CN114397422A - Calculation method of element mobility during the formation of clay minerals in sandstone-type uranium deposits - Google Patents

Abstract

The invention belongs to the field of geological exploration, and particularly discloses a method for calculating element mobility in a process of forming sandstone-type uranium deposit clay minerals, which comprises the following steps: step 1, sandstone geochemical zonal division; step 2, collecting a sample; step 3, measuring principal elements; step 4, selecting inert elements; and 5, calculating the mobility. The method can directly judge the active elements and the inactive elements in the sandstone-type uranium deposit alteration process, and can quantitatively calculate the migration rate of each active element relative to the native sandstone.

Description

Calculation method of element mobility during the formation of clay minerals in sandstone-type uranium deposits

technical field

The invention belongs to the field of geological exploration, and in particular relates to a method for calculating element mobility during the formation of clay minerals in sandstone-type uranium deposits.

Background technique

The changes in composition and content of clay minerals between different geochemical zones are essentially the changes in the content of elements, and microscopically manifest as in- and out-migration of elements. During the research, it was found that there are two ways to change the element content, the first is the change of the element's own content, and the second is the change of the element content due to the change of the content of other elements. In addition, it is believed that most of the geological processes in nature occur in a relatively open system. When the open system has significant changes in mass and volume, it is impossible to directly compare the element content of the rock before and after the occurrence of geological action. Recognize changes in its chemical composition.

The same is true for the study of sandstone-type uranium deposits. The previous studies on the element geochemistry of the interlayer oxidation zone mainly focused on the analysis and comparison of the element content of different geochemical zones, while few scholars considered the mass and volume of the ore-bearing target layer. The effect of changes on the element content.

Sandstone-type uranium deposits belong to epigenetic-low temperature hydrothermal deposits, which meet the application requirements of mass balance theory. Therefore, mass balance theory is introduced this time, and this method is used to quantitatively explore the change law of elements in the evolution of clay minerals in various geochemical zones.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a kind of calculation method of element mobility in the clay mineral formation process of sandstone type uranium deposit, which can quantitatively calculate the in-migration and migration degree of each element in the clay mineral formation process.

The technical scheme that realizes the object of the present invention:

A method for calculating element mobility in the formation process of clay minerals of sandstone-type uranium deposits, the method specifically comprises the following steps:

Step 1. Sandstone geochemical zoning division;

Step 2, sample collection;

Step 3. Determination of major elements;

Step 4. Inert element selection;

Step 5, mobility calculation.

The step 1 is specifically as follows: according to rock color, reducing medium content, and uranium element analysis, the sandstone is divided into paleo-oxidized sandstone, uranium mineralized sandstone and primary sandstone; paleo-oxidized sandstone and primary sandstone are divided by rock color; Uranium elemental analysis identifies uranium mineralized sandstone.

The step 2 is specifically: selecting a typical borehole that can cover the entire deposit, and selecting samples of paleo-oxidized sandstone, uranium mineralized sandstone, and primary sandstone in the core of the lower Zhiluo Formation of each borehole, and the sample lithology is: Massive coarse sandstone.

The step 3 is specifically as follows: cleaning the surface of the sample, breaking the sample into powder, and performing major element analysis by using an X-ray fluorescence spectrometer.

In the step 3, the main elements include SiO ₂ , Al ₂ O ₃ , CaO, FeO, Fe ₂ O ₃ , MgO, Na ₂ O, K ₂ O, MnO, TiO ₂ , and P ₂ O ₅ .

The step 4 includes:

Step 4.1, make Grant diagram;

Step 4.2, draw Grant isolines;

Step 4.3, select the inert element.

The step 4.1 is specifically as follows: the pre-alteration concentration C _i ^O and the post-alteration concentration C _i ^A of various major element components of primary sandstone, paleo-oxidized sandstone, and mineralized sandstone are used as the X and Y coordinate projection points, respectively. , to make Grant diagrams of paleo-oxidized sandstone-primary sandstone and uranium-mineralized sandstone-primary sandstone, respectively.

The step 4.2 is specifically: using the formula K=MO ^/ MA to calculate the slope ^K of the Grant isopotential line, and taking the calculated K as the slope, draw a straight line passing through the origin (0, 0), and this straight line is Grant etc. bit line.

