1. Content Overview
Black Rock Series, also known as Black Shales, contains more organic carbon (C organic ≥ 1%) and A general term for a combination of dark gray to black sulfide (iron sulfide) siliceous rocks, carbonate rocks, argillaceous rocks and corresponding metamorphic rocks. In 1989, the International Geological Comparison Program 254 Project "Metallic Black Shale and Related Mineral Deposits" defined "black shale" as "a black or gray fine-grained (silt sand or finer) sedimentary rock, usually muddy, containing Quite high organic matter (C organic ≥ 0.5%).” Tu Guangchi (1999) defined black shale deposits as layer-bound deposits occurring in epimetamorphic clastic rock series with high organic carbon content (generally content >0.5%). Clastic rock systems often contain carbonate rocks, siliceous rocks and volcanic rocks, but are mainly sandstone and slate. This definition more comprehensively reflects the basic characteristics of black rock series deposits. Sozinov (1990) divided black rock series (black shale) into four types based on rock type and material composition: terrigenous black shale formation, siliceous black shale formation, carbonate black shale formation and volcanic origin (carbon salt) black shale construction. Black rock series usually contains abundant metal elements such as PGE, Cu, Ni, Mo, Au, U, V, Mn, Fe, Co, Bi, Cr, Se, etc. These elements can form certain-scale deposits under appropriate conditions.
In recent years, foreign research on mineral deposits related to black rock series has made important progress. The black rock series is closely related to mineralization. The black rock series not only contains minerals itself, but also serves as a source layer to provide minerals for the formation of epigenetic mineral deposits, such as the Muruntau gold mine, the Kumtor gold mine, and the Polish copper-bearing shale type. Cu-Ag deposit, Columbia emerald deposit (Cheilletz et al., 2001), Guangxi Dachang tin polymetallic deposit (Pa?ava et al., 2003). The black rock series changes the properties of the ore-forming fluids, leading to the precipitation of metallic minerals. For example, the copper-rich and silver-rich ores in the Kuperschier copper deposit in Poland may be caused by the biological interaction between the copper-containing solution in the underlying Rotliegendes layer and the Kuperschifer black shale layer. The H2S generated by sulfate reduction reacts, leading to massive copper precipitation and mineralization (Michalik et al., 2001; Blundell et al., 2001). Pa?ava et al. (2003) believed that the black rock series played an important role in the precipitation of tin in the Dachang tin polymetallic deposit in Guangxi.
The black shale system also has an important impact on post-generated mineralization. For example, the Cretaceous black shale of the Colombian emerald deposit is considered to be the ore-bearing mineral, and undergoes water-rock reaction with the basin brine, resulting from sodium metasomatism. and cation exchange leading to mineralization, with beryllium originating mainly from clay rocks (Cheilletz et al., 2001). A systematic study of the Devonian shale and ore-forming fluids that host the Dachang tin polymetallic deposit in Guangxi not only proves that the layered and vein-like tin polymetallic deposits in the area are both mineralization systems related to granite It is also found that a large amount of organic matter exists in the ore-forming fluids in the form of CO2, CH4, etc., and these organic matters are believed to originate from the surrounding rocks (Pa?ava et al., 2001). Germanium is a sparse element, but it is widely present and enriched in many coal seams dominated by black shale. In southwestern my country and the Far East of Russia, germanium was found to be highly enriched in coal and became independent deposits, even reaching super large scales (Seredin et al., 2001). Although the origin of germanium is still debated between syngenetic and epigenetic issues, the richness of germanium in coal still reflects the important control effect of organic matter on germanium mineralization. Since the black rock series is the product of a strong reducing environment, a large number of rare minerals and their combinations are found in many mining areas (Distler et al., 2001), including a variety of elemental metals, metal alloys or intercompounds, sulfate minerals, and phosphates. species, tungstates, tellurides, Pt-Cu-Fe metal solid solutions, as well as arsenic platinum ore, sulfur platinum ore, Sn-Sb solid solution, Ni-Sb solid solution and a large number of Fe-Ni-S and Cu-S mineral series.
