Geochemical exploration has played an important role in the prospecting of Jiaodong gold deposits. The exploration methods have gradually developed from secondary halo geochemistry and primary halo geochemistry to structural geochemistry. For secondary halo geochemistry in the area, 1:200,000 and 1:50,000 river sediment measurements have been systematically carried out, and 1:10,000 soil measurements have been carried out in some mining areas. Secondary halo geochemistry has been selected in large-area prospecting target areas. , plays a key role in mineralization prediction. Primary halo geochemistry, 1:50,000 bedrock geochemical survey in some areas and 1:10,000 and 1:5,000 bedrock geochemical survey and geochemical profile survey in some mining areas have been carried out to lay out the exploration project for the general survey work. Provided basis. Structural geochemistry measurement is a newly developed geochemical exploration method in recent years. In the survey and evaluation of mineral deposits, bedrock samples are collected along the surface or in boreholes along the mineralization structure to provide information for deep prospecting, prediction of blind ore bodies, and mineral deposit evaluation. basis.
1. Principle of structural geochemical method
Structural geochemical prospecting technology is to infer deep hidden mineralization conditions by analyzing the geochemical halos of mineralization indicator elements in structures. It is a primary Halo technology category. It is superior to traditional primary halo technology in many aspects. First, it can more effectively detect weak geochemical anomalies formed by deep hidden mineralization in shallow parts; second, sampling is based on the structural framework as the main control standard, and the irregular network High-degree sampling can reduce the number of samples and reduce exploration costs without missing mineralization; third, the structural control of mineralization and halo formation is fully considered, making it easier to interpret anomalies (Peng Shenglin et al., 2004).
Since tectonics and geochemistry are important dynamic processes during and after mineralization, tectonic geochemistry must play an important role in detecting geochemical information of hidden mineral deposits. At present, we mainly use the geochemical rules of fault structures of mineralization and halo to find minerals, study the rules that the geochemical spatial changes of mineralization indicator elements are controlled by structures during and after mineralization, and analyze those special mineralization processes. The structural rocks in the halo structure can capture the weak geochemical anomalies caused by deep hidden ore bodies on the surface. The reason is that the migration of mineralizing elements in these structures is much easier than in non-halo-forming structures, and the dynamic process of halo formation is also controlled by the structural dynamics process (Peng Shenglin et al., 2004).
The native halo prospecting method is a widely used and effective method in gold prospecting. Primary halos are geochemical anomalies that form around mineral bodies or other geological bodies. The primary halo prospecting method is a method of prospecting by discovering and studying primary halos in bedrock. This method is usually used to find blind ores. The basic theory of primary halo prospecting is that the primary halo of hydrothermal deposits is zoned in the axial (vertical) direction, that is, each ore body has its own front halo, near ore halo and tail halo, and the front halo is in front of the ore body. The edge can reach 100~300m, providing important information for finding blind mines (Li Hui et al., 2006). Since gold mines have the characteristics of multi-stage pulsation and superimposed mineralization and halo formation, a primary superimposed halo prospecting method has been developed, that is, based on the multi-stage, multi-stage pulsation and formation of ore bodies (halos) in gold ore mineralization and halos. Search for blind mines by spatially superimposing features.
In recent years, the characteristics of primary halos in structural alteration zones have been studied in the Jiaodong area and used for blind ore prediction and deep exploration, which is called the structural superposition halo method. The principle of the method is: hydrothermal deposits are strictly controlled by structures. The characteristics of the primary halo development of ore bodies in structures are high strength and large scope within the structural belt. In particular, the front halo can reach several hundred meters at the front edge of the ore body. Study the axial (vertical) zoning of primary haloes in structures and the superimposed structure of primary haloes formed in different stages. Only taking alteration superimposed samples in structural zones can not only strengthen the halo intensity or blind ore prediction information, but also greatly Reduce the workload of sampling and analysis, improve work efficiency and ore prospecting effect (Li Hui et al., 2006).
