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

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, molybdenum, 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.