Source of granite

Release time:

2023-11-08

As the iconic 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 tectonism, metamorphism and mineralization of the continent. From the 18th century when geological science was still in the cradle stage, the problem of granite genesis was the subject of many debates. The debate on 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 advent of plate tectonic theory in the 1960 s, many explanations about the genesis of granite have been placed in the theoretical framework of the plate to re-understand. In many cases, perceptions seem to converge, but the actual debate continues.

The misconception of Bowen's (1914,1922,1948) basaltic magma crystallization differentiation theory is to combine mineral crystallization order with magmatic rock sequence from basic to acidic. The experimental results show that the crystallization differentiation of basaltic 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 be applied to the magma system of different components. In other words, the first crystals from the magmatic system are not necessarily basic rocks, and the final formation is not necessarily felsic (acid) rocks, because the nature of the rocks crystallized from the melt depends on the composition of the melt rather than the order of mineral crystallization (Kennedy,1933). Walton(1960) commented on Bowen's understanding as follows: "There is nothing wrong with Bowen's chemical theory or its application to the separation of basaltic magmas, which remains a fundamental principle of petrology. However, the theory of pyrogenesis is rigidly bound to a single model, and it is a bit speculative to suggest that most of the evolution of igneous rocks is due to the cooling, crystallization and separation of the crust due to the invasion of basaltic magma. The same chemical theory can be applied to other models."

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

The overwhelming understanding of this problem is that granite is formed by the partial fusion of rocks of various compositions in the earth's crust. This view combines two different early understandings about the origin of granite: magmatic theory (that granite comes from the crystallization of magma) and metamorphism (that granite is rich in silicon and aluminum sedimentary rocks under dry or water-bearing conditions by granitalization transformation). It is proposed that granite is the result of hypermetamorphism (deep melting) of crustal rocks, which is of great significance to the study of the origin and chemical differentiation of the crust, because they are related to the thermal state of the crust and the composition of the original rock in a specific period, including how much granite pulp can be produced, the temperature and the amount and source of water at the time of granite formation, the tectonic background and the plate action process, etc.

Introduction of types of granite

Natural granite has been paid more and more attention because of its own characteristics

Introduction of types of granite

Natural granite has been paid more and more attention because of its own characteristics