Chongli-Chicheng experimental area

In this section, the spectral characteristics of rock samples in Zhangjiakou experimental area of Hebei Province are studied and analyzed. The field rock spectral measurement was mainly carried out in May of 1997, when the plants in the experimental area just began to sprout, which brought a lot of convenience to the measurement. The measuring instrument is GER-IRIS-Ⅲ infrared intelligent spectrometer. The measuring time is 9:30- 17:30, mostly between 10:00- 15:00, and the illumination is generally above 40,000 lx. The vertical measurement height is about 100cm.

This survey adopts the method of combining profile and scattered points. According to the geological conditions and research purposes of the experimental area, after reconnaissance, a large lithologic section and four small sections (Figure 3-2- 1) were selected, namely the large section of Sitaizui-Chongli-Xishigou and the four small sections of Sandaogou, Dongping, Huang Tu and Paoliang, and some sporadic test points were added. Measure each feature for many times, observe and record the measurement parameters (measuring point position, date, time, sun angle, observation angle, etc.). ), weather state (weather, cloud cover, cloud shape, illumination, wind speed, wind direction, etc.). ), target characteristics (stratum, lithology, main mineral composition, color, particle size, etc. ), surface state (weathering degree, coverage, etc. More than 60 rock specimens or samples were collected, and the parallel light generated by 1000W halogen lamp was used as the incident light in the laboratory. The weathered surface and fresh surface of the samples were tested respectively, and the fresh section, rock and mineral identification and chemical analysis of some samples were carried out on 39 samples.

Fig. 3-2- 1 reflection spectrum of some sedimentary rocks in the experimental area

B35- 1- slightly metamorphic timely sandstone; B37-3- feldspar quartz siltstone; B35-2- striped dolomite; B36- 1- argillaceous thin dolomite; B29- 1- fault breccia; B29-2- Granite cataclastic rock; B23- 1- quartzite

In order to make up for the deficiency of field test of rock species, the reflection spectra of rock samples collected from different places are measured under natural lighting conditions for sporadic points or places where field test is difficult. 25 rock spectra were measured in different places.

3.2. 1.2 Spectral characteristics analysis of sedimentary rocks

Sedimentary rocks are mainly exposed in the southeast corner of the test area, and the measured lithology includes slightly metamorphic timely sandstone, feldspar quartzite, banded, striped and argillaceous dolomite, quartzite and so on. , some of which are fault breccia and granitic cataclastic rocks reconstructed or filled by faults (Table 3-2- 1 and Figure 3-2- 1).

The absorption zones of sedimentary rocks are mainly carbonate zones, strong absorption zones of hydroxyl and water produced by clay minerals, and wide and slow absorption zones of Fe3+ or Fe2+. Features are generally clear, but may be weakened by opaque minerals.

Feldspar quartzite siltstone (B37-3) contains 60% quartz, which is siliceous and cemented. Due to the high content of silica (9 1.54%), the spectral reflectance is high. Fe2+ can be seen in the weak absorption band of 0.95μm, and iron ions are clear in the absorption band of 0.5 μ m.. The hydroxyl band at 1.40μm widens in the long wave direction, which may be caused by the disordered distribution of OH-. The hydroxyl bands of 1.9μm and 2.2μm are obvious, and the hydroxyl bands of 2.35μm and 2.45μm are slightly distinguishable.

Table 3-2- 1 Spectral Characteristics of Some Sedimentary Rocks in Experimental Area

The mineral composition of feldspar quartz sandstone (B35- 1) is similar to B37-3, and the content of SiO2 _ 2 is as high as 96.72%. Fresh noodles are gray-white, mainly produced in the season, when most of the debris has been recrystallized, containing a small amount of feldspar and coarse particles. The overall reflectivity is extremely high, the absorption band features are clear and obvious, and the absorption intensity is high. The hydroxyl bands around 1.40μm, 1.9μm and 2.2μm are sharp, and the Fe2+ absorption band at 0.95μm is clear. The spectrum of fresh surface shows a weak band formed by Fe3+ decomposed from feldspar at 0.65μm m. The total spectral reflectivity of weathered surface and cut surface decreases.

