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Zircon U-Pb dating, Lu-Hf isotopic and geochemical data for the Silurian rhyolites from the Loei fold belt are presented to constrain their petrogenesis and tectonic settings. The rhyolites give a weighted mean ~(206)Pb/~(238) U age of 423.7±2.7 Ma, and are characterized by high SiO_2, Al_2O_3, K_2 O and low MnO, MgO and P_2O_5. All samples are enriched in LILEs(e.g., Ba, K, Pb) and LREEs and depleted in HFSEs(e.g., Nb, Ta, Ti) with obvious negative Eu-anomalies(δEu=0.56–0.63). The calc-alkaline rhyolites are typical arc-related rocks. The Loei rhyolites have high A/CNK ratios(1.19–1.34) and positive εHf(t)(4.03–5.38), which can be interpreted as partial melting of juvenile crustal materials followed by multistage melting and differentiation, similar to highly fractional I-type rocks. Combined with regional geological surveys, the Loei rhyolites should be formed in a volcanic arc environment and may be in contact with the Truong Son fold belt during the Early Paleozoic. Moreover, the Simao Block might be in contiguity with the Indochina Block during Silurian.
Zircon U-Pb dating, Lu-Hf isotopic and geochemical data for the Silurian rhyolites from the Loei fold belt are presented to constrain their petrogenesis and tectonic settings. The rhyolites give a weighted mean (206) Pb / ~ 238 U age of 423.7 ± 2.7 Ma and are characterized by high SiO 2, Al 2 O 3, K 2 O and low MnO, MgO and P 2 O 5. All samples are enriched in LILEs (eg, Ba, K, Pb) and LREEs and depleted in HFSEs The calc-alkaline rhyolites are typical arc-related rocks. The Loei rhyolites have high A / CNK ratios (1.19-1.34) and positive εHf (t ) (4.03-5.38), which can be interpreted as partial melting of juvenile crustal materials followed by multistage melting and differentiation, similar to highly fractional I-type rocks. Combined with regional geological surveys, the Loei rhyolites should be formed in a volcanic arc environment and may be in contact with the Truong Son fold belt during the Early Paleozoic. Moreov er, the Simao Block might be in contiguity with the Indochina Block during Silurian.