(II) Copper-nickel sulfide type-Jinchuan (Baijiazuizi) copper-nickel mine in Gansu Province

1. Geological characteristics of mining area

Jinchuan copper-nickel mine in Gansu Province is located in jinchang, Gansu Province. It is a world-class super-large copper-nickel sulfide deposit, rich in polymetallic symbiotic minerals such as cobalt, platinum, palladium, gold and silver. The reserves of nickel and platinum group metals in the deposit rank first in China, and the reserves of copper and cobalt rank second in China.

Jinchuan copper-nickel deposit was formed in the dome-shaped uplift stage in the early Mesoproterozoic, and the geotectonic structure is located in the south edge of Longshoushan uplift belt in the southwest edge of Alashan block in North China (Figure 3-4). There are more than 20 mafic-ultramafic rocks and several intermediate-acidic rocks in the southern margin of Longshoushan uplift belt. The NW-trending rocks turn to the Near East, extending about 200km from east to west to the Longshoushan tectonic magmatic rock belt, and Jinchuan deposit is at its structural turning point. The structure in the mining area is developed, mainly northwest and east-west faults, folds and joints. F 1 fault is a deep fault (also called Chaonan fault) in the northern margin of Longshou Mountain, and it is the dominant fault of diagenesis and mineralization (Fu Kaiquan et al., 2006; Gao Hui et al., 2009; Sun Guiyu,1990; Meilan Wen et al, 2013; Tian Yulong et al., 2008).

Figure 3-4 Regional Geological Map of Jinchuan Copper-Nickel Deposit (according to Gao Hui et al., 2009)

1- Cenozoic deposits; 2- Mesozoic continental clastic rocks; 3- Early Paleozoic continental clastic rocks; 4- Late Paleozoic flysch formation; 5- Mesoproterozoic carbonate rocks and clastic rocks; 6- Proterozoic metamorphic rock series (pre-Great Wall series); 7- mixed granite; 8- granite; 9- granodiorite; 10— Jinchuan copper-nickel ore group and Fe-Mg ultraFe-Mg rock mass (group); 11-measured and presumed faults.

2. Ore body characteristics

Ore-bearing ultrabasic rocks intrude between migmatite and marble of Archean Baijiazuizi Formation along the secondary structure of deep fault. According to the genetic types of ore bodies, they can be divided into five types: magmatic in-situ detachment type ore bodies, magmatic deep detachment-penetration type ore bodies, late penetration type ore bodies, contact metasomatic type ore bodies and hydrothermal superimposed type ore bodies (Figure 3-5) (Gao Hui et al., 2009). The main ore body occurs in pure peridotite and lherzolite, which is layered and lenticular, and a few veins invade the lower part of the rock mass (Figure 3-6). The scattered suspended ore bodies are irregular nests, and the ore bodies and surrounding rocks gradually transition; Veins are mainly produced in intermittent veins in structural fractures of rock mass, with a width of several centimeters to 30 centimeters.

Figure 3-5 Geological Map of Jinchuan Copper-Nickel Deposit

(According to Ye Liang Shandeng 20 13)

1- four yuan; 2- striped migmatite; 3- marble; 4- Gneiss containing durian; 5— Homogeneous migmatite; 6- biotite plagioclase gneiss; 7- migmatite; 8— Mixed granite; 9- late granite; 10-ultrabasic rock mass; 1 1- geological boundary; 12- Fault

Figure 3-6 Schematic diagram of 50 rows of shear zones in Jinchuan Copper-Nickel Mine Ⅱ mining area

(According to Gao Hui et al., 2009)

1- four yuan; 2- mafic-ultramafic intrusions; 3- disseminated ore body; 4- reticular vein-rich ore body; 5- contact metasomatic ore body; 6- shear band; 7-Drilling and numbering

According to field observation and microscopic identification, the ore structures are mainly sponge meteorite-like, fine-medium-coarse-grained, star-shaped and metamorphic structures. Various replacement and filling structures are common under the microscope. The main structures of ore bodies are sparse disseminated, dense disseminated, veinlets and massive structures. The hanging lean ore body is composed of star-shaped lean ore, and the veins are mainly reticulate and massive structures. The ore minerals are mainly pyrite, pyrrhotite, chalcopyrite, nickel pyrite and magnetite, followed by hematite, ilmenite, chromite and chromite spinel, accompanied by a small amount of gold and platinum. Rock-forming minerals are mainly pyroxene and olivine, followed by tremolite, diopside, calcite and a small amount of chlorite.

