Yingshi is a common rock-forming mineral and the most common gangue mineral. Synchrony exists in most hydrothermal deposits, especially in synchrony-type gold deposits and synchrony-type tungsten deposits, and synchrony is one of the most important minerals. Therefore, the time in these deposits, whether it is the spontaneous time of hydrothermal filling crystallization or the abnormal time produced in the process of wall rock replacement or alteration, must contain information related to mineralization. In addition to the commonly used information on the physical and chemical conditions of mineralization, such as hydrogen and oxygen isotopes, temperature, pressure and oxygen fugacity, these information also include the sources of ore-forming materials and fluids, metallogenic evolution process, mineralization zoning and so on. However, apart from the study of physical and chemical conditions of mineralization, there are relatively few studies on the material source, mineralization zoning and even how to guide ore prospecting from the perspective of timely minerals themselves.
Because SiO _ 2 is the main component in the earth's crust, its crystal structure and mineral chemical composition are relatively simple and stable, and it is the most ideal mineral for determining trace element content by neutron activation method. Many achievements have been accumulated at home and abroad in the determination of trace elements by neutron activation method (Li,1989; Guan Heguo,1991; Cao Zhimin,1991; Hu Chuyan et al.,1992; Qu Wenjun, et al., 1997), but there are few reports about chronotropic wolframite. Cao Zhimin (199 1) once conducted neutron activation analysis on the time of Huangjinping gold deposit in Dadu River, Sichuan Province. The results show that the content of ultra-fine gold dispersed in time is high in the upper part of the ore body, the highest is 6.7× 10-6, and the content decreases in the deep part. The exposed ore body of ZK30 1 hole should contain 0.65438 gold. It is difficult to form an independent gold ore body if there is no visible gold in the ore with less sulfide. The ratio of Ba/As is small in the upper part (< 36.7), large in the middle part (185 ~ 225) and small in the lower part (7.7), because the primary halo of gold mineralization generally takes Ba as the leading halo and As as as the tail halo, and the Mn content is related to the gold-rich deposits in the middle part of the Sixth System.
Gannan is the main producing area of quartz vein type tungsten ore, but there are also fracture zones-quartz vein type gold deposits. Timely veins are all over the surface of southern Jiangxi. Do these timely veins contain minerals? If so, what is their potential? Are they worthy of further study? These problems are both realistic and concrete. In this paper, the neutron activation method is used to make a preliminary comparative study between the typical time-dependent gold deposit (Liu Long gold deposit) and tungsten deposit (Taoxikeng tungsten-tin polymetallic deposit) in southern Jiangxi, and a very meaningful result is obtained, that is, not only the information of whether there is a mine in time, but also its ore-bearing property can be obtained, which provides a reference for the deployment of exploration work.
Second, the method and requirements
The methods and steps of neutron activation analysis of timely samples are briefly described as follows: the accurately weighed samples and reference materials are wrapped in high-pressure polyethylene film, put into an irradiation tube, and sent to the radiation tunnel in the micro-reactor of China Institute of Atomic Energy for irradiation. According to the different types of elements to be measured, short irradiation and long irradiation are selected for 2 minutes to 35 hours respectively. The neutron flux rate of the reactor is 2 ~ 8×1011n/s cm2. The irradiated samples and reference materials were cooled for different times, and the γ -ray radioactivity was measured by high purity germanium detector under the same geometric conditions. Among them, γ -ray energy spectrum analysis, various interference corrections and element content calculation are all completed by microcomputer γ -ray energy spectrometer system.
