CN108548708B

CN108548708B - A kind of cold spring carbonate samples processing method for surveying year mode suitable for the U system tropic

Info

Publication number: CN108548708B
Application number: CN201810602666.2A
Authority: CN
Inventors: 王立胜; 马志邦; 王学锋
Original assignee: Institute of Geology and Geophysics of CAS
Current assignee: Institute of Geology and Geophysics of CAS
Priority date: 2018-06-12
Filing date: 2018-06-12
Publication date: 2019-04-16
Anticipated expiration: 2038-06-12
Also published as: CN108548708A

Abstract

The present invention relates to a kind of cold spring carbonate samples processing methods that year mode is surveyed suitable for the U system tropic, it the treating method comprises the split-phase processing and chemical purification processing to sample, split-phase processing is by the way that the powder sample of cold spring carbonate to be added in mixing heavy-fluid, by increasing the lesser heavy-fluid proportion of density in mixing heavy-fluid, it is gradually reduced the density for mixing heavy-fluid, by the density of different minerals in sample and the otherness of granularity, several subsamples successively are precipitated from mixing heavy-fluid.The present invention is suitable for carrying out physical separation to impure cold spring carbonate samples, and avoiding uranium thorium isotope, there is a phenomenon where be fractionated；The chemical purification processing method that further matching requirements optimizes simultaneously makes processed cold spring carbonate samples be suitable for the U system tropic and surveys year mode.The experiment proved that can get accurately and reliably using method of the invention²³⁰Th age data.

Description

A kind of cold spring carbonate samples processing method for surveying year mode suitable for the U system tropic

Technical field

The present invention relates to a kind of chemical treatment method of geological sample, especially a kind of U system tropic that is suitable for surveys year mode Cold spring carbonate samples processing method.

Background technique

The discovery of sea bed gas hydrate causes national governments and the great attention of scientist, cold spring and cold spring carbon One of the hot spot of Carbonate Rocks to become current geoscience research (Sun Zhilei etc., 2012；Sun et al.,2011；Sun et al.,2015；Sun et al.,2010).Since cold spring is the natural gas fluid of methane rich, a large amount of particulates are carried during spraying and spoiling over Substance is deposited on seabed in the form of chimney-like, bulk, crust shape etc., so, the pure calcium carbonate of cold spring carbonate is very low.Nearly 20 Nian Lai, domestic and foreign scholars obtain significant achievement to the research of the Biogeochemical mechanism in cold spring carbonate precipitation process, But it is formed the understanding of time it is very few (Cavagna et al., 1999；Teichert et al.,2003；Feng et al.,2010；Wirsig et al.,2012；Li et al.,2018).Therefore, it establishes and adapts to the SEEP CARBONATE PRECIPITATION KINETICS measurement age Technical method, facilitate the forming age for furtheing investigate SEEP CARBONATE PRECIPITATION KINETICS, and it carried out on split-second precision scale History is rebuild.

Currently, for Quaternary Period SEEP CARBONATE PRECIPITATION KINETICS determine year adapt to radioisotope method it is less, mainly include¹⁴C The uneven dating technology of dating methods and U system.Due to being may be subjected in SEEP CARBONATE PRECIPITATION KINETICS deposition process from methane or other The influence of derivative old carbon in source, application¹⁴C dating technology is often unable to get the accurate age.And when applying Uranium dating technology The original U and Th that must be carried to clast contained by sample are corrected, that is, a sample is taken using chemical solvent leaching Or the methods of physical sedimentation layering is divided into 5-7 subsample, by analyzing the U-Th isotope composition of each subsample, is returning Its age is determined on line.Classical tropic bearing calibration mainly has L/R (leachate/residue) method (Ku and Liang,1984；Herczeg and Chapman,1991；Ma Zhibang etc., 2010a), L/L (leachate/leachate) method (Schwarcz and Latham,1989；Peng et al., 2014) and the side TSD (Total-Sample Dissolution) Method (Luo and Ku, 1991；Ma Zhibang etc., 2010b).An important prerequisite of L/R technology is required with dilute in these methods Acid leaching takes, and U-Th isotope fractionation does not occur when sample.However, being often difficult to hold in actual operation, lead to existing method pair When cold spring carbonate uranium series isochrone determines year, it is difficult that each subsample uranium thorium isotope in chemical treating process is avoided to be fractionated The case where.

Summary of the invention

In order to obtain the accurate age of the impure cold spring carbonate in seabed, it is suitable for U system the object of the present invention is to provide one kind and returns Line is returned to survey the efficient quick of year mode, easily operated cold spring carbonate samples processing method, including to cold spring carbonate samples Phase-splitting technology and chemical purification technology, method of the invention can guarantee cold spring carbonate samples will not occur during processing The fractionation of uranium thorium isotope, achievees the purpose that reconstruction time scale.

