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zeolite and prehnite-pumpellyite facies metabasalts

KR
Kent Ratajeski
Tue, Jan 28, 2025 2:30 PM

All,

Another teaching-oriented question for you.  In lecture, I will include brief discussions of the zeolite and prehnite-pumpellyite metamorphic facies, but I'm wondering what to do for the lab.  We have tons of amygdaloidal basalts with white and greenish minerals in the vesicles, but that isn't really enough to establish equilibrium mineral assemblages for the whole rock.  As I understand it, metabasalts are actually resistant to zeolite facies metamorphism, and metasediments are where you see actual equilibrium mineral assemblages.  Is that true for prehnite-pumpellyite as well?

So what do I do?  (A) Throw the samples in there, but say something like "this may or may not actually be an example of the [zeolite/preh-pump] facies, or (B) err on the side of simplicity and sacrifice accuracy and honesty and say "white amygdaloids = zeolite facies; green amygdaloids = preh-pump facies?

Kent


Dr. Kent Ratajeski

Lecturer and Dice Mineralogical Museum Director
North Hall 081

Department of Geology, Geography, and Environment

Calvin University

3201 Burton St. SE
Grand Rapids, MI  49546
(616) 526-6769
https://calvin.edu/directory/people/kent-ratajeski

All, Another teaching-oriented question for you. In lecture, I will include brief discussions of the zeolite and prehnite-pumpellyite metamorphic facies, but I'm wondering what to do for the lab. We have tons of amygdaloidal basalts with white and greenish minerals in the vesicles, but that isn't really enough to establish equilibrium mineral assemblages for the whole rock. As I understand it, metabasalts are actually resistant to zeolite facies metamorphism, and metasediments are where you see actual equilibrium mineral assemblages. Is that true for prehnite-pumpellyite as well? So what do I do? (A) Throw the samples in there, but say something like "this may or may not actually be an example of the [zeolite/preh-pump] facies, or (B) err on the side of simplicity and sacrifice accuracy and honesty and say "white amygdaloids = zeolite facies; green amygdaloids = preh-pump facies? Kent --- Dr. Kent Ratajeski Lecturer and Dice Mineralogical Museum Director North Hall 081 Department of Geology, Geography, and Environment Calvin University 3201 Burton St. SE Grand Rapids, MI 49546 (616) 526-6769 https://calvin.edu/directory/people/kent-ratajeski
MK
Matt Kohn
Fri, Jan 31, 2025 8:33 PM

Hi,

I’ve tried posting this message a couple times, but the link to Perkins et al. in the last paragraph isn’t working. So, just copy and paste.

Hi Kent,

I suspect my response won’t help you much at this date, but Allen Glazner and I decided to just lump both facies into “incipient metamorphism” and not talk about them directly as a facies. There are several reasons for that decision – it’s hard to find good teaching materials, it’s hard to establish equilibrium, and there’s not a lot of research on those facies (as a facies – lots of work on zeolites, of course).

Also, in the context of teaching igneous and metamorphic petrology, I don’t really teach metamorphic facies for facies sake. Rather, following Allen’s approach, I teach about processes and the mineral assemblages that go along with them. This can include facies, but doesn’t have to. So, I put my examples of zeolites (which I purchased off the internet, BTW) in the section on alteration of oceanic crust at mid-ocean ridges. There, I have examples of metamorphism of basalts and gabbros (zeolitized basalt, greenschists, amphibolites, granulites), but also altered ultramafic rocks (serpentinites and orthoamphibole rocks). Facies does come up, but that’s not really the point of the lab. There’s an earlier lab (by a couple weeks) on the formation of oceanic crust with rocks like basalts, gabbros, and peridotites – the feed stock for the more important metamorphic rocks.  ;)

Anyway, something that might help – Dex Perkins, John Brady, and I posted several photos of zeolites to our book (https://optical.minpet.org https://optical.minpet.org/) including some amygdaloidal basalts. For the ones I contributed, I spent quite a lot of time finding a range of zeolites on ebay/etsy and verifying their identify with Raman before labeling the photos. So, you can be sure they’re ID’d correctly. Personally, I find them texturally interesting, but optically rather dull (sorry to any zeolitiphiles out there). Except the gmelinite (online fig. 2.6.6). That’s a beauty!

Best,

Matt

Note: While I may send email outside of regular business hours, I do not expect the same from others.


Dr. Matthew J. Kohn, University Distinguished Professor
Department of Geosciences, Boise State University
1910 University Dr.; MS1535
Boise, ID 83725-1535
mattkohn@boisestate.edu
https://www.boisestate.edu/earth/people/matthew-j-kohn/
fax: (208)-426-4061
Pronouns: He/him/his
China book:
https://www.amazon.com/dp/B0BRXWNTS6 https://www.amazon.com/dp/B0BRXWNTS6,
https://www.amazon.com/dp/B0BRZ2XRV9 https://www.amazon.com/dp/B0BRZ2XRV9
Optical Mineralogy Book:
https://optical.minpet.org/ https://optical.minpet.org/
Petrology and Plate Tectonics Book:
https://global.oup.com/academic/product/petrology-and-plate-tectonics-9780190490645 https://global.oup.com/academic/product/petrology-and-plate-tectonics-9780190490645


On Jan 28, 2025, at 7:30 AM, Kent Ratajeski via MSA-talk msa-talk@minlists.org wrote:

All,

Another teaching-oriented question for you.  In lecture, I will include brief discussions of the zeolite and prehnite-pumpellyite metamorphic facies, but I'm wondering what to do for the lab.  We have tons of amygdaloidal basalts with white and greenish minerals in the vesicles, but that isn't really enough to establish equilibrium mineral assemblages for the whole rock.  As I understand it, metabasalts are actually resistant to zeolite facies metamorphism, and metasediments are where you see actual equilibrium mineral assemblages.  Is that true for prehnite-pumpellyite as well?

