Ion Beam Analysis applied to lapis lazuli rocks and archaeological findings: new expansion and application of a scientific procedure for the material provenance investigation
The main aim of this PhD project is to expand and improve the methodologies for lapis lazuli provenance investigation via the application of non-invasive atomic and nuclear techniques:
the Ion Beam Analysis (IBA). The study of the provenance of the raw lapis lazuli used to carve precious artefacts (such as jewels, amulets, seals, inlays) in the ancient Middle East, Egypt, Central and Southern Asia is one of the main line of research of the group since 2008;
it led to the realization of a provenance protocol [Lo Giudice 2017] that takes into account 4 quarry districts as possible source of lapis lazuli used in antiquity: Badakhshan (Afghanistan), Liadjura-Dara (Pamir Mountains, Tajikistan), Lake Baikal (Siberia), Coquimbo region (Chile).
Recently, a fifth possible origin, Mogok (Myanmar) has been added. When studying an archaeological finding, the provenance attribution is achieved via the search of characteristic markers in the lapis lazuli rocks (such as peculiar trace elements or luminescence features) that can ultimately be related with a specific geological source.
So far, the markers were identified inside diopside and pyrite mineral phases by using Proton Induced X-ray Emission (PIXE) and Ionoluminescence (IL) and they were successfully adopted in some interesting case studies , such as the study of the Egyptian treasure of Tôd, conserved in Louvre Museum (France) [Calligaro 2014].
However, some ambiguities still remain in the protocol, especially regarding the Myanmar origin.
The identification of new provenance markers could be helpful not only in the resolution of this specific issue but also in the more general analysis of archaeological objects with a travelled conservation history: an approach with multiple independent markers is crucial for a correct provenance attribution.
Moreover, a deeper investigation of the material is fundamental in view of including new possible lapis lazuli sources in the protocol. From one hand, the markers will be searched inside other widespread minerals in lapis lazuli (calcite and K-feldspar) with PIXE and IL;
from the other hand, IBA techniques never used before in this topic, Particle Induced Gamma-ray Emission (PIGE) and Rutherford Backscattering Spectrometry (RBS), will be adopted to gain complementary information regarding light elements concentration and layer structure of the material, respectively.
Together with the high sensitivity and the possibility to be simultaneously applicable with the same proton probe at few MeV, IBA have the great advantage of being implementable also in air, other than in vacuum, allowing a completely non-invasive approach on precious fragile objects.
Finally, the proposed methodologies will be applied to the analysis of unique archaeological findings from different ancient sites (VI-III millennium BC) in an area spreading from Oman to Pakistan and belonging to different civilization: Jiroft Culture, Shahr-i Sokhta, Indus Valley and others.
The majority of the data will be acquired at the AN2000 accelerator line at the Legnaro National Laboratories of the National Institute of Nuclear Physics INFN-LNL in the frame of ALCHIMIA project and at the NewAGLAE accelerator facility of the Louvre Museum (Paris, France) with the SIBILLA project, developed via the international IPERION CH/IPERION HS programmes.
In the figures are shown respectively:
[1] Map of the approximate diffusion area of lapis lazuli in ancient time (IV-I millennium BCE). The blue circles are documented quarries; the red squares are hypothetical sources whose existence has not been proven; the pink star is the 1rst documented site where lapis lazuli was used (Mehrgarh, VII millennium BCE).
The yellow point the Shahr-i Sokhta site, an important working center for lapis lazuli. Ovals area represent the area of ancient civilizations where lapis lazuli archaeological objects have been found;
[2] lapis lazuli working fragments from the Shahr-i Sokhta site (Iran, III millennium BCE)
[3] Measurements at the NewAGLAE accelerator facility of some lapis lazuli beads from an Indus Valley Civilization site in Pakistan.
