[H-RE13] 資源地球科学

[HRE13-P13] Geochemistry of antimony and tungsten mineralization of the Doi Ngom deposit, northern Thailand

*Karn Phountong¹、Ryohei Takahashi¹、Punya Charusiri²、Andrea Agangi¹、Pearlyn Manalo¹、Ladda Tangwattananukul³、Hinako Sato¹ (1.Akita Univ.、2.Department of Mineral Resources、3.Kasetsart Univ.)

キーワード：antimony, tungsten, Doi Ngom, Sukhothai Fold Belt, Thailand

The Doi Ngom W-Sb deposit is one of several W-Sb occurrences located in the Sukhothai Fold Belt that forms a part of the South-East Asian metallogenic belt. The Sukhothai Fold Belt is a N-S trending volcanic arc extending from Yunnan, southern China to Thailand, small parts of Myanmar and Laos, and peninsular Malaysia. This research aims to elucidate geochemical characteristics of the Doi Ngom deposit based on the mode of occurrence of ores and host rocks. On the basis of the field observations, two types of mineralization were identified: (1) wolframite filling the open-space of brecciated rocks, and (2) stibnite disseminated in mudstone. We employed petrography and whole-rock geochemical analysis. The brecciated rocks consist of very angular to moderately rounded pebble-sized clasts and matrix of wolframite and fine-grained quartz with 0.01-0.02 mm grain size. The dissemination of mudstone includes subhedral to euhedral stibnite grains with 1-5 mm in size as well as subhedral to euhedral fluorite grains with 0.01-0.05 mm in size. Bulk chemical compositions of the Wolframite-bearing breccia show 0.01 - > 10 wt% W, up to 0.69 wt% Sb, 0.06-0.13 ppm Au, 0.17-0.93 ppm Ag, 54.4-145 ppm Cu, 7.87-564 ppm Pb, and 15.2-858 ppm Zn, while those of the stibnite disseminated mudstone show 0.07-1.42 wt% Sb, 0.07-0.54 ppm Au, 0.15-0.23 ppm Ag, 12.7-53.7 ppm Cu, 0.18-23.9 ppm Pb, and 0.20-80.6 ppm Zn. There are positive correlations (r > 0.8) of Au against Cr; Ag against Bi, V, Zn, Ge, In, and Pb; W against Ti, Cu, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu. In addition, there are slightly positive correlations of Sb against Au (r = 0.48); and Tl against Sb (r = 0.62). In contrast, there is a negative correlation (r = -0.85) of Ta against Ag. These correlations suggest a possible associations of Ag, Ti, Cu, Nd, and REEs with wolframite, and Au and Tl with stibnite.