Dear Dr. Kumar, here a couple of papers of para-amphibolite in greywacke (not all of them are in chem sed rxs!) that may relate to both your tectonic and lithological settings, and complement all the technical very useful information above.
Dear Dr. Kumar, here a couple of papers of para-amphibolite in greywacke (not all of them are in chem sed rxs!) that may relate to both your tectonic and lithological settings, and complement all the technical very useful information above.
I fully agree with Prof. Stephen Kraus suggestions/observations. I am sure you may find chilled margin(s). Many people somehow over look this aspect. Also, can you send /show a photomicrograph of the amphibolite? I wonder whether it could be an ultramafic rock retrograded to amphibolite. KNRAO
I fully agree with Prof. Stephen Kraus suggestions/observations. I am sure you may find chilled margin(s). Many people somehow over look this aspect. Also, can you send /show a photomicrograph of the amphibolite? I wonder whether it could be an ultramafic rock retrograded to amphibolite. KNRAO
You can use the CaO-MgO-FeO triangular diagram or the mg-c-al-alk triangle of Niggli which differentiate between Para- and ortho-amphibolite. Also relict texture of igneous rocks such as relict ophitic texture is typical of ortho-amphibolite.
You can use the CaO-MgO-FeO triangular diagram or the mg-c-al-alk triangle of Niggli which differentiate between Para- and ortho-amphibolite. Also relict texture of igneous rocks such as relict ophitic texture is typical of ortho-amphibolite.
Look at Winchester JA 1984. The geochemistry of the Strathconon amphibolites. Scottish Journal of Geology vol.20, 37-51. and Plank, T. 2005. Contraints from Th/La on sediment re-cycling at subduction zones and the evolution of the continents. Journal of Petrology. doi:10.1093/pterology/egi005
Look at Winchester JA 1984. The geochemistry of the Strathconon amphibolites. Scottish Journal of Geology vol.20, 37-51. and Plank, T. 2005. Contraints from Th/La on sediment re-cycling at subduction zones and the evolution of the continents. Journal of Petrology. doi:10.1093/pterology/egi005
Dear Chandan, the arguments you present in your last posting indeed point towards a sedimentary protolith. However, I think the most important question is whether the quartz grains are rounded because of a sedimentary origin, or because of anhedral growth during later metamorphism. In the second case, this unit's protolith could also be a magmatic sill that has intruded concordantly into the sedimentary sequence and then been metamorphosed together with the rest. Could what you call relics of sedimentary layering also be magmatic banding? Are there any hints/relics of a chilled margin along the boundary with the underlying/overlying sediment packages?
And if the unit in question has undergone amphibolite facies metamorphism, why is the dolomitic limestone still limestone and not marble, being (according to your initial information) part of the same sequence? It should have enjoyed the same grade of metamorphism as the rest, shouldn't it?
Dear Chandan, the arguments you present in your last posting indeed point towards a sedimentary protolith. However, I think the most important question is whether the quartz grains are rounded because of a sedimentary origin, or because of anhedral growth during later metamorphism. In the second case, this unit's protolith could also be a magmatic sill that has intruded concordantly into the sedimentary sequence and then been metamorphosed together with the rest. Could what you call relics of sedimentary layering also be magmatic banding? Are there any hints/relics of a chilled margin along the boundary with the underlying/overlying sediment packages?
And if the unit in question has undergone amphibolite facies metamorphism, why is the dolomitic limestone still limestone and not marble, being (according to your initial information) part of the same sequence? It should have enjoyed the same grade of metamorphism as the rest, shouldn't it?
Ortho-amphibolites have higher Cr,Ni and Ti contents and low k ratios, but since most of basic igneous rock have low Cr, Ni and Ti content and also alkali metamorphism normally disturbs k ratios, therefore there should be number of analysis and compare data with other places to give reliable trend.
Ortho-amphibolites have higher Cr,Ni and Ti contents and low k ratios, but since most of basic igneous rock have low Cr, Ni and Ti content and also alkali metamorphism normally disturbs k ratios, therefore there should be number of analysis and compare data with other places to give reliable trend.
