What Is Granite Cladding?

Granite is an intrusive rock in acidic (SiO2> 66%) magmatic rocks. This is the most common type of rock in this category. It is mostly light flesh red, light gray, and off-white. Medium coarse grain, fine grain structure, block structure. Some are spotted structures, spherical structures, gneiss-like structures, and so on. The main minerals are quartz, potash feldspar and acid plagioclase, and the minor minerals are biotite, hornblende, and sometimes a small amount of pyroxene. There are many types of auxiliary minerals, such as magnetite, vermiculite, zircon, apatite, tourmaline, and fluorite. Quartz content is the largest among various magmatic rocks, and its content can range from 20-50%, and a few can reach 50-60%. The content of potassium feldspar is generally more than that of plagioclase. The relationship between the content of the two is often that potassium feldspar accounts for two thirds of the total feldspar, plagioclase occupies one third, and potassium feldspar is more in granite. It is light flesh red, and there are also gray and gray. Off-white potassium feldspar and plagioclase are often difficult to distinguish in hand specimens. At this time, we must carefully observe the dual crystal characteristics of these two types of feldspar, because plagioclase has a polycrystalline twin crystal. When rotating the hand specimen, we can see regular bright and dark polyliths on the plagioclase crystal, and potassium feldspar. It is a card-type twin crystal, which appears as two halves with different brightness.

Originally by H. H. Read's famous saying of there are various granites in 1933. In fact, there are at least 20 granite classification schemes (see Barbarin, 1990, 1999 summary; and Frost et al. 2001 for more commonly used Comments on classification methods). The most common classification schemes are geochemical and / or genetic letter classification schemes, such as dividing granite into S type, I type, M type, A

As the landmark rock of the continent, granite forms the basis of the upper crust of the continent, and the formation process of granite is usually closely related to the tectonic, metamorphic, and mineralizing processes of the continent. Since the 18th century when geological science was still in its cradle stage, the genesis of granite has been the subject of much debate. Controversy about the genesis of granite can be seen in the works of Gilluly (1948), Pitcher (1993), and Young (2003), which are not listed here. It should be mentioned that since the introduction of plate tectonic theory in the 1960s, many explanations of the genesis of granite have been placed in the theoretical framework of the plate to re-understand. In many cases, awareness seems to be converging, but actual debate continues.

Bowen (1914, 1922, 1948) misunderstood the basaltic magma crystal differentiation theory by combining the mineral crystallization sequence with the magmatic rock from basic to acidic rock sequences. The experimental results prove that the crystalline differentiation of basalt magma can only produce a small amount of residual granitic melt, which obviously conflicts with the fact that there are many granites in the field (Holmes, 1926; Read, 1957). The mineral reaction series can actually be applied to magma systems with different components. In other words, the first crystals from the magma system are not necessarily basic rocks, and the final formation may not be felsic (acid) rocks, because the nature of the rocks crystallized from the melt depends on the composition of the melt. Not the order of mineral crystallization (Kennedy, 1933). Walton (1960) commented on Bowen's knowledge as follows: "There is nothing wrong with Bowen's chemical theory or its application to the separation of basaltic magma. This is still a basic principle of petrology. But Ignition theory rigidly constrains a single model, thinking that most igneous rocks evolved due to basalt magma intrusion into the crust to cool, crystallize, and separate, so it is a bit speculative. The same chemical theory can be applied to other models

In the 1940s (Gilluly, 1948) H. "Become theorists" represented by Read and N. L. The debate between "magma theorists" represented by Bowen ended with more and more scholars agreeing with the origin of granite magma. However, where did the magma forming the granite body come from? In Bowen's words: Whence the granites? (where does granite come from?)

