Constraints on age and construction process of the Foundation chain submarine volcanoes from magnetic modeling

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• 作者：Maia ; Marcia ; Dyment ; J??r??me ; Jouannetaud ; David
• 刊名：Earth and Planetary Science Letters
• 出版年：2005
• 出版时间：June 30, 2005
• 年：2005
• 卷：235
• 期：1-2
• 页码：183-199
• 全文大小：2.10 M

文摘

The interaction between the Foundation hotspot and the Pacific–Antarctic Ridge (South Pacific) is one of the two known cases where a ridge is approaching a hotspot. This ridge–hotspot relative movement results in a change in the morphology of the volcanoes along the chain as the age of the lithosphere at the time of edifice formation progressively diminishes. Four hundred kilometers west of the Pacific–Antarctic Ridge axis, volcanism is distributed along two sub-parallel lines of volcanoes, separated by distances diminishing from 100 km at the west to 50 km near the axis of the ridge. The magnetic anomalies mapped on this part of the chain show a pattern clearly dominated by the magnetic signature of the seamounts. The anomalies were forward modeled using a remanent magnetization of normal or reversed polarity within the volcano topography. The resulting pattern of normal and reversed magnetization is consistent with the intervals of the geomagnetic polarity time scale for the last 5 Ma, the age of the oldest studied volcano. These magnetic anomalies therefore represent an independent means of dating the volcanic edifices. The ages deduced from the modeling are consistent with the hypothesis of volcanoes built by a hotspot on the fast moving Pacific plate and are in good agreement with the published radiometric dates, although these dates tend to correspond to the late constructional stages of the edifices. The differences between magnetic and radiometric ages suggest that the average time span to build a volcano of the Foundation chain is about 1 million years, in agreement with other intraplate edifices. The difference between the magnetic ages of the seamounts and of the underlying crust, both deduced from the magnetic anomaly analysis, show that the ridge has approached the hotspot at a rate of 40 km/Ma.