A method for quickly determining the type of tin deposit using cassiterite

Abstract

The present invention discloses a method for rapidly determining the type of a tin deposit using cassiterite. The method comprises collecting cassiterite markers from the deposit, obtaining cathodoluminescence image characteristics, chronological characteristics from U-Pb dating, trace element characteristics, and Sn isotope characteristics of the markers, and determining the type of the tin deposit based on these characteristics. This method can directly invert the mineral geochemical characteristics of cassiterite to determine the deposit type, eliminating issues such as external interference and ambiguity in elemental analysis, and significantly improving the efficiency of mineral exploration.

Description

Technical Field

[0001] The present invention relates to the technical field of prospecting and exploration of mineral deposits, and in particular to a cassiterite mineralogy prospecting method for accurately distinguishing the types of tin polymetallic deposits. Background Art

[0002] Mineral exploration refers to a method of conducting geological, technical, and economic evaluations by effectively identifying and evaluating the occurrence and reserves of ore bodies by studying the geological conditions of mineral formation and distribution, the occurrence patterns of ore deposits, and the characteristics of ore body changes. Currently, the geochemical method is the first choice for prospecting and exploration of mineral deposits. This method analyzes the content of elements related to mineralization through rock geochemical measurements, soil (rock debris, gully system, water chemistry, deep-penetrating ground gas, etc.) geochemical measurements, and stream sediment measurements. It then defines the level and range of geochemical anomalies and conducts drilling verification. This method requires a lot of manpower and funds, and it is difficult to obtain direct ore deposit information, such as ore deposit type and burial depth. There are also problems such as multi-solution and interference from surface contamination, which make its prospecting and exploration results poor. Summary of the Invention

[0003] In order to solve the problems in the prior art, the present invention provides a prospecting method for accurately identifying the type of tin polymetallic deposits through cassiterite, which can directly invert the mineral geochemical characteristics of cassiterite to obtain information such as the type of the deposit, eliminating problems such as external interference and ambiguity in elemental analysis.

[0004] The technical solutions of the present invention are as follows:

[0005] A method for quickly determining the type of tin deposit using cassiterite, characterized by comprising the following steps:

[0006] S1: Collect cassiterite ore samples from the tin deposit and sort them, and randomly select at least 100 cassiterites as markers;

[0007] S2: performing target preparation and cathode luminescence photography on the marking product to obtain cathode luminescence image characteristics of the marking product;

[0008] S3: performing in situ U-Pb dating analysis on the marker to obtain the chronological characteristics of the marker;

[0009] S4: performing LA-ICP-MS trace element analysis on the marker product to obtain the trace element characteristics of the marker product;

[0010] S5: performing Sn isotope analysis on the marker to obtain the Sn isotope characteristics of the marker;

[0011] S6: Determine the type of the tin deposit based on the cathode luminescence image characteristics, chronological characteristics, trace element characteristics and Sn isotope characteristics of the marker.

[0012] In the above scheme, the trace elements refer to elements with a content of less than 2%, such as Nb, Zr, Hf, Ta, U, W, REE (rare earth elements), etc.

[0013] in,

[0014] The cathodoluminescence image features include: the colors presented at different positions in the image, whether oscillation rings appear in the image, and whether other hydrothermal minerals and / or fluid inclusions appear in the image;

[0015] The geochronological characteristics include: the age of the lower intersection of the marker in the Tera-Wasserburg Concordia diagram obtained based on the U-Pb dating;

[0016] The trace element characteristics include one or more of the following characteristics: type, content, and content ratio of trace elements;

[0017] The Sn isotope characteristics include: δ 120 / 116 Sn and δ 124 / 116 Sn value, i.e. δ 120 / 116 Sn NIST3161a and δ 124 / 116 Sn NIST3161a value.

[0018] According to some specific embodiments of the present invention, the trace elements include: 29 4. 31 P. 43 Ca, 49 Ti, 55 Mn, 57 Fe, 89 Y. 91 Zr, 93 Nb, 118 Sn, 139 La, 140 Ce, 141 Pr, 146 Nd, 147 Sm, 153 Eu, 157 Gd, 159 Tb, 163 Dy, 165 Ho, 166 Second,169 Tm, 172 Yb, 175 Lu, 178 Hf, 181 She 182 W. 208 Pb, 232 Th, 238 U.

[0019] According to some specific embodiments of the present invention, step S2 specifically includes: embedding the marker in epoxy resin, polishing it, and performing cathode luminescence photography (CL) using a high vacuum scanning electron microscope equipped with a cathode luminescence probe to obtain a cathode luminescence image of cassiterite, wherein the acceleration voltage during the CL image shooting process is 20-30 kV, and the shooting distance is 9.5-10.5 mm.

