Melting Behavior of Mafic Lower Crust in Continental Arcs

Glazner我们要求一年的资金，以完成一项关于花岗岩和通常伴随着它们的大陆弧中的镁铁质岩石(闪长岩和辉长岩)之间关系的研究。在许多弧形中，花岗岩与同时代的镁铁质岩石具有强烈的同位素相似性，表明两套岩石通过分离结晶或部分熔融等分异过程联系在一起。镁铁质下地壳重熔是产生具有地幔同位素特征的花岗岩类岩浆的一种方式(但不是唯一的方式)。我们对不同K2O含量的角闪辉长岩和闪长岩的脱水熔融进行了研究，以探讨内华达山脉等地花岗岩类岩浆的来源。锡尔兰镁铁质岩石在8千巴压力下熔融实验，成功地产生了组成与普通I型花岗岩和花岗闪长岩相似的硅质至中间液体(包括K2O和Na2O)。我们要求提供资金以完成这项研究。将进行的工作将包括进一步的合成矿物相和玻璃的电子探针分析，实验玻璃的离子微探针分析，以及检验花岗岩可能来自镁铁质下地壳熔融的假设的地球化学模拟。

9805079GlaznerWe request one year of funding to complete a study of the relationships between granites and the mafic rocks (diorites and gabbros) commonly accompany them in continental arcs. In many arcs granites bear a strong isotopic resemblance to coeval mafic rocks, suggesting that the two suites are linked by a differentiation process such as fractional crystallization or partial melting. Remelting of mafic lower crust is one way (but not the only way) to generate granitoid magmas with mantle-like isotopic characteristics. We have undertaken a study of the dehydration melting of hornblende gabbros and diorites with variable K2O contents to investigate the origin of granitoid magmas of the Sierra Nevada batholith and elsewhere. Melting experiments at 8 kilobar pressure on Sierran mafic rocks have successfully produced silicic to intermediate liquids similar in composition (including K2O and Na2O) to common I-type granite and granodiorite. We request funding to complete this study. Work to be performed will include further electron microprobe analyses of synthesized mineral phases and glasses, ion microprobe analysis of experimental glasses, and geochemical modeling to test the hypothesis that the granites could be derived by melting of mafic lower crust.