JiscMail Logo
Email discussion lists for the UK Education and Research communities

Help for GEO-METAMORPHISM Archives


GEO-METAMORPHISM Archives

GEO-METAMORPHISM Archives


GEO-METAMORPHISM@JISCMAIL.AC.UK


View:

Message:

[

First

|

Previous

|

Next

|

Last

]

By Topic:

[

First

|

Previous

|

Next

|

Last

]

By Author:

[

First

|

Previous

|

Next

|

Last

]

Font:

Proportional Font

LISTSERV Archives

LISTSERV Archives

GEO-METAMORPHISM Home

GEO-METAMORPHISM Home

GEO-METAMORPHISM  October 2012

GEO-METAMORPHISM October 2012

Options

Subscribe or Unsubscribe

Subscribe or Unsubscribe

Log In

Log In

Get Password

Get Password

Subject:

Re: Metasomatism

From:

Sumit Chakraborty <[log in to unmask]>

Reply-To:

Metamorphic Studies Group <[log in to unmask]>, Sumit Chakraborty <[log in to unmask]>

Date:

Fri, 12 Oct 2012 18:50:22 +0200

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (79 lines)

This is good fun, folks. Now that I have triggered this off with a 
comment that included "text books", I figured I can get in again and 
point people to the first few pages of Ch. 19 of Spear. Would make good 
reading in this context. While you are at it, pieces of Winter, Clarke 
and Vernon, and Philpotts and Ague, would add fun to the deal too. And 
just in case you were about to, don't forget Bruce (I mean the book now) 
either.

To finish cooking my spicy curry, here is some thought for the weekend: 
Korzhinskii's rules says that if a ch. pot is constrained, the number of 
phases get reduced by one. WE *interpret* constrained ch. pot to mean 
open system, fluid transport etc. So it follows that if fluids flow, but 
ch. pots do not become pinned by that, Korzhinskii has told us nothing 
about the number of phases. I could not help noticing that in all of 
Kurt's examples, the fluid was CO2. Not a great "constraint-er" of ch. 
pot of Mg, Fe, Si and the like...?

I could not let such fun die out, could I?

Have a



On 10/12/2012 6:27 PM, Bruce Yardley wrote:
> Dear All
>
> All Kurt says is of course true, but, because you have to define components differently for the altered rock rather than the initial dunite, none of his examples involve a decrease in the number of degrees of freedom. In both cases, if more fluid flow occurs, one of the secondary phases will disappear and the number of degrees of freedom will increase. There are plenty of field examples that show this in marbles and ultramafic rocks. So really, we should say that infiltration metasomatism leads to an increase in the number of degrees of freedom, not a decrease in the number of phases.
>
> If you are baffled by that: the altered dunite started off with just olivine having constant ratios of Fe:Mg:Si (so they combine as 1 component). As soon as a trace of CO2-H2O fluid arrives (and some H2 is lost) it makes a phase which concentrates the Si (enstatite), a phase with just Mg (magnesite) and a phase with the Fe (magnetite). Now these 3 elements must be treated as separate components because their relative proportions are different in each mineral. So we have gone from a rock with 1 immobile component and 1 solid phase to a rock with 3 immobile components and 3 solid phases. For sure, it may have begun to experience metasomatism but at present it still has reserves of minerals available to react and modify the fluid composition to something defined by the rock. Eventually, if the rock is fortunate enough to experience even more fluid infiltration, all the olivine will go and the enstatite may then become carbonated. When the carbonation of enstatite is complete, the number of phases has been reduced by 1 because we now have another component acting as  mobile (the Si is being leached out).
>
> And to get back to the original query which we lost sight of some time ago - there is some really nice recent work about alteration of sea floor rocks from Ron Frost (B.R. Frost if you are searching) and his collaborators.
>
> Bruce
>
> Professor Bruce Yardley
> School of Earth and Environment
> University of Leeds
> Leeds LS2 9JT, UK
>
> Tel: +44 (0)113 3435227
> Fax: +44 (0)113 3435259
>
> -----Original Message-----
> From: Metamorphic Studies Group [mailto:[log in to unmask]] On Behalf Of Kurt Bucher
> Sent: 12 October 2012 13:06
> To: [log in to unmask]
> Subject: [geo-metamorphism] Metasomatism
>
> Dear All,
>
> The metasomatism topic seems to be attractive. It has, at least, attracted sevral responses that have been adressed directly to me personally. This is of course not the purpose of a mailbase discussion.
>
> Anyhow: I have labeled the photomicrograph that was attached to my last mail. On this picture you can see two extremely resorbed olivine grains (olivine 1 and olivine 2) from the original dunite. The metasomatic reaction products are Mg-carbonate (magnesite) and Mg-silicate (enstatite). The dark opaque phase is magnetite (Fe-oxyde). It does not participate in the reaction. It is irrelevant for Korzinsky games.
>
> The frozen-in reaction recorded by the texture is: Olivine + CO2 = Enstatite + Magnesite.
> The reaction, as shown, is an efficient natural CO2-sequestration reaction. The CO2 from the gas/fluid phase is transferred to a solid ( magnesite).
>
> However, this was not my major point. The point is, that the metasomatic rock contains more minerals than the starting material.
>
> Cheers
> Kurt
>


