Variations in trace element partition coefficients in sanidine in the Cerro Toledo Rhyolite, Jemez Mountains, New Mexico: Effects of composition, temperature, and volatiles

Journal Article · Mon Oct 01 00:00:00 EDT 1990 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(90)90005-6· OSTI ID:5997394

Stix, J ^[1]; Gorton, M P ^[2]

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1. Universite de Montreal, Quebec (Canada)
2. Univ. of Toronto, Ontario (Canada)

Trace element partition coefficients have been measured for one plagioclase and five sanidine mineral separates from the Cerro Toledo Rhyolite, New Mexico. Sanidine partition coefficients vary substantially and systematically within the Cerro Toledo Rhyolite. Partition coefficients for Ca, Sr, Zn, La, and Eu are lowest in the most evolved rhyolites, whereas Sm and HREE partition coefficients are highest. Rubidium partition coefficients remain constant, while those for Ba, Ce, and Th are variable. Variations of the Sr, Zn, La, and Eu partition coefficients are correlated with the Ca contents and partition coefficients of the sanidines. Calcium may have controlled the distribution of these elements in the sanidine by modifying the feldspar structure. The low Ca partition coefficients in sanidines for the most evolved rhyolites may be the consequence of modification of the melt structure, possibly due to increased volatile contents at the top of the magma chamber(s) during evolution of the Cerro Toledo Rhyolite. The Zn and La partition coefficients between sanidine and melt also may have been controlled by this change in melt structure. Modelling using major elements and the constant Rb partition coefficient for sanidine indicates 70% crystallization of magma during Cerro Toledo Rhyolite time by removal of 68% sanidine and 32% quartz. Estimates of the volume (1) of initial parental magma and (2) of the magma that crystallized during this period are 11,670 km{sup 3} and 8,170 km{sup 3}, respectively. The average intrusion rate of silicic magma during Cerro Toledo Rhyolite activity was 35 {times} 10{sup {minus}3} km{sup 3}/a.

• OSTI ID: 5997394
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 54:10; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
CHEMICAL COMPOSITION
CHEMISTRY
CRYSTALLIZATION
FEDERAL REGION VI
FELDSPARS
GEOCHEMISTRY
IGNEOUS ROCKS
MAGMATISM
MATTER
MINERALOGY
MINERALS
NEW MEXICO
NORTH AMERICA
PETROCHEMISTRY
PETROGENESIS
PHASE TRANSFORMATIONS
RHYOLITES
ROCKS
USA
VOLATILE MATTER
VOLCANIC ROCKS