(2) Clastic rock type-Banpo antimony deposit in Dushan, Guizhou.

1. Geological characteristics of mining area

Banpo antimony deposit, located about 14km east of dushan county in southern Guizhou Province, is a large antimony deposit. The deposit is located in the southwest edge of Jiangnan ancient land, between Hunan-Guizhou mercury ore belt and Guangxi Danchi tin-antimony polymetallic ore belt. It has regional metallogenic characteristics and belongs to the transitional antimony ore belt between them (Zhu Xun et al., 1999). It is one of the important antimony producing areas in Guizhou. Antimony and mercury mines (spots) are widely distributed, including Jiabai Antimony Mine, Beida Antimony and Mercury Mine, Banian Antimony Mine and Silver Mine.

Figure 2-4 Schematic diagram of geological and mineral distribution at the south inclined end of Dushan box anticline

(According to Zhong Qiwei 20 12)

1-Upper Devonian; 2- Middle Devonian; 3- Lower Devonian; 4- Lower Silurian; 5- Silurian; 6- Lower Ordovician; 7- Large antimony deposit; 8- medium antimony deposit; 9- Small antimony deposits or occurrences; 10- mercury deposit; 1 1- geological boundary; 12- failure; 13- anticline axis

2. Ore body characteristics

Banpo antimony deposit occurs in clastic rocks on the continental margin of the Lower Devonian Dānlín Formation. The ore-bearing rock series is marine clastic rocks, namely mudstone, siltstone and fine sandstone, and the metallogenic type belongs to clastic antimony deposit. The ore bodies are mainly filled in the fault zone and influence zone of the NNW-trending tension-torsion broom fault group in Banpo, and the main ore bodies are in the form of large veins. The output of ore bodies basically coincides with faults, and the size of ore bodies is positively correlated with the scale of faults (Figure 2-5) (Cui et al., 1995). Ore bodies can be divided into two types, one is vein and saccate occurring at the fault expansion or intersection, and the other is vein group near the main fault. A single ore body is generally 60 ~ 60 ~ 600 meters long, 0.5 ~ 15 meters thick and 80 ~ 450 meters deep. The grade of antimony is about 1% ~ 10%, and the highest grade of antimony in some dense massive ores exceeds 45%.

According to field observation and microscopic identification, the ore structure mainly consists of autogenous needle-like columnar structure and autogenous-semi-autogenous granular structure. Microscopically, veinlet-net vein structure, lumpy twin structure, inclusion structure and interstitial structure can be seen. Ore structures include massive structure, radial structure, veinlet structure, veinlet disseminated structure and breccia structure. The mineral composition is single, the main ore mineral is stibnite, followed by pyrite; Gangue minerals are mainly chronological, followed by calcite, dolomite, barite and clay minerals. It can be seen that gangue minerals are massive or veinlets, forming ore skeleton, and stibnite is distributed in ore in vein or veinlets.

Figure 2-5 Schematic Diagram of Exploration Line Section of Banpo Antimony Mine

(According to Cui et al. 1995)

1-sandstone; 2- shale; 3- limestone; Middle Devonian 4- Dushan Formation; 5- 4 yuan; 6— Silty shale; 7- slope deposit; 8— Fracture and number; 9— Ore body; 10-Lower Devonian Shujiaping Formation; 11-Longdongshui Formation of Middle Devonian; 12- Lower Devonian Dānlín Formation