II. Structural geochemistry of deep gold deposits in Jiaojia Mining Area
(1) Working methods
Due to the large burial depth of deep deposits and the existence of shallow deposits, Corresponding to ore deposits (bodies), surface structural geochemistry research cannot effectively predict deep ore bodies, so deep ore prospecting uses borehole sampling methods, that is, samples of structurally altered rocks in boreholes are taken to study their primary halo characteristics, which is called boreholes. Tectonic geochemistry. In this work, samples were collected from typical exploration lines 112 and 144 in the Jiaojia Mining Area, and the contents of 44 trace elements were analyzed. The analysis results of 18 mineralizing elements and related trace elements are listed in Table 8-2.
Experimental testing was completed at the Analysis and Testing Center of the Beijing Institute of Chemical Industry and Metallurgy of the Nuclear Industry. Except for Au and Ag, which were tested using the atomic absorption spectrometer (TAS-990F), ELEMENT inductive coupling and plasma mass spectrometry atomic fluorescence photometer (AFS-2202), other elements All were tested using the inductively coupled plasma mass spectrometry (ICP-MS) method (instrument model HR-ICP-MSElementⅠ).
(2) Tectonic geochemistry rules
1. Statistical distribution characteristics of elements
Conduct statistical analysis on 18 kinds of metallic elements, and calculate the Lithified granite (granite, pyrite-sericite granite), pyrite-sericite granite cataclastic rock (pyrite-sericite granite cataclastic rock), pyrite-sericite cataclastic rock (pyrite-sericite cataclastic rock) The maximum value, minimum value, average value (X), standard deviation (S), coefficient of variation (Cv), and concentration Clark value (C) of each element in the rock), the hanging wall rock of the main fault, and the main fault footwall rock , mineralization coefficient (Z) and element contrast of pyrite-sericite cataclastic rock (Table 8-3). Taking the concentration Clark value greater than 0.5 and the contrast value greater than 1 as standards, the mineralization element combination is determined to be Au, Ag, Cu, Pb, As, Sb, Bi, W, Sn, Mo, B, and U.
The coefficient of variation (all samples) of the mineralizing elements Au, Cu, Pb, As, Sb, Bi, and Mo is greater than 1, indicating that the distribution of these elements is extremely uneven and there are local enrichments. or impoverishment. The mineralization coefficients of these elements (all samples) are greater than 10, indicating that mineralization is prone to occur. The abnormal contrast values ??of various elements are quite different. The main halo-forming elements are Au, Cu, Pb, Sb, Bi, As, and Mo (the contrast values ??are greater than 2). Among them, the Au, Bi, and Mo elements have the largest contrast values, indicating that their composition The halo intensity is high; the secondary halo-forming elements are Ag, W, Sn, B, Th, and U (the contrast value is greater than 1 to 2).
Relevant analysis (Table 8-4) shows that among the 18 metal elements, Au and Bi are most closely related, followed by W, Sb, Cu, Ag, As, Sn, and B. This is related to the area The combination relationship of internal mineralizing elements is basically the same. Clustering and grouping according to the correlation coefficient of 0.2 can be divided into three groups, Au, Ag, As, Bi, Sb, W, Cu, B are one group, Pb, Sn, Th, U are one group, Zn, Co, Ni , V, Cr, and Ba are a group. Clustering and grouping according to the correlation coefficient of 0.45, Au, Ag, As, Bi, and Sb are in one group (Figure 8-25), indicating that these elements are closely related, and their enrichment is closely related to the ore body, which is the unique characteristic of this area. Mineralization indicator elements.
The average contents of the main mineralizing elements Au, Ag, Cu, As, Bi, Sb and the trace elements Co, Ni, V, Cr, W and Ba in the footwall rocks of the main fault surface are higher than those in the hanging wall rocks. , indicating that the alteration of the footwall is stronger than that of the hanging wall. Comparison of altered rocks with different structures shows that the contents of major halo-forming elements such as Au, Ag, Cu, As, Sb and Bi increase as the alteration increases.
Table 8-2 Analysis results of mineralizing elements and related trace elements in the Jiaojia deep mining area
Sample name codes in the table: γ—granite, γJ—potassium feldsparized sericite pyritized granite, γJH—pyritized granite, SγJ—seriticized granitic cataclastic rock, SγJH—pyritized granitic cataclastic rock, SJH—pyritized sericized granite cataclastic rock, SJ—sericite Antarctic cataclastic rock.
