Annular pyrite cause analysis method

Abstract

The invention discloses a cause analysis method for annulus pyrite, and relates to the technical field of mineral analys.The method comprises the following steps that a sample is cut into sheets, and an annulus pyrite area to be detected is selected; grinding the surface of the to-be-detected belt pyrite step by step, and then performing fine polishing by using a diamond suspension and a colloidal silicon dioxide polishing solution to obtain a polished section; a laser confocal microscopic Raman spectrometer is used for carrying out surface scanning on the optical sheet to collect a Raman spectrum, and then dotting scanning is carried out according to a trans-annulus interface of the annulus pyrite from the inside to the outside of the nucleus; carrying out surface scanning and dotting analysis on the same area by adopting an electronic probe; the evolution process of the annulus corpus luteum ore is analyzed by combining a Raman spectrum and an electronic probe result, and verification is carried out by combining sulfur isotope data. According to the method, element introduction interference in the sample preparation process is eliminated, electronic probe analysis and Raman spectrum combined analysis are adopted, the causes of pyrite are analyzed from multiple dimensions, and the accuracy of the analysis result is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of mineral analysis technology, and specifically to a genetic analysis method for zonal pyrite. Background Technology

[0002] Pyrite (FeS2) is the most widely distributed sulfide mineral in the Earth's crust, typically containing trace elements, particularly As, Co, and Ni, in isomorphous forms. Analysis of the genetic evolution mechanism and ore deposit genesis of pyrite has significant practical value for geological research. Summary of the Invention

[0003] To address the aforementioned technical problems, the present invention aims to provide a genetic analysis method for zonal pyrite. This method eliminates elemental interference introduced during sample preparation and employs a combination of electron probe microanalysis and Raman spectroscopy to analyze the genesis of pyrite from multiple dimensions, significantly improving the accuracy of the analytical results.

[0004] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for analyzing the genesis of zonal pyrite is provided, comprising the following steps: (1) Cut the sample into slices and select pyrite particles with rings as the pyrite to be tested by optical observation; (2) The surface of the zonal pyrite to be tested is ground step by step, then diamond suspension is used on the polishing cloth for coarse polishing, and then colloidal silica polishing liquid is used on the synthetic velvet cloth for fine polishing to obtain a zonal pyrite polishing sheet. (3) A laser confocal micro Raman spectrometer was used to perform a surface scan of the pyrite region in the zonal pyrite section, collecting samples from 300-450 cm⁻¹. -1 Raman spectra within the range, and then based on the zonal pyrite, spotting and focusing the Eg and Ag characteristic peaks across the zonal interface from the core to the outside; (4) Carbon plating was performed on the zonal pyrite sheet, and then the same area was scanned by an electron probe to analyze the distribution of Ca, Co, Fe, Ni, Si and Ti elements. Then, the contents of S, Fe, Cu, Zn and As were quantitatively analyzed at the same Raman spot positions. (5) The evolution process of the zonal luteal ore was analyzed by combining Raman spectroscopy and electron probe results, and verified by combining sulfur isotope data.

[0005] In the genetic analysis of zonal pyrite, the combined application of Raman spectroscopy and electron probe microanalysis revolves around the multi-dimensional correlation between structure and composition. The 300-450 cm⁻¹ region obtained using laser confocal microRaman spectroscopy... -1The spectral data were analyzed to extract the peak position shift (Δv) and full width at half maximum (FWHN) parameters of Eg and Ag characteristic peaks. Δv reflects the change in pyrite lattice vibration frequency, indicating the degree of crystal structure order and the difference in formation environment pressure. FWHN is positively correlated with the lattice defect density and can characterize the intensity of hydrothermal alteration after mineral formation. The cross-zone dot plotting analysis of the zonal core-boundary surface can establish the spatial distribution gradient of Raman spectral parameters and clarify the interface position and transition characteristics of structural transformation.

[0006] The structural parameters of Raman spectroscopy were coupled with the compositional data of electron probe microanalysis. Using the Cu / Zn zonation interface as a reference, the abrupt changes in Δν, FWHN, and elemental content on both sides of the interface were analyzed. When Δν > 380 cm⁻¹, the abrupt changes were observed. -1 And FWHN < 3.7cm -1 Simultaneously, when Zn is enriched and Cu is depleted, it can be identified as a low-temperature seawater mineralization zone; when Δν < 379 cm -1 And FWHN > 4.5cm -1 Furthermore, when the Cu element values ​​are high and the Zn element values ​​are low, it can be classified as a high-temperature magma core. Finally, sulfur isotope data are introduced, and the δ¹⁴ ... 34 The S-value verifies the above genetic determination result—pyrite of high-temperature magmatic origin usually has a δ-value close to that of meteorite sulfur. 34 The S value is (0±2‰), while low-temperature seawater-derived pyrite exhibits a positive δ value due to the reduction of seawater sulfate. 34 S-value shift enables a three-dimensional genetic constraint of "junction-composition-isotope".

