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An Experimental Study on the Origin and Dynamics of the Earth's Lower Mantle

地球下地幔起源和动力学的实验研究

基本信息

批准号：
13852005
负责人：
ITO Eiji
金额：
$ 64.06万
依托单位：
Okayama University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (S)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2004
项目状态：
已结题

项目摘要

We have established a technique to generate pressure up to 60 GPa over a specimen volume 2 mm^3 within a repeatable accuracy of 2% using the Kawai-type multi anvil apparatus equipped with sintered diamond cubic anvils with edge length of 14 mm and a truncated corner of 1.5 mm. The maximum pressure reaches higher than 63 GPa. We carried out determination of phase equilibria of several materials under high-pressure and high-temperature by means of in situ X-ray observation using synchrotron radiation at Spring-8. First we examined iron up to 44 GPa and 2100 K. The stability of β-Fe was excluded, and the phase boundary for the ε【tautomer】γ transition was established. We further studied the phase equilbria of GaN and Fe_2O_3 up to 62GPa/900K and 58GPa/1400K, respectively, together with measurement of electrical resistance at 300 K. In GaN, the wurtzire-rocksalt transition was observed at 54GPa/300K and 51.5GPa/750K, suggesting the phase boundary with a negative slope. It was confirmed that … More Fe_2O_3 hematite (phase I) transforms successively into Rh_2O_3II type (II) and an orthorhombic phase (III) with increasing pressure. Both the phase boundaries for the I【tautomer】II, II【tautomer】III have negative slopes. The electrical resistance of GaN was in several tens of mega ohms up to 62 GPa and did not show any remarkable change on the wurtzite-rocksalt transition. The electrical resistance of Fe_2O_3, on the other hand, decreased monotonically from several hundreds mega ohms at 0 GPa to a few ohms at 58 GPa. However, the decrease over a pressure range 54±1 GPa was characteristically abrupt, ca. four orders of magnitude, which can serve as a new pressure fixed point.In order to simulate material fractionation in a magma ocean formed in the early stage of the Earth, we performed melting experiments on peridotite and CI mantle material up to 35 GPa. In peridotite the first liquidus phase changes from feropericlase (Fp) to Mg-perovskite (Mg-Pv) and at 33 GPa liquidus Mg-Pv is successively followed down temperature by Fp and Ca-perovskite (Ca-Pv) within a small temperature interval. In CI mantle material, Mg-Pv is also the liquidus phase followed down temperature by Ca-Pv. These results suggest fractionation of both Mg-Pv and Ca-Pv in a deep magma ocean resulting in formation of a perovskite layer in bottom of the mantle. The layer may be a geochemical reservoir due to the high capability of Ca-Pv to accommodate large cations such as alkaline and rare earth elements.We have successively synthesized single crystals with mm size of deep mantle materials such as Mg-Pv. These crystals are to be used for measurements of elasticity and various transport phenomena such as element and thermal diffusivilitisand electrical conductivity. Less

我们已经建立了一种技术，使用配备边长为14 mm、截角为1.5 mm的烧结金刚石立方体砧的河合型多砧装置，在2 mm^3的样品体积内产生高达60 GPa的压力，重复精度为2%，最大压力达到63 GPa以上。我们在Spring-8上用同步辐射X射线原位观测的方法测定了几种材料在高温高压下的相平衡。首先，我们研究了高达44 GPa和2100 K的铁。排除了β-Fe的稳定性，建立了ε[互变异构体]γ相变的相边界。进一步研究了GaN和Fe_2O_3在62 GPa/900 K和58 GPa/1400 K下的相平衡，并测量了300 K下的电阻。在54 GPa/300 K和51.5GPa/750 K下观察到GaN的wurtzire-rocksalt转变，表明相界具有负斜率。证实了 ...更多信息 Fe_2O_3赤铁矿（Ⅰ相）随压力的增加依次转变为Rh_2O_3 Ⅱ型（Ⅱ相）和斜方晶相（Ⅲ相）。I[互变异构体]II、II[互变异构体]III的相边界都具有负斜率。GaN的电阻在高达62 GPa的几十兆欧姆，并且在纤锌矿-岩盐转变上没有显示出任何显著的变化。而Fe_2O_3的电阻则从0 GPa时的几百兆欧姆单调下降到58 GPa时的几欧姆。然而，在54±1 GPa的压力范围内的下降是典型的突然，约。为了模拟地球早期形成的岩浆海洋中物质的分馏过程，我们对橄榄岩和CI地幔物质进行了高达35 GPa的熔融实验。在橄榄岩中，第一液相线相从铁钙钛矿（Fp）转变为镁钙钛矿（Mg-Pv），并且在33 GPa液相线Mg-Pv之后，在小的温度间隔内依次由Fp和钙钛矿（Ca-Pv）降温。在Cl地幔材料中，Mg-Pv也是液相，随后是Ca-Pv。这些结果表明，Mg-Pv和Ca-Pv在深部岩浆海洋中的分馏导致在地幔底部形成钙钛矿层。由于Ca-Pv对碱金属和稀土元素等大阳离子具有很强的容纳能力，该层可能是一个地球化学储集层。这些晶体用于测量弹性和各种传输现象，如元素和热扩散率和电导率。少