Periodic Reporting for period 4 - INFANT EARTH (The Making of the Earth – Reading the Geochemical Code from Meteorites and the Earth’s Oldest Rocks)
Período documentado: 2020-03-01 hasta 2021-08-31
We could show that Earth formed from inner solar system building blocks that are not present in our meteorite collections anymore. So called siderophile (i.e. metal loving) elements in Earth’s mantle are in part pristine and are not entirely derived from the so called late veneer, the last ca. 0.5 percent of meteorite material that were delivered to Earth after formation of its metal core ceased. A study on Apollo samples from the Moon revised the formation age of the Moon to ca. 40-60 million years after solar system formation, significantly earlier than previously thought. The age also implies that the Earth-Moon system was more or less formed by ca. 60 million years after solar system formation, i.e. by 4.50 billion years ago. We could show that so called volatile elements (i.e. elements with condensation temperatures of less than ca. 800°K in space) on Earth and in some primitive meteorites display a characteristic hockeystick-like pattern, now unambiguously showing that the final 10-15 percent of meteoritic material that was delivered to the Earth had a composition similar to the CI or CM groups of carbonaceous chondrites that originate from the more outer parts of the solar system. The results of this study also allow much improved estimates of volatile element abundances in Earth’s hidden metal core. We could also show that the deficit of the rare element Niobium in Earth’s silicate mantle is likely a vestige of Earth’s early history and was inherited from Earth’s building blocks. The Niobium in Earth’s mantle has therefore been lost to asteroidal cores. Isotope measurements in Earths oldest rocks from Greenland, Australia and South Africa could show that Earth’s upper silicate mantle has lost much more basaltic melts by this time than previously thought.
1) The first sufficiently precise Ru isotope measurements in terrestrial rocks - Fische Gödde et al. 2020
2) Volatile element measurements in meteorites at unprecedented accuracy - Braukmüller et al. 2019
3) Some of the first Stable W isotope measurements in geological materials - Kurzweil et al. 2019,2020
4) A revised age for formation of the Moon – Thiemens et al. 2019
5) The first high precision measurements of high field strength elements in differentiated meteorites - Münker et al. 2017
6) Firm evidence for an early depleted mantle from Hf-Nd-Ce isotopes in rocks from the Pilbara craton - Hasenstab et al. 2021