We present the first results of a comprehensive investigation aimed at testing the hypothesis of chondrule-matrix complementarity and the four-component model for the compositions of the carbonaceous chondrites and their components. Combining point-counting with electron microprobe analyses, we have determined the bulk compositions of thin sections, as well as the average abundances and compositions of the major chondritic components (chondrules, matrix, refractory inclusions, isolated silicate grains and isolated opaque grains). To minimize the potential for element exchange between components during parent body processing, the two most primitive COs, DOM 08006 and ALH 77307, and the primitive ungrouped CO/CM-like Acfer 094 were selected for this study. To verify our method, we also examined one section of the well-studied CO3.2 Kainsaz, a fall that is free of weathering. We were able to reproduce all major and many minor elemental concentrations reported in the literature for average bulk COs and Kainsaz to better than 10%. The elements most commonly cited as displaying evidence for complementarity are Mg, Si, Al, Ca, Fe and Ti. Iron, however, can be easily affected by chondrule metal-silicate fractionation, redistribution in the parent body and weathering, and our Ti data for matrix are likely compromised by an analytical artifact. Hence, we focused on Mg, Al, Si and Ca – four elements that we can determine very accurately – and show that their relative abundances in chondrules are on average CI-like within the uncertainties of the method. The matrix is not CI-like, but its composition can be explained by the loss of 10–15 wt.% of forsterite from an initially CI-like material prior to or during parent body accretion. These results are inconsistent with chondrule-matrix complementarity. Our average CO chondrule compositions, as well as chondrule and matrix abundances, are in line with the predictions of the four-component model. However, the four-component model assumes a CI-like composition for matrix, and also predicts refractory inclusion abundances that are higher and compositions that are less refractory than we observe. While similar studies of the other carbonaceous chondrite groups are needed, these differences may indicate the limitations of the simplifying assumptions made in the four-component model.

我们提出了一项全面调查的第一个结果，旨在检验软骨-基质互补性假说和碳质球粒陨石及其成分组成的四组分模型。结合点计数和电子探针分析，我们确定了薄片的本体组成，以及主要软骨成分（软骨，基质，难熔夹杂物，孤立的硅酸盐晶粒和孤立的不透明晶粒）的平均丰度和组成。为了使母体处理过程中组件之间元素交换的可能性最小化，本研究选择了两个最原始的CO，即DOM 08006和ALH 77307，以及原始的未分组的类似CO / CM的Acfer 094。为了验证我们的方法，我们还研究了经过深入研究的CO3.2 Kainsaz的一部分，没有风化的秋天。我们能够重现文献中报告的所有主要和许多次要元素浓度，将平均散装CO和Kainsaz的浓度提高到10％以上。Mg，Si，Al，Ca，Fe和Ti最常被引用为显示互补性的元素。然而，铁很容易受到球状金属硅酸盐分馏，母体中的再分布和风化的影响，并且我们的基质Ti数据可能会受到分析伪影的影响。因此，我们集中于镁，铝，硅和钙（我们可以非常准确地确定它们的四个元素），并表明在方法的不确定性范围内，它们在球状晶体中的相对丰度平均呈CI状。基质不是CI样的，但是其组成可以通过损失10-15 wt％来解释。在母体增生之前或期间，由最初类似CI的材料产生的镁橄榄石的百分比。这些结果与软骨基质互补性不一致。我们的平均CO软骨组成以及软骨和基质的丰度与四组分模型的预测相符。但是，四组分模型假设基质的CI成分相同，并且预测的耐火材料夹杂物丰度更高，而耐火材料的组成则比我们观察到的少。尽管需要对其他碳质球粒陨石组进行类似的研究，但这些差异可能表明在四组分模型中简化假设的局限性。以及软骨和基质的丰度，与四成分模型的预测相符。但是，四组分模型假设基质的CI成分相同，并且预测的耐火材料夹杂物丰度更高，而耐火材料的组成则比我们观察到的少。尽管需要对其他碳质球粒陨石组进行类似的研究，但这些差异可能表明在四组分模型中简化假设的局限性。以及软骨和基质的丰度，与四成分模型的预测相符。但是，四组分模型假设基质的CI成分相同，并且预测的耐火材料夹杂物丰度更高，而耐火材料的组成则比我们观察到的少。尽管需要对其他碳质球粒陨石组进行类似的研究，但这些差异可能表明在四组分模型中简化假设的局限性。