In order to achieve the above object, the main technical schemes that the present invention uses are as follows:

A kind of cold spring carbonate samples processing method for surveying year mode suitable for the U system tropic, at the split-phase to sample Reason:

The powder sample of cold spring carbonate is added in mixing heavy-fluid, the mixing heavy-fluid includes the first heavy-fluid and the second weight Liquid, density of unlimited miscible and the second heavy-fluid density of both second heavy-fluid and the first heavy-fluid energy less than the first heavy-fluid；Pass through Being continuously increased second heavy-fluid proportion in the mixing heavy-fluid is gradually reduced the density of the mixing heavy-fluid, by The otherness of the density of different minerals and granularity in the powder sample successively isolates several cold spring carbon from mixing heavy-fluid The subsample of hydrochlorate.

The method also includes carrying out chemical purification processing to each subsample, the chemical purification processing includes:

Sample dissolution: the subsample is dissolved using inorganic solvent, then solvent evaporated；

Interior school U-Th: add into sample²²⁹Th-²³³U-²³⁶U diluent, standing 12~for 24 hours, then it is evaporated；

Chemical Decomposition: use inorganic acid solution sample, be added can raw rubber body metal ion, use ammonium hydroxide adjust solution ph To alkalescent, make the hydroxide colloid precipitating for obtaining the metal ion, the hydroxide colloid precipitating by sample U and Th is adsorbed, and is then separated and is cleaned the hydroxide colloid precipitating；

U-Th absorption and elution: precipitating using described in inorganic acid solution, be subsequently poured on the exchange column equipped with characteristic resin, Use 7~8mol/L HNO₃Fe ion and foreign ion are fallen in elution, U and Th complex ion is adsorbed by the characteristic resin；It is described Characteristic resin is AG1-X8 resin anion (R.A.), TEVA resin, UTEVA resin or TRU resin；Select solion to the exchange column It is eluted, respectively correspondingly to elute Th ion, U ion and be collected respectively.

A preferred embodiment according to the present invention, the first heavy-fluid that the split-phase processing uses are selected from diiodomethane, tetrabromo Ethane, bromoform, three Bromofluoromethanes, 1,1,2- tribromoethane, methylene bromide, bromo- 1, the 2- dichloroethanes of 1,2- bis-, 1,2- bis- Bromo- chloroethanes, Bromofume, combination one or more of in three chloro- bromomethanes；Second heavy-fluid is dehydrated alcohol, anhydrous Methanol, propyl alcohol, isopropanol, acetone, 2 pentanone, methyl iso-butyl ketone (MIBK), 2- butanone, hexamethylene, petroleum ether, ether, methyl- tert fourth One or more of combination in base ether, acetonitrile.

It should be noted that the first heavy-fluid and the second heavy-fluid in the application only define first and second from density up, Do not refer to type, therefore first and second may both respectively refer to for a kind of heavy-fluid when implementing, can also respectively refer to two kinds of generation or The combination of the close heavy-fluid of two kinds of density.Such as second heavy-fluid can be the mixing or anhydrous second of dehydrated alcohol and anhydrous methanol The mixing of alcohol and acetone.But in order to reduce the disturbing factor necessarily wanted, in split-phase processing, the type of heavy-fluid should be lacked as far as possible, And the density contrast of wherein the first heavy-fluid and the second heavy-fluid is larger, and the density of the first heavy-fluid should be slightly bigger than or be equal to cold spring carbonate The density maxima of sample Mineralss.

Wherein, the density (g/cm at 25 DEG C of room temperature³), diiodomethane 3.32, tetrabromoethane 2.97, bromoform 2.89, three Bromofluoromethanes, 2.75,1,1,2- tribromoethane 2.61, methylene bromide 2.48, bromo- 1, the 2- dichloroethanes of 1,2- bis- 2.36, the bromo- chloroethanes 2.25 of 1,2- bis-, Bromofume 2.17, three chloro- bromomethanes 2.00.Dehydrated alcohol 0.789, anhydrous methanol 0.791, propyl alcohol 0.803, isopropanol 0.7863, acetone 0.8,2 pentanone 0.81, methyl iso-butyl ketone (MIBK) 0.8,2- butanone 0.81, ring Hexane 0.78, petroleum ether 0.65, ether 0.7134, methyl tertiary butyl ether(MTBE) 0.74, acetonitrile 0.79.In selection, greater density The heavy-fluid of heavy-fluid and smaller density, which is arranged in pairs or groups, to be applied, but premise two pieces is that two kinds of heavy-fluids can be unlimited miscible and chemically react, In addition, the volatility of two kinds of pure heavy-fluid is as close as possible, the relative density values for otherwise mixing heavy-fluid can occur bright at any time Aobvious/biggish variation.

