Method for calculating mineral formation temperature based on chlorite spectrum

Abstract

The invention relates to the field of mineral exploration and evaluation, in particular to a method for calculating mineral formation temperature based on chlorite spectrum. The invention discloses a method for calculating mineral formation temperature based on chlorite spectrum. The method comprises the following steps: S1, recording related information of each chlorite sample; s2, the Fe-OH wavelength value of each chlorite sample is obtained; s3, respectively calculating the mineralization temperature and the content of main elements of the chlorite sample; and S4, according to the mineralization temperature and the main element content information obtained in the S3, determining the mineralization environment and classification of the corresponding chlorite sample. According to the method disclosed by the invention, the conventional calculation of the chlorite mineral temperature is converted from the traditional calculation of obtaining data results of major elements based on laboratory electronic probe analysis and test into the calculation of obtaining characteristic wavelength parameters based on field on-site short-wave infrared spectrum test; and convenience is provided for rapid discrimination of a mineral formation environment and an alteration zone where the mineral formation environment is located, and the working efficiency of prospecting is greatly improved.

Description

Technical Field

[0001] The invention relates to the field of mineral exploration and evaluation, and in particular to a method for calculating mineral formation temperature based on chlorite spectrum. Background Art

[0002] Chlorite minerals are widely formed in different geological environments. Their genesis includes magmatic hydrothermal genesis and metamorphic genesis. They can be formed in medium-high temperature, medium-low temperature, and low temperature environments. Especially in porphyry deposits, they can be formed in high-temperature sericite alteration zones and low-temperature chlorite alteration zones. Therefore, accurate and rapid determination of the formation temperature of chlorite has a good guiding significance for subsequent further prospecting and exploration.

[0003] The existing calculations of mineral formation temperatures are based on the major element data obtained by electron probe microprobe (EMPA) analysis or trace element data obtained by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis, and are calculated using empirical mineral temperature formulas, such as biotite and amphibole Ti thermometers, chlorite Al thermometers, zircon Zr saturation thermometers and Ti thermometers, rutile Zr thermometers, etc. Before calculating the temperature using the above methods, EPMA and LA-ICP-MS analysis tests must be performed, both of which have the characteristics of long cycles and high costs, and cannot meet the urgent needs of economic and efficient exploration in the current mineral prospecting process. Summary of the invention

[0004] In view of this, the present invention proposes a method for quantitatively calculating the formation temperature of minerals using the characteristic parameters of chlorite short-wave infrared spectrum (Fe-OH wavelength), which can provide a basis for us to quickly determine the formation environment and alteration zone of the minerals, thereby guiding the next step of mineral exploration deployment.

[0005] The method for calculating the mineral formation temperature based on chlorite spectrum comprises the following steps:

[0006] S1. Collect chlorite samples and record relevant information of each chlorite sample;

[0007] S2. Perform short-wave infrared spectrum test on each chlorite sample to obtain the Fe-OH wavelength value of each chlorite sample;

[0008] S3. Taking the absorption peak of the Fe-OH wavelength of chlorite as the boundary, calculate the formation temperature and the content of the main elements of the corresponding chlorite sample when the Fe-OH wavelength of the chlorite sample is greater than or less than the absorption peak;

[0009] S4. According to the temperature and main element content information obtained in S3, the mineralization environment and classification of the corresponding chlorite sample are determined.

[0010] Furthermore, in S3, the absorption peak of chlorite Fe-OH wavelength is 2255nm, and:

[0011] If the Fe-OH wavelength value of the chlorite sample measured in S2 is less than or equal to 2255 nm, the formation temperature of the corresponding chlorite sample is calculated by formula (1), where the expression of formula (1) is:

[0012] T(℃)=8.5475*Pos2250-18994±50 (1)

[0013] In the above formula, Pos2250 is the Fe-OH wavelength value of the chlorite sample;

[0014] If the Fe-OH wavelength value of the chlorite sample measured in S2 is greater than 2255 nm, the corresponding chlorite formation temperature is calculated by formula (2), where the expression of formula (1) is:

[0015] T(℃)=8.7646*Pos2250-19609±50 (2)

[0016] In the above formula, Pos2250 is the Fe-OH wavelength value of the chlorite sample.

