Rapid cooling of planetesimal core-mantle reaction zones from Mn-Cr isotopes in pallasites

Pallasite meteorites, which consist of olivine-metal mixtures and accessory phosphates crystallised from silico-phosphate melts, are thought to represent core-mantle reaction zones of early differentiating planetesimals. Pallasite meteorites can be linked to five distinct planetesimals, indicating that they are default products of differentiation. However, their formation modes (deep, shallow, and impact environments) and age are still elusive. We have investigated the trace element and Mn-Cr isotopic signatures of Main-Group pallasite olivine, finding enhanced Mn, P and Cr/Cr near crystal rims which indicates early ingrowth of radiogenic Cr in silico-phosphate melts. Mn-Cr isotopic data corroborate previous Hf-W isotopic data, indicating an early metal-silicate separation event but additionally that rapid cooling generated silico-phosphate eutectic melts with high Mn/Cr within ∼2.5 to 4 Myr of Solar System formation. These melts formed before most known samples of planetesimal crusts (eucrite and angrite meteorites) and are among the earliest evolved planetary silicates. Additionally, Mn-rich phosphates in other, non-Main-Group pallasite meteorites suggest that core-mantle reaction zones are generic, datable features of differentiation.

• Publication year

  2016

• Venue

  Unknown venue

• Publication date

  Unknown publication date

• Fields of study

  Environmental Science, Geology

• Identifiers
  DOI 10.7185/GEOCHEMLET.1607
• External record

  Open on Semantic Scholar

• Source metadata

  Semantic Scholar

• No claims are published for this paper.

• No concepts are published for this paper.

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