The grain boundary conductivities of dry synthetic peridotite are conducted by virtue of YJ-3000t multi-anvil press and Solartron-1260 Impedance /Gain-phase Analyzer at conditions of 4.0 GPa, 1373 K and frequency rang...The grain boundary conductivities of dry synthetic peridotite are conducted by virtue of YJ-3000t multi-anvil press and Solartron-1260 Impedance /Gain-phase Analyzer at conditions of 4.0 GPa, 1373 K and frequency ranging from 10-2 to 106 Hz. The Fe2O3+Fe3O4,Ni+NiO,Fe+Fe3O4,Fe+FeO and Mo+MoO2 solid buffers are adopted to adjust展开更多
The Dabie UHP metamorphic belt, central China,contains two contrasting types of mafic-ultramafic complex. The Bixiling peridotite in the southern Dabie terrane contains abundant garnet (21.1-32.2 vol% )and thus ha... The Dabie UHP metamorphic belt, central China,contains two contrasting types of mafic-ultramafic complex. The Bixiling peridotite in the southern Dabie terrane contains abundant garnet (21.1-32.2 vol% )and thus has high CaO + Al2O3 (9.81-15.9 wt% ).……展开更多
The Beni Bousera peridotite massif(Internal Rif, Morocco),5 km in width and 15 km in length,is formed in a major part of spinel-bearing lherzolite rimed by a layer of garnet-bearing peridotite(100 m thick)which is in ...The Beni Bousera peridotite massif(Internal Rif, Morocco),5 km in width and 15 km in length,is formed in a major part of spinel-bearing lherzolite rimed by a layer of garnet-bearing peridotite(100 m thick)which is in direct contact with HP-HT granulite metamorphic rocks(16 kbar,860℃).According to recent detailed study,the shearing contact between these two formations shows the presence of serpentinite and展开更多
The northern extension of the Semailophiolite in the UAE is dominated by tectonic mantle peridotites and gabbros. The peridotites are mostly harzburgites with little lherzolites, and contain various intermittentveins,...The northern extension of the Semailophiolite in the UAE is dominated by tectonic mantle peridotites and gabbros. The peridotites are mostly harzburgites with little lherzolites, and contain various intermittentveins, dikes and pods. These veins, dikes and pods can be divided into three rock categories: the ultramafic group that includes dunites, chromitites and pyroxenites, the granitic dikes, and carbonate veins. Occurrences of these bodies are explicit and ubiquitous, but their distribution throughout the sequence is not consistent. Pyroxenites, chromitites, and granites occur in the upper half of the sequence, but are more pronounced and dominant close to the transition zone. Dunites pods and carbonate veins can be found at different stratigraphic levels.展开更多
Information on abundance and distribution of platinum\|group elements (PGE) in peridotite from ophiolite is relevant to understand the nature and evolution of the upper mantle. The ophiolite suite outcropping along th...Information on abundance and distribution of platinum\|group elements (PGE) in peridotite from ophiolite is relevant to understand the nature and evolution of the upper mantle. The ophiolite suite outcropping along the famous suture zone of Yarlung Zangbo River, Tibet, has attracted wide attention of geologists both in China and abroad. The Dagzhuka ophiolite of in the suture zone is thought to display a complete ophiolitic sequence. The peridotite from the Dazhuka ophiolite is composed of fairly fresh or unaltered lherzolite, harzburgite and minor dunite which are the upper mantle residuum formed by 15%～35% partial melting. In this paper we have mainly studied the abundance and distribution of PGE in the harzburgites and lherzolites. The harzburgites and lherzolites preserve total PGE contents of 28 37×10 -9 ～50 67×10 -9 respectively higher than Primitive mantle or the peridotite from some typical ophiolites and Alpine. They all have fractionated chondrite\|normalized PGE patterns with positive slopes from Ir to Pd (Fig.1), and Pd/Ir=1 13～2 40>1, Pd/Rh=2 23～7 49>1, and Pd/Pt=0 26～1 16 (average 0 67) higher than Primitive mantle (1 11, 2 35, 0 57) or CI\|chondrite (1 01, 2 73, 0 53). Consequently, the Dagzhuka peridotite are PGE\|enriched, but otherwise possess residual characteristics arising from a minimum of 15% partial melting. It is suggested that mantle residuum by partial melting have low total PGE contents, fractionated chondrite\|normalized PGE