[0017] Furthermore, in S3, the main elements in each chlorite sample are tested to be Fe, Mg, and Si.

[0018] Furthermore, in S3, the absorption peak of chlorite Fe-OH wavelength is 2255nm, and:

[0019] If the Fe-OH wavelength value of the chlorite sample measured in S2 is less than or equal to 2255 nm, the contents of the three main elements Fe, Mg and Si in the corresponding chlorite sample are calculated by formulas (3)-(5), where the calculation formula for the Fe element is:

[0020] Fe(apfu)=0.0783*Pos2250-174.41±0.5 (3)

[0021] In the above formula, Pos2250 is the Fe-OH wavelength value of the chlorite sample;

[0022] The calculation formula of Mg element is:

[0023] Mg(apfu)=-0.0949*Pos2250+216.25±0.5 (4)

[0024] In the above formula, Pos2250 is the Fe-OH wavelength value of the chlorite sample;

[0025] Si(apfu)=-0.0494*Pos2250+114.14±0.2 (5)

[0026] In the above formula, Pos2250 is the Fe-OH wavelength value of the chlorite sample;

[0027] If the Fe-OH wavelength value of the chlorite sample measured in S2 is greater than 2255nm, the contents of the three main elements Fe, Mg and Si in the corresponding chlorite sample are calculated by equations (6)-(8) respectively, where the calculation formula for the Fe element is:

[0028] Fe(apfu)=0.25*Pos2250-560.91±0.5 (6)

[0029] In the above formula, Pos2250 is the Fe-OH wavelength value of the chlorite sample;

[0030] The calculation formula of Mg element is:

[0031] Mgapfu)=-0.161*Pos2250+364.78±0.5 (7)

[0032] In the above formula, Pos2250 is the Fe-OH wavelength value of the chlorite sample;

[0033] Si(apfu)=-0.0696*Pos2250+160.19±0.2 (8)

[0034] In the above formula, Pos2250 is the Fe-OH wavelength value of the chlorite sample.

[0035] Further, in S4, based on the calculation result of the formation temperature T of each chlorite sample in S3, if 200℃≦T≦300℃, the chlorite sample is formed in a medium-high temperature environment, and when 100℃<T<200℃, the chlorite sample is formed in a medium-low temperature environment.

[0036] Furthermore, in S4, the classification of chlorite is determined based on the range of the content of the Fe element and the Si element in each chlorite sample in S3.

[0037] The technical solution provided by the present invention has the following beneficial effects: the method for calculating the mineral formation temperature based on the chlorite spectrum of the present invention transforms the existing chlorite mineral temperature calculation from the traditional calculation based on laboratory electron probe analysis test to obtain the main element data results to the calculation based on field short-wave infrared spectrum test to obtain the characteristic wavelength parameters, which facilitates the rapid identification of the mineral formation environment and the alteration zone in which it is located, and greatly improves the efficiency of mineral prospecting. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a flow chart of a method for calculating the mineral formation temperature based on chlorite spectrum of the present invention;

[0039] Figure 2 a is a correlation analysis diagram of the Fe-OH wavelength and the formation temperature of chlorite of the present invention;

[0040] Figure 2 b is a correlation analysis diagram of the Fe-OH wavelength and Fe content of chlorite of the present invention;

[0041] Figure 2 c is a correlation analysis diagram of the Fe-OH wavelength and Mg content of chlorite of the present invention;

[0042] Figure 2 d is a correlation analysis diagram of the Fe-OH wavelength and Si content of chlorite of the present invention;

[0043] Figure 3 It is the classification diagram of chlorite components of the present invention. DETAILED DESCRIPTION