The overwhelming understanding of this problem is that granite is formed by the melting and solidification of various parts of the rock in the crust. This view combines two different early understandings of the origin of granite: magmatism (granite is believed to be derived from the crystallization of magma) and transformation theory (granite is considered to be a siliceous aluminum-rich sedimentary rock undergoing granitization under dry or watery conditions). Remodeled). It is proposed that granite is the result of crustal rocks undergoing ultra-metamorphism (deep melting), which is of great significance for studying the origin and chemical differentiation of the crust, because they are related to the thermal state of the crust and the composition of the protolith in a specific period, including How much granite syrup can be produced, the temperature and amount and source of water during the formation of granite, the tectonic setting and plate interaction process, etc. ^[2]

To properly understand the so-called "granite problem", one must first understand how geologists came to the conclusion of the current doctrine. It is therefore necessary to expound systematically the knowledge of ideas from a century or more ago. From these narratives, it can be seen that many "new concepts" that have been developed in the last two or three decades are precisely the past 100 years or

A topic that has been discussed and debated for 150 years.

In the 1930s, geologists debated fiercely about which granites were formed by magma and which were metamorphic or metasomatic. This dispute began as early as the Age of Water Marginal Theory, and remained entangled in the idea that granite was formed by sedimentation in aqueous solution until the mid-19th century. Although Hutton has been aware of the process of metamorphism (the term proposed by Leuer), although its nature is not well understood. Much has been written about the formation of granite metamorphisms even before the use of microscopes. Hutton himself strongly advocates the idea of magma origin. According to Hutton's opinion, the characteristics of granite unconformity invading layered rocks, coarse-grained crystal structure, and granite veins in oblique rock layers are all considered to be evidence of granite formation from "subterranean lava" crystals. The magma was later called "magma".

Regarding the "magma" habit, if we do not assume the existence of water, there will be many situations that cannot be explained well. This has long been valued. This is particularly important in the case of granite, so it is necessary here to describe in advance a problem that was revived more than a decade ago. Spllanzani (1794) was probably the first to recognize the genetic significance of the presence of water in molten rocks. Since then, Scorp (1825) has explored the significance of water in lava, and Scheerer (1862) has more explicitly linked the existence of water to granite magma.

In addition, Bunsen (1861) also discussed the geology of granite, especially the genesis of granite. At that time, it was known that the crystallization temperature of quartz in the molten state was higher than that of orthoclase, and much higher than the crystallization temperature of mica. The "anti-fire arrogant" does not recognize that granite is formed from magma, and insists that if the granite is indeed formed from magma, the crystallizing order of these minerals in granite should be quartz-orthoclase-mica. As we all know, the actual crystallization order is just the opposite. It turns out that granite cannot be ignited. According to Bunsen, the melting point of a bulk material is not the same as the temperature at which the bulk material crystallizes from its solution in another case. On the other hand, in further discussion, he compared the behavior of some chemical components in aqueous solution.

The concept of granitization (migration of acidic materials) dates back to the age of Leuer in 1836. At that time, the dispute over the granite cause could be explained in the context of Oslo. Leopold Von Buch surveyed the area in the early nineteenth century, and Charles Leuer directed it at B.M. Keilhau in 1837. A survey of this area was also carried out. Holtedah I (1963) commented fully on these investigations. According to this record, von Bucher (a student of Weilner) believes that most of the granite in this area is in the same form as basalt and other "dark" rocks, covering fossil-containing constructions, and Della Drammen granite is older than limestone and lies beneath limestone. However, Leyle was very skeptical of these explanations. He believed that granite can be obliquely deposited on sedimentary rocks in some places, but this is a secondary feature. Generally, the veins extended by granite extend into the adjacent stratum and make Limestone turns into marble, turning shale into mica schist. In essence, he adopted Hutton's concept of deep formation; molten material invaded violently into older constructions and caused overthrusting of the overlying rock mass. However, Kelho did not accept these ideas, and he did not understand how, in the place previously occupied by the eruption rock, there could be such a huge space for the invasion of the human body immersed in it. As early as 1838, Kelho was probably the first to pay attention to the "space problem" regarding the emplacement of igneous rocks.

Kelho came up with his "transmutations" doctrine instead. The argument of this argument is that the early rock mass was transformed into granite and orthoclase as a slow and stable process. Kelho calls this process "granitification." He also claimed to have found an example of a change from sedimentary rock to granite; for this change he neither paid much attention to the connection to deep phenomena nor considered the temperature increase involved.

