本文在构造变形分析的基础上,利用共轭节理、断层擦痕和显微构造分析定量反演宁波地区燕山晚期构造应力场的应力方位,同时利用岩石破坏准则,方解石 e 双晶和变形石英的位错密度定量估算其差异应力。进而结合现今地应力测量结果分析,采...本文在构造变形分析的基础上,利用共轭节理、断层擦痕和显微构造分析定量反演宁波地区燕山晚期构造应力场的应力方位,同时利用岩石破坏准则,方解石 e 双晶和变形石英的位错密度定量估算其差异应力。进而结合现今地应力测量结果分析,采用有限元模拟法,探讨宁波地区燕山晚期以来区域应力场的分布及其演化关系,从而为宁波地区地壳稳定性和区域稳定性研究提供重要依据。展开更多
绍兴—江山断裂带为江南古陆与华夏古陆之间分划性界面。它的主带及与两侧古陆相接的边缘带都由石英质糜棱岩及千糜岩所组成。断裂带变形岩石的动力学分析表明,它至少经历了两个变形时期,主变形期为塑性变形,后期有脆性变形迭加。主变...绍兴—江山断裂带为江南古陆与华夏古陆之间分划性界面。它的主带及与两侧古陆相接的边缘带都由石英质糜棱岩及千糜岩所组成。断裂带变形岩石的动力学分析表明,它至少经历了两个变形时期,主变形期为塑性变形,后期有脆性变形迭加。主变形期石英的 TEM 研究揭示了它的位错亚结构以亚颗粒和重结晶颗粒发育为特征,位错密度较低(2.26×10~4cm^(-2)),亚颗粒粒径为2—3μm,重结晶粒径为15—30μm,属高应变位错蠕变机制。运用浸蚀法(二氟化铵为浸蚀剂),统计石英重结晶粒径,推算出差应力值为57—92MPa,并且从断裂带北西侧向南东侧有增高之势,同时多硅白云母的 b_0值也趋升高,为8.9950,9.0144—9.033,变质相从低压型—中压型向高压型过渡。展开更多
The oxygen isotope composition of minerals from quartz veins and host eclogites in the Dabie terrane was measured in order to place geochemical constraints on the origin and transport of metamorphic fluid. The results...The oxygen isotope composition of minerals from quartz veins and host eclogites in the Dabie terrane was measured in order to place geochemical constraints on the origin and transport of metamorphic fluid. The results are discussed together with structural and petrological relationships between quartz vein and wallrock. The quartz veins can be temporally classified into three groups: (1) synmetamorphic vein which would be formed prior to eclogite-facies recrystallization when they were exhumated from mantle depths to deep crustal levels; (2) early retrogressive vein which was formed in the early stage of eclogite exhumation subsequent to the recrystallization, the vein-forming fluid is still relevant to the eclogites; (3) late retrogressive vein which was formed in the late stage of eclogite exhumation from deep crustal to upper crustal levels, oxygen isotope fractionation between vein quartz and host eclogite significantly deviates from equilibrium values and the vein-forming fluid was principally derived from granitic gneiss hosting the eclogites. For the synmetamorphic vein, it appears that local advective transport of fluid is the predominant mechanism in the processes of vein precipitation; the scale of oxygen isotope homogenization within the veins is much larger than that within the associated eclogites. The vein-forming fluid would be derived from the exsolution of dissolved hydroxyls within eclogite minerals due to significant pressure decrease. Fluid flow prior to the eclogite-facies recrystallization and the early retrogression may occur mainly along pressure gradients.展开更多
Using Fourier transform infrared spectroscopy(FTIR),we measured water contents in quartz and feldspar for four kinds of felsic rocks,i.e.,undeformed granite,banded granitic gneiss,fine-grained felsic mylonite,and fine...Using Fourier transform infrared spectroscopy(FTIR),we measured water contents in quartz and feldspar for four kinds of felsic rocks,i.e.,undeformed granite,banded granitic gneiss,fine-grained felsic mylonite,and fine-grained quartz-mica schist,collected from Pengguan Complex and Kangding Complex in the Longmenshan tectonic zone,Sichuan,China.The absorbance spectra suggest that water in coarse-grained quartz and feldspar of undeformed granite and banded granitic gneiss occurs mainly as hydroxyl in crystal defects,and water in most of fine-grained quartz and feldspar of felsic mylonite is molecular water in inclusions and liquid-type water in grain boundaries,but in some cases it still occurs as hydroxyl in crystal defects.Water content of quartz in undeformed granite is 0.001 wt%-0.009 wt %,and that of feldspar 0.005 wt%-0.02 wt%.The banded granitic gneiss shows water contents of 0.002 wt%-0.011 wt% in quartz and 0.012 wt%-0.036 wt% in feldspar.Quartz ribbon and feldspar ribbon in fine-grained felsic mylonite show that their water contents are similar to those of coarse-grained quartz and feldspar in granite,0.002 wt%-0.011 wt%,and 0.004 wt%-0.02 wt%,respectively.Water contents of fine-grained quartz and feldspar are respectively 0.004 wt%-0.02 wt% and 0.012 wt%-0.06 wt%.Water content of quartz in fine-grained quartz-mica schist is 0.007 wt%-0.15 wt%.Water-bearing minerals display much higher water contents than those of nominally anhydrous minerals,and the percentage of water-bearing minerals in felsic rocks increases with the strain of rocks.These new data indicate that hydroxyl in crystal defects has basically not been released during the shear deformation,and on the contrary,the increase in molecular water in inclusions and liquid-type water in grain boundaries as well as water-bearing minerals after shear deformation leads to a significant increase of the water content in deformed rocks.Based on data of creep tests,it is inferred here that the fine-grained mylonites with more water have much lower strength than that of the weakly deformed coarse-grained rocks in the middle crust,and this indicates that trace amount of water significantly helped develop the ductile shear zone.展开更多