[0044] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0045] Chlorite is composed of alternating tetrahedrons and octahedrons, and its main component has the chemical formula Y3[Z4O 10 ](OH)2·Y3(OH)6, where Y mainly represents Mg 2+ , Fe 2+ 、Al 3+ and Fe 3+ ; Z is mainly Si and Al. With the change of physical and chemical environment, chlorite will undergo some replacement, such as Si and Al in tetrahedral position IV and octahedral position Al IV , Mg, Fe 2+ , Fe 3+ They can replace each other, thus causing changes in the composition of chlorite. Studies have shown that the Fe-Mg substitution in the chlorite octahedron and the Al substitution in the tetrahedron can increase the Fe-OH wavelength (Pos2250) of chlorite. At the same time, the change in chlorite temperature is also mainly controlled by the change in the Fe, Mg, and Al content in the mineral. Therefore, based on the relationship between the characteristic wavelength and temperature change of chlorite and the mineral composition, it is feasible to establish a method for calculating the formation temperature of chlorite minerals based on short-wave infrared spectroscopy.

[0046] Specifically, the present invention discloses a method for calculating the mineral formation temperature based on chlorite spectrum, comprising the following steps:

[0047] S1. Collect chlorite samples and record relevant information of each chlorite sample; wherein the relevant information of the chlorite sample includes sample collection coordinates, lithology, chlorite characteristics (vein or disseminated), mineralization, and location;

[0048] S2. Perform a short-wave infrared spectrum test on each chlorite sample to obtain the Fe-OH wavelength value of each chlorite sample. In the present invention, the Fe-OH wavelength value of the sample can be tested by using a portable short-wave infrared spectrometer (TerraSpec) or other testing instruments.

[0049] S3. Taking the absorption peak of the Fe-OH wavelength of chlorite as the boundary, calculate the formation temperature and the content of the main elements of the corresponding chlorite sample when the Fe-OH wavelength of the chlorite sample is greater than or less than the absorption peak; wherein, the derivation process of the calculation formula of the formation temperature and the content of the main elements of the chlorite sample is:

[0050] S31. Collect data samples: Collect short-wave infrared spectrum data and electron probe major element data of chlorite related to magmatic-hydrothermal deposits through Chinese and English literature databases such as CNKI and WEB of SCIENCE to obtain data samples;

[0051] S32. Calculate chlorite temperature

[0052] Based on the difference in the content of the main elements Fe, Mg, and Al in chlorite, the formation temperature of chlorite minerals was calculated using the chlorite temperature calculation formula, that is, based on the laboratory electron probe data Al IV , Fe, Mg content calculated chlorite mineral formation temperature, where Fe = Fe 2+ +Fe 3+ , the specific calculation formula is as follows:

[0053]

[0054] In the formula, Al IV is the Al content of chlorite calculated based on 14 oxygen atoms, Fe is the Fe content of chlorite, and Mg is the Mg content of chlorite. It should be noted that the chlorite temperature calculation formula of the present invention is the prior art;

[0055] S33. Correlation analysis

[0056] The short-wave infrared spectrum Fe-OH wavelength (Pos2250) of chlorite in the data sample is used as the horizontal axis, and the chlorite formation temperature and Mg, Fe, and Si contents calculated in S32 are used as the vertical axis to make a scatter plot in Excel to analyze the correlation between the Fe-OH wavelength and the chlorite composition. The results are as follows: Figure 2 As shown. Figure 2From the data, we can see that the wavelength of Fe-OH in chlorite (Pos2250) is positively correlated with the Fe content, negatively correlated with the Mg content, and negatively correlated with the Si content, which reflects that Fe replaces Mg in the octahedron of chlorite and Al replaces Si in the tetrahedron. The increase of Fe content and the decrease of Si content can cause the wavelength of Fe-OH in chlorite (Pos2250) to increase. Figure 2 (a) It can be seen that the Fe-OH wavelength (Pos2250) of chlorite is positively correlated with temperature. Under relatively low temperature conditions, Mg-rich and Fe-poor chlorite is formed, and the Fe-OH wavelength (Pos2250) is mainly short-wave. Under relatively high temperature conditions, Fe-rich and Mg-poor chlorite is formed, and the Fe-OH wavelength (Pos2250) is mainly long-wave.

