Petrology And Zicon U-Pb Chronology Of Dykes In Nankou Beijing

There are often a regional dykes after the large-scale granitic magmatism in the orogenic belt, which are always called the post-orogenic dyke complex, characterized by the formation of nearly the same time,wide spectrum and small size components. In recent years, scholars pay more attention on these dikes. Through previous study, they can be divided into lamprophyre, basalt, diorite, granodiorite and granitic mass based on lithology. Some scholars believe that their emplacement suggest the large-scale extension, which means the beginning of the magma Wilson cycle. In recent years, some geologists proposed the formation of these dyke swarms in the regional tectonic stress field from compression to extension conversion stage, and can be used to calibrate the end of the orogenic process, thus called after orogenic vein rock composition. Although many researchers have noted the country rock of the importance of such connections, but also the theoretical model is relatively reasonable, but still relatively accurate age of the lack of data validation is indeed a combination of these dikes formed the same period. In this paper, Beijing Nankou dyke swarms, for example, through field observations and geochemical and U-Pb zircon age of rock and mineral data analysis provides a relatively accurate school information and zircon age, verification of the study area, while the formation of dykes.Interspersed in the study area dikes Rock Foundation, the dykes a few centimeters to the width of the range of tens of centimeters, there is completely different lithological contacts between dikes formed interpenetrating composite dikes. The results show that the study area dikes range of SiO2 content increases 49.09% -75.43%, and the main rocks gabbro, lamprophyre, diorite porphyry, granodiorite and granite, major elements show the basic dykes have shoshonitic series features a high potassium acid dykes characteristics of the alkaline rocks. Light rare earth (LREE) compared with enriched distribution patterns characterized by right-wing, than the flat HREE, (La / Yb) N = 13.79-44.2, with the exception of granite samples negative Eu anomalies, the majority of rock samplesδEu is between 0.70-1.05 . Dikes enriched Rb, Sr, K and other large plum lithophile elements and loss of Nb and Ti.According to the analysis we get the following conclusions:Nanyan swarms formed at almost the same time, all belonging to the late Yanshan intrusive rocks, in the Yanshan orogenic process, without major tectonic movements after that. Thus such dyke swarms may suggest the end of the orogenic. Lithology of these dyke swarms distribution of a wide spectrum, small size and mutual relations that the increase in rate cuts fast, but the increase rate of magma and magma viscosity in addition to, but also with the formation of dikes in the channel in which the tectonic stress environment, so different lithology of magma could rise may indicate that a rapid extension of the tectonic stress environment. In addition, based on previous analysis of the heat transfer rate, post-orogenic dikes in combination should also be accompanied by the formation of large-scale fluid flow. As the deep fluid in the concentration of ore elements strongly depends on the pressure, the new model means petrogenesis orogenic dikes in combination with the mineralization accompanied by students. Observations in the wild can also be identified based on outcrop observations and ore forming fluids in the channels of mass accumulation of elements in place. Therefore, the inference orogenic dikes in combination can not only be used to calibrate the regional orogenic end of the process of time, is also an effective regional exploration prediction flag.