In this study, V 1 1 tungsten vein (one of the trump cards of Taoxikeng), Liu Long gold mine 10 gold vein (main vein) and some veins in Baxiannao and Mimeishan mining areas were sampled respectively, and pure timely single mineral samples were collected and selected for neutron activation analysis. Each sample can be determined at one time. Neutron activation analysis was completed by Qu Wenjun, a researcher at the National Geological Testing Center, after being irradiated by the China Institute of Atomic Energy. According to the analysis results, except about 0.2% Al2O3, the contents of other substances W, Ca, Mn, As, K, Na, Cr, Cs, Fe, Rb and Zn are all at the level of × 10-6, while Sb, Sm, Au, Ag, Ce, Co, Hf, Lu and Sc.
In addition, timely neutron activation test (NAA) can directly and accurately determine the main ore-forming elements such as W, Au, Ag, Pb, Zn and Sb (especially the sensitivity to Au is the highest among all methods), which has obvious advantages over other analysis methods.
Three. Timely Vein Gold Deposits —— Taking Liu Long Gold Deposit as an Example
1. Geological survey and sample representativeness
Liu Long gold deposit is the first medium-sized rock gold deposit with industrial value discovered and proved in southern Jiangxi. The mining area is located in Liu Long Township, 20km southeast of Xingguo County, at the junction of the SN- trending Yongfeng-Anyuan structural belt and the Neocathaysian Yushan structural belt. Faults are developed in this area, mainly SN- trending, EW-trending and NE-NNE-trending faults, which all control mineralization to varying degrees. Only vein-like and vein-like diabase and amphibole lamprophyre are found in the mining area, but there are frequent magmatic activities in the area, which are surrounded by granite bodies from early Caledonian to late Yanshan. Veins occur in metamorphic tuff, retrogradation tuff, metamorphic tuff sandstone and tuffaceous phyllite of Shangshi Formation in Lower Sinian. The deposit types are synchronous pulse type and synchronous compound pulse type. The known vein in the whole area is 3 1, the largest vein is 10, and the average gold grade of the whole vein is 8.31g/t. The main metal minerals are pyrite and arsenopyrite, and the gangue minerals are timely, sericite, chlorite and epidote. Gold minerals include natural gold, silver-gold ore and gold-silver ore, which are mainly produced in pyrite.
The research samples are taken from the main vein of Baxiannao mining area 10, and from the tungsten-bearing vein in time. At the same time, the contents of trace elements were determined by neutron activation method and compared.
2. Results and discussion
The results of timely neutron activation determination of Liu Long gold mine and Baxiannao time-dependent pulse deposit are listed in Table 8-4.
Table 8-4 Time-dependent Neutron Activation Analysis Results of Time-dependent Veins in Baxiannao Tungsten Mine and Liu Long Gold Mine.
Note: the unit is × 10-6. The samples containing LL are from Liu Long gold mine, and the rest are from Baxiannao tungsten mine. The Ag content in LLw-0 1 13 is 0.00652× 10-6, and that in V2H44-3Q is 0.0004 19× 10-6. The sulfide in the timely vein of Liu Long Gold Mine is mainly pyrite, and wolframite, scheelite, sphalerite and galena are not found. Besides wolframite, there are sphalerite, chalcopyrite and pyrite in the timely vein of Baxiannao tungsten mine.
3. Identification and traceability of genetic types
According to the preliminary analysis results, both Liu Long gold deposit and Baxiannao tungsten deposit belong to time-pulse type deposits, but their main minerals are different. Therefore, the information of trace elements contained in the timely vein is different, as follows:
1) As can be seen from the table, whether it is Liu Long gold mine or Baxiannao tungsten mine, the content of timely gold is very small, less than 0.03× 10-6. The accurate determination of such a low content of gold depends on the accuracy of neutron activation analysis. Among them, the average gold mine is 0.00776× 10-6, and the average tungsten mine is 0.00 192× 10-6, the former is four times that of the latter.
