中-低压泥质岩在KFMASH体系中的相平衡关系  

Phase equilibria for metapelites in the system K_2O-FeO-MgO-Al_2O_3-SiO_2-H_2O (KFMASH)

作　　者：张翠光[1] 魏春景[1] 

机构地区：[1]北京大学地质学系,北京100871

出　　处：《岩石学报》2004年第3期725-736,共12页Acta Petrologica Sinica

基　　金：国家自然科学基金(编号:40172031)

摘　　要：利用内部一致热力学数据库、可靠的固溶体活度模型,用有关程序THERMOCALC3.1计算了KFMASH(K_2O-FeO-MgO-Al_2O_3-SiO_2-H_2O)体系和亚体系KMASH、KFASH中的岩石成因格子。温压范围为P=0.05～1.2GPa,T=450～900℃,包括黑云母、白云母、钾长石、绿泥石、硬绿泥石、十字石、堇青石、斜方辉石、石榴石、尖晶石、红柱石、蓝晶石、矽线石、石英(过量)、熔体和水(固相线以下水过量、固相线以上水不过量)。利用这些成因格子以及所计算的AFM图、P-T视剖面图,可以很好地阐明泥质岩石中低压变质作用的相平衡关系及P-T条件。所计算的结果与岩石学研究非常吻合,能解释从绿片岩相至麻粒岩相的一系列变化。尤其是熔体的引入,使我们能够定量计算高角闪岩相以上出现的混合岩化过程。Using the internally-consistent thermodynamic dataset of Holland and updated models of activity-composition relation for solid solutions, petrogenetic grids in the model system KFMASH ( K2O-FeO-MgO-Al2O3-SiO2-H2O) and the subsystems KMASH and KFASH have been calculated with the software THERMOCALC 3.1 in the P-T range 0.05 similar to 1.2 GPa and 450 similar to 900degreesC, involving biotite, muscovite, K-feldspar, chlorite, chloritoid, staurolite, cordierite, garnet, orthopyroxene, spinel, andalusite, sillimanite, kyanite, quartz (in excess), melt and H2O (in excess for subsolidus part, not excess for supersolidus part). These grids, together with calculated AFM compatibility diagrams and P-T pseudosections are shown to be powerful tools for delineating the phase equilibria and P-T conditions of pelitic low-medium pressure metamorphism. The calculated equilibria and mineral assemblages predicted by the grid is consistent with successive prograde development in fields. Especially, adding melts makes it possible to interpret quantitatively the wide migmatization in fields.

关 键 词：KFMASH体系 泥质岩石 岩石成因格子 THERMOCALC 

分 类 号：P588.91[天文地球—岩石学]