Isotope dating, hornblende geobarometer, fission-track analysis and fluid inclusion homogeneous temperature analysis have been applied to Caledonian, Variscan and Yenshan plutons in Bei Huaiyang (BHY) and Dabie erogen...Isotope dating, hornblende geobarometer, fission-track analysis and fluid inclusion homogeneous temperature analysis have been applied to Caledonian, Variscan and Yenshan plutons in Bei Huaiyang (BHY) and Dabie erogenic belt (DOB), and the emplaced depths and ages of these plutons have been obtained in order to obtain differential uplift time and uplift heights between BHY and DOB since late Paleozoic era. BHY had experienced three stages of uplift (C1-C2, T-J2, J3-K1) and its total uplift height is about 10 km, but, DOB had only experienced two stages of uplift (T-J2, J3-K1) and its maximum uplift height is more than 15 km. BHY uplift occurred mainly before the mid-Jurassic (about 150 Ma), but DOB uplift took place after the mid-Jurassic (about 150 Ma).展开更多
The North Dabie complex unit （NDC） is a widely exposed petro-tectonic unit. To understand post-orogenic uplift history and mechanism of the Dabie orogenic belt, many samples of granite, granodiorite, diorite, and al...The North Dabie complex unit （NDC） is a widely exposed petro-tectonic unit. To understand post-orogenic uplift history and mechanism of the Dabie orogenic belt, many samples of granite, granodiorite, diorite, and alkali feldspar granite with precise zircon U-Pb ages were collected for electron microprobe analysis of hornblende. Emplacement pressure values were then cal- culated by using an Al-in-hornblende geobarometer. The result shows that total A1 （A1T） values in hornblende range from 1.17 to 1.97 p.f.u., XFe（=Fe/（Fe＋Mg）） from 0.4 to 0.65, and corresponding pressure values from 256.8 to 676.2 MPa for A1T greater than 1.17. It is suggested that although the main mechanism for the uplift is tectonic extension, inhomogeneous uplift related to the pluton emplacement is also important during post-orogenic evolution of the Dabie orogenic belt. Emplacement depth dis- tribution of the plutons shows that uplift in the NDC is affected by horst-graben structures since 120 Ma.展开更多
Major and accessory minerals from the Ibity granite, Tsarasaotra monzonitic and granite dykes, and Antsahakely granite of the Itremo domain in the Precambrian basement of Madagascar were characterized by using microsc...Major and accessory minerals from the Ibity granite, Tsarasaotra monzonitic and granite dykes, and Antsahakely granite of the Itremo domain in the Precambrian basement of Madagascar were characterized by using microscopic observations and chemical analyses with the aim of understanding their chemical characteristics and estimating the crystallization pressure and oxygen fugacity of their host rocks. Plagioclases in these rocks are albite and oligoclase, while alkali feldspars are orthoclase. For the phlogopite-micas, Fe-biotite and Li-phengite are common for the Ibity and Antsahakely granites, Mg-biotite is common for the Ibity granite and the Tsarasaotra monzonitic and granite dykes, and siderophyllite and Zinnwaldite are specific to the Ibity granite. Phlogopite-micas in the studied rocks are mainly primary, accessorily re-equilibrated, and rarely secondary. Calcic amphiboles distributed in the Magnesio-and Ferro-hornblende are identified in the Tsarasaotra monzonitic, whereas amphibole is rare and absent in the other rocks. Igneous titanite is observed in the Ibity granite and in the Tsarasaotra monzonitic rocks, which have similar compositions to some REE oxide-rich titanites. Concerning the Fe-Ti oxide phases, the rhombohedral and spinel/trifer tetroxide phases are found in both the Tsarasaotra monzonitic and the Tsarasaotra granite dyke, the