Cumulate textures

Cumulate textures are rarely seen in porphyritic olivine spherules, but have received significant attention from the scientific community. They form when comparatively dense relict olivine crystals are pushed to the leading front of the spherule, where they serve as nuclei for new olivine growth. Consequently, the particle displays a transition from larger and compacted crystals at the leading front to smaller crystals at the far end. Additionally, the front of the particle is commonly flattened and rich in Fe-rich phases.

These textures have been interpreted as an indication of high orbital eccentricities and entry speeds. Additionally, oxygen isotopic analyses by Jonker et al. 2024 indicate a possible relation to an isotopically heavy source region that so far hasn’t been correlated to any known chondrite group. Cumulate spherules will therefore play an important role in studying the diversity of the cosmic dust flux to Earth. See also Genge et al. (2016).