Melting in the Sub-Arc Mantle: The Effects of H2O on Primary Magmas and the Spinel-to-Garnet Transition
Melting in the Sub-Arc Mantle: The Effects of H2O on Primary Magmas and the Spinel-to-Garnet Transition
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弧下地幔的熔化：H2O 对原生岩浆和尖晶石到石榴石转变的影响
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发表时间：
1994
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影响因子：
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通讯作者：
G. Gaetani
中科院分区：
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作者：
G. Gaetani
在俯冲带中，H2O在熔体生成过程中起着重要作用。H2O的影响在动态熔融环境中可能是复杂的，因为H2O含量将随着熔融程度的增加而连续变化。为了模拟熔融过程，必须发展的作用，变量H20含量和变量地幔残留物的定量理解。该模型必须能够恢复地幔残余组合橄榄石+斜方辉石+单斜辉石_尖晶石_。角闪石_石榴石（原生岩浆）作为压力和H2O含量的函数。同样重要的是了解在各种压力-温度条件下H20对地幔相稳定性的影响。最近的实验工作表明，在地幔橄榄岩中，H2O的存在使石榴石稳定在较低的压力下（Gaetani和格罗夫，1993年）。在这里，我们报告的结果H2O-不饱和熔融实验在10-16千巴。这些实验被设计为确定在一定压力范围内的初级maLmaas的H2O-欠饱和液相线的温度，以及含有6wt%H2O的地幔熔体的组成。此外，结果可以用来约束的压力下尖晶石石榴石的转变发生在地幔中的含水条件下。
In subduction zone settings H20 plays an important role in the melt generation process. The effects of H20 are likely to be complex in a dynamic melting environment, because H20 contents will vary continuously with increasing degree of melting. In order to model the melting process, a quantitative understanding of the role of variable H20 content and variable mantle residue composition must be developed. The model must be capable of recovering liquidus temperatures and compositions of melts saturated with a mantle residual assemblage of olivine + orthopyroxene + clinopyroxene _ spinel _.+ amphibole _ garnet (primary magmas) as a function of pressure and H20 content. Equally important is understanding the effect of H20 on the stability of mantle phases under various pressure-temperature conditions. Recent experimental work indicates that the presence of H20 stabilizes garnet to lower pressures in mantle peridotlte (Gaetani and Grove, 1993). Here we report the results of H20-undersaturated melting experiments performed at 10-16 kbar. These experiments were designed to determine the temperature of the H20-undersaturated liquidus of primary maLmaas over a range of pressures, and the compositions of mantle melts containing 6 wt% H20. Further, the results can be used to constrain the pressure at which the spinel-togarnet transition occurs in the mantle under hydrous conditions.