Mineralogical zonation in chondrules and chemical chondrule-matrix complementarities in carbonaceous and Rumuruti chondrites

Chondritic meteorites (´chondrites`) are primitive early solar system materials; the composition of chondrites—especially of CI chondrites—represent the average solar system composition. The two main components of chondrites are (i) chondrules, µm to mm-sized silicatic melt droplets, and (ii) matrix, an opaque and fine-grained unequilibrium mineral assemblage. The origin of these two constituents, especially for the heat source required for melting chondrules, is still enigmatic. In this work, the genetic link between chondrules and matrix was studied. \nA mineralogical zonation with olivine minerals dominating the cores and low-Ca pyroxenes at the margins are present in at least 75% of all chondrules studied in chapter 2. In total, 256 chondrules of 16 different carbonaceous and Rumuriti chondrites (R chondrites) were studied. The low-Ca pyroxene rims were formed by addition of Si to the chondrules (or their precursor) from the surrounding nebula gas, which later condensed to form matrix. Hence, chondrules were open systems and gained 3-15 wt.% material by this process. \nIn chapters 3 and 4, bulk chondrule, matrix and bulk meteorite compositions of the recently found CM chondrite Jbilet Winselwan (JW) and of three different R chondrites were studied. Bulk chondrule and matrix compositions were obtained with the electron microprobe and bulk meteorite compositions with X-ray spectrometry. \nJbilet Winselwan and the R chondrites show chemical complementarities. Thus, although bulk meteorite compositions are CI chondritc (=solar), chondrules and matrix have different compositions. The amount of matrix in the studied chondrites are at least 50 vol.%. All chondrites have higher than bulk ratios of Fe/Mg, Si/Mg, Al/Ti, Al/Ca in the matrices and vice versa in chondrules. Bulk chondrite ratios are (except Si/Mg in R chondrites) CI chondritic. These complementarities, together with the solar bulk composition of the meteorites, can only be explained when chondrules and matrix formed from a single reservoir. \nIn chapter 4, complementarity is, to my knowledge, for the first time reported in non-carbonaceous chondrites. It is assumed that carbonaceous and non-carbonaceous chondrites formed in distinct regions within the solar system. A joint formation of chondrules and matrix is required for both reservoirs.