However, Kjerulf (1855, 1879) argued that the granite in Oslo was fiery. He acknowledged the space issues raised by Kelho, but he believed that the glowing invaders had engulfed previously deposited rocks. Therefore, the concept of "assimilation" was introduced in igneous petrology. Decades later, Michel-Levv (1894) possibly unknown to Kay Rulf s writingintroduced the concepts of assimilation and assimilation in explaining the genesis of granite in France. At the end of the nineteenth century, the concept of granite formed by metamorphism and metasomatism prevailed in France. Those who were educated in France and Britain, such as Kakirulf of Norway, favored the idea of "magmatic-igneous".

In Finland, Cedholm (1893) had previously opposed the Canadian view of Lawson (A, C. Lawson). Lawson believed that the oldest granites that had invaded the original crust and the oldest sedimentary rocks were due to The oldest sediment at the bottom is formed by remelting. Cedholm (1892) believed that the ringed granite is a true magmatic rock. During the period of strong vertical movement, the magma can fill the graben-like depressions. It was during this period Invaded as a large rock mass. Later, Cedholm proposed his own concepts of regeneration and deep penetration for some other granites, which were partially consistent with the concepts described by Lawson in Canada. T / gerstedt (1893) published a slightly different concept when describing some mixed rocks (later known as mixed rocks) in southern Finland. He believes that these rocks were formed by the infiltration of granitic material into a piece of hemp rock that had deteriorated. This granitic substance contains a considerable part of water. The presence of this water accelerates the progress of the action and allows the granitic substance to form fine veins and penetrate into the gneiss. So he again mentioned the existence of water to explain the formation of fine-grained rock veins with long and narrow resistances; if they were to be explained in other ways, they would encounter considerable difficulties.

Generally speaking, granite generally forms a huge rock foundation. In fact, these foundations are rarely granite, and most of them are composed of mountain granodiorite, steep rock, and quartz diorite. However, some granites are considered to form rock caps, basins, or domes.

Determining the occurrence of granite is an important issue. The terms used to describe the occurrence are of a causal meaning to those who adopt them. According to Gil-bert (1877), the rock cover is the result of the magma's ascending movement, and the meaning of the rock basin is the space formed by the passive magma passive chassis. The term rock foundation was recommended by Suess (1895); it is difficult to infer the immersion of a rock foundation. Hughes himself compared the process of magma rising through the earth's crust with "the process of forcibly penetrating a wooden board with red hot tongs". Nevertheless, this vivid metaphor is by no means an explanation (Levenson-Lexingian). Kakirulf (1855) and Michel-Levi thought that the rock mass was formed by magma assimilating the surrounding rock, and the magma rising speed depends on the speed of magma digesting the surrounding rock and roof. Later, in 1923, Clos believed that many rock masses that had been assumed to be a rock actually were some large intrusive rock beds. For the invasion of rock beds, the difficult space problem is no longer a problem. . In the dome structure, there is often a granite core surrounded by gneiss. Finnish geologist Gadolin (1858) was the first to describe the dome structure in northern Ladoga Lake, Pusunsaari. According to his opinion, the dome structure is a granite rock mass invaded into the gneiss construction. The upper contact surface has a slower inclination angle, and the downward angle gradually increases. In 1951, Escola explained the dome as follows: "As summarized in my 1949 paper, the facts show that granitization has specially modified the rock mass with the addition of a large amount of potassium and volume increase. Marginal part of the rock, so that the ancient intrusive body uplifted into the rock dome. " ^[3]

I. Magma-Hydrothermal Deposit

(1) Rare metal pegmatite deposits associated with shallow crust-type granites;

(2) Rare metal granite deposits associated with shallow crustal granites;

(3) Porphyry copper and molybdenum deposits related to deep-type crustal granites.

Hydrothermal Deposit

(1) Shikayan deposits related to shallow-crust granite and deep-earth-type granite;

(2) The yunenite deposit associated with shallow crust-type granite,

(3) gold-bearing quartz vein deposits related to deep-crust deep granite,

(4) Veined lead-zinc deposits related to crustal deep postal granites:

(5) Intrusive massive sulfide deposits related to deep-type crustal granite. ^[4]