3. Genetic model

In the early and middle Devonian, the Middle Ages in Guizhou extended eastward and connected with the ancient land in the south of the Yangtze River, and Dushan was located outside Duyun-Kaili Bay. Abundant antimony in tuffaceous slate of Banxi Group on the ancient land was weathered and denuded, and some antimony in the rock was dissolved and migrated, and some antimony migrated to the sea in the form of debris and was initially enriched, and it was deposited with rocks to become the source bed of Middle Devonian, which became the most fundamental material basis in the whole mineralization process. The ore-forming hydrothermal solution in the later period mainly came from atmospheric precipitation, which had a strong oxygen isotope exchange with surrounding rocks during downward infiltration, migration and circulation. The fault structure in the axis of anticline is the main ore-controlling factor, which provides driving force, heat source, migration channel and precipitation space for ore-bearing hydrothermal solution. Vertical faults deepen and increase, and deep matter and heat flow rise. At the same time, atmospheric precipitation permeates downward and merges with bottom water and deep heat flow, continuously dissolving and extracting the ore-forming materials in deep strata and faults, and increasing its salinity and salinity. Driven by Yanshanian tectonic dynamics, ore-forming fluids migrated upward along the fault system and deposited on the steeply inclined fault zone where the temperature and pressure eased sharply, forming a semi-slope steeply inclined vein deposit (Figure 2-6) (Kim Jong Kook and Daitagen, 2007; Qian Jianping et al., 2000; Zhong Qiwei, 20 12).

4. Brief introduction of mineral deposit series specimens

In 20 10, according to the regional metallogenic characteristics and the geological characteristics of Banpo antimony deposit, 18 ore samples were collected in the ore-bearing strata of Dānlín Formation of Lower Devonian by block picking method (Table 2-2), among which 10 ore samples were collected, and the lithology was stibnite, veinlet stibnite and vein stibnite. Collect 5 samples of surrounding rock, whose lithology is dark gray silty mudstone, timely sandstone, quartzite sandstone, fine-grained timely sandstone and argillaceous siltstone; Three samples of mineralized surrounding rocks are collected, and the lithology is mainly stibnite-broken timely sandstone, stibnite-containing timely sandstone and stibnite-mineralized timely sandstone. The samples collected this time basically reflect the geological characteristics of Banpo antimony deposit and the ore types with different structures and different material compositions.

Figure 2-6 Metallogenic Model of Dushan Antimony Deposit

(According to Zhong Qiwei 20 12)

1-Longdongshui Formation of Middle Devonian; 2- Lower Devonian Shujiaping Formation; 3- Lower Devonian Dānlín Formation; 4- ore body; 5- Direction of mineral leaching and mineral liquid migration; 6— Dushan Formation of Middle Devonian

Table 2-2 Specimens Collected from Banpo Antimony Mine in dushan county, Guizhou Province

Note: In the table, Sb2-b represents the specimen of Banpo Antimony Mine in dushan county, Guizhou, Sb2-B represents the thin section number of the specimen, and Sb2-g represents the light section number of the specimen.

Step 5 plate

(1) Specimen photos and their characteristics description

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-B0 1

Antimony ore. The ore is gray, self-shaped, acicular, massive and radial. Mineral stibnite is lead gray, and its stripes (powder) are also lead gray. Automorphic, acicular and columnar crystals, some of which are semi-automorphic-heteromorphic and granular, with a length of 2 ~ 3 cm and a column width of1~ 3 mm. The aggregate is radial and chrysanthemum-shaped, with a content of about 60%, and the surface of the cylinder is often striate (multi-flake and double-grain). The gangue minerals are chronological sandstone, the breccia is fine-grained chronological sandstone, and some of them are white chronological veins filled in the later period. The main mineral composition is timely, with a content of about 40%.

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-B02

Antimony ore. The ore is gray, authigenic-abnormal granular structure and veinlet-veinlet disseminated structure. Ore mineral stibnite, lead gray, authigenic-irregular columnar granular, metallic luster, gray dirty handprint, content of about 5%. The gangue mineral is calcite, which is massive or veinlet-like. Antimony is distributed in the ore in the form of veins or veinlets.

