Jiamusi micro-landmass is located in the northeast of Heilongjiang, and it is connected with Russia's Breya landmass (Turan landmass) in the north. This is a continent with a large crystal base and an older age. The periphery of the micro-landmass is bounded by faults, and the west boundary is the Jielie River fault of Tangwang in Mudanjiang, which is adjacent to Zhangguangcailing (fold belt). The southern boundary is bounded by Dunhua-Mishan fault and Yanbian fold system, and the eastern boundary is Tongjiang-Dangbi section and Nadanha Daling terrane.
Proterozoic metamorphic basement of Jiamusi micro-block can be divided into two groups: Mashan Group in the lower part and Dongfeng Group in the upper part.
Mashan Group is mainly composed of deep metamorphic schist, sillimanite-bearing garnet gneiss, graphite-bearing gneiss, marble and granulite (containing a small amount of hypersthene), and contains graphite, phosphorus, sillimanite and other deposits. The metamorphic degree of Mashan Group reaches high amphibolite facies to granulite facies, and at the same time it suffers from migmatization of granitic magma, with complex deformation. The original rock is medium-basic volcanic rock-hard sandstone formation or flysch formation (Dong Shenbao et al., 1986). The Pb-Pb isochron age is 2269±68Ma, and the whole rock U-Pb isochron age is 2251360ma (Jiang Zhe et al., 199 1).
Dongfeng Mountain Group is exposed in Hegang area in the north of Musi Micro-land in Yoga Yu. This formation is mainly composed of marble, sericite quartz schist, eryun quartz schist, eryun adamellite, electric quartzite, biotite adamellite schist, siliceous schist and graphite schist, with iron-bearing quartzite and magnetite chlorite schist. The protolith is a set of intermediate-acid marine volcanic-sedimentary rock series, which has experienced high greenschist facies metamorphism and granitization. According to the lithology and stratigraphic correlation, Dongfeng Mountain Group should be located in the upper part of Mashan Group and formed in Late Proterozoic (regional geology of Heilongjiang Province, 1993). In Dongfeng Mountain area, magnetite quartzite is associated with metamorphic volcanic rocks, which reflects that there is ferrosilicon formation in this group (Wang Xichen et al., 2002).
Mashan Group and Dongfengshan Group constitute the metamorphic basement of Jiamusi micro-block. By Mesoproterozoic, the deep-sea volcanic sedimentary rock series of Heilongjiang Group was formed in the rift environment on the edge of craton.
Mashan rock group has undergone multi-stage deformation and metamorphic superposition transformation, and its internal structure is very complex. The schist and gneiss are closely linear and twisted. The supracrustal rocks have obviously undergone recrystallization, among which granitization is the most developed, and it is distributed in the strata in the form of residues. Basement rocks are rich in potassium and aluminum, but lack sodium. Supergene geochemical field shows that iron, gold, copper, chromium, vanadium, titanium and yttrium are highly abnormal. Mineralization is characterized by Precambrian sedimentary metamorphic graphite, phosphorite, sillimanite, iron ore and hydrothermal gold deposits.
(2) Metallogenic sub-series of graphite-phosphorus-sillimanite deposits related to amphibolite facies and granulite facies.
Mashan Rock Group in Jiamusi Micro-land contains many sedimentary metamorphic crystalline graphite deposits in China, which is a dense area of crystalline graphite deposits in China, including super-large deposits such as Yunshan in Luobei, Boli Foling, Liumao in Jixi and Muling Guangyi, and large and super-large deposits such as Yangbi Mountain in Shuangyashan and Yaoyingshan in Hulin (see Table 2- 10). Especially in Linkou, Jixi, Tudingzi, Huangwanggou, Ximashan, Shichang, Heping, Qing Yu, Zhongsanyang, Zhao Long and Guangyi in the south of Jiamusi micro-land, * * * has graphite layer 12, and there are many large, medium and large graphite deposits, with more than 50 occurrences 150.
The whole Mashan Group generally contains graphite, and Mashan Group can be divided into Ximashan Group and Longshan Group (Table 5-7).
Table 5-7 Rock assemblage characteristics of Mashan Group
(According to Geological Bureau of Heilongjiang Province 1980, this article is slightly revised)
Mashan rock group is mainly composed of schist, gneiss and various magnesium marble. The metamorphism of metamorphic rock series is amphibolite facies-granulite facies, in which various remelted granitoids are developed. The main mineral of Mashan Group is graphite, followed by sillimanite, apatite and gold.
