COMPARING IRON AGE SOFTSTONE ARTIFACTS WITH SAMPLES FROM ANCIENT QUARRIES IN THE SEMAIL OPHIOLITE, SOUTHEAST ARABIA: XRD MINERALOGY AND ELEMENTAL ABUNDANCES BY ICP-MS

The Semail Ophiolite in the al-Hajjar Mountains of southeast Arabia is rightfully considered the predominant source of carved softstone (aka serpentinite, steatite, soapstone or chorite) artifacts found at Iron Age archaeological sites along the Arabian Gulf coast. Yet exact source locations and mountain-to-coast transport paths for carved softstone are not well known. The present mineralogical and geochemical provenance study tests the feasibility of addressing two different archaeological sourcing questions. First, can softstone artifacts be separated into compositionally defined groups (that may have originated from different quarry sites)? Second, can mountain quarry localities be identified or eliminated as possible sources for carved softstone artifacts?

We analysed the mineralogy and major, trace and rare-earth element abundances of 20 Iron Age softstone artifact fragments. The artifacts were collected from two coastal archaeological sites (Muweilah and Hamriya) and one mountain site (Jebel Buhais), all within the Emirate of Sharjah, United Arab Emirates. A total of 38 rock samples from six separate quarry localities in the ophiolitic Hajjar Mountains also were analyzed. Previous mineralogical studies of carved softstone vessels from archaeological sites on the east (Oman Gulf) side of the Hajjar mountains describe two material types: talc-rich and chlorite-rich. All of the artifacts in our study would fall into the chlorite-rich category, with clinochlore and nimite being the predominant minerals. The serpentinized rock samples from the six localities where numerous small ancient quarries were present were more mineralogically variable, but generally could be lumped into talc-rich and chlorite-rich categories. Minerals present in these ‘talc' group include: birnessite, bementite, talc, clinochrysotile, antigorite and dolomite. Rock samples falling into the ‘chlorite' group were found less commonly; nimite and clinochlore were the most common minerals identified by XRD in these samples. Not surprisingly, higher Al concentrations characterize the major element signature of the chlorite-rich materials when compared with the talc-rich samples. The samples' chondrite-normalized REE signatures are generally consistent with those expected from ophiolitic parent rock, suggesting more regional groupings are possible.