Drawing method of geochemical map of exposed earth crust rock

Abstract

The invention provides a mapping method of a geochemical map of rock exposed out of earth crust, and belongs to the technical field of geochemical mapping of rock. The method comprises the steps of constructing a multi-source database, carrying out step-by-step attribute matching, calculating a weighted average value of geological unit element contents, and generating a geochemical map. According to the method, a multi-source data fusion technology and a step-by-step attribute matching algorithm are utilized to combine relatively low-density rock data with a geological unit structure and geological unit space distribution, a rock geochemical map is finally generated by relying on a GIS technology, the step-by-step matching method follows an objective rule of rock element distribution, and compared with simple matching, the step-by-step matching method has the advantages that the matching efficiency is greatly improved; the assignment precision can be improved, and the existing rock chemical data can be utilized to the maximum extent; public geological map data are compatible, and the data collection cost is reduced; the requirement for the number of samples is greatly reduced, at least dozens of rock sample data are needed, and the drawing is more accurate along with the increase of the types and the number of the samples.

Description

Technical Field

[0001] This invention belongs to the field of rock geochemical mapping technology, specifically relating to a method for mapping exposed crustal rocks geochemically. Background Technology

[0002] The exposed crust, as the interface between the lithosphere and the episphere, plays a crucial role in the Earth's system cycles, environmental assessments, and resource exploration. Traditional sediment / soil geochemical maps, due to media differentiation effects (such as significant differences in alkali and heavy metal elements between rocks and soils), cannot accurately reflect the geochemical background of rocks.

[0003] The distribution of rock elements is strictly controlled by geological units, violating the first law of geography and rendering traditional spatial interpolation methods ineffective. High-density sampling methods (sampling points spaced several meters to tens of meters apart) are necessary to ensure sample representativeness, and then the elemental content at each sampling point is used to directly generate a map. However, large-scale (e.g., national or regional scale) rock geochemical maps are limited by manpower, time, and funding, making high-density sampling methods unusable. Therefore, large-scale rock geochemical mapping requires addressing how to create reliable geochemical maps using low-density rock samples. Summary of the Invention

[0004] To address the aforementioned shortcomings of existing technologies, this invention aims to provide a method for generating geochemical maps of exposed crustal rocks. This method utilizes multi-source data fusion technology and a hierarchical attribute matching algorithm to combine relatively low-density rock data with geological unit structure and spatial distribution, ultimately generating a rock geochemical map based on GIS technology.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for creating geochemical maps of exposed crustal rocks, comprising the following steps:

[0007] (1) Constructing a multi-source database:

[0008] Elemental content data of rock samples were collected. Based on the lithology, tectonic unit, geological age and geological unit of the rock samples, nine levels of search attributes were generated. The average elemental content of the samples corresponding to each search attribute was calculated to obtain a rock chemistry database.

[0009] Data containing the names of geological units and their spatial distribution information is extracted from digital geological maps to obtain a database of the spatial distribution of geological units.

[0010] By integrating geological unit names, lithology, lithological thickness, and nine levels of search attributes corresponding to the petrochemical database, a geological unit structure database is obtained.

[0011] (2) Hierarchical attribute matching:

[0012] For each tuple in the geological unit structure database, it is matched with the tuples in the petrochemical database in order of priority of the 9-level search attributes, starting with the highest precision attribute. If the match is successful, the element content data of the corresponding tuple in the petrochemical database is assigned to the current tuple in the geological unit structure database and the matching process is terminated. If the match fails, it continues to try to match the next level attribute until the match is successful or all 9 levels of attributes are traversed.

[0013] (3) Calculate the weighted average elemental content of geological units:

[0014] Based on the thickness proportion of each lithology in the geological unit, the thickness-weighted calculation of the element content of the successfully matched elements is performed to obtain the thickness-weighted average value of element content in each geological unit.

[0015] (4) Generate geochemical maps:

[0016] The elemental content and thickness weighted average of each geological unit are linked to the spatial distribution database of geological units. Geological units are then classified and colored according to elemental content using GIS tools to generate rock geochemical maps.