trifer tetroxide and spinel + wüstite phases are found only in the Ibity granite, and the pseudobrookite + rhombohedral phase is found only in the Tsarasaotra granite dyke. The epidote mineral, rarely found in the Antsahakely granite, could be an indicator of metamorphism or hydrothermal activity involved during the emplacement of this rock. Aluminum in hornblende geobarometer gave pressure ranges of around 5 kbar for the Tsarasaotra monzonitic rocks. The Titanite geobarometer gave pressures of 2.5 - 3.2 kbar for the Ibity granite, 2.9 kbar for the Tsarasaotra monzonitic, and 7.1 kbar for the Antsahakely granite. Both amphibole and Fe-Ti oxide-base oxygen fugacity reve展开更多
Longling is characterized by a wide distribution of hydrothermal areas, among which the Banglazhang hydrothermal system is the most geothermally active. Banglazhang is marked by intensive hydrothermal activities inclu...Longling is characterized by a wide distribution of hydrothermal areas, among which the Banglazhang hydrothermal system is the most geothermally active. Banglazhang is marked by intensive hydrothermal activities including hot springs, geysers, fumaroles and hydrothermal explosions. The geothermal waters from the Longling region are mainly HCO3-Na type with low but comparable SO4 and Cl concentrations. Calculations based on a variety of chemical geothermometers and a K-Ca geobarometer indicate that the Banglazhang hydrothermal system has much higher subsurface temperature and CO2 pressure compared to the other systems such as Daheba, Dazhulin and Huangcaoba. However, geothermal water samples collected from all these alternative hydrothermal areas are either partially equilibrated with reservoir minerals or are immature. The silica-enthalpy relationships of Banglazhang geothermal waters indicate the presence of a deep geothermal fluid with an enthalpy value and silica concentration of 945 J/g（up to around 220 °C） and 339 mg/L. Our work indicates the Banglazhang area is a promising source in terms of long-term utilization of hydrothermal resources.展开更多
Volcanic rocks in seamounts of the South China Sea consist mainly of alkali basalt, tholeiitic basalt, trachyandesitic pumice, dacite, etc. Inclusions in the minerals of the volcanic rocks are main-ly amorphous melt i...Volcanic rocks in seamounts of the South China Sea consist mainly of alkali basalt, tholeiitic basalt, trachyandesitic pumice, dacite, etc. Inclusions in the minerals of the volcanic rocks are main-ly amorphous melt inclusions, Which reflects that the volcanic rocks are characterized by submarine eruption and rapid cooling on the seafloor. Furthermore, fluid-melt inclusions have been discovered for the first time in alkali basalts and mantle-derived xenoliths, indicating a process of differentiation between magma and fluid in the course of mantle partial melting. Alkali basalts and inclusions may have been formed in this nonhomogeneous system.Rock-forming temperatures of four seamounts were estimated as follows: the Zhongnan seamount alkali basalt 1155 ～1185 ℃, the Xianbei seamount alkali basalt 960～1200℃, tholeiitic basalt 1040～1230℃, the Daimao seamount tholeiitic basalt 1245 ～1280℃; and the Jianfeng seamount trachyandestic pumice 880～1140℃. Equilibrium pressures of alkali basalts in the Zhongnan and Xanbei seamounts are 13.57 and 8.8 × 108 Pa, respectively. Pyroxene equilibrium tem-peratures of mantle xenoliths from the Xianbei seamount were estimated at 1073～1121℃, and pres-sures at (15.58 ～ 22.47)× 108Pa, suggesting a deep-source (e.g. the asthenosphere) for the alkali basalts.展开更多
