Geology and petrogeneses of the lavas of Floreana and Santa Cruz Islands: Galapagos Archipelago

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 1979

OSTI ID:5473189

Bow, C S

Floreana is a mature shield volcano situated on the southern boundary scarp of the Galapagos Platform. On the basis of petrographic and geochemical criteria, Floreana lavas are divisible into two distinct volcanic series: Main Series: Fine-grained, alkalic basanitoids constitute the majority of shield-building flows. Flank Series: Isolated parasitic shields on the southeastern flank of the central volcano erupted olivine and plagioclase phyric, alkali-poor basanitoid lavas during the waning stages of volcanism. A spectrum of theoretical models was applied to the Floreana suite in an attempt to account for observed major and trace element variations. The complex tectonic history and chemical diversity of volcanism on Santa Cruz contrasts with the relative brevity and compositional uniformity of volcanism on Floreana. Two major time-stratigraphic units are defined for Santa Cruz lavas. Platform Series: Lavas are dominantly olivine tholeiites and ferrobasalts with little compositional diversity; subsidiary low-K/sub 2/O ridge type basalts and basanitoid lavas have affinities with younger, Shield Series rocks. Lavas associated with this most recent phase of Santa Cruz volcanism include basanitoids (alkali-olivine basalts), hawaiites, low-K/sub 2/O basalts, and flows with compositions intermediate between basanitoid and low-K/sub 2/O types. The results of petrogenetic modeling for Floreana and Santa Cruz imply significant lateral variations in mantle trace element abundances, depth, and extent of partial melting and volcanic plumbing systems. These patterns are reflected to varying extents by other volcano-tectonic provinces and may be consequences of the thermal evolution of mantle melting anomalies.

• Research Organization: Oregon Univ., Eugene (USA)
• OSTI ID: 5473189
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580202* -- Geophysics-- Volcanology-- (1980-1989)
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
ANORTHOSITES
BASALT
CHALCOGENIDES
CHROMIUM
EARTH CRUST
EARTH MANTLE
ELEMENTS
GABBROS
GEOLOGY
IGNEOUS ROCKS
IRON COMPOUNDS
IRON SILICATES
LAVA
MAGNESIUM COMPOUNDS
MAGNESIUM SILICATES
METALS
MINERALS
NICKEL
OLIVINE
ORIGIN
OXIDES
OXYGEN COMPOUNDS
PETROGENESIS
PLUTONIC ROCKS
POTASSIUM COMPOUNDS
POTASSIUM OXIDES
RARE EARTH COMPOUNDS
ROCKS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
STRATIGRAPHY
TECTONICS
TRACE AMOUNTS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
VOLCANIC ROCKS
VOLCANOES