Characterization of carbonaceous matter in xenolithic clasts from the Sharps (H3.4) meteorite: Constraints on the origin and thermal processing
Characterization of carbonaceous matter in xenolithic clasts from the Sharps (H3.4) meteorite: Constraints on the origin and thermal processing
复制标题
Sharps (H3.4) 陨石捕虏体碎屑中碳质的表征：对起源和热处理的限制
DOI：
10.1016/j.gca.2016.09.024
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发表时间：
2017
影响因子：
5
通讯作者：
G. D. Cody
中科院分区：
文献类型：
--
作者：
5.Y. Kebukawa;M. E. Zolensky;Q. H. S. Chan;K. Nagao;A. L. D. Kilcoyne;R. J. Bodnar;C. Farley;Z. Rahman;L. Le;G. D. Cody
原始捕虏体碎屑，通常被称为“黑暗碎屑”，是众所周知的许多风化角砾岩。夏普斯H3.4普通球粒陨石含有异常大的黑色碎屑，直径可达1.01厘米。据报告，这些碎屑中含有石墨化程度低的碳（PGC）和铁、镍金属，被称为“富碳聚集体”（Brearley，1990年）。我们报告的碳质物质在几个相同的夏普碎屑使用FTIR，拉曼，C-XANES和TEM，提供洞察力的热处理程度和可能的起源，这样的碎屑的详细分析。我们还使用HCl/HF方法制备了碎屑的酸残留物，并对夹带的惰性气体进行了质谱分析。由于碳质物质对热过程的敏感性，它通常被用来推断热历史。从夏普斯碎屑的酸残留物的FTIR光谱表明，在碎屑中的碳质物质含有较少的氢和氧相比，从典型的3.4型普通方解石的酸残留物。通过拉曼光谱得到的变质温度范围在380 °C到490 °C之间。TEM观察表明，碎屑经历了300 °C至400 °C的峰值温度，基于富C聚集体的碳002层晶格间距。这些估计值与早先的330 ± 50 °C的估计值一致，后者也是通过d 002层晶格间距估计的（Brearley，1990）。应该指出的是，格点间距温度计是基于陆地变质岩石，因此温度可能被低估。同时，富C聚集体的C-XANES光谱显示出高激子强度，表明石墨烯结构在长时间（数百万年）后在约700-800 °C下形成，然而，周围基质区域经历了低于300-500 °C的较低温度。对夏普斯碎屑的酸性残留物进行的稀有气体分析表明，该残留物与碳质碎屑中报告的某些物质几乎相同，即，这些结果表明，Sharps碎屑中的富C聚集体是在高达800 °C的相对高温条件下形成的，随后与较低温度的基质混合，可能在不同的母体中，然后通过碰撞并入最终的Sharps岩性中。
Primitive xenolithic clasts, often referred to as “dark clasts”, are well known in many regolith breccias. The Sharps H3.4 ordinary chondrite contains unusually large dark clasts up to ∼1 cm across. Poorly-graphitized carbon (PGC), with Fe, Ni metal and described as “carbon-rich aggregates”, has been reported in these clasts (Brearley, 1990). We report detailed analyses of carbonaceous matter in several identical Sharps clasts using FTIR, Raman, C-XANES, and TEM that provide insight on the extent of thermal processing and possible origin of such clasts. We also prepared acid residues of the clasts using the HCl/HF method and conducted mass spectrometric analysis of the entrained noble gases.Carbonaceous matter is often used to infer thermal history due to its sensitivity to thermal processes. The FTIR spectra of the acid residue from the Sharps clast suggest that carbonaceous matter in the clast contains less hydrogen and oxygen compared to acid residues from typical type 3.4 ordinary chondrites. The metamorphic temperatures obtained by Raman spectroscopy ranges between ∼380 °C and ∼490 °C. TEM observations indicate that the clasts experienced a peak temperature of 300 °C to 400 °C, based on the carbond002layer lattice spacing of C-rich aggregates. These estimates are consistent with an earlier estimate of 330 ± 50 °C, that is also estimated by thed002layer lattice spacing (Brearley, 1990). It should be noted that the lattice spacing thermometer is based on terrestrial metamorphose rocks, and thus temperature was probably underestimated. Meanwhile, the C-XANES spectra of the C-rich aggregates show high exciton intensities, indicative of graphene structures that developed at around 700–800 °C following an extensive period of time (millions of years), however, the surrounding matrix areas experienced lower temperatures of less than 300–500 °C. Noble gas analysis of the acid residue from the Sharps clasts shows that the residue is almost identical with some material reported in carbonaceous chondrites, i.e., heavily enriched in the Q-gas component as well as HL-gas from presolar diamonds and Ne-E(H) from presolar SiC.These results indicate that the C-rich aggregates in the Sharps clasts formed under relatively high temperature conditions, up to 800 °C, and were subsequently mixed with lower temperature matrix, probably in a different parent body, before they were incorporated into the final Sharps lithology by collision.