Relationship between Precambrian landmass formation and mineralization in China and its adjacent areas

7. 1.2. 1 CAMBRIAN block reconstruction

Although the lithosphere of the craton is stable, these Precambrian landmasses in China and its adjacent areas are not static after their formation, but are constantly being transformed with the geological evolution. Take North China as an example for analysis.

According to the geological and geophysical characteristics of North China, the lithosphere is discontinuous and can be divided into Ordos craton type, Yanshan-Taihang orogenic belt type and North China plain rift type (Qiu et al., 2004, 2006).

Geologically, the North China landmass has the same history as the global main landmass (craton) and was formed in Archean-Proterozoic. The igneous magma activity before Jurassic was limited to the edge of the block (Figure 7.5), indicating that the North China block was a stable block (China-Korea block) before Jurassic. Since Jurassic, the land mass has undergone a strong transformation, that is, the land mass has been "activated": in terms of magmatism, Yanshanian magmatism went deep into the land mass and spread all over the central and eastern parts of North China (Figure 7.6); Cenozoic is superimposed by rifting, and a large number of basalt eruptions are mainly distributed in the eastern part of North China Plain (Figure 7.7).

Fig. 7.5 Distribution map of Caledonian, Variscan and Indosinian intrusive rocks in North China Block (modified according to Cheng 1994).

Fig. 7.6 Distribution map of Yanshanian intrusive rocks in North China landmass (according to the history, 1994).

Fig. 7.7 Distribution Map of Cenozoic Basalt in Eastern Plain of North China

The composition and structure of the three types of lithosphere formed by the evolution of the lithosphere in North China have changed significantly: Ordos is a craton lithosphere that survived the "activation" and "transformation" of Mesozoic and Cenozoic landmasses, the main component of the continental crust is TTG, and the lithospheric mantle is mainly composed of gabbro with strong losses, which has been preserved since the final formation of Neoarchean-Paleoproterozoic, and its crust-mantle petrological structure can be used as North China and even China. In Mesozoic, the central and eastern part of North China block was "activated" in Yanshan orogeny, and a large amount of convective mantle materials and heat input transformed the original TTG continental crust into granite continental crust, and the lithospheric mantle was replaced by fanghui peridotite-lherzolite formed in Yanshan period. Yanshan-Taihang Mountain is a residual orogenic stone circle after Cenozoic rifting in eastern North China. Due to the thinning of Cenozoic extension, the current thickness cannot represent the thickness of the crust and lithospheric mantle during the Yanshan movement, but the material and structure of the lithospheric mantle and continental crust were still formed during the Yanshan movement. During the Cenozoic era, continental rifting in eastern North China formed a rift lithosphere represented by the eastern plain of North China. With the eruption of a large number of basalts in the rift valley, the "acidic" continental crust in Yanshan period was "alkalized" again, and the lithospheric mantle formed in Yanshan period was destroyed, forming the Himalayan lithospheric mantle with lherzolite as the main body. Rift crust and lithospheric mantle experienced stretching thinning and thermal erosion on the lithospheric scale. The materials and structures of lithospheric mantle and continental crust detected by geophysics today were formed in Cenozoic.

To sum up, the tectonic units in North China can be understood as: before Jurassic, they belonged to the Sino-Korean landmass, and after Jurassic-Cretaceous Yanshan movement, they were divided into two units: the western landmass (craton) and the central-eastern orogenic belt; With the development of Cenozoic rifting, it is further divided into western craton, central orogenic belt and eastern rift. Therefore, to discuss the relationship between the formation and mineralization of Precambrian landmasses in China and its adjacent areas, we should pay attention to the mineralization related to the formation and transformation of landmasses.