Table 8-3 Statistical results of tectonic geochemical content of mineralizing elements and related trace elements in Jiaojia deep mining area
Continued table
Continued table
Note: The lithology codes in the table are the same as Table 8-2.
Table 8-4 Correlation coefficient matrix of elements analyzed by structural geochemistry in Jiaojia deep mining area
Figure 8-25 R-type clustering pedigree of elements analyzed in structural geochemistry in Jiaojia deep mining area Figure
R-type factor analysis (Table 8-5) shows that the factor model of gold elements in the Jiaojia deep gold mine is: XAu=0.52F1+0.37F2-0.02F3-0.48F4-0.11F5+0.07 F6 indicates that F1 and F4 contribute more to gold mineralization.
The main factors determined after orthogonal rotation (Table 8-6) are: F1 [As, Bi, Sb, B, Ag, Cu, Au], F2 [Cr, Co, Ni, V], F3 [Pb, Ag] , F4 [Au, Sn, W, Bi], F5 [Mo], F6 [Th, U, W]·[Cu]. Among them, F1 is the main mineralization factor, indicating that Au is closely related to arsenopyrite, bismuthite, arsenite, chalcopyrite and other polymetallic sulfides; F4 is the secondary mineralization factor, indicating that Au is closely related to Sn and W. origin relationship.
2. Structural geochemical characteristics of borehole profiles
The structural geochemical profile along the 122 exploration line (Figure 8-26) consists of ZK622, ZK603, and ZK604 boreholes. ZK622 hole Located in the middle of the main ore body of I-1, hole ZK603 is located in the middle and lower part of the main ore body of I-1, and hole ZK604 is located in the lower part of the main ore body of I-1. On the borehole profiles passing through the main structural alteration zone, the content of Au and a series of associated elements has changed, most obviously in the ZK622 hole, showing a strong positive anomaly combination of Au, As, Sb, Bi, and Mo elements simultaneously, and The anomaly peak positions coincide; Ag, Pb, Cu, Sn, U, and Th show positive anomalies, but the element concentration center is slightly shifted. Except for the Cu anomaly, which is located in the deep part of the Au anomaly, the other element anomalies are located in the shallow part of the Au anomaly; Ni , Co, and Cr also show positive anomalies. Along the exploration line profile, the ZK622 hole in the middle of the ore body has many abnormal elements and high anomaly intensity; towards the tail (lower part) of the ore body, the abnormal elements decrease and the anomaly intensity decreases.
The structural geochemical profile along the 144 exploration line (Figure 8-27) consists of three boreholes: ZK606, ZK608, and ZK615. Hole ZK606 is located at the head of the main ore body I-1, and hole ZK608 is located at the head of the main ore body I-1. In the middle of the main ore body 1, hole ZK615 is located at the tail of the main ore body I-1. The change characteristics of element content are similar to those of line 112: Au, As, Sb, Bi, W, and Cu elements show a synchronized strong positive anomaly combination, and the abnormal peak positions coincide; Mo, Pb, Zn, B, Ag, U, and Th elements It shows a positive anomaly, and the concentration center of some elements is slightly shifted. The number of abnormal elements at the tail of the ore body decreases, and the abnormal intensity decreases. The abnormal elements mainly include Au, W, Bi, and Cu.
Table 8-5 Orthogonal factor loading table of R-type factor analysis of primary halo of Jiaojia deep gold mine
Table 8-6 R-type factor analysis of primary halo of Jiaojia deep gold mine Maximum Variance rotation table
Figure 8-26 Structural geochemical profile of borehole 122 in Jiaojia deep mining area
Figure 8-27 Structural geochemistry of borehole 144 in Jiaojia deep mining area Profile
3. Determination of indicator elements
From the perspective of the original halo element composition, the main halo-forming elements with the highest contrast values ??are Au, Bi, and Mo, followed by Cu, Pb, Sb, they both form clear anomalies. From the perspective of primary halo generation combinations, elements significantly positively correlated with gold include Ag, As, Bi, and Sb. From the structural geochemical profile, in addition to Au, Ag, Cu, Bi, Pb, As, and Sb forming strong positive anomalies, Mo, W, B, U, and Th also often form positive anomalies. Therefore, it is believed that Au, Ag, Cu, Bi, Pb, As, and Sb elements have strong affinity in geochemical behavior and are identified as mineralization indicator elements; Mo, W, B, U, and Th element anomalies can also be used as mineralization indicator elements. Auxiliary indicator elements for gold mineralization.