[0020] According to some specific embodiments of the present invention, step S3 specifically includes: using a laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) to perform the U-Pb dating analysis; the beam spot diameter used in the analysis is 44 μm, the ablation frequency is 5 Hz, and the energy density is 5 J / cm 2 Zircon 91500 was used as an external standard for Pb / U fractionation and mass discrimination correction, and cassiterite AY-4 was used as a monitoring standard. Two 91500 standards and one AY-4 standard were analyzed every 5-6 sample points. A 20-second gas blank and a 35-50-second signal interval were collected for data processing.

[0021] According to some specific embodiments of the present invention, step S4 specifically includes: using a laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) to perform the trace element analysis; in the analysis, areas without cracks and inclusions in the cathode luminescence image are circled, and particles are ablated in a point manner. The beam spot diameter used is 44 μm, the frequency is 5 Hz, helium is used as the carrier gas, argon is used as the compensation gas, the sample signal acquisition time is 35-50 s, the blank background value acquisition time is 20 s, and the glass standard material NIST610 is used as an external standard to calibrate the trace element content and perform offline processing of the analysis data.

[0022] According to some specific embodiments of the present invention, step S5 specifically includes: performing the Sn isotope analysis by a multi-collector plasma mass spectrometer (MC-ICP-MS); the step includes: pulverizing and degassing the weighed marker, then mixing it with KCN, and heating it at 850°C to obtain reduced tin metal beads; dissolving and purifying the tin metal beads with hydrochloric acid, separating tin isotopes of different mass numbers using a micro-concentric borosilicate glass atomizer, and then using an Sb doping solution (high-purity ICP-MS Sb standard material 10 2-3; 10 μg / ml in 2% nitric acid and trace HF) to correct the mass deviation of Sn isotope analysis, and the corrected value was then calibrated with the Sn isotope standard NISTSRM3161a.

[0023] According to some specific embodiments of the present invention, step S6 includes data processing of the data of the chronological characteristics, trace element characteristics and Sn isotope characteristics, obtaining the U-Pb age concordance diagram and age weighted average of the marker through the data processing, obtaining the content of the trace elements and the principal component analysis results, and δ 120 / 116 Sn NIST3161a and δ 124 / 116 Sn NIST3161a isotope ratio.

[0024] According to some specific embodiments of the present invention, in step S6, the determining includes:

[0025] When the cathode luminescence images of the contemporaneous markers of the said markers are clean and transparent, without fluid inclusions and other obvious hydrothermal minerals; and more than 50% of the markers in all 100 markers have trace elements of Nb>1000ppm, Ta>100ppm, Zr>50ppm, Hf>50ppm; and more than 50% of the markers in all 100 markers have tin isotope ratios δ 124 / 116 Sn NIST3161a >-0.2, δ 120 / 116 Sn NIST3161a When >-0.1, the deposit is a granite-type tin deposit;

[0026] When the cathode luminescence images of the contemporaneous markers of the said markers are clean and transparent, without fluid inclusions and obvious other hydrothermal minerals; and more than 50% of the markers in all 100 markers have trace elements of Nb>5000ppm, Ta>100ppm, Zr>100ppm, Hf>20ppm; and more than 50% of the markers in all 100 markers have tin isotope ratios δ 124 / 116 Sn NIST3161a >-0.2, δ 120 / 116 Sn NIST3161a When >-0.1, the deposit is a greisen-type tin deposit;

[0027] When the cathode luminescence images of the contemporaneous markers of the said markers are clean and transparent, without fluid inclusions and other obvious hydrothermal minerals; and more than 50% of the markers in all 100 markers have trace elements of Nb>500ppm, Ta<100ppm, Zr>100ppm, Hf<20ppm; and more than 50% of the markers in all 100 markers have tin isotope ratios δ 124 / 116 Sn NIST3161a <-1.0、δ 120 / 116 Sn NIST3161a When <-0.5, the deposit is a skarn-type tin deposit;

[0028] When the cathode luminescence images of the contemporaneous markers of the said markers are clean and transparent, without fluid inclusions and other obvious hydrothermal minerals; and more than 50% of the markers in all 100 markers have trace elements of Nb < 100ppm, Ta < 10ppm, Zr < 10ppm, Hf < 1ppm; and more than 50% of the markers in all 100 markers have tin isotope ratios δ 124 / 116 Sn NIST3161a <-4.0、δ 120 / 116 Sn NIST3161a When <-2.0, the deposit is a quartz vein type tin ore;

[0029] The contemporary markers refer to markers whose age difference after U-Pb dating is less than 10%.

