Recognition of a ca. 130 Ma Makeng-Yangshan iron skarn belt in the Southeastern China: evidence from garnet in situ U-Pb geochronology

A number of iron ore deposits and occurrences are distributed along the southeastern China coast, and they constitute an important Fe metallogenic belt in South China. However, the genesis of this belt remains poorly understood. Here, we present in situ U-Pb laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) ages of garnet from three Fe skarn deposits (Makeng, Luoyang, and Yangshan) to constrain the timing and the genesis of the Fe mineralization. Electron microprobe analyses of garnet in association with magnetite indicate a composition within the grossular-andradite solid solution series. Garnet from two Fe skarn ore samples in the Makeng deposit (430 Mt @ 41.60% Fe) in the western part of the belt yielded two U-Pb ages of 132.9 +/- 0.9 Ma and 131.4 +/- 1.2 Ma, respectively. Garnet from the Luoyang Fe skarn deposit (14.4 Mt @ 42.44%Fe) in the middle part of the belt yielded ages of 130.7 +/- 0.7 Ma and 131.8 +/- 1.4 Ma, and garnet from two ore samples in the Yangshan Fe deposit (37.1 Mt @ 42.82% Fe) in the eastern part of the belt yielded similar U-Pb ages of 130.0 +/- 1.2 Ma and 132.8 +/- 0.9 Ma. The consistent ore-formation ages, similar geological characteristics, and close spatial distribution of these Fe skarn deposits indicate that they constitute a newly recognized ca. 130 Ma Fe skarn metallogenic belt in South China. The garnet ages are in general agreement with the crystallization ages of their associated granitic rocks. The ca. 130 Ma iron skarn belt at the southeastern China coast formed simultaneously and in parallel NE-trending alignment with the Handan-Xingtai Fe skarn deposits in the central North China craton and the Middle-Lower Yangtze River Valley (MLYRV) iron-oxide apatite (IOA) and skarn deposits at the northeastern margin of Yangtze Craton in the northern part of Eastern China. Together, these three ca. 130 Ma Fe metallogenic belts in eastern China constitute an important component of the Cretaceous post-subduction tectono-magmatic Cu-Au-Mo-Sn-W-Fe metallogeny along the eastern Asian continental margin.