论文部分内容阅读
Study of micro-area chemical compositions indicates that phengite in albite gneiss from hole ZK2304 of the Donghai region has evident compositional zoning. SiO2 and tetrahedrally coordinated Si contents decrease, and Al2O3, AlIV and AlVI contents increase gradually from core to rim. However, K2O, MgO and FeO contents basically remain unchanged from core to rim. According to P-T estimates obtained from geothermometers and barometers, combined with previous experimental data, the core belt (micro-area I) of phengite was formed at T=637-672℃ and P=1.55-1.73 GPa, and the transitional belt (micro-area II) of the phengite were formed at r=594-654℃ and P=1.35-1.45 GPa. Towards the rim belt (micro-area III), the temperature decreased slightly, but the pressure decreased rapidly with r=542-630℃ and P=1.12-1.19 GPa. The P-T evolution path recorded by the compositional zoning of phengite is characterized by significant near-isothermal decompression, revealing that the gneiss has. undergone high-pressure-ultrahi
Study of micro-area chemical compositions indicates that phengite in albite gneiss from hole ZK2304 of the Donghai region has emerged compositional zoning. SiO2 and tetrahedrally coordinated Si contents decrease, and Al2O3, AlIV and AlVI contents increase gradually from core to rim. However, K2O , Based on PT estimates obtained from geothermometers and barometers, combined with previous experimental data, the core belt (micro-area I) of phengite was formed at T = 637-672 ° C and P = 1.55-1.73 GPa, and the transitional belt (micro-area II) of the phengite were formed at r = 594-654 ° C and P = 1.35-1.45 GPa. Towards the rim belt decreased slightly, but the pressure decreased rapidly with r = 542-630 ° C and P = 1.12-1.19 GPa. The PT evolution path recorded by the compositional zoning of phengite is characterized by significant near-isothermal decompression, revealing that the gneiss has. undergonehigh-pressure-ultrahi