Tho Gudui geothermal field records the highest temperature at equivalent borehole depths among the lainland hydrothermal systems in China's Mainland.Located about 150 km southeast of Lhasa City,the capital of Tibe...Tho Gudui geothermal field records the highest temperature at equivalent borehole depths among the lainland hydrothermal systems in China's Mainland.Located about 150 km southeast of Lhasa City,the capital of Tibet,the Gudui geothermal field belongs to the Sangri-Cuona rift belt,also known as the Sangri-Cuona geothermal belt,and is representative of the non-volcanic geothermal systems in the Himalayas.In this study,oxygen-18 and deuterium isotope compositions as well as 87Sr/86Sr ratios of water samples collected from the Gudui geothermal field were characterized to understand the origin and mixing processes of the geothermal fluids at Gudui.Hydrogen and oxygen isotope plots show both,deep and shallow reservoirs in the Gudui geothermal field.Deep geothermal fluids are the mixing product of magmatic and infiltrating snow-melt water.Calculations show that the magma fluid component of the deep geothermal fluids account for about 21.10%-24.04%;magma fluids lay also be a contributing source of lithium.The linear relationship of the 87Sr/86Sr isotopic ratio versus the 1/Sr plot indicates that shallow geothermal fluids form from the mixing of deep geothermal fluids with cold groundwater.Using a binary mixing model with deep geothermal fluid and cold groundwater as two end-members,the nixing ratios of the latter in most surface hot springs samples were calculated to be between 5% and 10%.Combined with basic geological characteristics,hydrogen and oxygen isotope characteristics,strontium concentration,87Sr/(86)Sr ratios,and the binary mixing model,we infer the 6 th-Class Reservoirs Evolution Conceptual Model(6-CRECM) for the Gudui geothermal system.This model represents an idealized summary of the characteristics of the Gudui geothermal field based on our comprehensive understanding of the origin and mixing processes of the geothermal fluid in Gudui.This study may aid in identifying the geothermal and geochemical origin of the Gudui high-temperature hydrothermal systems in remote Tibet of China,whose potential for geothermal development and utilization is enormous and untapped.展开更多
To analyze the genesis of Sr isotopes in groundwater of Hebei plain, time-accumulative effect of ^87Sr/^86Sr ratio was studied. It is shown that ^87Sr/^86Sr ratio increases with the increasing age and depth of groundw...To analyze the genesis of Sr isotopes in groundwater of Hebei plain, time-accumulative effect of ^87Sr/^86Sr ratio was studied. It is shown that ^87Sr/^86Sr ratio increases with the increasing age and depth of groundwater and has a positive correlation to 4Heexc and a negative correlation to δ^18O and δD.The groundwater is divided into three groups to discuss the relation between ^87Sr/^86Sr ratio and Sr^2＋ content： ① moderate Sr^2＋ content and higher ^87Sr/^86Sr ratio （water Ⅰ）; ② lower Sr^2＋ content and higher ^87Sr/^86Sr ratio （water Ⅱ）; and ③ higher Sr^2＋ content and lower ^87Sr/^86Sr ratio （water Ⅲ）, that is hot water. On the basis of integrated analysis, it was considered that ① the radiogenic Sr in the Quaternary groundwater （Q4-Q1） originates from weathering of silicate rich in Na and Rb, mainly from plagioclase; ② the radiogenic Sr of hot water in Huanghua port is attributed to carbonate dissolution, with lower ^87Sr/^86Sr ratio and higher Sr/Na ratio; ③ the recharge area is laterally recharged by the groundwater flowing through igneous and metamorphic rocks, with moderate ^87Sr/^86Sr ratio. However, the formation mechanism of Sr isotopes in Tertiary groundwater needs further studies.展开更多
