Zircon U-Pb dating and Hf isotope of the felsic dykes in the Longshan Au-Sb deposit in Central Hunan Province and their geological significance

This study presents a systematic geochemistry, zircon U-Pb dating and Hf isotope analysis on the felsic dykes outcropped around the Longshan Au-Sb deposit, aiming to constrain the intrusion ages, nature of sources and the tectonic setting of these felsic dykes and provide some new insights on the genetic relationship between the Longshan Au-Sb mineralization and magmatism. Zircon U-Pb dating results show that the felsic dykes occurred in five different locations around the Longshan Au-Sb deposit yield the same crystallization ages of 220 similar to 217Ma (Late Indosinian). The Hf isotopes of the felsic dykes show the nearly identical characteristics with Hf-176/Hf-177 ratio of 0.282264 similar to 0.282536, epsilon(Hf) (t) = -13.4 similar to -3.7, t(DM2) of 2089 similar to 1482Ma. Combining with the elements geochemical characteristics, it suggests that the felsic dykes may have derived from the partial melting of the Paleoproterozoic-Mesoproterozoic meta-sedimentary under a post-collision extensional tectonic setting. The intrusion ages of the felsic dykes are roughly consistent with the ore-forming age of the Longshan Au-Sb deposit, implying that deep-seated magmatism under the deposit may have supplied the part of mineralization hydrothermal fluid components and heat based on the previous studies.