In the host rocks of graphite deposits, sillimanite content is very high, and sillimanite deposits can be formed in some areas, such as Sandaogou sillimanite deposit in Ximashan Formation. The deposit occurs in multiple layers, and the ore bodies occur in biotite schist, gneiss and granulite in similar layers. The width of sillimanite mineralization is 100 ~ 2 10m, and the length is over 900m. The occurrence of ore body is consistent with the schistosity of surrounding rock. In graphite-bearing sillimanite schist ore, sillimanite content is 20% ~ 55%, and graphite content is 1% ~ 5%. In biotite sillimanite schist ore, sillimanite content is 15% ~ 35%, and graphite content is less than 0.5%. From the contents of Al2O3 and C in the above two sillimanite ore types, it can be seen that Al and C are positively correlated.
In addition to graphite deposits, there are phosphate deposits in the area, mainly distributed in Jixi, Linkou and Qing Yu, and Liumaoyan Formation of Mashan Rock Group, mainly including small and medium-sized deposits such as Shichang, Qing Yu, Zhongsanyang, Xingkai and Longshan. Ore types include: phosphorite diopside plagioclase gneiss, phosphorite Jinyun marble, phosphorite diopside, phosphorite olivine marble, Jinyun phosphorite diopside and phosphorite diopside potash feldspar. Gangue minerals include plagioclase, graphite, quartz, diopside, phlogopite, calcite, olivine and potash feldspar. The deposit types can be divided into sedimentary metamorphic type and metamorphic hydrothermal type. Ores are generally in the form of scaly granulite structure, equigranular granulite structure and medium-fine granulite structure, and the structure is massive, banded and gneiss. The grade of apatite is 7% ~ 40%, with an average of 15%.
Therefore, this area is actually a composite metallogenic belt composed of graphite, sillimanite and phosphorite, which constitutes a metallogenic sub-series of graphite-sillimanite-phosphorite deposits.
Six-wool graphite ore
Liumao deposit is a super-large deposit in Jixi graphite mining area. The mining area is surrounded by faults, and the ore-forming structures are mainly distributed in east-west direction, and then dismembered into a series of imbricate fault blocks by NNW and NE faults. There are four folds in the deposit, which are roughly parallel from north to south in the axial direction. The regional structure is characterized by east-west folds and thrust faults, and the east-west Longshan syncline runs through the whole area, which controls the distribution of Mashan rock group (ore-bearing rock series). Mashan fault and Shichang fault respectively cross the north and south of this area in the east-west direction. Mashan rock group overthrusts the Jurassic-Cretaceous system, showing the characteristics of fault block uplift basement in the continental margin active zone as a whole. Neoproterozoic basic gabbro moves along the south of the deposit. The faults in the whole mining area are criss-crossing, which destroys the continuity of strata (ore bodies).
Granite develops in Ximashan Formation in the lower part of Mashan Group. Its metamorphic degree generally reaches granulite facies. The common metamorphic minerals are sillimanite, cordierite, almandine, diopside, hypersthene, spinel, olivine, cartilaginous stone and plagioclase. Its original rocks are mainly clayey rocks, semi-clayey rocks, marl and carbonate rocks, mixed with basic volcanic rocks, belonging to shallow marine sediments, and the sediments are characterized by rich iron and magnesium. Ximashan Formation is located at the core of the uplift, with well-developed deep structure. It has been invaded by basic ultrabasic magma for many times, and its metamorphic degree is deeper than Longshan Formation (Longshan Formation is equivalent to amphibolite facies). The rocks of ore-bearing strata include: graphite-bearing sillimanite schist, graphite-bearing biotite plagioclase gneiss, biotite plagioclase granulite, diopside plagioclase granulite and vanadium (calcium) garnet graphite plagioclase gneiss. Due to the late magmatic remelting and ductile shearing, eyeball-shaped or banded granite with garnet as phenocrysts, biotite granite gneiss and garnet-potash feldspar porphyry granite dominated by timely potash feldspar metasomatism appeared in the area.
There are dozens of ore bodies in Liumao mining area, of which Daxigou ore section is the largest. It mainly occurs in the carbonate-rich section in the upper part of Ximashan Formation.
There are 44 large and small ore bodies in Daxigou ore block, of which the main ore body 1 1 is mainly concentrated in the middle section (see Figure 5-28). The thickness of a single ore body is 12 ~ 27m, extending 300 ~ 1500m, and it is layered, wedge-shaped or lenticular. The occurrence of ore bodies is relatively stable, with local expansion and bifurcation, and even pinch-out reappearance. The main ore types are vanadium garnet graphite ore (produced in vanadium garnet diopside schist); Diopside ink ore (produced in graphite-bearing permeability (produced in graphite-bearing marble); Sillimanite graphite ore (occurring in diopside gneiss containing graphite, diopside potassium gneiss containing diopside and graphite plagioclase gneiss). Among them, vanadium garnet graphite ore is rich in grade, containing fixed carbon13% ~16%; Other grades are low (about 3% ~ 8%). The main biogenic minerals are diopside, quartz, feldspar, biotite, garnet, sillimanite, serpentine, rutile and garnet (manganese aluminum garnet and garnet). The ore has scaly granular crystal structure and/or scaly metamorphic structure, as well as flaky, flaky, massive and a small amount of disseminated structure. Graphite is gray-black ~ dark gray, scaly, and the scale diameter is generally 0.063 ~ 0.25 mm Graphite is distributed among gangue mineral particles in scales or flakes, arranged directionally and interspersed locally. In addition, a small amount of graphite has a fine particle size and is embedded in gangue minerals. The ores near metasomatic rocks usually become rich and the scales become rough. Vanadium garnet graphite ore is the main ore type, accounting for about 80% of the whole ore block.
