蓟县剖面中元古界下马岭组地层下部黑色岩系中发现丰富的铁质结核,经X射线粉晶衍射、显微镜下观察、能谱分析等方法鉴定,确定铁质结核主要由菱铁矿构成。这些菱铁矿可能具有经济意义。另外,野外和室内研究表明,无论是铁质结核还是黑色岩系本身,都匮乏硫化物。这一发现说明中元古代下马岭期的燕辽海盆水体贫氧、富铁、贫硫,不是硫化的海洋。 Rich iron nodules were found in the lower part of the Lower Malay Formation stratum in the Jixian section and were identified by X-ray powder diffraction, microscopic observation and energy spectrum analysis. The results showed that the iron nodules were mainly composed of siderite . These siderite can be of economic importance. In addition, field and laboratory studies show that sulphides are scarce in either the ironic or the black rock series themselves. This finding shows that the Yan-Liao basin water of the Mesoproterozoic Lower Maling Ridge is depleted in oxygen, iron and sulfur, and is not a sulfide sea.