[0017] As a preferred embodiment of the present invention, in step (1), the generation method of the 9-level retrieval attributes is as follows: based on the fields of "primary lithology", "secondary lithology", "primary tectonic unit", "secondary tectonic unit", "geological age" and "geological unit" of the rock sample, the following are combined to generate "primary lithology", "secondary lithology", "primary tectonic unit-primary lithology", "primary tectonic unit-secondary lithology", "secondary tectonic unit-primary lithology", "secondary tectonic unit-secondary lithology", "secondary tectonic unit-age-secondary lithology", "geological unit-primary lithology", and "geological unit-secondary lithology".

[0018] As a preferred embodiment of the present invention, in step (2), the nine-level search attributes are arranged in descending order of matching accuracy as follows: “Geological unit - secondary lithology” → “Geological unit - primary lithology” → “Secondary tectonic unit - age - secondary lithology” → “Secondary tectonic unit - secondary lithology” → “Secondary tectonic unit - primary lithology” → “Primary tectonic unit - secondary lithology” → “Primary tectonic unit - primary lithology” → “Secondary lithology” → “Primary lithology”.

[0019] In a preferred embodiment of the present invention, in step (3), the formula for calculating the elemental content thickness-weighted average of the geological unit is as follows:

[0020]

[0021] Among them, c it represents the elemental content of the i-th lithology in a geological unit. i This represents the thickness of the i-th type of lithology.

[0022] As a preferred embodiment of the present invention, the data sources of the geological unit spatial distribution database include digital geological maps at scales of 1:200,000 to 1:2,500,000, and the lithological thickness data of the geological unit structure database are obtained through regional geological records or publicly available rock stratigraphic data.

[0023] As a preferred embodiment of the present invention, the samples in the rock chemistry database need to cover all primary lithological types in the target area, and the number of samples should not be less than 30.

[0024] As a preferred embodiment of the present invention, in step (4), the specific operation of the GIS tool is as follows: the attribute table of the geological unit spatial distribution database is associated with the assigned element content data through spatial connection; the color levels are divided according to the element content value range, the geological unit polygons are filled with color, and a visual geochemical map is generated.

[0025] Compared with existing technologies, the beneficial technical effects of this invention are as follows: This invention utilizes multi-source data fusion technology and a hierarchical attribute matching algorithm to combine relatively low-density rock data with geological unit structure and spatial distribution. Ultimately, it generates a rock geochemical map using GIS technology. The hierarchical matching method follows the objective laws of rock element distribution, improving the accuracy of value assignment and maximizing the use of existing rock chemical data compared to simple matching. It is compatible with publicly available geological map data (such as 1:500,000, 1:1,500,000, and 1:2,500,000 digital maps), reducing data collection costs. The requirement for a large number of samples is significantly reduced, requiring only a few dozen rock samples (covering all primary lithologies). As the types and quantities of samples increase, the mapping becomes more accurate. This invention provides a high-precision spatial analysis tool for geochemical research, suitable for applications such as heavy metal pollution source apportionment, key mineral exploration target area selection, and construction of rock geochemical benchmark values, possessing significant scientific and engineering value. Attached Figure Description

[0026] Figure 1 This invention provides a mapping process for geochemical maps of exposed crustal rocks.

[0027] Figure 2 This is a partial schematic diagram of the spatial distribution database of geological units in an application example of the present invention;

[0028] Figure 3 This is a partial schematic diagram of the geological unit structure database in an application example of the present invention;

[0029] Figure 4 This is a partial schematic diagram of a rock chemistry database in an application example of the present invention;

[0030] Figure 5 This is a partial schematic diagram of the geological spatial structure database after SiO2 content has been added in an application example of the present invention;

[0031] Figure 6 This is a partial schematic diagram of the weighted average SiO2 thickness of various geological units in an application example of the present invention;

[0032] Figure 7 This is a partial schematic diagram illustrating the association operation between the spatial database of geological units and the content of geological units in an application example of the present invention;

