Since 2006,we have conducted a geological exploration of the Khammuane area in southeastern Laos.Several thick sequences of potash deposits containing sylvite and carnallite were discovered from drilling Paleocene str...Since 2006,we have conducted a geological exploration of the Khammuane area in southeastern Laos.Several thick sequences of potash deposits containing sylvite and carnallite were discovered from drilling Paleocene strata of the Thangon Formation(E1tg).To constrain the origin of the brine that formed thick sequences of salt mineral deposits,we measured the strontium and boron isotope composition of some salt minerals in the potash deposit.Boron isotope composition of halite-and potash-associated minerals in the Khammuane potash deposit varied from 19.91%to 31.01‰,which differs significantly from continental evaporates(-6.83‰--5.79‰)but is very close to that of salts precipitated from evapo-concentrated seawater(10‰-36‰).The 87Sr/86Sr ratios(0.707542 to 0.709461)of salts were also close to the values of Paleocene seawater(0.70772 to 0.707830).The content of Br-(0.01%-0.25%)and Br×103/Cl ratios(0.10-0.52)of halite were>10 times higher than that of common continental salts.These characteristics indicate clearly that the Laos potash deposits were deposited from seawater.The small variation in boron and strontium isotopes in all salt sedimentary sequences(gypsum-halite-potash-halite)also suggests that the recharge source should be stable and the effects of other continental water mixing are negligible.Large-scale potash deposits are commonly precipitated from seawater.Hence,the results of recent regional drilling work and geochemical research suggest extensive potash resources could occur in the Thangon Formation of southeastern Laos.展开更多
There are two main methods to determine boron isotopic composition.One is the solution method,in which boron is purified after the samples are dissolved in solution and the boron isotope ratios are determined by therm...There are two main methods to determine boron isotopic composition.One is the solution method,in which boron is purified after the samples are dissolved in solution and the boron isotope ratios are determined by thermal ionization mass spectrometry(P-TIMS and N-TIMS) or multicollector inductively coupled plasma mass spectrometry(MC-ICP-MS).The other is an in-situ analysis method,in which the in-situ boron isotopic ratios in minerals are analyzed directly using secondary ion mass spectrometry(SIMS) or laser ablation multicollector inductively coupled plasma mass spectrometry(LA-MC-ICP-MS).In the in-situ analysis method for boron isotopes,the multifarious chemical purification and separation processes of the solution method are avoided,with increased work efficiency.In addition,the microzones and microbeddings of minerals can be analyzed in-situ to reveal the fine processes and conditions of mineral formation.In this study,using the standard-sample-bracketing(SSB) method,mass bias of the instrument and the fractionation of isotopes were calibrated,and the in-situ determination method of LA-MC-ICP-MS for boron isotopes was established.Through detailed analyses on a series of boron isotope standards and samples,a matrix effect was assessed but not detected,and the analysis results were in accordance with the formerly reported values or P-TIMS determined values,within the error range.The analytical results for IAEA B4 and IMR RB1 with relatively high boron contents were δ 11B =-(8.36±0.58)‰(2σ,n=50) and δ 11B =-(12.96±0.97)‰(2σ,n=57),respectively;the analytical result for IAEA B6 with rela-tively low boron content was δ 11B =-(3.29±1.12)‰(2σ,n=35).In-situ measurements for B isotopes were performed on geo-logical samples such as tourmaline,ulexite,ludwigite,inyoite and ascharite,with the results consistent with those determined by P-TIMS,within the error range.展开更多
Lithium in nature mainly exists in the forms of solid minerals and ionic liquid.More than 150 lithium minerals exist,which are mainly pegmatite mineral including triphane,lithionite and petalite.Liquid lithium mainly
A laboratory experiment was undertaken to investigate the behaviour of boron at the seawater-air interface under air flow conditions. Dried air at 25 and 35℃ was passed over or bubbled through seawater at the same te...A laboratory experiment was undertaken to investigate the behaviour of boron at the seawater-air interface under air flow conditions. Dried air at 25 and 35℃ was passed over or bubbled through seawater at the same temperature. A combination of ice-chilled condensers and KOH impregnated cellulose fibre filters was used to collect boron from the reacted air. When air stripped of boron was passed over the seawater, boron was found in the reacted air, and its concentration was higher in the higher temperature test. In the tests where air was bubbled through seawater the concentration of boron in the reacted air was directly proportional to the air flow rate. In this situation the boron in the reacted air was mainly introduced as a spray of microdroplets. Isotopic analysis of the collected boron in the non-bubbled tests yields fractionation factors which demonstrate that the lighter isotope, 10B, is enriched in the reacted air. The size of the fractionation changes with temperature, ruling out a purely kinetic effect.展开更多
