I. Geological Survey of Mining Area
The strata exposed in Jinshizhou mining area include deep metamorphic rock series of Sinian subgroup of Yunkai Group and rhyolite porphyry, lithic crystal tuff and volcanic breccia of Gaojiping Group of Upper Jurassic.
The sub-group of Yunkai Group is a ore-bearing stratum, and its main lithology is mixed potash granite, plagioclase gneiss, plagioclase amphibole, calcite marble, siliceous rock, wollastonite, andesite porphyrite, intermediate-basic lava, recrystallized lithic tuff, with a small amount of plagioclase gneiss, amphibole granulite and metamorphic feldspar chronological sandstone. Granite and gneiss gradually change with each other, showing an irregular contact relationship. Siliceous rocks, wollastonite, fine-grained mixed potash feldspar granite and andesite porphyrite are the main host rocks.
Magmatic rocks exposed in the mining area include Yanshanian fine-grained biotite granite (γ2-35), Yanshanian porphyry potash granite (γ3- 15), Yanshanian granite porphyry (γ3-25) and quartz porphyry (Q3-25). Granite porphyry is the largest rock mass in the mining area, which is distributed in the north-south direction, occupying the west wing and the middle part of the Yinkuangkeng-Huangjinkeng anticline, and dividing the anticline into two parts. There are adamellite, medium-fine grained granite and porphyritic granite in the tunnel, and diopside skarn and wollastonite skarn appear at the edge of the rock mass.
The mineralization zone in Jinshizhang mining area is 2000 meters long and 300 meters wide, and the mineralization is strictly controlled by strata and faults. Faults are mainly NW-trending and nearly North-South trending: 2 15 ~ 235 ∠ 30 ~ 80, 75 ~ 85 ∠ 35 ~ 75. There is also a group of NE-trending joints:131~156 ∠ 44 ~ 80, and the distribution direction of ore bodies is controlled by NW-trending structures.
At present, six lead-zinc-silver industrial ore bodies and several iron ore bodies can be delineated. According to the geological characteristics of ore-controlling, it can be divided into three types: ① hydrothermal metasomatic Pb-Zn-Ag ore bodies (V4) in the fractured zone of mixed K-feldspar granite, ② surface weathering leaching Ag-Mn ore bodies (V6), and ③ stratabound metamorphic Pb-Zn-Ag ore bodies (V 1, V 1-2, V/KL) in the deep metamorphic rocks and volcanic lava of the Sinian Yunkai Group. Cumulative coal seam thickness is 9.27 ~ 26. 16m, ore grade is ag164×10-6 ~ 202×10-6, Pb 0.56% ~ 0.69%, Zn 0.68% ~/kloc. There are specularite and ferromanganese deposits under the bed of Yingshi silver mine.
There are mainly two mineral combinations, one is lead-zinc-silver combination, and the other is silver-manganese combination. Metal minerals include galena, sphalerite, pyrite, chalcopyrite and silver minerals; Followed by bornite, tetrahedrite, chalcocite, local hard manganese ore, hematite, specularite, magnetite, ilmenite and molybdenite; The secondary minerals are malachite, azurite, pyrolusite, limonite and lepidolite. Gangue minerals include syenite, potash feldspar, plagioclase, calcite, wollastonite and tremolite, followed by diopside, zoisite, epidote, garnet, sillimanite, biotite, fluorite and chlorite. Microscopic identification shows that silver mainly occurs as independent silver minerals, including argentite, tetrahedrite, natural silver, crimson silver, red silver and chalcopyrite-copper silver. Among them, argentite is the main mineral, followed by tetrahedrite and natural silver, and other silver minerals are less.
There are three main ore types: iron-manganese ore in silver-bearing soil, lead-bearing zinc-silver ore and silver ore. Ore texture includes inclusion texture, irregular granular texture, solid solution separation texture, marginal texture, porphyritic metamorphic texture, granular metamorphic texture, metasomatic residual texture and columnar metamorphic texture. Ore structures include disseminated structures, banded structures and massive structures.
The surrounding rocks of Jinshiqiang mining area are strongly altered, mainly silicified, wollastonite, diopside, calcite, garnet and pyrite, followed by epidote, potassium, kaolin, chloritization, sericite, malachite and limonite.