[0030] According to some specific embodiments of the present invention, the detection position of the marker in the U-Pb dating is a position where there are no obvious mineral or fluid inclusions between the center and the edge of the marker.

[0031] Cassiterite, the primary ore mineral in tin polymetallic deposits, has a crystallization and precipitation process closely related to the magma-hydrothermal system. Cassiterite also exhibits strong resistance to physical and chemical weathering, and its chemical composition is highly sensitive to the crystallization environment and its variations. Many elements can enter its crystal lattice through substitution processes. Trace elements such as Sc, Ti, Nb, Ta, Fe, Mn, W, In, U, Pb, and REEs can record the geochemical characteristics of the ore-forming fluids, playing an important role in understanding the genesis of tin deposits and identifying the types of tin polymetallic deposits. The present invention can establish a mineral exploration method for rapidly determining the type of tin deposits based on cathodoluminescence images, age spectrum, trace elements, and tin isotopes of tin ore, which has important practical significance for accurately inverting deposit types.

[0032] The present invention further has the following beneficial effects:

[0033] (1) The present invention can obtain accurate judgment results on the type of tin deposit by directly obtaining mineralogical information, eliminating external interference and multiple solutions of elemental analysis;

[0034] (2) The present invention can quantitatively obtain the crystallization temperature information of cassiterite through chemical element characteristics;

[0035] (3) The present invention can directly invert the mineral geochemical characteristics of cassiterite to obtain deposit type information, eliminating the interference of other factors. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 These are typical cathode luminescence images of cassiterite from different types of deposits in Examples 1-3 of the present invention.

[0037] Figure 2 This is a diagram showing the U-Pb dating results of cassiterite from different types of deposits in Example 1 of the present invention.

[0038] Figure 3 This is a relationship diagram of the (Nb+Ta) / (Fe+Mn) ratio of cassiterite in different types of deposits in Example 1 of the present invention.

[0039] Figure 4 This is a relationship diagram of the Fe / W ratio of cassiterite in different types of deposits in Example 1 of the present invention.

[0040] Figure 5 This is a relationship diagram of the Nb / Ta ratios of cassiterite from different types of deposits in Example 2 of the present invention.

[0041] Figure 6 This is a relationship diagram of the Zr / Hf ratios of cassiterite from different types of deposits in Example 2 of the present invention.

[0042] Figure 7 This is a relationship diagram of the (Zr / Hf) / (Nb / Ta) ratios of cassiterite in different types of deposits in Example 2 of the present invention.

[0043] Figure 8 This is a relationship diagram of the W / Fe ratios of cassiterite in different types of deposits in Example 3 of the present invention.

[0044] Figure 9 This is a relationship diagram of the Fe / (Nb+Ta) ratio of cassiterite in different types of deposits in Example 3 of the present invention.

[0045] Figure 10 This is the PCA diagram of trace elements of cassiterite in different types of deposits in Example 3 of the present invention.

[0046] Figure 11 This is a tin isotope characteristic diagram of cassiterite of different types of deposits in Example 4 of the present invention. DETAILED DESCRIPTION

[0047] The present invention is described in detail below with reference to the embodiments and accompanying drawings. However, it should be understood that the embodiments and accompanying drawings are merely exemplary descriptions of the present invention and do not constitute any limitation on the scope of protection of the present invention. All reasonable variations and combinations within the scope of the inventive concept of the present invention fall within the scope of protection of the present invention.

[0048] The samples collected in the embodiments of the present invention mainly come from tin polymetallic deposits of different types and origins in the Nanling region. The ore types are quartz vein ore of the Dengfuxian deposit, greisen ore of the Dayishan deposit, skarn ore of the Shizhuyuan deposit, granite ore of the Xianghualing deposit, and greisen ore of the Jiuyishan deposit.

[0049] The following examples select the markers through the following process:

[0050] (1) Crushing the ore;

[0051] (2) The crushed ore is roughly washed to screen out lighter minerals and retain heavy minerals. After rough washing, the sample is dried by controlling the baking temperature to obtain the rough washed minerals;

[0052] (3) Repeated magnetic separation of the rough-washed minerals using magnets and electromagnetic instruments to screen out the magnetic minerals;

[0053] (4) repeatedly fine-panning the coarse-panned minerals remaining after screening to screen out heavy fine tailings;

[0054] (5) The remaining minerals after screening are sorted under a binocular microscope, and at least 100 cassiterites are randomly selected as markers.

