@article{oai:niigata-u.repo.nii.ac.jp:00006824, author = {Yamazaki, Shusaku}, journal = {Science reports of Niigata University. (Geology), Science reports of Niigata University. (Geology)}, month = {Mar}, note = {The grinding of rock sample by tungsten carbide (WC) mill provides higher efficiency and performance than other mill materials such as agate. However, it has disadvantage of contamination of the sample with the grinding unit material. In order to evaluate the contamination effect from WC mill, we analyzed 31 trace elements of the quartz sand that was ground by WC rod mill and agate ball mill. The results of the quartz sand analysis demonstrate that the grinding by WC rod mill leads to the significant high contamination of W (1963 ppm) and Co (482 ppm). Their abundances were more than 1000 times higher than those by agate ball mill. The contaminations of Ta (0.6 ppm) and Nb (0.15 ppm) were also detected in the quartz sand ground by WC rod mill. The contaminations of Fe and Ti were also estimated to be in sub-ppm levels as well as the Ta contamination. The contamination of Fe and Ti can be considered as negligible for typical igneous rock samples containing over hundreds of ppm in these elements. In order to investigate the effect of the contamination for natural igneous rock, the plagiogranites from the Oman ophiolite were ground by the WC and agate mills and were measured for their trace element compositions. The WC ground plagiogranites demonstrate the compositional correlations of SiO2 with Co and Ta concentrations. These correlations indicate that the contamination is controlled by the amount of quartz in the sample. The regression analyses of these correlations indicate that the contamination in the quartz-free rock, such as basalt and gabbro, is equivalent to 30% of the effect by the quartz sand. Collectively, these trace element analyses suggest that the grinding by the WC rod mill leads to the contaminations of W, Co, Ta and Nb in the sample. The contaminations of W and Co seriously affect on discussion of their geochemical characteristics. The contamination of Ta also affects on the plot on some discrimination diagrams. The contamination of Nb does not seem to affect so much if the original Nb concentration is sufficiently high (more than a few ppm) or analytical detection and error are significantly larger than the extent of contamination. These indicate that if the analyses of W and Co are not needed, the grinding by the WC mill is applicable for the rock sample with more than a few ppm in Nb and tens of ppm in Ta.}, pages = {91--99}, title = {Trace element contamination from tungsten carbide rod mill}, volume = {26}, year = {2011} }