-- 


***************** Sumit Chakraborty ****************************************
	http://www.gmg.ruhr-uni-bochum.de/petrologie

Institut fuer Geologie, Mineralogie und Geophysik;
Ruhr-Universität Bochum; D-44780 Bochum; Germany


Email: [log in to unmask]
Tel: +49-(0)234-322 4395 / 8155
Fax: +49-(0)234-321 4433
*****************************************************************************

Top of Message | Previous Page | Permalink

JiscMail Tools


RSS Feeds and Sharing


Advanced Options


Archives

March 2024
February 2024
January 2024
December 2023
November 2023
October 2023
September 2023
August 2023
July 2023
June 2023
May 2023
April 2023
March 2023
February 2023
January 2023
December 2022
November 2022
October 2022
September 2022
August 2022
July 2022
June 2022
May 2022
April 2022
March 2022
February 2022
January 2022
December 2021
November 2021
October 2021
September 2021
August 2021
July 2021
June 2021
May 2021
April 2021
March 2021
February 2021
January 2021
December 2020
November 2020
October 2020
September 2020
August 2020
July 2020
June 2020
May 2020
April 2020
March 2020
February 2020
January 2020
December 2019
November 2019
October 2019
September 2019
August 2019
July 2019
June 2019
May 2019
April 2019
March 2019
February 2019
January 2019
December 2018
November 2018
October 2018
September 2018
August 2018
July 2018
June 2018
May 2018
April 2018
March 2018
February 2018
January 2018
December 2017
November 2017
October 2017
September 2017
August 2017
July 2017
June 2017
May 2017
April 2017
March 2017
February 2017
January 2017
December 2016
November 2016
October 2016
September 2016
August 2016
July 2016
June 2016
May 2016
April 2016
March 2016
February 2016
January 2016
December 2015
November 2015
October 2015
September 2015
August 2015
July 2015
June 2015
May 2015
April 2015
March 2015
February 2015
January 2015
December 2014
November 2014
October 2014
September 2014
August 2014
July 2014
June 2014
May 2014
April 2014
March 2014
February 2014
January 2014
December 2013
November 2013
October 2013
September 2013
August 2013
July 2013
June 2013
May 2013
April 2013
March 2013
February 2013
January 2013
December 2012
November 2012
October 2012
September 2012
August 2012
July 2012
June 2012
May 2012
April 2012
March 2012
February 2012
January 2012
December 2011
November 2011
October 2011
September 2011
August 2011
July 2011
June 2011
May 2011
April 2011
March 2011
February 2011
January 2011
December 2010
November 2010
October 2010
September 2010
August 2010
July 2010
June 2010
May 2010
April 2010
March 2010
February 2010
January 2010
December 2009
November 2009
October 2009
September 2009
August 2009
July 2009
June 2009
May 2009
April 2009
March 2009
February 2009
January 2009
December 2008
November 2008
October 2008
September 2008
August 2008
July 2008
June 2008
May 2008
April 2008
March 2008
February 2008
January 2008
December 2007
November 2007
October 2007
September 2007
August 2007
July 2007
June 2007
May 2007
April 2007
March 2007
February 2007
January 2007
2006
2005
2004
2003
2002
2001
2000
1999
1998


JiscMail is a Jisc service.

View our service policies at https://www.jiscmail.ac.uk/policyandsecurity/ and Jisc's privacy policy at https://www.jisc.ac.uk/website/privacy-notice

For help and support help@jisc.ac.uk

Secured by F-Secure Anti-Virus CataList Email List Search Powered by the LISTSERV Email List Manager