Analytical Study of Lead Isotope Signatures for Provenance Determination of Smuggled Lead-Zinc Ore in South East Nigeria

Illegal export of lead-zinc ore from South East Nigeria constitutes a major revenue loss and security concern, yet forensic tools for ore provenance determination to support enforcement actions have not been developed for Nigerian mineralisation contexts. This study applies lead isotope geochemistry to develop a provenance fingerprinting system for lead-zinc ore from major deposits in Ebonyi and Cross River states. Reference ore samples were collected from 12 locations across known mineralised zones at the Enyigba, Abakaliki, and Afikpo deposit clusters. Lead isotope ratios (206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb) were determined by multi-collector inductively coupled plasma mass spectrometry on galena separates from each sample. Discriminant analysis was applied to the isotope ratio dataset to develop deposit-specific provenance fields. The provenance model was validated by blind testing of 24 ore samples of known origin. Validation results indicate correct deposit assignment in 88 percent of test cases using the combined isotope ratio discriminant model. Lead isotope data are supplemented by trace element geochemistry to improve discrimination between closely adjacent deposits. The study provides forensic evidence capability that can be used by the Nigerian Customs Service and security agencies to assign confiscated ore to specific source deposits, supporting prosecutions and improving understanding of smuggling networks. Keywords: lead isotope, provenance, smuggling, lead-zinc ore, forensic geochemistry.