[0033] Figure 8 This is a partial schematic diagram of the associated geological spatial distribution database in an application example of the present invention;

[0034] Figure 9 This is a rock geochemical map of SiO2 based on GIS coloring in an application example of the present invention. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0036] Example

[0037] like Figure 1 As shown, the present invention provides a method for creating geochemical maps of exposed crustal rocks, comprising the following steps:

[0038] (1) Constructing a multi-source database:

[0039] Elemental content data of rock samples were collected. Based on the lithology, tectonic unit, geological age, and geological unit of the rock samples, nine levels of search attributes were generated. The average elemental content of samples corresponding to each search attribute was statistically analyzed to obtain a rock chemistry database. The nine levels of search attributes were generated by combining the fields of "primary lithology," "secondary lithology," "primary tectonic unit," "secondary tectonic unit," "geological age," and "geological unit" of the rock samples to generate "primary lithology," "secondary lithology," "primary tectonic unit-primary lithology," "primary tectonic unit-secondary lithology," "secondary tectonic unit-primary lithology," "secondary tectonic unit-secondary lithology," "secondary tectonic unit-age-secondary lithology," "geological unit-primary lithology," and "geological unit-secondary lithology." The samples in the rock chemistry database must cover all primary lithology types in the target area, and the number of samples must be no less than 30.

[0040] Data containing the names of geological units and their spatial distribution information is extracted from digital geological maps to obtain a spatial distribution database of geological units. The data sources of the spatial distribution database of geological units include digital geological maps at scales of 1:200,000 to 1:2,500,000, and the lithological thickness data of the geological unit structure database are obtained from regional geological records or publicly available lithostratigraphic data.

[0041] By integrating geological unit names, lithology, lithological thickness, and nine levels of search attributes corresponding to the rock chemistry database, a geological unit structure database is obtained.

[0042] (2) Hierarchical attribute matching:

[0043] For each tuple in the geological unit structure database, it is matched sequentially with tuples in the petrochemical database according to the priority order of the 9-level search attributes, starting with the highest precision attribute. If a match is successful, the elemental content data of the corresponding tuple in the petrochemical database is assigned to the current tuple in the geological unit structure database, and the matching process is terminated. If a match fails, the matching continues to try matching the next level attribute until a match is successful or all 9 levels of attributes are traversed. The 9-level search attributes are arranged in descending order of matching precision as follows: "Geological Unit - Secondary Lithology" → "Geological Unit - Primary Lithology" → "Secondary Tectonic Unit - Age - Secondary Lithology" → "Secondary Tectonic Unit - Secondary Lithology" → "Secondary Tectonic Unit - Primary Lithology" → "Primary Tectonic Unit - Secondary Lithology" → "Primary Tectonic Unit - Primary Lithology" → "Secondary Lithology" → "Primary Lithology".

[0044] (3) Calculate the weighted average elemental content of geological units:

[0045] Based on the thickness proportion of each lithology in the geological unit, the thickness-weighted calculation of the element content of the successfully matched elements is performed to obtain the thickness-weighted average value of element content in each geological unit.

[0046] Specifically, the formula for calculating the thickness-weighted average elemental content of a geological unit is as follows:

[0047]

[0048] Among them, c i t represents the elemental content of the i-th lithology in a geological unit. i This represents the thickness of the i-th type of lithology.

[0049] (4) Generate geochemical maps:

[0050] The elemental content and thickness weighted average of each geological unit are linked to the spatial distribution database of geological units. Geological units are then classified and colored according to elemental content using GIS tools to generate rock geochemical maps.

[0051] Specifically, the GIS tool operates as follows: it associates the attribute table of the geological unit spatial distribution database with the assigned element content data through spatial connection; it divides the color levels according to the element content value range, fills the geological unit polygons with color, and generates a visualized geochemical map.

[0052] Application examples

[0053] A second-order tectonic unit of the Kangdian axis was selected, and a petrogeochemical map of SiO2 was prepared according to the method described in the example.

