Greisen


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greisen

[′grīz·ən]
(petrology)
A pneumatolytically altered granite consisting of mainly quartz and a light-green mica.

Greisen

 

a rock of metasomatic origin, composed basically of quartz and light-colored micas—lepidolite and muscovite. It not infrequently contains an impregnation of valuable ore minerals (such as cassiterite. wolframite, and tantalite) in industrial quantities. In such cases they are regarded as ore bodies. Deposits usually occur in the form of irregularly shaped sections in granite masses, mainly in their outer sections and sometimes in the rocks surrounding the granite Greisen is formed as a result of the greisening of rocks, often along the periphery of ore veins, and serves as an indication for prospecting.

References in periodicals archive ?
Petrographic observations suggest that greisenized granites of the Hub stock originated at the same time as the greisen bodies.
Cabe senalar en este documento tecnico, que para la determinacion de concentraciones economicas de Ta-Nb-Sn-Ti, REES (Ce, La, Y, Nd) y asociaciones de PB-Th, se debe emplear al gu nos metodos/tecnicas tales como imagen satelital hyperespectral ASTER, para la discriminacion litologica, mapeo de estructuras geologicas y la identificacion de areas de alteracion hidrotermal y greisen, geofisicas (magnetismo, por presencia del hierro asociado), espectrometria de radiacion gamma, que diferencie presencia de radon-torio, K40, para aquellos casos asociados a radiactividad leve, y en general, refraccion sismica/equipo portatil, para medir espesores de los aluviones con potencial de coltan y otros minerales asociados.
Pough (1964) has described the typical habits associated with each of these genetic models, lumping the pegmatitic and greisen modes of formation together because crystals from them show no difference in habit.
Take 'Mandatory' Out of Arbitration Agreements, by Paula Greisen and Alison Butler Daniels [Aug.
1992; Greisen, Munck, & Lou, 1987; Okumura et al.
Rhein's back-up quarter-back Chris Greisen then fumbled in his own endzone when the ball slipped out of his hand in the torrential rain, and a defensive tackle by DeVonte Peterson made him pay as he flopped on the ball to score a touchdown.
Rhein's back-up quarterback Chris Greisen fumbled in his own endzone in the torrential rain and tackle DeVonte Peterson flopped on the ball for a touchdown.
But the Germans responded quickly with receiver Charlie Adams hauling in an 11- yard pass from quarterback Chris Greisen in the endzone and Anderbrugge's point after kick took it to 14-3.
In 1965 Kenneth Greisen (Cornell University) and Georgi Zatsepin and Vadem Kuzmin (Russian Academy of Sciences) independently realized that cosmic-ray protons with energies above 5 x [10.
New York Giants: QUESTIONABLE: C Chris Bober (biceps); WR Ron Dixon (knee); LB Nick Greisen (foot); DT Cornelius Griffin (ankle); LB Quincy Monk (ankle).
Then a company is stuck justifying it," said Lane, who is with the Denver firm of Miller, Lane, Killmer & Greisen.