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-B03

Vein stibnite ore is gray-light gray, semi-autogenous-irregular columnar granular structure, veinlet-veinlet disseminated structure. Mineral stibnite is semi-self-shaped-shaped columnar, gray-lead gray, metallic luster, low hardness, dirty hands, veinlets or veinlets embedded in the ore, with a content of 2% ~ 3%. There are three kinds of gangue minerals: quartzite timely sandstone, which constitutes the main body of the ore, is colorless, transparent and round, with obvious secondary edge enlargement, and the cement is also siliceous, with a content of about 85%; Calcite veinlets are composed of meat-red calcite, with a pulse width of 1 ~ 5m and a length of 10cm, distributed in parallel, and the content is about 10%. The chronotropic veins are composed of colorless chronotropic microcrystals, which are closely associated with stibnite veins. Late silicified quartz veins and stibnite veins pass through quartz sandstone and calcite veins.

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-B04

Dark gray silty mudstone. The rock is dark gray, with silty-argillaceous texture and layered structure. The main mineral composition is argillaceous minerals, with a small amount of silt. The hardness of the rock is small, and it is carved into powder by knife, and it does not blister when hydrochloric acid is added. They are all clay minerals, which are difficult to distinguish with the naked eye because of their fine particles.

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-B05

Vein-reticulate vein stibnite. The ore is gray, with authigenic-special-shaped columnar granular structure and vein-net vein structure. The ore mineral is stibnite, which is lead-gray to gray-black, with metallic luster and low hardness, mostly in the form of fine needle-like aggregates, and a few in the form of special-shaped particles or films. Antimony is distributed in the ore in a vein-net vein shape, with a pulse width of 1 ~ 5mm and an irregular direction, with a content of 10% ~ 15%. The gangue minerals are mainly timely sandstone, and the rocks are breccia-like and angular. See the timely and calcite veins filled in the later period. After the mineralization period, there was a structural fracture, which broke the ore, and the stibnite on the fracture surface turned into powder and stained the hands.

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-B06

Antimony mineralized fractured sandstone. Gray, medium-fine grained sandy texture, massive structure. The composition of sand is timely, colorless and transparent, the cement is siliceous, and the rock is slightly metamorphic quartzite, sometimes the grain boundary is unclear and the rock is fractured. Antimony is unevenly distributed in the rocks in the form of veinlets or veinlets, and it is in the form of gray bands or nests, with a content of < 1%.

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-B07

Antimony ore containing pyrite. The ore is gray, authigenic-abnormal granular structure and massive structure. The ore mineral is mainly stibnite, which is lead-gray with metallic luster. Most of them are self-shaped short columnar or long columnar crystals, and some of them are heteromorphic granules. The transverse twin of the crystal column is very developed, and its content is about 30%. Followed by a small amount of pyrite, the content is 1% ~ 2%. The gangue minerals are mainly siliceous cemented quartzite sandstone, and small time veins or small aggregates filled in the later period can also be seen in the rocks.

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-B08

Seasonal sandstone. The rock is grayish white, with medium-fine grained sandy texture and massive structure. The main mineral composition is quartz sand, mostly colorless and transparent, with fine particles, and the cement is also siliceous, colorless and hard, and does not foam when dripping acid. There are two types of cementation: pore type and basement type. The content of quartz sand is about 60%, the content of cement is nearly 40%, and the rock is slightly metamorphic with secondary quartzitization. These rocks contain trace amounts of black minerals.

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-B09

Antimony ore. The ore is gray-light gray-white, self-shaped-shaped columnar granular, veinlet-like and veinlet-disseminated. The ore mineral is stibnite, lead-gray, authigenic-heteromorphic granular crystal. The grain size is generally 1 ~ 3mm, and some of them can reach10 mm. Mineralization fills along the fault, and sometimes it fills both sides of the vein. Sometimes there are secondary small cracks beside them, which are filled by mineralization, with a content of 5% ~ 8%. Gangue minerals are timely sandstone, siliceous cementation and secondary quartzitization. Small and medium cracks are developed in the ore, and limonite is disseminated along the small cracks.

