The Geological Characteristics, Genesis And Tectonic Significance Of The Taiping Giant Porphyritic Monzogranite Dike Group In Southern Anhui Province

There are a series of NNW trending granite dykes and near-east-west trending faults associated with the dykes in the middle and western part of the Taiping granodiorite in southern Anhui Province.Most previous studies have been carried out on the two main bodies of the Taiping-Huangshan complex rock mass--Taiping granodiorite and Huangshan granite,but few detailed studies have been carried out on the dyke group inside the rock mass.This paper focuses on the giant porphyritic monzogranite dike group in Taiping granitic diorite,carries out a detailed systematic analysis of petrology,chronology and petrogeochemistry,and analyzes the tectonic stress in combination with the regional tectonic stress field.It is found that the lithology of the granitic samples in in Taiping granitic diorite is giant porphyritic monzogranite.U-Pb zircon dating shows that the forming age of giant porphyritic monzogranite dike group are concentrated in130¹32Ma,between Taiping granodiorite and Huangshan granite.Rock belongs to high potassium calc alkali,SiO₂ content>65%,high total alkali content,for aluminum,enrichment of light rare earth,rare earth distribution curve to the right of the weak Eu negative anomaly curve,shows for type A granite rock characteristics,but does not have such as Huangshan the characteristics of the typical late Yanshanian granite type A granite,indicates the environment to make the transition to stretch.Since the late Jurassic,the near south-to-north compressive stress and the left shear of the basement fault zone had acted together,and the force dual in the northwest and south-to-east directions had formed wild goose inclined split inside the Taiping rock mass.Early cretaceous,regional tectonic stress field from nearly NS-trending extrusion to what extended,type A granite magma upwelling along the fracture penetration,produced in the direction of the magma intrusion nearly north-south local extrusion,under the continuous joint action of near-north and south local compression and east-west extension,the fractures in the Taiping rock mass expanded further and were filled by the porphyritic monzogranite dykes.Therefore,the transition from the extrusion environment of Taiping granodiorite to the extensional environment of Huangshan granodiorite is not abrupt and there is a transition link.