[0054] First, generate a "Spatial Distribution Database of Geological Units". Extract information from the 1:500,000 national digital geological map within the Kangdian Axis region and generate an ArcGIS file named "filename.shp". The "UNITNAME" attribute column contains the name of the geological unit, such as... Figure 2 As shown.

[0055] Second, a "Geological Unit Structure Database" is generated. By collecting regional geological records from Yunnan and Sichuan provinces, where the Kangdian Axis is located, the lithological composition of each geological unit is obtained. The "50w_unitname" field matches the "Geological Unit Structure Database," recording the lithology and thickness information of the geological unit. Using the structure, age, lithology, and geological unit to which the rock sample belongs, a nine-level attribute column is established, such as... Figure 3 As shown.

[0056] Third, establish a "Rock Chemistry Database." This involves obtaining statistical information on the elemental content of different rock types through self-collection, analysis, or literature review. Column A corresponds to the 9-level attributes in the "Geological Unit Structure Database," such as... Figure 4 As shown.

[0057] Fourth, assign the "Rock Chemistry Database" to the "Geological Unit Structure Database," retrieve the 9-level attributes level by level, and assign elemental content to each tuple in the "Geological Unit Structure Database," such as... Figure 3 As shown. The formula for calculating element content is:

[0058] =IF(ISNA(VLOOKUP($L3,'Rock Chemistry Database'!$A:$CE,1,FALSE)),IF(ISNA(VLOOKUP($K3,'Rock Chemistry Database'!$A:$CE,1,FALSE)),IF(ISNA(VLOOKUP($J3,'Rock Chemistry Database'!$A:$CE,1,FALSE)),IF(ISNA(VLOOKUP($I 3,'Rock Chemistry Database'! $A:$CE,1,FALSE)),IF(ISNA(VLOOKUP($H3,'Rock Chemistry Database'!$A:$CE,1,FALSE)),IF(ISNA(VLOOKUP($G3,'Rock Chemistry Database'!$A:$CE,1,FALSE)),IF(ISNA(VLOOKUP($F3,'Rock Chemistry Database'!$A:$CE,1,FALSE)),IF(ISNA(VLOOKUP($E3,'Rock Chemistry Database'!$A:$CE,1,FALSE)),IF(ISNA(VLOOKUP($D3, 'Rock Chemistry Database'! $A:$CE,1,FALSE)),"Not Found",VLOOKUP($D3,'Rock Chemistry Database'!$A:$CE,1,FALSE)),VLOOKUP($E3,'Rock Chemistry Database'!$A:$CE,1,FALSE)),VLOOKUP($F3,'Rock Chemistry Database'!$A:$CE,1,FALSE)),VLOOKUP($G3,'Rock Chemistry Database'!$A:$CE,1,FALSE)),VLOOKUP($H3,'Rock Chemistry Database'!$A:$CE,1,FALSE)),VLOOKUP($I 3,'Rock Chemistry Database'! $A:$CE,1,FALSE)),VLOOKUP($J3,'Rock Chemistry Database'!$A:$CE,1,FALSE)),VLOOK UP($K3,'Rock Chemistry Database'!$A:$CE,1,FALSE)),VLOOKUP($L3,'Rock Chemistry Database'!$A:$CE,1,FALSE)).

[0059] Fifth, calculate the weighted average SiO2 value based on the thickness proportion of each lithology in the geological unit. Multiply the SiO2 content of each lithology in the geological unit by the sum of their thicknesses (Σcontent*thickness) and divide by the sum of the thicknesses of each lithology (Σthickness) to obtain the weighted average SiO2 value (SiO2_weighted_avg) of the geological unit.

[0060] Sixth, generate visualized geochemical maps based on GIS. Using the "join" function in ArcGIS, the spatial database of geological units is associated with geological units containing SiO2, such as... Figure 7 and 8 As shown. Based on SiO2 content, different tuples in the geological unit spatial database are assigned different colors to generate a visualized geochemical map, which intuitively reflects the SiO2 content of each geological unit, such as... Figure 9 As shown.