Dear Chandan, You have plenty of useful comments and suggestions, particularly those of Stephen Kraus. In 1960s and 1970s, there was a hot controversy regarding the ortho versus para origin of banded amphibolites of the type you are discussing. BE Leake and his colleagues (including BW Evans) discussed the problem in considerable detail. Geochemistry, including Cr, Ni, Ti, was used in the distinction, apart from other arguments. You may like to read a paper on the origin of amphibolites in the kohistan magmatic arc of the NW Himalaya (MQ Jan, 1988. Geochemistry of amphibolites....Mineralogical Magazine 52, 147-59). In general, I would think that amphibolites should be derived from mafic precursors. They can be sills or tuffaceou beds alternating with sedimentary beds.You did not mention whether your rocks are thin-bedded or not. In thin-bedded marly rocks, amphibolite bands can develop during metamorphism. Finally, the rounded shape of the quartz grains in amphibolite grade metamorphism cannot be alluded to transport. At this grade of metamorphism, quarts as well as other minerals would be the product of metamorphic recrystallization. Best, Qasim
Dear Chandan, You have plenty of useful comments and suggestions, particularly those of Stephen Kraus. In 1960s and 1970s, there was a hot controversy regarding the ortho versus para origin of banded amphibolites of the type you are discussing. BE Leake and his colleagues (including BW Evans) discussed the problem in considerable detail. Geochemistry, including Cr, Ni, Ti, was used in the distinction, apart from other arguments. You may like to read a paper on the origin of amphibolites in the kohistan magmatic arc of the NW Himalaya (MQ Jan, 1988. Geochemistry of amphibolites....Mineralogical Magazine 52, 147-59). In general, I would think that amphibolites should be derived from mafic precursors. They can be sills or tuffaceou beds alternating with sedimentary beds.You did not mention whether your rocks are thin-bedded or not. In thin-bedded marly rocks, amphibolite bands can develop during metamorphism. Finally, the rounded shape of the quartz grains in amphibolite grade metamorphism cannot be alluded to transport. At this grade of metamorphism, quarts as well as other minerals would be the product of metamorphic recrystallization. Best, Qasim
See paper by Phil Orville in AJS (1960's?), if you haven't seen it already.
Ed Ghent
See paper by Phil Orville in AJS (1960's?), if you haven't seen it already.
Ed Ghent
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Dear Dr. Kumar, here a couple of papers of para-amphibolite in greywacke (not all of them are in chem sed rxs!) that may relate to both your tectonic and lithological settings, and complement all the technical very useful information above.
Archean-Proteroz, interbanding of sed rxs and amphibolite:
1. "Unique amphibolite–iron formation assemblage in the
Kawaweyak Lake area, Manitoba"
http://www.manitoba.ca/iem/mrd/geo/field/roa07pdfs/GS-6.pdf
2. "Geological investigations in the Manasan Falls area, Thompson
Nickel Belt, Manitoba"
http://www.manitoba.ca/iem/mrd/geo/field/roa11pdfs/GS-9.pdf
3. Theye et al. 2012 'Significance of amphibole compositional zoning in para-amphibolite"
http://meetingorganizer.copernicus.org/EMC2012/EMC2012-388.pdf
Hope it helps,
Andres Urrutia
Dear Dr. Kumar, here a couple of papers of para-amphibolite in greywacke (not all of them are in chem sed rxs!) that may relate to both your tectonic and lithological settings, and complement all the technical very useful information above.
Archean-Proteroz, interbanding of sed rxs and amphibolite:
1. "Unique amphibolite–iron formation assemblage in the
Kawaweyak Lake area, Manitoba"
http://www.manitoba.ca/iem/mrd/geo/field/roa07pdfs/GS-6.pdf
2. "Geological investigations in the Manasan Falls area, Thompson
Nickel Belt, Manitoba"
http://www.manitoba.ca/iem/mrd/geo/field/roa11pdfs/GS-9.pdf
3. Theye et al. 2012 'Significance of amphibole compositional zoning in para-amphibolite"
http://meetingorganizer.copernicus.org/EMC2012/EMC2012-388.pdf
Hope it helps,
Andres Urrutia
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I fully agree with Prof. Stephen Kraus suggestions/observations. I am sure you may find chilled margin(s). Many people somehow over look this aspect. Also, can you send /show a photomicrograph of the amphibolite? I wonder whether it could be an ultramafic rock retrograded to amphibolite. KNRAO
I fully agree with Prof. Stephen Kraus suggestions/observations. I am sure you may find chilled margin(s). Many people somehow over look this aspect. Also, can you send /show a photomicrograph of the amphibolite? I wonder whether it could be an ultramafic rock retrograded to amphibolite. KNRAO
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VOTE
You can use the CaO-MgO-FeO triangular diagram or the mg-c-al-alk triangle of Niggli which differentiate between Para- and ortho-amphibolite. Also relict texture of igneous rocks such as relict ophitic texture is typical of ortho-amphibolite.
You can use the CaO-MgO-FeO triangular diagram or the mg-c-al-alk triangle of Niggli which differentiate between Para- and ortho-amphibolite. Also relict texture of igneous rocks such as relict ophitic texture is typical of ortho-amphibolite.
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Yes, it's possible. Some variation diagrams are also useful.
Yes, it's possible. Some variation diagrams are also useful.
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I have a question
What is the differences between amphibole schist and para-amphibolite in amphibolite metamorphic facies?
I have a question
What is the differences between amphibole schist and para-amphibolite in amphibolite metamorphic facies?