[0057] S34. Obtain the calculation formula for chlorite formation temperature and major element content

[0058] Further analysis found that the Fe-OH wavelength of chlorite showed inconsistent correlation with its formation temperature and major element content in different bands, which is related to the fact that the change of the wavelength of the short-wave infrared spectrum of chlorite is controlled by multiple factors. The present invention uses the wavelength (Pos2250) of the characteristic parameter of the infrared spectrum of chlorite Fe-OH as 2255nm as the boundary, and according to the correlation analysis results in S3, the wavelength of chlorite Fe-OH and its formation temperature data are linearly fitted to obtain the calculation formula of the formation temperature of chlorite when the wavelength of chlorite Fe-OH is greater than or less than 2255nm, that is:

[0059] When the field test interprets the chlorite Fe-OH wavelength Pos2250≤2255nm, the chlorite formation temperature calculation formula is: T(℃)=8.5475*Pos2250-18994±50;

[0060] When the chlorite Fe-OH wavelength Pos2250 is interpreted as 2255nm in field tests, the chlorite formation temperature calculation formula is: T(℃)=8.7646*Pos2250-19609±50.

[0061] Similarly, the correlation between the Fe-OH wavelength of chlorite and the three major elements of Fe, Mg and Si in chlorite was linearly fitted, and the calculation formulas for the contents of the three major elements of Fe, Mg and Si in chlorite were obtained when the Fe-OH wavelength of chlorite was greater than or less than 2255nm, namely:

[0062] When the field test interprets the chlorite Fe-OH wavelength Pos2250≤2255nm:

[0063] The calculation formula of Fe content in chlorite spectrum is: Fe(apfu)=0.0783*Pos2250-174.41±0.5;

[0064] The calculation formula of chlorite spectrum Mg content is: Mg(apfu)=-0.0949*Pos2250+216.25±0.5;

[0065] The calculation formula of chlorite spectrum Si content is: Si(apfu)=-0.0494*Pos2250+114.14±0.2;

[0066] When the field test interprets the chlorite Fe-OH wavelength Pos2250>2255nm:

[0067] The calculation formula of Fe content in chlorite spectrum is: Fe(apfu)=0.25*Pos2250-560.91±0.5;

[0068] The calculation formula of chlorite spectrum Mg content is: Mg(apfu)=-0.161*Pos2250+364.78±0.5;

[0069] The calculation formula of chlorite spectrum Si content is: Si(apfu)=-0.0696*Pos2250+160.19±0.2;

[0070] S4. Identification of chlorite formation environment and type

[0071] Based on the calculation results of the chlorite formation temperature T in S4, if 200℃≦T≦300℃, it can be judged that the chlorite was formed in a medium-high temperature environment, such as a sericite alteration zone; when 100℃<T<200℃, it can be judged that the chlorite was formed in a medium-low temperature environment, such as a pyrophyllite alteration zone.

[0072] Based on the calculation results of the Si and Fe contents of chlorite in step S4, a chlorite composition classification diagram (Sivs.Fe) is drawn, and the results are as follows: Figure 2 As shown, according to the range of Fe and Si content, chlorite can be classified into brittle chlorite, pseudo-lepidolite, ferrochlore, chlorite, clinochlore, dense chlorite, ferromagnesian chlorite, diabase or chlorite. It should be noted that the classification of chlorite in the present invention belongs to the prior art. For the classification standard, please refer to the relevant papers and documents Wiewióra and Weiss, 1990; Inoue et al., 2009.