2) Compared with Jishi, the gold mining area is rich in chlorine, manganese, arsenic, antimony, iron, zinc and other elements, especially manganese, arsenic and antimony. This is consistent with the fact that arsenic, antimony, chlorine and other elements are often used as prospecting indicators for gold deposits. The contents of manganese and tungsten in Yingshi gold mine are higher than those in Yingshi tungsten mine. The reason remains to be further studied, or it may be due to the regional enrichment of tungsten in Nanling. No independent mineral of tungsten has been found in Liu Long Gold Mine, which makes it relatively enriched in the hot melt fluid represented by "Yingshi". The contents of K, Rb and Cs in the tungsten ore in Baxiannao are obviously higher than those in the gold ore, indicating that there is an obvious material source connection between tungsten ore and granite (rich in K, Rb and Cs).
3) From the perspective of element combination (Figure 8-5), in the Cl-Au diagram, Mn-Au diagram, As-Au diagram, Cs-Au diagram, Sc-Au diagram, Rb-Au diagram, Cl×Mn-As×La diagram and Cl×Mn-As×Sb diagram, the Au and Cl contents of timely gold deposits are obvious.
Fig. 8-5 Comparison of Time-dependent Neutron Activation Analysis between Baxiannao Yingshi Vein Tungsten Mine and Liu Long Yingshi Vein Gold Mine.
Fig. 8-6 Comparison of element combination products of timely neutron activation results between Baxiannao Yingshimei tungsten mine and Liu Long Yingshimei gold mine.
4) Taoxikeng and Baxiannao tungsten deposits, the former belongs to the time pulse of magmatic hydrothermal filling, and the latter belongs to the time pulse of altered rocks in the fracture zone. Comparatively speaking, they have obviously different grouping characteristics of trace elements. There are fewer kinds of trace elements in Baxiannao mining area, and the degree of correlation between different elements is different from Taoxikeng. Because the time-dependent samples in Taoxikeng are mainly collected from the filled time-dependent veins, the ore-forming fluid mainly comes from the magmatic hydrothermal solution differentiated from deep granite crystals, with many trace elements, which has the typical combination characteristics of magmatic hydrothermal ore-forming elements; The Baxiannao sample is also taken from the time pulse, but it mainly belongs to the time pulse filled with hydrothermal solution in the fracture zone, with obvious structural deformation characteristics, few trace elements and less direct display of magmatic hydrothermal characteristics. This can be clearly seen in the cluster analysis diagram. Tungsten in the eight immortals' brain is highly correlated with sulfide-loving elements (As, Sb, Fe, etc.). ), while W in Taoxikeng has the highest correlation with rare earth elements (Figure 8-7).
Fig. 8-7 R-cluster analysis results of timely neutron activation analysis, the left side is Baxiannao; On the right is Taoxikeng.
5) There is a strong correlation between timely tungsten content and reserves. This will be discussed below.
Generally speaking, the content of W in tungsten mine area changes greatly, which can be as high as 1000× 10-6, and the content of Au in gold mine area changes greatly and is high (as high as 6700× 10-9 in Huangjinping mine area of Sichuan). Cao Zhimin et al., 199 1).
For tungsten ore, there are also differences among Taoxikeng, Xiumeishan and Baxiannao (Figures 8-8 and 8-9). The iron content in Baxiannao changed little, but the aluminum content changed greatly (that is, the iron content and aluminum content in Xiumei Mountain remained basically unchanged), and the iron content and aluminum content in Taoxikeng mining area were positively correlated.
Fig. 8-8 W-Au relationship diagram of different types of chronological vein deposits.
Fig. 8-9 Al-Fe relationship diagram of tungsten ores with different types of chronological veins.
Four. Time-related vein tungsten deposits--taking taoxikeng as an example.
China quartz wolframite is world-famous, and quartz is the most common gangue mineral. As a pure mineral, Yingshi contains all kinds of information, which is very helpful to study the source of ore-forming materials, the properties of ore-forming fluids and mineralization zoning. Neutron activation analysis can obtain a variety of information, but in the past it was mostly used in gold mines and rare in tungsten mines. In this paper, a trump card tungsten vein of Taoxikeng tungsten mine in Chongyi County, southern Jiangxi Province is systematically analyzed and tested, and significant results are obtained.