3. Genetic model

Jinchuan copper-nickel deposit is a deep magmatic detachment-composite penetrating deposit (Fu Kaiquan et al., 2006). Ore-bearing magma melts and differentiates in the deep and emplaces in turn, forming a layered structure of magma, ore-bearing magma, ore-rich magma and pulp (Figure 3-7). The controlling factors of mineralization are mainly divided into homologous magma control and late tectonic control. The control of homologous magma is characterized by lithofacies differentiation and layered structure of ore-bearing ultrabasic rocks. The late structure controls both the emplacement of ore-bearing rock mass and the spatial position of ore body. Metamorphic deformation of intrusions is mainly controlled by late structures, and to some extent determines the geometric shape, occurrence and related mineralization and distribution of intrusions (Gao Hui et al., 2009).

Figure 3-7 Jinchuan Rock Intrusion Pattern Diagram

(According to Gao Hui et al., 2009)

1-peridotite; 2- lherzolite; 3- dunite; 4- plagioclase lherzolite; 5- olivine pyroxenite; 6- metasomatic ore body; 7- reticular vein ore body; 8- massive sulfide ore body

4. Brief introduction of mineral deposit series specimens

20 13 according to the outcropping stratum characteristics, spatial distribution of ore bodies, genetic types and surrounding rock properties of Jinchuan copper-nickel deposit, 20 samples were collected in I, II and IV mining areas by fixed-point block picking method (Table 3-2). Among them, there are 9 poor and rich ores in the acquisition area, and the lithology includes ultrabasic magmatic copper-nickel ore, pyrite ore and ultrabasic rock-type copper-nickel ore; Eight samples of surrounding rocks are collected, and the lithology is pyroxene peridotite, banded granite migmatite, amphibole, marble, biotite plagioclase gneiss and granodiorite porphyry. Collect 2 samples of altered surrounding rock, the lithology is serpentine marble and banded migmatite; 1 block mineralized rock is collected, and its lithology is olivine gabbro containing pyrite. This episode basically covers the typical specimens of exposure and drilling control in the whole region.

Table 3-2 Samples Collected from Jinchuan Copper-Nickel Mine in Gansu Province

Note: In the table, Cu2-b stands for Jinchuan copper-nickel mine specimen, Cu2-B stands for thin section number of specimen, and Cu2-g stands for light section number of specimen.

Step 5 plate

(1) Specimen photos and their characteristics description

Cu2-B0 1

Ultra-basic magmatic copper-nickel ore. The ore is gray-black, spongy meteorite structure, dense disseminated and massive structure. Ore minerals are mainly pyrite, pyrrhotite and nickel pyrite, with a small amount of chalcopyrite. Pyrite, yellow-yellow-white, metallic luster, semi-self-shaped-shaped granular; Pyrrhotite, weak magnetism; The total content of nickel pyrite and bronze yellow is 25% ~ 30%. Chalcopyrite, copper yellow-bright yellow, metallic luster, irregular fine grain structure, content of about 65438 0%. The ore-bearing rocks are peridotite or pyroxenite. The rock is gray-black, with medium-coarse grain structure and massive structure. The main mineral is pyroxene, the content is about 70%, and fine pyrite is filled in the grain gap, showing sponge meteorite structure. Occasionally olivine