3. Structural and geochemical anomaly zoning
Through the geochemical study of the primary halo in the Jiaojia gold ore belt, it was found that the primary halo along the mineralization structural belt has obvious horizontal zoning and Axial zoning.
(1) Horizontal zoning
The structural geochemical profile was measured along the 288 exploration line in the Sizhuang mining area. Judging from the geochemical element content curve of the profile (Figure 8-28) , near the main metallogenic structural belt in the northwest part of the profile, the content of Au and related elements has changed significantly. It appears as a synchronized strong positive anomaly combination of Au, Ag, As, and Bi elements, with the anomaly peak positions coinciding. Although Cu, Pb, Sb, and Hg elements also show positive anomalies, their element concentration centers are slightly shifted.
The structural geochemical profile along the 368 exploration line in the Sizhuang mining area (Figure 8-29) shows that Au and Ag present a synchronous strong positive anomaly combination above the ore body, and the peak positions coincide; while Pb , Zn and Cu abnormal concentration centers are slightly shifted.
The horizontal banding of the primary halo shows that the inner bands are Au, Ag, and Cu, and the outer bands are Pb and Zn.
It can be seen that the primary halo anomaly near the Jiaojia ore-controlling structural belt in this area has obvious concentration zoning in the horizontal direction. The primary halo anomalies of Au and the main associated elements Ag, As, and Bi are often located above the main structural zone and the main ore body. The abnormal peaks of each element coincide with gold, and the element anomalies of Cu, Pb, and Sb are slightly away from the mineralization center. According to the above geochemical profile, combined with the geochemical characteristics of other mining areas in the Jiaojia ore field, the horizontal zoning is divided into inner zones of Au, Ag, As, and Bi, which are manifested by strong positive anomalies of Au, Ag, As, and Bi, and Cu, Weak positive anomalies of Pb and Zn; strong positive anomalies of Cu, Pb, Zn, and weak anomalies of Au, Ag, As, and Bi in the middle band; positive anomalies of Hg and Mo and weak anomalies of Au, Ag, and Bi in the outer band. According to the geophysical exploration team's statistics on the element zoning sequence of 60 boreholes, it was determined that the lateral element zoning from outside to inside is Hg-Zn-Pb-Cu-Sb-Ag-As-Ag.
(2) Axial zoning
The 159 exploration line of Xincheng Gold Mine was selected to study the axial zoning characteristics. The range of the native halo background value is used as the background area, and three values ????of 1, 2, and 4 times the abnormal lower limit are used to divide the outer, middle, and inner bands of each element's anomaly. Among them, due to the large abnormal concentration gradient of gold and silver elements, 1 times, 3 times, and 9 times are used to divide the abnormal concentration zones. On this basis, the isoconcentration map of each element in the native halo was drawn.
The structural geochemical anomaly map of the primary halo of the 159 exploration line (Figure 8-30) shows that the ore body is produced in the footwall of the fault, and the primary halo develops along the axial direction and extends far beyond the control of drilling. In addition, the primary halo on both sides of the ore body is narrow, and the primary halo is lens-shaped around the ore body. The development on both sides is slightly asymmetric, and it is more developed below the ore than above the ore. The side of the mine close to the fault is narrow, and the element concentration decreases like a steep slope. It is speculated that the fault gouge on the main section acts as a barrier and affects the diffusion of elements.
Among them, Au, Ag, Bi, and Zn elements are exceptionally strong and have three bands: inner, middle, and outer. The outer zone has a large range and is beyond the control of drilling. The inner zone surrounds the ore body, and the abnormal concentration center coincides well with the ore body.
Figure 8-28 Structural geochemical profile of 288 exploration line in Sizhuang Mining Area
The abnormal distribution range of As, Pb, and Cu elements also exceeds the control of drilling, and the abnormal intensity is slightly weaker than the above elements. , the middle zone surrounds the ore body, the inner zone is well integrated with the ore body, and only the inner zone of copper element is slightly biased towards the ore tail.
