The Longqiao iron deposit is a large stratabound skarn type iron ore deposit in the Luzong ore district. Identification of the ore formation is important for the research and exploration, but distinguishing between two possible host units (Luoling and Dongmaanshan Formations) is controversial. The host formation at Longqiao is marl, brecciated limestone, dolomite, argillaceous siltstone and quartz sandstone, with a thickness of 20-150 m. We collected sandstones from the Luoling Formation outside the deposit and a unit of uncertain stratigraphic affinities about 5 m above the orebody. Using detrital zircon U-Pb chronology we found that there were significant differences in zircon concordant ages of the sandstones from the two locations. Zircon concordant ages of sample LQWW from the Luoling Formation outside the deposit are in the range 166.0 ± 1.4Ma to 3842.6 ± 6.5Ma; zircon concordant ages of samples from the unit hosting the orebody are in the range 262.1 ± 3.2Ma to 2589.8 ± 15.0Ma (ZK109), 261.8±1.9Ma to 2520.1±11.1Ma (ZK309), 264.6 ± 2.0Ma to 2947.2 ± 51.4Ma (ZK007) and 257.1±1.9Ma to 2717.0±21.0 Ma (ZK1603). These data and their age distributions indicate that the unit hosting ore at the Longqiao deposit differs from the Luoling Formation outside the deposit, and we infer that the host unit is not part of the Luoling Formation and probably belongs to the Dongmaanshan Formation. Combining with the recent exploration achievement, it is proposed that the north part of Luzong basin is a good district for looking for Longqiao type deposit.