In-situ microanalysis of Pb isotopic compositions using fsLA-MC-ICP-MS for the Tongyu copper deposit in the North Qinling Orogen and its geological significance

Pb isotopes are considered an ideal tool for identifying material sources and tectonic settings of various petrogeneses and mineralizations. A high precision method for in-situ Pb isotopic analysis by femtosecond laser-ablation multi-collector inductively coupled plasma mass spectrometry (fsLA-MC-ICP-MS) was first established in China by the State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University. This new method has been used to measure Pb isotopic compositions for inclusions, minerals, glasses, metals, etc., because of its negligible element fractionation and well-corrected mass discrimination. However, Pb isotopic studies on typical deposits using fsLA-MC- ICP-MS have until now rarely been reported globally. The Tongyu copper deposit in the Shaanxi Province, China is one of the most important VHMS deposits with industrial value and is also a typical example of mineralization associated with subduction and metallogenesis during the Caledonian orogeny in the western part of the North Qinling Orogen. Previous studies of this deposit have focused mainly on geological features and ore-forming ages, but detailed isotopic geochemical studies on the ore-forming material sources and tectonic settings were lacking.