[0007] Furthermore, in step (1), the material is cut into 10×10×5 mm pieces. 3 Standard-sized rock slices.

[0008] Furthermore, in step (2), the diamond suspension has a concentration of 15-30 wt% and a diamond particle size of 1-9 μm.

[0009] Furthermore, in step (2), a diamond suspension with a particle size of 5-9 μm is first used, and then a diamond suspension with a particle size of 1-5 μm is used for polishing.

[0010] Furthermore, in step (2), the concentration of the colloidal silica polishing slurry is 10-15 wt%, the pH is 9.5-10.5, and the particle size of the silica is 0.04-0.06 μm.

[0011] Furthermore, each step in the optical sheet preparation process involves ultrasonic cleaning with deionized water or ethanol.

[0012] Furthermore, in step (3), a 532 nm laser and a 50x LWD objective lens are used.

[0013] Furthermore, in step (3), the area scan area is 250µm×200µm in size, the dot matrix is ​​3600 points, and the single-point acquisition time is 3 seconds.

[0014] Furthermore, in step (4), the accelerating voltage of the electron probe analysis is 20-25 kV, the beam current is 20 nA, and the beam spot is 5µm.

[0015] Furthermore, in step (5), the Cu / Zn zonal interface is located based on electron probe surface scanning, and the Ag peak displacement Δν and full width at half maximum (FWHN) on both sides of the interface are extracted and analyzed. When Δν > 380 cm⁻¹ -1 And FWHN < 3.7 cm -1 When Δν < 379 cm, it is determined to be a low-temperature seawater mineralization zone; -1 And FWHN > 4.5 cm -1 At that time, it was determined to be a high-temperature magma core.

[0016] Furthermore, in step (5), the formation of zonation is analyzed based on the changes in element distribution.

[0017] The present invention has the following beneficial effects: 1. This invention abandons traditional polishing methods, using diamond suspension and silica polishing slurry for polishing. It avoids using oxides such as Al2O3, Cr2O3, and CeO2, or cotton polishing pads, as these abrasive particles can embed in softer pyrite or remain in cracks, affecting subsequent trace element analysis. This invention uses diamond suspension for accelerated polishing on a hard polishing cloth (such as canvas), quickly removing grinding scratches. Then, colloidal silica polishing slurry is used on a soft synthetic velvet cloth for chemical-mechanical polishing. Colloidal SiO2, in an alkaline environment, softens the surface through a weak chemical reaction and removes minor undulations through mechanical action, resulting in a near-perfect mirror finish. It almost completely eliminates the surface mechanical damage layer, offering extremely high flatness and zero pollution.

[0018] 2. The method of this invention uses a combination of electron probe microanalysis and Raman spectroscopy, which can analyze the genesis of pyrite from multiple dimensions such as elemental distribution, internal structure and lattice changes, and can significantly improve the accuracy of the analysis results.

[0019] 3. At the same time, the method of the present invention also optimizes the analysis process. It first performs non-destructive analysis by Raman spectroscopy and then performs electron probe analysis, so that the analysis results are not affected by the slight damage of electron probe analysis when spot analysis is performed at the same location in pyrite. Attached Figure Description

[0020] Figure 1 This is a microscopic photograph of the zonal pyrite sample from Example 1. Figure 2 This is a Raman surface scan composition diagram of the zonal pyrite in Example 1; Figure 3 This is a 2D Raman surface scan image of the zonal pyrite in Example 1; Figure 4 This is a diagram showing the qualitative distribution analysis results of sulfur (S) in zonal pyrite in Example 1. Figure 5 The figure shows the qualitative distribution analysis results of Fe element in the zonal pyrite in Example 1; Figure 6 This is a graph showing the qualitative distribution analysis results of Ca element in zonal pyrite in Example 1; Figure 7 This is a graph showing the qualitative distribution analysis results of Si element in the zonal pyrite of Example 1; Figure 8 The figure shows the qualitative distribution analysis results of Ni element in the zonal pyrite in Example 1; Figure 9 This is a diagram showing the location of the zonal pyrite in Example 1. Detailed Implementation

[0021] The principles and features of this invention are described below. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0022] Example 1 The samples were iron-rich, blocky polymetallic sulfides collected by the Chinese oceanographic research vessel "Dayang Yihao" during its 22nd oceanographic expedition in the 26°S ridge segment of the South Atlantic Ridge.

