Enigma of granitoid bodies without contact metamorphic halos : Genetic solutions
General characteristics of granitoid bodies without contact metamorphic halos are first demonstrated : (1) They have common annular to circular cross sections (2) The existence of a shear zones with cataclastic to protomylonitic textures of host rocks. (3) Nonexistence of contact metamorphism in hostrocks or existence of halos with paragenesis which donot correspond at all with thermal evolution of granitoid bodies.(4) Existence of a network of diabasic rocks in form of parallel or discontinuous bodies. (5) Discordant Zircon age with realistic geological ages. All these characters invites an especific mechanism of intrusion. Our regional investigation demonstrated that : These granitoid bodies can not be envisaged as hot magmatic bodies , Their existence in present crustal level can be reconsiled with diapiric movement of sialic mass due to gravity movements. The intrusion of mafic magmatic rocks into sialic rocks may cause anatexis which in turn may change viscosity and enhancement of diapiric uprise.
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