The main mineral of dolomite (B35-2) is dolomite, which contains about 10% chlorophyll. Wide slow absorption bands caused by Fe2+ and Fe3+ ions can be seen at 0.5μm, 1.0μm and 0.7μm of the spectrum. The hydroxyl band at 1.4μm is weak and widened, while the absorption band at 1.9μm shifts to near 1.93μm in the long wave direction. Strong and wide bands indicate that there are more water molecules in the sample. The hydroxyl band is influenced by the 2.0μm carbonate band, forming a composite band. An abnormal water molecule band of about 2. 1μm can be seen in the spectrum of weathered surface. Due to the influence of Mg-OH band, the absorption peak of ions moves to around 2.30μm, and a strong and clear carbonate band is formed at 2.33μm, which basically masks the hydroxyl band at 2.2 μ m. ..

The reflectivity of sandstone and dolomite is generally high, about 75%. The absorption characteristics are very strong, with strong absorption at 1.4μm, 1.93μm and 2.20μm, indicating that they are not only rich in OH minerals and crystalline water molecules, but also in a highly ordered state. Due to the charge transfer of Fe-O, the reflection curves of these rocks drop sharply from about 0.50μm to Ranbo, and the absorption characteristics can be seen around 0.50μm and 0.80 μ m. ..

Quartzite (B23- 1) has electron transition bands of Fe3+ ions around 0.50μ m, 0.65μm and 0.93μm, and the absorption of 1.40μm, 1.92μm and 2.20μm is very strong, which means that quartzite contains crystal water inclusions and clay mineral Al-OH groups. Clear absorption bands can also be seen at 2.35μm and 2.45 μ m.

Felsic detritus of granitic cataclastic rock (B29-2) is cemented or filled with purplish red iron oxide. The fuchsia fault breccia (B29- 1) is similar in mineral composition, but its volume is relatively large, with a maximum of 5 ~ 6mm, and it is cemented by iron. Their spectral characteristics are similar: due to the influence of opaque minerals such as magnetite, the overall spectral contrast is not strong, the waveform is relatively flat, and the reflectivity is low, generally below 35%. Fe3+ forms absorption bands around 0.55μm, 0.65μm and 0.90 μ m.. The hydroxyl bands of 1.40μm and 1.93μm are faintly visible, the Al-OH band of 2.20μm is clear, and the hydroxyl bands of 2.35μm and 2.45μm are faintly distinguishable.

3.2. 1.3 Spectral characteristics of magmatic rocks and volcanic rocks

The magmatic rocks and volcanic rocks tested this time include amphibole, diorite, rhyolite, trachyandesite, amphibole, monzonite and syenite. Their weak spectral characteristics are shown in Table 3-2-2 and Figure 3-2-2.

Table 3-2-2 Spectral Characteristics of Main Magmatic Rocks and Volcanic Rocks in Experimental Area

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Figure 3-2-2 Reflection Spectra of Some Magmatic Rocks and Volcanic Rocks in Experimental Area

B33-1-granite; B38-1-diabase; B15-1-rhyolite; B10-1-chloritization monzonite; B 10-2- diopside amphibolite; B16-1-porphyritic coarse andesite; B8- 1 and b19-1-spherulite syenite plagioclase veins; B11-kloc-0/-adamellite; B7-1-quartz monzonite

The matrix of rhyolite (B 15- 1) is composed of microcrystalline feldspar and syenite, and porphyritic crystals are mainly orthoclase and syenite. The absorption band of 1.9μm is clear, while the absorption bands of 1.4μm and 2.2μm are weak, indicating that the clay mineral content is very small. The broad band and slow band around 0.45μm and 0.9μm are produced by trivalent iron oxide in the matrix, which is more obvious in the spectrum of weathered surface, and the Fe3+ absorption band around 0.7μm is also slightly distinguishable. The spectral shape of porphyritic dacite (B 16- 1) is very similar to rhyolite.