In the step 4.2, calculating the slope K of the Grant isoline includes:

A major element case:

K ₁ =MO ^/ MA ^{= CO} / ^CA ,

Among them, K ₁ is the slope of a major element; ^MO and MA are the rock mass before and after alteration, respectively; ^CO and ^CA are the concentration of ^a major element in the rock before and after alteration, respectively;

Two or more major elements:

K ₂ =MO ^{/MA =∑C i O ×C i A} _/ ^∑ ₍ ^C _i ^A ) ²

Among them, K ₂ is the slope of two or more major elements; ^MO and M ^A are the rock mass before and after alteration, respectively; C _i ^O and C _i ^A are the element i in the rock before and after alteration. after the concentration.

The step 4.3 is specifically: analyzing the Grant diagrams of ancient oxidized sandstone-primary sandstone and uranium mineralized sandstone-primary sandstone, and selecting the Grant diagrams simultaneously located on the Grant diagrams of primary sandstone-paleo-oxidized sandstone and primary sandstone-mineralized sandstone Grant diagrams. element, which is an inert element.

The calculation formula of the mobility in the step 5 is:

△C _i =C _i ^A /KC _i ^O

where ΔC _i is the mobility;

K is the slope of the Grant isoline;

C _i ^O and C _i ^A are the concentrations of element i in the rock before and after alteration.

The beneficial technical effect of the present invention is:

1. The method for calculating element mobility in the formation process of clay minerals in sandstone-type uranium deposits provided by the present invention can directly judge the active elements and inactive elements in the alteration process of sandstone-type uranium deposits, and can quantitatively calculate the relative relative value of each active element. The in-migration rate of primary sandstone.

2. The element in and out rate obtained by the method for calculating element mobility in the formation process of clay minerals in a sandstone-type uranium deposit provided by the present invention can scientifically and reasonably explain the most essential reasons for the change of mineral composition and content in the alteration process , minerals are all composed of elements. In sandstone-type uranium ore, the in and out of Fe element can be understood as the increase or decrease in the content of pyrite, chlorite and other minerals, and the in and out of Ca element can be understood The increase or decrease of calcite content can more accurately explain the genetic mechanism of uranium deposits, and then predict the prospect and indicate the prospecting direction.

3. The calculation method of element mobility in the formation process of clay minerals in a sandstone-type uranium deposit provided by the present invention covers the process from field geological observation and sampling to indoor experiments and data analysis. The design method has an accurate entry point, grasps the essential problem, and collects samples The object, analysis and test requirements and purposes are clear, the formula calculation steps are clear and reasonable, and the operability is strong.

Description of drawings

Fig. 1 is the calculation method flow chart of element mobility in a kind of sandstone type uranium deposit clay mineral formation process provided by the present invention;

Fig. 2 is the inert element discrimination diagram of each geochemical zone of the Zhiluo Formation obtained by applying Grant equation and Grant isotline slope to the Nalinggou uranium deposit provided by the present invention; wherein, Fig. 2A is the inert element discrimination diagram of the paleo-oxidative zone ; Fig. 2B is a discriminant diagram of inert elements in the uranium mineralization zone;

Fig. 3 is an in-migration diagram of elements from each geochemical zone of Zhiluo Formation of Nalinggou uranium deposit provided by the present invention; wherein, Fig. 3A shows the in-migration of SiO ₂ , Al ₂ O ₃ , FeO and Fe ₂ O ₃ -Emigration diagram; Fig. 3B is an in-migration-immigration diagram of CaO, Na ₂ O, K ₂ O; Fig. 3C is an in-migration-out diagram of MgO, MnO, P ₂ O ₅ .

Detailed ways

The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

As shown in Figure 1, the present embodiment takes the Nalinggou uranium deposit in the northeastern part of the Ordos Basin as an example to provide a method for calculating element mobility during the formation of clay minerals in a sandstone-type uranium deposit. The method specifically includes the following steps:

Step 1. Sandstone geochemical zoning division

According to rock color, reducing medium content (the content of carbon (organic matter) in sandstone observed by hand specimen), and uranium element analysis, the sandstone is divided into paleo-oxidized sandstone, uranium mineralized sandstone and primary sandstone. Paleo-oxidized sandstone and primary sandstone are divided by rock color; uranium mineralized sandstone is identified by reducing medium content and uranium element analysis.