1. Overview of geological characteristics and representativeness of samples The geological characteristics of Taoxikeng tungsten mine have been introduced in detail in the previous chapters, so they are not repeated here. In this study, the V 1 1 tungsten vein in Baoshan section of Taoxikeng mining area is one of the trump cards of Taoxikeng. Figure 8- 10) was systematically sampled, and 42 single mineral samples were collected and purified for neutron activation analysis, each containing 24 elements. Neutron activation analysis was completed by Qu Wenjun, a researcher at the National Geological Testing Center, after being irradiated by the China Institute of Atomic Energy.
V 1 1 The exposed length of the vein surface is 340 ~ 682 m, the dip angle is 250 ~ 660 m, the output elevation of the ore body is 690 ~-56m, and the lowest elevation has been controlled to -56m, but it is not pointed out. Mineralization belongs to time-related vein type, and wolframite locally occurs in greisen dikes or greisenized rocks. The pulse shape changes little, the pulse amplitude is stable and extends deeply. According to the working data of Gannan Geological Survey Brigade in this mining area, the elevation of V 1 1 vein in Baoshan section is from 356m to 106m, the thickness of ore body is increased from 0.3~0.5m to 1.7m, and the WO3 grade is gradually enriched from shallow to deep.
Figure 8- 104 Taoxikeng Line 10 (adapted from Gannan Geological Brigade)
2. Test results
According to the analysis results (Table 8-5), except for about 0.2% Al2O3, the contents of other substances W, Ca, Mn, As, K, Na, Cr, Cs, Fe, Rb and Zn in the time are all at the level of × 10-6, while Sb, Sm, Au, Ag, Ce and Zn are all at the same time.
Table 8-5 Time-dependent Neutron Activation Analysis Results of Taoxikeng V 1 1 Vein.
Note: the content unit of Al is%, the content unit of W, Ca, Mn, As, K, Na, Cr, Cs, Fe, Rb and Zn is × 10-6, and other elements are × 10-9.
3. Correlation analysis between elements
The elements in Taoxikeng are analyzed by R-cluster analysis and factor analysis, and the relevant information among the elements is obtained (Table 8-6 and Figure 8-9). As can be seen from Table 8-6, the element W has a good correlation with elements such as Sm, Lu, Yb, Mn, Sc, Ta, Fe, and the correlation coefficients are 0.76, 0.66, 0.55, 0.45438+0, 0.33, 0.28 respectively, while it has a poor correlation with elements such as Cs, Co, K and Rb. Similar information can be obtained from the cluster analysis genealogy diagram, that is, if 0.4 is taken as the dividing line (where the red line is located in Figure 8-9), these 24 elements can be divided into 8 groups: ①W, Sm, Mn, Sc, Ta, Lu, Yb, etc. (2) aluminum, potassium and rubidium; ③ Arsenic, iron, silver, cobalt and zinc; ④ Gold, hafnium and thorium; ⑤Na、Sb； While Ca, Cr and Cs are independent. This shows that W has a good correlation with rare earth elements and Mn. This is consistent with the good correlation between tungsten and rare rare earth elements in this area, and also represents the characteristics of time-oxide combination. A group of arsenic, iron, silver, cobalt and zinc are related to the sulfide assemblage of chalcopyrite, pyrite, arsenopyrite and pyrrhotite in this area, which represents the timely sulfide assemblage.
Table 8-6 Correlation Coefficient of Elements in Taoxikeng V 1 1 Pulse
4. Spatial distribution characteristics of tungsten.
The distribution characteristics of W element in single mineral in different veins are different, and there are also low and ultra-high contents in the same vein, which seems to have nothing to do with depth. In addition, there may be great differences between adjacent samples, such as Bs 156- 1, Bs 156-2, Bs 156-3, Bs 156-4 and bs1. The contents of W are 172× 10-6, 7.43× 10-6, 130× 10-6,1855×/kloc-respectively. According to all data, the maximum value of W is 1855× 10-6, the minimum value is 0.2 15× 10-6, and the average value is 187.67× 10-6. It shows that the distribution of data is extremely scattered.
