The mantle is the main source of the magmas that extrude at the Earth surface and an essential goal for Earth scientists is to understand how this reservoir works and how it produces different types of melts. The isotopic variability of mantle-derived melts reflects the lithological heterogeneity of their source, but provides little information on how these heterogeneities were acquired. The Ronda peridotite (southern Spain) is a unique natural laboratory to unravel how the mantle acts during melting. Indeed, the Ronda Massif preserves a unique example of a sharp melting front affecting a heterogeneous mantle domain composed of peridotite and garnet pyroxenite thrust tectonically on to the Earth’s surface. The applicant proposes to carry out both whole rock and in-situ trace element and (Sr-Nd-Hf-Pb-Os) isotopic analyses in pyroxenites and wall-rock peridotites located at different distances from the Ronda melting front. This study will provide new insights into how different radiogenic isotopes behave during partial melting of a mixed pyroxenite-peridotite mantle, how the interaction between pyroxenite melts and host-peridotite affects the isotopic composition of the mantle, and to what length-scales these isotopic systems are homogenized and/or decoupled during mantle melting. The proposed Career Development Plan will permit to complement the professional skills of the candidate in analytical geochemistry and will be fundamental for his potential success as Earth Scientist. The host organization (Géosciences Montpellier, France) is internationally reputed one of the best European laboratories in mantle geochemistry research. The programmed collaboration with a third-country institution (GEMOC, Macquarie University, Australia) will strengthen the international cooperation of European researchers with one of the world’s best equipped geochemical laboratory.