Through the observation of borehole cores, the classification standard of paleo-oxidized sandstone and primary sandstone of Nalinggou uranium deposit is determined: the color of the oxidized residual sandstone is purplish red and brick red, the grain size is generally fine-siltstone, the degree of cementation is high, and the basic No reducing substances such as charcoal and pyrite are found; the color of the sandstone that has undergone the secondary reduction of oil and gas in the later stage of the target layer is green and gray-green, and basically does not contain reducing substances such as sulfide or organic matter, and the particle size is generally fine- Coarse sandstone, with weak cementation and loose sand, rarely see carbon, pyrite and other reducing substances. The construction unit in this area only retains the secondary reduction sandstone, so only the secondary reduction sandstone is used as the ancient oxidized sandstone. The primary sandstone is gray in color, with high content of reducing substances such as sulfide or organic matter, with a wide range of particle size distribution, loose sand, and poor cementation. The uranium mineralized sandstone is preliminarily identified by the HD2000 gamma radiation meter measured by the Beijing Institute of Geology of the Nuclear Industry. Generally, the core measured in the field is considered to contain ore above 5nc/kg.h; after sampling, the U content is further determined by analyzing and testing. Generally, U>100×10μg/g is considered as uranium mineralized sandstone.

Step 2. Sample collection

After completing the division of sandstone geochemical zoning, samples were taken in units of ore deposits, and typical boreholes that could cover the entire ore deposit, namely uranium ore holes, were selected from the cores of the lower Zhiluo Formation in each borehole. samples of secondary reduced sandstone, uranium mineralized sandstone and primary sandstone. The lithology of the sample is massive coarse sandstone with a size of 3cm×6cm×9cm. The collected samples were numbered: ES ₁ , ES ₂ , ES ₃ , ES ₄ , . . . , ES _n .

Step 3. Determination of major elements

After sampling, the obtained samples were removed from the surface impurities and weathered epidermis, and then crushed into 200-mesh powder. 50g of samples were taken and sent to the analysis and testing unit. Table 1 shows the analysis results of SiO ₂ , Al ₂ O ₃ , CaO, FeO, Fe ₂ O ₃ , MgO, Na ₂ O, K ₂ O, MnO, TiO ₂ , P ₂ O ₅ and the like.

Table 1 Determination and analysis results of major elements

ancient interlayer oxidation zone Uranium mineralization zone native band SiO₂ 70.82 72.24 72.46 Al₂O₃ 12.92 12.57 12.96 Fe₂O₃ 4.01 3.06 2.24 FeO 2.26 1.71 1.44 CaO 0.92 1.10 1.01 Na₂O 1.98 2.10 2.06 K₂O 3.43 3.38 3.42 MgO 1.53 1.04 1.19 MnO 0.06 0.05 0.03 P₂O₅ 0.09 0.09 0.09 TiO₂ 0.47 0.44 0.44

Step 4. Inert element selection

The interlayer oxidized sandstone is divided into paleo-oxidized sandstone, uranium mineralized sandstone and primary sandstone. The following will calculate the migration of elements in each geochemical zone relative to the primary sandstone elements, so as to illustrate the quantification of different zone elements in the evolution of clay minerals. migrate.

Step 4.1, make Grant diagram

The pre-alteration concentration C _i ^O and the post-alteration concentration C _i ^A of the primary sandstone, paleo-oxidized sandstone, and mineralized sandstone are used as the X and Y coordinate projection points, that is, for the paleo-oxidized zone Inertness, take the log value of each element content in the primary zone as the X-axis, and the log value of each element content in the paleo-oxidation zone as the Y-axis, make a Grant diagram, as shown in Figure 2A; The logarithmic value of element content is on the X axis, and the logarithmic value of each element content in the uranium mineralization zone is on the Y axis. The Grant diagram is made, and the Grant diagram is shown in Figure 2B.

Step 4.2, draw Grant isolines

Calculate the slope of the Grant isoline. The formula for the slope of the Grant isoline is as follows:

A major element case:

K ₁ =MO ^/ MA ^{= CO} / ^CA ,

Among them, K ₁ is the slope of a major element; ^MO and MA are the rock mass before and after alteration, respectively; ^CO and ^CA are the concentration of ^a major element in the rock before and after alteration, respectively;

Two or more major elements:

K ₂ =MO ^{/MA =∑C i O ×C i A} _/ ^∑ ₍ ^C _i ^A ) ²

Among them, K ₂ is the slope of two or more major elements; ^MO and M ^A are the rock mass before and after alteration, respectively; C _i ^O and C _i ^A are the element i in the rock before and after alteration. after the concentration.

