Fifteen elements, including most of the major elements, were quantified using neutron-induced prompt gamma-ray analysis for five Antarctic carbonaceous chondrites with CI affinities and seven with CM affinities. Common among the twelve meteorites is the depletion of volatile elements H and chlorine, showing a positive correlation and being depleted compared to non-Antarctic CI levels. This depletion is not thought to have occurred after the fall on Antarctica, but to have been caused by thermal metamorphism on the parent body. Among the meteorites analyzed in this study, six meteorites (Y-86029, Y 980115 and Y-82162 (with CI affinities), and Y-86720, Y-86789 and B-7904 (with CM affinities)) have previously been proposed to constitute a new meteorite group, the Yamato-type (CY), based on their oxygen isotopic compositions and petrological features. The elemental compositional characteristics of the remaining six meteorites analyzed in this study, Y-86737 and Y 980134 (with CI affinities), and Y-86770, Y-86771, Y-86772 and Y-86773 (with CM affinities), suggest that these meteorites are all classified into the same chemical group CY. Based on the abundance of moderately volatile elements Mn and S, the twelve meteorites can be divided into two groups: one with levels similar to non-Antarctic CI and the other with intermediate levels between CI and CM. These results suggest that CY chondrites originate from two distinct parent bodies. To facilitate further discussions on CY chondrites, we propose naming the groups with compositions close to CI and CM as CYi and CYm, respectively.

中文翻译：

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Yamato 型 （CY） 碳质球粒陨石的化学特性


使用中子诱导的瞬发伽马射线分析对 5 种具有 CI 亲和力的南极碳质球粒陨石和 7 种具有 CM 亲和力的南极碳质球粒陨石量化了 15 种元素，包括大多数主要元素。这十二颗陨石的共同点是挥发性元素 H 和氯的消耗，与非南极 CI 水平相比，它们呈正相关并耗尽。这种消耗被认为不是在南极洲坠落后发生的，而是由母体的热变质作用引起的。在本研究分析的陨石中，六颗陨石（Y-86029、Y 980115 和 Y-82162（具有 CI 亲和力）以及 Y-86720、Y-86789 和 B-7904（具有 CM 亲和力））先前曾被提议根据它们的氧同位素组成和岩石学特征构成一个新的陨石群，即大和型 （CY）。本研究分析的其余六颗陨石 Y-86737 和 Y 980134（具有 CI 亲和力）以及 Y-86770、Y-86771、Y-86772 和 Y-86773（具有 CM 亲和力）的元素组成特征表明，这些陨石都属于同一化学组 CY。根据中等挥发性元素 Mn 和 S 的丰度，这 12 颗陨石可分为两组：一组水平与非南极 CI 相似，另一组水平介于 CI 和 CM 之间。这些结果表明，CY 球粒陨石起源于两个不同的母体。为了促进对 CY 球粒陨石的进一步讨论，我们建议将组成接近 CI 和 CM 的组分别命名为 CYi 和 CYm。