Chemical classification of common volcanic rocks based on degree of silica saturation and CaO/K2O ratio
Autor(a) principal: | |
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Data de Publicação: | 2021 |
Outros Autores: | |
Tipo de documento: | Artigo |
Idioma: | eng |
Título da fonte: | Anais da Academia Brasileira de Ciências (Online) |
Texto Completo: | http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652021000501103 |
Resumo: | Abstract Modal classifications of common volcanic rocks are expensive, difficult, or impossible to attain. As a consequence, these rocks are classified using the chemical composition. However, existing classificatory diagrams are unable to identify all 16 families of common volcanic rocks; the most used is the total alkali-silica (TAS) diagram that identifies six families. Rocks not in the TAS diagram are misclassified with other rock names; their names are evolving to extinction, e.g. latite and rhyodacite. Some diagrams use Na2O, which is a complicating element rather than discriminant. Na2O is present both in alkali feldspar and plagioclase making difficult the separation of the amount associated to either feldspar. Silicon, potassium, and calcium are the three major elements with highest variations among volcanic rocks. They are selected for use in two new diagrams confronting CaO/K2O ratio with K2O content (KCK diagrams). One diagram is designed for saturated (intermediate) rocks (quartz <5 vol.%) and the other for oversaturated (acid) volcanic rocks (quartz >5%). These diagrams are tested using compositions of volcanic rocks from Uatumã magmatism in the Amazon Craton and also by plotting compositions of rocks from type-localities and the world averages. The proposed limits between rock families agree with plotted rock compositions. The KCK diagrams are an alternative to existing diagrams to classify volcanic rocks. |
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Chemical classification of common volcanic rocks based on degree of silica saturation and CaO/K2O ratioChemical classificationvolcanic rockssilica saturationUatumã volcanismAbstract Modal classifications of common volcanic rocks are expensive, difficult, or impossible to attain. As a consequence, these rocks are classified using the chemical composition. However, existing classificatory diagrams are unable to identify all 16 families of common volcanic rocks; the most used is the total alkali-silica (TAS) diagram that identifies six families. Rocks not in the TAS diagram are misclassified with other rock names; their names are evolving to extinction, e.g. latite and rhyodacite. Some diagrams use Na2O, which is a complicating element rather than discriminant. Na2O is present both in alkali feldspar and plagioclase making difficult the separation of the amount associated to either feldspar. Silicon, potassium, and calcium are the three major elements with highest variations among volcanic rocks. They are selected for use in two new diagrams confronting CaO/K2O ratio with K2O content (KCK diagrams). One diagram is designed for saturated (intermediate) rocks (quartz <5 vol.%) and the other for oversaturated (acid) volcanic rocks (quartz >5%). These diagrams are tested using compositions of volcanic rocks from Uatumã magmatism in the Amazon Craton and also by plotting compositions of rocks from type-localities and the world averages. The proposed limits between rock families agree with plotted rock compositions. The KCK diagrams are an alternative to existing diagrams to classify volcanic rocks.Academia Brasileira de Ciências2021-01-01info:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersiontext/htmlhttp://old.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652021000501103Anais da Academia Brasileira de Ciências v.93 n.3 2021reponame:Anais da Academia Brasileira de Ciências (Online)instname:Academia Brasileira de Ciências (ABC)instacron:ABC10.1590/0001-3765202120201202info:eu-repo/semantics/openAccessSANTOS,JOÃO O.S.HARTMANN,LÉO A.eng2021-07-15T00:00:00Zoai:scielo:S0001-37652021000501103Revistahttp://www.scielo.br/aabchttps://old.scielo.br/oai/scielo-oai.php||aabc@abc.org.br1678-26900001-3765opendoar:2021-07-15T00:00Anais da Academia Brasileira de Ciências (Online) - Academia Brasileira de Ciências (ABC)false |
