Details

Autor(en) / Beteiligte

• REVILLON, S
• Arndt, N T
• Chauvel, C
• Hallot, E

Titel

Geochemical Study of Ultramafic Volcanic and Plutonic Rocks from Gorgona Island, Colombia: the Plumbing System of an Oceanic Plateau

Ist Teil von

• Journal of petrology, 2000-07, Vol.41 (7), p.1127-1153

Ort / Verlag

Oxford: Oxford Publishing Limited(England)

Erscheinungsjahr

2000

Link zum Volltext

Quelle

Free E-Journal (出版社公開部分のみ）

Beschreibungen/Notizen

•   The only known post-Archaean komatiites are found on Gorgona, a small island off the Colombian coast that forms part of the Caribbean oceanic plateau. Mafic and ultramafic intrusions are located in the interior of the island. To establish the relationship between intrusive and extrusive phases of ultramafic magmatism, and to help understand how an oceanic plateau is constructed, we undertook the first petrological and geochemical study of the intrusive rocks. Rare earth element patterns in gabbros range from almost flat to moderately depleted; in dunites and wehrlites, the depletion is more pronounced. These patterns fall midway in the range measured in Gorgona volcanics, whose compositions vary from slightly enriched to extremely depleted. Nd isotope compositions indicate two distinct mantle sources, one highly depleted, the other less depleted. MgO contents of parental liquids are estimated from olivine compositions at 20-25 % in ultramafic lavas, and 12-13% in the intrusives. Petrographic observations and similarities in trace-element contents indicate that the two magma types are comagmatic, related through olivine fractionation. Modelling of major and trace elements indicates that the primary ultramafic magmas formed by advanced critical melting at high pressure in a rising mantle plume. The plumbing system that fed the Gorgona plateau was complex, being characterized by a series of magma chambers at different crustal levels. Mantle-derived ultramafic liquids either travelled directly to the surface to erupt as komatiite flows, or were trapped in magma chambers where they differentiated into basaltic liquid and mafic to ultramafic cumulates. Gorgona gabbros and peridotites formed in shallow-level examples of these intrusions.