Figure 1 - uploaded by Alex Meshik
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Three-isotope plot for the Allende Curious Marie CAI. The I-Xe isochrons (free-fit, not forced through Q-Xe) correspond to low-and hightemperature releases of radiogenic Xe.
Source publication
The Allende fine-grained inclusion Curious Marie is a unique CAI. It is depleted in uranium but contains large ^(235)U excess [1], providing new evidence that ^(247)Cm was alive in the Early Solar System, as has been previously suggested [2], and leading to an updated (^(247)Cm/^(235)U)initial ratio of (1.1±0.3)×10^(-4).
Citations
... Release profiles of 129 *Xe and 128 *Xe indicate the presence of a major iodine mineral carrier phase characterized by melting in the 1,200-1,300 °C temperature range with 99.95% of 129 Xe and 128 Xe released below 1,450 °C. The concentration of 129 *Xe is 3.5 × 10 −8 cm 3 STP g −1 , compared with 1.0 × 10 −10 cm 3 STP g −1 for trapped 132 Xe, and is consistent with previous observations for finegrained Allende CAIs 17,18,25 . There is also an even smaller contribution from 244 Pu fission, 0.3 × 10 −10 cm 3 STP g −1 of 132 Xe (Fig. 1b). ...
... There is also an even smaller contribution from 244 Pu fission, 0.3 × 10 −10 cm 3 STP g −1 of 132 Xe (Fig. 1b). Small excesses of 130 Xe were observed and were not accompanied by excesses in 124,126,131 Xe, which would be expected in case of spallation, suggestive of Xe-G and consistent with our earlier observations for the neutron-irradiated Curious Marie aliquot 25 . ...
... The 130 Xe excesses are diagnostic of the Xe-G component in finegrained CAIs, as s-process contributions on other Xe isotopes are masked by I-derived and fission Xe. Although in our I-Xe dating studies 17,25 we observed small and variable 130 Xe excesses in some fine-grained Allende CV3 CAIs, including Curious Marie, these excesses could not be clearly attributed to s-process nucleosynthesis. ...
Calcium–aluminium-rich inclusions (CAIs) are one of the first solids to have condensed in the solar nebula, while presolar grains formed in various evolved stellar environments. It is generally accepted that CAIs formed close to the Sun at temperatures above 1,500 K, where presolar grains could not survive, and were then transported to other regions of the nebula where the accretion of planetesimals took place. In this context, a commonly held view is that presolar grains are found solely in the fine-grained rims surrounding chondrules and in the low-temperature fine-grained matrix that binds the various meteoritic components together. Here we demonstrate, on the basis of noble gas isotopic signatures, that presolar SiC grains were incorporated into fine-grained CAIs in the Allende carbonaceous chondrite at the time of their formation, and have survived parent-body processing. This finding provides new clues on the conditions in the nascent Solar System at the condensation of the first solids. A commonly held view is that presolar grains could not survive the high temperatures of the protoplanetary disk close to the Sun, where calcium–aluminium-rich inclusions (CAI) formed. Yet a detailed noble gas isotopic composition analysis of a CAI shows evidence of presolar SiC incorporated in it that could withstand high-temperature processing.
