Experimental simulation of orthopyroxene enrichment and carbonation in the suprasubduction mantle under the influence of H2O, CO2, and SiO2
Experimental simulation of orthopyroxene enrichment and carbonation in the suprasubduction mantle under the influence of H2O, CO2, and SiO2
复制标题
H2O、CO2、SiO2影响下俯冲地幔中斜方辉石富集及碳化的实验模拟
DOI：
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发表时间：
2013
影响因子：
0.8
通讯作者：
V. Yapaskurt
中科院分区：
文献类型：
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作者：
A. Perchuk;V. Yapaskurt
俯冲板块和俯冲上地幔边界的热梯度和化学梯度导致了各种鲜为人知的地质过程。本文报道了在“热”俯冲带的P-t条件下，橄榄石（Ol，地幔类似物）与碳酸盐蓝闪石片岩（Gls，俯冲地壳上层类似物）相互作用的模拟实验结果。实验在温度梯度条件（tminGls = 720°C和tmaxOl = 1000°C）下在P = 25千巴的压力下进行，并且在对应于梯度实验中材料之间的边界的t = 800°C的恒定温度下进行。用两种不同的方法得到的实验数据的比较表明，温度梯度实验再现了在等温条件下的片岩橄榄石相互作用的字符，并提供了额外的信息，温度对矿物反应的影响。实验产物中的斜方辉石存在于不同的结构位置，在橄榄石带的底部形成一层（有或没有菱镁矿），或在橄榄石颗粒的边界形成单独的颗粒并与菱镁矿共生。斜方辉石的形成和碳酸盐的再沉积是由橄榄石与水成流体组分SiO_2和CO_2的反应来描述的，反应条件分别为a_{SiO_2 } = 0.23$$和a_{CO_2 } = 0.07$$。在这样的热力学条件下计算的流体中的二氧化硅含量为0.39mol/kg H2O。考虑到这些参数，在美国西北部卡斯卡迪亚俯冲带下行板片深度为1.80 km处的估计SiO2通量为180 t/yr，非常温和（考虑深度水平）的水流体通量为每年每公里100万摩尔。现代概念的对流在地幔楔俯冲板发起的建议，斜方辉石富集的超镁铁岩必须发生以上的挥发性组分和二氧化硅从板片和更深层次的俯冲带的释放区域。
Thermal and chemical gradients at the boundary of a subducting plate and suprasubduction mantle lead to a variety of poorly understood geologic processes. This paper reports the results of experiments simulating interaction between olivine (Ol, mantle analog) and carbonated glaucophane schist (Gls, analog of the upper layer of the subducted crust) under the P-t conditions of a ‘hot’ subduction zone. The experiments were carried out at a pressure of P = 25 kbar under temperature gradient conditions (tminGls = 720°C and tmaxOl = 1000°C) and at a constant temperature of t = 800°C corresponding to the boundary between the materials in the gradient experiment. A comparison of experimental data obtained using two different methods showed that the temperature gradient experiment reproduced the character of schist-olivine interaction under isothermal conditions and provided additional information on the effect of temperature on mineral reactions. Orthopyroxene occurs in the experimental products in different textural positions, forming a layer (with or without magnesite) at the base of the olivine zone or separate grains and intergrowths with magnesite at the boundary of olivine grains. The development of orthopyroxene and carbonate redeposition are described by reactions between olivine and aqueous fluid components, SiO2 and CO2, at $$a_{SiO_2 } = 0.23$$ and $$a_{CO_2 } = 0.07$$. The calculated silica content in the fluid under such thermodynamic conditions is 0.39 mol/kg H2O. Given these parameters, the estimated SiO2 flux at a depth of ∼80 km from the downgoing slab of the Cascadia subduction zone in the northwester United States is 180 t/yr at a very moderate (for the considered depth level) aqueous fluid flux of one million moles per year per kilometer. Modern concepts on convective flows initiated by a subducting slab in the mantle wedge allow us to suggest that orthopyroxene-enriched ultramafic rocks must occur both above the areas of the release of volatile components and silica from the slab and at deeper levels of subduction zones.
活塞-气缸组件中的温度分布：数值模拟和实验室实验
影响因子：
2.1
作者：
通讯作者：
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