It can be seen from the contour map of the spatial distribution of W element that the grade of W tends to decrease gradually from the deep to the surface. According to the current mining data, the middle section of 156 ~ 56m is the relatively rich place of V 1 1 vein in Baoshan section. This is very similar to the results of sampling analysis in the mining area (Table 8-7). On the plane contour maps of Baoshan section 156m and 106m (Figure 8- 1 1), there are three W concentration centers in both middle sections, but the concentration centers of the two sections are not completely corresponding, but "offset", showing the trend of spatial migration of the concentration centers from southeast to northwest. This may represent the migration direction of mineral liquid. This means that the V 1 1 vein in Baoshan section may extend southeast to Fenglinkeng section. At present, although the Fenglinkeng profile has been developed to the middle of 256 meters, there is no large-scale wolframite timely vein, and it is predicted that there may be rich ore bodies in the deep part of Fenglinkeng profile.
Figure 8- Plane Isograms of Tungsten Element in Taoxikeng Tungsten Mine at Baoshan Section156m and106m (× 10-6)
5. Study on orebody reserves prediction
The prediction of ore body reserves in this area is a problem that mining enterprises are very concerned about, and it is also the basic work of mineral resources potential evaluation. In addition to the conventional methods of irradiation and sampling analysis in exploration engineering, the results of timely neutron activation analysis can also provide reference information. Since tungsten is very stable in nature and insoluble in acid and alkali solutions, when it is precipitated from the solution, the critical content of tungsten is very low, and W exists in the form of complex or halide. Therefore, the original abundance of W in ore-forming fluids can be discussed according to the volume of fluids and the average grade of W in ore deposits (Li Yiqun et al., 199 1). The volume of ore-forming fluid is mainly estimated according to the volume of ore body, the volume of ore-free and poor veins, the range of alteration zone and the volume of possible escaped substances. If in the whole metallogenic system, the altered volume is 10 times of the ore body volume, the volume of ore-free and bad veins is twice of the ore body volume, and 20% of the filtered residual liquid is lost, according to this calculation, the existing ore body is concentrated by ore-forming fluid which is about 37.5 times larger than its volume. On this basis, according to the average grade of the deposit, the original tungsten abundance in ore-forming fluid can be calculated. If a general industrial tungsten deposit with a tungsten grade of 0. 12% is formed, the original tungsten abundance in the ore-forming fluid should not be lower than 32× 10-6 (equivalent to 10 ~ 3.86 mol/L aqueous solution); If a tungsten-rich deposit with a grade of 1% is formed, the original tungsten abundance in the ore-forming fluid should be no less than 267× 10-6 (equivalent to an aqueous solution with a concentration of 10 ~ 2.94 mol/L). Then, when only the volume of tungsten ore is considered without considering the altered volume, is there a corresponding relationship between the W content measured in time without considering the original W abundance and the W grade measured by slotting sampling in the tunnel? The following is an example of Taoxi pit vein V 1 1 (Table 8-7, Figure 8- 12).
Taoxikeng v 1 1 ace vein has been mined from the middle section of 356 to the middle section of 156, and the upper section of 356 to the middle section of 206 is basically mined. At present, the middle section of 206 to 156 is being mined, so it is urgent to predict and evaluate the reserves of the middle section of 106 to the middle section of 56 or even deeper.
