Although gilt silver threads were widely used for decorating historical textiles, their manufacturing techniques have been elusive for centuries. Contemporary written sources give only limited, sometimes ambiguous information, and detailed cross-sectional study of the microscale soft noble metal objects has been hindered by sample preparation. In this work, to give a thorough characterization of historical gilt silver threads, nano- and microscale textural, chemical, and structural data on cross sections, prepared by focused ion beam milling, were collected, using various electron-optical methods (high-resolution scanning electron microscopy (SEM), wavelength-dispersive electron probe microanalysis (EPMA), electron backscattered diffraction (EBSD) combined with energy-dispersive electron probe microanalysis (EDX), transmission electron microscopy (TEM) combined with EDX, and micro-Raman spectroscopy. The thickness of the gold coating varied between 70-400 nm. Data reveal nano- and microscale metallurgy-related, gilding-related and corrosion-related inhomogeneities in the silver base. These inhomogeneities account for the limitations of surface analysis when tracking gilding methods of historical metal threads, and explain why chemical information has to be connected to 3D texture on submicrometre scale. The geometry and chemical composition (lack of mercury, copper) of the gold/silver interface prove that the ancient gilding technology was diffusion bonding. The observed differences in the copper content of the silver base of the different thread types suggest intentional technological choice. Among the examined textiles of different ages (13th-17th centuries) and provenances narrow technological variation has been found.
The thermal influence of a Miocene stratovolcano (Mátra Volcano) on its basement was studied by apatite and zircon (U–Th)/He thermochronometry. The pre-Miocene substratum of the volcano contains Mesozoic sedimentary units in addition to the nearby exhumed igneous Recsk Complex. The Oligocene emplacement age of the Recsk Complex is constrained by zircon U–Pb geochronology to be 29.6 Ma, which serves as a benchmark for the beginning of its thermal history. All measured apatite (U–Th)/He ages (19.9–5.9 Ma) and most of the zircon (U–Th)/He ages (26.2–17.7 Ma) are considerably younger than the emplacement age of the Oligocene Recsk Complex, implying thermal overprinting by the adjacent Miocene Mátra Volcano. The apatite and zircon He ages of the Oligocene complex increase from south to north, providing clear evidence of a northwards-weakening thermal overprint. The post-Oligocene thermal history of the basement was reconstructed via one-dimensional subsidence/thermal modelling. According to zircon He modelling, the thickness of the covering units above the Recsk Complex was estimated to be 1000–1500 m and the heat flux was
c.
200 mW m
−2
during the Miocene volcanism. Thermal modelling based on apatite He data suggests that the Miocene volcanism was followed by intensive erosion and the exposure of the Recsk Complex by the Late Miocene.
Supplementary material:
The locality, petrography and age yield of the dated samples of the Recsk Igneous Complex and details of the laser ablation inductively coupled plasma mass spectrometry dating of zircons from the Recsk Complex are available at:
https://doi.org/10.6084/m9.figshare.c.4127444
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