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橄榄石是上地幔的主要矿物之一,它的相变对于认识地幔不连续面的成因,整个地幔的物质组成和演化、地幔对流、俯冲板片深源地震等地球深部动力学问题具有重要意义.本研究使用中国地质大学地球深部研究实验室多面砧压机进行了2种成分的橄榄石(Fo100和Fo90)在压力为14.1～20GPa,温度为1400℃的相变实验研究.压力为14.8～15.6GPa时,Fo90和Fo100均转变为瓦兹利石(α);而在14.1GPa实验中,Fo90完全转变为瓦兹利石,Fo100则仍为橄榄石(α).瓦兹利石具有2种产状:破碎的粒状结构(粒度大于100μm)和微晶集合体(微晶粒度小于10μm).瓦兹利石拉曼谱图中显示722～723和917～919cm-1特征峰.随着压力升高,实验产物中出现更多的呈微晶集合体结构产出的瓦兹利石,表明实验压力离橄榄石相变边界越远,瓦兹利石成核密度越大,导致体系Gibbs自由能下降,高压相矿物颗粒生长受到抑制.但由于瓦兹利石成核活化能很小,因此实验产物中均有大量呈微晶集合体产出的瓦兹利石.实验产物的显微结构特征对解释陨石中出现瓦兹利石的产状提供高温高压实验启示.压力为19.5和20GPa时实验产物为林伍德石(γ),其中压力为19.5GPa的实验中Fo100中瓦兹利石和林伍德石共存.实验产物林伍德石为自形粒状(颗粒度为10～20μm),三联点结构发育.798和840cmμ1为林伍德石的拉曼特征峰.综合本次研究以及前人地震探测结果表明,中国东部上地幔复杂结构无法用单一的橄榄石体系相变来解释,其他矿物(如辉石-石榴石)的相变及其与橄榄石体系相变的相互影响可能导致了该地区上地幔具有复杂的结构.因此进一步开展复杂体系(如橄榄石+辉石体系)的高温高压相变实验研究,并在已有地球物理探测成果的基础上建立合理的地质-岩石学模型,对探讨中国东部地区上地幔复杂结构形成的物理机理,影响因素及其深部动力学机制具有重要意义.
Peridot is one of the main minerals in the upper mantle, and its phase transformation is of great significance for understanding the origin of the mantle discontinuities, the material composition and evolution of the entire mantle, the convection of the mantle, deep-seated subduction slab and other earth-deep dynamical problems In this study, the phase change experiments of olivine (Fo100 and Fo90) with two compositions at a pressure of 14.1 ~ 20GPa and a temperature of 1400 ℃ were carried out using a multi-anvil press at the Deep Earth Research Laboratory of China Earthquake Press. The pressure was 14.8 ~ At 15.6 GPa, both Fo90 and Fo100 were transformed into the wazirisite (α), whereas in the 14.1 GPa experiment, the Fo90 was completely transformed into the wazirisite and the Fo100 was still olivine (α) Species: crushed granular structure (particle size greater than 100μm) and a collection of microcrystals (crystallite size less than 10μm). The Waszierite Raman spectrum shows characteristic peaks of 722-72 and 917-919cm-1 The higher the pressure is, the more product appears in the experimental product as a micro-crystalline aggregate structure output of the Waszierite, indicating that the experimental pressure from the olivine phase transition boundary, the greater the density of the Valence stone nucleation, resulting in the system Gibbs free Can decline, high-pressure phase mineral particle growth is suppressed, but due to tile The nucleation and activation energy of the stone is very small, so there are a large number of the orezers in the experimental product which are produced by the aggregate of the microcrystal. The microstructure characteristics of the experimental product provide high temperature and pressure for explaining the appearance of the orezirite in the meteorite Experimental results show that when the pressure is 19.5 and 20GPa, the experimental product is the forest wood (γ), in which the pressure is 19.5GPa Fo100 Oviszite and Lynn Wood coexist in the experimental product Lynwood stone self-shaped granular (particle size (10 ~ 20μm), and the triple point structure is developed.779 and 840cmμ are the Raman peaks of the Lyndhurst stone.According to the results of this study and the previous seismic exploration results, the complex structure of the upper mantle in eastern China can not be characterized by a single olivine phase To explain, the phase transitions of other minerals (such as pyroxene-garnet) and their interaction with the olivine phase transformation may lead to the complex structure of the upper mantle in the region, thus further developing complex systems such as olivine + Pyroxene system) high temperature and high pressure phase transition experimental study, and based on the results of existing geophysical exploration to establish a reasonable geology - petrology model, to explore the formation of the upper mantle complex structure in eastern China physical Management, influencing factors and dynamic mechanism of deep significance.