To evaluate influence of chemical weathering of the Qinghai-Tibet Plateau (QTP) on seawater 87Sr/86Sr variation, river water and sediment samples were collected, and their Sr concentrations and isotopic compositions a...To evaluate influence of chemical weathering of the Qinghai-Tibet Plateau (QTP) on seawater 87Sr/86Sr variation, river water and sediment samples were collected, and their Sr concentrations and isotopic compositions analyzed, from the seven large rivers that originated from the QTP. By combining these with the data of the Ganges, Brahmaputra, Indus and Irrawaddy originated in the southern QTP, the total Sr flux of the eleven rivers reaches 3.47×109 mol·a-1, which accounts for 10.2% of the total Sr flux transported by the global rivers. The weighted mean 87Sr/86Sr is 0.71694, higher than the average value of the global rivers. The 87Srex (87Sr flux in excess of the seawater 87Sr/86Sr ratio) of the Chinese seven rivers is 1.55×106 mol·a-1, only accounting for about 6% of the value of the eleven rivers originated from QTP, and the Ganges-Brahmaputra system accounts for 86%. We assume that the QTP rivers have no strontium contributions to the oceans before ~40 Ma and the Sr fluxes of the global rivers, except the QTP eleven rivers, are constant, then a maximum linear increase in Sr fluxes of the QTP rivers from zero to the modern value in response to tectonic uplift can explain ~69% increase of seawater 87Sr/86Sr over the past ~40 Ma and the remainder of 31% is perhaps provided from other factors.展开更多
A new method for high-precision measurements of stable (δ88/86Sr) and radiogenic (87Sr/86Sr) Sr isotope ratios was developed on the MC-ICP-MS using a standard-sample-standard bracketing protocol. By carefully monitor...A new method for high-precision measurements of stable (δ88/86Sr) and radiogenic (87Sr/86Sr) Sr isotope ratios was developed on the MC-ICP-MS using a standard-sample-standard bracketing protocol. By carefully monitoring and controlling the accumulation of the on-peak backgrounds (i.e. the carryover memory) on the instrument, our method can provide an external precision of around 0.010‰ to 0.014‰ for 88/86 Sr measurements. Such precision is comparable to that achieved by double-spike TIMS method (DS-TIMS), and 2-3 times better than those of the previously reported results by MC-ICP-MS without spiking. The results of the standard seawater IAPSO are also identical to those by DS-TIMS. However, our method is more advantageous, efficient and convenient to use for routine Sr isotopic analysis than the DS-TIMS method as there is no need to prepare and calibrate the 84Sr-87 Sr double spike. Using this method, we measured the δ88/86Sr values in a series of international geological rock standards, which show large variability, with the lowest value (0.20‰) registered in JG-2, a terrestrial granite, and the highest value (0.539‰) in UB-N, a serpentinite. This may provide an additional means for isotopic characterization of geological processes, adding a new dimension over the traditional use of radiogenic Sr isotopic ratio 87Sr/86Sr.展开更多
The Sr isotopic composition of foraminifera has been used in studies of chronstratigraphy and sedi- mentary geochemistry. However, it is difficult to sample foraminifera without overprinting of later diagenesis, which...The Sr isotopic composition of foraminifera has been used in studies of chronstratigraphy and sedi- mentary geochemistry. However, it is difficult to sample foraminifera without overprinting of later diagenesis, which contains enough amount of Sr for isotopic measurement. Analysis of single-grain foraminifera was successively conducted by a combination of low Sr procedural blank and high precision determination of 87Sr/86Sr ratio. This combi- nation of single-grain foraminifera can be significant for the study and application of Sr isotopic composition of fo- raminifera. Measured foraminifera of this study, having a size between 250 μm and 400 μm, were sampled from the carbonate basement of a ferromanganese crust in western Pacific. Mean value of 87Sr/86Sr ratios of the analyzed sin- gle-grain foraminifera is 0.709150 ±0.000013 with internal precision between 4 ppm and 8 ppm for each measurement run. Average value of total procedural blank of Sr is 14 pg. It is significant but difficult to date foraminifera in carbonate basements of ferromanganese crusts. Based on the ob- tained value of 87Sr/86Sr ratio, the analyzed foraminifera can be dated at 0.91 +0.33/?0.39 Ma.展开更多
基金This work was financially supported by the China Geological Survey(Grant No.DD20160054)the National Natural Science Foundation of China(Grant No.U1407207)the National Key Research and Development Program of China(Grant No.2017YFC0602802).