7. 1.2.2 Mineral characteristics of Precambrian landmasses

Precambrian deposits in China are mainly distributed in landmasses, especially in North China landmass and Yangtze landmass, and less in orogenic belts (Shen Baofeng et al., 2004, 2006). Rifts in continental margin and continental block are very favorable spaces for Precambrian deposition. They pointed out that China is rich in Precambrian mineral resources, and many large and super-large deposits such as iron, copper, lead, zinc, nickel, gold, rare earth, manganese, graphite, magnesite, talc, boron, phosphorus, pyrite, rutile and vermiculite have been formed. The metallogenic age is from ancient times to Sinian, but the peak of mineralization is in three geological periods: Neoarchean, Paleoproterozoic, Mesoproterozoic-Qingbaikou. With the evolution of Precambrian geological history in China, the ore-forming materials and deposit types have obviously changed and increased. In the global metallogenic domain and metallogenic belt classified by Mei et al. (2004), the Sino-Korean metallogenic belt is located in the southeast of Lauya metallogenic domain, bordering on Urals-Mongolia metallogenic belt, Himalayan metallogenic belt and Indo-China Peninsula metallogenic belt in the north, west and southwest respectively, and adjacent to East Asia metallogenic belt in the east. Its distribution range is equivalent to China block, including several ancient landmasses in central China and Korean Peninsula. The main minerals in this metallogenic area are coal, iron and phosphorus, followed by tungsten, molybdenum, lead and zinc, copper, nickel and gold. The representative deposits are Dongsheng-Shenfu coalfield in China, Kunyang sedimentary phosphorite, Anshan-Benxi BIF iron mine, Jinchuan copper-nickel sulfide deposit, Jinduicheng porphyry molybdenum deposit, Luanchuan skarn type tungsten-molybdenum deposit and so on. The famous Jiande metamorphic deposit is produced in North Korea.

Precambrian iron ore occupies an important position in China, and the iron ore resources/reserves in this period accounted for 65.6% of the whole country (Shen Baofeng et al., 2005). Precambrian iron deposits in China are mainly distributed in the eastern part of China, the continental block and the rift valley inside the continental block, and their metallogenic scale, metallogenic region, metallogenic types and metallogenic evolution characteristics are obvious. It can be divided into five types: (volcanic) sedimentary metamorphic iron deposits, iron deposits related to volcanic intrusion, sedimentary iron deposits, composite mineralized iron deposits and magmatic iron deposits. The oldest iron ore deposit in China was formed in Archaean, and NeoArchean was the most important formation period of iron ore in China. The iron ore reserves formed in this period account for about 50% of the total iron ore reserves in China, and the deposit type is banded iron ore deposits related to greenstone belts. The evolution characteristics of this kind of deposits are: the metallogenic scale changes from weak to strong and then weak, and the types of deposits change from simple to complex and then simple.

Siberian continental block

Siberian landmass is located in the northeast of Lauya metallogenic domain (Mei et al., 2009), bordering on Urals-Mongolia metallogenic belt in the west and south, and adjacent to Chukchi-Okhotsk metallogenic belt in the east. Its distribution range includes the Central Siberian Plateau and Termel Peninsula, and it belongs to the Siberian landmass in geotectonics. The main minerals in this area are coal, gold and diamonds, followed by copper, antimony, lead, zinc, nickel, manganese and potassium salt. Representative deposits include Russian Tunguska coalfield, Su Huoyi Locke black rock series type gold deposit, Heping Kimberlite type diamond deposit, Norilsk copper-nickel sulfide deposit, Nepa evaporite type potassium deposit, Salik hydrothermal antimony deposit, etc.

The most important Precambrian iron deposit (V.I.Kazanskyra, 1980) in Ardan Shield is iron-bearing quartzite in Chara-Tokko area, which occurs in the north-south trending trough volcanic-sedimentary rock series. Reliable geological data of Ardan Shield in Australia, India, South Africa (azania) and Canadian Archean landmass (Craton) reveal the similarity of early Precambrian structural complexes and their development time, which can be distinguished according to the differences in main components, metamorphic degree, metasomatic metamorphism and ore-bearing formations.