[0073] The method of calculating the formation temperature of minerals based on the chlorite spectrum of the present invention transforms the existing chlorite mineral temperature calculation from the traditional calculation based on laboratory electron probe analysis test to obtain the main element data results to the calculation based on field short-wave infrared spectrum test to obtain the characteristic wavelength parameters, which provides convenience for the rapid identification of the mineral formation environment and the alteration zone in which it is located, and greatly improves the efficiency of prospecting work.

[0074] <Example 1>

[0075] The method for calculating the formation temperature of minerals based on the chlorite spectrum of the present invention is used to calculate the formation temperature of chlorite minerals in the Juno porphyry deposit, comprising the following steps:

[0076] a. Geological mapping: Through mapping, the occurrence characteristics of chlorite exposed on the surface of the Juneau deposit can be identified, including vein-like, impregnated, and agglomerated forms.

[0077] b. Field sample collection: Collect chlorite-containing samples in the Juneau mining area. During the sampling process, record the following information truthfully and in detail:

[0078] Sampling No. X Y Lithology Chlorite characteristics Mineralization Place 10101-1 547907 3281087 Monzogranite porphyry Dip Minor pyritization Juneau 1301-1 545227 3281026 Monzogranite Pulse none Juneau 4033-1 543992 3280278 Quartz porphyry Lumpy Minor chalcopyrite mineralization Juneau … … … … … … …

[0079] c. Sample testing: The collected chlorite-containing samples were tested in the field using a portable short-wave infrared spectrometer (TerraSpec).

[0080] d. Data processing: The obtained spectral data were interpreted using the spectral interpretation software (TSG) to extract the Fe-OH wavelength (Pos2250). The interpretation results showed that the Fe-OH wavelength (Pos2250) of the chlorite samples collected in the Juneau mining area varied between 2248 and 2255 nm.

[0081] e. Calculation of mineral temperature and composition: The spectral characteristics of chlorite interpreted from the Juneau mining area are consistent with situation ① When the field test interprets the chlorite Fe-OH wavelength Pos2250≤2255nm.

[0082] Using the chlorite spectrothermometer T (℃) = 8.5475*Pos2250-18994±50, it is calculated that the formation temperature range is between 207 and 346℃;

[0083] Using the chlorite spectrum Fe content calculation formula Fe (apfu) = 0.0783 * Pos2250-174.41 ± 0.5, the Fe content range is calculated to be between 1.2 and 2.3 apfu;

[0084] Using the chlorite spectrum Mg content calculation formula Mg (apfu) = -0.0949*Pos2250+216.25±0.5, the calculated Mg content range is between 2.5 and 3.6 apfu;

[0085] Using the chlorite spectrum Si content calculation formula Si (apfu) = -0.0494*Pos2250 + 114.14 ± 0.2, it is calculated that the Si content range is between 2.5 and 3.1 apfu.

[0086] f. Identification of chlorite formation environment and type: Based on the above temperature and composition calculation results, it is determined that the chlorite samples collected in the Juneau mining area were formed in a medium-high temperature environment and are mainly products of sericite alteration, and are mainly classified into ferrochlore and pyrochlore. The above identification results are basically consistent with the microscopic identification results and the electron probe data analysis results, proving that the method proposed in the present invention is effective.

[0087] The technical solution provided by the present invention has the following beneficial effects: the method for calculating the mineral formation temperature based on the chlorite spectrum of the present invention transforms the existing chlorite mineral temperature calculation from the traditional calculation based on laboratory electron probe analysis test to obtain the main element data results to the calculation based on field short-wave infrared spectrum test to obtain the characteristic wavelength parameters, which facilitates the rapid identification of the mineral formation environment and the alteration zone in which it is located, and greatly improves the efficiency of mineral prospecting.