文摘Tho Gudui geothermal field records the highest temperature at equivalent borehole depths among the lainland hydrothermal systems in China's Mainland.Located about 150 km southeast of Lhasa City,the capital of Tibet,the Gudui geothermal field belongs to the Sangri-Cuona rift belt,also known as the Sangri-Cuona geothermal belt,and is representative of the non-volcanic geothermal systems in the Himalayas.In this study,oxygen-18 and deuterium isotope compositions as well as 87Sr/86Sr ratios of water samples collected from the Gudui geothermal field were characterized to understand the origin and mixing processes of the geothermal fluids at Gudui.Hydrogen and oxygen isotope plots show both,deep and shallow reservoirs in the Gudui geothermal field.Deep geothermal fluids are the mixing product of magmatic and infiltrating snow-melt water.Calculations show that the magma fluid component of the deep geothermal fluids account for about 21.10%-24.04%;magma fluids lay also be a contributing source of lithium.The linear relationship of the 87Sr/86Sr isotopic ratio versus the 1/Sr plot indicates that shallow geothermal fluids form from the mixing of deep geothermal fluids with cold groundwater.Using a binary mixing model with deep geothermal fluid and cold groundwater as two end-members,the nixing ratios of the latter in most surface hot springs samples were calculated to be between 5% and 10%.Combined with basic geological characteristics,hydrogen and oxygen isotope characteristics,strontium concentration,87Sr/(86)Sr ratios,and the binary mixing model,we infer the 6 th-Class Reservoirs Evolution Conceptual Model(6-CRECM) for the Gudui geothermal system.This model represents an idealized summary of the characteristics of the Gudui geothermal field based on our comprehensive understanding of the origin and mixing processes of the geothermal fluid in Gudui.This study may aid in identifying the geothermal and geochemical origin of the Gudui high-temperature hydrothermal systems in remote Tibet of China,whose potential for geothermal development and utilization is enormous and untapped.
基金This paper is supported by China Geological Survey Project (No. 200320150002).
文摘To analyze the genesis of Sr isotopes in groundwater of Hebei plain, time-accumulative effect of ^87Sr/^86Sr ratio was studied. It is shown that ^87Sr/^86Sr ratio increases with the increasing age and depth of groundwater and has a positive correlation to 4Heexc and a negative correlation to δ^18O and δD.The groundwater is divided into three groups to discuss the relation between ^87Sr/^86Sr ratio and Sr^2＋ content： ① moderate Sr^2＋ content and higher ^87Sr/^86Sr ratio （water Ⅰ）; ② lower Sr^2＋ content and higher ^87Sr/^86Sr ratio （water Ⅱ）; and ③ higher Sr^2＋ content and lower ^87Sr/^86Sr ratio （water Ⅲ）, that is hot water. On the basis of integrated analysis, it was considered that ① the radiogenic Sr in the Quaternary groundwater （Q4-Q1） originates from weathering of silicate rich in Na and Rb, mainly from plagioclase; ② the radiogenic Sr of hot water in Huanghua port is attributed to carbonate dissolution, with lower ^87Sr/^86Sr ratio and higher Sr/Na ratio; ③ the recharge area is laterally recharged by the groundwater flowing through igneous and metamorphic rocks, with moderate ^87Sr/^86Sr ratio. However, the formation mechanism of Sr isotopes in Tertiary groundwater needs further studies.