[0023] A genetic analysis method for zonal pyrite includes the following steps: (1) Cut the sample into slices and select pyrite particles with rings as the pyrite to be tested by optical observation; (2) The surface of the zonal pyrite to be tested is ground step by step. Then, on the polishing cloth, a diamond suspension with a particle size of 9 μm and a 20 wt% is used for coarse polishing. Then, a diamond suspension with a particle size of 3 μm and a 20 wt% is used for medium polishing. Finally, on the synthetic velvet cloth, a colloidal silica polishing liquid (concentration of 15 wt%, pH adjusted to 10 with sodium hydroxide, and silica particle size of 0.04 μm) is used for fine polishing to obtain a zonal pyrite sheet. (3) A laser confocal micro Raman spectrometer (HORIBA LabRAM HR Evolution, 532 nm laser, 50x LWD objective) was used to perform a surface scan (250µm×200µm, 3600 points in the array, single-point acquisition for 3 seconds) on the pyrite region in the zonal pyrite section, acquiring data from 300-450 cm⁻¹. -1 Raman spectra within the range, and then based on the zonal pyrite, spotting and focusing the Eg and Ag characteristic peaks across the zonal interface from the core to the outside; (4) Carbon plating was performed on the zonal pyrite sheet, and then an electron probe was used (accelerating voltage of 20-25 kV, beam current of 20 nA, beam spot of 5 µm) to perform surface scanning on the same area of ​​the Raman surface scan to analyze the distribution of S, Ca, Co, Fe, Ni, Si and Ti elements. Then, the contents of S, Fe, Cu, Zn and As were quantitatively analyzed at the same Raman spot positions. (5) The evolution process of the zonal luteal ore was analyzed by combining Raman spectroscopy and electron probe results, and verified by combining sulfur isotope data.

[0024] Experimental Example 1 (1) A microscopic photograph of the zonal pyrite sample in Example 1 is shown below. Figure 1 As shown in the image, the mineral core and outer layer are distinctly different, with a clear black ring at the boundary, clearly indicating two generations: Py1 and Py2. The inner ring, Py1, is characterized by higher brightness and less developed fractures, suggesting it is a mineral formed in an earlier generation. The outer layer, Py2, is darker than the inner ring, showing many dark inclusions and impurities, with more developed fractures and a denser structure.

[0025] (2) The Raman surface scan composition diagram and 2D diagram of the zonal pyrite in Example 1 are shown below. Figure 2 and Figure 3 As shown.

[0026] The results showed that Raman spectral data indicated that in the 300-450 cm⁻¹ range... -1 Within this range, the Raman peaks of pyrite are concentrated at 337-342 cm⁻¹. -1 and 373-378 cm -1 Between them. The Raman spectral peak shift data of pyrite samples from different geological locations and periods often have great similarities. The 2D figure shows that there are obvious differences in the mineralization period of zonal pyrite.

[0027] (3) The qualitative distribution analysis results of S, Fe, Ca, Si and Ni elements in the zonal pyrite in Example 1 are shown in the figure below. Figure 4-8As shown, distinct zoning can be clearly seen among the four elements Ca, Fe, S, and Si, while Ni also exhibits relatively clear zoning. Comparing this to previous electron microscope images of pyrite, it can be seen that it can be divided into two generations, Py1 and Py2, from the inside out.

[0028] (4) BSE images of zonal pyrite in Example 1 are shown below. Figure 9 As shown in the figure, the locations of the dotted test are illustrated, and the element content at each location is shown in Table 1.

