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Figure 14-1.After Crough (1983) Ann.Rev. Earth Planet. Sci., 11, 165-193.

This map shows important hot spots and hot spot tracks over the world.

Note that many tracks have kinks, indicating changing plate motions.

Ocean Intraplate Volcanism

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Types of OIB Magmas

Two principal magma series:

Tholeiitic series (dominant type), parental to ocean island tholeiitic

basalt, or OIT. This magma is similar to MORB, but with some distinct

chemical and mineralogical differences.

Alkaline series (subordinate), parental to ocean island alkaline basalt,

or OIA.

There are two principal alkaline sub-series:

Silica undersaturated sub-series (more common).

Slightly silica oversaturated sub-series (less common).

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Magma evolution in the oceanic island lava series

After Wilson, 1989, Igneous

Petrogenesis. Kluwer.

Strongly alkaline

Mildly alkalineTholeiitic

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Alkalinity of oceanic island lavasAlkalinity is highly variable among various oceanic islands. Alkalis are

incompatible and little affected by

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Spider diagrams

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Simple Mixing Models

Winter, 2001, An

Introduction to Igneous and

Metamorphic Petrology.Prentice Hall.

Binary mixing

All analyses fall along a line

between two end members assource regions or magmas mix.

Ternary mixing

All analyses fall within a triangle

of three end members as sourceregions or magmas mix.

A d l f i i

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Cartoon illustrating a conceptual model for the origin of various ocean

magmas, and the mantle reservoirs from which they ultimately come.

Nomenclature from Zindler and Hart, 1986, After Wilson, 1989, and Rollinson, 1993.

Depletedmantle

E

nriched

mantle

A model for oceanic magmatism

Continentalreservoirs