Science-advisor
REGISTER info/FAQ
Login
username
password
     
forgot password?
register here
 
Research articles
  search articles
  reviews guidelines
  reviews
  articles index
My Pages
my alerts
  my messages
  my reviews
  my favorites
 
 
Stat
Members: 3643
Articles: 2'487'895
Articles rated: 2609

28 March 2024
 
  » pubmed » pmid17769134

 Article overview


Geological Aspects of High-Pressure Research: High-pressure experimentation is providing a new look at problems in geophysics and petrology
F R Boyd ;
Date 3 Jul 1964
Journal Science, 145 (3627), 13-20
AbstractThe low-density minerals that make up the bulk of rocks in the earth’s crust, such as quartz and the feldspars, are transformed by high pressure into much denser phases. In some cases the products of these transitions are new phases that were first discovered in the laboratory; in other cases they are minerals such as kyanite, jadeite, and pyrope, which have long been known as constituents of metamorphic rocks. Determinations of the stability fields of these high-pressure minerals show that either metamorphism of sedimentary rocks takes place at much greater depth than has hitherto been supposed or pressures generated by orogenic forces may have significantly augmented the hydrostatic pressure. The second alternative seems unlikely, but lack of information on the strength of rocks during metamorphism makes the matter uncertain. Geophysical and petrological observations indicate that the dominant rock type in the upper mantle is garnet peridotite. However, there is reason to believe that the mantle is inhomogeneous and that a variety of rocks ranging in bulk composition from eclogite to peridotite are present. Hydrous phases, such as amphiboles, are possible constituents in the upper 100 kilometers. The hypothesis that the Mohorovicić discontinuity is a dynamic equilibrium between basalt and eclogite seems improbable. The transition zone between the upper and lower mantle can be explained as a series of reactions in which silicates with the silicon ion in fourfold coordination are transformed into phases in which silicon is in six-fold coordination. This interpretation is supported by synthesis of stishovite, a polymorph of SiO(2) with rutile structure, and by syntheses of germanate pyroxenes with ilmenite structure. Data on the melting of silicates at pressures up to 50 kilobars show that the initial dT/dP slopes of silicate melting curves are much steeper than those of metals but that they show considerable curvature. The increase of melting temperature with pressure should be much more pronounced near the top of the mantle than at greater depth.
Source PubMed, pmid17769134 doi: 10.1126/science.145.3627.13
Services Forum | Review | Favorites   
 
Visitor rating: did you like this article? no 1   2   3   4   5   yes

No review found.
 Did you like this article?

This article or document is ...
important:
of broad interest:
readable:
new:
correct:
Global appreciation:

  Note: answers to reviews or questions about the article must be posted in the forum section.
Authors are not allowed to review their own article. They can use the forum section.

browser claudebot






ScienXe.org
» my Online CV
» Free


News, job offers and information for researchers and scientists:
home  |  contact  |  terms of use  |  sitemap
Copyright © 2005-2024 - Scimetrica