Preferably, first heavy-fluid is bromoform, and the second heavy-fluid is dehydrated alcohol.

A preferred embodiment according to the present invention further includes the pre-treatment step to sample before split-phase processing, pretreatment Step includes:

Sample clean: blocky SEEP CARBONATE PRECIPITATION KINETICS sample surfaces are rinsed using deionized water, are dried and in dry environment It is cooled to room temperature；

It drills through sample: in the clean surface of SEEP CARBONATE PRECIPITATION KINETICS sample, drilling through the cold spring carbonate that quality is about 0.5~1g Powder sample.

A preferred embodiment according to the present invention, the split-phase handle 5~7 cold spring carbonate subsample, use The cleaning of low-density alcohol, is then cooled to room temperature in dry environment.

A preferred embodiment according to the present invention, in the sample dissolving step of chemical purification processing, be by 0.02~ The subsample of 0.2g cold spring carbonate is placed in a beaker, and the dense HNO of 0.5~5ml high-purity is added to the beaker₃Or concentrated hydrochloric acid, Subsample described in aqua regia dissolution, is added the dense HF of 0.05~2ml high-purity, and closed beaker is protected under the conditions of being placed in 120~180 DEG C Temperature 1~2 day opens beaker, is evaporated sample under the conditions of 120~180 DEG C to complete molten sample.

In the step of preferred embodiment according to the present invention, the interior school U-Th of chemical purification processing, using 0.5~ The dense HNO of 5ml high-purity₃Appropriate (300 μ l) is added in sample dissolution²²⁹Th-²³³U-²³⁶U diluent standing 12~for 24 hours, it is added 0.05 ~2ml HClO₄Solution removes the organic matter in sample, is finally evaporated.

A preferred embodiment according to the present invention, in the Chemical Decomposition step of chemical purification processing, using 0.5~ Fe is added in the diluted hydrochloric acid dissolution sample of 1~2mol/L of 5ml³⁺, pH value of solution=7~8 are adjusted using ammonium hydroxide, are generated Fe (OH)₃Glue Body, U and Th in sample form complex compound under ammonium hydroxide effect and are adsorbed by the colloid, and the colloid is made to become larger reformation Precipitating, separates and cleans the precipitating.

A preferred embodiment according to the present invention, the U-Th absorption of the chemical purification processing are used in elution step The HNO of 7~8mol/L of 0.5~5ml₃The precipitating is dissolved, is subsequently poured into equipped with 0.4~2ml AG1-X8 resin anion (R.A.) On exchange column, the HNO of 7~8mol/L of 1~10ml is used₃Fe ion and foreign ion, the complex ion quilt of U and Th are fallen in elution Resin adsorption；Then the HCl elution Th ion of 6~8mol/L of 1~10ml is added to the exchange column and collects；Using 1~ Dilute HNO of 0.1~1mol/L of 10ml₃Elution U ion is simultaneously collected.

A preferred embodiment according to the present invention, the cold spring carbonate samples processing method further include one prepare it is to be measured The step of sample: the U solion of collection and Th solion are evaporated, then with 2~5%HNO of mass fraction₃And mass fraction The mixed solution of 0.01~0.03%HF extracts U and Th Isotopic moieties, standby mass-spectrometer measurement.

Technical effect of the invention includes:

Processing method of the present invention includes the split-phase processing to sample: using the heavy-fluid of greater density and the heavy-fluid of smaller density It carries out being mixed to get mixing heavy-fluid, by adjusting mass ratio shared by different heavy-fluids in mixing heavy-fluid, makes the entirety for mixing heavy-fluid Density constantly reduces, and during reduction, utilizes different minerals granularity, density or qualitative difference in SEEP CARBONATE PRECIPITATION KINETICS sample Rock sample is divided into the subsample of different minerals combination by different characteristic, and reaching each subsample has different U, Th contents.For example, optional Select that density is>2.85, sample is divided into 6 by 2.85-2.82,2.82-2.79,2.79-2.76,2.76-2.73 and<2.73g/ml etc. A subsample.The split-phase treatment process is mainly to utilize to mix the physical properties such as important density and different minerals granularity, density, It is sorted for pure physical separation methods, is carried out at normal temperature.It can be effectively to impure cold spring carbonate sample using heavy-fluid split-phase Product carry out physical separation, and can avoid uranium thorium isotope, there is a phenomenon where be fractionated.