[0055] In the following examples, a high vacuum scanning electron microscope JSM-IT300 equipped with a Delmicsparc cathodoluminescence probe was used to perform cathodoluminescence photography (CL) of cassiterite to obtain cathodoluminescence images of cassiterite. During the CL image shooting process, the operating voltage was 0.5-30 kV, the filament emission current was 72 μA, the acceleration voltage was generally 20-30 kV, and the shooting distance was 9.5-10.5 mm.

[0056] In the following examples, cassiterite U-Pb dating was performed using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The analysis used a beam spot diameter of 44 μm, an ablation frequency of 5 Hz, and an energy density of 5 J / cm 2Zircon 91500 was used as an external standard for Pb / U fractionation and mass discrimination correction, cassiterite AY-4 was used as a monitoring standard, two 91500 standards and one AY-4 standard were analyzed every 5-6 sample points, a 20-second gas blank was collected, and a 35-50-second signal interval was used for data processing. The U-Pb age concordance diagram and age-weighted average calculation were completed using Isoplot / Ex_ver3.

[0057] The trace element analysis of cassiterite in the following examples was carried out using a laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS). During the analysis, areas without cracks and inclusions in the cathodoluminescence image were circled, and the particles were ablated using a point method. The beam spot diameter used was 44 μm, the frequency was 5 Hz, helium was used as the carrier gas, argon was used as the compensation gas, the sample signal acquisition time was 35-50 s, and the blank background value acquisition time was 20 s. The glass standard material NIST610 was used as an external standard for trace element content correction, and the analytical data was processed offline to obtain the various trace element contents of cassiterite. The trace elements include: 29 4. 31 P. 43 Ca, 49 Ti, 55 Mn, 57 Fe, 89 Y. 91 Zr, 93 Nb, 118 Sn, 139 La, 140 Ce, 141 Pr, 146 Nd, 147 Sm, 153 Eu, 157 Gd, 159 Tb, 163 Dy, 165 Ho, 166 Second, 169 Tm, 172 Yb, 175 Lu, 178 Hf, 181 She 182 W. 208 Pb, 232 Th, 238 U.

[0058] The tin isotope analysis of cassiterite in the following examples was performed by multi-collector plasma mass spectrometry (MC-ICP-MS); the method included: pulverizing and degassing the weighed marker, mixing it with KCN, and heating it at 850°C to obtain reduced tin metal beads; dissolving and purifying the tin metal beads with hydrochloric acid, separating tin isotopes of different mass numbers using a micro-concentric borosilicate glass atomizer, and then using an Sb doping solution (high-purity ICP-MS Sb standard material 10 2-3 ; 10 μg / ml, in 2% nitric acid and trace HF) to correct the mass deviation of Sn isotope analysis, and the corrected value was then calibrated with the Sn isotope standard NISTSRM3161a to obtain the δ 120 / 116 Sn NIST3161a and δ 120 / 116 Sn NIST3161a isotope ratio.

[0059] In the following examples, the detection position of U-Pb dating is the position between the center and the edge of cassiterite where there is no obvious mineral or fluid inclusion, such as the Figure 1 shown.

[0060] Example 1

[0061] Using cassiterite to quickly determine the age of tin mineralization:

[0062] Tin ore samples (5 kg) were collected from each of the Dengfuxian, Dayishan, Shizhuyuan, Xianghualing, and Jiuyishan deposits. Cassiterite (more than 100 grains) were sorted out and embedded in epoxy resin. One side was polished to obtain test samples.

[0063] Cathodoluminescence (CL) photography was performed on the test sample to obtain a detailed CL image of each cassiterite grain. Figure 1 A typical CL image of cassiterite is shown. In the CL image, the cassiterite appears black to off-white, with a clean surface and no obvious other hydrothermal minerals or fluid inclusions. Some areas exhibit distinct internal oscillation zoning.

[0064] U-Pb dating analysis of cassiterite from these five deposits showed that the cassiterite from the Dengfuxian deposit had a lower intersection age of 142.0±17.1Ma (MSWD=1.40) in the Tera-Wasserburg Concordia diagram. Figure 2 a). The cassiterite in the Dayishan deposit has a lower intersection age of 154.7±3.0Ma (MSWD=0.96) in the Tera-Wasserburg Concordia diagram ( Figure 2b) The cassiterite in the Shizhuyuan deposit has a lower intersection age of 154.9±2.1Ma (MSWD=1.50) in the Tera-Wasserburg Concordia diagram. Figure 2 c). The cassiterite in the Xianghualing deposit has a lower intersection age of 155.4±4.8Ma (MSWD=0.43) in the Tera-Wasserburg Concordia diagram ( Figure 2 d). The cassiterite in the Jiuyishan deposit has a lower intersection age of 152.0±5.8Ma (MSWD=1.50) in the Tera-Wasserburg Concordia diagram ( Figure 2 e). The inventors believe that the U-Pb dating results of cassiterite from the five deposits are consistent, within the margin of error, with the dating results of magmatic zircon, molybdenite, garnet, and other minerals in the corresponding regions. The large age deviation of the Dengfuxian cassiterite is due to the fact that the cassiterite sample is relatively young, has a low U content, a low radiogenic Pb content, and a high ordinary lead content, resulting in a large error in the cassiterite U-Pb dating.

