Geology and Petrology of the Galápagos Islands

McBirney, Alexander R.; Williams, Howel

doi:10.1130/mem118-p1

Cited by 204 publications

(167 citation statements)

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“…The Galapagos Islands are not a likely source for the layers studied here, because differentiated rocks are very rare and of quartz-trachytic composition (McBirney and Williams, 1969). Moreover, the ash layers should have been deposited westwards of their eruptive source, owing to the prevailing easterly high-altitude wind direc- tions (Ninkovich and Shackleton, 1975).…”

Section: Discussionmentioning

confidence: 92%

Rhyolitic and Basaltic Ashes from the Galapagos Mounds Area, Leg 70, Deep Sea Drilling Project

Schmincke¹

1983

Initial Reports of the Deep Sea Drilling Project

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Ashes occurring both as distinct layers and mixed with pelagic sediments of the hydrothermal mounds lying south of the Galapagos Rift are mainly rhyolitic and basaltic. The ashes, of rhyolitic to intermediate composition, appear to belong to a calc-alkalic series and were probably derived from Plinian eruptions in Ecuador or Colombia. Basaltic ashes are made of nonvesicular sideromelane spalling shards and are of tholeiitic composition. They probably were derived locally from fault scarps. Most rhyolitic and basaltic glass shards studied are fresh except for hydration of the rhyolitic shards. Some shards are severely altered, however. Basaltic ash may be more common in pelagic sediments deposited near accretion zones and may be a source of silica and other elements released during diagenesis.

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Section: Discussionmentioning

confidence: 92%

Rhyolitic and Basaltic Ashes from the Galapagos Mounds Area, Leg 70, Deep Sea Drilling Project

Schmincke¹

1983

Initial Reports of the Deep Sea Drilling Project

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“…The petrology of the Galápagos Islands in general has been studied by McBirney and Ken-ichiro Aoki (1966). They concluded that the lavas are tholeiitic, grading into alkaline basalts.…”

Section: The Physical Environmentmentioning

confidence: 99%

Soils and Paleosoils of the Galápagos Islands: What We Know and What We Don't Know, A Meta-Analysis

Stoops

2014

Pacific Science

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Accessible information on Galápagos soils is very limited. Much of the existing, although still scarce, information is several decades old and not easily retrieved. The aim of this paper is to present a critical synthesis. Three local soilforming factors (parent material, climate, and vegetation) are briefly highlighted, followed by a more detailed discussion of the hypsometric soil sequence on Santa Cruz, the only island where systematic information was recorded by a Belgian geopedological mission in 1962. Five zones are distinguished from the coast toward the top of the island: a dry coastal area, containing superficial and interstitial reddish, smectite-bearing soils between basalt blocks; a transition zone of brown, also smectite-bearing soils; and three subsequent higher zones covered by deeper, brown soils with probably andosolic characteristics. Trace element analyses point to a uniform composition of the parent material and a more progressed weathering on the higher slopes. Micromorphological characteristics of the soils are discussed. Soils of Santa Fé are comparable with those of the coastal zone of Santa Cruz but show higher amounts of P and S, probably of avian origin. Deeper, reddish clayey soils cover San Cristóbal and are at least partly preHolocene. On the younger islands, no soils seem to be present.

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“…It is obvious that the ongoing processes of magmatic evolution which occur near the East Pacific Rise (Batiza et al, 1977) may cause these "incompatible" metals to become residually concentrated in highly differentiated basalts or released into a coexisting brine during crystallization of the basalt. Additionally, McBirney and Williams (1969) have shown that these trace constituents could be concentrated by magmatic hybridization of a tholeiitic basalt. The alkaline basalts and other effusive rocks described from the Galapagos Islands (McBirney and Williams, 1969) in several cases are significantly enriched in Co, Ni, and Cu over the relatively more primitive basalts in the vicinity.…”

Section: Co-ni-cu Sulfide Veinsmentioning

confidence: 99%

“…Additionally, McBirney and Williams (1969) have shown that these trace constituents could be concentrated by magmatic hybridization of a tholeiitic basalt. The alkaline basalts and other effusive rocks described from the Galapagos Islands (McBirney and Williams, 1969) in several cases are significantly enriched in Co, Ni, and Cu over the relatively more primitive basalts in the vicinity.…”

Section: Co-ni-cu Sulfide Veinsmentioning

confidence: 99%

Mineralogy and Geochemistry of Ore Minerals from Basalts Related to Spreading Centers of the Eastern Pacific with Speculations on Ore-Forming Processes

Schrader¹,

Furbish²

1980

Initial Reports of the Deep Sea Drilling Project

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Two opaque phases, Ti-magnetite and pyrite, are ubiquitous in the basalts retrieved from the eastern Pacific on DSDP Leg 54. Additional, but minor, phases observed in reflected light include pyrrhotite, chalcopyrite, ilmenite, hematite, goethite, spinel, and amorphous manganese oxides.The dominant mode of occurrence for the Ti-magnetite and all sulfide phases is as grains, crystals, or spheres enclosed in basalt glass or interstitial to crystalline silicates. Ti-magnetites are present mainly as skeletal crystals whose grain size appears directly proportional to the degree of undercooling of the lava. The sulfides occur generally as monomineralic or polymineralic spheres apparently separated immiscibly from the silicate melt. Sulfide veining and replacement of silicates and primary oxides takes place in several samples and suggests a secondary (e.g., hydrothermal) period of ore mineral deposition. The veins are dominantly pyrite, with very minor chalcopyrite and/or pyrrhotite in a few cases.The samples studied and published research results support the concept of spreading centers as loci for certain types of metallogenesis. Ore bodies related to divergent plate margins may include massive sulfides, stratiform complexes, and hydrothermal manganese oxide deposits, all of which are related to the types of magmatic and secondary processes which affected the basalts recovered on Leg 54.

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Geology and Petrology of the Galápagos Islands

Cited by 204 publications

References 0 publications

Rhyolitic and Basaltic Ashes from the Galapagos Mounds Area, Leg 70, Deep Sea Drilling Project

Rhyolitic and Basaltic Ashes from the Galapagos Mounds Area, Leg 70, Deep Sea Drilling Project

Soils and Paleosoils of the Galápagos Islands: What We Know and What We Don't Know, A Meta-Analysis

Mineralogy and Geochemistry of Ore Minerals from Basalts Related to Spreading Centers of the Eastern Pacific with Speculations on Ore-Forming Processes

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