METHODOLOGIES FOR SOURCE ATTRIBUTION USING COPPER AND LEAD WITHIN RED INCLUSIONS OF TRINITITE

Investigating post-detonation material (PDM) from nuclear explosions is one route to source attribution because these samples can contain device components. Historical PDM from nuclear testing can be used to develop methodologies for this purpose if the chemical and isotopic components of the device are known. Trinitite, a PDM formed from the world’s first nuclear detonation on July 16, 1945, is glassy material resulting from the melting of arkosic sand at the detonation site (White Sands Missile Range, Alamogordo, NM) and the device components. A rare type of Trinitite contains red inclusions that have extremely high amounts of lead (between 2,000 and 25,000 μg/g) and copper (between 500 and 12,000 μg/g) that are in general positively correlated. Red inclusion areas were analyzed for their lead isotope compositions via laser ablation multi-collector- ICP-MS. The Pb isotope ratios exhibit a large variation, which indicate mixing of Pb from 3 different sources: the natural geological background (arkosic sand); an anthropogenic component from the device; and Cu used for wiring in the device. Based on the Pb isotopic ratios for areas with the highest concentrations of Pb, it is likely that the anthropogenic Pb originates from Buchan’s Mine (Newfoundland, Canada). To determine the source of the industrial Cu used in the device, Cu samples produced from mines (Keweenaw Peninsula, MI and Bingham Mine, UT) that were the main producers of Cu during the 1940’s were analyzed for their trace element and Pb isotopic compositions The combined trace metal abundances of Pb, Zn and Cu and Pb isotope compositions for the industrial Cu samples and red inclusion areas of Trinitite suggest that the Cu wiring used in the device was sourced from both the Bingham and Keweenaw Cu ore deposits. The chemical and isotope results from our investigation indicate that important insights can be gained about the manufacturing history of metal components used in a nuclear device, which will greatly enhance the likelihood of accurate source attribution.