*2.4.1 Conversion of data format*

The geochemical data obtained from the Daxinganling Mountains were stored in Microsoft XLS format, and 39 elements (oxide) data was included. The arrangement of single elements' data is based on the seriation of the first letters and then followed by oxide. The whole arrangement order is as follows: Ag, As, Au, B, Ba, Be, Bi, Cd, Co, Cr, Cu, F, Hg, La, Li, Mn, Mo, Nb, Ni, P, Pb, Sb, Sn, Sr, Th, Ti, U, V, W, Y, Zn, Zr, Al2O3, CaO, Fe2O3, K2O, MgO, Na2O, and SiO2. The oxides content were expressed in percentage; the unit of Au and Ag value is ppb. The units of other content values all were ppm. The geographic position was expressed in the format of geographic coordinates.

The file needs to be checked in the sorting way, to inspect whether unqualified data exists. The unqualified data site must be eliminated to ensure quality of the data. Because ENVI cannot directly recognize the file with Microsoft XLS format, the XLS files need to be transformed into TXT format. The latitude and longitude of coordinates were assigned at the first two columns respectively; the other elements were listed afterwards. In Microsoft Excel, the file was saved as TXT format. Additionally, it needs to be noted that if the data content of the geochemical exploration sampling sites is too large even exceeding the permission of Microsoft Excel software, then respectively they need to be else saved in other software, e.g., software Surfer 8 (Golden Software Inc., Golden, USA), to obtain the format that can be recognized by ENVI software. The latter case is suitable for the aeromagnetic data, in which data volume is enormous and usually exceeds the row range of Microsoft Excel software.

#### *2.4.2 Rasterizing geochemical data*

The geochemical data are rasterized by pull-down menu "Rasterize point data" in the ENVI software. The output projection was determined, and output X/Y size was selected as 1000 m, meaning the spatial resolution of the formed rasterized images is 1000 m. Linear interpolation (quintic polynomial) was chosen. Smooth quintic


#### **Figure 2.**

*Position of the elements measured by 1:2,000,000 regional geochemical survey in the periodic table, with shaded area as measured elements.*

**57**

**Figure 4.**

*image maps as pixels. Pixel size is 1000 m.*

**Figure 3.**

*is 1000 m.*

*The Geochemical Data Imaging and Application in Geoscience: Taking the Northern…*

mask the incorrect area, the buffer zones of sampling site were used.

polynomial interpolation is performed by giving binary interpolation of Z values and smooth surface fitting at points that are irregularly distributed on the X-Y plane. The interpolation function is a fifth-degree polynomial in X and Y in a triangular cell and each polynomial is determined by the given values of Z and estimated values of partial derivatives at the vertexes of the triangle [32]. After the above steps, the image of a single element can be formed. And in the same way, the images of 39 elements can be created. The sampling sites were irregular and the rasterized image covered a whole area in a rectangle in the process of rasterizing geochemical data (**Figure 3**). These inappropriate image contents can be eliminated by using the method of masking. To

The formation of the buffer zone is that the geochemical sampling sites were overlaid by the ROI (region of interest) sites. The overlaid 5231 sampling sites were shown in **Figure 4**. By contrast, the maximum distance assigned to 2 pixels is much better to generate buffer zone. Buffer zone image was used to create an image mask. Finally the incorrect area was masked to generate the geochemical content image (**Figure 5**).

*Original Ag element grid map of Manzhouli area cut from northern Daxinganling metallogenic belt. Pixel size* 

*Locations of sampling points in Manzhouli area. Sampling points were expressed in ROI and superposed on* 

*DOI: http://dx.doi.org/10.5772/intechopen.84725*

## *The Geochemical Data Imaging and Application in Geoscience: Taking the Northern… DOI: http://dx.doi.org/10.5772/intechopen.84725*

polynomial interpolation is performed by giving binary interpolation of Z values and smooth surface fitting at points that are irregularly distributed on the X-Y plane. The interpolation function is a fifth-degree polynomial in X and Y in a triangular cell and each polynomial is determined by the given values of Z and estimated values of partial derivatives at the vertexes of the triangle [32]. After the above steps, the image of a single element can be formed. And in the same way, the images of 39 elements can be created.

The sampling sites were irregular and the rasterized image covered a whole area in a rectangle in the process of rasterizing geochemical data (**Figure 3**). These inappropriate image contents can be eliminated by using the method of masking. To mask the incorrect area, the buffer zones of sampling site were used.

The formation of the buffer zone is that the geochemical sampling sites were overlaid by the ROI (region of interest) sites. The overlaid 5231 sampling sites were shown in **Figure 4**. By contrast, the maximum distance assigned to 2 pixels is much better to generate buffer zone. Buffer zone image was used to create an image mask. Finally the incorrect area was masked to generate the geochemical content image (**Figure 5**).

#### **Figure 3.**

*Applied Geochemistry with Case Studies on Geological Formations, Exploration Techniques…*

The remote sensing software can be used for the point rastering; most of the data processing and interpretation can be accomplished. In this study, the whole process was completed through using the ENVI software (V. 4.4, Research System

The geochemical data obtained from the Daxinganling Mountains were stored in Microsoft XLS format, and 39 elements (oxide) data was included. The arrangement of single elements' data is based on the seriation of the first letters and then followed by oxide. The whole arrangement order is as follows: Ag, As, Au, B, Ba, Be, Bi, Cd, Co, Cr, Cu, F, Hg, La, Li, Mn, Mo, Nb, Ni, P, Pb, Sb, Sn, Sr, Th, Ti, U, V, W, Y, Zn, Zr, Al2O3, CaO, Fe2O3, K2O, MgO, Na2O, and SiO2. The oxides content were expressed in percentage; the unit of Au and Ag value is ppb. The units of other content values all were ppm. The geographic position was expressed in the format of geographic coordinates. The file needs to be checked in the sorting way, to inspect whether unqualified data exists. The unqualified data site must be eliminated to ensure quality of the data. Because ENVI cannot directly recognize the file with Microsoft XLS format, the XLS files need to be transformed into TXT format. The latitude and longitude of coordinates were assigned at the first two columns respectively; the other elements were listed afterwards. In Microsoft Excel, the file was saved as TXT format. Additionally, it needs to be noted that if the data content of the geochemical exploration sampling sites is too large even exceeding the permission of Microsoft Excel software, then respectively they need to be else saved in other software, e.g., software Surfer 8 (Golden Software Inc., Golden, USA), to obtain the format that can be recognized by ENVI software. The latter case is suitable for the aeromagnetic data, in which data volume is enormous and usually exceeds the row range of Microsoft Excel software.

The geochemical data are rasterized by pull-down menu "Rasterize point data" in the ENVI software. The output projection was determined, and output X/Y size was selected as 1000 m, meaning the spatial resolution of the formed rasterized images is 1000 m. Linear interpolation (quintic polynomial) was chosen. Smooth quintic

*Position of the elements measured by 1:2,000,000 regional geochemical survey in the periodic table, with shaded* 

**2.4 Geochemical data rasterizing method**

Inc., Boulder, CO, USA).

*2.4.1 Conversion of data format*

*2.4.2 Rasterizing geochemical data*

**56**

**Figure 2.**

*area as measured elements.*

*Original Ag element grid map of Manzhouli area cut from northern Daxinganling metallogenic belt. Pixel size is 1000 m.*

#### **Figure 4.**

*Locations of sampling points in Manzhouli area. Sampling points were expressed in ROI and superposed on image maps as pixels. Pixel size is 1000 m.*

**Figure 5.** *Rasterized image of Ag element after a buffer zone mask.*