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-B02

Ultrabasic rock type copper-nickel ore. The ore mineral is pyrite with a small amount of nickel pyrite. Pyrite, yellow-yellow white, metallic luster, irregular fine-grained structure, content of 4% ~ 5%. Nickel pyrite, bronze yellow, metallic luster, content of about 65438 0%. The ore-bearing rocks are olivine pyroxenite, gray-black, medium-coarse grained and massive. The main rock-forming mineral is pyroxene, followed by olivine. Pyroxene is brownish black, grayish white and light gray, and there may be two kinds of pyroxene and diopside, both of which are plate-shaped and columnar, with a particle size of 1 ~ 5 mm and a content of about 70%. Olivine, green-light green, semi-automorphic-heteromorphic granular, with a content of about 20%.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-B03

Pyroxene peridotite rocks are bluish-gray, with medium-fine grain structure and massive structure, with schistose structure in some areas. The main mineral components are olivine, a small amount of pyroxene and amphibole. Olivine, green-light green, glassy, semi-automorphic-heteromorphic fine-grained, with a particle size of about 1mm and a content of about 60%, with some serpentine. Pyroxene and amphibole, black-green-black, fine-grained structure, columnar-long columnar, with a content of about 30%. A small amount of unevenly distributed pyrite can be seen in the rock, with yellow-yellow white, autotype-allotype fine-grained structure, metallic luster, content of 2% ~ 3%, and occasional pyrite veinlets.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-B04

Banded granite migmatite The rock is dark meat red, with medium-coarse crystalline structure and banded structure. The main mineral components are potash feldspar and quartz, with a small amount of biotite and chlorite. Potash feldspar, fleshy red, glassy, authigenic, with a particle size of 5 ~ 10~20mm, the maximum is 10~20mm, and the content is about 60%. It is colorless, transparent, oily, granular and sometimes directional, with a content of about 20%. Biotite and chlorite, black-green-black, fine scaly, partly chloritization, with the content of 15% ~ 20%, constitute dark bands. Potassium feldspar and quartz form light-colored bands. Light and dark stripes are alternately distributed, forming a banded structure.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-B05

Oblique amphibolite rocks are dark gray, with fine-grained crystalline structure and massive structure. The main mineral components are plagioclase, amphibole and a small amount of biotite. Plagioclase, white, glassy, hemimorphic-heteromorphic, fine-grained, particle size < 1 mm, content about 50%. Hornblende, black, green-black, authigenic-heteromorphic granular structure, particle size < 65438±0mm, content about 35%. Biotite, brownish black, fine flake, flake diameter < 1 mm, content 5% ~ 10%. Trace semi-crystalline pyrite is distributed along the fault surface.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-B06

Marble. The rock is pure white with medium-fine grain crystal structure and massive structure. The rocks are almost entirely composed of calcite, which is white, glassy, rhombic, cleavage developed, medium-fine grained and coarse grained in some areas. Dilute hydrochloric acid foams strongly, with a content of > 95% (maybe some dolomite). Scattered serpentine can be seen in the rock, which is beige, brown, light green, waxy and granular, with the content of < 1%.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-B07

The biotite plagioclase gneiss is gray, medium-grained metamorphic, banded and gneiss. The main mineral components are plagioclase and quartz, with a small amount of potash feldspar and biotite. Plagioclase is white, light grayish white, glassy, self-shaped-shaped columnar, with a particle size of about 2mm, and the aggregate is mostly punctate, with a content of about 60%. In time, it is colorless, transparent, shiny, irregular and granular, with a content of 20% ~ 25%. Biotite, black, scaly aggregate, directionally distributed in strips, with a content of about 15%. Potassium feldspar, fleshy red, granular, mostly metasomatic plagioclase, unevenly distributed, with a content of about 5%. The dark mineral biotite is composed of dark bands, which are alternately distributed with feldspar and timely bright bands to form a banded structure.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-B08

Serpentine marble rocks are light gray-green, medium-grained metamorphic structure, massive and banded structure. The main mineral components are calcite and serpentine, with a small amount of chlorite. Calcite, white, glassy, semi-automorphic-heteromorphic granular, with a particle size of 2 ~ 4 mm and a content of 50% ~ 60%. Serpentine, yellow-green-grass-green, waxy luster, lower hardness than knife, autotype-heteromorphic granular, particle size 1 ~ 3 mm, content about 30%. The local direction distribution is banded. Chlorite, black, irregular granular, uneven distribution, content < 10%. There are also scattered muscovites in the rocks, with a content of about 65438 0%.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-B09

