Lower-mantle iron heterogeneity constrained by the electrical conductivity of Al-bearing bridgmanite

Map showing global iron content distribution in the lower mantle at 1225 kilometres depth with LLSVP boundaries outlined.

Scientists measured how well iron-bearing bridgmanite, the main mineral in Earth’s lower mantle, conducts electricity under high pressure and temperature conditions. They found conductivity rises sharply with iron content but barely changes with temperature, allowing iron variations to be mapped directly from global conductivity models derived from geomagnetic data. The results suggest iron-rich material within … Read more…

Granitic intrusions enhance strain localization and rapid mantle exhumation along an oceanic detachment fault

Map of the Tyrrhenian Sea showing IODP Expedition 402 drill sites with core photos and lithology logs.

Scientists drilling into the Tyrrhenian Sea seafloor as part of the International Ocean Discovery Program recovered rock cores showing granite intrusions mixed with peridotite along an ancient detachment fault. Dating and chemical analysis show the granites formed about 4 million years ago some 7 to 9 kilometres down, then were rapidly brought to the seafloor … Read more…

Thickness of an extensional plate-boundary shear zone in the mantle: Implications for tectonic controls on strain localization and transient strain rates

This study shows that constant displacement rate conditions – imposed by plate tectonics – is the best approach to consider the evolution of extensional plate-boundary shear zones, as stresses vary during deformation. The Turon de Técouère massif of the French Pyrenees preserves a Cretaceous, magma-poor hyperextended plate margin within the lithospheric mantle. The massif exposes an extensional … Read more…

Heterogeneous Earth’s mantle drilled at an embryonic ocean

Mantle processes control plate tectonics and exert an influence on biogeo- chemical cycles. However, the proportion of mantle sampled in-situ is minimal, as it is buried beneath igneous crust and sediments. Here we report the lithological characteristics of two mantle sections from an embryonic ocean drilled by the International Ocean Discovery Program (IODP) in the … Read more…