According to the classification of petrology, granite in a narrow sense refers to acidic intrusive rocks formed by magmatic intrusion, and the main minerals are Synchrosite (with a content of 20% ~ 60%), alkali feldspar and plagioclase. Granite in a broad sense refers to a set of intermediate-acid plutonic or hypabyssal intrusive rocks with the appearance of granite.
Granite is a widely distributed rock, which has been produced in various geological ages. Most of the forms are bedrock, rock plants and so on. In terms of genesis, some people think that granite is the result of condensation crystallization of granite slurry in the deep crust or crystallization differentiation of basaltic magma, while others think that granite is the result of deep metamorphism and metasomatism.
Second, the petrological characteristics of minerals
The content of silicon dioxide is more than 70%. The color is lighter, and grayish white and flesh red are more common. It is mainly composed of dark minerals such as quartz and feldspar and a small amount of biotite. The timely content is 20% ~ 60%. Feldspar is divided into alkali feldspar and plagioclase, and alkali feldspar is more than plagioclase, accounting for more than 2/3 of the total length stone. Alkali feldspar is a variety of potash feldspar and albite, and plagioclase is mainly albite or albite. The dark mineral is mainly biotite with a small amount of amphibole. Having granite structure or porphyritic structure. Block structure is the most common, but there are also variegated structure, crystal cave structure and gneiss structure.
Granite has high wear resistance and mechanical strength. The compressive strength of fresh granite is generally (1000 ~ 2100) ×105 pa, and the highest is 3000 × 105 Pa. The flexural strength is generally (90 ~ 270) × 105 Pa, the density is 2.63 ~ 2.75 g/cm3, the bulk density is 2.50 ~ 3.3 g/cm3, the porosity is about 1.2%, and the water absorption is about 0.46%.
Third, use.
Granite is often closely related to the genesis of endogenetic metal deposits such as nonferrous metals, rare metals and radioactive elements. There are many kinds of sediments, which are an important building material. They have excellent physical properties and decorative effects, such as high strength, high hardness, wear resistance and corrosion resistance, which bring great economic value, and their application has been paid more and more attention. Granite is increasingly used in stone materials, not only for luxurious public buildings, but also for home decoration.
As a kind of stone, granite is mainly used in the following aspects: building materials, artistic decoration, carving materials, paving materials, water conservancy projects, bridge projects, port dams, foundation and other engineering materials, chemical and light industrial products, measuring instruments and components in astronomy, earthquake and aviation industries, and is also widely used in household appliances and environmental protection.
Four. geologic feature
The types of granite deposits in China are complex and diverse. The proven and developed granite deposits can generally be divided into magmatic granite deposits and metamorphic granite deposits, which provide a broad prospecting prospect for granite deposits in China.
(1) magmatic granite deposit
It is formed by the intrusion of high-temperature magma into different parts of the earth's crust through condensation and crystallization, which has a sudden intrusion relationship with surrounding rocks and has typical structural characteristics of high-temperature melting and condensation.
These deposits include a series of ultrabasic rocks, basic rocks, intermediate rock, acid intrusive rocks and volcanic rocks, which are distributed in all major geological structural units in China, mainly in the fold zone. The formation time can be divided into Precambrian, Caledonian, Hercynian, Indosinian, Yanshan and Himalayan periods. Representative deposits are Shouning granite mining area in Fujian, Precambrian hornblende lherzolite in Miyun, Beijing, Jinyun tuff in Zhejiang, fuchsia tuff lava in Minhou, Fujian and fuchsia banded rhyolite in Yongtai, Fujian.
(2) Metamorphic granite deposits
Metamorphic or metasomatic granite deposits are granite deposits occurring in deep metamorphic rock series. Granite ore body is a deep metamorphic rock formed by strong metasomatism of original rock and gradual transformation of rock composition, structure and structure under regional metamorphism. Among them, migmatite, gneiss and migmatized granite can be used as granite. Metamorphic granite deposits are mostly distributed in North China platform, and the metallogenic age is mainly Archean. The ore-bearing rock series include Fuping Group in Taihang Mountain, Taishan Group in western Shandong, Dengfeng Group in Songshan Mountain, Sanggan Group in Yanshan Mountain and Anshan Group in Liaodong. The ore body has a large exposed area and is distributed in a strip shape. The lithology is mostly acidic or alkaline migmatization or potash granite series, with common gneiss structure, red rock, uniform structure or beautiful pattern, which can meet the requirements of famous stone materials. The representative deposits are Archean migmatized gneiss granite deposit in Lingqiu, Shanxi Province and Archean migmatized granite deposit in Yanshi, Henan Province.
Verb (abbreviation of verb) mineral distribution
Granite is widely distributed in China. Due to the complex geological conditions, many tectonic movements and frequent magmatic activities in China, all major tectonic magmatic periods from Proterozoic to Neogene occurred. In geological history, the back-arc magmatic belt formed on the mainland side of the convergence boundary between the continental plate and the oceanic plate often develops along the extensional deep faults of the orogenic belt. The formation of Chinese mainland's crust has gone through a long historical process, with eleven ancient plates as the core, constantly assembling and splicing, and the mainland gradually proliferated and expanded. In this process, the granite magma mainly developed in the folded orogenic belt on the upper wall of the plate subduction zone, controlled by deep faults, and distributed in strips, often occurring in large bedrock and rock plants, forming the main body of large mountain systems, usually distributed in the folded belt and tectonic active area. Generally speaking, the Variscan and Yanshan periods were the periods of intense activity of granite magma in China. Granites in northern China are mainly Yanshanian, Caledonian and Variscan, while those in southern China are mainly Yanshanian.
Large areas of granite are exposed in Zhejiang, Fujian, Jiangxi, Guangdong, Yanshan in the north and Tianshan in the northwest of China. They are hundreds of kilometers long and tens of kilometers wide, and their output is closely related to orogeny and many metal deposits.
The available resources of intransitive verbs
Granite is widely distributed in China and occurs in all major tectonic magmatic periods from Proterozoic to Neogene. It is mainly distributed at the edge and inside of ancient plates, and widely distributed in northeast China, Inner Mongolia, Xinjiang, Qilian Mountains, Qinling Mountains, northeastern Tibet-western Yunnan and the eastern coast of South China, with granite in South China being the most typical.
Granite mineral resources are abundant, distributed all over the country, especially in the southeast, and various granite bodies are exposed in a large area, which shows its large reserves. According to the National Bulletin of Mineral Resources Reserves issued by the Ministry of Land and Resources in 2005, there are more than 2 14 mining areas with proven reserves, and about 20× 108t of mineral resources have been discovered. Shandong, Guangxi and Beijing are the main regions, accounting for 20.7%, 12.2% and 1655 respectively.
Table 2-34- 1 Find out the granite resource reserves in China.
(According to Notice of Ministry of Land and Resources on National Mineral Resources Reserves, 2005)