Ultra-basic magmatic nickel ore. The ore is black, sponge meteorite structure, disseminated structure and massive structure. The ore minerals are pyrite and nickel pyrite, with a content of about 8%. Pyrite, yellow-white, silvery gray-white, with irregular fine-grained structure. Nickel pyrite, light bronze color, irregular fine-grained structure. The ore-bearing rocks are pyroxenite with olivine, medium-grained structure and massive structure. The main mineral components are pyroxene and a small amount of olivine, with a content of about 80%. Pyrite, black, authigenic-heteromorphic granular structure. Olivine, green, special-shaped particles

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-B 10

Ultra-basic magmatic copper-nickel ore. The ore minerals are pyrite and nickel pyrite, with sponge meteorite structure, dense disseminated structure and strong magnetism. Pyrite, yellow-white, silvery gray-white, metallic luster, special-shaped fine-grained structure. Nickel pyrite, bronze yellow, metallic luster, irregular fine grain structure, content of about 20%. There is also a small amount of chalcopyrite, copper yellow, metallic luster and irregular granular structure. The ore-bearing rocks are pyroxenite, olivine pyroxenite, medium-grained texture and massive texture. The main mineral components are pyroxene and trace olivine, with a content of about 80%. Pyroxene, black glass luster, authigenic-heteromorphic granular structure.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-B 1 1

Ultra-basic magmatic copper-nickel ore. The ore is black, sponge meteorite structure, dense disseminated and massive structure. The ore minerals are pyrite, nickel pyrite and chalcopyrite, with a content of 20% ~ 25% and strong magnetism. Pyrite, yellow-white, metallic luster, irregular fine-grained structure, content of about 65438 05%. Nickel pyrite, bronze yellow, metallic luster, other shapes of fine particles, content of about 5%. Chalcopyrite, copper yellow, metallic luster, irregular fine grain structure, content of 3% ~ 5%. The ore-bearing rocks are pyroxenite with olivine, medium-grained structure and massive structure. The main rock-forming minerals are pyroxene and trace olivine.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-B 12

Marble. The rocks are milky white, coarse-grained and massive. The mineral composition is almost all calcite, white, glassy, authigenic-semi-authigenic coarse-grained structure, particle size of 0.5 ~ 3cm, rhombic cleavage development, content > 99%, and no other minerals are found.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-B 13

Banded migmatite The rock is dark flesh red, with medium-fine crystalline structure, massive structure and slightly banded structure. The main mineral components are potash feldspar, quartz and plagioclase, with a small amount of biotite. Potassium feldspar, flesh red, glassy luster, irregular medium-grained structure, particle size of 2 ~ 4 mm, content of about 65%. It is colorless and transparent, oily, irregular and granular, with a particle size of 1 ~ 3mm and a content of about 20%. Irregular timely veinlets are locally developed and distributed in the form of milk drops in potash feldspar. Plagioclase, white, glassy, semi-autotype-heteromorphic granular, particle size 1 ~ 3 mm, content 10% ~ 20%. Biotite, dark brown, fine scale-like, directionally distributed, forms dark bands in time, and then alternately distributes with red potash feldspar to form banded structure, with the content less than 5%.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-B 14

Granodiorite porphyry. The rock is gray-light gray, with medium-fine grained porphyritic structure and massive structure. Porphyry is about 40%, mainly composed of plagioclase, amphibole and biotite. Plagioclase, white and grayish white, glassy, autotype-semi-autotype granular, particle size 1 ~ 2mm, content about 15%. In time, it is colorless, transparent, oily and shiny, with irregular granule size 1 mm and content of about 20%. Hornblende, black, slender column. Biotite, dark brown, flaky, with a content of about 5%. The matrix is fine-grained aphanitic, consisting of feldspar and timely particles, with a content of about 60%.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-B 15

