Abstract Details
(2020) Felsic Magma Diversity, & Triumphs and Perils of Granite Typology
Miller C, Miller J & Gualda G
https://doi.org/10.46427/gold2020.1804
The author has not provided any additional details.
04j: Room 1, Saturday 27th June 00:30 - 00:33
Calvin Miller
View all 2 abstracts at Goldschmidt2020
View abstracts at 2 conferences in series
Jonathan Miller
Guilherme A. R. Gualda View all 5 abstracts at Goldschmidt2020 View abstracts at 4 conferences in series
Jonathan Miller
Guilherme A. R. Gualda View all 5 abstracts at Goldschmidt2020 View abstracts at 4 conferences in series
Listed below are questions that have been submitted by the community that the author will try and cover in their presentation. To submit a question, ensure you are signed in to the website. Authors or session conveners approve questions before they are displayed here.
Submitted by Changqian Ma on Sunday 14th June 11:10
Hi, Calvin! Due to the diversity of granite types, genesis, and magma processes, in your opinion, what kind of granite research paradigm should we have? Thank you so much!
Hi, Calvin! Due to the diversity of granite types, genesis, and magma processes, in your opinion, what kind of granite research paradigm should we have? Thank you so much!
Submitted by Changqian Ma on Sunday 14th June 11:12
Hi, Calvin! Due to the diversity of granite types, genesis, and magma processes, in your opinion, what kind of granite research paradigm should we have? Thank you so much! Changqian
This is a very large, and very challenging, question! Maybe the most important simple response: my view of the granite research paradigm is that there can be no (single) paradigm: diversity, in terms of sources, is the rule. Alternatively, one could start with feldspar-quartz-melt equilibria – beginning with Tuttle & Bowen, and with observations of chemistry and dominant phase assemblages in felsic igneous rocks – as the founding simple paradigm. This is what granites (and rhyolites) have in common. The central question, at which diverse models (paradigms) are then aimed: how do melts saturated in quartz+feldspar (or nearly saturated in both) form? What are paths to this composition? What are contributing sources? Are they essentially primary, substantially fractionated, strongly affected by assimilation? (General answer in my view: granites (and rhyolites) are produced have a wide array of source contributions and their felsic compositions are consequence of various combinations of partial melting, fractional crystallization, and assimilation.)
Hi, Calvin! Due to the diversity of granite types, genesis, and magma processes, in your opinion, what kind of granite research paradigm should we have? Thank you so much! Changqian
This is a very large, and very challenging, question! Maybe the most important simple response: my view of the granite research paradigm is that there can be no (single) paradigm: diversity, in terms of sources, is the rule. Alternatively, one could start with feldspar-quartz-melt equilibria – beginning with Tuttle & Bowen, and with observations of chemistry and dominant phase assemblages in felsic igneous rocks – as the founding simple paradigm. This is what granites (and rhyolites) have in common. The central question, at which diverse models (paradigms) are then aimed: how do melts saturated in quartz+feldspar (or nearly saturated in both) form? What are paths to this composition? What are contributing sources? Are they essentially primary, substantially fractionated, strongly affected by assimilation? (General answer in my view: granites (and rhyolites) are produced have a wide array of source contributions and their felsic compositions are consequence of various combinations of partial melting, fractional crystallization, and assimilation.)
Submitted by Changqian Ma on Saturday 20th June 10:12
Thank you for your wonderful keynote. You emphasized the importance of volcanic records in the lessons section at the end. What can we learn from the study of volcanic rocks about granites?
Thanks, Changqian! In my opinion: First, felsic volcanic rocks reveal the nature of mobile magmas that are akin to those that form granites. They are almost instantaneously quenched form mobile-magma state and thus retain a textural and chemical (if they haven’t been modified much by subsolidus alteration). If they contain unaltered glass, they also reveal melt compositions. Inferring melt compositions and textures and compositions of mobile magmas from granites encounters much more ambiguity. Volcanic rocks are also invaluable complements to plutonic rocks for assessing upper crustal magmatic processes. They provide a snapshot of eruptible magma and a record of the eruption process. Granites are more of a blurry time exposure that integrates a more complete record of magmatic residence in the crust. Finally, study of volcanic rocks reveals what sorts of felsic magmas erupt and can, conversely, suggest what sorts of magmas rarely or never do. All felsic volcanics have plutonic counterparts, but it appears that some granite types have very few or perhaps no erupted counterparts. Understanding the full life cycles of granitic (felsic) magmas requires assessment of eruption: is eruption of a particular felsic magma type inevitable, possible but uncommon, or nearly possible? And if there is a correlation between magma type and eruption probability: why?
Thank you for your wonderful keynote. You emphasized the importance of volcanic records in the lessons section at the end. What can we learn from the study of volcanic rocks about granites?
Thanks, Changqian! In my opinion: First, felsic volcanic rocks reveal the nature of mobile magmas that are akin to those that form granites. They are almost instantaneously quenched form mobile-magma state and thus retain a textural and chemical (if they haven’t been modified much by subsolidus alteration). If they contain unaltered glass, they also reveal melt compositions. Inferring melt compositions and textures and compositions of mobile magmas from granites encounters much more ambiguity. Volcanic rocks are also invaluable complements to plutonic rocks for assessing upper crustal magmatic processes. They provide a snapshot of eruptible magma and a record of the eruption process. Granites are more of a blurry time exposure that integrates a more complete record of magmatic residence in the crust. Finally, study of volcanic rocks reveals what sorts of felsic magmas erupt and can, conversely, suggest what sorts of magmas rarely or never do. All felsic volcanics have plutonic counterparts, but it appears that some granite types have very few or perhaps no erupted counterparts. Understanding the full life cycles of granitic (felsic) magmas requires assessment of eruption: is eruption of a particular felsic magma type inevitable, possible but uncommon, or nearly possible? And if there is a correlation between magma type and eruption probability: why?
Submitted by Alan Benimoff on Saturday 27th June 00:35
We have been working on a pyroxene trondhjemite(Albite granite) derived from the fusion of a xenolith of Na rich Loctatong Argilite . High Na is not in accord with S-type granite, but the trondhjemite is derived from argillite. See Benimoff, A. I. and Sclar, C. B. (1984) "Coexisting Silicic and Mafic Melts Resulting From Marginal Fusion of a Xenolith of Lockatong Argillite the Palisades Sill, Graniteville, Staten Island, New York" American Mineralogist, 69, 1005-1014. This might be another type of granite?
We have been working on a pyroxene trondhjemite(Albite granite) derived from the fusion of a xenolith of Na rich Loctatong Argilite . High Na is not in accord with S-type granite, but the trondhjemite is derived from argillite. See Benimoff, A. I. and Sclar, C. B. (1984) "Coexisting Silicic and Mafic Melts Resulting From Marginal Fusion of a Xenolith of Lockatong Argillite the Palisades Sill, Graniteville, Staten Island, New York" American Mineralogist, 69, 1005-1014. This might be another type of granite?
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