[0061] Although specific technical solutions of the present invention have been described in detail through embodiments and application examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the present invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for creating geochemical maps of exposed crustal rocks, characterized in that, Includes the following steps: (1) Constructing a multi-source database: Elemental content data of rock samples were collected. Based on the lithology, tectonic unit, geological age and geological unit of the rock samples, nine levels of search attributes were generated. The average elemental content of the samples corresponding to each search attribute was calculated to obtain a rock chemistry database. Data containing the names of geological units and their spatial distribution information is extracted from digital geological maps to obtain a database of the spatial distribution of geological units. By integrating geological unit names, lithology, lithological thickness, and nine levels of search attributes corresponding to the petrochemical database, a geological unit structure database is obtained. (2) Hierarchical attribute matching: For each tuple in the geological unit structure database, it is matched with the tuples in the petrochemical database in order of priority of the 9-level search attributes, starting with the highest precision attribute. If the match is successful, the element content data of the corresponding tuple in the petrochemical database is assigned to the current tuple in the geological unit structure database and the matching process is terminated. If the match fails, it continues to try to match the next level attribute until the match is successful or all 9 levels of attributes are traversed. (3) Calculate the weighted average elemental content of geological units: Based on the thickness proportion of each lithology in the geological unit, the thickness-weighted calculation of the element content of the successfully matched elements is performed to obtain the thickness-weighted average value of element content in each geological unit. (4) Generate geochemical maps: The elemental content and thickness weighted average of each geological unit are linked to the spatial distribution database of geological units. Geological units are then classified and colored according to elemental content using GIS tools to generate rock geochemical maps.

2. The method for mapping geochemical maps of exposed crustal rocks according to claim 1, characterized in that, In step (1), the generation method of the 9-level retrieval attributes is as follows: based on the fields of "primary lithology", "secondary lithology", "primary tectonic unit", "secondary tectonic unit", "geological age" and "geological unit" of the rock sample, the following are combined to generate "primary lithology", "secondary lithology", "primary tectonic unit - primary lithology", "primary tectonic unit - secondary lithology", "secondary tectonic unit - primary lithology", "secondary tectonic unit - secondary lithology", "secondary tectonic unit - age - secondary lithology", "geological unit - primary lithology", and "geological unit - secondary lithology".

3. The method for mapping geochemical maps of exposed crustal rocks according to claim 2, characterized in that, In step (2), the nine-level search attributes are arranged in descending order of matching precision as follows: "Geological unit - secondary lithology" → "Geological unit - primary lithology" → "Secondary tectonic unit - age - secondary lithology" → "Secondary tectonic unit - secondary lithology" → "Secondary tectonic unit - primary lithology" → "Primary tectonic unit - secondary lithology" → "Primary tectonic unit - primary lithology" → "Secondary lithology" → "Primary lithology".

4. The method for mapping geochemical maps of exposed crustal rocks according to claim 1, characterized in that, In step (3), the formula for calculating the elemental content thickness-weighted average of geological units is as follows: Among them, c i t represents the elemental content of the i-th lithology in a geological unit. i This represents the thickness of the i-th type of lithology.

5. The method for mapping geochemical maps of exposed crustal rocks according to claim 1, characterized in that: The data sources for the spatial distribution database of geological units include digital geological maps at scales of 1:200,000 to 1:2,500,000, and the lithological thickness data for the geological unit structure database are obtained from regional geological records or publicly available lithostratigraphic data.

6. The method for mapping geochemical maps of exposed crustal rocks according to claim 1, characterized in that: The samples in the rock chemistry database must cover all primary lithological types within the target area, and the number of samples must be no less than 30.

7. The method for mapping geochemical maps of exposed crustal rocks according to claim 1, characterized in that, In step (4), the specific operation of the GIS tool is as follows: the attribute table of the geological unit spatial distribution database is associated with the assigned element content data through spatial connection; the color levels are divided according to the element content value range, the geological unit polygons are filled with color, and a visual geochemical map is generated.

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