Pyrite-bearing olivine gabbro The rock is black, fine-grained and massive. The main mineral components are pyroxene, a little olivine and a little pyrite. Pyroxene, black, glassy, authigenic-heteromorphic fine-grained structure, particle size 1 ~ 2mm, content about 80%. Olivine, light green-dark green, semi-automorphic-heteromorphic granular, with a particle size of about 1mm and a content of about 10%. Pyrite and pyrrhotite are yellowish white with metallic luster. When the content of pyrite is low, it is an irregular granular structure, and when the content is high, it is a weakly magnetic sponge meteorite structure.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-B 16

Ultra-basic magmatic copper-nickel ore. The ore is black, and the minerals are pyrite, pyrrhotite, nickel pyrite and a small amount of chalcopyrite, with a content of about 10%, which is weak in magnetism. Pyrite has a filamentous structure, and its pores are filled with pyroxene particles, forming a sponge meteorite structure. The ore-bearing rocks are pyroxenite with medium-fine grain structure and massive structure. Rock-forming minerals are almost all composed of pyroxene, which is black, glassy and autotype-isomorphic, with a content of 85% ~ 90%.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-B 17

Ultra-basic magmatic copper-nickel ore. The ore is black, and the minerals are pyrite, pyrrhotite, nickel pyrite and trace pyrite, with a total content of about 10% and weak magnetism. The ore-bearing rocks are olivine pyroxenite, black, fine-grained and massive. The main mineral components are pyroxene and a small amount of olivine. Pyroxene, black, glassy, authigenic-heteromorphic fine-grained structure, particle size 1 ~ 2mm, content about 80%. Olivine, green, glassy, autotype-heteromorphic medium-grained structure, particle size 1 ~ 2mm, content about 10%.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-B 18

Pyrite ore. The ore is yellow-light yellow, and the weathered surface is brown, with other fine-grained structures and massive and dense disseminated structures. Ore minerals are mainly pyrite and pyrrhotite, with a small amount of chalcopyrite and magnetite. Pyrite, yellow-white-silvery gray-white, with irregular fine-grained structure, metallic luster, containing pyrrhotite with weak magnetism, with a content of about 80%, and pyrite veins filled in the later period can be seen, with a pulse width of 1 ~ 2mm. Chalcopyrite, copper yellow, metallic luster, irregular fine grain structure, content < 5%. A small amount of magnetite is bluish gray. Gangue minerals include olivine, pyroxene and chlorite with the content of 15% ~ 20%.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-B 19

Ultrabasic rock type copper-nickel ore. The ore is grayish yellow-grayish black, with irregular fine grain structure, sponge meteorite structure, veinlets, dense disseminated and massive structure. Ore minerals include pyrite, copper-bearing pyrite, pyrrhotite and nickel pyrite, with a total amount of 80% ~ 90% and strong magnetism. When it is disseminated, the pyrite content is only 30%. The ore is dominated by massive structure, with pure pyrite lumps and pyrite veinlets locally developed. Gangue minerals are low in content, mainly amphibole and pyroxene, in the form of black long columnar crystals, and the content is less than 10%.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-B20

Diopside diopside skarn rocks are bluish gray, with medium-grained metamorphic structure and massive structure. The main mineral components are tremolite, diopside, calcite and a small amount of chlorite. Tremolite and diopside are closely symbiotic, green-gray, glassy, self-shaped, long columnar and granular, and the aggregate is fibrous and radial, with low hardness and content of 60% ~ 70%. Calcite, white, glassy, heteromorphous granular, banded distribution, foaming violently with dilute hydrochloric acid, with a content of about 30%. Chlorite, green-gray-green-black, granular in other shapes, content < 5%. Sparse fine-grained and fine-grained pyrite can be seen in the rock, with the content of < 1%.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

(2) Specimen identification photos and feature description under microscope.

