Occurrence Of Silicon In Magnetite From Yamansu Iron Deposit In Xinjiang Province

Magnetite occurs widely from hydrothermal to magmatic rocks,which has inverse spinel structure.Because of the frequent occurrence of isomorphism in magnetite lattice,the lattice can occur in a variety of impurity elements.Silicon and iron are quite different,either from the ionic radii or electronic obtain ability,however,both electron microprobe data and wet chemical methods analysis showed that: magnetite contains certain amount of silicon.Whether the Silicon is similar to Al,Mg and Ti,entering into the magnetite lattice,is not clear.Some studies have shown that: the silicon content in the magnetite may relate to diagenetic environment: in the hydrothermal environment,SiO2 content may up to 6.19 wt%,where as in the magmatic ones,it seems that silicon content mostly under detection limit of electron probe.This paper summarizes the research work on the isomorphism of the impurity elements(Co,Si,Ca,Cu,Ni,Mg,Ti,Mn)in magnetite.The samples from Yamansu magnetite were used electron microprobe,X-ray diffraction,transmission electron microscope,M?ssbauer spectroscopy and other technical methods for system analysis and testing,the aim of this study is to identify the status of silicon in magnetite.The results of the studies are listed as follows:(1)The results of electron probe show that magnetites contain a certain amount of silicon,and the content of Si and Fe3+ had obvious negative linear relationship,indicating that Si enters into the lattice of magnetite.It is worth noting that high-resolution electron microscopy and energy spectrum analysis showed that there were silicate inclusions in magnetite.(2)X-ray diffraction shows that the lattice parameters of the test samples are slightly smaller than the magnetite.Because of the difference of Si and Fe ions and the substitution content,the lattice parameters of the test samples are 8.392? and 8.374? respectively.The silicon entering into the lattice of the magnetite is the main reason for the decrease of the unit cell parameters.The isomorphism is the main form of silicon in magnetite;(3)The data of M?ssbauer spectroscopy show that Si substituted for the position of Fe3+ in the tetrahedron,with the isomorphous substitution more widely,the isomer shift and quadrupole splitting parameters on the A-site increased slightly,hyperfine magnetic field parameters on the A-site decreased slightly;isomer shift and the magnetic hyperfine field parameters on the B-site decreased slightly;the half-width on the A and B site were slightly reduced;A/B area ratio decreased.