27 septembre 2021, 13h amphithéâtre du CRPG | Maxime Piralla (CRPG)
Origin and chronology of the first objects in the early solar system
Summary : Chondrules, one of the first igneous objects formed in the protoplanetary disk, are powerful proxies of the processes that occurred during the formation of solar system. They appear to have formed during 4 Ma but the dynamic and the nature of the production processes (time, continuous or discrete, efficiency) and the importance of the recycled precursors on their isotopic compositions and formation ages are largely under-constrained. Besides, the genetic and temporal links between CAIs, AOAs and chondrules are as well poorly known. Knowing the duration and chronology of the chondrule-forming processes are crucial for our understanding of the dynamic of the protoplanetary disk. The objectives of my PhD are to couple high precision 26Al-26Mg dating of chondrules with in situ oxygen isotope analyses in order to constrain the timing, conditions and efficiency of primordial solid formation in the protoplanetary disk. During this presentation, I will show you a comprehensive study of chondrules from ordinary chondrites with petrographic and isotopic evidences that explain their formation processes. Meanwhile, we explore a new method for chondrule dating using spinel from various chondrite groups. This shows a clear dichotomy between CAIs/AOAs and chondrules ages, with chondrules seeming to be formed during a similar period.