[0029] Table 1. Element content at each location Element (wt%) 1 2 3 4 5 6 7 Ca La 0 0 0 0 0 0 0 S La 54.938 53.657 50.367 54.51 54.279 55.049 39.835 Mn Ka 0.234 0.211 0.012 0 0 0 0.027 Ge La 0 0.027 0 0.02 0 0.017 0 Pb Ma 0.366 0.117 0.107 0.079 0.1 0.099 0.099 Fe Ka 46.427 44.828 42.732 45.306 45.944 45.441 32.892 As La 0.218 0.161 0.164 0.225 0.206 0.217 0.175 Bi Ma 0 0 0 0 0 0 0 Co Ka 0.064 0.047 0.067 0.137 0.023 0.055 0 Ag La 0 0.014 0 0 0.016 0.022 0.014 Ni Ka 0.021 0.029 0 0 0 0 0.002 Cd La 0 0 0 0 0 0 0 Cu Ka 0.033 0.011 0 0.067 0.04 0.037 0 Sb La 0.051 0 0.007 0.026 0 0.005 0 Zn Ka 0 0 0 0.064 0.032 0 0.069 Total 102.352 99.102 93.455 100.434 100.64 100.941 73.113 Table 1 shows that, from point 1 to point 3, which forms the core of the pyrite, the contents of major elements S and Fe clearly decrease from the inside out, as do trace elements Mn, Pb, and Cu. However, starting at point 4, a sudden change occurs between the trace elements and the major elements: Fe and S increase dramatically, while As, Co, and Cu also increase. A higher Cu content in pyrite usually indicates higher formation temperatures, while a higher Zn content usually indicates lower formation temperatures. Electron probe microanalysis data shows that the internal formation conditions were high-temperature hydrothermal, while the newly formed pyrite from different external phases occurred in a low-temperature hydrothermal environment.

[0030] 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 or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for genetic analysis of zonal pyrite, characterized in that, Includes the following steps: (1) Cut the sample into slices and select pyrite particles with rings as the pyrite to be tested by optical observation; (2) The surface of the zonal pyrite to be tested is ground step by step, then diamond suspension is used on the polishing cloth for coarse polishing, and then colloidal silica polishing liquid is used on the synthetic velvet cloth for fine polishing to obtain a zonal pyrite polishing sheet. (3) A laser confocal micro Raman spectrometer was used to perform a surface scan of the pyrite region in the zonal pyrite slide, collecting samples from 300-450 cm⁻¹. -1 Raman spectra within the range, and then based on the zonal pyrite, spotting and focusing the Eg and Ag characteristic peaks across the zonal interface from the core to the outside; (4) The circumferential pyrite sheet is carbonized, and then the same area is scanned by an electron probe to analyze the distribution of Ca, Co, Fe, Ni, Si and Ti elements. Then, the contents of S, Fe, Cu, Zn and As are quantitatively analyzed at the same Raman spot positions. (5) The evolution process of the zonal luteal ore was analyzed by combining Raman spectroscopy and electron probe results, and verified by combining sulfur isotope data.

2. The genetic analysis method for zonal pyrite as described in claim 1, characterized in that, In step (1), the material is cut into 10×10×5 mm pieces. 3 Standard-sized rock slices.

3. The genetic analysis method for zonal pyrite as described in claim 1, characterized in that, In step (2), the diamond suspension has a concentration of 15-30 wt% and a diamond particle size of 1-9 μm.

4. The genetic analysis method for zonal pyrite as described in claim 1, characterized in that, In step (2), a diamond suspension with a particle size of 5-9 μm is first used, and then a diamond suspension with a particle size of 1-5 μm is used for polishing.

5. The genetic analysis method for zonal pyrite as described in claim 1, characterized in that, In step (2), the concentration of the colloidal silica polishing slurry is 10-15 wt%, the pH is 9.5-10.5, and the particle size of the silica is 0.04-0.06 μm.

6. The genetic analysis method for zonal pyrite as described in claim 1, characterized in that, In step (3), a 532nm laser and a 50x LWD objective lens are used.

7. The genetic analysis method for zonal pyrite as described in claim 1, characterized in that, In step (3), the area scan area is 250µm×200µm in size, the dot matrix is ​​3600 points, and the single point acquisition takes 3 seconds.

8. The genetic analysis method for zonal pyrite as described in claim 1, characterized in that, In step (4), the accelerating voltage of the electron probe analysis is 20-25 kV, the beam current is 20 nA, and the beam spot is 5 µm.

9. The genetic analysis method for zonal pyrite as described in claim 1, characterized in that, In step (5), the Cu / Zn zonal interface is located based on electron probe surface scanning. The Ag peak displacement Δν and the full width at half maximum (FWHN) on both sides of the interface are extracted and analyzed. When Δν > 380 cm⁻¹ -1 And FWHN < 3.7 cm -1 When Δν < 379 cm, it is determined to be a low-temperature seawater mineralization zone; -1 And FWHN > 4.5 cm -1 At that time, it was determined to be a high-temperature magma core.

10. The genetic analysis method for zonal pyrite as described in claim 1, characterized in that, In step (5), the formation of zonation is analyzed based on the changes in element distribution.

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