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，使用配备边缘长度为 14 mm 的烧结金刚石立方砧和截头的 Kawai 型多砧装置，在 2 mm^3 的样本体积上产生高达 60 GPa 的压力，重复精度为 2%。 1.5毫米的最大压力达到63 GPa以上我们通过原位方法测定了几种材料的相平衡。首先，我们在 Spring-8 上使用同步加速器辐射进行 X 射线观察，在 44 GPa 和 2100 K 下检查了铁。排除了 β-Fe 的稳定性，并进一步建立了 ε【互变异构体】γ 转变的相界。研究了 GaN 和 Fe_2O_3 分别高达 62GPa/900K 和 58GPa/1400K 的相平衡，以及 300 ℃下的电阻测量K. 在 GaN 中，在 54GPa/300K 和 51.5GPa/750K 处观察到纤锌矿-岩盐转变，表明相界具有负斜率，证实 Fe_2O_3 赤铁矿（I 相）依次转变为 Rh_2O_3II 型（II 相）。 ) 和随着压力增加的斜方相 (III) 两者的相界。 I【互变异构体】II、II【互变异构体】III具有负斜率，GaN的电阻高达62GPa，在纤锌矿-岩盐转变过程中没有表现出任何显着的变化。另一方面，从 0 GPa 时的数百兆欧姆单调下降到 58 GPa 时的几欧姆。但是，在压力范围内下降。 54±1 GPa具有突变性，大约四个数量级，可以作为新的压力固定点。为了模拟地球早期形成的岩浆海洋中的物质分馏，我们对橄榄岩进行了熔融实验。 CI 地幔材料在高达 35 GPa 的压力下，第一液相从铁橄榄石 (Fp) 转变为镁钙钛矿 (Mg-Pv)。在 CI 地幔材料中，Mg-Pv 的液相线随着 Fp 和 Ca-Pv 的温度依次降低。这些结果表明，在 CI 地幔材料中，Mg-Pv 也是随着 Ca-Pv 的温度降低的液相线。深部岩浆海中 Mg-Pv 和 Ca-Pv 的分馏导致地幔底部形成钙钛矿层，由于钙钛矿层的高容量，该层可能是一个地球化学储层。 Ca-Pv可容纳碱性和稀土元素等大阳离子。我们已相继合成了毫米级的深层地幔材料（例如Mg-Pv）单晶，这些晶体将用于弹性和各种输运现象（例如）的测量。元素和热扩散性和电导率。少