摘要
Haitaite-(La),(La,Ce)(U^(4+),U6^(+),Fe^(2+))(Fe^(3+),Al)2(Ti,Fe^(2+),Fe^(3+))18O38,is a new member of the crichtonite group.It is named after the Haita Village in the Miyi County of Sichuan Province,China,where the mineral was discovered.The mineral occurs as black opaque centimeter-sized aggregates in the external contact zone between the Neoproterozoic(~800 Ma)alkali feldspar granite and the Mesoproterozoic(~1700 Ma)micaschist.In the studied sample,haitaite-(La)is associated with other minerals,including ilmenite,magnetite,rutile,zircon,brannerite and uraninite.The new mineral is a black,metallic phase and has a Mohs hardness of 6,with a density of 4.99 g/cm3(calculated)and 5.03 g/cm^(3)(measured).Haitaite-(La)is opaque in transmitted light and grayish-white under reflected light,with a reflectivity between 22.5%and 16.42%in the 400–700 nm band(SiC,in the air).The compositions of the mineral were measured by EPMA,the U4+/U6+ratio was determined by X-ray photoelectron spectroscopy and the Fe^(2+)/Fe^(3+)ratio was determined by Mössbauer spectroscopy.Haitaite-(La)is trigonal,belongs to R3¯and has unit-cell parameters a=10.3678(5)Å,c=20.8390(11)Å,V=1939.9(2)Å3,Z=3.The crystalline structure is composed of octahedra with 9 layers of close-packed octahedra(M1,M3,M4,M5),tetrahedra(M2)and contains large 12-coordinated M0 sites.
基金
supported by China Nuclear Geology(Grant No.202137-3)
the National Natural Science Foundation of China(Grant No.42002044)
the CNNC Science Fund for Talented Young Scholars(Grant No.QNYC2020-2).