基金Supported by National Natural Science Foundation of China (Grant Nos. 40473009, 40331001, 40873001)
文摘To evaluate influence of chemical weathering of the Qinghai-Tibet Plateau (QTP) on seawater 87Sr/86Sr variation, river water and sediment samples were collected, and their Sr concentrations and isotopic compositions analyzed, from the seven large rivers that originated from the QTP. By combining these with the data of the Ganges, Brahmaputra, Indus and Irrawaddy originated in the southern QTP, the total Sr flux of the eleven rivers reaches 3.47×109 mol·a-1, which accounts for 10.2% of the total Sr flux transported by the global rivers. The weighted mean 87Sr/86Sr is 0.71694, higher than the average value of the global rivers. The 87Srex (87Sr flux in excess of the seawater 87Sr/86Sr ratio) of the Chinese seven rivers is 1.55×106 mol·a-1, only accounting for about 6% of the value of the eleven rivers originated from QTP, and the Ganges-Brahmaputra system accounts for 86%. We assume that the QTP rivers have no strontium contributions to the oceans before ~40 Ma and the Sr fluxes of the global rivers, except the QTP eleven rivers, are constant, then a maximum linear increase in Sr fluxes of the QTP rivers from zero to the modern value in response to tectonic uplift can explain ~69% increase of seawater 87Sr/86Sr over the past ~40 Ma and the remainder of 31% is perhaps provided from other factors.
基金supported by the Chinese Ministry of Science and Technology Special Scheme (2009CB421206 and 2010CB808900)the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-YW-138)+1 种基金the National Natural Science Foundation of China (40973008 and 41173006)contribution No.IS-1616 from GIGCAS
文摘A new method for high-precision measurements of stable (δ88/86Sr) and radiogenic (87Sr/86Sr) Sr isotope ratios was developed on the MC-ICP-MS using a standard-sample-standard bracketing protocol. By carefully monitoring and controlling the accumulation of the on-peak backgrounds (i.e. the carryover memory) on the instrument, our method can provide an external precision of around 0.010‰ to 0.014‰ for 88/86 Sr measurements. Such precision is comparable to that achieved by double-spike TIMS method (DS-TIMS), and 2-3 times better than those of the previously reported results by MC-ICP-MS without spiking. The results of the standard seawater IAPSO are also identical to those by DS-TIMS. However, our method is more advantageous, efficient and convenient to use for routine Sr isotopic analysis than the DS-TIMS method as there is no need to prepare and calibrate the 84Sr-87 Sr double spike. Using this method, we measured the δ88/86Sr values in a series of international geological rock standards, which show large variability, with the lowest value (0.20‰) registered in JG-2, a terrestrial granite, and the highest value (0.539‰) in UB-N, a serpentinite. This may provide an additional means for isotopic characterization of geological processes, adding a new dimension over the traditional use of radiogenic Sr isotopic ratio 87Sr/86Sr.
基金This study was supported by the Chinese Society for 0ceanology （CS0） （Grant Nos. DY105-01-04-14 and DY105-01-01-01）the National Natural Science Foundation of China （Grant No. 40403008）.
文摘The Sr isotopic composition of foraminifera has been used in studies of chronstratigraphy and sedi- mentary geochemistry. However, it is difficult to sample foraminifera without overprinting of later diagenesis, which contains enough amount of Sr for isotopic measurement. Analysis of single-grain foraminifera was successively conducted by a combination of low Sr procedural blank and high precision determination of 87Sr/86Sr ratio. This combi- nation of single-grain foraminifera can be significant for the study and application of Sr isotopic composition of fo- raminifera. Measured foraminifera of this study, having a size between 250 μm and 400 μm, were sampled from the carbonate basement of a ferromanganese crust in western Pacific. Mean value of 87Sr/86Sr ratios of the analyzed sin- gle-grain foraminifera is 0.709150 ±0.000013 with internal precision between 4 ppm and 8 ppm for each measurement run. Average value of total procedural blank of Sr is 14 pg. It is significant but difficult to date foraminifera in carbonate basements of ferromanganese crusts. Based on the ob- tained value of 87Sr/86Sr ratio, the analyzed foraminifera can be dated at 0.91 +0.33/?0.39 Ma.