[0065] LA-ICP-MS in-situ trace element analysis was performed on cassiterite from five deposits. Offline processing of analytical data included sample and blank signal selection, instrument sensitivity drift correction, and element content calculation using the ICPMSDataCal software. Origin plotted the trace element in-situ laser ablation test results of cassiterite to show the relationship between the ratios of (Fe+Mn) / (Nb+Ta) and W / Fe, as shown in the attached figure. Figure 3 、 4 As shown, all five deposits are granite-related tin deposits and the sources of cassiterite in the deposits are directly related to the granite, indicating that the U-Pb dating results of cassiterite can limit the formation age of the tin deposits and the intrusion age of the mineralizing granite.

[0066] In summary, the inventors believe that the U-Pb dating results of cassiterite can limit the formation age of the deposit with high accuracy.

[0067] Example 2

[0068] Using the trace element characteristics of cassiterite to quickly determine the type of tin deposit:

[0069] Tin ore samples (5 kg) were collected from each of the Dengfuxian, Dayishan, Shizhuyuan, Xianghualing, and Jiuyishan deposits. Cassiterite (more than 100 grains) were sorted out and embedded in epoxy resin. One side was polished to obtain test samples.

[0070] Cathodoluminescence (CL) photography was performed on the test sample to obtain a detailed CL image of each cassiterite grain. Figure 1A typical CL image of cassiterite is shown. In the CL image, the cassiterite appears black to off-white, with a clean surface and no obvious other hydrothermal minerals or fluid inclusions. Some areas exhibit distinct internal oscillation zoning.

[0071] LA-ICP-MS in-situ trace element analysis was performed on cassiterite from five deposits. Offline processing of the analytical data included sample and blank signal selection, instrument sensitivity drift correction, and element content calculation using the software ICPMSDataCal. Origin plotted the trace element in-situ laser ablation test results of cassiterite to show the relationship between the ratios of Nb / Ta, Zr / Hf, and (Zr / Hf) / (Nb / Ta), as shown in the attached figure. Figure 5 、 6 7 (To avoid the influence of outliers, all data below represent the 16th to 84th percentiles). The element contents (ratios) of cassiterite from the Dengfuxian deposit are: Nb (7.3-278.2 ppm), Ta (0.2-4.4 ppm), Zr (3.8-14.0 ppm), Hf (0.1-1.0 ppm), Fe (243.6-5091.2 ppm), and W (51.6-18799.7 ppm). The Nb / Ta ratio, Zr / Hf ratio, and (Zr / Hf) / (Nb / Ta) ratio of cassiterite from the Dengfuxian deposit indicate a low crystallization temperature.

[0072] The element contents (ratios) of cassiterite from the Dayishan deposit are: Nb (1582.3-5513.0 ppm), Ta (189.1-1019.1 ppm), Zr (101.3-283.3 ppm), Hf (12.7-45.5 ppm), Fe (651.0-3210.9 ppm), and W (234.4-4906.4 ppm). The Nb / Ta, Zr / Hf, and (Zr / Hf) / (Nb / Ta) ratios of cassiterite from the Dayishan deposit indicate a high crystallization temperature.

[0073] The elemental contents (ratios) of cassiterite from the Shizhuyuan deposit are: Nb (163.4-549.8 ppm), Ta (44.9-122.5 ppm), Zr (127.0-343.7 ppm), Hf (6.2-26.4 ppm), Fe (152.0-698.1 ppm), and W (74.6-1396.8 ppm). The Nb / Ta, Zr / Hf, and (Zr / Hf) / (Nb / Ta) ratios of the cassiterite from the Shizhuyuan deposit indicate a medium-to-high temperature crystallization temperature.

[0074] The elemental contents (ratios) of cassiterite from the Xianghualing deposit are: Nb (101.8-1367.6 ppm), Ta (92.0-1763.0 ppm), Zr (57.2-206.9 ppm), Hf (13.9-48.4 ppm), Fe (201.5-1465.0 ppm), and W (380.5-3078.3 ppm). The Nb / Ta, Zr / Hf, and (Zr / Hf) / (Nb / Ta) ratios of the Xianghualing cassiterite indicate a high crystallization temperature.