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The difference between the two types was explained in the following links
https://academic.oup.com/petrology/article-abstract/5/2/238/1576422?redirectedFrom=PDF
http://www.j-igu.in/igu%2021-5%20(web)/paper6.pdf
Best Regards Dr. Chandan Kumar B
The difference between the two types was explained in the following links
https://academic.oup.com/petrology/article-abstract/5/2/238/1576422?redirectedFrom=PDF
http://www.j-igu.in/igu%2021-5%20(web)/paper6.pdf
Best Regards Dr. Chandan Kumar B
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Look at
Winchester JA 1984. The geochemistry of the Strathconon amphibolites. Scottish Journal of Geology vol.20, 37-51.
and
Plank, T. 2005. Contraints from Th/La on sediment re-cycling at subduction zones and the evolution of the continents. Journal of Petrology. doi:10.1093/pterology/egi005
Look at
Winchester JA 1984. The geochemistry of the Strathconon amphibolites. Scottish Journal of Geology vol.20, 37-51.
and
Plank, T. 2005. Contraints from Th/La on sediment re-cycling at subduction zones and the evolution of the continents. Journal of Petrology. doi:10.1093/pterology/egi005
More
VOTE
Dear Chandan,
the arguments you present in your last posting indeed point towards a sedimentary protolith. However, I think the most important question is whether the quartz grains are rounded because of a sedimentary origin, or because of anhedral growth during later metamorphism. In the second case, this unit's protolith could also be a magmatic sill that has intruded concordantly into the sedimentary sequence and then been metamorphosed together with the rest. Could what you call relics of sedimentary layering also be magmatic banding? Are there any hints/relics of a chilled margin along the boundary with the underlying/overlying sediment packages?
And if the unit in question has undergone amphibolite facies metamorphism, why is the dolomitic limestone still limestone and not marble, being (according to your initial information) part of the same sequence? It should have enjoyed the same grade of metamorphism as the rest, shouldn't it?
Cheers,
Stefan
Dear Chandan,
the arguments you present in your last posting indeed point towards a sedimentary protolith. However, I think the most important question is whether the quartz grains are rounded because of a sedimentary origin, or because of anhedral growth during later metamorphism. In the second case, this unit's protolith could also be a magmatic sill that has intruded concordantly into the sedimentary sequence and then been metamorphosed together with the rest. Could what you call relics of sedimentary layering also be magmatic banding? Are there any hints/relics of a chilled margin along the boundary with the underlying/overlying sediment packages?
And if the unit in question has undergone amphibolite facies metamorphism, why is the dolomitic limestone still limestone and not marble, being (according to your initial information) part of the same sequence? It should have enjoyed the same grade of metamorphism as the rest, shouldn't it?
Cheers,
Stefan
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VOTE
Ortho-amphibolites have higher Cr,Ni and Ti contents and low k ratios, but since most of basic igneous rock have low Cr, Ni and Ti content and also alkali metamorphism normally disturbs k ratios, therefore there should be number of analysis and compare data with other places to give reliable trend.
Ortho-amphibolites have higher Cr,Ni and Ti contents and low k ratios, but since most of basic igneous rock have low Cr, Ni and Ti content and also alkali metamorphism normally disturbs k ratios, therefore there should be number of analysis and compare data with other places to give reliable trend.
More
VOTE
Dear Chandan,
You have plenty of useful comments and suggestions, particularly those of Stephen Kraus. In 1960s and 1970s, there was a hot controversy regarding the ortho versus para origin of banded amphibolites of the type you are discussing. BE Leake and his colleagues (including BW Evans) discussed the problem in considerable detail. Geochemistry, including Cr, Ni, Ti, was used in the distinction, apart from other arguments. You may like to read a paper on the origin of amphibolites in the kohistan magmatic arc of the NW Himalaya (MQ Jan, 1988. Geochemistry of amphibolites....Mineralogical Magazine 52, 147-59).
In general, I would think that amphibolites should be derived from mafic precursors. They can be sills or tuffaceou beds alternating with sedimentary beds.You did not mention whether your rocks are thin-bedded or not. In thin-bedded marly rocks, amphibolite bands can develop during metamorphism.
Finally, the rounded shape of the quartz grains in amphibolite grade metamorphism cannot be alluded to transport. At this grade of metamorphism, quarts as well as other minerals would be the product of metamorphic recrystallization.
Best,
Qasim
Dear Chandan,
You have plenty of useful comments and suggestions, particularly those of Stephen Kraus. In 1960s and 1970s, there was a hot controversy regarding the ortho versus para origin of banded amphibolites of the type you are discussing. BE Leake and his colleagues (including BW Evans) discussed the problem in considerable detail. Geochemistry, including Cr, Ni, Ti, was used in the distinction, apart from other arguments. You may like to read a paper on the origin of amphibolites in the kohistan magmatic arc of the NW Himalaya (MQ Jan, 1988. Geochemistry of amphibolites....Mineralogical Magazine 52, 147-59).
In general, I would think that amphibolites should be derived from mafic precursors. They can be sills or tuffaceou beds alternating with sedimentary beds.You did not mention whether your rocks are thin-bedded or not. In thin-bedded marly rocks, amphibolite bands can develop during metamorphism.
Finally, the rounded shape of the quartz grains in amphibolite grade metamorphism cannot be alluded to transport. At this grade of metamorphism, quarts as well as other minerals would be the product of metamorphic recrystallization.
Best,
Qasim
More
VOTE