Ptotal, {Mathematical expression} and the occurrence of cummingtonite in volcanic rocks
The phenocryst assemblage of cummingtonite, orthopyroxene, quartz, titanomagnetite and ilmenite in rhyolites of New Zealand has been used to calculate Ptotal and {Mathematical expression}. The values of Ptotal and {Mathematical expression} depend strongly upon whether an ideal mixing, or an ordered,...
| Main Authors: | , |
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| Format: | Journal article |
| Language: | English |
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Springer-Verlag
1973
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| _version_ | 1797100806211633152 |
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| author | Wood, B Carmichael, I |
| author_facet | Wood, B Carmichael, I |
| author_sort | Wood, B |
| collection | OXFORD |
| description | The phenocryst assemblage of cummingtonite, orthopyroxene, quartz, titanomagnetite and ilmenite in rhyolites of New Zealand has been used to calculate Ptotal and {Mathematical expression}. The values of Ptotal and {Mathematical expression} depend strongly upon whether an ideal mixing, or an ordered, model is used for the solid-solutions, but in both cases {Mathematical expression} ≈Ptotal. The rhyolite magma contained over 9 per cent water (by weight) when the cummingtonite phenocrysts precipitated, and possibly as much as 12 per cent, so that it is surprising that one of these rhyolites is a coherent lava. The calculated values of Ptotal and {Mathematical expression} are very sensitive to uncertainty in both the composition of the solid-solutions and temperature. Calculations show that {Mathematical expression}>0.7-0.8 Ptotal for cummingtonite to precipitate in rhyolites, and that iron-rich olivine and cummingtonite could only exist in rhyolites over a small temperature range at a pressure near 5 kilobars. Hornblende phenocrysts co-existing with fayalitic olivine in rhyolites accordingly have a very low activity of Mg7Si8O22(OH)2. © 1973 Springer-Verlag. |
| first_indexed | 2024-03-07T05:42:51Z |
| format | Journal article |
| id | oxford-uuid:e62d1a38-6f93-4d0a-b4d7-1bc2de8b04b0 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T05:42:51Z |
| publishDate | 1973 |
| publisher | Springer-Verlag |
| record_format | dspace |
| spelling | oxford-uuid:e62d1a38-6f93-4d0a-b4d7-1bc2de8b04b02022-03-27T10:29:21ZPtotal, {Mathematical expression} and the occurrence of cummingtonite in volcanic rocksJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:e62d1a38-6f93-4d0a-b4d7-1bc2de8b04b0EnglishSymplectic Elements at OxfordSpringer-Verlag1973Wood, BCarmichael, IThe phenocryst assemblage of cummingtonite, orthopyroxene, quartz, titanomagnetite and ilmenite in rhyolites of New Zealand has been used to calculate Ptotal and {Mathematical expression}. The values of Ptotal and {Mathematical expression} depend strongly upon whether an ideal mixing, or an ordered, model is used for the solid-solutions, but in both cases {Mathematical expression} ≈Ptotal. The rhyolite magma contained over 9 per cent water (by weight) when the cummingtonite phenocrysts precipitated, and possibly as much as 12 per cent, so that it is surprising that one of these rhyolites is a coherent lava. The calculated values of Ptotal and {Mathematical expression} are very sensitive to uncertainty in both the composition of the solid-solutions and temperature. Calculations show that {Mathematical expression}>0.7-0.8 Ptotal for cummingtonite to precipitate in rhyolites, and that iron-rich olivine and cummingtonite could only exist in rhyolites over a small temperature range at a pressure near 5 kilobars. Hornblende phenocrysts co-existing with fayalitic olivine in rhyolites accordingly have a very low activity of Mg7Si8O22(OH)2. © 1973 Springer-Verlag. |
| spellingShingle | Wood, B Carmichael, I Ptotal, {Mathematical expression} and the occurrence of cummingtonite in volcanic rocks |
| title | Ptotal, {Mathematical expression} and the occurrence of cummingtonite in volcanic rocks |
| title_full | Ptotal, {Mathematical expression} and the occurrence of cummingtonite in volcanic rocks |
| title_fullStr | Ptotal, {Mathematical expression} and the occurrence of cummingtonite in volcanic rocks |
| title_full_unstemmed | Ptotal, {Mathematical expression} and the occurrence of cummingtonite in volcanic rocks |
| title_short | Ptotal, {Mathematical expression} and the occurrence of cummingtonite in volcanic rocks |
| title_sort | ptotal mathematical expression and the occurrence of cummingtonite in volcanic rocks |
| work_keys_str_mv | AT woodb ptotalmathematicalexpressionandtheoccurrenceofcummingtoniteinvolcanicrocks AT carmichaeli ptotalmathematicalexpressionandtheoccurrenceofcummingtoniteinvolcanicrocks |