对于大别山高压-超高压变质带中大面积出露的云母片岩和片麻岩的变质条件和演化历史有不同的认识:如中低压绿帘角闪岩相,高压角闪岩相和超高压榴辉岩相。通过对大别山南部超高压榴辉岩区、高压榴辉岩区和宿松变质杂岩带中的云母片岩和...对于大别山高压-超高压变质带中大面积出露的云母片岩和片麻岩的变质条件和演化历史有不同的认识:如中低压绿帘角闪岩相,高压角闪岩相和超高压榴辉岩相。通过对大别山南部超高压榴辉岩区、高压榴辉岩区和宿松变质杂岩带中的云母片岩和片麻岩进行详细的岩相学及相平衡研究表明:它们的变质条件分别为610℃～690℃,1.2～1.4Ga;590～600℃、1.3～1.5GPa;520～590℃,0.9～1.4GPa,相当于高压绿帘角闪岩相、高压角闪岩相与榴辉岩相之间的过渡。依据超高压榴辉岩区绿帘石黑云片麻岩中的石榴石环带特征推测,它们很可能经过超高压变质阶段,现有矿物组合记录了抬升阶段的条件。但是高压榴辉岩区的石榴石绿帘石二云片麻岩和宿松变质杂岩带中石榴石云母片岩中的石榴石环带特征表明,其现有矿物组合记录了变质峰期条件,不应该经历更高压变质阶段。在 KFMASH 体系的 PT 视剖面图上计算多硅白云母 Si 含量等值线表明,在多数矿物组合中白云母的 Si 含量可作为地质压力计,但 Si 等值线的斜率受到矿物组合的控制。展开更多
文摘Isotope dating, hornblende geobarometer, fission-track analysis and fluid inclusion homogeneous temperature analysis have been applied to Caledonian, Variscan and Yenshan plutons in Bei Huaiyang (BHY) and Dabie erogenic belt (DOB), and the emplaced depths and ages of these plutons have been obtained in order to obtain differential uplift time and uplift heights between BHY and DOB since late Paleozoic era. BHY had experienced three stages of uplift (C1-C2, T-J2, J3-K1) and its total uplift height is about 10 km, but, DOB had only experienced two stages of uplift (T-J2, J3-K1) and its maximum uplift height is more than 15 km. BHY uplift occurred mainly before the mid-Jurassic (about 150 Ma), but DOB uplift took place after the mid-Jurassic (about 150 Ma).
基金supported by the Anhui Natural Science Foundation (Grant No. 1108085J12)China Geological Survey Project of Science and Technology (Grant No. 1212011121114)
文摘The North Dabie complex unit （NDC） is a widely exposed petro-tectonic unit. To understand post-orogenic uplift history and mechanism of the Dabie orogenic belt, many samples of granite, granodiorite, diorite, and alkali feldspar granite with precise zircon U-Pb ages were collected for electron microprobe analysis of hornblende. Emplacement pressure values were then cal- culated by using an Al-in-hornblende geobarometer. The result shows that total A1 （A1T） values in hornblende range from 1.17 to 1.97 p.f.u., XFe（=Fe/（Fe＋Mg）） from 0.4 to 0.65, and corresponding pressure values from 256.8 to 676.2 MPa for A1T greater than 1.17. It is suggested that although the main mechanism for the uplift is tectonic extension, inhomogeneous uplift related to the pluton emplacement is also important during post-orogenic evolution of the Dabie orogenic belt. Emplacement depth dis- tribution of the plutons shows that uplift in the NDC is affected by horst-graben structures since 120 Ma.
文摘Major and accessory minerals from the Ibity granite, Tsarasaotra monzonitic and granite dykes, and Antsahakely granite of the Itremo domain in the Precambrian basement of Madagascar were characterized by using microscopic observations and chemical analyses with the aim of understanding their chemical characteristics and estimating the crystallization pressure and oxygen fugacity of their host rocks. Plagioclases in these rocks are albite and oligoclase, while alkali feldspars are orthoclase. For the phlogopite-micas, Fe-biotite and Li-phengite are common for the Ibity and Antsahakely granites, Mg-biotite is common for the Ibity granite and the Tsarasaotra monzonitic and granite dykes, and siderophyllite and Zinnwaldite are specific to the Ibity granite. Phlogopite-micas in the studied rocks are mainly primary, accessorily re-equilibrated, and rarely secondary. Calcic amphiboles distributed in the Magnesio-and Ferro-hornblende are identified in the Tsarasaotra monzonitic, whereas amphibole is rare and absent in the other rocks. Igneous titanite is observed in the Ibity granite and in the Tsarasaotra monzonitic rocks, which have similar compositions to some REE oxide-rich titanites. Concerning the Fe-Ti oxide phases, the rhombohedral and spinel/trifer tetroxide phases are found in both the Tsarasaotra monzonitic and the Tsarasaotra granite dyke, the trifer tetroxide and spinel + wüstite phases are found only in the Ibity granite, and the pseudobrookite + rhombohedral phase is found only in the Tsarasaotra granite dyke. The epidote mineral, rarely found in the Antsahakely granite, could be an indicator of metamorphism or hydrothermal activity involved during the emplacement of this rock. Aluminum in hornblende geobarometer gave pressure ranges of around 5 kbar for the Tsarasaotra monzonitic rocks. The Titanite geobarometer gave pressures of 2.5 - 3.2 kbar for the Ibity granite, 2.9 kbar for the Tsarasaotra monzonitic, and 7.1 kbar for the Antsahakely granite. Both amphibole and Fe-Ti oxide-base oxygen fugacity reve