7. 1.2.2.2 Chinese mainland

The North China Craton has a long history of 3.8Ga, especially compared with other landmasses, it has a more complicated multi-stage tectonic evolution history, which records almost all the early crustal development and major tectonic events since Mesozoic (Zhai, 20 10). Archean, North China landmass experienced the formation of >: 3.0Ga continental core and micro-landmass; 2.7~2.9Ga continental crust proliferation; Magma, metamorphism and cratonization of 2.5Ga; 2.3~ 1.9Ga Proterozoic active (orogenic) belt; 1.8Ga basement uplift and rift-non-orogenic magmatic events. From Neoproterozoic to Paleozoic, the North China block was in a relatively stable state, and its southern and northern edges were influenced by the Qinling orogenic belt and the ancient Asian oceanic orogenic belt. In Mesozoic, the North China landmass experienced the intense transformation of Mesozoic tectonic framework and the destruction and reconstruction of craton. In Cenozoic, the eastern margin of North China landmass belongs to a part of the Pacific Rim tectonic belt. Corresponding to the above-mentioned major tectonic events, large-scale mineralization occurred in the North China block, forming rich and diverse solid mineral resources. The formation and evolution of North China landmass and its different types of metallogenic systems provide an example for further understanding of the constraints of tectonic environment on mineralization. Gold deposits in granite-greenstone belt (Shen Baofeng et al., 1994) are widely developed in North China landmass, mainly distributed in Xiaoqinling, Jiaodong, Jiapigou, western Liaoning, northern Hebei, Wulashan and Wutaishan, among which there are not only many small and medium-sized deposits, but also large and super-large gold deposits, which are the main gold production bases in China at present.

From the perspective of geological evolution, before 2900Ma, due to the separation of mantle and the migration of materials to the ground, the original silicon-aluminum crust was formed in the North China block. With the formation of the initial silicon-aluminum layer, the land and sea gradually differentiated, forming ancient uplift and ancient basin. Around 2900Ma, the first strong tectonic-magmatic thermal event occurred in the North China block, which formed the early continental core and the first stable period. From about 2800Ma, a rift environment similar to the modern continental margin active zone or back-arc basin was formed at the edge of the oval dome composed of ancient continental cores, and a large number of volcanic eruptions and deposits, that is, a large number of volcanic-sedimentary materials, namely greenstone formations, gathered in the narrow trough basin. Intense submarine volcanic activity has brought a large number of useful metals such as gold, iron, copper and zinc from the mantle, and a large amount of gold and mafic volcanic rocks have been sprayed from the depths of the mantle to the seabed, becoming the source bed of vein-like and stratabound gold deposits. Strong submarine volcanic activity has brought abundant iron from the deep, and the formation of some major iron mines in North China block, such as Waitoushan, Gongchangling, Banshigou and Laoniugou, is related to this. In the later stage of volcanic activity, it turned into a widely distributed andesite-felsic volcanic eruption. At the same time, with the volcanic eruption, ore-bearing fluids such as copper and zinc rose along the crater and sprayed to the seabed, forming primitive massive sulfide deposits. Around 2500Ma, the second strong tectonic-magmatic thermal event occurred, and the Archean block was basically cratonization. During this period, due to the intrusion of granite slurry as a heat source, some metals in the original greenstone formation were recrystallized, activated and migrated. During this period, the original massive sulfide deposit experienced multi-stage structural deformation, which repositioned and enriched metals and formed ore-rich pillars. Iron deposits are coarsened due to metamorphism and transformation, and there are stratabound gold deposits and some vein gold and iron deposits controlled by ductile shear zones. After the formation of the granite-greenstone block, it underwent the transformation of multi-stage tectonic-magmatic events, such as Lvliang Movement, Variscan Movement and Yanshan Movement, especially the Yanshan Movement, as the last and strongest tectonic-magmatic event (Qiu et al., 2006), which played a very important role in the formation and final positioning of gold deposits in the North China block.

The Yangtze Plate evolved on the basis of the Paleoproterozoic-Neoarchean continental core (Hua Youren, 1995). Before the Lvliang Movement, several small ancient plots, mainly small and medium-sized plots in Sichuan, formed a yoke block belt protruding to the northwest. In Mesoproterozoic, a trench island arc system was formed on the east and west sides of the yoke block belt, and a set of pre-arc and post-arc sedimentary formations were deposited. The Dongchuan movement during the period of 1~ 1. 1Ga consolidated the fold of the gully-arc system into a land mass. Continental rifting occurred in the early Neoproterozoic, forming a set of rift sedimentary formations; Jinning movement consolidated the Yangtze plate as a whole, and in the late Neoproterozoic, the piedmont molasses formation, ice sheet and carbonate cap rock developed.