Cold spring carbonate samples processing method of the invention, in this field, system uses heavy-fluid split-phase processing method for the first time, together The chemical purification processing method that Shi Peihe is advanced optimized, the cold spring carbonate samples for obtaining final process are adapted to U system and return Line is returned to survey year mode.The experiment proved that can get very accurately using method of the invention²³⁰Th age data.

Detailed description of the invention

Fig. 1 is 5 subsamples that the embodiment of the present invention 1 is obtained using heavy-fluid split-phase²³⁰Th/²³²Th atomic ratio is with heavy-fluid The variation of density.

Fig. 2 is 5 subsamples that the embodiment of the present invention 2 is obtained using heavy-fluid split-phase²³⁰Th/²³²Th atomic ratio is with heavy-fluid The variation of density.

Fig. 3 is that the Osmond type-II of the carbonate chimney A sample of the embodiment of the present invention 1 returns line chart.

Fig. 4 is that the Osmond type-II of the carbonate chimney B sample of the embodiment of the present invention 2 returns line chart.

Specific embodiment

In order to preferably explain the present invention, in order to understand, with reference to the accompanying drawing, by specific embodiment, to this hair It is bright to be described in detail.

The cold spring carbonate samples processing method according to the present invention that year mode is surveyed suitable for the U system tropic, now design is specific Experimental implementation process it is as follows:

The processing of S1 sample split-phase:

S11 sample clean: blocky SEEP CARBONATE PRECIPITATION KINETICS sample surface is rinsed using deionized water, is placed in baking oven Drying, taking-up, which is placed in drier, to be cooled to room temperature.

S12 drills through sample: in sample clean surface, drilling through a small amount of powder sample using micro-, quality is about 0.5~1g.

S13 heavy-fluid split-phase: in draught cupboard, powder sample is added to bromoform (CHBr₃) in heavy-fluid, then to it The density of the middle dehydrated alcohol adjustment heavy-fluid that appropriate low-density is added, as dehydrated alcohol additional amount is continuously increased, bromoform- Ethyl alcohol mixing heavy-fluid density constantly reduces；Density reduce during, due to mineral granularity, density or in nature have difference, The big mineral grain of density first precipitates, the small rear precipitating of density, thus sample is divided into the subsample of different minerals combination, increment Product are separated using centrifuge, obtain 5~7 subsamples, achieve the purpose that each subsample has different U, Th contents.

S14: subsample cleaning: being cleaned each subsample using dehydrated alcohol repeatedly, uses baking oven by sample later Product drying, taking-up, which is placed in drier, to be cooled to room temperature.

The processing of S2 chemical purification:

The dissolution of S21 sample: the chemical pre-treatment of sample carries out in better purifying space, weighs a certain amount of cold spring carbonate increment Product are placed in polytetrafluoroethylene (PTFE) (PFA) beaker, are completely dissolved sample using inorganic reagents such as nitric acid, hydrochloric acid or chloroazotic acid.Specifically Operation can be with are as follows: weighs 0.02~0.2g cold spring carbonate subsample, is placed in polytetrafluoroethylene beaker, 0.5~5ml high is added The dense HNO of purity₃, the dense HF of 0.05~2ml high-purity is added, closed beaker keeps the temperature 1~2 under the conditions of being placed in 120~180 DEG C It opens beaker, is evaporated sample under the conditions of 120~180 DEG C to complete molten sample.

School U-Th in S22: with the high-purity dense HNO of 0.5~5ml₃The sample being evaporated in dissolution S21, is added appropriate (300 μ l)²²⁹Th-²³³U-²³⁶U diluent standing 12~for 24 hours, a few drop (0.05~2ml) HClO are added₄, it is placed on electric hot plate and is evaporated.

S23 Chemical Decomposition: dissolving the sample being evaporated with a small amount of (0.5~5ml) 2mol/L HCl, be added it is appropriate (about 30~ 100ng)FeCl₃Solution adjusts pH=7~8 to there is bronzing flocculent deposit with ammonium hydroxide.It is centrifugated out bronzing Fe (OH)₃ Precipitating, discards supernatant liquor.Bronzing Fe (OH)₃Precipitating discards supernatant liquid using being centrifuged after ultrapure water, repeats to rinse two It is secondary.

