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首页> 外文期刊>Contributions to Mineralogy and Petrology >How partial melts of mafic lower crust affect ascending magmas at oceanic ridges
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How partial melts of mafic lower crust affect ascending magmas at oceanic ridges

机译：如何在海洋山脊上影响迈克克下地壳的部分熔体

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We present experiments showing that the lower oceanic crust should melt efficiently and quickly when heated by hot ascending magmas. Average plagioclase-olivine and plagioclase-augite pairs from the lower crust at the Southwest Indian Ridge have melt-mineral saturation boundaries at 1,190 and 1,154 deg C, respectively, and melt rapidly (>0.01 mm/h) at 50 deg C or more above these temperatures. Melting experiments performed on olivine-plagioclase and augite-plagioclase mineral pairs from actual oceanic lower crustal rock samples and under conditions applicable to a MOR setting (1,220-1,330 deg C, 1 atm, quartz-fayalite-magnetite oxygen buffer, 0.25-24 h) indicate that the resulting disequilibrium melts are linear mixes of the mineral compositions. The rates of melting are slower than the rate of heat-diffusion into a sample and are approximated as: zeta = 2.43 x 10~(-26) x e~(0.004109 x T(deg C)) (m/s~(1/2)) for augite melted with plagioclase; zeta = 3.47 x 10~(-15) x e~(0.002041 x T(deg C)) for plagioclase melted with augite; and zeta= 1.79 x l0~(-21) x e~(0.0032 x T(deg C)) for plagioclase melted with olivine. Our results indicate that great care must be taken in backward models using basalt chemistry alone to explore mantle-melting processes, assuming only crystallization and fractionation during ascent, as partial melts may mix with intruded hot magma.
机译：我们提出了实验，表明低海洋地壳应该在热升华岩浆加热时融化。来自西南印度脊的下层地壳的平均普拉基酶 - 橄榄石和Plagioclase-upite对分别在1,190和1,154℃下具有熔融矿物饱和界限，并在50℃或更高时熔化（> 0.01mm / h）。这些温度。从实际海洋下层地壳岩样和适用于MOR环境的条件下，对橄榄石 - 普氏蛋白酶和消耗术 - Plagioclase矿物对进行熔融实验（1,220-1,330℃，1atm，石英 - 配盐磁铁矿氧气缓冲液，0.25-24小时）表明所得不平衡熔体是矿物组合物的线性混合物。熔化率比热扩散速率慢于样品，近似为：Zeta = 2.43×10〜（-26）xe〜（0.004109 x t（deg c））（m / s〜（1 / 2））对于奥伯特用​​Plagioclase融化; Zeta = 3.47 x 10〜（-15）×e〜（0.002041 x t（deg c））用upite融化的plagioclase;和Zeta = 1.79 x L0〜（-21）×e〜（0.0032 x t（deg c））用橄榄石熔化的plagioclase。我们的结果表明，使用玄武岩化学单独使用玄武岩化学的落后模型中的优点必须探索搭式熔化过程，假设仅在上升期间结晶和分馏，因为部分熔体可以与侵入的热岩浆混合。

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