patterns with negative or slightly flat slopes from Ir to Pd, and Pd/Ir<1. But, the total PGE contents, chondrite\|normalized PGE patterns and Pt/Ir, Pd/Rh and Pd/Pt values of the Dagzhuka peridotite are completely inconsistent with a residual origin. Partial melting would have partitioned all sulfide in the source into the melt. In fact, no sulfide or silicate melt remained in the Dagzhuka peridotite. Therefore, PGE in Dagzhuka peridotite are not present in sulfides. The PGE\|enrichment and fractionation of the Dagzhuka peridotites seem to arise from mantle metasomatism of melts/fluid enrich incompatible elements include Pt and Pt, but not from residual or percolation of sulfides. The enrichment of Cs, Rb, Ba, Th, U and LREE in Dagzhuka peridotite also give a hint of the mantle metasomatism. The abundance and distribution of PGE in the peridotite from the Dagzhuka ophiolite show the nature and evolution of the Dagzhuka upper mantle are distinctive.展开更多
The subcritical crack growth and fracture toughness in peridotite, lherzolite and amphibolite were investigated with double torsion test. The results show that water-rock interaction has a significant influence on sub...The subcritical crack growth and fracture toughness in peridotite, lherzolite and amphibolite were investigated with double torsion test. The results show that water-rock interaction has a significant influence on subcritical crack growth. With water-rock interaction, the crack velocity increases, while the stress intensity factor declines, which illustrates that water-rock interaction can decrease the strength of rocks and accelerate the subcritical crack growth. Based on Charlse theory and Hilling & Charlse theory, the test data were analyzed by regression and the correlation coefficients were all higher than 0.7, which shows the correlation is significant. This illustrates that both theories can explain the results of tests very well. Therefore, it is believed that the subcritical crack growth attributes to the breaking of chemical bond, which is caused by the combined effect of the tensile stress and the chemical reaction between the material at crack tip and the corrosive agent. Meanwhile, water-rock interaction has a vital effect on fracture toughness. The fracture toughness of samples under atmospheric environment is higher than that of samples immersed in water. And water-rock interaction has larger influence on fracture toughness in amphibolite than that in peridotite and lherzolite.展开更多
文摘The grain boundary conductivities of dry synthetic peridotite are conducted by virtue of YJ-3000t multi-anvil press and Solartron-1260 Impedance /Gain-phase Analyzer at conditions of 4.0 GPa, 1373 K and frequency ranging from 10-2 to 106 Hz. The Fe2O3+Fe3O4,Ni+NiO,Fe+Fe3O4,Fe+FeO and Mo+MoO2 solid buffers are adopted to adjust
基金This study was supported by the Nature Science Foundation of China (40673002) .
文摘 The Dabie UHP metamorphic belt, central China,contains two contrasting types of mafic-ultramafic complex. The Bixiling peridotite in the southern Dabie terrane contains abundant garnet (21.1-32.2 vol% )and thus has high CaO + Al2O3 (9.81-15.9 wt% ).……
文摘The Beni Bousera peridotite massif(Internal Rif, Morocco),5 km in width and 15 km in length,is formed in a major part of spinel-bearing lherzolite rimed by a layer of garnet-bearing peridotite(100 m thick)which is in direct contact with HP-HT granulite metamorphic rocks(16 kbar,860℃).According to recent detailed study,the shearing contact between these two formations shows the presence of serpentinite and
文摘The northern extension of the Semailophiolite in the UAE is dominated by tectonic mantle peridotites and gabbros. The peridotites are mostly harzburgites with little lherzolites, and contain various intermittentveins, dikes and pods. These veins, dikes and pods can be divided into three rock categories: the ultramafic group that includes dunites, chromitites and pyroxenites, the granitic dikes, and carbonate veins. Occurrences of these bodies are explicit and ubiquitous, but their distribution throughout the sequence is not consistent. Pyroxenites, chromitites, and granites occur in the upper half of the sequence, but are more pronounced and dominant close to the transition zone. Dunites pods and carbonate veins can be found at different stratigraphic levels.