S24: the HNO of the 7~8mol/L of a small amount of (0.5~5ml) is used₃Sediment is dissolved out, is poured into equipped with AG1-X8 On the exchange column of characteristic resin, different ions is selected to elute U and Th respectively from the exchange column.Specific operation can be with are as follows: Use 7~8mol/L of 0.5ml HNO₃Sediment is dissolved out, is poured on the exchange column equipped with AG1-X8 resin anion (R.A.), is made With 7~8mol/L of 1ml HNO₃Fe ion and foreign ion are fallen in elution, U and Th complex ion is by resin adsorption.To resins exchange The HCl solution that appropriate (1~10ml) 8mol/L is packed into column elutes Th ion, and collects Th using polytetrafluoroethylene beaker.With Appropriate (1~10ml) 0.1~1mol/L HNO is packed into backward exchange column₃Solution elutes U ion, separately takes polytetrafluoroethylene beaker Collect U.

S3 prepares sample to be tested

S31: machine solution example to be measured in preparation: the solution containing U, Th that step S24 is collected is evaporated, then uses mass fraction 2%HNO₃U and Th Isotopic moieties, standby mass-spectrometer measurement are extracted with the mixed solution of mass fraction 0.01%HF.

According to the experimental implementation process of above-mentioned design, below in conjunction with specific embodiment and implementation result to the present invention into one Step explanation:

Reagent and instrument:

Analyze pure hydrochloric acid, nitric acid: SavillexTM DST- is passed through in Sinopharm Chemical Reagent Co., Ltd.'s production The purification of 1000 sub-boiling distillation device sub-boiling distillations.

Ultrapure hydrofluoric acid: the production of Merck KGaA company, it is ultrapure.

NH₄OH: Japanese Kanto Kagaku K. K., it is ultrapure.

Bromoform (CHBr₃): pure, density 2.889~2.891 is analyzed in Sinopharm Chemical Reagent Co., Ltd.'s production (20℃)/(g/ml)。

Dehydrated alcohol: Sinopharm Chemical Reagent Co., Ltd.'s production, analysis is pure, and density 0.789~0.791 (20 DEG C)/ (g/ml)

FeCl₃Solution: AlfaAesar (China) Chemical Co., Ltd. iron powder (~22 mesh, 99.998%) is steamed using Asia boiling The pure concentrated hydrochloric acid dissolution of the analysis evaporated is configured to solution.

AG1-X8: pure, 100~200 mesh are analyzed in the production of Bio-Rad company, the U.S..

Ultrapure water: the preparation of Millipore Corp., U.S. Millipore-Q Element system, water outlet resistivity 18.2M Ω/ cm。

The Neptune Plus model of MC-ICP MS:Thermo Scientific company production receives inductive coupling etc. more Gas ions mass spectrograph；

Cetac Arudus II micro-sampling system: Teledyne Cetac company, the U.S. is equipped with 50 μ l/min flow velocitys Atomizer.

NBS CRM-112A standard sample: it is issued by the U.S. Department of Energy laboratory New Brunswick.

Vessel: the production of Savillex company, the U.S. is 30ml round bottom PFA Teflon beaker with cover, uses analysis using preceding Pure chloroazotic acid, the 10% pure HNO of analysis₃, the 10% pure HCl of analysis and the 5% pure HNO of analysis₃It is cleaned.

Embodiment 1

Below by taking A cold spring carbonate samples as an example, by its method according to the invention carry out sample treatment, then prepare to Sample, upper MC-ICP MS mass spectrograph test.

Step 1: sample split-phase

(1) sample clean: SEEP CARBONATE PRECIPITATION KINETICS sample surfaces are rinsed using deionized water, are placed on drying in baking oven Dry, temperature is 60~80 DEG C, and taking-up, which is placed in drier, to be cooled to room temperature.

(2) it drills through sample: in sample clean surface, drilling through powder sample, quality 0.5g using micro-.

(3) heavy-fluid is prepared: in draught cupboard, 0.5g cold spring carbonate samples powder being added to 27ml bromoform heavy-fluid In, 0.5ml dehydrated alcohol is added into heavy-fluid, the mixing heavy-fluid of density 2.85g/ml is obtained, using centrifuge by sample and again The centrifugation of liquid mixed solution, isolates first subsample a.

(4) heavy-fluid split-phase: by repeating step (3), it may be assumed that

0.16ml dehydrated alcohol is added into heavy-fluid, obtains the mixing heavy-fluid of density 2.82g/ml, using centrifuge by sample Product and the centrifugation of heavy-fluid mixed solution, isolate second subsample b.

0.16ml dehydrated alcohol is added into heavy-fluid, obtains the mixing heavy-fluid of density 2.79g/ml, using centrifuge by sample Product and the centrifugation of heavy-fluid mixed solution, isolate third subsample c.

