Thermodynamic Modeling of Crustal Melting Using Xenolith Analogs from the Cortlandt Complex, New York, USA

摘要: Emplacement of gabbroic magmas the Cortlandt Complex, New York, induced rapid (less than 5 years) heating pelitic schist protoliths (up to � 1200 Ca t� 0� 9 GPa). Xenoliths entrained within mafic melt experienced significant melting and melt-segregation, now represented as a series complex fabrics structures comprising Si-rich veins an Al-rich, Si-poor residuum (a typical assemblage is spinel‐magnetite‐ilmeno-hematite‐sillimanite 6 sapphirine corundum). Subtle microscopic textures in include corundum‐magnetite symplectites, which are interpreted be result oxidative breakdown hercynite component spinel during cooling. Aluminous orthopyroxene selvages have typically grown along contact between quartzofeldspathic ‘melt’. Hybrid monzonorite monzodiorite crop out near xenoliths represent assimilation by magma some partial produced from xenoliths. Equilibrium-melting batch-melting thermodynamic models track evolution schist, its upon heating, extraction. We introduce ‘filter-pressing’ cooling calculation simulate crystallization veins. Modeling results yield following: (1) initial that, when mixed with estimated composition melt, produces hybrid igneous rock consistent found xenolith; (2) high-T that mineral texturally compositionally corresponds veinlets retained samples xenolith interiors; (3) residual material oxidized, resembles aluminous assemblages residuum. predicts early formation, Al content analyzed selvage pyroxene. propose this pyroxene reflects primary phase rather reaction-rim margins against matrix.