In situ analysis of white marble from the Mediterranean Basin by LA-ICP-MS: inferences on provenace based on trace-element profiles

White marble is a carbonate dominant metamorphic crystalline rock used for more than 5000 years (late Neolithic – Cycladic civilizations) for statuary and architectural elements. The remarkable value taken on during the history is proved by the large and continuous use of this rock in the ancient societies. So far, numerous studies have set out to determine the provenance of white marble exploited from the main quarrying sites of the Mediterranean basins. These studies led a large number of data, which are partial and not always satisfactory from a scientific point of view. Actually, white marble of archeometric interest is largely characterized through minero-petrographic studies and isotopic signatures, primarily carbon, oxygen and strontium. A complete description of the geochemical composition, aimed at an exhaustive provenance study, is still missing. The application of the Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) permits the measurement of a large number of trace elements. The scope is to improve the limited existing database on the trace-element profile of white marble. The comparison of the concentration of these elements among different quarrying districts aims to identify geochemical markers as fingerprints of several white marble sites. With these assumptions, one can start to go deeper into the problem, surveying all the bibliography, the state of the art and general knowledge about this rock, i.e., its history, geology, geochemistry and archaeometry. The specimens considered come from a collection of white marbles chips, collected from the past sampling campaigns of La Sapienza University of Rome and IGAG-CNR of Rome, and largely analyzed by means of several analytical techniques in previous research works (i.e., stable isotope concentrations, EPR intensities, petrographic observations). The sampling is composed of about 120 white marble samples from nine different quarrying areas (i.e., Carrara, Paros, Penteli, Afyon, Göktepe, Naxos, Thasos, Thiountas and Proconnesos) and eight archeological samples of known attribution to test the feasibility of the method. This Ph.D. thesis is based on a multi-analytical approach and it can be divided in two phases. The first one consists of a systematic minero-petrographic characterization of a selection of the geological white marbles of known provenances, in order to identify the occurrence of minero-chemical markers discriminating different quarrying districts. The second step provided analyses on rock samples from different quarries of the Mediterranean area and archeological samples from the Casa di Augusto (Palatine Hill) and Musei Capitolini collection by means the LA-ICP-MS. The analyses have been conducted at the Laboratory of Inorganic Chemistry of Eidgenössische Technische Hochschule (ETH) of Zurich and at the laboratory of CNR-Istituto di Geoscienze e Georisorse, U.O.S. of Pavia. The goal of this study is to fulfill a database, gathering the more significant features of the proposed minero-petrographic and geochemical markers. The multidisciplinary collaboration among the different competences (geologists, chemists, conservation scientists) is fundamental to carry out this study, and this mutual collaboration is an integral part of the present Ph.D. thesis. Going in more detail into the structure of the work, the present thesis provides: 1) an overview on the use of white marble throughout the centuries and civilizations, and the state of the art about previous studies of provenance focused on white marble; 2) the description of the geological settings of the areas where the white marble considered were sampled, presenting also the history of the main quarries; 3) a brief description of the geological samples here analyzed and the experimental setup employed; 4) the results on the quarried samples; 5-6) a discussion and conclusion, with some proposals for future improvements. Finally, in the Appendix are presented the geochemical results of archeological samples.