In this study, the number of absorption peaks of the SWIR spectral curves of sixty specimens in the five wavelength ranges of 1380–1430 nm, 1630–1660 nm, 1880–1950 nm, 2170–2230 nm, and 2230–2380 nm are calculated. The specimens DK10-23, SK24-10 and DK10-22 are introduced as examples for introduction.
The SWIR spectral curve of the specimen DK10-23 is shown in Fig. 5(a). There are two absorption peaks, which are located at 1416 nm and 2220 nm respectively. The SWIR spectral curve of the specimen SK24-10 is shown in Fig. 5(b). There are three absorption peaks, which are located at 1412 nm, 1910nm and 2220 nm respectively. The SWIR spectral curve of the specimen DK10-22 is shown in Fig. 5(c). There are four absorption peaks, which are located at 1414 nm, 1910nm, 2210 nm and 2354 nm respectively.
The SWIR spectral curves of the remaining 57 specimens are shown in Fig. 6(a)-(be).
The number of absorption peaks of the SWIR spectral curves in the five wavelength ranges and UCS of the sixty altered rock specimens are calculated, as shown in Table 1.
Table 1
The number of absorption peaks of SWIR spectral curves in the five wavelength ranges and UCS of the sixty altered rock specimens
No. | Wavelength of absorption peaks/nm | Number of absorption peaks | UCS/MPa |
DK10-22 | 1414, 1910, 2210, 2354 | 4 | 143.2 |
DK10-23 | 1916, 2220 | 2 | 144.0 |
DXK1-2 | 1922 | 1 | 96.8 |
SK24-10 | 1412, 1910, 2206 | 3 | 75.7 |
SK24-11 | 1910, 2206 | 2 | 152.8 |
SK24-12 | 1414, 1910, 2206 | 3 | 53.2 |
SK24-13 | 1414, 1912, 2208 | 3 | 54.2 |
SK24-14 | 1414, 1910, 2206 | 3 | 78.3 |
SK24-14-1 | 1414, 1912, 2208 | 3 | 31.6 |
SK31-1-1-1 | 1912, 2220 | 2 | 159.9 |
SK31-1-1-2 | 1926, 2214 | 2 | 166.7 |
SK31-1-2 | 1916, 2210 | 2 | 179.2 |
SK31-1-3 | 1414, 1912, 2218 | 3 | 46.3 |
SK31-1-6 | 1416, 1912, 2216 | 3 | 81.2 |
SK31-1-7 | 1414, 1912, 2216, 2348 | 4 | 106.9 |
SK31-1-14 | 1414, 1912, 2208 | 3 | 44.3 |
SK31-1-15-1 | 1416, 1914, 2214, 2342 | 4 | 130.2 |
SK31-1-16 | 1414, 1912, 2210 | 3 | 41.0 |
SK31-1-19 | 1416, 1910, 2218 | 3 | 76.4 |
XK2-6 | 1414, 1912, 2208 | 3 | 64.4 |
XK2-6-1 | 1414, 1912, 2206 | 3 | 37.2 |
XK2-6-1-1 | 1414, 1912, 2208 | 3 | 76.5 |
XK6-8 | 1920, 2208 | 2 | 147.4 |
XK6-9 | 1412, 1910, 2204, 2346 | 4 | 152.6 |
XK6-10 | 1412, 1910, 2204 | 3 | 99.7 |
XK23-1 | 1414, 1912, 2220 | 3 | 73.0 |
XK23-2 | 1394, 1644, 1916, 2330 | 4 | 112.4 |
XK23-3 | 1394, 1642, 1916, 2342 | 4 | 63.2 |
XK23-4 | 1394, 1644, 1916, 2330 | 4 | 138.4 |
XK23-5 | 1394, 1646, 1916, 2330 | 4 | 114.2 |
XK23-7 | 1394, 1642, 1916, 2326 | 4 | 131.2 |
XK23-8 | 1394, 1646, 1914, 2329 | 4 | 129.1 |
XK23-8-1 | 1394, 1642, 1912, 2244 | 4 | 110.6 |
XK31-17 | 1412, 1910, 2204 | 3 | 19.9 |
YK3-1 | 1414, 1912, 2210 | 3 | 93.0 |
YK3-2 | 1414, 1912, 2208 | 3 | 34.4 |
YK3-3 | 1414, 1912, 2208 | 3 | 30.4 |
YK3-4 | 1416, 1912, 2216 | 3 | 58.6 |
YK3-5 | 1416, 1910, 2214 | 3 | 88.9 |
YK3-8 | 1914, 2208 | 2 | 59.5 |
YK4-1 | 1416, 1912, 2212 | 3 | 39.9 |
YK7-1 | 1416, 1912, 2214 | 3 | 48.5 |
YK7-3 | 1414, 1912, 2212 | 3 | 16.8 |
YK10-3 | 1414, 1912, 2212 | 3 | 52.2 |
YK10-4 | 1416, 1912, 2214 | 3 | 102.1 |
YK10-6 | 1414, 1914, 2204 | 3 | 58.2 |
YK10-8 | 1414, 1910, 2206 | 3 | 69.3 |
YK10-11 | 1910, 2204 | 2 | 183.6 |
YK10-14 | 1414, 1908, 2208 | 3 | 87.9 |
YK10-22 | 1416, 1914, 2218, 2352 | 4 | 137.3 |
YK10-25 | 1416, 1912, 2218, 2350 | 4 | 156.3 |
YK10-27 | 1416, 1912, 2214, 2352 | 4 | 103.4 |
YK10-30 | 1414, 1910, 2213 | 3 | 83.1 |
YK10-34 | 1414, 1912, 2216 | 3 | 32.1 |
YK10-35 | 1414, 1912, 2206 | 3 | 59.6 |
YK10-36 | 1414, 1910, 2206 | 3 | 41.5 |
YK10-37 | 1416, 1912, 2216, 2348 | 4 | 142.4 |
YK10-38 | 1414, 1916, 2212, 2346 | 4 | 53.8 |
YK10-41 | 1414, 1912, 2212, 2348 | 4 | 90.7 |
YK10-43 | 1412, 1642, 1912, 2218 | 4 | 156.8 |
It can be seen from the Table 1 that, there is an obvious correlation between the number of absorption peaks in the five wavelength ranges of the SWIR spectral curves and the UCS of altered rock specimens.
The number of absorption peaks of the SWIR spectral curves of the eight specimens are two, and the absorption peaks exist in the two wavelength ranges of 1880–1950 nm and 2170–2230 nm. Among them, the UCS of five specimens are higher than 150 MPa, and the UCS of two specimens are slightly lower than 150 MPa (the UCS of specimens DK10-23 and XK6-8 are 144 MPa and 147.4 MPa, respectively).
The number of absorption peaks in the SWIR spectral curves of the thirty-three specimens are three, and the absorption peaks exist in the three wavelength ranges of 1380–1430 nm, 1880–1950 nm, 2170–2230 nm. Among them, the UCS of thirty-two specimens are lower than 100 MPa, and the UCS of specimen YK10-4 is 102.1 MPa (slightly higher than100 MPa).
The number of absorption peaks in the SWIR spectral curves of the eighteen specimens are four, among them, the UCS of twelve specimens are between 100–150 MPa, and the UCS of three specimens are slightly higher than 150 MPa (the UCS of specimens XK6-9, YK10-25, YK10-43 are 152.6 MPa, 156.3 MPa and 156.8 MPa, respectively).
The number of absorption peaks in the SWIR spectral curve of specimen DXK1-2 is one, and its UCS is 96.8 MPa.