日本地球惑星科学連合2018年大会

講演情報

[EJ] Eveningポスター発表

セッション記号 S (固体地球科学) » S-RD 資源・鉱床・資源探査

[S-RD33] 資源地質学

2018年5月23日(水) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:大竹 翼(北海道大学大学院工学研究院 環境循環システム部門)、荒岡 大輔(産業技術総合研究所地圏資源環境研究部門)、高橋 亮平(秋田大学大学院国際資源学研究科、共同)、野崎 達生(海洋研究開発機構海底資源研究開発センター)

[SRD33-P01] 南薩型金鉱床における Au の挙動

*石田 美月1村上 俊平1安川 和孝1,2中村 謙太郎1藤永 公一郎2,3加藤 泰浩1,2,3,4 (1.東京大学大学院工学系研究科システム創成学専攻、2.千葉工業大学次世代海洋資源研究センター、3.東京大学大学院工学系研究科 エネルギー・資源フロンティアセンター、4.海洋研究開発機構 海底資源研究開発センター)

キーワード:南薩型金鉱床、全岩化学組成、高硫化型鉱床、黄鉄鉱、鉱物資源

Gold (Au) is one of the most important metals in our society, used not only in making jewelry and financial transactions but also in various electronic devices and aerospace technology. Au generally occurs as an ore-forming mineral of hydrothermal deposits [1]. The Nansatsu-type gold deposits in the southern area of Kagoshima, Kyusyu, on which this study focuses, are the representative hydrothermal gold deposits in Japan.

In order to explore undiscovered gold deposits, understanding of the formation mechanism of high-grade hydrothermal gold deposits is important. In this respect, elucidation of the behavior of Au during the formation of gold deposit constitutes a key constraint. However, the behavior of Au on the formation of hydrothermal deposits has not been fully understood. This is partly because the concentration of Au in the ore and ore-forming fluid is significantly lower compared to those of the major elements such as Fe and Cu.

In this study, therefore, we conducted multi-trace element analysis (including Au) of the ore samples collected from the Kasuga and Akeshi deposits by using ICP-MS. As a result, we found out that the sulfide (mostly pyrite) samples from the Akeshi and Kasuga deposits can clearly be divided into two groups by their composition: higher As group (> 200 ppm) and lower As group (< 100 ppm). The samples of the higher As group show strong positive correlations between Au and As (r=0.99) and between Au and Pb (r=0.87). In contrast, the samples of the lower As group show no clear correlation among Au, Pb and As contents. Instead, the Au content of these sulfide samples correlates well with Cu (r=0.67) and Co (r=0.75). These results imply that the elements associated with Au are different in the two groups. The contrasting geochemical features in the two groups of sulfide minerals might suggest that two hydrothermal fluids that had distinct chemical composition were involved in the Au-mineralization in the Nansatsu-type gold deposits.


[1] Mariko, T (2008) Geology of Ore Deposits. Kokin-Shoin, Tokyo, 580 p (in Japanese)