黑钨矿中铌钽含量变化的研究及意义

黑钨矿中铌、钽含量的变化和锰、铁含量的的变化一样,是黑钨矿具有成因意义和找矿意义的重要标型特征之一,且前者在时间、空间上的变化规律较后者更明显。本文在作者近几年研究黑钨矿成分、时空变化规律的基础上,进一步讨论与黑钨矿中铌、钽含量变化有关的问题及其找矿意义。

Variation in Nb-Ta Contents Of Wolframite And Its Significance As An Indicator

The Nb-Ta contents of wolframite seem to be one of the major indicators in genesis study and mineral exploration of tungsten deposits. Tungsten deposits related genetically to continental volcanism-subvolcanism, marine volcanic exhalation-hot spring precipitation, hydrothermal infiltration-metasomatism or sedimentation-transformation obviously contain much less Nb and Ta than various ore deposits pertaining to metallogenic series of granites. The variation in Nb-Ta contents of wolframite shows a decreasing tendency from early to late stage and from parent rock to country rock. The investigation of six typical deposits and the correlation analysis and R-factor analysis of data acquired from 30 deposits suggest the presence of positive correlation between Nb and Ta in wolframite with different deposits exhibiting diverse degree of such correlation, and the nonexistence of correlation between Nb, Ta and Mn, Fe. The mineral facies analysis, electronic microprobe scanning and the determination of residue reveal that Nb and Ta are predominantly evenly distributed in wolframite in the form of isomorphism with a probable minor amount present in Columbite-tantalite and microlite as micro-inclusions. The variation in Nb-Ta content of wolframite depends principally on the concentration of Nb⁵⁺ and Ta⁵⁺ during the crystallization of wolframite. The characteristics of Nb-Ta contents of wolframite and the regularity of their variation might find applications in two aspects: to determine the genetic relations between ore veins in granites and their country rocks and to predict the extension of ore veins.