Creep And Viscosity Of Mantle Rocks At High Pressure And Temperature

高压高温下地幔岩石的蠕变和粘度

• 批准号: 03640676
• 负责人: SATO Hiroki
• 金额: $ 1.28万
• 依托单位: Okayama University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1991
• 资助国家: 日本
• 起止时间: 1991 至 1992
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-03640676/
• 关键词: Superplasticity; Mantle viscosity; Grain growth; Postspinel transformation; Dissociation of manganese titanium oxide; Aseismicity; High pressure and temperature; Descending slab; B-MnzTiO_4の分解生成物; 粘性率; マントル; 変形実験; βーMn_2TiO_4の分解生成物; 転位密度

At the 670-km discontinuity, spinel dissociates to a fine-grained mixture of perovskite plus magnesiowustite. The fine-grained dissociation product may exhibit superplastic behavior ; we have thus accounted for the observed absence of seismicity below -700 km depth. In order to investigate the rheological properties of the dissociation product, grain growth of MnO + MnTiO_3 (an analogue of Pv + Mw) was studied at 0.9-1.6GPa and 1000-1320ﾟC. Even after annealing for 256 hours, grain size was less than 10 mum. Such a slow growth rate causes at least several tens of kilometers superplastic zone in the lower mantle slab. Further the dissociation product of Mn_2TiO_4 was deformed in a piston-cylinder high-pressure apparatus. Long and narrow grains of MnO and MnTiO_3, which are typical in superplastic texture, were observed in the deformed sample.Based on the creep and anelasticity data of mantle rocks at high pressure and temperature, we have derived a relationship between viscosity and seismic Q. This relation was used to estimate mantle viscosity from seismic Q structure. For the upper mantle beneath northeastern Japan, viscosity is low (-10^<20>Pa・s) in the back-arc side of volcanoes, and increases to -10^<23>Pa・s toward the tip of the mantle wedge. Viscosity of the descending slab is greater than 10^<23>Pa・s. Beneath the Pacific Ocean, upper mantle viscosity from the bottom of the lithosphere to 300 km depth is in the range of 3x10^<18>-3x10^<22>Pa・s. Viscosity at the lithosphere-asthenosphere boundary is in the range of 10^<20>-10^<21>Pa・s, and lithospheric viscosity is found to be larger than 10^<21>Pa・s. For the asthenosphere beneath the Iceland Plateau, Qs=7 (0-5 Ma) and 50 (5-10 Ma) yield 10^<16> and 10^<18>Pa・s, respectively. These viscosity values are consistent with the thermal states of the two regions, where one may expect 3-7 vol.% partial melt in 0-5 Ma and about 90 % of the solidus temperature in 5-10 Ma.

在670公里的不连续性下，尖晶石分离为钙钛矿加镁层岩的细粒混合物。细粒分解产物可能存在极具增塑性行为。因此，我们已经考虑到低于-700 km深度的地震性没有观察到。为了研究解离产物的流变特性，MNO + MNTIO_3的晶粒生长（PV + MW的类似物）在0.9-1.6GPA和100​​0-1320 ﾟC. C.即使退火256小时，晶粒尺寸也小于10妈妈。如此缓慢的生长速率在下地幔平板中至少导致了至少数十公里的巨型区域。此外，将MN_2TIO_4的解离产物在活塞缸高压设备中变形。在变形样品中观察到了MNO和MNTIO_3的长和狭窄晶粒，它们是典型的。在高压和温度下的蠕变和地幔岩石的厌氧性数据中，我们得出了粘度和地震Q之间的关系。这种关系用于估计从地震Q结构估算地震粘度。对于日本东北部以下的上地幔，粘度在火山的后弧侧较低（-10^<20> pa s），并增加到-10^<23> pa s朝向地幔楔的尖端。降板的粘度大于10^<23> pa。在太平洋的下方，从岩石圈底部到300 km深度的上地幔粘度在3x10^<18> -3x10^<22> pa ・S的范围内。岩石圈 - 心圈边界的粘度在10^<20> -10^<21> pa s的范围内，发现岩石圈粘度大于10^<21> pa・s。对于冰岛高原下方的动态圈，QS = 7（0-5 mA）和50（5-10 mA）的产量分别为10^<16>和10^<18> Pa・s。这些粘度值与这两个区域的热状态一致，在该区域的热状态下，在0-5 mA中，局部熔体可能为3-7％，在5-10 mA中约为固相温度的90％。

项目成果

Eiji Ito and Hiroki Sato: "Aseismicity in the lower wantle by superplasticity of the descending slab" Nature. 351. 140-141 (1991)

伊藤英二 (Eiji Ito) 和佐藤博树 (Hiroki Sato)：“下降板的超塑性导致下层的抗震性”《自然》。

Eiji ITO and Hiroki SATO: "Aseismicity in the lower mantle by superplasticity of the descending slab" Nature. 351. 140-141 (1991)

Eiji ITO 和 Hiroki SATO：“下降板块超塑性导致下地幔抗震”《自然》。

Hiroki Sato: "Rheological structure of a subduction zone : application of high P-T viscons and anelastic properties of mantle rocks" High-Pressure Research : Application to Earth and Planetary Sciences, Syono and Manghnani, eds, Terra Sci.Pub.Co.263-268 (

Hiroki Sato：“俯冲带的流变结构：高 P-T 粘度和地幔岩石滞弹性的应用”高压研究：在地球和行星科学中的应用，Syono 和 Manghnani，编辑，Terra Sci.Pub.Co.263-

Hiroki Sato: "Magma generation in island arc - a new constraint from seismic Q structure -" Chikyu Extra, S.Uyeda Volume. 3. 101-105 (1991)

Hiroki Sato：“岛弧中的岩浆生成 - 来自地震 Q 结构的新约束 -” Chikyu Extra，S.Uyeda Volume。

Hiroki Sato: "HighーPressure Research:Application to Earth and Planetary Scinces(Rheological structure of a subduction 2Dne:application of high PーTviscous and anelastic properties of mantle rocks)" Terra Scientific Publishing Company, (1992)

Hiroki Sato：“高压研究：在地球和行星科学中的应用（俯冲 2Dne 的流变结构：地幔岩石的高 P-T 粘性和滞弹性特性的应用）” Terra Scientific Publishing Company，（1992）