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SUMMARY:Melt generation and extraction from the Mantle - Dan McKenzie (Uni
 versity of Cambridge)
DTSTART:20160215T100000Z
DTEND:20160215T110000Z
UID:TALK64704@talks.cam.ac.uk
CONTACT:INI IT
DESCRIPTION:In 1964 Paul Gast discovered that basalts from oceanic islands
  had quite different radiogenic isotope ratios from those of basalts from 
 spreading ridges\, and that these differences required their two source re
 gions to have been separate for <span><span><img alt="" src="http://www-ol
 d.newton.ac.uk/js/MathJax/current/fonts/HTML-CSS/TeX/png/Main/Regular/141/
 223C.png"><img alt="" src="http://www-old.newton.ac.uk/js/MathJax/current/
 fonts/HTML-CSS/TeX/png/Main/Regular/141/0031.png"></span> </span>   Ga.  A
 t the time he made this discovery almost all earth scientists believed tha
 t the continents had never moved.  This belief changed completely over the
  following five years\, to be replaced by a general acceptance that the Ea
 rth&#39\;s mantle is a vigorously convecting fluid with a Rayleigh number 
 of <span><span><span><span><span><img alt="" src="http://www-old.newton.ac
 .uk/js/MathJax/current/fonts/HTML-CSS/TeX/png/Main/Regular/141/0031.png"><
 img alt="" src="http://www-old.newton.ac.uk/js/MathJax/current/fonts/HTML-
 CSS/TeX/png/Main/Regular/141/0030.png"></span> </span><span><img alt="" sr
 c="http://www-old.newton.ac.uk/js/MathJax/current/fonts/HTML-CSS/TeX/png/M
 ain/Regular/100/0036.png"> </span></span><img alt="" src="http://www-old.n
 ewton.ac.uk/js/MathJax/current/fonts/HTML-CSS/TeX/png/Main/Regular/141/221
 2.png"><span><span><span><img alt="" src="http://www-old.newton.ac.uk/js/M
 athJax/current/fonts/HTML-CSS/TeX/png/Main/Regular/141/0031.png"><img alt=
 "" src="http://www-old.newton.ac.uk/js/MathJax/current/fonts/HTML-CSS/TeX/
 png/Main/Regular/141/0030.png"></span> </span><span><img alt="" src="http:
 //www-old.newton.ac.uk/js/MathJax/current/fonts/HTML-CSS/TeX/png/Main/Regu
 lar/100/0037.png"> </span></span></span> </span>  .  Gast&#39\;s discovery
 \, which was quickly confirmed by many other measurements\, then slowly be
 came recognised as more and more unexpected.  How can the source regions o
 f ocean island basalts remain intact for long periods of time in a vigorou
 sly convecting fluid\, and\, if they are drawn out into thin sheets\, as s
 eems almost inevitable\, how can melt be extracted preferentially from suc
 h a well stirred inhomogeneous material?  Attempts to answer these questio
 ns have concerned igneous petrologists and geochemists ever since Gast&#39
 \;s discovery\, and are of central concern to this workshop.  Though the r
 esulting work has lead to considerable progress in understanding the proce
 ss of melt generation\, and some progress in understanding how it moves\, 
 it has not yet thrown much light on the original question.&nbsp\;
LOCATION:Seminar Room 1\, Newton Institute
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