0.16ml dehydrated alcohol is added into heavy-fluid, obtains the mixing heavy-fluid of density 2.76g/ml, using centrifuge by sample Product and the centrifugation of heavy-fluid mixed solution, isolate the 4th subsample d.

0.5ml dehydrated alcohol is added into heavy-fluid, obtaining density is the < mixing heavy-fluid of 2.76g/ml, uses centrifuge will Sample and the centrifugation of heavy-fluid mixed solution, isolate the 5th subsample e.

Be the corresponding subsample number isolated of different heavy-fluid density referring to following table (table 1): the present embodiment one isolates 5 subsamples out, it is therefore an objective to which sample is divided into the increment of different minerals combination according to mineral granularity, specific gravity or qualitative difference Product achieve the purpose that each subsample has different U, Th contents.

Table 1:A sample heavy-fluid specific gravity and segregant sample number into spectrum

Step	Heavy-fluid density (g/ml)	Subsample number
			1	>2.85	a
2	2.82-2.85	b
			3	2.79-2.82	c
4	2.76-2.79	d
			5	<2.76	e

(5) subsample cleans: cleaning each subsample repeatedly using dehydrated alcohol, uses baking oven by sample later Drying, temperature are 60~80 DEG C, and taking-up, which is placed in drier, to be cooled to room temperature.

Step 2: chemical purification processing

(1) subsample dissolves: the chemical pre-treatment of sample carries out in the clean room of three-level air filtration, and it is cold to weigh 20mg Spring carbonate subsample, is placed in polytetrafluoroethylene beaker, and the dense HNO of 1ml high-purity is added₃, the high-purity dense HF of 0.1ml is added, Closed beaker keeps the temperature 1~2 day under the conditions of being placed in 130 DEG C, and sample is entirely molten, opens beaker, is evaporated sample under the conditions of 150 DEG C.

(2) U-Th being added in U-Th diluent dilute sample: the high-purity dense HNO of 0.5ml is used₃The son being evaporated in dissolution (5) 300 μ l are added in sample²²⁹Th-²³³U-²³⁶U diluent is stood overnight, and the high-purity dense HClO of 0.05ml is added₄Having in removal sample Machine matter is placed on electric hot plate under the conditions of 120~180 DEG C until being evaporated.

(3) Chemical Decomposition: dissolving the sample being evaporated with 0.5ml 2mol/L HCl, and gross mass 30ng FeCl is added₃, with 0.2ml concentrated ammonia liquor is added afterwards and adjusts pH=7~8 to there is bronzing flocculent deposit, stands and is placed in 15ml centrifuge tube, use It after parafilm seals centrifuge tube, is centrifuged 7 minutes, revolving speed is 3500 revs/min.It is centrifugated out bronzing Fe (OH)₃Precipitating is abandoned Remove supernatant liquor.Bronzing Fe (OH)₃Precipitating discards supernatant liquid using being centrifuged after 8ml ultrapure water, repeats to rinse twice.

(4) U-Th is separated: using 0.5ml 7mol/L HNO₃It dissolves out Fe (OH)₃Precipitating, is poured into equipped with 0.4ml (resin-column uses 1.2ml 7mol/L HNO before being poured into the exchange column of AG1-X8 resin anion (R.A.)₃With 1.2ml 8mol/ L HCl is eluted pre-processed in advance), use 1.6ml 7mol/L HNO₃Fe ion and foreign ion are eluted, U and Th are by this Resin adsorption.The 8mol/L HCl solution of 1.6ml is packed into exchange column again, is eluted out Th, is collected in 7ml PFA beaker； The HNO of 1.6ml 0.1mol/L is finally packed into exchange column₃, it is eluted out U, is collected in 30ml PFA beaker.

Step 3: sample to be tested is prepared

(1) machine solution to be measured in preparation: the solution containing U, Th of collection is evaporated under the conditions of 180 DEG C respectively respectively, then With 0.5ml 2%HNO₃The Isotopic moieties of U and Th are extracted with the mixed acid solution of 0.01%HF, in case mass-spectrometer measurement.

Step 4: mass spectrograph test

(1) MC-ICP MS is measured: U the and Th isotope solution collected by above-mentioned chemical purification process uses Neptune Plus type MC-ICPMS measures isotopic ratio.Specific instrument setting parameter is referring to table 2, other references when measurement Document 4 (Wang Lisheng etc., 2016).It can be obtained by the mass-spectrometer measurement technology that multiple groups standard U measured data shows that this work is drafted Stable ion intensity of flow is obtained, is had reached simultaneously for the data precision of isotopic ratio some thousandths of.

