| The chalcopyrite has been found in the Xingtai mining area,which is located in Litougou-Xingshutai and Mankaiyu,Neixiu Country.The tectonic position is in the south of Zanhuang uplift.The main metamorphic rocks are NW-SE extensional,NE-dip,and medium-dip angle.The Xingshutai mining area is a layer-controlled polymetallic deposit where sulfur,iron,copper and other minerals are present.The Rb-Sr dating of chalcopyrite represents that the Xingtai copper deposit was formed in the Proterozoic.Based on the theory of mineralogy,this paper studies the characteristics of chalcopyrite self-crystallized lattice parameters,morphological type,main trace rare earth elements and the dolomite-calcite coexisting with chalcopyrite,then gets the Crystal formation conditions.The chalcopyrite in the copper deposit is semi-self-shaped,and the dolomite-calcite coexist in the self-shape state.The crystal of chalcopyrite mainly appears as a p{112}crystal of tetragonal tetrahedron;{201} polycrystals;polyhedral crystal of tetragonal x{119},p{112} and square m{110};parallel double sided c{001} and tetragonal tetrahedron d{118}?-?{221} polycrystals;orthorhombic o{111} contact bicrystals.Chalcopyrite crystal surface color is copper yellow,and some oxidation surface was tarnish color,its hardness is3-4,the density between 4.103-4.179 with the metallic luster,the fracture was uneven,chalcopyrite from the crystal Physical properties and ordinary chalcopyrite has no significant difference.X-ray diffraction analysis showed that chalcopyrite crystal has two kinds of structure,mainly a tetragonal crystal system,a = b = 5.18,c = 10.53,space group I-42d;followed by equiaxed crystal with sphalerite structure,Significant triangular corrosion.This form of chalcopyrite high-temperature phase,the unit cell parameters a = b = 5.27,c = 5.194,the space group p-42 m.The contents of Cu,Fe and S in the chalcopyrite are between 99.243% and 99.738%,with a small amount of elements such as Ag,Mg and Se.The elements such as Pb,W,Zn and Ba are enriched in trace elements,Mo and Re are depleted and the ratio of Th / La is low.The ore-forming fluids are Cl-rich hydrothermal fluids.The rare earth elements are characterized by the relative enrichment of light rare earths,the ?LREE is 1.44×10-6 ~4.03×10-6,?HREE is 0.19×10-6~ 1.19×10-6,showing a strong negative Ce anomalies and weak negative Eu anomalies,combined with Y / Ho ratio is higher than 28,suggesting that the formation of chalcopyrite crystals related with much seawater Mixed.Based on the analysis of the above elements,it can be inferred that it is formed in the oxidizing environment.The composition of the hydrothermal fluids is mainly seawater heated at thelater stage of magmatic process,convective action and magmatic hydrothermal mixing occur to participate in mineralization.At this stage,chalcopyrite and dolomite-calcite crystals grow in close contact with each other and the temperature decreases slowly,which provides the premise for the formation of chalcopyrite.Based on the study of dolomite fluid inclusions,the fluid inclusions is in the deep environment with medium-high temperature and medium-high pressure.The ore-forming fluid is magmatic hydrothermal fluid mixed with large amount of seawater with medium-high salinity,medium-low density. |
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