The main mineralization of graphite in this area occurred in Paleoproterozoic, with the characteristics of deposition-regional metamorphism. It belongs to the type of heat flow-high temperature regional metamorphism. Granitization in the late stage of regional metamorphism makes the original rock remelt and transform, and the retrogression of the rock increases the coarsening and local enrichment of graphite scales.
(3) Gold-cobalt deposit metallogenic sub-series related to metamorphic marine volcanic eruption-deposition (Dongfengshan Gold Mine)
The Dongfengshan gold deposit is located in the Dongfeng Mountain Group of Musi Micro-continent in Yoga Yu. According to Liu Jinglan (199 1), the Dongfeng Mountain Group in the mining area can be divided into three rock formations from bottom to top. The lower rock formation consists of lower siliceous layer, manganese-bearing sulfide cobalt-gold layer, iron ore layer and upper siliceous layer with a thickness of 40 ~120m. The lower part of Zhongyan Formation is mainly marble with quartz schist and quartzite, and marble generally contains graphite, while the upper part of Zhongyan Formation is mainly composed of various graphite schists with marble, quartzite and metamorphic intermediate-acid volcanic tuff, with the thickness of 0 ~ 450 m; The upper strata are mainly horny biotite quartz schist, horny granulite with electric biotite, garnet epidote schist and graphite schist, mixed with metamorphic acid tuff lava, with the thickness of 350m m. The common feature of the three rock groups is that they all contain metamorphic intermediate-acid pyroclastic rocks with small thickness.
Figure 5-28 Schematic diagram of ore body distribution in Daxigou ore section of Liumao graphite deposit in Heilongjiang Province
(According to the First Research Institute of Heilongjiang Bureau of Geology and Mineral Resources, slightly abridged)
1- four yuan; 2- Marble or diabase; 3- schist; 4- gneiss; 5-metamorphic rocks; 6- Granitic rocks; 7- graphite ore body; 8— Ximashan Formation
The Rb-Sr isochron age of Dongfeng Mountain Group is 797±43Ma, which may reflect the age of metamorphism. The formation age of Dongfeng Mountain Group is equivalent to that of Longshan Formation of Mashan Group, tentatively scheduled as Proterozoic. The intrusive rocks exposed in the mining area and its periphery account for 50% of the total area. Except Proterozoic granite, the rest are mainly biotite granite from late Paleozoic to Mesozoic and its derived dikes.
The middle and lower rock formations of Dongfeng Mountain Group include carbonate rocks, siliceous rocks, pyroclastic rocks and carbonaceous rocks, and gold is positively correlated with silver, arsenic, antimony, cobalt and nickel. Magnetite quartzite in the lower rock group is associated with metamorphic volcanic rocks, reflecting that there is ferrosilicon formation at the bottom of the rock group.
The gold content of Dongfeng Mountain Group gradually decreases from bottom to top. The lower rock group is the main rock group of gold, cobalt and iron ore bodies, and gold deposits are produced here. Generally, there are gold anomalies in the middle rock formation, but there are almost no gold anomalies in the upper rock formation (Figure 5-29).
Liu Jinglan (1987) investigated the gold content of the iron-bearing buildings in this area 13 (Table 5-8). Dongfengshan gold deposit mainly occurs in the manganese-bearing sulfide cobalt-gold deposit in the lower part of the iron ore layer of the lower rock group. The manganese-containing sulfide layer is located at the bottom of the iron ore layer, which is in the form of thin layer and lenticular interlayer. The main rock types are: magmatic rock, magmatic rock and biotite manganese garnet with magnetic yellow. The rocks are mainly granulite porphyry structure with banded structure. Garnet (mainly garnet) often appears alternately with pyrrhotite and amphibole, forming a banded structure. Granite aggregate usually contains mineral particles such as pyrrhotite, apatite, quartz, natural gold and cobaltate. , forming a structure containing metamorphic crystals. Iron amphibole is mainly manganese iron amphibole, which is closely associated with manganese aluminum garnet. Pyrrhotite aggregates are often distributed in strips, and sometimes filled in the gaps between amphibole and garnet, forming a "meteorite structure"; Sometimes dispersed or banded, contained in garnet crystals. Gold ore bodies can be divided into two types: integrated ore bodies and vein ore bodies, with integrated ore bodies as the main one.
