An In-Situ Melting Model of Granite Formation: Geological Evidence from Southeast China

摘要

An in-situ melting model is proposed to explain the origin of granite by the melting of sialic upper crustal rocks. Unlike the traditional magma-intrusion hypothesis, this model regards the upper crust as a closed system, and the formation of granite as resulting from a change of intracrustal material from order (protolith) to disorder (melts) to new order (granite), with variations of entropy of the system. Magma formed through in-situ melting is inferred to he layer-like, and the upper limit of the melt layer is defined as the melting interface (MI) that marks the change from a solid to a partially molten condition. Granite bodies are considered to be the protruding parts of a paleo-MI (PMI), and their shape and size reflect the geometric relationship between the PMI and the present-day denudation surface. The physical process of rock melting and the formation mechanism the melt layer, and their relationship to the shape and size of granite bodies (and to the migmatites and other metamorphic rocks in southeast China) are discussed in this paper.