The Characteristics Of Fushan Iron Deposit, Handan, Hebei Provience, China, And Its Implication To The North China Craton Evolution

The Fushan iron deposits as one of the major typical skarn-type deposits arelocated in Hanxing area, southern Taihang mountains. It was formed in the boundarybetween hornblende diorite intrusion and mid-Ordovician limestone.This paper analyzed the isotopic data of U and lead for zircon mineral of thehornblende diorite and the results yield the ICPMS zircon U-Pb ages of2527±42Ma;Extensive hornblende diorite intrusions in Fushan deposits, Zircon ICPMS U-Pbdating yields the ages of128±2.5Ma, some of ages are2355±35Ma, with thechracteristics of inherition. ICPMS zircon U-Pb age of128±2.5Ma represents the timeof the diorite emplacement, and the ages of2355-2527Ma can indicated that the lowercrust were probably formed in Neoarchean. Additionally, the U-Pb age of the twozircon from gneiss xenoliths and the strata of Archean Zanhuang group were2464±27Ma and2535±71Ma, respectively, and display the fact that the age of hornblendediorite is consistant with the inherited zircon age. This shows that the hornblendediorite re-capture the Archean rocks when the ore-controlling rock emplacement ofthe process. The different group of ages recorded the formation of the North ChinaCraton and Mesozoic magmatic events, respectively. These are two major geologicalevents.The isotopic data of sulfur and lead for magnetite ore of the deposits are indicatedthat discussed in further the ore source by comparison with intrusions and strata. Thesulfur of the ore is from the deep source of sulfur mixed with crustal sulfur. The leadmainly from the orogenic magmatism, and with the relevant of magmatism, the mainsource originated from lower crust and mixed with a few from the mantle, and notethat the close relationship between mineralization and intrusive rocks and orogenicprocess.The helium and argon isotope characteristics of pyrites from iron deposits inFushan area are indicated that the source of ore-forming materials was from crust.There only0.12~4.96%of helium from mantle in ore-forming fluids.Based on the theory of minerageny and electron microprobe analysis ofindividual magnetite from the orebody in the iron deposits, it is suggested that magnetite is not only related to the skarn, but also affected by diagenism.The fluids inclusions experiments shows that the magnetite ore minerals and theskarn minerals (Epidote and Garnet) have the same decrepitation temperature(between410℃and430℃). They all belong to the mid-high stage of fluid evolution(the decrepitation temperature of magnetite is between452~532℃).The skarn stage has the typical characteristic of the mid-high density (between0.7~0.9g/cm3) and the homogenization temperature is between350℃and500℃.The fluids salinity declined from skarnism to carbonization. The evidence of the fluidinclusions shows that the depth of ore-forming is between5and7km. All thesecharacteristics can indicated the skarn mineralization.We conclude that: the material source of ore deposits in Handan Fushan irondeposit is mainly from lower crust, with the melting of lower strata of Zanhuang. Inaddition, a small amount of mantle-derived substances involved in mineralization;Two different ages of zircon from ore-forming rocks were recorded the time offormation and destruction of the North China Craton.