Rare earth prospecting method based on particle size analysis of ultra-fine particle sediments

Abstract

The invention belongs to the technical field of rare earth mineral exploration, and particularly relates to a rare earth prospecting method based on particle size analysis of ultra-fine particle sediments, which comprises the following steps: sampling a clay rock stratum at the bottom of Xuanwei group, and analyzing the particle size of the sample and the composition of each particle size; and when the proportion of the sample with the particle size of 111.00-654.11 microns is 50%-60%, the proportion of the sample with the particle size of 0.04-0.15 microns is 15%-25%, and the proportion of the sample with the particle size of 2.42-7.64 microns is 20%-30%, judging that the sample is a rare earth enriched dominant phase region. The method disclosed by the invention has a relatively good effect on sedimentary microfacies analysis of sedimentary type rare earth ore-bearing construction which has no obvious sedimentary structure and no obvious sedimentary facies mark and is relatively strongly damaged by later-stage transformation; meanwhile, the sedimentary rare earth prospecting target area can be delineated rapidly and greenly, the cost of the exploration stage is greatly reduced, and the prospecting efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of rare earth mineral exploration, and in particular relates to a rare earth prospecting method based on ultra-fine grain-grade sediment particle size analysis. Background Art

[0002] In recent years, a new type of rare earth resource, "paleo-continental sedimentary rare earth ore (hereinafter referred to as sedimentary rare earth ore)", which is rich in high-value key rare earth elements praseodymium, neodymium, terbium, dysprosium (CREE) and co-exists with valuable elements such as niobium, zirconium, gallium, and titanium, has been discovered in the western edge of the Upper Yangtze Platform and the adjacent areas of Sichuan, Yunnan, and Guizhou. It is significantly different from the carbonate / alkaline lithology rare earth deposits, ion adsorption rare earth deposits, and seashore sand-type rare earth deposits that are currently mainly mined in the world. The ore-bearing structure of the sedimentary rare earth ore is the clay rock at the bottom of the Xuanwei Formation of the Upper Permian, with extremely fine grains. The mineralized clay rock is mainly composed of kaolinite and illite. A small amount of complete plant fossils such as Rajahia, Compsopteris contracta, Compsopteris contracta and Sphenophyllum from the Late Permian are still preserved in the mineralized formation. Horizontal stratification and layered structure are partially preserved, which has typical paleo-continental sedimentary genesis characteristics. In the plane, the mineralized clay rock formation is concentrated in the east of Yingjing-Hanyuan-Zhaojue-Jinyang-Zhaotong-Xuanwei-Qujing line and the west of Muchuan-Gongxian-Weixin-Bijie-Liupanshui line; there are no rare earth anomalies in the sediments of the marine-continental interphase in the east during the same period.

[0003] In summary, this type of rare earth deposit has obvious sedimentary characteristics, but due to the strong clay lithification of the ore-bearing layer and the extremely fine grain size (generally micrometer level), very few sedimentary structures that can be used to restore lithofacies paleogeography are preserved, which has a great impact on the sedimentary environment, especially prospecting.

[0004] In June 2009, the journal "Journal of Central South University (Natural Science Edition)" published a journal article entitled "Microfacies types of deep-water fine-grained sedimentary systems in the Qingshankou Formation in the Qijia-Gulong Sag of the Songliao Basin and their significance for shale oil and gas exploration". The journal article carried out fine core observation, well logging analysis, high-resolution three-dimensional seismic interpretation, whole-rock optical slice micro-component determination, and argon ion polishing-field emission scanning electron microscope micro-pore research on the mud shale area of ​​the Qingshankou Formation in the Qijia-Gulong Sag of the Songliao Basin. The fine-grained sandstone, siltstone, and mudstone sediments were divided into six sedimentary microfacies, namely oil shale, deep lake mud, bottom flow reformed sand, shell beach, turbidite, and block transport body.

[0005] The above-mentioned journal article proposed a microfacies type analysis method for deepwater fine-grained sedimentary systems, but its core is to serve oil and gas exploration, and the technical methods are core observation, well logging analysis, high-resolution three-dimensional seismic interpretation, optical microscopic component determination, and microscopic pore research. It is significantly different from the method introduced in this article, and the sediment particle size targeted by this patented technology is also finer.

[0006] In 2019, the Institute of Comprehensive Utilization of Mineral Resources, Chinese Academy of Geological Sciences proposed "a rare earth prospecting method based on large-scale profile sedimentary microfacies analysis". Although it is also a sedimentary phase constrained prospecting technology method for sedimentary rare earths in the region, it still remains at the macroscopic research of profiles or drill cores, and cannot distinguish sedimentary microfacies well, nor does it conduct grain size analysis on ultra-fine-grained mineral-bearing clay rock structures. Summary of the invention

[0007] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a rare earth prospecting method based on ultra-fine grain size analysis of sediments.