[0088] In the absence of conflict, the above embodiments and features in the embodiments may be combined with each other.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for calculating the mineral formation temperature based on chlorite spectrum, characterized in that: The following steps are involved: S1. Collect chlorite samples and record relevant information of each chlorite sample; S2. Perform short-wave infrared spectrum test on each chlorite sample to obtain the Fe-OH wavelength value of each chlorite sample; S3. Taking the absorption peak of the Fe-OH wavelength of chlorite as the boundary, calculate the formation temperature and the content of the main elements of the corresponding chlorite sample when the Fe-OH wavelength of the chlorite sample is greater than or less than the absorption peak; S4. According to the temperature and main element content information obtained in S3, the mineralization environment and classification of the corresponding chlorite sample are determined.

2. The method for calculating the mineral formation temperature based on chlorite spectrum according to claim 1, characterized in that: In S3, the absorption peak of chlorite Fe-OH wavelength is 2255nm, and: If the Fe-OH wavelength value of the chlorite sample measured in S2 is less than or equal to 2255 nm, the formation temperature of the corresponding chlorite sample is calculated by formula (1), where the expression of formula (1) is: T(℃)=8.5475*Pos2250-18994±50 (1) In the above formula, Pos2250 is the Fe-OH wavelength value of the chlorite sample; If the Fe-OH wavelength value of the chlorite sample measured in S2 is greater than 2255 nm, the corresponding chlorite formation temperature is calculated by formula (2), where the expression of formula (1) is: T(℃)=8.7646*Pos2250-19609±50 (2) In the above formula, Pos2250 is the Fe-OH wavelength value of the chlorite sample.

3. The method for calculating the mineral formation temperature based on chlorite spectrum according to claim 1, characterized in that: In S3, the main elements in each chlorite sample tested are Fe, Mg, and Si.

4. The method for calculating the mineral formation temperature based on chlorite spectrum according to claim 3, characterized in that: In S3, the absorption peak of chlorite Fe-OH wavelength is 2255nm, and: If the Fe-OH wavelength value of the chlorite sample measured in S2 is less than or equal to 2255 nm, the contents of the three main elements Fe, Mg and Si in the corresponding chlorite sample are calculated by formulas (3)-(5), where the calculation formula for the Fe element is: Fe(apfu)=0.0783*Pos2250-174.41±0.5 (3) In the above formula, Pos2250 is the Fe-OH wavelength value of the chlorite sample; The calculation formula of Mg element is: Mg(apfu)=-0.0949*Pos2250+216.25±0.5 (4) In the above formula, Pos2250 is the Fe-OH wavelength value of the chlorite sample; Si(apfu)=-0.0494*Pos2250+114.14±0.2 (5) In the above formula, Pos2250 is the Fe-OH wavelength value of the chlorite sample; If the Fe-OH wavelength value of the chlorite sample measured in S2 is greater than 2255nm, the contents of the three main elements Fe, Mg and Si in the corresponding chlorite sample are calculated by equations (6)-(8) respectively, where the calculation formula for the Fe element is: Fe(apfu)=0.25*Pos2250-560.91±0.5 (6) In the above formula, Pos2250 is the Fe-OH wavelength value of the chlorite sample; The calculation formula of Mg element is: Mg(apfu)=-0.161*Pos2250+364.78±0.5 (7) In the above formula, Pos2250 is the Fe-OH wavelength value of the chlorite sample; Si(apfu)=-0.0696*Pos2250+160.19±0.2 (8) In the above formula, Pos2250 is the Fe-OH wavelength value of the chlorite sample.

5. The method for calculating the mineral formation temperature based on chlorite spectrum according to claim 1, characterized in that: In S4, based on the calculation result of the formation temperature T of each chlorite sample in S3, if 200℃≦T≦300℃, the chlorite sample is formed in a medium-high temperature environment, and when 100℃<T<200℃, the chlorite sample is formed in a medium-low temperature environment.

6. The method for calculating the mineral formation temperature based on chlorite spectrum according to claim 1, characterized in that: In S4, the classification of chlorite is determined based on the range of the content of the Fe element and the Si element in each chlorite sample in S3.

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