The Distribution Of Igneous Rocks And Lithospheric Thinning Processes Of Yanshan Period In Yanshan Area, Beijing

Beijing area has a very wide distribution of igneous rock, the exposed area is more than 2,000 square kilometers, accounting for about one-fifth of the mountain area. Yanshan period igneous rock is about 3,600 square kilometers. Early Jurassic igneous rock is about 277.52 square kilometers, accounting for 7.71 percent of the total area. Medium Jurassic igneous rock is about 1466.1 square kilometers, accounting for 40.73 percent of the total area. Late Jurassic igneous rock is about 459.65 square kilometers, accounting for 12.78 percent of the total area. Early Cretaceous igneous rock is about 1395.53 square kilometers, accounting for 38.78 percent of the total area.Yanshan period is the strongest and the most frequently magmatic activity in the study region and North China platform. Magmatic activity, including volcanic eruptions, medium - deep into magma intrusion. From the magma composition, early period is basic and neutral, and the late is medium acid, acid and weak alkaline. Widely distributed in the Mesozoic igneous rock in Yanshan area, includes granite and volcanic rock consisting mainly of intrusive rocks.Multi-source data and the integrated treatment of multiple source data for the analysis of complex geological prospecting is the current widespread interest in the subject, but also the future development direction. From the RS, GPS access to the study, to extract information in GIS, reorganization and information processing, another professional models and software systems analysis and processing of new information generated data, it has broken the traditional method of qualitative analysis of geological, and then entered Computer quantitative research to accurate positioning of the times, advanced from the GIS system software for remote sensing image with the conventional interpretation of multiple statistics, image analysis of the organic integration, provide a convenient analysis for workers in decision-making. Beijing magmatic activity is subject to the whole basement faults control.Yanshanian invasive activities is the most violent, largest and particularly frequent. It makes intrusion and mineralization several times. Mainly exposed in North mountain. In addition, there are implicit dykes covered with the fourth in plain. On the basis of the magmatic rock types and characteristics of activities, the igneous rock can be divided into west mountain region, north mountain region and northeast mountain region.According to the study of igneous rock, we conclude that the source of magma is not enriched mantle (EMI), but asthenosphere mantle. This conclusion is not consistent with thermal erosion and/or chemical metasomatism mechanism which thin lithosphere mantle by changing lithosphere mantle to EM1.So we conclude that the main mechanism for thinning of lithosphere in eastern China is breakoff of lithosphere.