In this example, more than two major elements are included, so the slopes K ₂ of the Grant isolines of the Grant diagram in Fig. 2 are respectively: for the paleo-oxidative zone-primary zone rocks (Fig. 2A), the calculated result of K ₂ is 0.9889; for Uranium mineralized zone _- primary zone rocks (Fig. 2B), K2 calculated to be 0.9905.

Taking the calculated K ₁ or K ₂ as the slope, draw a straight line passing through the origin (0, 0).

Step 4.3, select inert elements

Grant contours are points that connect the evolution trajectories of elements with the same concentration change ratio from the original rock, and inactive elements are often located on a concentration contour. Comprehensively analyze the inactive elements (inert elements) of ancient oxidized sandstone and mineralized sandstone facies to primary sandstone. As shown in Figure 2, the paleo-oxidized sandstone-primary sandstone and uranium mineralized sandstone-primary sandstone Grant diagrams were analyzed (Figure 2A is the paleo-oxidized sandstone-primary sandstone Grant diagram, and Figure 2B is the uranium mineralized sandstone-primary sandstone Grant diagram), Elements located on the Grant isolines of the Grant diagram of primary sandstone-paleo-oxidized sandstone and primary sandstone-mineralized sandstone at the same time are selected as suitable inert elements (inactive elements).

As shown in Figure 2, TiO ₂ , SiO ₂ , Al ₂ O ₃ , K ₂ O, Na ₂ O can be used as inert elements, but considering that the ore-bearing target layer may or may suffer from the burial process and the interlayer oxidation process The transformation of acidic or alkaline fluids can easily cause the in and out of SiO ₂ , Al ₂ O ₃ , K ₂ O and Na ₂ O, so TiO ₂ is finally selected as an inert element.

Step 5, Mobility Calculation

According to the inert element TiO ₂ obtained in step 4, calculate the incremental ΔC of each geochemical zone relative to the element gain or loss in the primary zone, and make the element in-migration map of each geochemical zone in the Zhiluo Formation.

According to the Gresers formula, the increment △C _i of the element gain or loss of each geochemical zone relative to the primary zone is calculated. The Gresers formula is as follows:

C _i ^A = ^{MO /MA (C i O +} _ΔC ⁱ ₎

in,

C _i ^O , C _i ^A are the concentrations of element i in the rock before and after alteration;

△C _i is the gain or loss of element i in each geochemical zone in the rock relative to the original zone, that is, the mobility of element i;

^MO and ^MA are rock masses before and after alteration, respectively.

The calculation formula of the gain or loss increment ΔC _i of element i in the rock is:

ΔC _i =C _i ^A /( ^MO / ^MA )-C _i ^O =C _i ^A /KC _i ^O

in,

K is the slope of the Grant isoline;

C _i ^O and C _i ^A are the concentrations of element i in the rock before and after alteration.

Table 2 shows the calculation results of the incremental ΔC of each geochemical zone relative to the element gain or loss of the primary zone.

Table 2 The calculation results of the incremental ΔC of each geochemical zone relative to the element gain or loss of the primary zone

In the Grant diagram, the projected point of the element above the Grant isoline means that the element was acquired during alteration or mineralization, while the projected point below the Grant isoline means that the element has been lost.

As shown in Fig. 3, the in-migration characteristics of elements during uranium mineralization can be clearly seen. Among them, compared with the original sandstone in the original zone that has not been oxidized and reformed, the in-migrated elements of the sandstone in the ancient oxidation zone are Fe ₂ O ₃ , FeO, MgO and MnO, while the out-migrated elements are SiO ₂ , Al ₂ O ₃ , CaO, Na ₂ O, K ₂ O and P ₂ O ₅ , indicating that the sandstone of the paleo-oxidative zone was reformed by the strong acidic oxidizing fluid in the early stage, and also suffered the reformation of the alkaline Fe and Mg-rich fluid in the later stage; The in-migrated elements of sandstone are Fe ₂ O ₃ , FeO, CaO, Na ₂ O and MnO, while the out-migrated elements are SiO ₂ , Al ₂ O ₃ , K ₂ O and MgO, indicating that in the process of uranium mineralization, carbonic acid is closely related to each other. The formation of salt is closely related.

The present invention has been described in detail above in conjunction with the accompanying drawings and embodiments, but the present invention is not limited to the above-mentioned embodiments, and within the scope of knowledge possessed by those of ordinary skill in the art, various kind of change. The content that is not described in detail in the present invention can all adopt the prior art.

