Titanium isotope heterogeneity in the Earth’s mantle: A case study of the Horoman peridotite massif

Titanium isotopes are a promising novel tracer for magmatic processes. The Ti isotope composition of the Earth's mantle is key using this on planetary scale, however, recent studies point to potential variations in rocks. This study presents stable data well-characterised peridotites from Horoman massif (Japan) as well primitive, orogenic (Variscan and Alpine belts) South African ultrapotassic originate continuous section across layered peridotite body comprise highly depleted harzburgites fertile lherzolites metasomatically overprinted peridotites. Unlike most primitive mantle-derived magmas, which display very limited variations, δ49Ti (deviation 49Ti/47Ti OL-Ti standard) values vary –1.523 ± 0.029 0.547 0.015‰ (2SD), spanning total range 2.07‰. Heavy, continental crust-like compositions correlated with Nb/Th likely related metasomatism wedge above Hidaka subduction zone. In such scenario, isotopically heavy was inherited subducted terrigenous sediments might have been further enhanced by fractionation during mobilisation slab. Significant differences between coexisting clino- orthopyroxene (Δ49Tiopx-cpx = 0.16–0.29‰) notably light (δ49Ti −1.523 −0.677 0.036‰, 2SD) recorded refractory be kinetic diffusion-driven fluid/melt percolation. analysed rocks distinctly high (0.114 0.040 0.290 0.030‰, compared majority magmas. observed enrichment originates recycled material characterised δ49Ti, line their derivation strongly metasomatised sources. Our results demonstrate presence significant small-scale heterogeneity within upper mantle.