Table 8-8 shows the calculation results of proven reserves of ~ 356 ore body in the middle section 156438+0. According to the neutron activation analysis data of W element, assuming that the measured data of W represents the content of W in the ore-bearing solution, and according to the volume calculated in the middle section of 156 ~ 356, it can be concluded that the original content of W in a considerable volume of water solution =W average abundance ×V volume; Then, according to the reserves w of this part of ore body divided by (W average abundance ×V volume), the volume multiple of ore body fluid is obtained, and then the reserves of the middle sections of 106m and 56m are calculated according to this multiple.
Table 8-7 Ore Body Characteristics of Taoxikeng V 1 1 Vein
Note: According to the Geological Report of Northwest Section of Taoxikeng Tungsten Mine Area of Bird Tungsten Products Co., Ltd., Chongyi County, Jiangxi Province, compiled by Gannan Geological Brigade.
Fig. 8- 12 Relationship between trace element content and tungsten grade in Taoxikeng tungsten vein.
The volume multiple is calculated as F=W reserves /(W average abundance× v volume) = 9576.247/(155.7× 65731.16×10-6) = 935.697.
The average abundance of W is obtained by the weighted average of the data sampled from the middle section of 156 to the middle section of 356, which is 155.7× 10-6, and the multiple is calculated accordingly. According to the changes of ore bodies in the roadway (as described in the description of ore body morphology), we assume that the ore bodies in the middle sections of 106m and 56m are both 600m in strike and 1m in thickness for calculation. The calculation results are shown in Table 8-8.
Table 8-8 Prediction results of 1 1 156m and 56m resources in the middle part of Taoxikeng vein.
Note: 106 total 1 middle section adopts the arithmetic mean abundance of this section w, 56 middle section adopts the estimated abundance after gridding, and 106 total 2 middle section adopts the arithmetic mean abundance of w after gridding.
The geological report of the northwest section of Taoxikeng tungsten mine area of Bird Tungsten Products Co., Ltd. in Chongyi County shows the V11* * *19643.07 t vein reserves proved by Jiangxi Geological Brigade. Then, using the original arithmetic average abundance of W element in the middle section of 106m, the total reserves of the middle section of 106m and the middle section of 56m are calculated as 10275.69t, and the 9576.24t * * in the middle section of 156 is 356. If the arithmetic average abundance of grid W is used in the middle section of 106m, the reserves in the middle sections of 106m and 56m are calculated as ***8046.33t, and the total in the middle sections of 156 ~ 356 is 17922.57t, which is slightly less than the proven reserves. These two sets of data show that this method can effectively predict the deep reserves of ore bodies. According to the shift supervisor of Langengzi section in the mining area, there is ore body dilution in the middle section of 156 currently being mined. Therefore, this method can be considered to predict reserves, simulate the spatial prediction of tungsten abundance and guide ore prospecting.
Verb (abbreviation of verb) conclusion and discussion
The study of Taoxikeng mining area shows that: ① through the neutron activation analysis of different middle sections of V 1 1 ace vein in Taoxikeng mining area, it is found that W is mainly related to elements such as Sm, Lu, Yb, Mn, Sc, Ta and Fe; (2) On the vertical projection plane of the ore body, three enrichment centers are identified by drawing the isograms of tungsten in the middle section of 156 and the middle section of 106, and the W content gradually increases from the surface to the deep, indicating that the ore liquid is enriched from southeast to northwest. This means that ore-forming fluids migrate from bottom to top and from southeast to northwest, which can predict that the deep part of Fenglinkeng has a good prospecting prospect. (3) The deep reserves of the vein are preliminarily predicted, and the middle reserves of 106m and 56m * *10275.6t are obtained. When the middle reserves of 156 ~ 356 are added, the total reserves of ore body V1kloc-0/are/kloc-0. It can be seen that the timely neutron activation analysis data is helpful to estimate the deep reserves of ore bodies.
It should be pointed out that the determination of trace elements in timely single mineral by timely neutron activation method has the advantages of less dosage and easy sample collection and processing, but it is still in the exploration stage as a whole, and it needs to accumulate a lot of data to get a more scientific and regular understanding.