VIEIRA, A. G. F.; VIEIRA, Alexandre da Gama Fernandes.
Résumé:
The occurrence of gold in Cachoeiras de Minas located at the extreme
southwest of Paraiba was discovered in 1864 followed by exploration
in the auriferous regions of Pernambuco and Paraíba. Gold is concentrated
mainly in quartz veins in agreement with the general foliation
of the enclosing rocks. The veins are made of white quartz,
often fractured and impregnated with iron oxide. THE
systematic sampling performed in channel and chip form
sample "covered all came from Farias and Covico, main shafts
Metal bearers. In order to analyze continuity in mineralization and
homogenize the sample data for the estimates, we used
geostatistical techniques with their tools. The modeling
of variograms were made considering the effects of levels
extremes in the samples analyzed in this study. The elimination of
some high grade samples resulted in more
appropriate. Variographic studies revealed the presence of structures
mineralization in quartz veins, with the nugget effect varying from
1.3 to 1.7, dispersion variance from 1.5 to 2.4 and the range between
11 0 and 1 85 m. In the cross-validation of data it was observed that the average
estimated was close to the sample mean, however the difference between
the observed and estimated variances reached a significant value. The elaborated variogram models show the influence of structures
of shaping and shaping of shafts in metal distribution.
Soil gold variogram modeling associated with
veins showed the presence of structures with a nugget effect of 3.2
ppb, variance of 2,5 and 1,500 m range. The distribution of metal in
soil and directly related to quartz veins. The contents
estimated gold in the soil correspond to the sample levels but ha
significant difference between estimated and observed variance.
The high values of estimated variance are caused by the
extreme variations in sample contents. The kriging of the points and
influenced by the high levels resulting in the excessive estimation of
variance and estimated content. Co-kriging may decrease
the influence of high contents and reduce the estimated ore variance.
