The Characteristics Of Melt-fluids And Genesis Of Xishimen Iron Deposit In Wuan,Hebei

The Handan Xingtai Area is a major iron ore base,belonging to the central north China craton,south-central segment of Taihangshan intraplate orogenic belt.The Wuan Area is the centre of Handan Xingtai Area which hold the most iron deposit and the largest scale.Xishimen Area locates in Wuan depression,west of Taihangshan orogenic belt,east of North China Plain,develop NNE-orientated structure.The Xishimen iron ore,because of its large scale and quantity of iron ore,is considered to be a typical case of the Handan-Xingtai-type iron ore.Not only has the characteristic of skarn deposit,the Xishimen iron deposit also has the characteristic of ore magma type iron deposit.There are a certain amount of skarn ore around Ore body of Xishimen iron deposit,wall-rock was general albitization,minerals caused of metasomatosis were banded or spiderweb.The main ore body has a clear boundary with wall-rock,which were rotelliform or quasi-bedded.The alteration of wall rock was simple,the degree of alteration is slight.Block,breccia,porosity,almond-shaped ore structure development.The magnetite produced in melt of high temperature has the texture of allotriomorphic,they are produced with diopside and tremolite,which rich of Si.REE distribution pattern is flat type,Ce and Eu have no obvious abnormity;The magnetite produced with phlogopite has the texture of allotriomorphic or hypidiomorphic,Ce and Eu have no obvious abnormity,its trace element rich of Pb,loss Zr and Nb.The magnetite produced in fluid of low temperature has the texture of automorphic or hypidiomorphic,coexist with calcite,steatite and pyrity,which has a low quantity of Si,REE distribution patterns are right deviation,which is rich of light REE,Ce and Eu have no obvious abnormity,its trace element loss large ion lithophile element Sr and Ba.Diopside grew with magnetite have composition of bang,core rich of Fe,edge rich of Mg.The REE distribution pattern is right deviation,which is rich of light REE,Ce is positive anomaly,Eu is negative anomaly obvious.The REE distribution pattern of phlogopite show that Ce is intense negative anomaly,Eu is positive anomaly obvious,its trace element rich of Hf,loss Th.The REE distribution pattern of calcite become left deviation,while magnetite is right deviation,may mean that calcite was produced in late fluid.The genesis of Xishimen iron deposit would be this: the iron-enriched intermediate-basic magma react with limestone,make the composition of primitive magma change,produce abundant fluid,silicate magma via liquation produce iron ore magma,abundant fluid make iron ore magma become ore-bearing melt-fluid flow,because of fluid overpressure,ore-bearing melt-fluid flow intruded upward along magma conduit,iron ore magma mineralize when it rise to the place that magma rock mass contact with wall rock.