10Be-10B systematics of chondrules and refractory objects in primitive chondrites

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The short-lived isotope 10Be was present in the early solar system and produced by energetic particle irradiation, either from the early sun by solar cosmic rays or during collapse of the giant molecular cloud by interaction with galactic cosmic rays. Refractory inclusions with canonical 26Al/27Al ratio have a slightly higher initial 10Be/9Be ratio than hibonites from Murchison with 26Al deficit. As both types of refractory materials are commonly considered as earliest solar nebula material, the decoupling of initial 10Be/9Be and 26Al/27Al is interpreted as evidence for a different initial distribution in the solar nebula, 26Al being derived from a nucleosynthetic and 10Be from a solar irradiation source. However, it is unclear to what extent different irradiation settings of the precursor material (irradiation time and location, shielding effects and production rates) could lead to differences, as precursor material of refractory CAIs and hibonites may have principally very similar exposure histories. Chondrules are a type of material that formed 1-4 Ma after CAIs, by different energetic processes in a different environment. However, the low degree of Be/B fractionation mostly precludes evaluation of the initial 10Be/9Be ratio. Nevertheless, two promising—though not compelling—case studies exist on Al-rich chondrules, where it was shown that fractionation seems to be sufficiently large to constrain the initial 10Be/9Be with modern SIMS (IMS 1280-HR) techniques. Hence a new attempt on Al-rich chondrules of primitive carbonaceous and enstatite chondrites, as well as refractory materials from enstatite chondrites (CAIs and oldhamites) seems promising, particular if preparation and measuring techniques avoiding boron contamination are used.