Claims (11)

1. a calculation method of element mobility in sandstone type uranium deposit clay mineral formation process, is characterized in that, described method specifically comprises the following steps: Step 1. Sandstone geochemical zoning division; Step 2, sample collection; Step 3. Determination of major elements; Step 4. Inert element selection; Step 5, mobility calculation. 2. the calculation method of element mobility in a kind of sandstone type uranium deposit clay mineral formation process according to claim 1, is characterized in that, described step 1 is specifically: according to rock color, reducing medium content, uranium element analysis Sandstone is divided into paleo-oxidized sandstone, uranium-mineralized sandstone and primary sandstone; paleo-oxidized sandstone and primary sandstone are divided by rock color; uranium-mineralized sandstone is identified by reducing medium content and uranium element analysis. 3. the calculation method of element mobility in a kind of sandstone type uranium deposit clay mineral formation process according to claim 2, it is characterized in that, described step 2 is specifically: choose the typical borehole that can cover the whole deposit, in every In the cores of the lower Zhiluo Formation from each drill hole, samples of paleo-oxidized sandstone, uranium mineralized sandstone and primary sandstone were selected respectively. The lithology of the samples is massive coarse sandstone. 4. the calculation method of element mobility in a kind of sandstone type uranium deposit clay mineral formation process according to claim 3, is characterized in that, described step 3 is specially: clean sample surface, sample is broken into powder, utilize X Fluorescence spectrometer for major element analysis. 5. The method for calculating element mobility in the formation process of clay minerals in a sandstone-type uranium deposit according to claim 4, wherein in the step 3, major elements include SiO ₂ , Al ₂ O ₃ , CaO, FeO, Fe ₂ O ₃ , MgO, Na ₂ O, K ₂ O, MnO, TiO ₂ , P ₂ O ₅ . 6. the calculation method of element mobility in a kind of sandstone type uranium deposit clay mineral formation process according to claim 5, is characterized in that, described step 4 comprises: Step 4.1, make Grant diagram; Step 4.2, draw Grant isolines; Step 4.3, select the inert element. 7. the calculation method of element mobility in a kind of sandstone type uranium deposit clay mineral formation process according to claim 6, is characterized in that, described step 4.1 is specially: utilize primary sandstone and paleo-oxidized sandstone, mineralized sandstone The pre-alteration concentration of C _i ^O and the post-alteration concentration of C _i ^A of various major element components are used as the X and Y coordinate projection points, respectively, and the Grant diagrams of paleo-oxidized sandstone-primary sandstone and uranium mineralized sandstone-primary sandstone are made respectively. . 8. the calculation method of element mobility in a kind of sandstone type uranium deposit clay mineral formation process according to claim 7, is characterized in that, described step 4.2 is specially: utilize formula K=MO ^{/ MA} to calculate Grant etc. The slope of the bit line, K, takes the calculated K as the slope, and draws a straight line passing through the origin (0, 0). This straight line is the Grant isoline. 9. the calculation method of element mobility in a kind of sandstone type uranium deposit clay mineral formation process according to claim 8, is characterized in that, in described step 4.2, calculating Grant isotline slope K comprises: A major element case: K ₁ =MO ^/ MA ^{= CO} / ^CA , Among them, K ₁ is the slope of a major element; ^MO and MA are the rock mass before and after alteration, respectively; ^CO and ^CA are the concentration of ^a major element in the rock before and after alteration, respectively; Two or more major elements: K ₂ =MO ^{/MA =∑C i O ×C i A} _/ ^∑ ₍ ^C _i ^A ) ² Among them, K ₂ is the slope of two or more major elements; ^MO and M ^A are the rock mass before and after alteration, respectively; C _i ^O and C _i ^A are the element i in the rock before and after alteration. after the concentration. 10. the calculation method of element mobility in a kind of sandstone-type uranium deposit clay mineral formation process according to claim 9, is characterized in that, described step 4.3 is specially: analyze ancient oxidized sandstone-primary sandstone and uranium mineralized sandstone - Grant diagram of primary sandstone, select the elements located on the Grant isolines of the Grant diagram of primary sandstone-paleo-oxidized sandstone and primary sandstone-mineralized sandstone at the same time, that is, inert elements. 11. the calculation method of element mobility in a kind of sandstone type uranium deposit clay mineral formation process according to claim 10, is characterized in that, in described step 5, the calculation formula of mobility is: △C _i =C _i ^A /KC _i ^O where ΔC _i is the mobility; K is the slope of the Grant isoline; C _i ^O and C _i ^A are the concentrations of element i in the rock before and after alteration.

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