The cataclastic granite (B32- 1) has a flesh-red and porphyritic texture. The porphyritic crystals are mainly feldspar and syenite, and the matrix is potash feldspar, plagioclase and syenite, containing a small amount of dark minerals such as biotite and filled with altered minerals such as limonite. The absorption bands of 1.4μm and 1.93μm are strong, and the rocks may contain more liquid inclusion water. The absorption band of iron ion is obvious around 0.5μm, and the wide and slow absorption band around 0.7μm is caused by Fe3+. The wide and obvious band of 0.8 ~ 1.2 μ m should be the band of Fe3+ (content 3.02%) near 0.85μm and Fe3+ (content 1.22%) near/kloc-0. The hydroxyl absorption band is obvious near 2.2μm, mainly because feldspar erodes into high. The weak hydroxyl association bands at 2.3μm and 2.35μm may be the result of the corrosion of trace biotite into chlorite.

Granite (B33- 1) is mainly composed of potash feldspar, plagioclase and syenite, with granite structure. After 65438 0.4 μ m, the spectral morphology is similar to that of broken granite. The absorption bands of Fe3+(0.85μm) and Fe2+(0.95μm) in the cross-sectional spectrum are well separated, but the absorption bands are weak, indicating that the iron content is less (about 0.77%). In the natural spectrum, Fe2+ bands with peaks of 0.45μm and 0.5μm can be seen, and the reflectivity drops sharply from 0.75μm to short wave direction. The strong absorption of 2.2μm is also caused by kaolin. Due to the low iron content, the overall reflectivity is obviously higher than that of broken granite.

The adamellite (B 1 1- 1), like granite (B33- 1), has strong spectral bands at 1.40μm, 1.93μm and 2.20μm, indicating that granite.

The main mineral components of quartz monzonite (B 10-3) are plagioclase, microcline and about 5% quartz time. The spectrum is relatively flat, with obvious absorption characteristics at 1.9μm, weak absorption band at 1.4μm, and weak hydroxyl bands near 2.2μm and 2.3μm, which are caused by trace amounts of kaolinite, chlorite and epidote. The weak band caused by Fe2+ can be seen around 0.45μm and 0.9 μ m. The weak band at 2.35μm may be an accompanying band caused by hydroxyl groups at different positions.

Plagioclase and potash feldspar are embedded in chloritization monzonite (B 10- 1), accounting for 90% of the total, and contain pyroxene and a small amount of accessory minerals such as apatite and magnetite. Plagioclase and pyroxene have been partially chloritization. In the spectrum, the absorption band of 1.9μm is obvious, while the absorption band of 1.4μm and the absorption bands of hydroxyl groups at 2.2μm and 2.30μm are very weak. There is a weak hydroxyl absorption band caused by chlorite at 2.35 μ m, and the absorption band of Fe3+ at 0.45μm is obvious, but the absorption bands of other iron ions are not obvious.

The main minerals of spherulite syenite (B8- 1) are round spherulite syenite aggregate and a small amount of dark minerals. The weak absorption bands of water and hydroxyl groups are obvious at 1.4μm, 1.93μm and 2.2 μ m. The broad band and slow band of 0.7μm Fe3+ and 0.95μm Fe2+ are clear, and obvious iron ion band can be seen at 0.5μm, indicating that the rock is rich in iron. There are weak hydroxyl association bands at 2.35μm and 2.45 μ m.

Porphyry coarse andesite (B 16- 1) is brownish gray. The authigenic phenocrysts include plagioclase, altered amphibole and pyroxene. The matrix is microcrystalline plagioclase, orthoclase and glassy, and a small amount of magnetite is filled. The spectral curve is relatively flat, and the aggregation of a large number of dark opaque minerals reduces the overall reflectivity and contrast of the rock, but the bands of hydroxyl and water around 1.4μm, 1.9μm, 2.2μm and 2.35μm are still visible, and the bands of iron ions are weak.