基金supported by the National Natural Science Foundation of China(40603007 and 40903024)
文摘Since 2006,we have conducted a geological exploration of the Khammuane area in southeastern Laos.Several thick sequences of potash deposits containing sylvite and carnallite were discovered from drilling Paleocene strata of the Thangon Formation(E1tg).To constrain the origin of the brine that formed thick sequences of salt mineral deposits,we measured the strontium and boron isotope composition of some salt minerals in the potash deposit.Boron isotope composition of halite-and potash-associated minerals in the Khammuane potash deposit varied from 19.91%to 31.01‰,which differs significantly from continental evaporates(-6.83‰--5.79‰)but is very close to that of salts precipitated from evapo-concentrated seawater(10‰-36‰).The 87Sr/86Sr ratios(0.707542 to 0.709461)of salts were also close to the values of Paleocene seawater(0.70772 to 0.707830).The content of Br-(0.01%-0.25%)and Br×103/Cl ratios(0.10-0.52)of halite were>10 times higher than that of common continental salts.These characteristics indicate clearly that the Laos potash deposits were deposited from seawater.The small variation in boron and strontium isotopes in all salt sedimentary sequences(gypsum-halite-potash-halite)also suggests that the recharge source should be stable and the effects of other continental water mixing are negligible.Large-scale potash deposits are commonly precipitated from seawater.Hence,the results of recent regional drilling work and geochemical research suggest extensive potash resources could occur in the Thangon Formation of southeastern Laos.
基金supported by the National Special Research Program for Non-Profit Trades (Sponsored by MLR, 200911043-20 and 200811114)
文摘There are two main methods to determine boron isotopic composition.One is the solution method,in which boron is purified after the samples are dissolved in solution and the boron isotope ratios are determined by thermal ionization mass spectrometry(P-TIMS and N-TIMS) or multicollector inductively coupled plasma mass spectrometry(MC-ICP-MS).The other is an in-situ analysis method,in which the in-situ boron isotopic ratios in minerals are analyzed directly using secondary ion mass spectrometry(SIMS) or laser ablation multicollector inductively coupled plasma mass spectrometry(LA-MC-ICP-MS).In the in-situ analysis method for boron isotopes,the multifarious chemical purification and separation processes of the solution method are avoided,with increased work efficiency.In addition,the microzones and microbeddings of minerals can be analyzed in-situ to reveal the fine processes and conditions of mineral formation.In this study,using the standard-sample-bracketing(SSB) method,mass bias of the instrument and the fractionation of isotopes were calibrated,and the in-situ determination method of LA-MC-ICP-MS for boron isotopes was established.Through detailed analyses on a series of boron isotope standards and samples,a matrix effect was assessed but not detected,and the analysis results were in accordance with the formerly reported values or P-TIMS determined values,within the error range.The analytical results for IAEA B4 and IMR RB1 with relatively high boron contents were δ 11B =-(8.36±0.58)‰(2σ,n=50) and δ 11B =-(12.96±0.97)‰(2σ,n=57),respectively;the analytical result for IAEA B6 with rela-tively low boron content was δ 11B =-(3.29±1.12)‰(2σ,n=35).In-situ measurements for B isotopes were performed on geo-logical samples such as tourmaline,ulexite,ludwigite,inyoite and ascharite,with the results consistent with those determined by P-TIMS,within the error range.
文摘Lithium in nature mainly exists in the forms of solid minerals and ionic liquid.More than 150 lithium minerals exist,which are mainly pegmatite mineral including triphane,lithionite and petalite.Liquid lithium mainly
基金The paper was considerably improved as a result of reviews by H. G. M. Eggenkamp and A.Spivack, for which the authors were very grateful. Y. M. Zhou (Institute of Salt Lakes, Xining, China) kindly assisted with the chlorine isotopic measurements. This
文摘A laboratory experiment was undertaken to investigate the behaviour of boron at the seawater-air interface under air flow conditions. Dried air at 25 and 35℃ was passed over or bubbled through seawater at the same temperature. A combination of ice-chilled condensers and KOH impregnated cellulose fibre filters was used to collect boron from the reacted air. When air stripped of boron was passed over the seawater, boron was found in the reacted air, and its concentration was higher in the higher temperature test. In the tests where air was bubbled through seawater the concentration of boron in the reacted air was directly proportional to the air flow rate. In this situation the boron in the reacted air was mainly introduced as a spray of microdroplets. Isotopic analysis of the collected boron in the non-bubbled tests yields fractionation factors which demonstrate that the lighter isotope, 10B, is enriched in the reacted air. The size of the fractionation changes with temperature, ruling out a purely kinetic effect.