dc.title.none.fl_str_mv |
Chemical classification of common volcanic rocks based on degree of silica saturation and CaO/K2O ratio |
title |
Chemical classification of common volcanic rocks based on degree of silica saturation and CaO/K2O ratio |
spellingShingle |
Chemical classification of common volcanic rocks based on degree of silica saturation and CaO/K2O ratio SANTOS,JOÃO O.S. Chemical classification volcanic rocks silica saturation Uatumã volcanism |
title_short |
Chemical classification of common volcanic rocks based on degree of silica saturation and CaO/K2O ratio |
title_full |
Chemical classification of common volcanic rocks based on degree of silica saturation and CaO/K2O ratio |
title_fullStr |
Chemical classification of common volcanic rocks based on degree of silica saturation and CaO/K2O ratio |
title_full_unstemmed |
Chemical classification of common volcanic rocks based on degree of silica saturation and CaO/K2O ratio |
title_sort |
Chemical classification of common volcanic rocks based on degree of silica saturation and CaO/K2O ratio |
author |
SANTOS,JOÃO O.S. |
author_facet |
SANTOS,JOÃO O.S. HARTMANN,LÉO A. |
author_role |
author |
author2 |
HARTMANN,LÉO A. |
author2_role |
author |
dc.contributor.author.fl_str_mv |
SANTOS,JOÃO O.S. HARTMANN,LÉO A. |
dc.subject.por.fl_str_mv |
Chemical classification volcanic rocks silica saturation Uatumã volcanism |
topic |
Chemical classification volcanic rocks silica saturation Uatumã volcanism |
description |
Abstract Modal classifications of common volcanic rocks are expensive, difficult, or impossible to attain. As a consequence, these rocks are classified using the chemical composition. However, existing classificatory diagrams are unable to identify all 16 families of common volcanic rocks; the most used is the total alkali-silica (TAS) diagram that identifies six families. Rocks not in the TAS diagram are misclassified with other rock names; their names are evolving to extinction, e.g. latite and rhyodacite. Some diagrams use Na2O, which is a complicating element rather than discriminant. Na2O is present both in alkali feldspar and plagioclase making difficult the separation of the amount associated to either feldspar. Silicon, potassium, and calcium are the three major elements with highest variations among volcanic rocks. They are selected for use in two new diagrams confronting CaO/K2O ratio with K2O content (KCK diagrams). One diagram is designed for saturated (intermediate) rocks (quartz <5 vol.%) and the other for oversaturated (acid) volcanic rocks (quartz >5%). These diagrams are tested using compositions of volcanic rocks from Uatumã magmatism in the Amazon Craton and also by plotting compositions of rocks from type-localities and the world averages. The proposed limits between rock families agree with plotted rock compositions. The KCK diagrams are an alternative to existing diagrams to classify volcanic rocks. |
publishDate |
2021 |
dc.date.none.fl_str_mv |
2021-01-01 |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/article |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
format |
article |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652021000501103 |
url |
http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652021000501103 |
dc.language.iso.fl_str_mv |
eng |
language |
eng |
dc.relation.none.fl_str_mv |
10.1590/0001-3765202120201202 |
dc.rights.driver.fl_str_mv |
info:eu-repo/semantics/openAccess |
eu_rights_str_mv |
openAccess |
dc.format.none.fl_str_mv |
text/html |
dc.publisher.none.fl_str_mv |
Academia Brasileira de Ciências |
publisher.none.fl_str_mv |
Academia Brasileira de Ciências |
dc.source.none.fl_str_mv |
Anais da Academia Brasileira de Ciências v.93 n.3 2021 reponame:Anais da Academia Brasileira de Ciências (Online) instname:Academia Brasileira de Ciências (ABC) instacron:ABC |
instname_str |
Academia Brasileira de Ciências (ABC) |
instacron_str |
ABC |
institution |
ABC |
reponame_str |
Anais da Academia Brasileira de Ciências (Online) |
collection |
Anais da Academia Brasileira de Ciências (Online) |
repository.name.fl_str_mv |
Anais da Academia Brasileira de Ciências (Online) - Academia Brasileira de Ciências (ABC) |
repository.mail.fl_str_mv |
||aabc@abc.org.br |
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1754302870473146368 |