The fresh surface of diopside (B38- 1) is grayish green with diopside content of 90%. It can be seen that magnetite is filled in diopside particles or cracks in veins. In the spectrum, the Fe2+ band around 1.05μm is deep, and the Fe3+ band around 0.78μm is weak. There are no water and hydroxyl absorption bands in the fresh surface spectrum, and the hydroxyl bands of 1.4μm, 1.93μm, 2.3μm and 2.4μm in the weathered surface spectrum are faintly visible. In the spectrum of weathered surface, the reflectivity from 0.55μm to blue wavelength region drops sharply, which is caused by Fe3+, while in the spectrum of fresh surface and section, the absorption band of Fe2+ is shown at 0.45 μ m. ..

Diopside amphibole (B 10-2) is dark green, mainly composed of common amphibole (about 45%), plagioclase (about 30%) and diopside (about 15%). The waveform is similar to that of diabase (B38- 1), with low reflectivity and no obvious banded features. Only the water molecule band of 1.9μm, the hydroxyl band of 2.3μm and 2.4μm are obvious (natural surface), and the Fe3+ band of 0.7μm and the Fe2+ band around 0.9μm are only obvious in the cross-sectional spectrum.

Spherical syenite (B 19- 1) has a clear wave band, which is stronger at 0.48μm, 0.93μm, 1.40μm and 1.93μm, followed by 2.20μm and weaker at 2.30μm and 0.65 μm m.

Fine-grained quartz monzonite (B7- 1) has a high reflectivity of about 70%, and the reflectivity drops sharply from 0.60μm to short wave direction. The wide and deep bands of 1.40μm and 1.93μm indicate that the rocks contain a lot of liquid water inclusions, and the bands of 2.20μm and 2.30μm are very obvious, which are caused by clay minerals such as kaolinite and chlorite.

Granite, adamellite, syenite and quartz monzonite have similar waveforms and relatively high reflectivity.

Silica tetrahedron, the main component of magmatic rocks, has no spectral characteristics, and its spectral characteristics are all produced by other components in the rock, such as iron, hydroxyl and water, which produce electronic characteristics. They can exist in many forms in rocks, but they are not directly related to the basic molecular structure of magmatic rocks.

Magmatic rocks range from basic to neutral to acidic. Generally, the content of iron ions decreases gradually, the band of iron weakens gradually, and the band of hydroxyl and water increases rapidly. In basic and ultrabasic rocks, 1.4μm and 1.9μm absorption bands of hydroxyl and water are rare. However, the reflectivity increases with the increase of SiO _ 2 content, and the wavelength position of the highest point of the spectral curve moves to the long wave direction with the increase of SiO _ 2 content. With the enhancement of reflectivity contrast, the band intensities (depth and width) around 1.40μm, 1.93μm, 2.20μm and 2.30μm also become more prominent.

3.2. 1.4 Spectral characteristics of metamorphic rocks

Metamorphic rocks are mainly distributed in Archean Chongli Group and Proterozoic Hongqi Ruth Group in the north of this area. The main rocks tested are gneiss, metamorphic diorite, schist, marble and quartzite.

Muscovite quartz schist (B23-2), the scales of muscovite are aligned with the time, and sometimes muscovite gathers into thin slices to form a strip dominated by it. The spectra of water and hydroxyl groups are obvious between 1.4μm, 1.9μm and 2.2 ~ 2.5 μ m, with weak bands at 1. 1.35 μm and 2. 1.2 μm, and Fe2+ is around 0.95 μ m.

The spectral shapes of gneiss are similar, and the overall reflectivity is about 30%. The main minerals of biotite amphibole gneiss (B39- 1) are common amphibole (35%), plagioclase (50%) and syenite (10%), and a small amount of biotite comes from chloritization. There are obvious water and hydroxyl bands at 1.4μm, 1.9μm, 2.2μm and 2.35 μ m. A weak absorption peak can be seen at the weathering surface spectrum 1.5μm, which may be an abnormal band caused by water molecules at different positions. The spectral bandwidth of Fe3+ transition at 0.93μm is slow, and the spectral band at 0.45μm is caused by Fe. The reflectivity of 0.70μm drops sharply in the short wave direction.

