Alteration and weartering processes in the early terrestrial crust

早期地壳的蚀变和磨损过程

• 批准号: 08454152
• 负责人: TAGAI Tokuhei
• 金额: $ 0.51万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1997
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08454152/
• 关键词: Plagioclase; Archean; Alteration; Weathering; Microtexture; Pyroxene; Olivine

The materials of the terrestrial crust have contineously been weathered and altered by water since its formation. These phenomena are the most characteristic features of material evolution on the earth in the present solar system. However, the process of the weathering/alteration can not easily be traced because of the following volcanic, tectonic activities on the earth. We can see some products of the proteozoic alteration/weathering activities in the archean anorthosite complex in Superior Province, Canada. In order to simulate the proteozoic environment, we carried out the dissolution experiments on the single crystals of olivine, pyroxene and plagioclase, where the oriented thin specimens were used. Changing the experimental conditions (temperature, ph, time and orientation), the dissolution rate was measured and the surface of the reacted crystal was precisely observed. It can be concluded that the microtextures such as twinning or cleavage contribute very much on the dissolution rate and that the anisotropy of the crystal structure plays essential roll on the dissolution process.

地壳物质自形成以来，不断受到水的风化和蚀变作用。这些现象是目前太阳系中地球上物质演化的最典型特征。然而，风化/蚀变的过程不能很容易地被跟踪，因为在地球上的火山，构造活动。在加拿大苏必利尔上级省太古代斜长岩杂岩中，可以看到一些元古宙蚀变/风化作用的产物。为了模拟元古界环境，我们对橄榄石、辉石和斜长石单晶进行了定向薄片溶解实验。改变实验条件（温度、ph值、时间和取向），测量溶解速率并精确观察反应晶体的表面。结果表明，孪晶、解理等微织构对溶解速率的影响很大，晶体结构的各向异性对溶解过程起着重要作用。

项目成果

Murakami, T., Isobe, H., Sato, T., Ohnuki, T.: "Weathering of chlorite in a quartz-chlorite schist : I.Mineralogical and chemical changes." Clays and Clay Minerals. 44. 244-256 (1996)

Murakami, T.、Isobe, H.、Sato, T.、Ohnuki, T.：“石英-绿泥石片岩中绿泥石的风化：I.矿物学和化学变化。”

T.Tagai: "Preparation of porous apatite ceramics with straight through-channels." J.Mater.Sci.(in press). (1998)

T.Tagai：“具有直通通道的多孔磷灰石陶瓷的制备。”

T.Tagai, T.Hoshi and M.Suzuki: "Diffraction characteristics of calcic plagioclases from eucrites, lunar highland and archean anorthosites." Europ.Jour.Min.10. 125-132 (1998)

T.Tagai、T.Hoshi 和 M.Suzuki：“来自锂辉石、月球高地和太古代斜长岩的钙质斜长石的衍射特征。”

M.Suzuki: "Dissolution process and rate in feldspar:Effects of crystallographic orientation." Min.J.18-2. 43-53 (1996)

M.Suzuki：“长石中的溶解过程和速率：晶体取向的影响。”

Murakami, T., Ohnuki, T., Isobe, H., Sato, T.: "Mobility of uranium during weathering." American Mineralogist. 82. 888-899 (1997)

Murakami, T.、Ohnuki, T.、Isobe, H.、Sato, T.：“风化过程中铀的流动性。”