Parameter is arranged in the instrument that table 2:Neptune Plus type MC-ICPMS measures U-Th isotope

By the above test method, measure²³⁰Th age and U-Th isotope result are shown in Table 3 respectively.

Embodiment 2

Embodiment 2 and the difference of embodiment 1 are only that it is B that 2 applied geology rock sample of embodiment, which is SEEP CARBONATE PRECIPITATION KINETICS,.It presses According to operating procedure substantially the same manner as Example 1, a~e totally 5 subsamples are equally obtained using heavy-fluid split-phase method, are measured²³⁰Th Age and U-Th isotope result are shown in Table 3 respectively.

The U-series Age and U-Th isotope analysis data of table 3:A and B sample

[reproducibility inspection]

NBS-CRM-112A's (high pure metal uranium is issued by the U.S. Department of Energy laboratory New Brunswick)²³⁴U/²³⁸U Average value is respectively (52.85 ± 0.03) × 10^-6(n=12, ± 2 σ), δ²³⁴U average value be -38.5 ± 0.5 ‰ (n=12, ± 2 σ).The result and the average value that MC-ICP MS is delivered in laboratory in the world are consistent (referring to 4 Wang Lisheng of document in error range Deng 2016；Wang et al.,2017).

[other parameters]

The background noise of SEM is less than 1.5cpm, and gain diurnal variation is less than 1%.Whole flow process²³⁸U、²³⁰Th and²³²Th sheet Floors is respectively 8.6pg, 0.05fg and 0.2pg.

Each subsample²³⁰Th/²³²Th atomic ratio reduces variation in (2.99~4.08) × 10 with heavy-fluid density^-6, A With the related coefficient (R of B sample²) it was respectively 0.988 and 0.856 (respectively referring to Fig. 1, Fig. 2).It is indicated above that impure cold spring carbon Hydrochlorate, which carries out the U-Th tropic with heavy-fluid split-phase, to be determined year, and technical method is successful.

It is drawn according to 3 data of table²³²Th/²³⁸U-²³⁰Th/²³⁸U-²³⁴U/²³⁸U three-dimensional returns line chart (Fig. 3~Fig. 4), ISOPLOT/EX program obtains the age data of sample, and reliability is examined or check with parameter MSWD (< 1) and POF (≤ca.1).It obtains The tropic of sample A and B²³⁰The Th age is respectively 28.8 ± 0.4 and 26.1 ± 0.4ka.

Fig. 3 is that the Osmond type-II of the carbonate chimney A sample of the embodiment of the present invention 1 returns line chart, and Fig. 4 is this hair The Osmond type-II of the carbonate chimney B sample of bright embodiment 2 returns line chart.Wherein dotted line is ISOPLOT/EX journey in figure The tropic that sequence calculates, elliptical point represent 2 σ errors.Intercept represents the pure carbonate end member for eliminating clast pollution.It calculates²³⁰Th Age, initially²³⁴U/²³⁸U ratio and tropic parameter are listed in table 4.

Table 4: tropic correction obtains pure carbonate²³⁴U/²³⁸U and²³⁰Th^/238U ratio and age value

Note: MSWD indicates weighted mean square in table；POF indicates Fitted probability.

Technical effect of the invention: the present invention determines the use heavy-fluid split-phase in year for cold spring carbonate samples uranium series isochrone Technology and the small size chemical purification technology of Parameter Conditions optimization；Thus avoid the preceding processing that sample is tested in mass spectrograph Fractionation phenomenon occurs for uranium thorium isotope in the process.And through experiment show, this method favorable reproducibility be can get accurate²³⁰Th Age data, suitable for the processing to impure cold spring carbonate samples.

[bibliography]

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Document 2: Ma Zhibang, Zheng Mianping, Wu Zhonghai, Tamara Manina.Impure Carbonate U-Th isochrone determines year and isotope point Evaporate the influence to the age.Geology journal, 2010a, 84 (8), 1146-1154.

Document 3: Sun Zhilei, He Yongjun, Li Jun, Huang Wei, Li Qing, Li Jiwei, Wang Feng.Methane anaerobic oxidized in marine environment Mechanism and environmental effect.Advances in Earth Science, 2012,27 (11), 1262-1273.

Document 4: Wang Lisheng, Ma Zhibang, Cheng Hai, Duan Wuhui, Xiao Jule.MC-ICPMS measures Uranium Series Dating standard specimen The 230Th age, mass spectrum journal, 2016.37 (3): 262-272.

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Document 8:Feng, D., Roberts, Harry.H., Cheng, Hai, Peckmann, J., Bohrmann, G., Edwards,R.L.,Chen,D.,2010.U/Th dating of cold-seep carbonates:An initial comparison.Deep-Sea Research II,57:2055–2060.

