks. Hydraulic fracturing is a method used to increase or restore the permeability of rock formations by creating fractures from fluid pressure. ...
Breccia, derived from the Latin word for broken, is a sedimentary rock composed of angular fragments in a matrix that may be of a similar or a different material. ...
Strike and dip refer to the orientation or attitude of a geologic feature. ...
A Diatreme is a volcanic pipe or feature formed by a gas or volatile rich explosive magma. ...
A thrust fault is a particular type of fault, or break in the fabric of the Earths crust with resulting movement of each side against the other, in which a lower stratigraphic position is pushed up and over another. ...
This article or section cites very few or no references or sources. ...
For other uses, see strata (novel) and strata title. ...
Crack-seal veins When the confining pressure is too great, or when brittle-ductile rheological conditions predominate, vein formation occurs via crack-seal mechanisms. A material is brittle if it is subject to fracture when subjected to stress i. ...
Ductility is the physical property of being capable of sustaining large plastic deformations without fracture (in metals, such as being drawn into a wire). ...
In geology, a rheid is a solid material that deforms by viscous flow. ...
Crack-seal veins are thought to form quite quickly during deformation by precipitation of minerals within incipient fractures. This happens swiftly by geologic standards, because pressures and deformation mean that large open spaces cannot be maintained; generally the space is in the order of millimetres or micrometres. Veins grow in thickness by reopening of the vein fracture and progressive deposition of minerals on the growth surface. In engineering mechanics, deformation is a change in shape due to an applied force. ...
This article is about pressure in the physical sciences. ...
A millimetre (American spelling: millimeter, symbol mm) is an SI unit of length that is equal to one thousandth of a metre. ...
A micrometre (American spelling: micrometer, symbol µm) is an SI unit of length equal to one millionth of a metre, or about a tenth of the diameter of a droplet of mist or fog. ...
Deposition is a word used in many fields to describe different processes: In law, deposition is the taking of testimony outside of court. ...
Tectonic implications Veins generally need either hydraulic pressure in excess of hydrostatic pressure (to form hydraulic fractures or hydrofracture breccias) or they need open spaces or fractures, which requires a plane of extension within the rock mass. Hydrostatic pressure is the pressure exerted by a fluid due to its weight. ...
In metaphysics, extension is the property of taking up space; see Extension (metaphysics). ...
In all cases except brecciation, therefore, a vein measures the plane of extension within the rock mass, give or take a sizeable bit of error. Measurement of enough veins will statistically form a plane of principal extension.
In ductilely deforming compressional regimes, this can in turn give information on the stresses active at the time of vein formation. In extensionally deforming regimes, the veins occur roughly normal to the axis of extension. Bold text Wiktionary has related dictionary definitions, such as: compressor, compression inthe wkjhrlfidhb;g/df == Compressor may refer to: Gas compressor, a mechanical device that compresses a gas e. ...
Stress is a measure of force per unit area within a body. ...
A coordinate axis is one of a set of vectors that defines a coordinate system. ...
Mineralisation and veining Veins are of prime importance to mineral deposits, because they are the source of mineralisation either in or proximal to the veins. Typical examples include gold lodes, as well as skarn mineralisation. Hydrofracture breccias are classic targets for ore exploration as there is plenty of fluid flow and open space to deposit ore minerals. Image File history File links Metadata Size of this preview: 450 × 600 pixelsFull resolution (852 × 1136 pixel, file size: 144 KB, MIME type: image/jpeg) Roland Gotthard, own photograph 2004, copyright Roland Gotthard, free use with citation. ...
Image File history File links Metadata Size of this preview: 450 × 600 pixelsFull resolution (852 × 1136 pixel, file size: 144 KB, MIME type: image/jpeg) Roland Gotthard, own photograph 2004, copyright Roland Gotthard, free use with citation. ...
Boudinaged jasperoid in sheared basalt, Fortnum Gold Mine, Australia. ...
Quartz (from German Quarz[1]) is the second most common mineral in the Earths continental crust. ...
A sinistral is a horizontal movement of blocks either side of a geological fault. ...
Figure 1. ...
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GOLD refers to one of the following: GOLD (IEEE) is an IEEE program designed to garner more student members at the university level (Graduates of the Last Decade). ...
In geology a lode is the metalliferous ore that fills a fissure in a rock or a vein of ore deposited between layers of rock. ...
Skarn is a fine grained metamorphic rock that is usually variably colored green or red, occasionally grey, black, brown or white. ...
Iron ore (Banded iron formation) Manganese ore Lead ore Gold ore An ore is a volume of rock containing components or minerals in a mode of occurrence which renders it valuable for mining. ...
Ores related to hydrothermal mineralisation which are associated with vein material may be composed of vein material and/or the rock in which the vein is hosted.
Gold-bearing veins In many of the gold mines exploited during the gold rushes of the 19th century, vein material alone was typically sought as ore material. In most modern mines, ore material is primarily composed of the veins and some component of the wall rocks which surrounds the veins. For other meanings, see Gold rush (disambiguation) A California Gold Rush handbill A gold rush is a period of feverish migration of workers into the area of a dramatic discovery of commercial quantities of gold. ...
The difference between 19th century and modern mining techniques and the type of ore sought is based on the grade of material being mined and the methods of mining which are used. Historically, hand-mining of gold ores permitted the miners to pick out the lode quartz or reef quartz, allowing the highest-grade portions of the lodes to be worked, without dilution from the unmineralised wall rocks.
Modern mining using larger machinery and equipment forces the miners to take low-grade waste rock in with the ore material, resulting in dilution of the grade.
However, modern mining and assaying allows the delineation of lower-grade bulk tonnage mineralisation, within which the gold is invisible to the naked eye. In these cases, veining is the subordinate host to mineralisation and may only be an indicator of the presence of metasomatism of the wall-rocks which contains the low-grade mineralisation. In music alteration, an example of chromaticism, is the use of a neighboring pitch in the chromatic scale in place of its diatonic neighbor such as in an altered chord. ...
For this reason, veins within hydrothermal gold deposits are no longer the exclusive target of mining, and in some cases gold mineralization is restricted entirely to the altered wall rocks within which entirely barren quartz veins are hosted.
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