U-Pb ages and trace elements of zircons from Loei and Truong Son fold belts, northern Laos: Implication for porphyry deposit fertility

The Loei and Truong Son Fold Belts are well known as highly mineralized magmatic arc-related terranes in Southeast Asia. Zircon LA-ICP-MS studies provide U-Pb ages and magmatic fertility using trace elements of felsic to intermediate volcanic and plutonic rocks from ten prospects in the Loei and Truong Son fold belts, NW Laos region. The geochemical and geochronological analyses suggest at least three episodes of magmatism occurred in the region: Silurian-Devonian (434-411 Ma), Early to Middle Permian ( 299- 277 Ma), and Late Permian to Middle Triassic ( 253- 243 Ma). Key trace elements and ratios together with oxygen fugacity of magmas (e.g., Eu/Eu*, Dy/Yb, Ce/Nd,.FMQ) imply that the Phu Kham and the West of Vientiane area along the Mekong River are likely to be fertile for porphyry copper deposits. In contrast, the Pha Gnai and the other suites are less fertile. Therefore, zircon as a fertility indicator is a valuable tool to distinguish fertile magmatic suites from the barren suites in this area.