Amphibole biotite plagioclase gneiss (B20- 1) is composed of common amphibole, biotite and plagioclase, with a quartz content of 15%, and epidote and chlorite are filled with cracks along the direction of gneiss. The Fe3+ band of 0.7μm is more obvious than that of biotite plagioclase gneiss, indicating that the Fe3+ content is higher, and a wide and gentle Fe band appears at 0.95 μ m. The band at 2.3μm is obviously stronger than that at 2.2μm, indicating that the hydroxyl groups in the sample are mainly coordinated around magnesium. The hydroxyl groups and water bands of 1.4μm and 1.9μm are obvious, but the bandwidth of 1.4μm is widened, which may be caused by the orientation of hydroxyl groups in biotite. The iron ion band is obvious around 0.47 μ m.

Graphite-bearing garnet amphibole biotite plagioclase gneiss (B34- 1) contains opaque minerals such as graphite, which affects the performance of spectral band to some extent, especially in cross-section spectrum, and the overall reflectivity is low. In the natural surface spectrum, the bands of 1.4μm and 1.9μm can be seen. The coordination spectrum bandwidth of hydroxyl around magnesium is slow around 2.3μm, the absorption spectrum of Fe is strong and clear around 0.95μm, and the band of iron ion is obvious at 0.5 μ m.

The spectral characteristics of hypodiopside amphibole (B4- 1) are very similar to those of diopside amphibole (B 10-2), but the spectral absorption characteristics of the cross section are obvious. The spectral absorption characteristics of the cut surface and fresh surface at 1.9μm are far less obvious than those of the weathered surface, indicating that the weathered surface contains more water molecules, and the abnormal hydroxyl band at 2. 1μm visible in the cut surface spectrum is very weak in the natural surface spectrum. The hydroxyl bands at 2.3μm and 2.4μm are all shown, but only the weak bands of iron ions can be seen in the cross-sectional spectrum. The natural surface contains more opaque substances, which inhibits the spectral characteristics of the sample.

Table 3-2-3 Spectral Characteristics of Some Metamorphic Rocks in Experimental Area

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Serpentine marble (B4-3) of Chongli Rock Group (ArCl) is grayish white, mainly composed of dolomite and calcite, with serpentine content of 20%. The characteristic bands of iron in serpentine are visible around 0.45μm and 0.95 μ m, and the carbonate band of 2.35μm is very obvious, showing its unique shoulder peak on the short wavelength side. Due to the influence of Mg-OH group in serpentine, this band has double peaks, and the absorption near 2.30μm is extremely weak. There is another weak band of carbonate at 2. 1.4μm, and the band at 1.4 μm is strong and sharp, which indicates that the crystal lattice contains more structural water and is a highly ordered octahedron structure. There is a broad and strong absorption characteristic at1.9 ~ 2.0 μm, which consists of hydroxyl band at 1.9μm and carbonate band near 1.9μm and 2.0 μ m.

The white marble (B2 1- 1) of the Hongqiying subgroup (Pt 1Hq) contains 100% calcite. The shape of the spectral curve is similar to that of serpentine marble, but the reflectivity is about 20% higher. The absorption depth and width are strong at 1.93μm and 2.35μm, and the absorption spectrum near 1.40μm is wide and shallow, showing typical characteristics.

The reflectivity of metamorphic diorite (B 1- 1) and sericitized metamorphic diorite (B2- 1) is relatively low, generally around 20%. In the range of 0.40 ~1.85 μ m, the shapes of spectral curves are very similar. The bands of 0.48μm, 1.40μm, 1.90μm and 2.35μm are obvious, but the vibration band of 2.25μmMg-OH is stronger because of the high sericite content in the latter. The band of 0.48μm and the broad and shallow band around 1.0μm are caused by Fe2+.

The content of muscovite quartz schist (B23-2) muscovite (K {Al2 [Alsi3O 10] (OH) 2}) is 20% ~ 30%. The spectrum is basically similar to diorite, but the reflectivity is about 10% higher. The bands of 0.48μm, 0.65μm, 0.93μm, 1.40μm, 1.93μm, 2.20μm, 2.35μm and 2.45μm are clearly visible. 1.40μm and 2.20μm are deep and sharp, which are caused by the structural water molecules and Al-OH groups of muscovite.