[0008] The object of the present invention is achieved through the following technical scheme: A rare earth prospecting method based on ultra-fine grain size analysis of sediments, comprising the following steps:

[0009] The clay rock layer at the bottom of the Xuanwei Formation was sampled and the particle size and composition of each particle size were analyzed;

[0010] When the particle size of 111.00-654.11 microns accounts for 50% to 60%, the particle size of 0.04-0.15 microns accounts for 15% to 25%, and the particle size of 2.42-7.64 microns accounts for 20% to 30% in the sample, it is determined to be a dominant phase area enriched in rare earths.

[0011] Furthermore, before sampling the clay rock layer at the bottom of the Xuanwei Formation, the following steps are also included: collecting existing geological data in the area, sorting out the distribution range of the Permian Xuanwei Formation of the mineralized structure, conducting on-site field investigations, and verifying the exposure and continuity of the clay rock layer at the bottom of the Xuanwei Formation.

[0012] Furthermore, before sampling the clay rock layer at the bottom of the Xuanwei Formation, the following steps are specifically included: fully collect the existing 1:200,000 and 1:50,000 mineral geological data in the area, as well as larger-scale mining area geological data; sort out the distribution range, distribution characteristics, occurrence and continuity of the Permian Xuanwei Formation of the mineral-bearing structure; conduct on-site field investigations and verifications in sections where the clay rock mineral-bearing structures at the bottom of the Xuanwei Formation are continuously exposed.

[0013] Furthermore, the method for sampling the clay rock layer at the bottom of the Xuanwei Formation includes the following steps: perpendicular to the formation direction, deploying sampling sections for the clay rock layer at the bottom of the Xuanwei Formation at intervals of 400 to 800 meters, collecting particle size analysis samples at intervals of 20 centimeters from the bottom to the top of each section, and each sample is greater than 5 kilograms. Sampling runs through the clay rock layer.

[0014] The method for selecting the spacing deployment distance is: if the outcrop is continuous and stable, and the rock properties do not change much, then the deployment is carried out at a spacing of 800 meters; if the outcrop is discontinuous and the rock properties change greatly, then the deployment is increased to a spacing of 400 meters.

[0015] Furthermore, the method for analyzing the particle size of the sample and the composition of each particle size fraction includes:

[0016] 1) Use a laser analyzer with a resolution greater than 0.01 micron to conduct particle size analysis;

[0017] 2) Place the sample in a beaker and treat with H2O2 to remove organic matter;

[0018] 3) heating with HCL to remove carbonate;

[0019] 4) After the solution was precipitated for 12 hours, the clear supernatant was separated and removed, and a 0.05 mol / L (NaPO3)6 solution was used as a dispersant to disperse the precipitate particles at the bottom;

[0020] 5) Before the particle size measurement, the beaker was ultrasonically stirred for 5 minutes;

[0021] 6) Particle size analysis: Each sample was measured 3 times, and the average value was taken as the particle size data of each sample;

[0022] 7) Grain size endmember decomposition: Neural network-based endmember modeling analysis (NNEMA) is used in QGrain software to decompose the grain size distribution (GSD), divide it into different particle sizes, and calculate the particle size composition and proportion of each sampling layer.

[0023] Furthermore, after determining the dominant phase area of ​​rare earth enrichment, trenching and drilling work are arranged in the dominant phase area of ​​rare earth enrichment to guide rare earth prospecting and exploration.

[0024] Specifically: According to the exploration line spacing specified in the single-ore solid mineral exploration specifications, trenching and drilling verification are carried out, chemical analysis is performed, prospecting target areas are delineated, and resource quantities are estimated.

[0025] The clay rock strata rich in rare earths, niobium and other elements in the adjacent areas of Sichuan, Yunnan and Guizhou are widely distributed and continuous, but there are still differences in the horizontal direction. Since the clay rock strata are ultra-fine (grain size <0.0156mm), these differences are difficult to distinguish effectively with the naked eye. Especially in the process of sedimentary environment reconstruction, the lack of evidence such as grain size, vertical change relationship, sedimentary structure, and fossils visible to the naked eye makes it difficult to divide and compare fine sedimentary microfacies. An effective sedimentary microfacies identification method is needed to constrain the sedimentary environment.

