Study on the prediction of finding concealed gold deposits in the northern section of Luanjiahe fault in Zhaoyuan, Shandong Province

(1) Geological survey of the study area

Luanjiahe fault is located in the upper wall of Zhaoping fault zone, which strikes northeast and extends nearly 60 kilometers. The structural surrounding rock is the middle Yanshanian coarse-grained Luanjiahe granite. There are comprehensive anomalies of aerogeophysical electricity/magnetism and sporadic anomalies of geochemical exploration in this fault zone. On the surface of the main structure, timely veins of polymetallic sulfides such as silver, lead and zinc are found. In recent years, Zhao Jin Company discovered gold spots in the upper wall of Zhaoping fault zone, and made new breakthroughs in prospecting in old strata.

This research work is arranged in the northern section of Luanjiahe fault zone, which is divided into two areas, east and west, with a distance of 470 meters (Figure 8-9). The terrain in the west area is steep, and the exposed area of bedrock accounts for 60%, and some areas are covered with vegetation. The eastern region is relatively flat, with developed vegetation and covered with thick clay.

Fig. 8-9 Schematic diagram of the layout of electrochemical survey area in the northern section of Luanjiahe fault in Zhaoyuan; Shandong.

(2) the exploration results obtained

There are 1 1 sections in the study area and 5 sections in the west area, with line number 1 ~ 9 and dot number 32 ~ 92. There are 6 sections in the East Zone, with line number 1 ~ 10 and dot number 15 ~ 75. Each section is 600m long, the line spacing is 200m, and the point spacing is 20 m. With a grid of 200×20m m, the completed area is 1.02km2, and the elements analyzed by geoelectric extraction method are Au, Ag, As and Sb. Soil samples are collected to measure the ionic conductivity of soil. The geoelectric extraction adopts the "dipole" extraction method with "dipole" power supply mode. After the geoelectric extraction content values of anode and cathode of analytical elements are accumulated, the anomalies with obvious concentration center, certain concentration zoning and continuity of abnormal points are numbered from left to right and from top to bottom by Surfer drawing software. Due to the different natural geographical landscape conditions in the east and west, the abnormal lower limit values of geoelectric extraction elements are also different. The lower limit of anomaly is 9× 10-9 for gold, 20× 10-6 for silver, 4× 10-6 for arsenic,10-6 for antimony and 4 μ s for conductivity measurement. The lower limit of anomaly is 5× 10-9 for gold, 20× 10-6 for silver, 3× 10-6 for arsenic,1×/kloc-0-6 for antimony, and the measured conductivity is 5μs/.

Fig. 8- 10 comprehensive map of electrochemical anomalies in the western part of northern Luanjiahe fault in Zhaoyuan, Shandong Province

1-Abnormal geoelectric extraction of gold: 2- Abnormal geoelectric extraction of silver; 3-Anomalous geoelectric extraction of arsenic; 4— Extraction of antimony by geoelectric anomaly; 5— Abnormal ionic conductivity of soil; 6— Mineralization point

Characteristics of electrochemical anomalies in the western region The western region is characterized by the formation of linear anomalies, and its axis is parallel to the NE-trending fault structure in this region. According to the characteristics of anomaly combination, it is divided into four NE parallel anomaly zones (Figure 8- 10). Au- 1 anomaly is consistent with Ag- 1 anomaly, and both of them have peaks at point 86 of 1 line, and the peaks of Au- 1 3.65× 1 0-9, Ag-/kloc. The anomaly axis is parallel to the axis of Sb- 1 anomaly and conductivity anomaly, and the distance is relatively close, forming the anomaly zoneNo. 1, which is about 500 meters long and 60 meters wide ... The anomaly peak value of Ag-2 is 50.08× 10-6, which is located at 80 points of 1 line. The abnormal peak value of Au-2 is 15.88× 10-9, which is located at 78 points of 1 line. The abnormal peak of As- 1 is 34.2× 10-6, which is located at 74 o'clock on Line 3. The abnormal peak value of Sb-2 is 2.5× 10-6, which is located at 70 o'clock on Line 3. The abnormal peak value of Ag-3 is 50.65× 10-6, which is located at 76 o'clock on Line 9. The abnormal peak value of soil ionic conductivity is 6.72μS/cm, which is located at 72 points of Line 5. Generally speaking, Ag-2, Au-2, As- 1, Sb-2, Ag-3 and conductivity anomalies are relatively close, and they are arranged alternately in parallel in the axial direction, forming No.2 anomaly zone with a length of 800m and a width of 80m, and its axial direction is northeast. The abnormal peak value of Au-3 is 33.38× 10-9, which is located at the 60th point of 1 line, and there is also an abnormal high value point (9.92× 10-9) at the 60th point of Line 3. The connecting lines of abnormal peaks constitute the abnormal axis, and its extension direction is the same as that of Sb-3 and Ag-9. This anomaly is consistent with the mineralized tectonic fracture zone, and its axial direction is consistent with the strike of the tectonic fracture zone. Au-4 anomaly shows high-value anomaly at 7 consecutive points on the 1 line, with an anomaly width of about 140m and an anomaly peak of 20. 12× 10-9, which is consistent with Sb-4 anomaly, and the axial direction is northeast, forming anomaly zone IV.

Characteristics of geochemical anomalies in the eastern region The geoelectric extraction elements and conductivity anomalies in the eastern region are also linear. The peak value of Au- 1 anomaly is 9.88× 10-9, which is located at the point of 1 line 17, connected with the high-value anomaly points of Line 3 15 and 17, and the distribution direction is northeast (Figure 8-7 The abnormal peak in Au-2 is 7. 15× 10-9, and the abnormal peak in Sb- 1 is 3.27× 65438+. It is also consistent with As- 1 anomaly, and the peak value of As- 1 anomaly is 3.4× 10-6, which is located at the 25th point of 1 line. The anomaly of this assemblage is distributed linearly, and the axial direction is northeast (Figure 8- 1 1, Figure 8- 12). Anomaly of Ag- 1 and Ag-2, and anomaly of conductivity Cond-2 and Cond-3 form an anomaly zone with a length of 900m and a width of about 140m, which is distributed in the northeast. Ag- 1 anomaly continuously forms high-value anomalies at points 1 line 4 1, 43 and 45, and the peak value is136.0×10-6; The abnormal peak value of Ag-2 is 173.55× 10-6, which is located at 5 1 point of Line 3 and connected with 49 points and 5 1 point of Line, forming an abnormal axis. The abnormal peak value of conductivity Cond-2 is 18μS/cm, which is located at No.49 of Line 5. The abnormal values of Cond-3 appear continuously at No.59, No.6 10 and No.63 on the line10, and the abnormal peak value is 16.57μS/cm. There are also anomalies of gold, arsenic and antimony in the anomaly zone. This abnormal zone is located in the triangle area where Luanjiahe fault meets the secondary fault structure (Figure 8- 1 1). The peak value of Au-3 anomaly is 8.67× 10-9, which is located at 63 points of Line 3. The anomaly is an isometric anomaly (Figure 8- 1 1). The abnormal peak value of Au-4 is 22.47× 10-9, which is located at No.75 of Line 3, and there is conductivity abnormality in this abnormal range (Figure 8- 1 1).

Generally speaking, the anomalies of geoelectric extraction elements and soil ionic conductivity in this area are linear (the west area is more obvious than the east area), and the distribution direction is northeast, which is consistent with the extension direction of fault structures in this area, with strong anomaly intensity, obvious element combination characteristics and high degree of conformity. It can be considered that the fault structures in this area are ore-guiding structures or ore-hosting structures.