Abstract Details
(2020) In situ Titanium Isotope Measurements and the Search for the Source of Nucleosynthetic Anomalies in Bulk Chondrites
Shaw KMM, Pfeifer M, Coath CD, Parkinson IJ & Elliott T
https://doi.org/10.46427/gold2020.2352
The author has requested that this abstract is not discussed on social media.
The author has not provided any additional details.
01g: Plenary Hall, Thursday 25th June 22:03 - 22:06
Kathryn M M Shaw
Markus Pfeifer View abstracts at 9 conferences in series
Christopher D. Coath View all 5 abstracts at Goldschmidt2020 View abstracts at 6 conferences in series
Ian J Parkinson
Tim Elliott View all 8 abstracts at Goldschmidt2020 View abstracts at 7 conferences in series
Markus Pfeifer View abstracts at 9 conferences in series
Christopher D. Coath View all 5 abstracts at Goldschmidt2020 View abstracts at 6 conferences in series
Ian J Parkinson
Tim Elliott View all 8 abstracts at Goldschmidt2020 View abstracts at 7 conferences in series
Listed below are questions that have been submitted by the community that the author will try and cover in their presentation. To submit a question, ensure you are signed in to the website. Authors or session conveners approve questions before they are displayed here.
Submitted by Larry Nittler on Wednesday 24th June 22:24
very interesting talk! It looks like you're two isotope hotspots are from the same region of the meteorite, but identified in different scans, correct? Presumably, this means, for example, that the one on the right images was originally buried and appeared after material was ablated. Do you know how much material is removed per scan? (could help constrain size of grains if they are smaller than resolution?)
Thank you! Yes there were 3 scans over the same area, and the hotspots were found in scan 1 and 3 with none found in scan 2. So the second hotspot was uncovered after 2 scans. The depth of each scan is on the scale of 0.5-0.8 microns, with a planar "pixel" resolution of 3 x 2.4 microns. The size of the grains is hard to constrain without assuming the grain is roughly uniform shaped and was not ablated over more than one pixel. But given the depth ablated is < 1 micron and the hotspots were not found in the subsequent scan, I would like to say these grains were not big grains at several microns across but more on the order of 100's nm to possibly 1 micron.
very interesting talk! It looks like you're two isotope hotspots are from the same region of the meteorite, but identified in different scans, correct? Presumably, this means, for example, that the one on the right images was originally buried and appeared after material was ablated. Do you know how much material is removed per scan? (could help constrain size of grains if they are smaller than resolution?)
Thank you! Yes there were 3 scans over the same area, and the hotspots were found in scan 1 and 3 with none found in scan 2. So the second hotspot was uncovered after 2 scans. The depth of each scan is on the scale of 0.5-0.8 microns, with a planar "pixel" resolution of 3 x 2.4 microns. The size of the grains is hard to constrain without assuming the grain is roughly uniform shaped and was not ablated over more than one pixel. But given the depth ablated is < 1 micron and the hotspots were not found in the subsequent scan, I would like to say these grains were not big grains at several microns across but more on the order of 100's nm to possibly 1 micron.
Submitted by Mattias Ek on Thursday 25th June 13:09
Given the number of scans you have made can you comment on how rare these gains are?
This is a very difficult question to answer based on our current ablation resolution. If we are ablating smaller grains they have to be anomalous enough to not be diluted by any solar system Ti in the matrix. This is also complicated by the in situ method where half a grain may be ablated in one measurement and the other half in the next. This would mean the grain is there but was not detected as each half was too diluted by surrounding Ti in the matrix. Ideally a higher resolution would decrease the chance of diluting any presolar material with the laser measurement. So I would say what we have found is a minimum concentration. 2 hotspots in 45,000 measurements.
Given the number of scans you have made can you comment on how rare these gains are?
This is a very difficult question to answer based on our current ablation resolution. If we are ablating smaller grains they have to be anomalous enough to not be diluted by any solar system Ti in the matrix. This is also complicated by the in situ method where half a grain may be ablated in one measurement and the other half in the next. This would mean the grain is there but was not detected as each half was too diluted by surrounding Ti in the matrix. Ideally a higher resolution would decrease the chance of diluting any presolar material with the laser measurement. So I would say what we have found is a minimum concentration. 2 hotspots in 45,000 measurements.
Submitted by Mattias Ek on Thursday 25th June 13:15
How do you plan to take this technique forawrd to futher constrain the origin of the grains you measure?
Having knowledge of the mineralogy of the grain (SiC, oxide, silicate) would be extremely helpful to identify the origin of the grains found. We would like to do this by high resolution element mapping, possibly using an electron probe. Or another possibility which would allow us to place the grains with other measurements undertaken, is mapping the C, Si, N or O isotopic composition. Both of these would have to be done with preserving as much of the grain as possible so there is enough left to measure the Ti afterwards.
How do you plan to take this technique forawrd to futher constrain the origin of the grains you measure?
Having knowledge of the mineralogy of the grain (SiC, oxide, silicate) would be extremely helpful to identify the origin of the grains found. We would like to do this by high resolution element mapping, possibly using an electron probe. Or another possibility which would allow us to place the grains with other measurements undertaken, is mapping the C, Si, N or O isotopic composition. Both of these would have to be done with preserving as much of the grain as possible so there is enough left to measure the Ti afterwards.
Submitted by Paul Frossard on Thursday 25th June 22:19
Do you plan to measure Cr isotopes as well, as Nittler et al. (2018) measured large excesses of 54Cr and 50Ti on individual grains? Can the collision cell and pre-filter quadrupole allow good separation of Cr from Ti, V, and other interfering species?
This is an interesting project that we have thought about since Cr has been proposed to have an oxide carrier phase. The big isobaric interference for the 54Cr is the Fe. And we have been looking into ways of reacting the Cr away from the Fe as well as the Ti and V. It's definitely a possibility.
Do you plan to measure Cr isotopes as well, as Nittler et al. (2018) measured large excesses of 54Cr and 50Ti on individual grains? Can the collision cell and pre-filter quadrupole allow good separation of Cr from Ti, V, and other interfering species?
This is an interesting project that we have thought about since Cr has been proposed to have an oxide carrier phase. The big isobaric interference for the 54Cr is the Fe. And we have been looking into ways of reacting the Cr away from the Fe as well as the Ti and V. It's definitely a possibility.
Sign in to ask a question.