西藏墨竹工卡地区甲玛矽卡岩型铜多金属矿体的变化性

Variation of Jiama skarn copper-polymetallic body in Mozhugongka area, Tibet, China

以甲玛矽卡岩型矿体为研究对象,通过对矿体主要区域化变量矿石品位半变异函数的分析,建立了相应的半变异函数的球状模型,从而求得矿体主要变化方向上的滞后距、块金值、变程等参数。根据这些参数,求得矽卡岩型矿体的铜钼矿体主元素Cu、Mo品位在各方向上的变化性质系数为0.45,表明铜钼矿体中主元素品位在走向、倾向和垂向上都具有明显的坐标性变化;而铅锌矿体中Pb在各方向上的变化性质系数为0.58,Zn变化性质系数为0.5,显示铅锌矿体中主元素品位在走向、倾向和垂向上均具有一定的随机性变化。Cu、Mo、Pb、Zn品位变化程度系数在走向、倾向方向均大于0.9,表明矿体内的矿石品位变化程度是极复杂的。Cu、Mo在垂向上的变化程度系数值均在0.6~0.8之间,变化程度中等;Pb、Zn垂向上的变化程度系数值介于0.3~0.6之间,变化程度较简单。据此认为,控制矿体变化的因素主要是由斑岩-矽卡岩型矿床的成因所决定的,矿体形成时存在多阶段的矿化叠加,使有用矿物、成矿元素具有明显的分带性。

In this paper, putting the skarn-type ore body as the research object, according to the semi-variogram analysis of main internal symbol ore-grade in ore-body and establishing a corresponding spherical model, we get many parameters, as lag distance, nugget, variable-range, for the mainly variable directions of ore body. According to these parameters, the variation coefficients at every aspect of main elements, such as copper and molybdenum, in its copper-molybdenum ore body, are both 0.45. It indicates that both the main elements and the symbiotic elements in copper-molybdenum ore body have obvious coordinate changes in the direction of strike, tendency and vertical. While in the lead-zinc ore body, lead＇s variation coeffient is 0.58, and zinc＇s variation coeffient is 0.5, which indicates that they already have a certain randomness change in the direction of strike, tendency and vertical. Copper, molybde-num, lead and zinc, whose coefficients of grade change degree are all more than 0.9 in the direction of strike and tendency. It indicates that the ore＇s grade change degree is extremely complex in the ore body. The variation coeffient values of copper and molybdenum are both between 0.6 and 0.8 in the direction of vertical, showing their extent of changes are medium. And the lead and zinc＇s are between 0.3 and 0.6, showing that their degree of changes are relatively simple. Accordingly, we sum up the factors which control the ore body＇s change are mainly the cause of porphyry-skarn-type deposit, and there is a multi-stage mineralization during ore formation, to make useful minerals, ore-forming elements have a clear zoning.