Partition coefficients for rare earth elements in mafic minerals of high silica rhyolites: the importance of accessory mineral inclusions
Journal Article
·
· Geochim. Cosmochim. Acta; (United States)
REE concentrations of mafic mineral separates from high-silica rhyolites measured by INAA are high and variable compared to electron microprobe analyses of the minerals themselves. The mafic phases commonly contain inclusions or have adhering grains of accessory rare earth element (REE)-rich minerals. Optical and electron microscopic observation revealed discrete grains of chevkinite (rare earth titano-silicate) included within clinopyroxenes from the Sierra La Primavera (Mexico) rhyolite, and monazite grains adhering to ortho- and clinopyroxenes from the Bishop Tuff (California). During hand-picking of mineral separates, inclusions are only partly removed. As a result, the magnitude and variability of true mineral-melt partition coefficients for light REE have been overestimated. The true REE partition coefficients of La Primavera and Bishop Tuff pyroxenes obtained by microprobe are only slightly higher than they are in lower-silica rhyolites, and are not as variable as previously thought. The partitioning slope is positive, as in less silicic systems. The relative partitioning behavior of REE in high-silica rhyolites is dominated by crystal-chemical controls and not by liquid structural effects. When a partition coefficient is used for crystallization calculations, adhering phases and inclusions should be retained or the minor phases must be accounted for separately. Alternatively, a bulk distribution coefficient can be calculated using whole rock and glass compositions and the glass mode.
- Research Organization:
- Univ. of British Columbia, Vancouver (Canada)
- OSTI ID:
- 5100468
- Journal Information:
- Geochim. Cosmochim. Acta; (United States), Journal Name: Geochim. Cosmochim. Acta; (United States) Vol. 52:2; ISSN GCACA
- Country of Publication:
- United States
- Language:
- English
Similar Records
Pyroxene-high silica rhyolite trace element partition coefficients measured by ion microprobe
New and larger sanidine/melt partition coefficients for Ba and Sr as determined by ion microprobe analyses of melt inclusions and their sanidine host crystals
Compositional variations and equilibrium in REE, U and Th acceptor minerals during I-type granite differentiation, Palisade Crest suite, central Sierra Nevada batholith, California
Journal Article
·
Sat Jun 01 00:00:00 EDT 1991
· Geochimica et Cosmochimica Acta; (United States)
·
OSTI ID:5979271
New and larger sanidine/melt partition coefficients for Ba and Sr as determined by ion microprobe analyses of melt inclusions and their sanidine host crystals
Conference
·
Tue Dec 31 23:00:00 EST 1991
· Geological Society of America, Abstracts with Programs; (United States)
·
OSTI ID:6137429
Compositional variations and equilibrium in REE, U and Th acceptor minerals during I-type granite differentiation, Palisade Crest suite, central Sierra Nevada batholith, California
Conference
·
Mon Dec 31 23:00:00 EST 1984
· Geol. Soc. Am., Abstr. Programs; (United States)
·
OSTI ID:6379530
Related Subjects
58 GEOSCIENCES
580400* -- Geochemistry-- (-1989)
CALIFORNIA
CHEMICAL ANALYSIS
DEVELOPING COUNTRIES
ELECTRON MICROSCOPY
FEDERAL REGION IX
FUNCTIONS
IGNEOUS ROCKS
INCLUSIONS
LATIN AMERICA
MAGMA
MAGMATISM
MEXICO
MICROSCOPY
MINERALS
NORTH AMERICA
OPTICAL MICROSCOPY
OXYGEN COMPOUNDS
PARTITION FUNCTIONS
PYROXENES
QUANTITATIVE CHEMICAL ANALYSIS
RARE EARTH COMPOUNDS
RHYOLITES
ROCKS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
TUFF
USA
VOLCANIC ROCKS
580400* -- Geochemistry-- (-1989)
CALIFORNIA
CHEMICAL ANALYSIS
DEVELOPING COUNTRIES
ELECTRON MICROSCOPY
FEDERAL REGION IX
FUNCTIONS
IGNEOUS ROCKS
INCLUSIONS
LATIN AMERICA
MAGMA
MAGMATISM
MEXICO
MICROSCOPY
MINERALS
NORTH AMERICA
OPTICAL MICROSCOPY
OXYGEN COMPOUNDS
PARTITION FUNCTIONS
PYROXENES
QUANTITATIVE CHEMICAL ANALYSIS
RARE EARTH COMPOUNDS
RHYOLITES
ROCKS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
TUFF
USA
VOLCANIC ROCKS