The Hong'an block is an important component of the Dabie-Sulu orogenic belt. Studying its high-pressure/ultrahigh-pressure metamorphic rocks can provide valuable insights into the tectonic evolution of this orogenic belt. Three types of garnet amphibolite, exposed in northern Macheng of the Hong'an block, were selected for zircon U-Pb isotopic dating and geochemical compositions of zircon and whole-rock. In this study, ages of the metamorphism and protolith rocks and nature as well as the tectonic evolution context are discussed. Zircon U-Pb isotopic dating results reveal two age peaks (244-240 Ma for metamorphism and 817-772 Ma for formation of the protolith rocks). Rock sample LH1 exhibits low silicon content (SiO2 = 44.42 wt.%–49.29 wt.%) and high aluminum content (Al2O3 = 15.36 wt.%–16.31 wt.%), with a rare earth element (REE) distribution pattern similar to that of E-MORB. Rock sample LH2 shows relatively high SiO2 content (48.47 wt.%–52.49 wt.%), with a REE pattern being enriched in light REEs (LREEs). Rock sample LH3 displays geochemical characteristics of high silicon content (SiO2 = 56.60 wt.%–57.47 wt.%) and low aluminum content (Al2O3 = 13.51 wt.%–14.25 wt.%), enriched in large ion lithophile elements (LILEs) and depleted in high field strength elements (HFSEs), similar to that of continental arc andesite (CAA). Based on these resutls, the eclogites exposed in northern Macheng record middle Triassic metamorphism and preserve evidence of the Neoproterozoic thermal event in their protoliths. The protolith of sample LH1 is likely basalt forming in a back-arc basin and those of samples LH2 and LH3 are likely juvenile crustal rocks of the Yangtze block. The Hong'an block underwent detachment and exhumation of the subducted continental crust after the formation of a back-arc rift basin along the Yangtze block in the Neoproterozoic and Triassic continental thrusting during the Dabie orogeny.