• achondrite
• chondrite
• differentiation
• experimental petrology
• melting experiments
• parent body
• planetesimal
• planetesimal

In this PhD thesis, I explored the processes governing the evolution of planetesimals in the early solar system, investigating the role of partial melting of chondritic materials in the petrological evolution of small- to medium-sized planetary bodies. My research involved the high-pressure and high-temperature experimental investigations of melting and crystallization behaviour of natural chondritic meteorites (ordinary and carbonaceous chondrites), and the geochemical study of diverse achondrite groups (acapulcoites, aubrites, mesosiderites, and eucrites) by means of scanning electron microscope, electron probe micro-analyser, Raman spectroscopy, laser ablation-inductively coupled plasma-mass spectrometry, laser fluorination and synchrotron radiation X-ray computed micro-tomography. The textural and geochemical characterization of experimental and natural samples revealed a petrological connection between the primitive chondritic materials and some differentiated achondrites. In particular, experiments performed using an ordinary chondrite demonstrate that, at relatively low degrees of melting (less than 15%), silicate liquid with chemical composition comparable to some alkali- and silica-rich anomalous achondrites (i.e., GRA 60128/9, Almahata Sitta clast ALM-A, EC002, and NWA 11575) are produced. A similar result is reported for experiments performed using a carbonaceous chondrite, revealing the effect of devolatilization of the matrix minerals in modifying the mineralogical assemblage and providing some insights on the angrites and brachinites formation models. The silicate-metal fractionation under the effect of partial melting, investigated by means of synchrotron radiation X-ray microtomographic analysis of experimental products (experiments performed using the ordinary chondrite), is revealed to be inefficient in presence of interstitial silicate melt and under the isotropic conditions imposed by the experiments. Finally, I investigated post-differentiation processes in planetesimals using mesosiderites as a case study, revealing the complex evolution of their parent body, and their distinct origin with respect to HED meteorites, forming in distinct parent bodies and solving a long-standing question. The overall findings of this PhD thesis provide solid experimental constrain to the petrological evolution during melting of early formed planetesimals, giving valuable insights into the formation of the diverse meteoritic materials in the early solar system.