Geochemical characteristics of volcanic rocks from Conrad Rise, southern Indian Ocean: Insights into the origin of the plateaux at the Indian Ocean

Abstract

Conrad Rise is one of the plateaux in the Indian Ocean. We recovered igneous rocks: massive lava, porous lava, and volcanic breccia. They are mostly alkali rocks, and lesser amounts of sub-alkali rock were recovered. They have similar trace element compositions to igneous rocks from seamounts and plateaux in the Indian Ocean, while trace element and isotopic ratios are different from Marion, Crozet, and Kerguelen volcanic rocks. Instead, they have similar trace element and isotopic ratios to Madagascar and Afanasy-Nikitin rocks. Tectonic reconstruction reveals that Conrad Rise, Del Cano Rise, and Madagascar Plateau had formed one massive edifice. Therefore, Conrad Rise, Del Cano Rise, Madagascar Plateau, and Afanasy-Nikitin Rise have a common origin, because Afanasy-Nikitin Rise was located near the edifices at that time.