Document 9:Herczeg A.L, Chapman, A., 1991.Uranium-series dating of lake and dune deposits in southeastern Australia:a reconnaissance.Palaeogeography, Palaeoclimatology,Palaeoecology,84:285-298.

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Document 13:Li, J.W., Peng, X.T., Bai, S.J., Chen, Z.Y., Nostrand, J.D.V., 2018.Biogeochemical processes controlling authigenic carbonate formation within the sediment column from the Okinawa Trough.Geochimica et Cosmochimica Acta,222,363–382.

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Claims

1. a kind of cold spring carbonate samples processing method for surveying year mode suitable for the U system tropic, which is characterized in that the processing side Method includes:

S1 handles the split-phase of sample:

The powder sample of cold spring carbonate is added in mixing heavy-fluid, the mixing heavy-fluid includes the first heavy-fluid and the second heavy-fluid, First heavy-fluid is bromoform, and the second heavy-fluid is dehydrated alcohol；By being continuously increased second heavy-fluid in the mixing In heavy-fluid proportion make it is described mixing heavy-fluid density be gradually reduced, by different minerals in the powder sample density and The otherness of granularity successively isolates the subsample of several cold spring carbonate from mixing heavy-fluid；

S2 carries out chemical purification processing to each subsample:

The dissolution of S21 sample: the subsample is dissolved using inorganic solvent, then solvent evaporated, concrete operations are as follows: by 0.1~ The subsample of 0.2g cold spring carbonate is placed in a beaker, and the dense HNO of 0.1~10ml high-purity is added to the beaker₃Or concentrated hydrochloric acid, Subsample described in aqua regia dissolution, is added the dense HF of 0.05~2ml high-purity, and closed beaker is protected under the conditions of being placed in 120~180 DEG C Temperature 1~2 day opens beaker, is evaporated sample under the conditions of 120~180 DEG C to complete molten sample；

S22 dilutes U-Th: adding into sample²²⁹Th-²³³U-²³⁶U diluent, standing 12~for 24 hours, it is then evaporated, concrete operations are as follows: Use the dense HNO of 0.1~10ml high-purity₃Appropriate 300 μ l is added in sample dissolution²²⁹Th-²³³U-²³⁶U diluent standing 12~for 24 hours, 0.05~2ml HClO is added₄Solution is evaporated with removing the organic matter in sample；

S23 Chemical Decomposition: use inorganic acid solution sample, be added can raw rubber body metal ion, use ammonium hydroxide adjust solution ph To alkalescent, make the hydroxide colloid precipitating for obtaining the metal ion, the hydroxide colloid precipitating by sample U and Th is adsorbed, and is then separated and is cleaned the hydroxide colloid precipitating；

S24 U-Th absorption and elution: the HNO of 7~8mol/L of 0.1~5ml is used₃The precipitating is dissolved, is subsequently poured into and is equipped with On the exchange column of 0.4~5ml AG1-X8 resin anion (R.A.), 7~8mol/L HNO of 5~50ml is used₃Elution fall Fe ion and Foreign ion, U and Th complex ion are adsorbed by the resin anion (R.A.)；Then to the exchange column be added 1~50ml 6~ The HCl elution Th ion of 8mol/L is simultaneously collected, then using dilute HNO of 0.1~1mol/L of 5~50ml₃Elution U ion is simultaneously received Collection.

2. cold spring carbonate samples processing method according to claim 1, it is characterised in that:

Step S1 handles to obtain the subsample of 5~7 cold spring carbonate, is cleaned using low-density alcohol, then in dry environment It is cooled to room temperature.

3. cold spring carbonate samples processing method according to claim 1, it is characterised in that:

In the step S23, using the diluted hydrochloric acid dissolution sample of 0.1~10ml, 1~2mol/L, Fe is added³⁺Or Al³⁺, use ammonia Water adjusts pH value of solution=7~8, generates Fe (OH)₃Or Al (OH)₃Colloid, U and Th in sample form complexing under ammonium hydroxide effect Object is simultaneously adsorbed by the colloid, so that the colloid is become larger and is reformed precipitating, separates and clean the precipitating.

4. cold spring carbonate samples processing method according to claim 1, it is characterised in that: the cold spring carbonate samples Processing method further includes the steps for preparing a sample to be tested: the U solion of collection and Th solion being evaporated, quality is used 2~5%HNO of score₃U and Th Isotopic moieties are extracted with the mixed solution of 0.01~0.03%HF of mass fraction, standby mass spectrum is surveyed Amount.