Out-of-sequence skeletal growth causing oscillatory zoning in arc olivines.

ABSTRACT: Primitive olivines from the monogenetic cones Los Hornitos, Central-South Andes, preserve dendritic, skeletal, and polyhedral growth textures. Consecutive stages of textural maturation occur along compositional gradients where high Fo-Ni cores of polyhedral olivines (Fo_92.5, Ni ~3500 ppm) contrast with the composition of dendritic olivines (Fo < 91.5, Ni < 3000 ppm), indicating sequential nucleation. Here we present a new growth model for oscillatory Fo-Ni olivine zoning that contrasts with the standard interpretation of continuous, sequential core-to-rim growth. Olivine grows rapidly via concentric addition of open-structured crystal frames, leaving behind compositional boundary layers that subsequently fill-in with Fo-Ni-depleted olivine, causing reversals. Elemental diffusion

SUBMITTER: Salas P 

PROVIDER: S-EPMC8249515 | biostudies-literature | 2021 Jul

REPOSITORIES: biostudies-literature