著者

平野 伸夫 竹之下 愛 土屋 範芳

出版者

一般社団法人 日本鉱物科学会

雑誌

岩石鉱物科学 (ISSN:1345630X)

巻号頁・発行日

vol.38, no.5, pp.198-207, 2009 (Released:2009-11-26)

参考文献数

28

被引用文献数

2 2

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Carbonate hot spring is a natural chemical reaction field for understanding CO2 geological sequestration as a natural analogue. Natural analogue studies are particularly important to understand the kinetics of mineral precipitation which has potential difficulties in experimental investigations. Carbonate sinter is frequently formed in and around carbonate hot spring, which can be suitable to elucidate mechanisms of carbonate precipitation associated with flushing CO2.   Oku-Okuhachikuro hot spring, located in Kosaka town, Akita Prefecture, NE Japan, is an artificial hot spring after drilling of exploration for the Kuroko-deposits, and it is still active where carbonate sinter has still been forming continuously for more than thirty years after drilling. The temperature of spring water is 44 °C and water pH is 6.2, with discharge rate of 0.08 m3/min. The average chemical compositions of sinter correspond about 80 wt% CaCO3, and 4 wt% Fe2O3, associated with minor (<1 wt% each) SiO2, MnO, MgO, Na2O and K2O. Carbonate sinter is mainly composed of aragonite with a small amount of calcite; an intimate occurrence of these two forms of CaCO3 is the most characteristic feature of this locality. However, mineral assemblage, texture and structure of carbonate sinter are different in relation to the distance from the blowout point. Near the blowout point, the sinter is well solidified and shows laminar structure having both of calcite and aragonite. Thickness of Ca-rich laminar ranges from 20 to 150 μm and Fe-rich one is from 10 to 80 μm. Calcite and aragonite assemblage is mainly observed in Ca-rich layer. The Fe-rich layer, however, is composed only of aragonite. The sinter along downstream becomes porous and is monomineralic having aragonite as CaCO3. The observed relations on the special distribution of aragonite/calcite and the possible stability relations of these phases through EPMA and TG-DTA analyses suggest an importance of minor elements (Fe, etc.) in the precipitation of metastable carbonates: this possible effect of the precipitation of metastable phases should be taken into account in the consideration of geochemical processes of CO2 mineral trapping.

著者

岡本 敦 平野 伸夫 土屋 範芳

出版者

一般社団法人日本鉱物科学会

雑誌

日本鉱物科学会年会講演要旨集

巻号頁・発行日

vol.2008, pp.13, 2008

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石英脈の組織発達の支配要因を明らかにするために、流通式水熱反応実験を行った。シリカの析出条件は温度が400-430度、圧力が31MPaである。Siに過飽和な溶液は350-370度で石英、アモルファスシリカ、または花崗岩を溶解させて作成し、その溶液を花崗岩を敷き詰めた反応管に流して析出様式を観察した。析出物の種類(石英、クリストバライト、アモルファスシリカ)、またその析出の仕方は溶液の濃度と反応場所(石英表面、長石表面、流体中)によって異なることが明らかとなった。特に、低濃度(C/Ceq < 1.5)では花崗岩上の石英表面にのみ石英は析出し、ほかの表面では析出は起こらない。このことは、石英脈の組織は脈形成時の溶液濃度(Si)に対して制約を与えることを示唆している。

著者

平野 伸夫 竹之下 愛 土屋 範芳

出版者

一般社団法人 日本鉱物科学会

雑誌

岩石鉱物科学 (ISSN:1345630X)

巻号頁・発行日

vol.38, no.5, pp.198-207, 2009-09-30

参考文献数

28

被引用文献数

1 2

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&nbsp;&nbsp;Carbonate hot spring is a natural chemical reaction field for understanding CO₂ geological sequestration as a natural analogue. Natural analogue studies are particularly important to understand the kinetics of mineral precipitation which has potential difficulties in experimental investigations. Carbonate sinter is frequently formed in and around carbonate hot spring, which can be suitable to elucidate mechanisms of carbonate precipitation associated with flushing CO₂.<br> &nbsp;&nbsp;Oku-Okuhachikuro hot spring, located in Kosaka town, Akita Prefecture, NE Japan, is an artificial hot spring after drilling of exploration for the Kuroko-deposits, and it is still active where carbonate sinter has still been forming continuously for more than thirty years after drilling. The temperature of spring water is 44 &deg;C and water pH is 6.2, with discharge rate of 0.08 m³/min. The average chemical compositions of sinter correspond about 80 wt% CaCO₃, and 4 wt% Fe₂O₃, associated with minor (<1 wt% each) SiO₂, MnO, MgO, Na₂O and K₂O. Carbonate sinter is mainly composed of aragonite with a small amount of calcite; an intimate occurrence of these two forms of CaCO₃ is the most characteristic feature of this locality. However, mineral assemblage, texture and structure of carbonate sinter are different in relation to the distance from the blowout point. Near the blowout point, the sinter is well solidified and shows laminar structure having both of calcite and aragonite. Thickness of Ca-rich laminar ranges from 20 to 150 &mu;m and Fe-rich one is from 10 to 80 &mu;m. Calcite and aragonite assemblage is mainly observed in Ca-rich layer. The Fe-rich layer, however, is composed only of aragonite. The sinter along downstream becomes porous and is monomineralic having aragonite as CaCO₃. The observed relations on the special distribution of aragonite/calcite and the possible stability relations of these phases through EPMA and TG-DTA analyses suggest an importance of minor elements (Fe, <i>etc.</i>) in the precipitation of metastable carbonates: this possible effect of the precipitation of metastable phases should be taken into account in the consideration of geochemical processes of CO₂ mineral trapping.<br>

著者

平野 伸夫

出版者

東北大学

雑誌

若手研究(B)

巻号頁・発行日

2007

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温暖化対策の一つとして考えられているCO_2の地中貯留に関連して,秋田県奥奥八九郎温泉を対象に,現在でも活発に生じている炭酸カルシウム堆積物の 1)微生物代謝による生成2)溶液化学反応による生成 について検討した.その結果,1)に関しては微生物の存在は認められたものの,それが炭酸カルシウムの生成に結びついている確証は得られなかったが,2)に関しては温泉水中のFeイオンが炭酸カルシウムの生成に影響をおよぼしている可能性を見いだした.このFeおよび炭酸カルシウムに必要なCaはと地下の安山岩-玄武岩から供給されていると考えられ,このような岩質の場にCO_2貯留をおこなえば岩石化が促進される可能性がある.