黑钨矿中微量元素的赋存状态葠带状构造

THE EXISTENCE STATE OF MINOR ELEMENTS IN WOLFRAMITE AND ITS ZONAL STRUCTURE

本文应用扫描电镜、X射线衍射(粉晶)分析、电子探针、化学分析、原子吸收光谱分析等手段研究了大吉山和瑶岗仙脉状钨矿床中黑钨矿微量元素的赋存状态、含量以及Nb、Ta在矿物中的“置换容量”等问题。大吉山6号脉及瑶岗仙501号脉黑钨矿单晶具有带状构造,结合各带的成分特点,讨论了具带状构造黑钨矿的形成条件及其成因意义。

The existence state of Fe, Mn and minor elements in the wolframite of Dajishan and Yaogangxian wolfram deposits is discussed. Some elements are homogeneously-distributed (Nb,Ta, Y,Sc, Mo,Co,Zn)as shown by the scanning electronic microscope,but a few elements(Ca, Al) are distributed heterogeneously. By means of x-ray powder diffractometry, the enclosures of plagioclase (Ca,Al)or scheelite (Ca) in wolframite have been found.Ca and Al are homogeneously-distributed in the area other than the enclosure.A lot of elements in wolframite(Nb,Ta, Mg, Y,Sc, Mo,Co,Zn) are parts of solid solution, for example, W is replaced by Nb,Ta and Mo.Fe and Mn are replaced by Mg,Y,Sc,Co and Zn.A few elements(Ca and Al)afe contained in enclosures or (and) the composition of wolframite (Fe and Mn are replaced by Ca and Al).The zonal structure in wolframites from vein No.6 of Dajishan was found in 1983 by the author.The crystal of wolframite has nine zones and its content of iron is: 100(l);21.28(l*);46.8l(2);8.5l(2*); 91.49(3); 6.38(3*); 66.38(4); 17.02(4*); 31.91(5), where 1-5 are positive peaks, whereas l*-4* are negative ones. Wolframite of Yaogangxian has zonal structure too, which was revealed by electron probe microanalysis.