Hua Youren (1995) believes that the five main stages of the development of the Yangtze plate structure correspond to five important metallogenic periods, namely, the Mesoproterozoic Dongchuangou arc system metallogenic period, the early Neoproterozoic Jinning continental rift metallogenic period, the late Neoproterozoic Chengjiang-Caledonian landmass metallogenic period, the late Paleozoic Hercynian-Indosinian continental rift metallogenic period and the Mesozoic Yanshan active continental margin metallogenic period. For example, Dahongshan iron and copper deposit related to submarine volcanism in Dongchuan period, Yunnan-style sedimentary reformed iron deposit related to clastic carbonate formation, copper deposit deposited by submarine volcanic hot water in Jinning period, stratabound copper deposit formed by mineralization in Chengjiang-Caledonian period, etc.

Precambrian lead-zinc deposits are mainly formed in different geological structural units and rift system margins in the Mesoproterozoic and Neoproterozoic, and their distribution is controlled by structures. They are mainly distributed in the Proterozoic rift system in the east, middle and west of the northern margin of North China block and the marginal active zone on the east side of the Sinian rift belt of Kangdian axis in the west of Yangtze block, mainly in the northern margin of North China block. Mineralization is generally controlled by volcano-sedimentation-metamorphism, which is stratabound. The ore-forming age tends to change from north to south (Cao et al., 2005). At present, there are 5 1 pre-CAMBRIAN lead-zinc deposits with proven reserves, including super-large deposits 1, 3 super-large deposits, 7 large deposits, medium-sized deposits 12, and the rest are small. In recent years, the discovery of new types of lead-zinc deposits around the Yangtze block has aroused widespread concern.

7. 1.2.2.3 Mainland India

India's mineral resources are mainly distributed in the Indian Peninsula shield area, and its formation is related to Precambrian mineralization, with abundant iron, manganese and bauxite resources. Mineralization includes: ① gold mineralization in Archean greenstone belt related to craton (typical representative: craton gold deposit with a reserve of 825 t); Rare metal deposits such as rare earth, niobium and tantalum related to continental alkaline magmatism (including carbonate rocks); Diamond deposits in kimberlite cones. A large number of ultracrustal rocks and manganese-rich rocks are distributed in the Indian Craton. Ultrabasic rocks in Archean complex are rich in nickel metal, which provides a material basis for the formation of lateritic nickel deposits. Chromium, nickel (copper) deposits related to basic magmatic activities. ② Sedimentary mineralization related to rifting, such as Gondwana and Paleogene 1 1 coal-bearing basins. (3) The Proterozoic active belt and its tectonic action in the Indian landmass related to orogenic belts control the important non-ferrous metal metallogenic belt and metal mineralization in India, such as the Singebum shear belt controls the Singebum copper mineralization belt, and the Appalli ridge landmass active belt controls the most important copper mineralization belt in India; The high Himalayan orogenic belt on the Indian side has only a small amount of mineralization. In addition, climate plays an important role in hematite deposits, bauxite deposits, Bagarat residual manganese deposits and laterite nickel deposits in India.

Arabian continent

The Africa-Arabia metallogenic belt is located in the middle of Gondwana metallogenic belt (Mei et al., 2009), facing South America metallogenic belt, Antarctic metallogenic belt and Australia metallogenic belt respectively in the west, south and east, and connected with Mediterranean metallogenic belt and West Asia metallogenic belt in the north. Its distribution scope is basically consistent with the Africa-Arabia block, including the African continent and the Arabian Peninsula except the Atlas Mountains. The main minerals in this metallogenic area are oil, natural gas, diamond, copper, aluminum, nickel, chromium, lead, zinc, gold, phosphorus, manganese and uranium, followed by iron, tin, antimony and potassium salt. The representative deposits are Gavar oil and gas field in Saudi Arabia, Bulgain oil and gas field in Kuwait, Boke and Tugai-Dabo laterite bauxite in Guinea, Kimberly diamond deposit in South Africa and Bushveld layered composite chromium-nickel deposit.