Metasomatic PGE mobilization by carbonatitic melt in the mantle: Evidence from sub-μm-scale sulfide–carbonaceous glass inclusion in Tahitian harzburgite xenolith

Highly siderophile elements mobility in the subcontinental lithospheric mantle beneath southern Patagonia

“…Thus, Cpx4 is enriched in Na 2 O and characterised by a very high Cr 2 O 3 and Mg# and low TiO 2 content, and exhibit a high LREE enrichment, (La/Yb) n , (Zr/Hf) n and low (Ti/Eu) n , similar to clinopyroxene that typically crystallise from carbonatite-like melts (Fig. 6E, F) (e.g., Akizawa et al, 2017). In contrast, Cpx5 exhibits a similar minor and trace element distribution to Cpx4 (Fig.…”

“…Thus, a wide range of metasomatic agents have been proposed to explain the very different HSE systematics in SCLM peridotites (e.g., Lorand et al, 2013;Luguet et al, 2015). These include S-undersaturated OIB-like melts (Lorand et al, 2004;Saunders et al, 2016), volatile-rich silicate melts exsolved after percolation and reaction with the peridotite wall-rock or S-saturated melts (e.g., Grégoire et al, 1997;Moine et al, 2004); CO 2 -rich (i.e., carbonatite-like) melts (Akizawa et al, 2017;Saunders et al, 2015), and fluids derived from subduction zones (McInnes et al, 1999;Widom et al, 2003). Percolation of S-undersaturated melts usually removes BMS from the mantle and dilutes the whole-rock HSE concentrations in the peridotite whereas infiltration of S-saturated melts has the opposite effect producing the precipitation of Cu-Ni-rich sulphides (see Fig.…”

“…Despite these advances, there are significant gaps in knowledge that limit our understanding of the impact of metasomatism on HSE mobility. Particularly it is still debatable the effects that CO 2 -rich melts have in mobilizing HSE in the SCLM (Akizawa et al, 2017;Hughes et al, 2017;Saunders et al, 2015).…”

Crustal anorthosite formation by deep‐seated hydrothermal circulation beneath fast‐spreading axis: Constraints from chronological approach, Sr isotope, and fluid–chromite inclusion investigation

“…A micrometer-scale thin sample foil including the brown mineral inclusion was prepared using the FIB-SEM system described above. Refer to Akizawa et al (2017Akizawa et al ( , 2020 for detailed procedure of the sample extraction from the thin section. The thin sample foil was examined to identify mineral phase using a JEOL JEM-2100F transmission electron microscope system equipped with a Schottky field-emission gun (FE-TEM) system at Kyoto University.…”

Fe-Ti-Zr metasomatism in the oceanic mantle due to extreme differentiation of tholeiitic melts (Moa-Baracoa ophiolite, Cuba)

“…To date, most efforts in understanding mantle metasomatism have been focused on the study of ultramafic xenoliths and exhumed ultramafic massifs that have sampled the subcontinental lithospheric mantle (SCLM) underlying cratonic and off-craton regions of the Earth (Bodinier et al, 2008;Coltorti et al, 2004;Le Roux et al, 2007;Lenoir et al, 2001; Soustelle et al, 2009). In the SCLM, these three styles of metasomatism are very well preserved and have been identified to originate via a variety of metasomatic agents, including supercritical fluids and a variety of silicate liquids including silica-saturated, high-Na and high-K alkaline basaltic, as well as kimberlitic and carbonatitic compositions (e.g., Bodinier et al, 1990;Ionov et al, 1999;Coltorti et al, 1999Coltorti et al, , 2000Greégoire et al, 2000;Laurora et al, 2001;Dawson, 2002;Lorand et al, 2004;Scamberulli et al, 2009;González-Jiménez et al, 2014a;Akizawa et al, 2017;Tassara et al, 2018). However, modal metasomatism is relatively underexplored in the mantle rocks of "normal oceanic lithosphere", as numerous studies focused on oceanic islands such as Hawaii, Kerguelen or Canary islands.…”