Carbonated sediment–peridotite interaction and melting at 7.5–12 GPa
Carbonated sediment–peridotite interaction and melting at 7.5–12 GPa
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碳化沉积物与橄榄岩的相互作用以及 7 5â12 GPa 下的熔化
DOI：
10.1016/j.lithos.2014.05.010
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发表时间：
2014
期刊：
影响因子：
3.5
通讯作者：
Höfer
中科院分区：
文献类型：
--
作者：
Bulatov;Girnis;Gerdes;Höfer
为了更好地了解深俯冲带过程，在7.5-12 GPa和900-1400 °C条件下，利用多砧实验装置研究了模型沉积物与橄榄岩之间的相互作用。使用了两种含H2O和CO2的合成材料，类似于Plank和Langmuir（1998）的GLOSS，具有不同的K/Na比。橄榄岩混合物由天然橄榄石、斜方辉石和来自金伯利岩捕虏体的石榴石组成。将沉积物（下图）和橄榄岩（上图）装入重新内衬的Pt胶囊中，并暴露于恒定压力和温度下24-72小时。用纯泥沙混合物进行了几个实验。实验产物经EPMA和LA ICPMS分析表明，纯沉积物熔融在固相线附近产生钙碱性碳酸盐熔体，高温下产生富含SiO2的液体。残留矿物组合以柯石英/中石英、石榴石、蓝晶石和硬玉为主。橄榄岩-沉积物相互作用导致（1）变质橄榄岩带中的橄榄石被低钙辉石和菱镁矿取代，（2）形成含低钙辉石和柯石英/方石英的过渡富石榴子石带，（3）变质沉积层中蓝晶石的消失和碳酸盐的稳定。橄榄岩带转变为低钙辉石-石榴石集合体，其石榴石/辉石比随温度升高而增加。沉积带随温度的升高由柯石英/中石英+硬玉+石榴石+碳酸盐+金红石向柯石英/中石英+硬玉+石榴石演化。Si从沉积物向橄榄岩的迁移和Mg、Fe从橄榄岩向沉积物的迁移是主要的。在相互作用实验中产生的熔体的组成不同于从纯沉积物熔融在较高的Mg和Si含量和低得多的Ca。微量元素之间的分配系数（D）残留矿物（辉石，石榴石，碳酸盐，锆石，金红石和SiO2多晶型）和熔体在几个实验中测定。建模使用所获得的D值表明，橄榄岩的相互作用增强稀土元素分馏的沉积物来源的熔体由于蓝晶石的石榴石的替代。过渡带和变质沉积带中硬玉辉石的滞留抑制了Na的迁移，导致高K/Na液体的形成。碳酸盐稳定性的提高可能有利于CO2的深度再循环和H2O与CO2的解耦。研究表明，由沉积物-橄榄岩相互作用和熔融作用产生的石榴石-单斜辉石残留物与世界上几个金伯利岩管中报道的高MgO含金刚石榴辉岩相似。
To gain a better insight into deep subduction-zone processes, the interaction between model sediment and peridotite was experimentally studied using a multianvil apparatus at 7.5–12 GPa and 900–1400 °C. Two H2O- and CO2-bearing synthetic materials similar to GLOSS of Plank and Langmuir (1998) with different K/Na ratios were used. The peridotite (harzburgite) mixture consisted of natural olivine, orthopyroxene and garnet from kimberlite-derived xenoliths. Sediment (below) and peridotite (above) were packed into a Re-lined Pt capsule and exposed to constant pressure and temperature for 24–72 h. Several experiments were conducted with pure sediment mixtures. The experimental products were analyzed by EPMA and LA ICP MS. Pure sediment melting produces Ca–alkali carbonatite melts near the solidus and liquids richer in SiO2at high temperatures. The residual mineral assemblage is dominated by coesite/stishovite, garnet, kyanite and jadeite. Peridotite–sediment interaction results in (1) replacement of olivine in the metaperidotite zone by low-Ca pyroxene and magnesite, (2) formation of a transitional garnet-rich zone containing low-Ca pyroxene and coesite/stishovite, and (3) disappearance of kyanite and stabilization of carbonate in the metasediment layer. The peridotite zone is transformed into a low-Ca pyroxene–garnet aggregate, and its garnet/pyroxene ratio increases with increasing temperature. The sediment zone evolves with increasing temperature from coesite / stishovite + jadeite + garnet + carbonate + rutile to coesite / stishovite + jadeite + garnet. Mass transfer is dominated by Si flux from sediment to peridotite and Mg and Fe from peridotite to sediment. The composition of the melts produced in the interaction experiments differs from that from pure sediment melting in higher Mg and Si contents and much lower Ca. Trace element partition coefficients (D) between residual minerals (pyroxenes, garnet, carbonate, zircon, rutile and SiO2polymorphs) and melts were determined in several experiments. Modeling using the obtained D values showed that interaction with peridotite enhances REE fractionation in sediment-derived melt owing to the replacement of kyanite by garnet. The retention of jadeitic pyroxene in the transitional and metasediment zones depresses Na mobility and leads to the formation of high-K/Na liquids. The increasing stability of carbonate in the metasediment may be favorable for deep CO2recycling and decoupling of H2O and CO2. It was shown that the garnet–clinopyroxene residua produced by sediment–peridotite interaction and melting are similar to high-MgO diamond-bearing eclogites reported from several kimberlite pipes worldwide.
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影响因子：
3.5
作者：
Girnis, A. V.;Bulatov, V. K.;Hoefer, H. E.
通讯作者：
Hoefer, H. E.
影响因子：
3.5
作者：
Belousova, EA;Griffin, WL;Fisher, NI
通讯作者：
Fisher, NI
芬兰东部 Lahtojoki 金伯利岩管中两块含金刚石榴辉岩捕虏体的岩石学
影响因子：
3.5
作者：
P. Peltonen;K. Kinnunen;H. Huhma
通讯作者：
H. Huhma
影响因子：
3.1
作者：
Whitney, Donna L.;Evans, Bernard W.
通讯作者：
Evans, Bernard W.
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
影响因子：
0.8
作者：
A. Perchuk;V. Yapaskurt
通讯作者：
V. Yapaskurt