The Study On Genesis And Prospecting Pattern For The Sijiaying Sedimentary Metamorphic Iron Ore, Eastern Hebei

The Sijiaying BIFs occurrenced in the Luanxian group. According to the existing exploration data, the main iron ore bodies are monoclinic output, tend to west, and local folds and faults are development. After repeated exploration, its cumulative iron ore resource can reach 3.2 billion tons. Based on field surveys and used of mineralogy, lithology, SHRIMP chronology, main and REE element analysis technology, this work has made in-depth discussions on metamorphic degree, geochronology, metallogeny. Then prospecting pattern is established by combined with the geological properties, metallogeny and geophysical feature of Sijiaying.The paper stared firstly metamorphic degree of Sijiaying area. This work collected garnet-bearing samples from representative iron deposits to carry out EMPA and X-ray powder diffraction analysis. It is concluded that the metamorphic degree deepen from south to north by amphibolite facies to granulite facie, as well as the unit cell parameters(a0) values decrease in Qianan-Luanxian area. SHRIMP zircon U- Pb dating shows that the formation age of Sijiaying BIF is late neo-archean(2537~2545Ma). Soon afte, the BIF suffered from migmatization and regional metamorphism. By collecting the age data of Archean supra-crustal and granitic magmatic rocks dated by predecessors in recent years, a conclusion can be drawn that the formation age of all the sedimentary metamorphic iron ores in Eastern Hebei Province belongs to late neo-archean period. As 2.5Ga tectothermal event was mainly divided into three event peak periods on the basis of age data statistics: 2530-2550 Ma is BIF formation peak period in Eastern Hebei Province, 2510-2530 Ma is the peak period for late Archean magmatic event, and 2500-2515 Ma is a wide range of regional metamorphism peak period, respectively. Research on genesis of deposit shows that quartz of high-grade ore is less than low-grade ore, whereas mafic minerals and altered mineral are more than low-grade ore. The trace elements and REEs distribution patterns of the high-and low-grade ore are identical, indicating that they may come from the same sources of hydrothermal and seawater. High-grad ore show higher ∑REE+Y content which close to REE patterns in hydrothermal. The late hydrothermal alteration is the important reasons for high-grad ore.Through the study of Sijiaying sedimentary metamorphic iron deposit, and conbined with the former study, this paper forms the metallogenic model. At last, a geologicalgeophysical model of Sijiaying iron deposit is established, based on the summary of the metallogenic geological conditions and the physical characteristics of region...