Geochronology Of Huyanshan Alkaline Complex In The Middle Segment Of The Luliang Uplift Belt And Its Tectonic Characteristics Around

Huyanshan alkaline complex outcropped in the middle east wing of lüliang uplift belt,which belong to the Fenhe alkaline intrusive rock belt. So far, although much of work has been done to its petrographic and geochemical study, it has still been lack of credible chronology data.This research has got the latest LA-ICP-MS zircon U-Pb ages of the grain- monzonite and syenite taken from Huyanshan alkaline complex and use them to determine its formation time as well as to limit the duration of the magma activity. The formation age and order of the main structure as well as the relationship with Huyanshan alkaline complex have been discussed based on the study of morphological characteristics and combination form of the fault and fold.This research will help to provide a new evidence for understanding the tectonics and magma activities of North China Craton in the Midwest.Through the study of this article, some understandings are achieved as follows:1. Huyanshan alkaline complex are divided into six different types of rocks: granular-monzonite, porphyritic-like monzonite, porphyritic monzonite, quartz syenite porphyry, syenite and syenite porphyry.The first four units are named as Guo Guliang sequence according to the characteristics of main rock forming minerals and rock mass space associated relations;The later two units are named as Ketou sequence. Through field study on the relationship of the contact between each unit of rock, we confirm the grain monzonite is the earliest intrusion of Huyanshan alkaline complex, and syenite is the latest one.2.The Huyanshan alkaline complex are mainly composed of monzonite and syenite.Through the test method of LA-ICP-MS,we get that the weighted average age of the grain- monzonite is 127±1Ma and the syenite is 114±4Ma.They illustrate the Huyanshan alkaline complex formed in the early cretaceous. It is confirmed that grain-monzonite is the early product of magmatic activity, and syenite as a product of the late in order to the characteristics of the magma material?mineralogy?rock geochemical?Contact relationship of the intrusive.So,the range of the emplacement time of the Huyanshan alkaline complex can be limted in 127±1Ma~114±4Ma.3. Combining with the research results of the High precision zircon U- Pb chronology data and the magma source of the alkaline complex located at the Huyanshan?Zijinshan and Taershan-Erfengshan,it is fully showed that strong alkaline magmatism have taken place in the early cretaceous in the depths of central place of the midwest of North China Craton such as the Lüliang mountain including Huyanshan. The magma derived from the partial melting of enrichment mantle or the mix of partial melting of crust-mantle.4. The research area developed NNE, NE and nearly SN and combination of "S" type fracture and fold which are belong to Yanshanian. The NNE and NE structure are given priority to the east and northwest,which are more for high angle normal fault and form a series of horsts and grabens with different sizes. The fault zone are arranged parallel with equally spaced, Of which the small fold structure distributed. The nearly SN and "S" type structural are mainly distribution at west and south,which were formed by extrusion and early before the fracture. The order of different structure combination form can be summarized as the following points: The formation age of SN structure are earlier than the NE and NNE structure's because of they are surrounding or cutting by the NE and NNE structure; The formation of "S" structure obviously affected by the Huyanshan alkaline complex,namely the strong compression made by the alkaline alkaline magmatic's emplacement Lead to the shift of SN structure to "S" structure; The NE and NNE structure formed at the same time as the Huyanshan alkaline or later,namely they formed at The early cretaceous or even later.