[0075] The elemental contents (ratios) of cassiterite from the Jiuyishan deposit are: Nb (315.1-9789.4 ppm), Ta (15.5-3788.9 ppm), Zr (37.1-498.1 ppm), Hf (2.1-74.4 ppm), Fe (572.4-4259.5 ppm), and W (108.4-3140.3 ppm). The Nb / Ta, Zr / Hf, and (Zr / Hf) / (Nb / Ta) ratios of the Jiuyishan cassiterite indicate a high crystallization temperature.

[0076] According to the above results, this example judges that the Dengfuxian ore is a quartz vein type, the Dayishan ore is a greisen type, the Shizhuyuan ore is a skarn type, the Xianghualing ore is a granite type, and the Jiuyishan ore is a greisen type. There are obvious differences in the trace element content of cassiterite of different mineralization types, granite-type cassiterite → greisen-type cassiterite → skarn-type cassiterite → quartz vein-type cassiterite. The Nb, Ta, Zr, Hf and cassiterite crystallization temperature of cassiterite show a significant downward trend, which is of great reference significance for judging the type and characteristics of tin ore.

[0077] Example 3

[0078] Using cassiterite to determine the mechanism of trace element substitution:

[0079] Tin ore samples (5 kg) were collected from each of the Dengfuxian, Dayishan, Shizhuyuan, Xianghualing, and Jiuyishan deposits. Cassiterite (more than 100 grains) were sorted out and embedded in epoxy resin. One side was polished to obtain test samples.

[0080] Cathodoluminescence (CL) photography was performed on the test sample to obtain a detailed CL image of each cassiterite grain. Figure 1 A typical CL image of cassiterite is shown. In the CL image, the cassiterite appears black to off-white, with a clean surface and no obvious other hydrothermal minerals or fluid inclusions. Some areas exhibit distinct internal oscillation zoning.

[0081] LA-ICP-MS trace element in situ laser ablation testing was performed on cassiterite from five deposits. Offline processing of analytical data included sample and blank signal selection, instrument sensitivity drift correction, and element content calculation using the software ICPMSDataCal. Origin was used to perform the relationship between the Fe / W and Fe / (Nb+Ta) ratios of cassiterite trace elements and principal component analysis (PCA) of Nb, Ta, Zr, Hf, Fe, Mn, and W, as shown in the attached figure. Figure 8 、 9 As shown in Figures 10 and 10, the W-Fe ratios in cassiterite from five deposits exhibit positive correlations. The Fe-(Nb+Ta) ratios in cassiterite from the Dayishan, Shizhuyuan, Xianghualing, and Jiuyishan deposits exhibit positive correlations, while the Fe-(Nb+Ta) ratios in cassiterite from the Dengfuxian deposit exhibit no correlation. PCA results reveal coupling between trace elements in cassiterite, with the first two components accounting for 62.0% of the total variance (36.4% for PC1 and 25.6% for PC2), indicating that dimensionality reduction is feasible. The primary element loadings are Nb, Ta, Zr, and Hf in PC1, and Fe, Mn, and W in PC2. In the PCA plots, vector angles less than 90° indicate positive correlations between element pairs, such as Fe+Mn and Nb+Ta (r=+35.20°), W and Fe (r=+67.54°), and Nb+Ta and Fe (r=+22.56°).

[0082] Based on the above results, this example confirms that the trace element substitution mechanism of granite-type cassiterite, greisen-type cassiterite, and skarn-type cassiterite is: (Fe, Mn) 2+ +2(Nb,Ta) 5+ =3Sn 4+ 、W 6+ +2Fe 3+ =3Sn 4+ and Fe 3+ +(Nb,Ta) 5+ =2Sn 4+ The main substitution mechanism of trace elements in the quartz vein cassiterite lattice is: W 6+ +2Fe 3+ =3Sn 4+ .