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-B 10

The breccia stibnite ore is gray, authigenic-abnormal granular structure and breccia structure. The ore mineral is stibnite, with lead gray, authigenic-heteromorphic particles, see 1mm×5mm crystal, and the content is about 10%. Timely sandstone breccia is cemented in the form of cement. The gangue mineral is light gray fine-grained timely sandstone. There are trace pyrite in rocks and ores, and limonite oxides are common on fractures.

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-B 1 1

Timely sandstone containing stibnite vein. Seasonal sandstone, gray, medium-fine grained sandy texture, fissure texture, massive texture and vein texture. Stibnite is veined (only one vein is seen at the edge of the ore), in which stibnite has good self-crystallization, needle-shaped, lead-gray, particle size of 2mm× 10mm, and content of 5% ~ 10%. Gangue minerals are mainly timely sandstone, no other minerals are found, and uneven fine-grained pyrite can be seen in sandstone.

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-B 12

Shi Ying sandstone. The rock is grayish white, with medium-fine grained sandy texture, residual sandy texture and massive structure. Quartz sand is fine, accounting for about 60%. The cement is siliceous, the rock is slightly deteriorated, the cement is recrystallized, and the secondary edge expansion of quartz sand particles is obvious.

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-B 13

Antimony ore. The ore is gray-lead gray, with coarse-grained structure and massive structure. The ores are all composed of stibnite, gray-lead gray, columnar, with a few needles, a group of cleavage developed, and the transverse twin of cylinder is very developed, with a content of about 95%. The ore contains timely sandstone breccia, accounting for about 5%.

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-B 14

Antimony ore. The ore is gray, authigenic granular, veined and veined. The ore mineral is stibnite, which is lead-gray, metallic luster, and occurs as a vein from a columnar aggregate. The pulse width is 3 ~ 10 mm, and the extension is unknown. Branching and compounding phenomena can be seen, and the content of stibnite is 4% ~ 5%. The rest are quartzite fine sandstone, gray, medium-fine grained sandy texture, residual sandy texture and massive texture. The rock is broken and the surface is scratched.

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-B 15

Antimony mineralization in seasonal sandstone. The rock is gray-light green gray, with medium-fine grained sandy texture and massive structure. The main mineral is timely, colorless and fine particles. Cements include siliceous cementation, basement cementation and pore cementation. Quartz sand particles and cements are both siliceous, and the timely content is about 98%. Antimony, lead gray, metallic luster, low hardness, self-columnar or irregular fine particles, full of irregular textures in rocks. The vein body is small in scale and irregular in direction, with a content of about 2%.

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-B 16

Fine grained timely sandstone. The rock is gray, with fine-grained sandy structure and massive structure. Sandy components are all fine-grained, with a particle size of 0. 1 ~ 0.5 mm, colorless and transparent. The cement is siliceous, which is base cementation and pore cementation. Minerals in rocks are uniform in particle size and single and stable in color. We can see the timely veinlets containing pyrite with a pulse width of about 65438 0 mm, which run through the sample.

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-B 17

Vein stibnite ore is gray, with medium-grained autotype-heteromorphic structure and vein structure. The ore mineral is stibnite, gray-lead gray, authigenic columnar crystal, and the aggregate is radial, and the crystal with the size of 2mm×30mm can be seen. On the cleavage plane, striations are developed, mineralization is vein-like, width is 1 ~ 3 mm, extension is unknown, and the content is about 10%. The main body is fine-grained timely sandstone with calcite veins. There are scratches on the surface of the ore, and the stibnite on the scratched surface is powdery, which will dirty hands.

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-B 18

Silty siltstone The rock is dark gray, with silty-argillaceous texture and fine-grained layered structure. The main components are argillaceous and fine sand, and the mineral particles are fine, so it is impossible to distinguish the mineral type and particle size content with naked eyes. Adding hydrochloric acid does not foam (rock powder)

(2) Specimen identification photos and description of their characteristics under microscope.

