文物岩石材料劣化两类结垢物质成分 及形成机制的分析与研究

为了探讨文物岩石材料劣化结垢病害的特征和形成机理,以洛阳龙门石窟和北京西黄寺清净化城塔塔基砂岩条石为研究对象,采用全岩化学全分析和X射线衍射测试技术对两类结垢物质的成分和形成过程进行了系统分析和研究。研究结果表明,龙门石窟的结垢物是在水长期渗漏过程中对碳酸盐岩溶蚀改造沉淀后而形成的;而西黄寺清净化城塔塔基砂岩条石上的结垢物来源于砌筑砂浆(其主要物质成分为方解石),白色结垢物的形成机理为,砌缝砂浆在水渗流作用下发生溶蚀,溶蚀形成的溶液流至其下砂岩条石上经沉淀及重结晶形成结垢物。     

Analysis of rock samples collected from rock hewn churches of Lalibela,Ethiopia using laser-induced breakdown spectroscopy

With the aim to study alteration processes of the rock hewn churches from Lalibela (Ethiopia), we applied Laser Induced Breakdown Spectroscopy (LIBS) technique to measure the elemental composition both of the bulk rock materials and their external layers, exposed to the environmental factors. The analytical plasma was generated by nanosecond pulses of an Nd: YAG laser emitting at 1064 nm. Different major and minor sample constituents were detected, including Ca, Mg, Na, Fe, Ti, Al and K. The detected O emission originates both from air surrounding and the sample, while the intensity of N lines, coming exclusively from air, was used for the LIBS signal normalization. By depth profiling of the weathered basalt rock, we observed a lower presence of K in the external layers, corresponding to the first 5 laser shots. The emission from this element is anti-correlated with the line intensities from O, and this was attributed to the variations in relative abundances of clay minerals and K-feldspar. The analogue measurements were performed on the tuff rock, and compared to the spectra from powder samples containing only the external soft material, scratched from the rocks. These analyses show an abundance of H in the weathered, wetted layers and suggest that cations are lost from the constituent primary minerals and replaced by H⁺; this process disrupts the lattice structure and causes a marked loss of strength. The studies presented here demonstrate that LIBS is a useful technique for studying the alteration processes in the rocks, caused by environmental factors.     

Rare encrusted lingulate brachiopods from the Cambrian–Ordovician boundary beds of Baltica

Vinn, O., December 2015. Rare encrusted lingulate brachiopods from the Cambrian–Ordovician boundary beds of Baltica. Alcheringa 40, xx–xx. ISSN 0311-5518

Encrustation is rare on late Cambrian and Tremadocian brachiopods of Baltica. The encrusting fauna is represented by a single taxon, Marcusodictyon. Only Schmidtites celatus is encrusted in the Furongian of Estonia. The Marcusodictyon–Schmidtites association is the earliest example of syn vivo encrustation and symbiosis from the Baltica palaeocontinent. The encrusting faunas of the late Cambrian and Tremadocian of Baltica were unusual presumably owing to palaeogeographic reasons because the other known examples of early encrustation originate from lower palaeolatitudes.

Olev Vinn [olev.vinn@ut.ee], Department of Geology, University of Tartu, Ravila 14A, 50411 Tartu, Estonia.     

White Encrustation Produced from Deer Antler Phosphate on Prehistoric Ceramics from Podunavlje

The composition and structure of the white pigments used in the encrustation paste on prehistoric ceramics is analysed and described. Encrustations, pigments and their use were studied chronologically, starting with their first appearance during the early Kostolac culture (3500–3000 bc , Copper Age), their very extensive use in the Vu?edol culture (3000–2500 bc , Copper Age) and their final disappearance with the Pannonian complex of Encrusted Pottery (2000–1500 bc , Bronze Age). Most of the Kostolac and Vu?edol culture material is from the Vu?edol and Vinkovci Hotel localities. The Pannonian culture material is from the Grabrovac (Ðakovo) locality. The encrustations were analysed by deep field optical microscopy, polarization microscopy, scanning electron microscopy with EDS, and XRD. Our investigation showed that from the very beginning to the end of the use of the encrustation technique in this area and by these cultures, the composition of the white paste was quite unique. The base material is produced by burning and powdering of deer antler. Crushed freshwater clam shells (Unio sp.) were a common addition to the phosphate paste.