Xiaoqinling District is an important gold-producing area in China.It ranks second to Jiaodong with regard to gold deposits.The uprising period of the Wenyu granitic pluton and the wall-rocks of the deposit,as well as ...Xiaoqinling District is an important gold-producing area in China.It ranks second to Jiaodong with regard to gold deposits.The uprising period of the Wenyu granitic pluton and the wall-rocks of the deposit,as well as the mineralizing depth and reserved place of gold ore bodies,are significant to ore exploration.Fission-track(FT)analysis of zircons and apatites of granitic rocks from the Wenyu granitic pluton shows that apatite FT(AFT)data modeling indicates a rapid cooling rate of 20°C/Ma from 138 to120 Ma after emplacement at 138 Ma.Thermal evolution and inversion curves suggest a secondary phase of fast cooling and uprising from 45 to 35 Ma,and 35 Ma,respectively,with a cooling rate of 6.7°C/Ma and a denudation quantity of^4.3 km.The last cooling phase took place from<4 Ma,with an average cooling rate of^11.3°C/Ma and a denudation amount of 1.3 km.Total exhumation quantity of 5.6 km and uprising elevation of 7.3 km are similar to the estimated results of fluid inclusions from the Dongtongyu and Wenyu gold deposits.The39Ar/40Ar dating of sericite from the fault planes of the Xunmadao-Xiaohe and Taiyao faults demonstrate two uprising activities of the ore-host metamorphic complex.The Huashan and Wenyu granitic plutons intensively occurred during 77 and 45 Ma,respectively.These data sets are valuable for understanding the uplifting process and for preserving gold ore bodies in the Xiaoqinling area,as well as for further studies on tectonic evolutions of the Taihua Complex and the Qinling-Dabie Orogen.展开更多
Petrographic evidence indicates that some of the ultrahigh-pressure (UHP) eclogites in Dabie Mountains area may be evolved from epidote amphibolite fades rocks recrystallized under ultrahigh pressure conditions. The e...Petrographic evidence indicates that some of the ultrahigh-pressure (UHP) eclogites in Dabie Mountains area may be evolved from epidote amphibolite fades rocks recrystallized under ultrahigh pressure conditions. The evolution of the erogenic belt had eventually resulted in the uplift of the metamorphic terrane soon after the peak metamorphic ultrahigh pressure stage of collision. During the uplift the ultrahigh-pressure metamorphic rocks were superimposed by nearly isothermal decompressive retrograde metamorphism through high-pressure (HP) edogite fades to amphibolite fades. Some of them were followed by epidote amphibolite fades and greenschist fades of metamorphism, while others were followed by epidote blueschist fades and then lowered to greenschist fades. Accompanying the retrogressive metamorphism. the rocks underwent at least 6 stages of deformation ranging from plastic to brittle character. The decompressive P-T path is also shown in the evolution of fluid inclusions: the entrapment pressure is estimated as 2.05 GPa and then isothermally decreased to lower than 1.0 GPa. The salinity of the late fluid is obviously decreased. Its ratios of Br/Cl and I/Cl are higher than those of sea water and bulk earth, suggesting a deep source of the fluid.展开更多
基金supported by the National Natural Science Foundation of China(90814006)
文摘Xiaoqinling District is an important gold-producing area in China.It ranks second to Jiaodong with regard to gold deposits.The uprising period of the Wenyu granitic pluton and the wall-rocks of the deposit,as well as the mineralizing depth and reserved place of gold ore bodies,are significant to ore exploration.Fission-track(FT)analysis of zircons and apatites of granitic rocks from the Wenyu granitic pluton shows that apatite FT(AFT)data modeling indicates a rapid cooling rate of 20°C/Ma from 138 to120 Ma after emplacement at 138 Ma.Thermal evolution and inversion curves suggest a secondary phase of fast cooling and uprising from 45 to 35 Ma,and 35 Ma,respectively,with a cooling rate of 6.7°C/Ma and a denudation quantity of^4.3 km.The last cooling phase took place from<4 Ma,with an average cooling rate of^11.3°C/Ma and a denudation amount of 1.3 km.Total exhumation quantity of 5.6 km and uprising elevation of 7.3 km are similar to the estimated results of fluid inclusions from the Dongtongyu and Wenyu gold deposits.The39Ar/40Ar dating of sericite from the fault planes of the Xunmadao-Xiaohe and Taiyao faults demonstrate two uprising activities of the ore-host metamorphic complex.The Huashan and Wenyu granitic plutons intensively occurred during 77 and 45 Ma,respectively.These data sets are valuable for understanding the uplifting process and for preserving gold ore bodies in the Xiaoqinling area,as well as for further studies on tectonic evolutions of the Taihua Complex and the Qinling-Dabie Orogen.
基金Project supported by the Doctorate Special Fund of State Education Commission of China and the National Natural Science Foundation of China.
文摘Petrographic evidence indicates that some of the ultrahigh-pressure (UHP) eclogites in Dabie Mountains area may be evolved from epidote amphibolite fades rocks recrystallized under ultrahigh pressure conditions. The evolution of the erogenic belt had eventually resulted in the uplift of the metamorphic terrane soon after the peak metamorphic ultrahigh pressure stage of collision. During the uplift the ultrahigh-pressure metamorphic rocks were superimposed by nearly isothermal decompressive retrograde metamorphism through high-pressure (HP) edogite fades to amphibolite fades. Some of them were followed by epidote amphibolite fades and greenschist fades of metamorphism, while others were followed by epidote blueschist fades and then lowered to greenschist fades. Accompanying the retrogressive metamorphism. the rocks underwent at least 6 stages of deformation ranging from plastic to brittle character. The decompressive P-T path is also shown in the evolution of fluid inclusions: the entrapment pressure is estimated as 2.05 GPa and then isothermally decreased to lower than 1.0 GPa. The salinity of the late fluid is obviously decreased. Its ratios of Br/Cl and I/Cl are higher than those of sea water and bulk earth, suggesting a deep source of the fluid.