Cu2-b 13

Mixed rock. Granular structure, massive structure. The main mineral components are Yingshi (Qz, about 45%), potash feldspar (Kfs, about 30%), plagioclase (Pl, about 20%) and a small amount of amphibole (Amp, about 3%). The quartz with irregular grain structure has a grain size of about 0.4 mm ... K feldspar, negative low protrusion, inconspicuous lattice twin and oblique extinction. Plagioclase, semi-autogenous plate, negative low protrusion, obvious twin development, zonal, hornblende with particle size of about 0.5 ~ 1 mm, long column, hornblende cleavage, obviously multicolor.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-b20

Translucent serpentine schist. Scale metamorphic structure, schistose structure. The main mineral components are serpentine (Chr, about 70%) and diopside (Di, about 25%). Serpentine, fibrous, scaly, colorless-light green, weakly polychromatic, positive and low protruding, with interference color ranging from Grade I gray to Grade I yellow-white. Diopside, short column, no multicolor, high interference color, protruding height, particle size of about 0.5 ~1mm.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-g 10

The main metal minerals are pyrrhotite, chalcopyrite, nickel pyrite, magnetite, chromite, ilmenite, hematite and purple nickel ore. The content of pyrrhotite (Po) is about 65,438+0.5%, and it is in an irregular granular and vein structure with a particle size of 0.65,438+0 ~ 5 mm. It is distributed in transparent minerals in the form of sponge meteorite or interstitial structure, with developed fractures. The content of chalcopyrite (Ccp) is about 8%, with a semi-autotype-heteromorphic granular or vein structure, with a particle size of 0. 1 ~ 3 mm, coexisting with pyrrhotite, with developed fractures. The content of nickel pyrite (Pn) is about 5%, with a semi-autotype-allotropic granular structure, and the particle size range is 0. 1 ~ 2mm, most of which are associated with pyrrhotite and chalcopyrite. Magnetite (Mag) content is about 3%. In the early stage, it was authigenic-semi-authigenic granular structure with a particle size of 0. 1 ~ 0.5 mm, which was dissolved by pyrrhotite and chalcopyrite in the residual structure, and in the later stage, it was mostly irregular vein or block. The content of chromite is about 0.3%, and it has a self-shape-semi-self-shape granular structure. A small amount of ilmenite, hematite and purple nickel ore.

The sequence of mineral formation: chromite → magnetite, ilmenite → chalcopyrite, pyrrhotite, nickel pyrite → magnetite → hematite, purple nickel ore.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-g 1 1

The main metal minerals are pyrrhotite, chalcopyrite, magnetite and nickel pyrite, with a small amount of chromite, natural gold and purple-sulfur nickel ore. The content of pyrrhotite (Po) is about 20%, showing irregular granular structure and vein structure, and the particle size is 0. 1 ~ 5 mm, which is filled between transparent minerals in the sponge meteorite structure and cracks are developed. The content of chalcopyrite (Ccp) is about 65,438+00%, with irregular granular and vein structure, and the particle size is 0.65,438+0 ~ 5 mm, with developed fractures, which were filled and dissolved by magnetite in the later stage. The content of nickel pyrite (Pn) is about 5%, showing a semi-autotype-heteromorphic granular structure. Magnetite metasomatism, reticulate vein structure, developed fractures, coexisting with chalcopyrite, pyrrhotite and purple nickel ore, with particle size of 0. 1 ~ 2mm. The content of magnetite (Mag) is about 3%, and it has an authigenic-semi-authigenic granular structure in the early stage, with a particle size of 0. 1 ~ 0.5 mm, and a residual structure after sulfide dissolution in the later stage. Natural gold and chalcopyrite can be seen in some fractures, and sulfide is dissolved in the later stage. A small amount of natural gold (Gl) is irregularly granular and veinlet-like, with a particle size of 20 ~ 50μ m, and a small amount of chromite (Chr) and violet nickel (Vil).

