Toffolo Michael B, Pinkas Iddo, Gallo Ana Álvaro, Boaretto Elisabetta
Geochronology and Geology Program, Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), Paseo Sierra de Atapuerca 3, 09002, Burgos, Spain.
Department of Chemical Research Support, Weizmann Institute of Science, 234 Herzl Street, 7610001, Rehovot, Israel.
Sci Rep. 2023 Aug 10;13(1):12971. doi: 10.1038/s41598-023-39842-8.
Anthropogenic calcite is a form of calcium carbonate produced through pyrotechnological activities, and it is the main component of materials such as lime binders and wood ash. This type of calcite is characterized by a significantly lower degree of crystallinity compared with its geogenic counterparts, as a result of different formation processes. The crystallinity of calcite can be determined using infrared spectroscopy in transmission mode, which allows decoupling particle size effect from atomic order and thus effectively distinguish anthropogenic and geogenic calcites. On the contrary, Raman micro-spectroscopy is still in the process of developing a reference framework for the assessment of crystallinity in calcite. Band broadening has been identified as one of the proxies for crystallinity in the Raman spectra of geogenic and anthropogenic calcites. Here we analyze the full width at half maximum of calcite bands in various geogenic and anthropogenic materials, backed against an independent crystallinity reference based on infrared spectroscopy. Results are then used to assess the crystallinity of anthropogenic calcite in archaeological lime binders characterized by different states of preservation, including samples affected by the formation of secondary calcite, and tested on micromorphology thin sections in which lime binders are embedded in sediments.
人为方解石是通过烟火技术活动产生的一种碳酸钙形式，它是石灰粘结剂和木灰等材料的主要成分。由于形成过程不同，这种类型的方解石与地质成因的方解石相比，结晶度明显较低。方解石的结晶度可以通过透射模式的红外光谱法测定，该方法能够将粒度效应与原子有序性解耦，从而有效地区分人为成因和地质成因的方解石。相反，拉曼显微光谱法仍在为评估方解石的结晶度建立参考框架。在地质成因和人为成因的方解石的拉曼光谱中，谱带展宽已被确定为结晶度的指标之一。在此，我们分析了各种地质成因和人为成因材料中方解石谱带的半高宽，并以基于红外光谱的独立结晶度参考为依据。然后，将结果用于评估具有不同保存状态的考古石灰粘结剂中人为方解石的结晶度，包括受次生方解石形成影响的样品，并在石灰粘结剂嵌入沉积物的微观形态薄片上进行测试。