To sum up, with the metamorphism from shallow to deep, the characteristics of spectral bands are generally gradually strengthened, with the spectral bands of 2.20μm and 2.33μm being the most prominent. Spectral characteristics (sharpness, depth, double peaks, etc. The marble in different periods in this area is very different, which shows that the metamorphic conditions are very different. The marble of Hongqiying subgroup is pure, white and has high reflectivity, which has typical absorption characteristics of carbonate ions. The marble of Chongli Group is grayish white, and the spectral characteristics of altered minerals (serpentine) are obvious. The sharp absorption peak near 1.40μm indicates that the rock contains highly ordered structural water (OH-), which is distributed in the position corresponding to the sixth octahedral coordination of mineral crystals, and its metamorphic temperature is lower than that of the marble of Hongqi Ruth Group.

Figure 3-2-3 Reflection Spectrum of Some Metamorphic Rocks in Experimental Area

B21-1-white marble; B23-2- muscovite quartz schist; B3-9- plagioclase amphibolite gneiss with dark clouds; B20-1-amphibole biotite plagioclase gneiss; B 1- 1- metamorphic diorite; B2- 1- fine sericitized metamorphic diorite; B4-3- serpentine marble; B34-1-granite amphibole biotite plagioclase gneiss; B4-2-Sub-permeable amphibolite plagioclase gneiss; B 18- 1- biotite plagioclase gneiss

3.2. 1.5 Spectral characteristics of ores and altered rocks

The ore and main surrounding rocks of hematite, Dongping Gold Mine, Huangtuliang Gold Mine and Sandaogou Polymetallic Lead-zinc Mine were tested by spectrum, and the spectral characteristics of rocks and minerals in each mining area were analyzed respectively (Table 3-2-4).

3.2. 1.5. 1 Dongping gold mine area

The genetic type is multi-source hydrothermal time pulse type. In Yingshi 1 vein, gold mainly occurs in Yingshi vein, the host rock is quartz monzonite, and the wall rock alteration is mainly potassium, chloritization, pyritization, sericite kaolin and silicification. Figure 3-2-4 shows the rock and mineral spectrum measured along the section passing through vein 1. The overall spectral characteristics of veins, altered rocks and surrounding rocks are similar, and the absorption bands around 0.93μm, 1.40μm and 1.93μm weaken from ore to surrounding rocks in turn, indicating that from veins to altered rocks and then to surrounding rocks, water molecules in rocks change from highly ordered state to disordered state, structural water components decrease and crystal water increases. The change of absorption characteristics around 2.20μm shows that sericite-kaolinite, an altered mineral containing Al-OH, decreases in turn, and silicification and potassium become weak. The absorption characteristics of about 2.30μm show that the minerals (chlorite) containing Mg-OH groups increase in turn. The degree of chloritization becomes stronger (except the surrounding rock). See Table 3-2-5 for changes of alteration types in the alteration zone of this gold mine.

Table 3-2-4 Spectral Characteristics of Ores and Mineralized Altered Rocks in Experimental Area

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Table 3-2-5 Changes of Alteration Zone Types in Dongping Gold Mine

3.2. 1.5.2 huangtuliang gold mine area

The genetic type is hydrothermal, and gold occurs in pyritized potassium feldspar veins. The alteration types are potassium alteration, pyrite alteration and surface limonite alteration. The surrounding rock is purple feldspar timely sandstone and the rock mass is porphyritic granite (B32- 1). The spectrum is shown in Figure 3-2-5.

