Fe-Ni metal and sulfide minerals in CM chondrites: An indicator for thermal history
Fe-Ni metal and sulfide minerals in CM chondrites: An indicator for thermal history
复制标题
CM 球粒陨石中的铁镍金属和硫化物矿物：热史指标
DOI：
10.1111/j.1945-5100.2010.01164.x
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发表时间：
2011
影响因子：
2.2
通讯作者：
and M. K. Weisberg
中科院分区：
文献类型：
--
作者：
M. Kimura;J. N. Grossman;and M. K. Weisberg
CM球粒陨石遭受水蚀变，在某些情况下，遭受二次变质加热。这些过程的影响差异很大，主要记录在硅酸盐相中。本文报道了13cm和2cm球粒陨石中Fe - Ni金属和硫化物相的特征特征，以探索这些球粒陨石的热历史。CM中金属的织构和成分分布与不平衡的普通球粒陨石和CO球粒陨石不同，但与CH、CR和Acfer 094等高度原始的球粒陨石相似。我们根据金属成分和硫化物结构将CM样品分为三类。A类铁镍金属为马马体-马氏体。B类的特点是磁黄铁矿颗粒中总是含有镍黄铁矿的泡状或片状。C类不透明矿物组合通常为绢云母矿、富镍钴金属和磁黄铁矿。这些类别与二次加热程度密切相关，而与含水蚀变程度无关。不透明矿物的特征可以用水蚀变后的二次加热过程来解释。A类CM球粒陨石未被加热，而B类CM球粒陨石则经历了小程度的二次加热。C类CMs的二次加热过程最为严重。因此，不透明矿物可以为CM球粒陨石的热历史提供限制。
CM chondrites were subjected to aqueous alteration and, in some cases, to secondary metamorphic heating. The effects of these processes vary widely, and have mainly been documented in silicate phases. Herein, we report the characteristic features of Fe‐Ni metal and sulfide phases in 13 CM and 2 CM‐related chondrites to explore the thermal history of these chondrites. The texture and compositional distribution of the metal in CM are different from those in unequilibrated ordinary and CO chondrites, but most have similarities to those in highly primitive chondrites, such as CH, CR, and Acfer 094. We classified the CM samples into three categories based on metal composition and sulfide texture. Fe‐Ni metal in category A is kamacite to martensite. Category B is characterized by pyrrhotite grains always containing blebs or lamellae of pentlandite. Opaque mineral assemblages of category C are typically kamacite, Ni‐Co‐rich metal, and pyrrhotite. These categories are closely related to the degree of secondary heating and are not related to degree of the aqueous alteration. The characteristic features of the opaque minerals can be explained by secondary heating processes after aqueous alteration. Category A CM chondrites are unheated, whereas those in category B experienced small degrees of secondary heating. CMs in category C were subjected to the most severe secondary heating process. Thus, opaque minerals can provide constraints on the thermal history for CM chondrites.