Second, the relationship between rock types and mineralization
According to the statistics of Ag, Pb, Zn and Cu analysis data of 22 1 sample in Jinshizhou mining area (Table 7-26), it is found that ① there are 63 samples with Ag content ≥ 100× 10-6, of which 47 are silica fume samples (accounting for 74.6%). There are 95 pieces with Pb+Zn content ≥ 1.2%, including 66 pieces of silica fume (accounting for 69.5%), 4 pieces of marble, 9 pieces of granite/kloc-0 and 6 pieces of andesite. ② The mineralization intensity of Ag, Pb and Zn in all kinds of rocks is obvious, and the mineralization intensity of silica fume rock is the highest. Among 89 kinds of pozzolans, 52.8% pozzolans have Ag content ≥ 100× 10-6, and 74.2% pozzolans have Pb+Zn content ≥ 1.2%, which is the main mineralized rocks.
Correlation analysis shows that the correlation coefficients of Ag and Pb are 0.253, Ag and Cu are 0.30 1, and Pb and Zn are 0.403 (critical value γ0.999=0.230), indicating that there is an obvious positive correlation between them. It reflects that the mineralization of silver is closely related to lead and copper mineralization, indicating that silver has the same mining and utilization value as lead and zinc.
Table 7-26 Comparison Table of Mineralization Intensity of Silver, Lead, Zinc and Copper with Different Lithology in Jinshizhou Mining Area
Note: According to the analysis data of slotted samples.
Three. Structural ore-controlling characteristics
60 fractures developed in Jinshizhou mining area 1 alleys and 3 veins were measured and counted (Table 7-27), and a rose diagram was made (Figure 7-23 on the left). It can be seen from the rose diagram of faults that the overall faults in the mining area are NW-trending and NE-trending, which is consistent with the NE-trending faults and deep faults in the area.
Table 7-27 Statistical Data Sheet of Cracks in Jinshiqiang Mining Area
Note: According to the survey data recorded in the tunnel.
Figure 7-23 Rose Diagram of Cracks (Left) and Joints (Right) in Jinshiqiang Mining Area
The faults developed in the tunnel are mainly northwest and nearly north-south: 2 15 ~ 235 ∠ 30 ~ 80, 75 ~ 85 ∠ 35 ~ 75.
Fifty-three joints in Jinshizhou mining area 1 alleys and three veins were measured and counted (Table 7-28), and a rose diagram of joints was made (Figure 7-23 on the right). It can be seen that the main strike of joints in the mining area is NE direction 13 1 ~ 156. According to the analysis data of tunnel grooving samples, there are six high-value points (Ag >110×10-6, Pb > 0.5%, Zn > 0.5%, CM2719,20, CM292/kloc).
Table 7-28 Joint Statistical Data Sheet of Jinshiqiang Mining Area
Note: According to the survey data recorded by Jinshiwang Tunnel.
The ore bodies in and around the cave are strongly mineralized, and there are many kinds of alteration, such as silicification, wollastonite, diopside, epidote, potassium, kaolin and chloritization. The contents of silver, lead and zinc are obviously increased, which should be a structural fracture zone type lead-zinc-silver polymetallic deposit.
Four or three points of understanding
(1)NW-trending fracture zone is the main ore-controlling structure.
For the division of fault structures in Jinshiqiang mining area, it was previously thought that there were only two groups of faults in NE direction and EW direction. Through the exploration engineering exposure and our in-depth study, it is found that there are two groups of faults in northwest direction and near north-south direction.
The east-west fault is large in scale and belongs to regional structure, which controls the distribution of regional iron, manganese, lead, zinc and silver (abnormal) belts. The secondary faults derived from it are NW-trending and NE-trending, and the NW-trending fault is most closely related to mineralization, and the ore bodies are distributed along the NW-trending fault. The scale of NE-trending faults is generally small, mainly showing joint properties, and its relationship with lead-zinc ore bodies needs further study.
(2) "Cave" belongs to secondary oxidation leaching in granite alteration zone.
The "karst cave" in Jinshiqiang mining area is not completely a "karst cave" left by limestone dissolution. In fact, the granite alteration zone is mainly fractured and then leached and weathered by groundwater for a long time, in which feldspar is weathered to form kaolin, and some kaolin is leached out to form a cave that looks like a "karst cave". This kind of cave is controlled by the NW-trending fault zone, and the cave has a certain development scale. There are 4 caves in the main roadway, and 20 caves are found in 3 veins (including 4 caves in 27, 3 caves in 29, 3 caves in 13 and 3 caves in 3 1 cave). The largest caves are 2×5m and 2.2× 1.
(3) Mineralization of secondary oxidation zone belongs to a new ore type.
Nine cave weathering residue samples were collected in the field for analysis (Table 7-29). The grade of silver ranges from 241.5×10-6 to 3683.7×10-6, with an average of 998.04× 10-6, in which
Table 7-29 Analysis Results of Weathered Leachate Samples from Some Caves in Jinshiqiang Mining Area