Melt–rock interactions in a veined mantle: pyroxenite–peridotite reaction experiments at 2 GPa

Abstract. Interaction between peridotite and pyroxenite-derived melts can significantly modify the mineralogy chemistry of upper mantle, enhancing its heterogeneity, by creating re-fertilized peridotites secondary-type pyroxenites. We experimentally investigated reaction a fertile lherzolite MgO-rich basaltic andesite produced partial melting an olivine-free pyroxenite at 2 GPa 1300–1450 ∘C. The aim was to constrain rate style melt–peridotite mostly as function temperature, i.e. assuming variable physical status host peridotite. Experiments juxtaposed on synthesized evaluate modal mineral compositional changes in resulting from with melt. At 1300 1350 ∘C, produces thin orthopyroxene-rich zone confined partially molten modally unmodified subsolidus lherzolite. Chemical minerals crystal mush suggest that element diffusion across pyroxenite–peridotite interface, coupled orthopyroxene precipitation, plays role reactive crystallization mantle veins. 1380 1400 infiltration melt modifies websterites pyroxene-rich 1450 pyroxenitic fluxes into peridotite, melt-bearing dunite associated refractory harzburgite. given pressure, bulk compositions hybrid rocks originating through interaction are controlled reacting causes XMg[XMg=Mg/(Mg+Fetot)] XCr[XCr=Cr/(Cr+Al)] decrease TiO2 increase pyroxenes spinel boundary. Similar chemical gradients observed associations natural sequences. comparison variations derived experiments potentially represents petrologic tool discriminate low- versus high-temperature reactions.