Towards <i>in-situ</i> U–Pb dating of dolomites

Recent U–Pb dating by laser ablation ICP-MS has demonstrated that reasonable precision (3–10 % 2σ) can be achieved for high-resolution dating of texturally distinct calcite phases. Absolute dating of dolomite, for which biostratigraphy and traditional dating techniques are very limited, remains challenging but may resolve many fundamental questions related to the timing of mineral-rock formation by syngenetic, diagenesis, hydrothermal, and epigenetic processes. In this study we explore the possibility of dating dolomitic rocks via recent LA-ICP-MS dating techniques developed for calcite. The in-situ U–Pb dating was tested on a wide range of dolomite rocks of various origins (i.e., syngenetic, early diagenetic and epigenetic) from the Cambrian to Pliocene age – all of which from well-constrained stratigraphic sections in Israel. We present in-situ U–Pb results of dolomitic rock samples, together with imaging techniques and chemical characterizations. We show that dolomite dating is highly sensitive to textural differences and highlight parameters such as crater morphology and roughness, calcite zoning and impurities that may affect the interpretation of the resulted ages. Textural examination indicates zonation and mixing of different phases at the sub-millimeter scale (

Minero-Petrographic Characterization of Chianocco Marble Employed for Palazzo Madama Façade in Turin (Northwest Italy)

The study of ancient marble plays an important role in the interpretation of historical and archaeological sites and gives interesting information about building materials used in ancient times and their trade routes. The present work focuses on Chianocco marble that represents one of the most important ancient white marbles for cultural heritage exploited in the Piedmont region (Northwest Italy) and employed for the Palazzo Madama façade. A multi-analytical study based on petrographic (optical and scanning electron microscopy), electron microprobe, cathodoluminescence and stable isotope analyses was carried out on these marbles in order to perform an archaeometric study. Chianocco marble was used in Turin during the baroque era by the Savoy architect Filippo Juvarra (1678–1736) in historical buildings, such as the façade of the Palazzo Madama, the plinth of the façade of the town Cathedral and the columns (now plastered) of the portico of Piazza San Carlo. This stone is a dolomitic rock belonging to the Mesozoic cover of the Dora Maira Massif (Pennidic Unit). It shows a vuggy fabric characterized by a vacuolar texture due to tectonic brecciation and subsequent selective dissolution during subaerial exposure. This kind of research is useful to highlight the importance of the use of local stones as building materials and to investigate stone materials for the restoration and maintenance of historical buildings.