Melting and differentiation of early-formed asteroids: The perspective from high precision oxygen isotope studies

摘要: Abstract A number of distinct methodologies are available for determining the oxygen isotope composition minerals and rocks, these include laser-assisted fluorination, secondary ion mass spectrometry (SIMS) UV laser ablation. In this review we focus on which currently achieves highest levels precision analysis. particular, examine how results using method have furthered our understanding early-formed differentiated meteorites. Due to its rapid reaction times low blank levels, fluorination has now largely superseded conventional externally-heated Ni “bomb” technique bulk Unlike ablation SIMS analysis, is not capable focused spot While a mature technology, further analytical improvements possible via refinements construction sample chambers, clean-up lines use ultra-high resolution spectrometers. High-precision analysis proved be particularly powerful investigating formation evolution asteroids provided unique insights into interrelationships between various groups achondrites. clear example seen in samples that lie close terrestrial fractionation line (TFL). Based data from it was suggested main-group pallasites, howardite eucrite diogenite suite (HEDs) mesosiderites could all derived single common parent body. However, high demonstrates pallasites Δ 17 O fully resolvable HEDs mesosiderites, indicating involvement at least two bodies. The range values exhibited by an achondrite group provides useful means assessing extent their body underwent melting isotopic homogenization. Oxygen can also highlight relationships ungrouped achondrites more well-populated groups. proposed link evolved GRA 06128/9 meteorites brachinites. evidence isotopes, conjunction with other techniques, indicates approximately 110 asteroidal bodies (∼60 irons, ∼35 stony-iron,  ∼15 chondrites) global meteorite collection. compared likely size original protoplanetary asteroid population, extremely value. addition, almost (achondrites, stony-iron irons) were highly disrupted early evolution. some important origin mass-independent variation Solar System. primitive both slope 1 (Y&R) CCAM primordial significance. differences water ice silicate-rich solids probably initial source anomaly. These phases most acquired as result photo-dissociation CO took place either solar nebula or precursor giant molecular cloud. Such small-scale heterogeneities propagated larger-sized bodies, such planets, System processes, including dehydration, aqueous alteration, collisional interactions. There increasing chondritic accreted relatively late achondritic asteroids. This may account fact apart few notable exceptions’ aubrite-enstatite chondrite association, known been parents main