The sequence of mineral formation: chromite → magnetite → natural gold, chalcopyrite → pyrrhotite, nickel pyrite → purple pyrite → magnetite.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-g 15

The main metal minerals are pyrrhotite, chalcopyrite and magnetite, followed by hematite, nickel pyrite and ilmenite, and occasionally purplish red nickel ore. The content of pyrrhotite (Po) is about 6%, and it has an irregular granular or vein structure with a particle size of 0.1~ 3 mm. It coexists with chalcopyrite and nickel pyrite, and is dissolved by later occupied magnetite. The content of chalcopyrite (Ccp) is about 2%, and it has a semi-automorphic-heteromorphic granular or vein structure, with a particle size of 0. 1 ~ 2mm. Symbiotic with pyrrhotite and nickel pyrite, and later replaced and dissolved by magnetite. The content of magnetite (Mag) is about 65,438+0%, and it has an authigenic-semi-authigenic granular structure in the early stage, with a particle size of 0.65,438+0 ~ 65,438+0 mm, and it is filled in the early sulfide fractures in the later stage in the form of veins. Hematite (Hem) is small, with irregular or vein structure, particle size of 0. 1 ~ 0.05 mm, and local bending deformation and buckling. It contains a small amount of nickel pyrite, showing granular structure, and the particle size is 0.1~1mm. A small amount of ilmenite (Ilm) has a self-shape-semi-self-shape granular structure with a particle size of 0.0 1 ~ 2mm. One ilmenite has a semi-automorphic granular structure, and the other is a plate-like automorphic crystal dissolved in early magnetite. A small amount of purple pyrite and metasomatic nickel pyrite.

Mineralization sequence: magnetite, ilmenite → pyrrhotite, nickel pyrite, chalcopyrite → magnetite → purple nickel sulfide ore, hematite.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-g 18

The main metal minerals are pyrite, pyrrhotite and hematite, followed by chalcopyrite and magnetite. Pyrite (Py) content is about 40%, which is in the form of autotype-semi-autotype granular or coarse vein structure, with a particle size of 0. 1 ~ 5 mm, coexisting with pyrrhotite and chalcopyrite, with many pits on the surface and developed cracks, and some of them are cemented by hematite. The content of pyrrhotite (Po) is about 35%, with a semi-autotype-allotype granular structure, with a particle size of 0. 1 ~ 3 mm and developed fractures. Hematite (Hem) content is about 10%, which is a veined, variegated or irregular granular aggregate with a particle size of 10 ~ 100 micron, indicating that magnetite and sulfide are marginal structures. The content of chalcopyrite (Ccp) is about 5%, with granular or massive structure, and the particle size is 0. 1 ~ 5 mm, which is dissolved by magnetite or hematite in the later stage. Magnetite (Mag) content is about 3%, and it has an automorphic-semi-automorphic granular structure in the early stage, with a particle size of 0. 1 ~ 1 mm, and it is dissolved by sulfide in the later stage, showing a residual structure.

Mineralization sequence: magnetite → pyrite, pyrrhotite, chalcopyrite → magnetite → hematite.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.

Cu2-g 19

The main metal minerals are pyrrhotite, nickel pyrite and chalcopyrite, followed by chalcopyrite, purple nickel ore and hematite. The content of pyrrhotite (Po) is about 55%, and it has a massive or semi-autotype-heteromorphic granular structure, with a particle size of 0. 1 ~ 10 mm, cleavage or fracture development, and closely coexists with chalcopyrite and nickel pyrite, so it can be seen that nickel pyrite and chalcopyrite are interspersed in veins. The content of nickel pyrite (Pn) is about 30%, which is a semi-autotype-heteromorphic granular aggregate or vein structure, with a particle size of 0. 1 ~ 10 mm, and cracks are developed, so it is replaced by purple pyrite. The content of chalcopyrite (Ccp) is about 65,438+00%, which is in the form of vein or irregular granular aggregate with a particle size of 0.65,438+0 ~ 3 mm, and forms an immiscible continuous crystal with chalcopyrite. The content of chalcopyrite (cut) is about 2%, and there are many scratches, which often coexist with pyrrhotite and nickel pyrite. A small amount of purple nickel sulfide (Vil) and hematite (Hem) are filled in the cleavage or cracks of pyrrhotite in discontinuous veinlets.

The sequence of mineral formation: pyrrhotite, nickel pyrite, chalcopyrite → purple nickel sulfide and hematite.

Series of specimens and optical slices of typical deposits in China. Tungsten, molybdenum and copper.