大兴安岭托河林场毕利亚山碱长花岗岩黑云母地球化学特征及地质意义

根据大兴安岭毕利亚山碱长花岗岩黑云母的电子探针(EPMA)测试结果,对黑云母的化学成分特征、成因类型及结晶时的温度和氧逸度进行了研究,并探讨岩浆源区的性质及成岩背景。毕利亚山碱长花岗岩黑云母具有高Si(SiO_2:39.876%~42.419%)、富Mg(MgO:18.138%~20.02%)、贫Fe(FeO~t:10.549%~11.468%)特征,属镁质黑云母;黑云母的结晶温度为590℃~650℃,且具有较高的氧逸度。其∑Al的值为1.01~1.044,Fe/(Mg+Fe)的值为0.228~0.262。Mg/(Mg+Fe~(2+)+Mn)的值为0.673~0.834,FeO~t/(FeO~t+MgO)的值为0.345~0.387,指示了其岩浆源区为富镁的岩石圈地幔,并且在岩浆演化过程中发生混染作用。

Geochemical characteristics and geological significance of biotites from Bileashan alkali-feldspar granite of Tuohe forest farm in Da Hinggan mountains

Based on the electron microprobe (EPMA) of biotites from Bileashan alkali-feldspar granite in the Da Hinggan mountains, the authors studied the chemical composition, genetic types, formation temperature and oxygen fugacity of biotites and discussed the characteristics and diagenetic background of magma sources. The studied biotites are characterized by high SiO2 (39.876%~42.419%) and Mg(18.138%~20.02%), low FeOt (10.549%~11.468%), which belongs to Mg-biotites. The crystallization temperature of biotites ranges from 590℃ to 650℃, with high oxygen fugacity. Total Al ranges from 1.01 to 1.044 and Fe/(Mg+Fe) varies from 0.228 to 0.262, with Mg/(Mg+Fe2++Mn) and FeOt/(FeOt+MgO) in the ranges of 0.673 to 0.834 and 0.345 to 0.387, respectively, suggesting magma source of Mg-riched lithospheric mantle, with contamination during the magma evolution.