Carbonated and pyritized potassium feldspar veins (B27-3 and B27-4) are developed in the fractures of microcline and felsic aggregates. Chemical analysis shows that the content of Fe2+ in the sample is almost twice that of Fe3+. The spectral bandwidth of Fe2+ is deep at 1.0μm, and its long-wave edge extends to 1.35μm, forming a wide absorption valley extending from 0.75μm to 1.35 μ m, and the spectral band of Fe2+ is obvious at 0.43μm and that of Fe3+ at 0.7 μ m. In the short wave direction, the reflectivity at 0.65μm drops sharply. The absorption band is obvious at 2.35μm, but there is no shoulder peak on the short wavelength side of carbonate absorption band, which may be caused by the compound action of carbonate and hydroxyl accompanying band. The hydroxyl band of 1.4μm is weakly influenced by Fe2+ band, but it can still be identified. The water characteristic band of 1.93μm is strong, which indicates that the water molecules in gold ore may be disordered crystal water. The hydroxyl bands around 2.20μm and 2.30μm are strong and sharp, which are caused by Al-OH and Mg-OH groups in altered minerals such as kaolinite, sericite (or muscovite), chlorite and epidote. The spectrum of weathered surface shows that there is a weak hydroxyl association band near 2.45 μ m.

Figure 3-2-4 Reflection Spectrum Curve of Ore and Surrounding Rock in Dongping Gold Mine

B24- 1- auriferous quartz vein; B25-1-silicified fine-grained feldspar veins; B24-2- plagioclase dike; B24-3- adamellite vein; B6- 1- Kaolinized syenite

Figure 3-2-5 Reflection Spectrum of Ore and Surrounding Rock in Huangtuliang Gold Mining Area

B27-3 and B27-4- carbonized and pyritized potash feldspar veins; B27- 1- limonite and pyritized potassium feldspar veins; B27-2- limonite potassium vein; B32-1-porphyritic granite; B29-2 —— Granitic cataclastic rock

Limonite-pyrite-pyrite-sylvite vein (B27- 1) is mainly composed of microcline, with developed reticular fractures, filled with limonite and pyrite, and containing 5.01%Fe2O3. Pyrite is not found in limonite-sylvite vein (B27-2), and the content of Fe2O3 is 6.05%. Their spectral morphology and band characteristics are similar. Fe2+ and Fe3+ have strong absorption bands at 0.47μm, 0.7μm and 0.95 μ m. The strong absorption of 1.93μm and the weak absorption of 1.40μm indicate that the altered ore contains crystal water, which may be in a disordered position. The 2.20μm band is very clear, but the 2.30μm band is very weak and almost unrecognizable, indicating the existence of kaolinite produced by weathering of potash feldspar. There are two weak hydroxyl association zones in limonite veins at 2.35μm and 2.45 μ m.

The late Hercynian porphyry granite (B32- 1) has obvious iron ion zone. The strong band and weak band of 1.90μm and 1.40μm indicate that the crystal water may be in a disordered position. The moderately weak absorption of 2.20μm is caused by altered minerals (potassium) containing Al-OH groups (see description of magmatic rocks). The spectral characteristics of granitic cataclastic rock (B29-2) are described in sedimentary rocks.

The potash, pyrite and chloritization zones of primary gold deposits in this area are obvious. The limonite zone and potassium zone of oxidized gold ore are very obvious, but the chloritization zone is very weak. There are limonite and potash zones in the rock mass; There are obvious potash, chloritization and weak limonite belts in the surrounding rocks; The strong absorption peak of 1.93μm and the weak absorption peak of 1.40μm indicate that water molecules exist in the form of crystal water. Compared with Dongping gold mine, the band of 1.40 is weak but not sharp, which may indicate that its metallogenic temperature is higher than Dongping gold mine.

3.2. 1.5.3 Sandaogou polymetallic mining area

Located in the gneiss of Paleoproterozoic Hongqiyingzi Group on both sides of Chicheng-Chongli east-west fault, it is mainly controlled by NW-trending compressive and shear faults. On the surface of vein II, the ore, altered rock and surrounding rock of lead-zinc polymetallic ore are studied by spectrum, and the spectral characteristics are shown in Figure 3-2-6.