The abnormal intensity of Sb element is small, the outer band surrounds the ore body, and the inner band is deviated from the center of the ore body and is under the ore.
The abnormal intensity of Co and Ni elements is small, with only outer and middle bands. It is distributed at the front edge and tail of the ore, and is biased toward the bottom of the ore. It is speculated that another ore body in the upper part of the ore body has been denuded, and a front halo exists due to its influence.
In general, the scale of the primary halo of the Jiaojia style gold deposit is closely related to the mineralization intensity. Deposits with large mineralization intensity and scale will have correspondingly larger primary halos. Parts with high mineralization intensity have large halo widths. The shape of each element halo is in the shape of a closed or convergent belt on the vertical section. The width is relatively small, generally a few meters to nearly a hundred meters. However, the axial length of the ore body can exceed the control of the drilling, generally several hundred meters. The longest is more than 1200m, and the overall shape of the halo is an elongated discus shape surrounding the ore body.
Predecessors have done a lot of work on the axial zoning sequence of the native halo of the Jiaojia belt. According to the characteristics of each element on the structural geochemical profile, combined with the general rules of axial zoning of hydrothermal deposits and previous data, it is believed that the primary halo axial zoning of the Jiaojiashi gold deposit is Hg-As-Zn, Pb-Cu ,Ag,Bi,Sb-Au. Au, Ag, Bi, and Sb are short-range indicating elements, Cu, Pb, and Zn are medium-range indicating elements, and As and Hg are long-range indicating elements. This shows that when there are anomalies in Hg and As, it often indicates the presence of minerals in the depths; when Au, Ag, Bi, and Sb are abnormally good in short-range indicator elements, it often indicates that the mineralization enrichment center is not far away.
Figure 8-29 Structural geochemical profile of 368 exploration line in Sizhuang Mining Area
IV. Gold deposit structure superimposed halo model
Li Hui et al. (2006) studied Jiaodong A structural superposition halo model of some gold deposits was used to predict blind ore bodies. The Xincheng gold mine is located on the north side of the Jiaojia gold mine in the Jiaojia gold belt in this study area. The study of its structural superposition halo is of great significance to this work and future deep prospecting in northwest Jiaoxi. With good enlightenment significance, the structural superposition halo model of the Xincheng gold deposit established by Li Hui et al. (2006) is:
(1) Mineralization and halo characteristics: A certain amount of As is produced in each main stage of hydrothermal mineralization. , Sb, Hg, Bi, Mo, Mn, etc. Each stage of the mineralization process has obvious positive geochemical vertical zoning. The ore bodies formed at each stage have their own halo and tail halo, As, Sb, Hg In the primary halo of the ore body formed at each stage, elements such as Bi, Mo, Mn, Co, Ni and other elements are enriched in the front edge of the ore body to form the front halo, while elements such as Bi, Mo, Mn, Co, and Ni are enriched in the tail of the ore body to form the tail halo. ; When the later stage of mineralization (halo) is superimposed or partially superimposed on the previous stage of mineralization (halo), the elements that first formed the ore body or halo will be activated and migrated, causing the original zoning structure to be damaged to a certain extent. However, it can still show vertical zoning to a certain extent. The superposition of several stages of ore bodies or haloes forms a complex superimposed halo; the beaded ore bodies (or pinch-out reappearance ore bodies) formed at the same stage have an overall dizzy, Tail dizziness, individual ore bodies have their own dizziness and tail dizziness.
Figure 8-30 Geochemical map of Xincheng Gold Mine 159 exploration line
(2) Deposit structure superimposed halo model: ① The leading halo indicator elements are Hg, As, Sb, and F , B, W, and the tail halo elements are Bi, Mo, Co, and Mn. It is known that if front and tail halos appear in the deep part of the ore body, it indicates that the ore body extends downward greatly or there is a blind ore body in the deep part. ② The abnormal range of soil thermally released halogen F can indicate the relative position of the deep hidden gently sloping ore bodies; the I abnormality is distributed just above the ore body occurrence part and the exposed part of the front edge structure. ③The front halo of fluid inclusions in the ore deposit is CO2, CO, CH4 gas halo and F-, Cl- ion halo.