2. Application scope and application examples
Research examples
Figure 1 Bakyrchik gold deposit model in Kazakhstan
(According to Daukeev et al., 2004)
The Bakyrchik gold deposit is structurally located from northwest to west on the southwest edge of the Kuzlov Depression in the Variscan fold belt of Zhaisan-Junggar. The intersection of the Kalba fault and the nearly east-west trending Kuzlov fault (Fig. 1). The exposed strata are mainly composed of extremely thick flysch-like rocks from the Carboniferous Period. The proven reserves of the deposit are 277t. The organic matter content of the ore-bearing rock series is high, ranging from 0.2% to 1.5% to 2.0%. The average grade of gold is 9.4×10-6. The ore is accompanied by silver, lead, tungsten, aluminum, antimony, elements such as arsenic (Daukeev et al., 2004). Late Carboniferous-Early Permian granodiorite and plagioclase granite strains are developed in the mining area. Geophysical data show that there are huge hidden rock masses 2 to 5km deep in the mining area. Ore bodies are produced in the form of strips, layers and lenses. The intersection of the West Kalba northwest-trending fault and the nearly east-west trending Kuzlov fault on the southwest edge of the Kuzlov sag controls the distribution of gold mineral belts. Shear zones, faults and their intersections control the distribution of mineral deposits. The faults control the depth of mineralization. 1～1.5km. The mineralization types are gold-bearing quartz vein type, pyrite aplite type and disseminated sulfide carbonaceous type. The main alterations of the surrounding rocks include silicification, sericitization, chlorite, pyrite, ankerodolomitization, carbonation and weak graphitization. Isotope geochemistry shows that the temperature during the sedimentary diagenetic period is 60 to 140°C, and the ore-forming fluid mainly comes from seawater. The δ13C value of sulfur isotope in the ore-bearing rock series is mainly between -14‰ and +31‰, which is of biological origin; the main mineralization period The temperature is 250~350℃. The ore-forming fluid mainly comes from metamorphic fluid. The δ13C value in graphite is between -22‰~+26.8‰, and the δ13C value in carbonate is between -2.5‰~+18‰, which is of metamorphic origin. Characteristics: From the surface (0.5km) to the depth (1.5km), the δ13S value gradually increases, indicating that the sulfur is mainly a mixture of deep sulfur and biological sulfur. The formation of gold deposits has gone through a sedimentary-diagenetic period, a tectonic-metamorphic hydrothermal period (main mineralization period), and a magmatic hydrothermal superimposed transformation period.
In short, this deposit has the following characteristics: ① The deposit is controlled by the interaction of ductile shear zones and fractures; ② The host rock series contains high contemporaneous gold, organic carbon and globular and strawberry-shaped Pyrite has a high organic carbon content; ③ Magmatic hydrothermal activity is related to the superimposed enrichment of gold mineralization; ④ The mineralization types are gold-bearing quartz vein type, pyrite aplite type and disseminated sulfide carbonaceous type, among which Disseminated sulfide carbonaceous type is the most important type of mineralization; ⑤ The main changes in surrounding rock include silicification, sericitization, chlorite, pyrite, ankerodolomitization, carbonation and weak graphitization, etc. ;⑥Characteristic As-Sb-Mo-W-Sn-Pb-Au geochemical signature.
3. Data sources
Mao Jingwen. 2001. Trends in research on mineral deposits related to black shale systems. Mineral Deposit Geology, 20 (4): 402～403
< p>Mao Jingwen, Zhang Zuoheng, Wang Yitian, et al. 2012. Main foreign mineral deposit types, characteristics and prospecting exploration. Beijing: Geological Press, 371～380Wang Denghong. 1997. Research progress on mineral deposits related to black rock series . Geology and Geochemistry, 2: 85～88
Graupner T, Kempe U, Spooner E T C et al. 2001. Microthermometric?Laser?Raman spectroscopic, and volatile?ion chromate?graphic analysis of hydrothermal fluids in the Paleozoic Muruntau Au?bearing quartz vein ore field, UzbekistanUI. Economic Geology, 96: 1～23
Mihalik M, Sawlowicz Z. 2001. Multistage and long term origin of the Kupferschirfer copper deposits in Poland. In: Piestrzynski A. (ed). Mineral deposits at the beginning of the centory. Liss/Abingdon/Exton/Tokyo: A.A. Balkema Publishers, 235～238
Pasava J, Barnes S J, Vymazalov A.2003 .The use of mantle normalization and metal ratios in the identification of the sources of platinum?group elements in various metal?rich black Shales. Mineralium Deposita, 38: 775～783
Pasava J, Kríbek B, Vymazalov A et al.2008.Multiple sources of metals of mineralization in Lower Cambrian black shales of South China: evidence from geochemical and petrographicstudy.Resource Geology, 58: 25～42
Wille M, Nagler T F, Lehmann B et al.2008. Hydrogen sulphide release to surface waters at the Precambrian /Cambrian boundary. Nature, 453: 767～769