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 ?
Shane Stafford threw an interception to cornerback Tony Lukins and Greisen found Adams with the touchdown pass.
Greisen and Borch (2001) recommend maintaining a minimum mean arterial pressure of 30 mm Hg in preterm infants between 26 and 32 weeks gestation, because this has been shown to maintain cerebral perfusion in areas more sensitive to low blood flow such as the periventricular white matter.
Foote's attorney, Darold Killmer, of the Denver-based firm of Miller Lane Killmer & Greisen, contended the shopping center owners "are simply revising history, and not successfully.
Bygma is slightly larger than us, but we found ourselves in a very similar situation," said Peter Greisen, business manager for Johannes Fog.
Thomas Head & Greisen PC John Letourneau, Pres.
Chief Doug Greisen of the Scappoose Police Department noted, "When it came time to select a digital in-car video system, we wanted to select the best product on the market for the taxpayers' money.
5 kbars during vein mineralization at the Dunbrack occurrence in the MB, which is similar to pressures suggested for greisen and vein mineralization at the East Kemptville tin deposit in the western part of the South Mountain Batholith (Halter and Williams-Jones 1999; Kontak et al.
New York Giants: OUT: TE-S Darnell Dinkins (foot); LB Nick Greisen (foot); DT Matt Mitrione (shoulder).
Season-ending injury occurred on last play of the first half in the Sun Bowl when he was hit by blitzing linebacker Nick Greisen while attempting a Hail Mary pass.
Twelve kilometres WSW of the old Penedono mine, a broad NE trending auriferous greisen system contains a number of old tungsten-mining works.
LE R Meier 92, DT J Henderson 98, M Stroud 99, RE P Spicer 95, LB D Smith 52, M Peterson 54, N Greisen 55, CB R Mathis 27, B Williams 29, SS D Darius 20, FS D Grant 37.
Gobrecht joins a prestigious leadership team including: an international Board of Directors led by Chairman Timothy Shiver, President and CEO Pasternack, and Managing Directors Mike Smith (Europe/Eurasia), Dennis Brueggemann (Latin America), Ayman Wahab (Middle East/North Africa), John Dow (Africa), Troy Greisen (Asia Pacific) and Yan-Pui Tsin (East Asia).