[0026] The beneficial effects of the present invention are:

[0027] The present invention uses particle size and particle size end member decomposition to replace traditional chemical analysis, which saves time and cost in prospecting, and also avoids the use of a large number of trenching and drilling projects in the early stage of geological exploration, which damages the surface and affects the ecological environment.

[0028] The method of the present invention has a good effect on the sedimentary microfacies analysis of sedimentary rare earth ore-bearing structures without obvious sedimentary structures, obvious sedimentary phase marks, and which are severely damaged by later transformations; at the same time, the method can quickly and greenly delineate sedimentary rare earth prospecting target areas, greatly reducing the cost of the exploration stage and improving the efficiency of prospecting. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a regional geological map and distribution map of mineral-bearing formations in Bijie-Liupanshui area of ​​Guizhou;

[0030] Figure 2 The grain size and end-member composition of a typical sedimentary rare earth ore profile (Chahe profile, Heishitou Town, Bijie City, Weining County, Guizhou Province);

[0031] Figure 3 The corresponding relationship between the grain size and end-member composition of the typical sedimentary rare earth ore profile in Shicang (SCP) area of ​​Weining County and elements such as rare earth and niobium;

[0032] Figure 4 The corresponding relationship between the grain size and end-member composition of the typical sedimentary rare earth ore profile in the Salaxi (SLXP) area of ​​Hezhang County and the elements such as rare earth and niobium;

[0033] Figure 5 The sedimentary microfacies are typical sedimentary rare earth mineral profiles in Shicang (SCP) area of ​​Weining County and Salaxi (SLXP) area of ​​Hezhang County, and are derived from the grain size and grain size end-member decomposition inversion. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following.

[0035] Example 1

[0036] The ancient terrestrial sedimentary rare earth deposits in the adjacent areas of Sichuan, Yunnan and Guizhou are concentrated in the east of Yingjing-Hanyuan-Zhaojue-Jinyang-Zhaotong-Xuanwei-Qujing and west of Muchuan-Gongxian-Weixin-Bijie-Liupanshui. At present, many prospecting target areas have been discovered in Muchuan, Sichuan, Xuanwei, Yunnan, and Weining, Bijie, Guizhou, and some of them are being surveyed.

[0037] According to the rare earth prospecting technology described in this patent, based on the existing sedimentary rare earth ore target area, including the typical profile (Chahe profile CHP in Heishitou Town, Bijie City, Weining County, Guizhou Province), Shicang (SCP) in Weining County, Guizhou Province and Salaxi (SLXP) in Hezhang County, Guizhou Province were selected to carry out the verification work of the method of the present invention. The location is as follows Figure 1 shown.

[0038] The actual operation is as follows:

[0039] S1 Fully collect the existing geological data in the area, sort out the distribution range of the Permian Xuanwei Formation of the ore-bearing structure, carry out on-site field investigations, and verify the exposure and continuity of the clay rock layer at the bottom of the Xuanwei Formation.

[0040] Application example: The geological data of western Bijie and northern Liupanshui in Guizhou Province were collected comprehensively, and the distribution range of the Permian Xuanwei Formation was sorted out ( Figure 1 Through field investigation, the outcrop and continuity of the clay layer at the bottom of the Xuanwei Formation were verified. Among them, in addition to the existing sedimentary rare earth mineral target area (except the Maojiaping Chahe area), the ore-bearing structures at the bottom of the Xuanwei Formation in Shicang (SCP) of Weining County and Salaxi (SLXP) of Hezhang County are continuously and stably exposed.

[0041] S2 is perpendicular to the stratigraphic direction and deploys sampling sections for the clay rock layer at the bottom of the Xuanwei Formation at intervals of 400 to 800 meters. Grain size analysis samples are collected from the bottom to the top of each section at intervals of 20 centimeters, and each sample weighs more than 5 kilograms.

[0042] Application example: Perpendicular to the stratigraphic direction, targeted particle size analysis sampling profiles were deployed at intervals of 800 meters in the north-southeast-southwest direction in the Shicang (SCP) area and the nearly north-south direction in the Salar Creek (SLXP) area of ​​Hezhang County. Particle size analysis samples were collected at intervals of 20 cm from the bottom to the top of each profile, and each sample was greater than 5 kg. Among them, 30 samples were collected from typical profiles in the Shicang (SCP) area; 38 samples were collected from typical profiles in the Salar Creek (SLXP) area.

[0043] S3 carries out laser particle size analysis, systematically analyzing the particle size of the sample and the composition of each particle size fraction.