So what do I do?  (A) Throw the samples in there, but say something like "this may or may not actually be an example of the [zeolite/preh-pump] facies, or (B) err on the side of simplicity and sacrifice accuracy and honesty and say "white amygdaloids = zeolite facies; green amygdaloids = preh-pump facies?

Kent


Dr. Kent Ratajeski
Lecturer and Dice Mineralogical Museum Director
North Hall 081
Department of Geology, Geography, and Environment
Calvin University
3201 Burton St. SE
Grand Rapids, MI  49546
(616) 526-6769
https://calvin.edu/directory/people/kent-ratajeski https://calvin.edu/directory/people/kent-ratajeski


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Hi, I’ve tried posting this message a couple times, but the link to Perkins et al. in the last paragraph isn’t working. So, just copy and paste. Hi Kent, I suspect my response won’t help you much at this date, but Allen Glazner and I decided to just lump both facies into “incipient metamorphism” and not talk about them directly as a facies. There are several reasons for that decision – it’s hard to find good teaching materials, it’s hard to establish equilibrium, and there’s not a lot of research on those facies (as a facies – lots of work on zeolites, of course). Also, in the context of teaching igneous and metamorphic petrology, I don’t really teach metamorphic facies for facies sake. Rather, following Allen’s approach, I teach about processes and the mineral assemblages that go along with them. This can include facies, but doesn’t have to. So, I put my examples of zeolites (which I purchased off the internet, BTW) in the section on alteration of oceanic crust at mid-ocean ridges. There, I have examples of metamorphism of basalts and gabbros (zeolitized basalt, greenschists, amphibolites, granulites), but also altered ultramafic rocks (serpentinites and orthoamphibole rocks). Facies does come up, but that’s not really the point of the lab. There’s an earlier lab (by a couple weeks) on the formation of oceanic crust with rocks like basalts, gabbros, and peridotites – the feed stock for the more important metamorphic rocks. ;) Anyway, something that might help – Dex Perkins, John Brady, and I posted several photos of zeolites to our book (https://optical.minpet.org <https://optical.minpet.org/>) including some amygdaloidal basalts. For the ones I contributed, I spent quite a lot of time finding a range of zeolites on ebay/etsy and verifying their identify with Raman before labeling the photos. So, you can be sure they’re ID’d correctly. Personally, I find them texturally interesting, but optically rather dull (sorry to any zeolitiphiles out there). Except the gmelinite (online fig. 2.6.6). That’s a beauty! Best, Matt Note: While I may send email outside of regular business hours, I do not expect the same from others. ******************************************************************************************************************************* Dr. Matthew J. Kohn, University Distinguished Professor Department of Geosciences, Boise State University 1910 University Dr.; MS1535 Boise, ID 83725-1535 mattkohn@boisestate.edu https://www.boisestate.edu/earth/people/matthew-j-kohn/ fax: (208)-426-4061 Pronouns: He/him/his China book: https://www.amazon.com/dp/B0BRXWNTS6 <https://www.amazon.com/dp/B0BRXWNTS6>, https://www.amazon.com/dp/B0BRZ2XRV9 <https://www.amazon.com/dp/B0BRZ2XRV9> Optical Mineralogy Book: https://optical.minpet.org/ <https://optical.minpet.org/> Petrology and Plate Tectonics Book: https://global.oup.com/academic/product/petrology-and-plate-tectonics-9780190490645 <https://global.oup.com/academic/product/petrology-and-plate-tectonics-9780190490645> ******************************************************************************************************************************* > On Jan 28, 2025, at 7:30 AM, Kent Ratajeski via MSA-talk <msa-talk@minlists.org> wrote: > > All, > > Another teaching-oriented question for you. In lecture, I will include brief discussions of the zeolite and prehnite-pumpellyite metamorphic facies, but I'm wondering what to do for the lab. We have tons of amygdaloidal basalts with white and greenish minerals in the vesicles, but that isn't really enough to establish equilibrium mineral assemblages for the whole rock. As I understand it, metabasalts are actually resistant to zeolite facies metamorphism, and metasediments are where you see actual equilibrium mineral assemblages. Is that true for prehnite-pumpellyite as well? > > So what do I do? (A) Throw the samples in there, but say something like "this may or may not actually be an example of the [zeolite/preh-pump] facies, or (B) err on the side of simplicity and sacrifice accuracy and honesty and say "white amygdaloids = zeolite facies; green amygdaloids = preh-pump facies? > > Kent > > > --- > Dr. Kent Ratajeski > Lecturer and Dice Mineralogical Museum Director > North Hall 081 > Department of Geology, Geography, and Environment > Calvin University > 3201 Burton St. SE > Grand Rapids, MI 49546 > (616) 526-6769 > https://calvin.edu/directory/people/kent-ratajeski <https://calvin.edu/directory/people/kent-ratajeski> > _______________________________________________ > MSA-talk mailing list -- msa-talk@minlists.org > To unsubscribe send an email to msa-talk-leave@minlists.org