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Trace element and strontium isotope characteristics of volcanic rocks from Isla Tortuga: A young seamount in the Gulf of California

Rodey Batiza·K. Futa·C. E. Hedge
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Abstract

Isla Tortuga is a small isolated central volcano which is located near an actively spreading trough in the Gulf of California. The basalt lavas from Tortuga which have the highest Mg/Fe and Ni contents have trace element abundances and ratios and 87 Sr/ 86 Sr which are similar to those of mid-ocean ridge tholeiite. The major element, rare earth element and Sr abundances of fractionated tholeiite (low Mg/Fe) and tholeiitic andesite of Tortuga are consistent with an origin by closed-system fractional crystallization. This hypothesis is not supported by K, Na, Rb and Ba abundances in the lavas nor by their variable 87 Sr/ 86 Sr (0.7024–0.7035). It is proposed that the apparent decoupling of light rare earth elements, other incompatible trace elements and 87 Sr/ 86 Sr is due to contamination of some Tortuga magmas while they are fractionated in a high-level crustal magma chamber. The mantle source of least-contaminated, high Mg/Fe basalt lavas of Tortuga is similar, although not identical to the source of normal mid-ocean ridge tholeiite; significant differences exist. The reasons for these differences are not yet known.

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Rodey Batiza, K. Futa, C. E. Hedge. 1979. Trace element and strontium isotope characteristics of volcanic rocks from Isla Tortuga: A young seamount in the Gulf of California. https://doi.org/10.1016/0012-821x(79)90211-5

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