EH3 matrix mineralogy with major and trace element composition compared to chondrules

Lehner, S. W. and Mcdonough, W. F. and Németh, Péter (2014) EH3 matrix mineralogy with major and trace element composition compared to chondrules. METEORITICS & PLANETARY SCIENCE, 49 (12). pp. 2219-2240. ISSN 1086-9379

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Abstract

We investigated the matrix mineralogy in primitive EH3 chondrites Sahara 97072, ALH 84170, and LAR 06252 with transmission electron microscopy; measured the trace and major element compositions of Sahara 97072 matrix and ferromagnesian chondrules with laser-ablation, inductively coupled, plasma mass spectrometry (LA-ICPMS); and analyzed the bulk composition of Sahara 97072 with LA-ICPMS, solution ICPMS, and inductively coupled plasma atomic emission spectroscopy. The fine-grained matrix of EH3 chondrites is unlike that in other chondrite groups, consisting primarily of enstatite, cristobalite, troilite, and kamacite with a notable absence of olivine. Matrix and pyroxene-rich chondrule compositions differ from one another and are distinct from the bulk meteorite. Refractory lithophile elements are enriched by a factor of 1.5-3 in chondrules relative to matrix, whereas the matrix is enriched in moderately volatile elements. The compositional relation between the chondrules and matrix is reminiscent of the difference between EH3 pyroxene-rich chondrules and EH3 Si-rich, highly sulfidized chondrules. Similar refractory element ratios between the matrix and the pyroxene-rich chondrules suggest the fine-grained material primarily consists of the shattered, sulfidized remains of the formerly pyroxene-rich chondrules with the minor addition of metal clasts. The matrix, chondrule, and metal-sulfide nodule compositions are probably complementary, suggesting all the components of the EH3 chondrites came from the same nebular reservoir.

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