Gabbroic xenoliths in alkaline lavas in the region of Sanganguey Volcano, Nayarit, Mexico
Gabbroic xenoliths occur in alkaline cinder cones and lava flows erupted from vents along five parallel lines trending through the calc-alkaline volcano, Sanganguey in the northwestern portion of the Mexican Volcanic Belt. The xenoliths consist of varying proportions of olivine, clinopyroxene, orthopyroxene, and plagioclase. The complete lack of hydrous phases indicates that the gabbros crystallized under conditions of low PH/sub 2/O. Many xenoliths show textures indicative of a cumulate origin and others exhibit recrystallization indicative of subsolidus reactions prior to incorporation in the host liquids. Reaction between xenolithic minerals and host liquids are also observed. The range of Mg numbers calculated for liquids that would have been in equilibrium with olivines in the xenoliths suggests that these olivines crystallized from magmas such as those represented by either calc-alkaline basaltic andesites and andesites or the more evolved alkalic rocks which occur throughout the area. Crystal fractionation models show that the xenoliths may be related to such magmas. The fact that xenoliths occur most commonly in the alkaline rocks suggests that alkaline magmas rise to the surface more rapidly than the more chemically evolved calc-alkaline and alkaline magmas. Alternatively the lack of xenoliths in the more evolved magmas produced by high level crystal fractionation may indicate that the xenoliths are derived from zones below that from which the differentiated magmas begin their final ascent to the surface.
- Research Organization:
- Tulane Univ., New Orleans, LA (USA)
- OSTI ID:
- 6596723
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Vol. 17; ISSN GAAPB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
580300* -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
580400 -- Geochemistry-- (-1989)
CHEMICAL COMPOSITION
CHEMISTRY
CRYSTALLIZATION
DEVELOPING COUNTRIES
GABBROS
GEOCHEMISTRY
GEOLOGIC MODELS
IGNEOUS ROCKS
INCLUSIONS
LATIN AMERICA
LAVA
MAGMATISM
MEXICO
MINERALOGY
NORTH AMERICA
PETROGENESIS
PHASE TRANSFORMATIONS
PLUTONIC ROCKS
ROCKS
VOLCANOES