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首页> 外文期刊>Journal of Archaeological Science >Nucleation of aragonite upon carbonation of calcium oxide and calcium hydroxide at ambient temperatures and pressures: a new indicator of fire-related human activities
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Nucleation of aragonite upon carbonation of calcium oxide and calcium hydroxide at ambient temperatures and pressures: a new indicator of fire-related human activities

机译：在环境温度和压力下碳酸钙和氢氧化钙碳酸化时文石的核化：与火灾有关的人类活动的新指标

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摘要

Wood ash found at archaeological sites is the most direct evidence of the presence of combustion features. The preservation of wood ash within archaeological deposits is often poor due to diagenetic processes and therefore its identification requires the use of spectroscopic methods. FTIR spectrometry is able to detect the main calcite component of wood ash, unless this is mixed with other calcitic phases of geologic origin. Using FTIR spectrometry we identified non-biogenic aragonite in archaeological heataltered sediments and lime plasters. The presence of aragonite in such conditions is unusual, as it is unlikely to crystallize at ambient temperatures and pressures or in absence of Mg. The experimental conditions which favor the nucleation of this aragonite phase were investigated with FTIR spectrometry, XRPD and SEM imaging of modern lime plaster and quicklime samples prepared in the laboratory using different calcium carbonate starting materials. We show that aragonite forms at ambient temperatures and pressures upon carbonation of calcium oxide and calcium hydroxide together with calcite and its nucleation and growth are influenced by environmental parameters, such as carbon dioxide partial pressure, relative humidity and temperature. This pyrogenic aragonite is a reliable indicator for calcareous materials exposed to temperatures above 600 ℃, and therefore it can be used to determine the presence of heat-altered sediments and ash in the absence of structured combustion features. This mineral phase could have applications in radiocarbon dating as well.
机译：在考古现场发现的木灰是燃烧特征存在的最直接证据。由于成岩过程，考古沉积物中木灰的保存通常很差，因此，其鉴定需要使用光谱学方法。 FTIR光谱法能够检测出木灰的主要方解石成分，除非将其与地质来源的其他钙相混合。使用FTIR光谱仪，我们在考古学改变沉积物和石灰灰泥中鉴定了非生物文石。在这种条件下文石的存在是不寻常的，因为它不可能在环境温度和压力下或在没有镁的情况下结晶。通过FTIR光谱，XRPD和SEM成像，研究了使用不同碳酸钙起始原料在实验室中制备的现代石灰石膏和生石灰样品的有利于该文石相成核的实验条件。我们表明文石在环境温度和压力下与方解石一起碳化时会形成氧化钙和氢氧化钙，其成核和生长受环境参数（例如二氧化碳分压，相对湿度和温度）的影响。该热解文石是钙质材料暴露于600℃以上温度的可靠指示剂，因此，在没有结构化燃烧特征的情况下，它可用于确定热变质沉积物和灰分的存在。该矿物相也可能在放射性碳测年中具有应用。

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