Computer Science
Scientific paper
Sep 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995metic..30r.482a&link_type=abstract
Meteoritics, vol. 30, no. 5, page 482
Computer Science
Chondrites, Ci, Elements, Trace, Volatile, Interplanetary Dust Particles, Reliability, Statistical Analyses
Scientific paper
Introduction: Major, minor, and trace element contents may play a decisive role in unrevealing the possible origin(s) of stratospheric interplanetary dust particles (IDPs). We compiled a complete table of all analysed IDPs that includes data of 89 particles obtained with PIXE, SXRF, or SIMS. Before subjecting these data to statistical analyses the reliability of the trace element data was proven by various cross-checks: Reliability: In 1989, Wallenwein et al. had analysed two IDPs with PIXE in Heidelberg and afterwards with SXRF in Hamburg and found non-conflicting abundances for 16 detected elements and only one discrepancy for each IDP [1]. In 1992 we re-analysed with PIXE six IDPs that were measured also with PIXE in 1985 by van der Stap and found an agreement within a factor of about 2.5 between both data sets which is not really satisfying. With PIXE in Heidelberg we repeated analyses of the same two IDPs and found identical results. A comparison between the actual facilities of PIXE in Heidelberg and SXRF in Brookhaven leads to a convincing agreement between these two techniques [2]. As a test--actually as a by-product of an experiment to determine the influence of pulse heating on CI material [3] ( we analysed by means of PIXE 64 fragments (~50-100 micrometers) from the CI chondrites Orgueil and Alais to test the reliability of our actual pixe data [4]. We found most of the 18 elements between Mg and Zr in good agreement with CI [5]. But the means of these elements, for which our limits of detection (LODs) were close to CI, appear enriched which was the case for Sc, Co, As, Rb, Y, and Zr. Statistical analyses: Here we report on the results of cluster analyses we performed on IDP compositions. We took into account data from 89 particles and 28 elements between Na and Zr. Because of missing data - only Fe could be detected in all 89 particles - we clustered with the elements Cr, Mn, Ni, Cu, and Zn (normalized to Fe and CI chondrites), which were determined in the rather large amount of 73 IDPs. The data arrange themselves in (rather poorly defined) four groups which we will discuss in relation to CI chondrites. Results: The largest group with 44 members--provisionally we dub it normal--has abundances close to CI for many refractory and moderately refractory elements (Na, Al, Si, P, K, Sc, Ti, V, Cr, Co, Ge, Sr). It is depleted slightly in Fe and more in Ca and S, while the volatile elements (Cl, Cu, Zn, Ga, Se, Rb) are enriched by ~1.7 x CI and Br by 21 x CI. The next group with 12 members--dubbed low-Zn--is very similar to the normal group except its Zn-depletion, larger Ca-depletion and Fe-enrichment. The third group with 11 members--dubbed low-Ni--has Ni/Fe=0.03 x CI and almost CI-like Ca. The last group (6 members) is non-chondritic and of unknown origin. Excluding these non-chondritic particles, the means of the remaining 67 particles show enrichments of the trace elements compared to CI. These can be explained by contaminating processes or by an overestimation because of measuring near the LODs, since in the latter case the lowest - not detected - concentrations could not be taken into account. Conclusions: The present data set can be classified only in poorly discriminated groups by using Cr, Mn, Ni, Cu, and Zn, but between these groups there are some significant differences in further elements not used for this cluster analysis. Especially Ca might play an important r
Arndt Peter
Jessberger Elmar K.
Maetz Mischa
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