Figure 3-2-6 Reflection Spectrum of Ore and Surrounding Rock in Sandaogou Polymetallic Mining Area

B26-3, B26-4— Brass-pyrite; B26-5 and B26-6- lead-zinc mine; B26- 1- strongly sericitized granite; B26-7- pyritized sericite; B26-2 —— Limonite-mineralized broken rock; B28-1-granite gneiss; B 17- 1- spherical coarse andesite

The spectral curves of brass-pyrite (B26-3, B26-4) are relatively flat, and the reflectivity is generally around 20%. B26-4 can see wide and gentle Fe3+ ion band and Fe2+ ion band at 0.45μm near 0.93μm, and weak bands appear near 1.93μm, 2.20μm and 2.33 μ m. The typical Fe2+ band of B26-3 is very wide near1.0 μ m., Very weak bands can also be seen around 1.40μm, 1.93μm, 2.20μm and 2.33μm, and the Cu2+ ion band around 0.80μm is covered by the iron ion band, which is not shown in the curve.

The reflection spectrum curves of lead-zinc ores (B26-5 and B26-6) are straight, and the curves show a slight downward trend. The band characteristics are not obvious. The spectrum of B26-6 has an obvious weak band near1.20μ m. The optical identification results show that both samples contain a small amount of wrapped tetrahedrite ([Ag] Cu 12SBS 13), but the spectrum of B26-5 does not have this band. Therefore, this may be due to the fact that nickel divalent ions in nickel tetrahedrite allow electron spin transition. The latter explanation seems more reasonable (Institute of Information, Ministry of Geology, 1980).

The feldspar in strongly sericitized granite (B26- 1) has been completely altered into sericite muscovite, which contains kaolinite and some dark brown and yellow opaque minerals, mainly the aggregate of limonite and pyrite, and may be the alteration product of iron and magnesium minerals. The spectral absorption characteristics are strong and obvious. The bands at 1.45μm and 1.93μm are deep and sharp, indicating that the rocks contain highly ordered structural water (H2O2 2.84%), and their formation temperature may be low. The bending vibration of sericitized (Al2O3 16. 18%) octahedral Al-OH at 2.2μm produces a sharp band, which is obviously different from that of chlorite and epidote Mg-OH at 2.35μm and 2.45 μ m. The high content of iron intensifies the sharp attenuation of the spectrum from 0.55μm to the blue wavelength direction. There are obvious Fe ~ (2+) bands at 0.44μm and 0.5μm, and the Fe ~ (3+) band near 0.95μm is strong and wide, extending to the near infrared region, forming an obvious boundary with the hydroxyl 1.4 μ m band. ..

Pyritized sericite (B26-7) is mainly composed of sericite and muscovite, and pyrite is self-crystallized, accounting for about 0/5% ~ 20% of/kloc-. Pyrite spectrum has no obvious characteristics, and the wide and slow band centered at 0.93μm may be affected by trace Fe3+ or other impurities. The absorption band of Fe2+ at 0.453μm can be seen in the fresh surface spectrum. The bands of water and hydroxyl groups at 1.4μm, 1.9μm, 2.2μm, 2.30μm and 2.45μm are clear.

Limonite fractured rock (B26-2) is highly limonitized, with a content of about 65,438+00%, and it is distributed in a gelatinous aggregate along rock fractures and mica cleavage. Fe3+ ion is strong and wide in the spectral band of 0.93 micron, and its tail extends to the near infrared region. The Fe3+ band of 0.68μm is very weak, and the Fe2+ band of 0.47μm is also very clear. The spectral bands of cut surface and weathered surface are 1.45μm and 1.93μm, respectively, indicating that there are a large number of crystalline water molecules, and the hydroxyl band at 2.2μm is very obvious. However, the hydroxyl band of fresh noodles after 2.0μm is very weak.

The surrounding rock granite gneiss (B28- 1) has a moderate spectrum, with Fe3+ band of 0.93μm, Fe2+ band of 0.5 1μm, crystal water bands of 1.40 and 1.93 μ m .. Al-OH and Mg.

From the above analysis, it can be seen that due to the pollution of opaque pyrite and galena, the ore reflectivity of this polymetallic ore is low and the absorption band is suppressed; The spectral characteristics in altered rocks are relatively strong. According to the strong and sharp band characteristics of 1.40μm, the metallogenic temperature is lower than that of Dongping and Huangtuliang gold deposits.