基金financially supported by the National Natural Science Foundation of China (No. 41120124003, 41572335 and 41521001)the research program of China Power Investment Corporation (2015-138-HHS-KJ-X)the research program of State Key Laboratory of Biogeology and Environmental Geology of China
文摘Longling is characterized by a wide distribution of hydrothermal areas, among which the Banglazhang hydrothermal system is the most geothermally active. Banglazhang is marked by intensive hydrothermal activities including hot springs, geysers, fumaroles and hydrothermal explosions. The geothermal waters from the Longling region are mainly HCO3-Na type with low but comparable SO4 and Cl concentrations. Calculations based on a variety of chemical geothermometers and a K-Ca geobarometer indicate that the Banglazhang hydrothermal system has much higher subsurface temperature and CO2 pressure compared to the other systems such as Daheba, Dazhulin and Huangcaoba. However, geothermal water samples collected from all these alternative hydrothermal areas are either partially equilibrated with reservoir minerals or are immature. The silica-enthalpy relationships of Banglazhang geothermal waters indicate the presence of a deep geothermal fluid with an enthalpy value and silica concentration of 945 J/g（up to around 220 °C） and 339 mg/L. Our work indicates the Banglazhang area is a promising source in terms of long-term utilization of hydrothermal resources.
文摘Volcanic rocks in seamounts of the South China Sea consist mainly of alkali basalt, tholeiitic basalt, trachyandesitic pumice, dacite, etc. Inclusions in the minerals of the volcanic rocks are main-ly amorphous melt inclusions, Which reflects that the volcanic rocks are characterized by submarine eruption and rapid cooling on the seafloor. Furthermore, fluid-melt inclusions have been discovered for the first time in alkali basalts and mantle-derived xenoliths, indicating a process of differentiation between magma and fluid in the course of mantle partial melting. Alkali basalts and inclusions may have been formed in this nonhomogeneous system.Rock-forming temperatures of four seamounts were estimated as follows: the Zhongnan seamount alkali basalt 1155 ～1185 ℃, the Xianbei seamount alkali basalt 960～1200℃, tholeiitic basalt 1040～1230℃, the Daimao seamount tholeiitic basalt 1245 ～1280℃; and the Jianfeng seamount trachyandestic pumice 880～1140℃. Equilibrium pressures of alkali basalts in the Zhongnan and Xanbei seamounts are 13.57 and 8.8 × 108 Pa, respectively. Pyroxene equilibrium tem-peratures of mantle xenoliths from the Xianbei seamount were estimated at 1073～1121℃, and pres-sures at (15.58 ～ 22.47)× 108Pa, suggesting a deep-source (e.g. the asthenosphere) for the alkali basalts.
文摘对于大别山高压-超高压变质带中大面积出露的云母片岩和片麻岩的变质条件和演化历史有不同的认识:如中低压绿帘角闪岩相,高压角闪岩相和超高压榴辉岩相。通过对大别山南部超高压榴辉岩区、高压榴辉岩区和宿松变质杂岩带中的云母片岩和片麻岩进行详细的岩相学及相平衡研究表明:它们的变质条件分别为610℃～690℃,1.2～1.4Ga;590～600℃、1.3～1.5GPa;520～590℃,0.9～1.4GPa,相当于高压绿帘角闪岩相、高压角闪岩相与榴辉岩相之间的过渡。依据超高压榴辉岩区绿帘石黑云片麻岩中的石榴石环带特征推测,它们很可能经过超高压变质阶段,现有矿物组合记录了抬升阶段的条件。但是高压榴辉岩区的石榴石绿帘石二云片麻岩和宿松变质杂岩带中石榴石云母片岩中的石榴石环带特征表明,其现有矿物组合记录了变质峰期条件,不应该经历更高压变质阶段。在 KFMASH 体系的 PT 视剖面图上计算多硅白云母 Si 含量等值线表明,在多数矿物组合中白云母的 Si 含量可作为地质压力计,但 Si 等值线的斜率受到矿物组合的控制。
