In order to investigate the genesis of the iron-phosphorus(Fe-P)deposits hosted in the Archean met-amorphic series in Northern Hebei-Western Liaoning,we carried out petrographic,geochronological,and geo-chemical studies on the typical Zhaobinggou deposit.Field observations show that the so-called"the banded Fe-P ore"is hosted as veins in the biotite-hornblende-plagioclase gneiss,and is characterized by the gneissic schistosity with cross-cutting Fe-P veins.The formation of the vein folds is associated with the post tectonic deformation.Zircons in the Fe-P-bearing biotite-hornblende-plagioclase gneiss are intergrown with the Fe-Ti oxides and apatite.Cathodoluminescence imaging of these zircon grains shows no or weak zoning or patchy tex-ture,which is typical of mafic magmatic origin.Zircon U-Pb dating using LA-ICP-MS technique obtained a weighted average age at(282±3)Ma(MSWD=0.78),which constrains the Fe-P mineralization to be in the early Permian,rather than Neoarchean as supposed previously.Comprehensive comparison studies show that the geochemical characteristics and the ore-forming age of the Zhaobinggou Fe-P-bearing biotite-hornblende-plagioclase gneiss are similar to those of the regional mafic pyroxenite-hornblendite,which is considered as the parent rock of the Fe-P mineralization.The results indicate that the Zhaobinggou Fe-P deposit is associated with Phanerozoic Alaskan-type mafic-ultramafic magmatism along the Hongshila-Damiao fault zone,but not re-lated to any metamorphism as reported previously.Further investigations are needed for revealing the genesis of other similar deposits.
关键词
铁磷矿床/成矿年龄/矿床成因/阿拉斯加型岩体/华北克拉通
Key words
Fe-P deposit/ore-forming age/ore genesis/Alaskan-type complex/North China Craton
维普
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