[0044] Application example: The particle size analysis of 68 verification samples was completed. In the actual work, the Mastersizer3000 laser particle size analyzer was selected, and its particle size analysis range is 0.01 to 3500 microns. First, the sample was placed in a beaker and treated with 10% H2O2 to remove organic matter; then heated with 10% HCL to remove carbonates; after the solution was allowed to settle for 12 hours, the clarified supernatant was extracted, and 0.05 mol / L (NaPO3)6 solution was used as a dispersant to disperse the sediment particles at the bottom. The beaker was ultrasonically stirred for 5 minutes before the particle size measurement was performed. Each sample was measured 3 times, and the average value was taken as the particle size data for each sample. Finally, the particle size distribution (GSD) was decomposed using the neural network-based end member modeling analysis (NNEMA) in the QGrain software, and different particle sizes were divided to calculate the particle size composition and proportion of each sampling layer. The results are as follows:

[0045] Based on the classification criteria proposed by Folk (1954) and the results of grain size analysis, the sandy silty clay (SSC) composition of all samples collected from the Shicang (SCP) and Salar Creek (SLXP) sections was determined. The SCP samples showed a relatively uniform distribution, mainly composed of clayey sand and muddy sand, with a small amount of sandy clay, sandy mud and clay; the SLXP samples showed a dispersed distribution pattern, as they contained all components except silty sand, sandy clay and clay. The sand content ratio analysis showed that SCP had the highest percentage, followed by SLXP.

[0046] To further explore the differences in particle size composition, all samples were fitted to the particle size end member of the Weibull Function. The results showed that all samples could be decomposed into six basic particle size components (C1-C6), among which the C3 component was the most widely distributed, and only one sample did not contain the C3 component. The C6 and C2 components were distributed in 80% of the samples, and the C1 and C4 components were distributed in 50% of the samples; the C5 component was the least distributed, less than 30% of the samples. The particle size range of C1 was between 0.04-0.15 microns, with an average content of 23.52% (ranging from 1.22% to 55.35%). The particle size range of C2 was 0.19-0.53 microns, with an average content of 13.32% (ranging from 0.62% to 45.87%). The particle size range of C3 was between 2.42-7.64 microns, with an average content of 34.41% (ranging from 0.68% to 87.53%). The particle size range of C4 is between 8.68-40.60 microns, and the average content is 21.19% (range 1.33% to 88.24%). The particle size range of C5 is between 45.60-98.10 microns, and the average content is 5.88% (range 0.03% to 22.85%). The particle size range of C6 is between 111.00-654.11 microns, and the average content is 42.56% (range 0.17% to 78.34%) ( Figure 2 ).

[0047] According to the main ingredients and ingredient combinations, Stone Warehouse (SCP) ( Figure 3 ) and Sara Creek (SLXP)( Figure 4 ) All samples in the section are divided into seven different types ( Figure 5 ), the main end member components are summarized as follows:

[0048] (1) Type I: The typical composition is C1, C3 and C6, while C4 and C5 often serve as minor components alternately. Sometimes C1 is often replaced by C2, presenting a composition of C2, C3 and C6. The main composition characteristics are C1 / C3 / C6 (20% / 25% / 52%).

[0049] (2) Type II: The typical component combination is C1 and C3, while C2, C4, C5 and C6 often alternate as minor components. The main component characteristic is C1 / C3 (43% / 38%).

[0050] (3) Type III: The typical component combination is C2 and C3, while C4, C5 and C6 often appear alternately as minor components, and occasionally there is also a C1 component. The main component characteristic is C2 / C3 (18% / 61%).

[0051] (4) Type IV: The typical component combination is C2, C3, C4 and C6, and the main component characteristic is C4 / C6 (24% / 65%).

[0052] (5) Type V: The typical component combination is C2, C3 and C4, while C5 and C6 often alternate as minor components. The main component characteristic is C3 / C4 (20% / 71%).

[0053] (6) Type VI: The typical composition is C2 and C3, and the main composition characteristic is C2 / C3 (38% / 52%).

[0054] (7) Type VII: The typical component combination is C4 and C6, and the main component characteristics are C4 / C6 (43% / 57%).

[0055] S4 identifies the dominant phase region of rare earth enrichment

[0056] Application example: The above-mentioned Type I is the dominant phase area with rare earth enrichment. The dominant sedimentary microphases of the Shicang (SCP) section are mainly distributed in the 5th to 8th layers, and part of the 10th and 11th layers. Subsequent chemical analysis shows that the highest rare earth content appears in the 5th layer, with the highest grade of rare earth oxide (TREO) reaching 5037ppm and niobium content reaching 235ppm; the dominant sedimentary microphases of the Salaxi (SLXP) section in Hezhang County are mainly distributed in the 4th and 7th layers, with the highest grade of rare earth oxide (TREO) reaching 2492ppm and niobium content reaching 348ppm. The above two areas are new prospecting targets discovered this time, and their grades have reached the "General Industrial Index Requirements for the Ancient Continental Sedimentary Rare Earth Survey Stage", in which the minimum industrial grade requirement for rare earths is TREO greater than 0.18%.