[0083] Example 4

[0084] Using cassiterite tin isotopes to determine the type of tin deposits:

[0085] Tin ore samples (5 kg) were collected from each of the Dengfuxian, Dayishan, Shizhuyuan, and Xianghualing deposits. Cassiterite (>50 mg) was separated and subjected to Sn isotope analysis using a multi-collector plasma mass spectrometer (MC-ICP-MS). The analysis included: pulverizing and degassing the weighed marker, mixing it with KCN, and heating it at 850°C to obtain reduced tin metal beads; dissolving and purifying the tin metal beads with hydrochloric acid, separating tin isotopes of different mass numbers using a micro-concentric borosilicate glass atomizer, and then quantifying the tin isotopes with a Sb-doped solution (high-purity ICP-MS Sb standard material 10 2-3 ; 10 μg / ml, in 2% nitric acid and trace HF) to correct the mass deviation of Sn isotope analysis, and the corrected value was then calibrated with the NIST3161aSn standard to obtain δ 124 / 116 Sn NIST3161a and δ 120 / 116 Sn NIST3161a As a result, the δ 124 / 116 Sn NIST3161a is -4.29 and -4.19, δ 120 / 116 Sn NIST3161a The δ 124 / 116 Sn NIST3161a is -0.18, δ 120 / 116 Sn NIST3161a The δ 124 / 116 Sn NIST3161a are -1.36 and -4.19, δ 120 / 116 Sn NIST3161a The δ 124 / 116 Sn NIST3161a is -0.16, δ 120 / 116 Sn NIST3161a It is -0.06.

[0086] Origin was used to analyze the cassiterite (δ 120 / 116 Sn NIST3161a ) / (δ 124 / 116 Sn NIST3161a ), as attached Figure 11As shown in the figure, it can be seen that the tin isotopes of cassiterite of different mineralization types are significantly different and satisfy the linear relationship: Y = 1.9343x-0.0321 (R 2 =0.9998).

[0087] According to the above results, this example judges that the Dengfuxian ore is a quartz vein type, the Dayishan ore is a greisen type, the Shizhuyuan ore is a skarn type, and the Xianghualing ore is a granite type. There are obvious differences in the tin isotopes of cassiterite of different mineralization types, granite-type cassiterite → greisen-type cassiterite → skarn-type cassiterite → quartz vein type. The heavy tin isotope of cassiterite shows a significant downward trend, which is of great reference significance for judging the type and characteristics of tin ore.

[0088] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions that fall within the scope of protection of the present invention are within the scope of protection of the present invention. It should be noted that improvements and modifications that can be made by a person skilled in the art without departing from the principles of the present invention are also considered to be within the scope of protection of the present invention.

Claims

1. A method for quickly determining the type of tin deposit using cassiterite, characterized in that: The following steps are involved: S1: Collect cassiterite ore samples from the tin deposit and sort them, and randomly select at least 100 cassiterites as markers; S2: performing target preparation and cathode luminescence photography on the marking product to obtain cathode luminescence image characteristics of the marking product; S3: performing in situ U-Pb dating analysis on the marker to obtain the chronological characteristics of the marker; S4: performing LA-ICP-MS trace element analysis on the marker product to obtain the trace element characteristics of the marker product; S5: performing Sn isotope analysis on the marker to obtain the Sn isotope characteristics of the marker; S6: Determine the type of the tin deposit based on the cathodoluminescence image characteristics, chronological characteristics, trace element characteristics, and Sn isotope characteristics of the marker; in, The cathodoluminescence image features include: the colors presented at different positions in the image, whether oscillation rings appear in the image, and whether other hydrothermal minerals and / or fluid inclusions appear in the image; The geochronological characteristics include: the age of the lower intersection of the marker in the Tera-Wasserburg Concordia diagram obtained based on the U-Pb dating; The trace element characteristics include one or more of the following characteristics: type, content, and content ratio of trace elements; The Sn isotope characteristics include: δ 120 / 116 Sn and δ 124 / 116 The isotope ratio of Sn, δ 120 / 116 Sn NIST3161a and δ 124 / 116 Sn NIST3161a value.

2. The method according to claim 1, characterized in that The trace elements include: 29 4. 31 P. 43 Ca, 49 Ti, 55 Mn, 57 Fe, 89 Y. 91 Zr, 93 Nb, 118 Sn, 139 La, 140 Ce, 141 Pr, 146 Nd, 147 Sm, 153 Eu, 157 Gd, 159 Tb, 163 Dy, 165 Ho, 166 Second, 169 Tm, 172 Yb, 175 Lu, 178 Hf, 181 She 182 W. 208 Pb, 232 Th, 238 One or more of U.

3. The method according to claim 1, characterized in that The step S2 specifically includes: embedding the marker in epoxy resin, polishing it, and then performing cathode luminescence photography using a high vacuum scanning electron microscope equipped with a cathode luminescence probe to obtain a cathode luminescence image of the cassiterite. The acceleration voltage during the cathode luminescence image shooting is 20-30 kilovolts, and the shooting distance is 9.5-10.5 mm.

