Constraints on graphite crystallinity in some Spanish fluid-deposited occurrences from different geologic settings |
| |
Authors: | F J Luque M Rodas |
| |
Institution: | (1) Departamento de Cristalografía y Mineralogía, Facultad de Ciencias Geológicas, Universidad Complutense de Madrid, 28040 Madrid, Spain, ES |
| |
Abstract: | Epigenetic, vein-type graphite mineralization originates by deposition from C—O—H fluids in high-temperature environments.
Consequently, fluid-deposited graphite is uniformly highly crystalline in volumetrically large occurrences. This work examines
the factors controlling graphite crystallinity in fluid-deposited occurrences with reference to some case studies from southern
Spain where vein-type graphite is associated with a variety of host rocks. Possible causes influencing high crystallinity
of graphite in these occurrences include: (1) large graphite occurrences are generated from large volumes of fluids that maintain
their temperatures for long periods of time, which is easier at higher temperatures; (2) high temperature conditions are required
for a fluid to precipitate a major part of its dissolved carbon during a small temperature decrease; (3) carbon is incorporated
into C—O—H fluids mainly through devolatilization reactions which also require high temperatures; (4) highly crystalline graphite
generated at high-T/high-P conditions is less susceptible to resorption as P decreases or by subsequent fluid flow; (5) graphite precipitation involves high activation energy that can be overcome only
if the temperature is high enough. These causes can be extrapolated to most vein-type graphite deposits worldwide.
Received: 23 February 1998 / Accepted: 28 April 1998 |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|