Cocos Plate Seamounts offshore NW Costa Rica and SW Nicaragua: Implications for large-scale distribution of Galápagos plume material in the upper mantle

Abstract

The origin of intraplate volcanism not directly part of a hotspot track, such as

A 1.5 Ma record of plume-ridge interaction at the Western Galápagos Spreading Center (91°40′–92°00′W)

“…An extended description of the sample treatment and analytical procedures, along with data tables for major and trace element reference material, are presented in Herbrich et al (2015) and summarized below. A correlated table with all data and sample coordinates is provided in Table A1.…”

Episodic intraplate magmatism fed by a long-lived melt channel of distal plume origin

“…In addition, the EPR-generated Cocos Plate is speckled with seamounts, and several dated seamounts were formed between 19 and 7 million years (Ma) ago yet are 2 to 13 Ma younger than plate age (Fig. 2, A and B) ( 20 ). Despite being several hundreds of kilometers from the surface expression of the Galápagos Plume, the major and trace element and the isotopic signatures of these intraplate seamounts require a multisource mixture containing variable proportions of an enriched component with a chemistry similar to that of the Northern Galápagos Domain and two depleted components, mid-ocean ridge basalt (MORB) mantle and depleted Galápagos Plume material ( 20 ).…”

“…2, A and B) ( 20 ). Despite being several hundreds of kilometers from the surface expression of the Galápagos Plume, the major and trace element and the isotopic signatures of these intraplate seamounts require a multisource mixture containing variable proportions of an enriched component with a chemistry similar to that of the Northern Galápagos Domain and two depleted components, mid-ocean ridge basalt (MORB) mantle and depleted Galápagos Plume material ( 20 ). The erupted products responsible for the formation of the intraplate seamounts indicate silica-saturated to slightly undersaturated melts sourced from spinel peridotites (<60 km), consistent with shallow melting beneath young (<25 Ma) and thin Cocos Plate lithosphere ( 20 ).…”

“…However, unlike the intraplate seamounts, the sills require an enriched component resembling the Southern Galápagos Domain ( 26 ). Figure 3 shows the Pb-Nd isotopic ratios of the Site 1039 sill samples and select intraplate seamounts ( 20 , 26 ).…”

“…( B ) 206 Pb/ 204 Pb versus 143 Nd/ 144 Nd. Triangles show intraplate seamount [from( 20 )]; squares show Site 1039 sill [from( 26 )], and yellow circle shows depleted MORB mantle [from( 17 )]. The Galápagos chemical domains are derived from ( 20 ).…”