The hypothesis of melting in-situ has systematically expounded the genesis of granite which constitutes an important part of the continental crust, and of the various geological and geochemical phenomena concerning the genesis of granite in the view point different from the traditional ones. The in-situ melting model of the formation of granitic magma, the metallogenic hypothesis relative to the model, and the framework of geochemical field of the elements consist of a complete logical system. This paper gives briefly an introduction to the system.