4. The method according to claim 1, wherein The step S3 specifically includes: using a laser ablation inductively coupled plasma mass spectrometer to perform the U-Pb dating analysis; the beam spot diameter used in the analysis is 44 μm, the ablation frequency is 5 Hz, and the energy density is 5 J / cm 2 Zircon 91500 was used as an external standard for Pb / U fractionation and mass discrimination correction, and cassiterite AY-4 was used as a monitoring standard. Two 91500 standards and one AY-4 standard were analyzed every 5-6 sample points. A 20-second gas blank and a 35-50-second signal interval were collected for data processing.

5. The method according to claim 1, wherein The step S4 specifically includes: using a laser ablation inductively coupled plasma mass spectrometer to perform the trace element analysis; during the analysis, areas without cracks and inclusions in the cathode luminescence image are circled, and particles are ablated in a point manner. The beam spot diameter used is 44 μm, the frequency is 5 Hz, helium is used as the carrier gas, argon is used as the compensation gas, the sample signal acquisition time is 35-50 seconds, the blank background value acquisition time is 20 seconds, the glass standard material NIST610 is used as an external standard to calibrate the trace element content, and the analysis data is processed offline.

6. The method according to claim 1, characterized in that The step S5 specifically includes: performing the Sn isotope analysis by a multi-collector plasma mass spectrometer; which includes: pulverizing and degassing the weighed marker, then mixing it with KCN, and heating it at 850° C. to obtain reduced tin metal beads; dissolving and purifying the tin metal beads with hydrochloric acid, separating tin isotopes of different mass numbers using a micro-concentric borosilicate glass atomizer, and then correcting the mass deviation of the Sn isotope analysis with an Sb-doped solution, and then calibrating the corrected value with the standard of the Sn isotope standard NIST SRM3161a.

7. The method according to claim 1, characterized in that The step S6 includes data processing of the data of the chronological characteristics, trace element characteristics and Sn isotope characteristics, obtaining the U-Pb age concordance diagram and age weighted average of the marker through the data processing, obtaining the content of the trace elements and the principal component analysis results, and δ 120 / 116 Sn NIST3161a and δ 124 / 116 Sn NIST3161a isotope ratio.

8. The method according to claim 1, characterized in that In step S6, the determining includes: When the cathode luminescence images of the contemporaneous markers of the said markers are clean and transparent, without fluid inclusions and other obvious hydrothermal minerals; and more than 50% of the markers in all 100 markers have trace elements of Nb>1000ppm, Ta>100ppm, Zr>50ppm, Hf>50ppm; and more than 50% of the markers in all 100 markers have tin isotope ratios δ 124 / 116 Sn NIST3161a >-0.2, δ 120 / 116 Sn NIST3161a When >-0.1, the deposit is a granite-type tin deposit; When the cathode luminescence images of the contemporaneous markers of the said markers are clean and transparent, without fluid inclusions and obvious other hydrothermal minerals; and more than 50% of the markers in all 100 markers have trace elements of Nb>5000ppm, Ta>100ppm, Zr>100ppm, Hf>20ppm; and more than 50% of the markers in all 100 markers have tin isotope ratios δ 124 / 116 Sn NIST3161a >-0.2, δ 120 / 116 Sn NIST3161a When >-0.1, the deposit is a greisen-type tin deposit; When the cathode luminescence images of the contemporaneous markers of the said markers are clean and transparent, without fluid inclusions and other obvious hydrothermal minerals; and more than 50% of the markers in all 100 markers have trace elements of Nb>500ppm, Ta<100ppm, Zr>100ppm, Hf<20ppm; and more than 50% of the markers in all 100 markers have tin isotope ratios δ 124 / 116 Sn NIST3161a <-1.0、δ 120 / 116 Sn NIST3161a When <-0.5, the deposit is a skarn-type tin deposit; When the cathode luminescence images of the contemporaneous markers of the said markers are clean and transparent, without fluid inclusions and other obvious hydrothermal minerals; and more than 50% of the markers in all 100 markers have trace elements of Nb < 100ppm, Ta < 10ppm, Zr < 10ppm, Hf < 1ppm; and more than 50% of the markers in all 100 markers have tin isotope ratios δ 124 / 116 Sn NIST3161a <-4.0、δ 120 / 116 Sn NIST3161a When <-2.0, the deposit is a quartz vein type tin ore; The contemporary markers refer to markers whose age difference after U-Pb dating is less than 10%.

9. The method according to claim 1, characterized in that In the U-Pb dating analysis, the detection position of the marker is a position where there are no obvious mineral or fluid inclusions between the center and the edge of the marker.

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