文摘本文在构造变形分析的基础上,利用共轭节理、断层擦痕和显微构造分析定量反演宁波地区燕山晚期构造应力场的应力方位,同时利用岩石破坏准则,方解石 e 双晶和变形石英的位错密度定量估算其差异应力。进而结合现今地应力测量结果分析,采用有限元模拟法,探讨宁波地区燕山晚期以来区域应力场的分布及其演化关系,从而为宁波地区地壳稳定性和区域稳定性研究提供重要依据。
文摘绍兴—江山断裂带为江南古陆与华夏古陆之间分划性界面。它的主带及与两侧古陆相接的边缘带都由石英质糜棱岩及千糜岩所组成。断裂带变形岩石的动力学分析表明,它至少经历了两个变形时期,主变形期为塑性变形,后期有脆性变形迭加。主变形期石英的 TEM 研究揭示了它的位错亚结构以亚颗粒和重结晶颗粒发育为特征,位错密度较低(2.26×10~4cm^(-2)),亚颗粒粒径为2—3μm,重结晶粒径为15—30μm,属高应变位错蠕变机制。运用浸蚀法(二氟化铵为浸蚀剂),统计石英重结晶粒径,推算出差应力值为57—92MPa,并且从断裂带北西侧向南东侧有增高之势,同时多硅白云母的 b_0值也趋升高,为8.9950,9.0144—9.033,变质相从低压型—中压型向高压型过渡。
基金the Ministry of Science and Technology of China (Grant No. G1999075503) and the Chinese Academy of Sciences (Grant No. KZCX2-107).
文摘The oxygen isotope composition of minerals from quartz veins and host eclogites in the Dabie terrane was measured in order to place geochemical constraints on the origin and transport of metamorphic fluid. The results are discussed together with structural and petrological relationships between quartz vein and wallrock. The quartz veins can be temporally classified into three groups: (1) synmetamorphic vein which would be formed prior to eclogite-facies recrystallization when they were exhumated from mantle depths to deep crustal levels; (2) early retrogressive vein which was formed in the early stage of eclogite exhumation subsequent to the recrystallization, the vein-forming fluid is still relevant to the eclogites; (3) late retrogressive vein which was formed in the late stage of eclogite exhumation from deep crustal to upper crustal levels, oxygen isotope fractionation between vein quartz and host eclogite significantly deviates from equilibrium values and the vein-forming fluid was principally derived from granitic gneiss hosting the eclogites. For the synmetamorphic vein, it appears that local advective transport of fluid is the predominant mechanism in the processes of vein precipitation; the scale of oxygen isotope homogenization within the veins is much larger than that within the associated eclogites. The vein-forming fluid would be derived from the exsolution of dissolved hydroxyls within eclogite minerals due to significant pressure decrease. Fluid flow prior to the eclogite-facies recrystallization and the early retrogression may occur mainly along pressure gradients.
基金supported by National Natural Science Foundation of China(Grant No.40972146)State Key Laboratory of Earthquake Dynamics(Grant Nos. LED2009A01,LED2008A03)
文摘Using Fourier transform infrared spectroscopy(FTIR),we measured water contents in quartz and feldspar for four kinds of felsic rocks,i.e.,undeformed granite,banded granitic gneiss,fine-grained felsic mylonite,and fine-grained quartz-mica schist,collected from Pengguan Complex and Kangding Complex in the Longmenshan tectonic zone,Sichuan,China.The absorbance spectra suggest that water in coarse-grained quartz and feldspar of undeformed granite and banded granitic gneiss occurs mainly as hydroxyl in crystal defects,and water in most of fine-grained quartz and feldspar of felsic mylonite is molecular water in inclusions and liquid-type water in grain boundaries,but in some cases it still occurs as hydroxyl in crystal defects.Water content of quartz in undeformed granite is 0.001 wt%-0.009 wt %,and that of feldspar 0.005 wt%-0.02 wt%.The banded granitic gneiss shows water contents of 0.002 wt%-0.011 wt% in quartz and 0.012 wt%-0.036 wt% in feldspar.Quartz ribbon and feldspar ribbon in fine-grained felsic mylonite show that their water contents are similar to those of coarse-grained quartz and feldspar in granite,0.002 wt%-0.011 wt%,and 0.004 wt%-0.02 wt%,respectively.Water contents of fine-grained quartz and feldspar are respectively 0.004 wt%-0.02 wt% and 0.012 wt%-0.06 wt%.Water content of quartz in fine-grained quartz-mica schist is 0.007 wt%-0.15 wt%.Water-bearing minerals display much higher water contents than those of nominally anhydrous minerals,and the percentage of water-bearing minerals in felsic rocks increases with the strain of rocks.These new data indicate that hydroxyl in crystal defects has basically not been released during the shear deformation,and on the contrary,the increase in molecular water in inclusions and liquid-type water in grain boundaries as well as water-bearing minerals after shear deformation leads to a significant increase of the water content in deformed rocks.Based on data of creep tests,it is inferred here that the fine-grained mylonites with more water have much lower strength than that of the weakly deformed coarse-grained rocks in the middle crust,and this indicates that trace amount of water significantly helped develop the ductile shear zone.
