Geological Characteristics And Metallogenic Regularities Of Sangyuan Iron Deposit In Miyun County, Beijing

The Sangyuan iron deposit is one of Jidong-Mihuai ore concentrated area in the North China platform. The genetic type of the deposit is the famous Algoma-type in the world. This paper is on the basis of geological survey, drilling engineering and petrography, with the results of the forerunners. The article introduced the geological characteristics of the deposit, and analyzed it’s metallogenic regularities. And made a prediction for the surrounding and deepth of the mining area by the magnetic data. The main results are as follows:1.Sangyuan iron deposit occurred in the Dacao formation of Miyun group. The rocks outcropped in Sangyuan iron deposit are biotite plagioclase gneiss, biotite pyroxene plagioclase gneiss, garnet pyroxene plagioclase, biotite monzogneiss and magnetite quartzite. Some small faults and folds disproportionately affected the shape and distribution of the ore body. The ore bodies are bedded or lenticular, extends northeast. The main texture of ore is granular crystalloblastic and the structure is banded or gneissic. The deposit is controlled by the Gaoling-Xihenghe compound syncline because it is located at the southeast wing of the fold.2. The occurrence of ore beds are consistent with their surrounding rocks and it’s distribution is controlled by the stratum. The deposit formed in the Mesoarchean, with the metallogenic age of more than 2800 Ma.It has been revamped by regional metamorphism from amphibolites facies to granulite facies. The enriched garnet can be take for natural marks when drilling near the top or bottom of the ore bed.3.The metallogenic type of Sangyuan iron deposit is volcanic-sedimentary metamorphic type. It was formed in the stable basin far away from the volcanic center. And the volcanic activity provided the necessary metallogenic materials. The metallogenic model of the deposit can be summarized as follows: The active volcanoes in the deep sea bursted some thermal fluid with rich iron and silicon. When the chemical balance of the sea water changed, the silicon deposited and formed the silicon layer. Lately,the iron was carried up to the shallow sea by upwelling currents, and the Fe2+ were oxidized to be Fe3+ in this process. The Fe3+ deposited and the iron layer formed. During the period, the ore formed the banded structure by the seasonal upwelling currents.4.The results of Ground magnetic survey shows that there is an obviously magnetic anomaly area on the southeast side of Sangyuan area. The magnetic abnormal is probably caused by magnetite quartzite. It can be the next prospecting target area. According to the results of magnetic well logging in ZK170-1 drilling hole, we made a magnetic well logging map. On the map, the △ Z line is negative at the end and the △ T’ line is just on the opposite. These show that there is no prospective ores in the deep of the mining area.