Figure 5-29 Stratigraphic Histogram of Dongfengshan Gold Mine
(According to Liu Jinglan 199 1)
Integrated ore bodies are called integrated gold bodies because of the complete integration of ore bodies and surrounding rocks, and occur in manganese-uranium-gold sulfide deposits. Although the thickness of the ore bed is not large, the horizon and thickness are relatively stable, which is a highly concentrated part of useful elements of cobalt and gold. However, the content of gold in the seam is unstable and varies greatly, and the delineation of ore bodies and surrounding rocks needs to be based on the analysis results. The relationship between the intact ore body and the surrounding rock is gradual, and both the ore body and the surrounding rock have undergone the same deformation, and they fold with the folding of the rock layer. Thickening of ore body in saddle of anticline. Ore bodies are mostly saddle-shaped and lenticular (Figure 5-30). The spatial distribution of gold ore bodies and cobalt ore bodies are basically the same, and sometimes they are integrated, but the distribution range of cobalt ore bodies is larger than that of gold ore bodies. Ore bodies are generally 50 ~ 100 m long, 250m long, 1.73 ~ 4 m thick and 6. 16 ~ 9.0 1 m thick, and the depth of ore bodies is deeper along the dip than along the strike, with the ratio of 1 ~ 3. Ore bodies are often pointed out and reappeared along the strike. On the section, from south to north and from high to low, they are roughly arranged in a wild goose shape on the left.
Table 5-8 Abundance Value of Gold in Iron-bearing Formation of Jiamusi Micro-land Block (w(Au)/ 10-6)
(According to Liu Jinglan 1987)
Vein ore bodies often occur in the upper siliceous layer and are scattered, mainly controlled by the NE-trending fault structure along the bedding, with limited scale.
The ores in this area can be divided into four natural types: banded-micro-disseminated sulfur-poor cobalt gold ore, banded-veinlet disseminated cobalt gold ore, gold-bearing quartz vein type ore and banded lepidolite cobalt gold ore. The main ore types are 1 and 2. The main metal minerals in the ore are pyrrhotite and arsenopyrite, followed by cobalt ore, nickel-nickel ore, nickel-arsenic ore, magnetite and natural gold. Pyrite is found in gold-bearing quartz vein-type ores, and non-metallic minerals include manganese aluminum garnet, manganese iron amphibole, yingshi and biotite. In the banded iron-amphibole-olivine-pyroxene cobalt-gold ore, the main minerals are Yule pyroxene, fayalite and amphibole.
Figure 5-30 Geological Profile of Dongfengshan Gold Deposit
(According to Liu Jinglan 1987)
1- gold deposit; 2- cobalt deposit; 3- Iron ore deposit; 4- microcrystalline mica quartz schist containing tourmaline; 5- Fine-grained marble; 6- cordierite schist containing microcrystalline graphite; 7- biotite granite; 8- dike rock
Most natural gold is irregular and granular. Some are round, long, disc-shaped and so on. The particle size is fine, mostly about 5 μ m. Natural gold is closely related to arsenopyrite, cobalt ore, manganese aluminum garnet and manganese iron amphibole. The purity of natural gold ranges from 843 to 990, and the arithmetic average is 9 18.
Dongfengshan gold mine has experienced regional metamorphism dominated by amphibolite facies, with metamorphic temperature of 455 ~ 600℃ and pressure of 0.3 ~ 0.5 GPA.
Dongfengshan banded iron formation gold deposit belongs to volcanic jet deposition-metamorphism. The original sedimentary environment of the deposit is a sea basin far from the eruption center of intermediate-acid volcano, and the ore-forming materials are brought from the deep part of the volcano to the seawater on the crust surface. Gold is mainly concentrated in sulfide phase (or mixed phase with carbonate phase) at the bottom of banded iron formation in finely dispersed state, and forms layered, layered and lenticular integrated contemporaneous ore bodies with regional metamorphism. With the structural deformation of regional metamorphism, the gold ore body is repositioned, forming saddle-shaped and partially lenticular ore bodies. After regional metamorphism, metamorphic hydrothermal activity activated a small amount of gold, forming vein ore bodies.
It can be seen that Jiamusi micro-block was an important metallogenic period of graphite-phosphorus-gold deposit in Proterozoic. Graphite-sillimanite-phosphate deposit metallogenic sub-series is formed in Jixi area, and gold-cobalt deposit metallogenic sub-series is formed in Dongfeng Mountain area.