Andrea Mundl-Petermeier and Sebastian Viehmann of the University of Vienna’s Department of Lithospheric Research have demonstrated that a new geochemical archive 182Tungsten in banded iron formations can be used to simultaneously trace both the evolution of the Earth’s mantle and continents throughout Earth’s history, according to a study published in the journal Nature Communications. This opens up new possibilities for future research into the Precambrian Earth.
The short-lived 182Hafnium-182Tungsten isotope system has previously been studied to learn more about how the Earth’s mantle developed during the early Earth period: 182Tungsten shows, among other things, how much the Earth was exposed to violent meteorite strikes near the end of its formation and how quickly the Earth’s mantle mixed and homogenized with these meteoritic components over time.
However, until today, these isotopes had to be investigated in magmatic rocks from various, but extremely limited relicts of former continents, such as Australia or South Africa.
Andrea Mundl-Petermeier and Sebastian Viehmann of the University of Vienna’s Department of Lithospheric Research, along with colleagues from the University of Cologne and Jacobs University Bremen, have discovered a new geochemical archive, which they published in the journal Nature Communications: tungsten isotope signatures in banded iron formations (BIFs), which formed primarily in the Precambrian, between 3.8 billion and 540 million years ago.
With the help of high-precision measurement methods, we were able to resolve small but distinct differences in 182W of individual layers.
Andrea Mundl-Petermeier
Evolution of the Earth’s mantle and the continents
The team was able to reconstruct that iron- and silica-rich layers deposited from seawater can simultaneously record the evolution of the Earth’s mantle and crust using a 2.7 billion-year-old iron formation from the Temagami greenstone belt in Canada.
The research team obtained high-precision isotope measurements of individual bright quarz and dark iron layers using state-of-the-art instruments from the GeoCosmoChronology group and the new Geoscience Solid State Mass Spectrometry (GeoIsotopes) Core Facility at the Department of Lithospheric Research.
“With the help of high-precision measurement methods, we were able to resolve small but distinct differences in 182W of individual layers,” says Andrea Mundl-Petermeier from the Department of Lithospheric Research.
Banded iron ores are created by chemical deposition from the ocean, and the new approach now addresses long-standing problems about mantle and crust formation from a seawater perspective.
“The BIFs studied from the Temagami area thus directly represent seawater chemistry 2.7 billion years ago,” explains geologist Sebastian Viehmann: “We are looking at the Earth at that time from the perspective of the ocean.”
