Evidence from the Rb-Sr system for 4.4 Ga alteration of chondrules in the Allende (CV3) parent body

摘要: The timing and processes of alteration in the CV parent body are investigated by analysis Sr isotopes, major trace elements, petrographic type distribution secondary minerals (nepheline sodalite) 22 chondrules from Allende (CV3) chondrite. isotopic compositions scattered around 4.0 Ga reference line on 87Sr/ 86Sr evolution diagram, indicating that have been affected late thermal event(s) body. degree alteration, determined for individual based nepheline sodalite, is unrelated to disturbance Rb-Sr system, suggesting process produced sodalite different disturbed system chondrules. Considering geochemical behavior Rb Sr, main host phase likely be mesostasis, which could most susceptible alteration. As there a poor connection between abundances we consider mesostasis provide constraint process. From this point view, 23 mesostasis-rich chondrules, including those literature data, were selected. selected closely correlated 87Sr/86Sr with an inferred age 4.36 ±  0.08 Ga. This correlation would represent final redistribution