[0057] S5 arranges trenching and drilling work in the dominant phase area rich in rare earths to guide rare earth prospecting and exploration.

[0058] Application example: Currently, two trenches and two drillings have been deployed in the Shicang (SCP) area, with good ore-finding results, both reaching the minimum industrial grade requirements, and one prospecting target area has been submitted.

[0059] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A rare earth prospecting method based on ultra-fine grain size analysis of sediments, characterized in that: The following steps are involved: The clay rock layer at the bottom of the Xuanwei Formation was sampled and the particle size and composition of each particle size were analyzed; When the particle size of 111.00-654.11 microns accounts for 50% to 60%, the particle size of 0.04-0.15 microns accounts for 15% to 25%, and the particle size of 2.42-7.64 microns accounts for 20% to 30% in the sample, it is determined to be a dominant phase area enriched in rare earths.

2. A rare earth prospecting method based on ultra-fine grain size analysis of sediments according to claim 1, characterized in that: Before sampling the clay rock layer at the bottom of the Xuanwei Formation, the following steps are also included: collecting existing geological data in the area, sorting out the distribution range of the Permian Xuanwei Formation of the mineral-bearing structure, conducting on-site field investigations, and verifying the exposure and continuity of the clay rock layer at the bottom of the Xuanwei Formation.

3. A rare earth prospecting method based on ultra-fine grain size analysis of sediments according to claim 2, characterized in that: Before sampling the clay rock layer at the bottom of the Xuanwei Formation, the following steps are specifically included: fully collect the existing 1:200,000 and 1:50,000 mineral geological data in the area, as well as larger-scale mining area geological data; sort out the distribution range, distribution characteristics, occurrence and continuity of the Permian Xuanwei Formation of the mineral-bearing structure; conduct on-site field investigations and verifications in sections where the clay rock mineral-bearing structures at the bottom of the Xuanwei Formation are continuously exposed.

4. The rare earth prospecting method based on ultra-fine grain size analysis of sediments according to claim 1, characterized in that: The method for sampling the clay rock layer at the bottom of the Xuanwei Formation comprises the following steps: perpendicular to the formation direction, a sampling section for the clay rock layer at the bottom of the Xuanwei Formation is arranged at a spacing of 400 to 800 meters, and each section collects particle size analysis samples at a spacing of 20 centimeters from the bottom to the top, and each sample is greater than 5 kilograms. The sampling runs through the clay rock layer. The method for selecting the spacing deployment distance is: if the outcrop is continuous and stable, and the rock properties do not change much, then the deployment is carried out at a spacing of 800 meters; if the outcrop is discontinuous and the rock properties change greatly, then the deployment is increased to a spacing of 400 meters.

5. The rare earth prospecting method based on ultra-fine grain size analysis of sediments according to claim 1, characterized in that: The particle size of the analysis sample and the composition method of each particle size fraction include: 1) Use a laser analyzer with a resolution greater than 0.01 micron to conduct particle size analysis; 2) Place the sample in a beaker and treat with H2O2 to remove organic matter; 3) heating with HCL to remove carbonate; 4) After the solution was precipitated for 12 hours, the clear supernatant was separated and removed, and a 0.05 mol / L (NaPO3)6 solution was used as a dispersant to disperse the precipitate particles at the bottom; 5) Before the particle size measurement, the beaker was ultrasonically stirred for 5 minutes; 6) Particle size analysis: Each sample was measured 3 times, and the average value was taken as the particle size data of each sample; 7) Grain size endmember decomposition: Neural network-based endmember modeling analysis (NNEMA) is used in QGrain software to decompose the grain size distribution (GSD), divide it into different particle sizes, and calculate the particle size composition and proportion of each sampling layer.

6. The rare earth prospecting method based on ultra-fine grain size analysis of sediments according to claim 1, characterized in that: After determining the dominant phase area of ​​rare earth enrichment, trenching and drilling work will be arranged in the dominant phase area of ​​rare earth enrichment to guide rare earth prospecting and exploration. Specifically: According to the exploration line spacing specified in the single-ore solid mineral exploration specifications, trenching and drilling verification are carried out, chemical analysis is performed, prospecting target areas are delineated, and resource quantities are estimated.

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