Xujiagou copper mine target area is located in the northwest extension of Tongchang copper mine, the only independent medium-sized copper mine in Qinling Mountains. The study of the deposit shows that the Tongchang copper deposit has two-stage ore-controlling characteristics of typical orogenic deposits, and the copper mineralization process is mainly controlled by Mesozoic and Neoproterozoic marine basic volcanic deposits and quartz diorite (881~ 840 Ma; Wang Wei et al., 20 1 1) was controlled by two-stage intrusion transformation. Mesoproterozoic marine basic volcanic deposits are accompanied by volcanic sedimentary mineralization activities. Basic volcanic sedimentary rocks are rich in copper, and copper and other ore-forming materials are precipitated in the later alteration process, which provides a material source for mineralization, while industrial veins are strictly controlled by the transformation of Jinning intrusion, which provides thermal power and structural space for the activation and migration of ore-forming materials.
The basic metallogenic geological conditions of Xujiagou target area are basically the same as those of Tongchang copper mine. The strata are altered spilite and schist spilite. The ore-controlling fault of Tongchang copper mine extends westward to Xujiagou target area. The fracture zone is mainly composed of strong schist spilite, serpentine, schist and fractured dolomite. Magmatic rocks exposed in the mining area include serpentine, schist, gabbro and a small amount of quartz diorite. The main components of the rock are actinolite, albite and a small amount of biotite, and the altered minerals are chlorite and epidote. The metal minerals are mainly pyrrhotite, followed by pyrite, chalcopyrite and a small amount of tetrahedrite. The main mineralization alteration zones are fading, sericitization, chloritization, silicification and limonitization. Geochemical analysis of rocks (ores) shows that the contents of SiO2 _ 2, MgO, CaO, Na2 O, Al2O3, MnO, P2O5 and As decrease, while the contents of Fe2O3, FeO, P2O5, S, Cu, Zn, Mo, Sb, Bi, Co, Ni and Ba increase, especially Cu.
1:50000 dispersion current scanning results show that the copper ore field is a multi-element enrichment area with copper as the main component and the combination of copper, gold, silver and cobalt. 1:25000 soil geochemical survey, an anomaly of lead, zinc, gold and silver combination with copper as the main component was circled in Xujiagou area, with an abnormal length 1600m, width 1000m and copper concentration (100 ~ 200) × 60.
According to the analysis of basic metallogenic geological conditions and geochemical anomalies, it is considered that Xujiagou is a prospecting target area similar to Tongchang copper mine.
2. Exploration and verification of prospecting target area
Using the comprehensive exploration model, the prospecting work in this area is reasonably arranged and implemented. At first, geochemical anomalies were examined, combined geological and geochemical primary halo profiles, surface geological mapping and trench exploration were carried out. Results copper clues were found in the fracture zone exposed by the exploration trough. Subsequently, intensive trench exploration was carried out along the ore-controlling fault zone, and no new mineralization was found. Based on this, the author thinks that there may be semi-concealed deposits in Xujiagou target area.
Based on the preliminary understanding of the buried depth of the deposit, the surface induced polarization scanning surface suitable for finding shallow sulfide ore bodies was put into the mining area, and as a result, three IP abnormal zones were found in the mining area. Among them, the M ⅰ anomaly band is longer than 1700m and wider than 30 ~ 100 m, and the Ms value is generally 5% ~ 10%, with the highest value exceeding 40%. The length of m ⅱ anomaly zone is 1200m, and the width is 20 ~ 30m. The Ms value is generally 5% ~ 10%, and the highest value exceeds 19%. The m ⅲ anomaly zone is more than 700 meters long and about 100 meters wide, and the Ms value is generally 5% ~ 10%. The three abnormal zones are concentrated in the physico-chemical spilite zone of ore-bearing thin slices, and the strike is consistent with the fracture zone, with high strength and good continuity, reflecting that sulfide ore bodies may exist in the deep.
According to the occurrence and IP anomaly of the fracture zone in the target area, firstly, the borehole is designed to verify the geophysical anomaly, and as a result, all the boreholes are basically mined, among which ZK3005 is in the fourth ore body, with the cumulative thickness of 17.52m (Figure 6-26). After that, drilling and charging were carried out in the well to track the extension of the ore body, and drilling design was carried out according to the abnormal charging in the well, which made great progress in prospecting and exploration in the predicted target area.
Through the verification of the target area, three copper mineralization alteration zones were found in the mining area, numbered ⅰ, ⅱ and ⅲ from south to north, which were mainly distributed in the spilite in the middle section of Guojiagou Formation and were respectively affected by F 1 1- 1. 1 mineralization alteration zone delineates 1 1 ore body, in which 1-5 is the main ore body, and the ore bodies in 1 mineralization alteration zone are layered or layered, and the surrounding rocks on the upper and lower walls of the ore body are flaky lepidolite. At present, the project controls the length of the ore body to be 570 meters, the maximum extension of the ore body to be 340 meters, the horizontal thickness to be 3.70 meters, and the average grade to be 0.97× 60. Two ore bodies have been preliminarily delineated in No.2 mineralized alteration zone.
Through exploration in key sections, it is preliminarily concluded that the resource of 332+333+334 1 copper mine is over 5.4× 104t, the ore quantity is 554.8× 104t, and the average grade is 0.99× 10-2.
According to the comprehensive prediction, the ore-forming conditions of Nanxujiagou ore belt (that is, the west extension of the ore-controlling fault F 13 in Tongchang copper mine) are similar to those of Huangniliang ore belt, and the deep part of the mine area has not been effectively controlled. The distribution area of basic volcanic rocks in the southern outer contact zone of Tongchang diorite body also has good metallogenic conditions. According to the comprehensive prediction, the copper prospecting prospect in this mining area can reach (10 ~ 15) × 650.
Figure 6-26 Geological Map of Line 30 Section of Xujiagou Copper Mine