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-b08

Seasonal sandstone. Fine-grained structure, massive structure. The main mineral components are Yingshi (Q z, about 75%) and plagioclase (Pl, about 20%). Plagioclase, triclinic system, colorless, negative low protuberance, developing flaky twins. In time, it is colorless and transparent, with smooth surface, no weathering, high and low protrusions, cleavage and crystallization, with a particle size of 0.2-0.5 mm.

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-g0 1

The main metal minerals are stibnite and a small amount of pyrite, with occasional carbonaceous components. The content of stibnite (Snt) is about 2%, with irregular granular structure and filled with transparent mineral particles. Polyhedral twins are common, and the aggregates are embedded in transparent mineral particles in the form of veins, with a particle size of 0.002 ~ 2.0 mm. Pyrite (Py) is a small amount, with a self-shape-semi-self-shape granular structure and a cubic crystal cross-section with a particle size of 0.01~ 0.1mm.

Mineralization sequence: pyrite → carbonaceous → stibnite.

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-g03

The main metal minerals are stibnite and a small amount of pyrite. The content of stibnite (Snt) is about 5%, with irregular granular structure and filled with transparent mineral particles. Flake twins are common. Aggregates are veined in transparent mineral particles with a particle size of 0.002 ~ 2.0 mm. Pyrite (Py) is a small amount, with a self-shape-semi-self-shape granular structure, cubic and pentagonal dodecahedron crystal cross sections, and some of them are distributed with an irregular granular structure with a particle size of 0.005 ~ 0.2 mm..

Mineralization sequence: pyrite → stibnite.

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-g09

The main metal minerals are stibnite and pyrite. The content of stibnite (Snt) is about 65,438 0%, with irregular granular structure and filled with transparent mineral particles. Usually there are small flake twins, and the aggregates are scattered in transparent mineral particles in the form of veinlets-reticular veins. It can be seen locally that the metasomatic body contains pyrite particles with a particle size of 0.002 ~ 0.6 mm, and the content of pyrite (Py) is about 65,438 0%, with a self-shape and semi-self-shape granular structure. The crystal cross section is cubic and pentagonal dodecahedron, and some of them have a special-shaped granular structure, which is replaced by stibnite as residual particles with a particle size of 0.005 ~ 0.2 mm

Mineralization sequence: pyrite → stibnite.

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-g 13

The main metal mineral is stibnite, and no other metal minerals are found. The content of stibnite (Snt) is about 99%, with irregular granular structure distribution. Veins can be seen locally, mixed with transparent mineral particles, and common flaky twins with a particle size of 0.002 ~ 0.6 mm.

Mineralization sequence: stibnite

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-g 15

The main metal minerals are stibnite and a small amount of pyrite particles. The content of stibnite (Snt) is about 5%, with irregular granular structure distribution. It can be seen that the aggregate is veinlets-reticular veins, mixed with transparent mineral particles, and there are usually small flake twins with particle size of 0.002 ~ 2.0 mm. A small amount of pyrite (py) is distributed in transparent minerals in semi-autotype-allotropic granular structure with particle size of 0.002 ~ 0.03 mm..

Mineralization sequence: pyrite → stibnite.

Series of specimens and optical slices of typical deposits in China. Lead-zinc-antimony-silver-gold deposit

Sb2-g 17

The main metal minerals are stibnite and a small amount of pyrite particles. The content of stibnite (Snt) is about 2%, with irregular granular structure distribution. It can be seen that the aggregate is veinlet-reticulate vein, mixed with transparent mineral particles, and it is a common flaky twin with a particle size range of 0.002 ~ 65438 0.0 mm. A small amount of pyrite (py) is distributed in transparent minerals in a self-form-semi-self-form granular structure, with a cubic crystal cross section and a particle size of 0.002 ~ 0.2 mm.

Mineralization sequence: pyrite → stibnite.