Study On Enrichment Characteristics Of Heavy Rare Earth And Genesis Of Zudong Deposit In Southern Jiangxi

Rare earth has the name of"monosodium glutamate in industry",heavy rare earth has higher value,it is not only rare but strategic resource.The Zudong deposit is the only heavy ion adsorbed heavy rare earth deposit in the world.It is far-reaching to study the enrichment characteristics and formation process of heavy rare earth.The main research object of this paper is the Zudong granite body.On the basis of comprehensive analysis of geological characteristics,metallogeny and source of ore-forming materials of Zudong deposit,etc.Understanding the geological characteristics of the weathering crust of Zudong granite through detailed field geological work.Knowing of stratification of the weathered crust of the granite,the division of weathering intensity and the discrimination of weathering types;And by means of petrology,mineralogy,chemical composition analysis and other experimental methods,The chemical composition characteristics of adjacent rock mass,rare earth elements of weathering crust and the influence of structural alteration on the chemical composition of granite are studied respectively.Study on the characteristics of heavy rare Earth enrichment in Zudong Deposit,and preliminary study on the Genesis of heavy rare Earth enrichment.After the above work,the following awareness is obtained:?1?The chemical composition characteristics of Zudong granite show that:HREE enrichment and the mean?REE content is 100.96?g/g.0.39,0.01and 0.41 is average value of L/H,?Eu and?Ce.All of them showed negative anomalies;besides,Peripheral Cretaceous system,JurassicSystem and Cambrian system with their?REE are131.49?g/g,182.37?g/g and 263.60?g/g;L/H are 8.89,10.33 and 10.74;?Ce are0.88,0.58 and 0.59,respectively.All of them showed negative anomalies.?2?Effect of weathering on rare Earth characteristics of Zudong Granite:Influence of weathering intensity:The weathering crust of Zudong granite shows obvious left inclination and"seagull type"with EU anomaly;In the weathered crust,the HREE is mainly enriched in the completely weathered layer,and the sample L/H profile decreases from top to bottom,indicating that HREE is relatively enriched in the lower part of the weathered crust profile.Effects of weathering types:In the samples of different weathering types in Zudong,the?REE in red loose granite is relatively high,with an average value of308.70?g/g,L/H=0.54,showing a significant HREE enrichment,?Eu=0.01 and?Ce=2.54,showing negative Eu anomaly and positive Ce anomaly.There was a positive correlation with Fe₂O₃ content and L/H value in granite with low Fe₂O₃content.The HREE is relatively enriched in granite,and the same rule appears in the half-pit rock mass;at the same sampling point in the zudong rock mass,There was a positive correlation between the Fe₂O₃ content and?REE value,and the?REE value was relatively high in the samples with high Fe₂O₃ content.?3?Influence of structural alteration on rare Earth characteristics of Zudong rock mass:The influence of EW strike on large fracture alteration zone:The content of Al₂O₃ and K₂O increases with the increase of granite alteration strength.The content of Al₂O₃ in the three samples arranged from the center of the altered belt to the edge granite are 13.64,13.13%and 12.96%;and the content of K₂O are 4.79%,4.38%and4.38%;The content of Fe₂O₃,CaO,MgO and SiO₂ has no obvious change;SiO₂accounts for most of the rocks,76.66%and 76.65%,77.38%,respectively;The content of Rb,Th,U,Nb,Ta,Yb,Zr,Hf,Lu in trace elements increases with the increase of alteration,The content of Nd and Sm decreased with the increase of alteration;The whole rock in the fault-altered zone shows HREE enrichment characteristics.The EU and Ce negative anomaly is obvious and the REE distribution curve is left-tilted"seagull type".The trend of REE distribution curve of the three elements is basically the same;?REE are 299.91?g/g,337.77?g/g and 326.48?g/g,L/H are 0.32,0.44 and 0.43,and?Ce are 0.48,0.65 and 0.27,respectively.The decrease of L/H,La _N/Yb_N decreases with the increase of alteration strength,which indicates that the faulted alteration enriches the HREE of Zudong granite.Influence of alteration profile characteristics of small faults:In the constant elements,the content of SiO₂ in the fracture alteration zone profile of the Zudong rock mass and the half-pit rock mass increases with the increase of the alteration effect,The center of the alteration zone can be more than 80%.The content of Al₂O_3,K₂O,Na₂O and Fe₂O₃ decreases with the increase of alteration effect;The content of different SiO₂ in Fukeng rock body decreases with the increase of alteration,and the lowest is the green center hydromica sample wirh 68.65%.The content of Al₂O₃,CaO,Fe2O3,K2O and MgO decreases with the increase of alteration strength,and the lowest is the green central hydromica sample,the content of which are 19.30%,0.07%,2.33%and 0.43%,respectively.Trace elements in the fracture alteration zone of the half-pit rock mass of the Zudong rock body,the content of U,Nb,La,Yb,Sr,Nd,Sm,Y,Lu increases with the enhancement of the alteration effect in the section of the fracture alteration zone.In the half-pit rock mass,with the increase of alteration strength,the contents of other elements decrease except the U element content.Characteristics of rare Earth elements of Granites in the small fracture alteration Zone profile of Zudong and its surrounding Half-Pit and Fukeng rocks:The REE and HREE of the rock mass of Zudong are all increased with the reinforcement of the fracture alteration,and the rocks are HREE enrichment and the Eu negative anomaly,The L/H of Zudong,half pit and Fukeng rocks decreased with the increase of alteration strength;HREE enrichment of Fukeng rock mass,?REE was affected by alteration,and?REE increased with the enhancement of alteration.The?REE characteristic of the half-pit rock mass is opposite to that of Zudong.The stronger the alteration is,the smaller the?REE is.The ore-forming of body weight rare earth elements in Zudong rock is mainly affected by the following three stages:?1?The formation of Zudong rock mass during magmatic evolution and the formation of rare earth rich in the process of volcanic rock ejection at the same time;?2?Tectonic alteration evolution stage:Two NE trending faults and one EW trending deep fault formed structural clamping area,which was influenced by three faults and their secondary structures.Strong alteration developed on both sides of these fault zones,with the enhancement of hydrothermal alteration.REE+Y increased to a maximum of 6 times;The lowest value of L/H is0.20 with the increase of alteration strength;?3?The effect of different weathering intensity and weathering type on the ore-forming characteristics of rare earths is obvious:In the weathering crust,the HREE is mainly enriched in the completely weathered layer,and the sample L/H of the weathered crust profile decreases from top to bottom,indicating that HREE is relatively enriched in the lower part of the weathered crust profile;The content of Fe₂O₃ in granites of different weathering types is very important.Multiple evidence suggests:There is a positive correlation between Fe₂O₃ content and L/H value,and a positive correlation between Fe₂O₃ content and?REE value at the same sampling point in Zudong rock mass.The?REE value of granitic rocks with high Fe₂O₃ content is relatively high.