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Experimental Studies on Diagenesis under Hydrothermal Conditions

热液条件下成岩作用的实验研究

基本信息

批准号：
61470049
负责人：
MITSUSHIO Hiromi
金额：
$ 4.1万
依托单位：
Kochi University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1986
资助国家：
日本
起止时间：
1986 至 1988
项目状态：
已结题

项目摘要

The submarine topolography and subsurface sediments were studied off Aino-Shima island, north of Fukuoka day. Mechanical grain analysis was made, and the contents of calcareous sediments, mainly shell fragements, and magnetic mineral were measured. Medium sand is distributed at the southwestern part, and course one occupies the other area. Calcareous bioclastic sediment attains more than 60%, and magnetic content is 0.3 to 0.1%, and also 34 species of the molluscan shells are identified.Hydrothermal changes from amorphous silica gel into -cristobalite with additions of cobalt compounds, such as Co, CoO, Co(OH)_2, and CoCl_2・ 6H_2O, for 24-240 hours, were examined at the reaction temperatures of 350゜C, 300゜C, and 250゜C. Consequently, their crystallizing order is such as follows;Co(OH)_2 > CoO > Co > CoCl_2 ・ 6H_2OHydrothermal changes from amorphous silica gel are studied under the conditions at 250-350゜C for 96-384 hours with addition of CaCO_3. SiO_2 and CaCO_3 are effective mutually to dissolve, and they progress crystallization each other. Then this can well explain that limestone and chart in fields occur frequently with close relationship.Shell powder as starting material was treated for dolomite synthesis under hydrothermal conditions at 250-350゜C in mixed solutions of CaCl_2 and MgCl_2 with various Mg/Ca molar ratio. Dolomite phase was obtained at above 250゜C. The time, elaspsed until the first appearance of crystals of dolomite, was increased with temperature. Thus, the activation energy for dolomite formation was found to be 24 kcal/mol. Dolomite crystals were formed in mixed solutions with Mg/Ca molar ratio in the range of0.2 and 0.7. Above this range, only magnesite crystals were finally formed. It is very interesting for the consideration of diadenesis of dolomite formation that LMC and HMC were necessarily formed as intermediate phases.

本文对福冈以北的爱野志摩岛附近海域的海底地形和地下沉积物进行了研究。进行了机械粒度分析，并测定了钙质沉积物（主要是贝壳碎片）和磁性矿物的含量。中砂分布在西南部，一层占另一层。结果表明，在24-240小时的水热作用下，无定形硅胶在Co、CoO、Co（OH）_2、CoCl_2· 6H_2O等钴化合物的作用下，逐渐转变为α-方石英，而在24-240小时的水热作用下，无定形硅胶逐渐转变为α-方石英。在350 ℃、300 ℃和250 ℃的反应温度下进行了检测。研究了无定形硅胶在250-350 ℃、96-384小时、添加CaCO_3条件下的水热变化。SiO_2和CaCO_3相互有效溶解，并相互促进结晶。以贝壳粉为原料，在不同Mg/Ca摩尔比的CaCl_2和MgCl_2混合溶液中，于250-350 ℃水热条件下合成白云石。在250 ℃以上得到白云石相。白云石晶体首次出现的时间随温度的升高而延长。因此，白云石形成的活化能为24千卡/摩尔。白云石晶体在Mg/Ca摩尔比为0.2 ~ 0.7的混合溶液中形成。超过这个范围，最终只形成菱镁矿晶体。对于白云岩形成的二叠作用，LMC和HMC必然作为中间相形成，这是非常有趣的。