文摘Information on abundance and distribution of platinum\|group elements (PGE) in peridotite from ophiolite is relevant to understand the nature and evolution of the upper mantle. The ophiolite suite outcropping along the famous suture zone of Yarlung Zangbo River, Tibet, has attracted wide attention of geologists both in China and abroad. The Dagzhuka ophiolite of in the suture zone is thought to display a complete ophiolitic sequence. The peridotite from the Dazhuka ophiolite is composed of fairly fresh or unaltered lherzolite, harzburgite and minor dunite which are the upper mantle residuum formed by 15%～35% partial melting. In this paper we have mainly studied the abundance and distribution of PGE in the harzburgites and lherzolites. The harzburgites and lherzolites preserve total PGE contents of 28 37×10 -9 ～50 67×10 -9 respectively higher than Primitive mantle or the peridotite from some typical ophiolites and Alpine. They all have fractionated chondrite\|normalized PGE patterns with positive slopes from Ir to Pd (Fig.1), and Pd/Ir=1 13～2 40>1, Pd/Rh=2 23～7 49>1, and Pd/Pt=0 26～1 16 (average 0 67) higher than Primitive mantle (1 11, 2 35, 0 57) or CI\|chondrite (1 01, 2 73, 0 53). Consequently, the Dagzhuka peridotite are PGE\|enriched, but otherwise possess residual characteristics arising from a minimum of 15% partial melting. It is suggested that mantle residuum by partial melting have low total PGE contents, fractionated chondrite\|normalized PGE patterns with negative or slightly flat slopes from Ir to Pd, and Pd/Ir<1. But, the total PGE contents, chondrite\|normalized PGE patterns and Pt/Ir, Pd/Rh and Pd/Pt values of the Dagzhuka peridotite are completely inconsistent with a residual origin. Partial melting would have partitioned all sulfide in the source into the melt. In fact, no sulfide or silicate melt remained in the Dagzhuka peridotite. Therefore, PGE in Dagzhuka peridotite are not present in sulfides. The PGE\|enrichment and fractionation of the Dagzhuka peridotites seem to arise from mantle metasomatism of melts/fluid enrich incompatible elements include Pt and Pt, but not from residual or percolation of sulfides. The enrichment of Cs, Rb, Ba, Th, U and LREE in Dagzhuka peridotite also give a hint of the mantle metasomatism. The abundance and distribution of PGE in the peridotite from the Dagzhuka ophiolite show the nature and evolution of the Dagzhuka upper mantle are distinctive.
基金Project(51374246,51474249)supported by the National Natural Science Foundation of ChinaProject(2013FJ6002)supported by the Science-Technology Project of Science-Technology Department of Hunan Province,China
文摘The subcritical crack growth and fracture toughness in peridotite, lherzolite and amphibolite were investigated with double torsion test. The results show that water-rock interaction has a significant influence on subcritical crack growth. With water-rock interaction, the crack velocity increases, while the stress intensity factor declines, which illustrates that water-rock interaction can decrease the strength of rocks and accelerate the subcritical crack growth. Based on Charlse theory and Hilling & Charlse theory, the test data were analyzed by regression and the correlation coefficients were all higher than 0.7, which shows the correlation is significant. This illustrates that both theories can explain the results of tests very well. Therefore, it is believed that the subcritical crack growth attributes to the breaking of chemical bond, which is caused by the combined effect of the tensile stress and the chemical reaction between the material at crack tip and the corrosive agent. Meanwhile, water-rock interaction has a vital effect on fracture toughness. The fracture toughness of samples under atmospheric environment is higher than that of samples immersed in water. And water-rock interaction has larger influence on fracture toughness in amphibolite than that in peridotite and lherzolite.
