The Lithogeochemical Characteristics And Protolith Formation Of Wulashan Gr.in Central Inner Mongllia

Reconstruction of early palaeo-continent,properties and evolution of early continential crust has become one of significant front problems of contemporary geosciences.But Wulashan Gr.is high-grade metamorphic region in early continrntal crust development.The research of its characteristic and research of origin has important scientific significant for probing into the evolution process of the early continental crust formation of this type region.The paper is based on regional geological survey project of "1: 50000 Debusige Temple,Dalagaigaole,Miaokou in Inner Mongolia",entitled?The Lithogeochemical Characteristics and Protolith Formation of Wulashan Gr.in central Inner Mongllia?.The study area has a complex tectonic setting,and which located in the Wulashan area of central Inner Mongolia.The tectonic location belongs to the western part of the northern margin of the North China Craton and the western part of the Yanshan-Yinshan Mesozoic orogenic belt.On the basis of fully understanding and mastering the predecessors' data and research results,find out the distribution in space,the characteristic of rock composition,stratigraphic sequence and petrological characteristics,through the systematic analysis of Wulashan Gr.in central Inner Mongolia.The protolish formation has been restored based on the lithsgeochemical characteristics and varied protolith recovery diagrams,further discussing about types of protolish formation and depositional environment of protolith of Wulashan Gr.Obtain the following knowledge and results:1?Based on the characteristics of the symbolic marker layer,combined with the rock assemblage,distribution,color,contact relationship and mineral composition,the Wulashan group is divided into five rocks by means of the "tectonic-rock-event" method,through field geological prospecting and typical measured profile,from the bottom to the top,the hornblende gneiss group,the biotite gneiss group,the garnet-biotite gneiss group,the garnet-leucoleptite group and the marble rock group.2?Hornblende gneiss rock group is characterized by amphibolite as the symbol layer,the main rock types:hornblende plagioclase gneiss,biotite hornblende plagioclase gneiss;Biotite gneiss group in quartzite marked layer,the main rock types: biotite plagioclase gneiss and biotite hornblende plagiogneiss;Garnet-biotite gneiss group is an Al-rich gneiss characterized by rich garnet,sillimanite,cordierite and Al-rich mineral characteristics,the main rock types:Garnet biotite plagioclase gneiss,garnet biotite gneiss,two biotite plagioclase gneiss;There are significant differences in color and mineral content of garnetleucoleptite group different from Garnet-biotite gneiss group,the main rock types: light grey biotite garnet monzonitic leucoleptite,Garnet plagio claseleu colep-tite,sillimanite garnet granulite;The marble rock group is characterized by serpentine marble.3 ? Through a comprehensive analysis of stratigraphic features,rock type,metamorphic rock restore the original illustrations,etc.It is believed that the hornblende gneiss group is constructed of volcanic rocks with a certain amount of debris deposition consisting of volcanic-sedimentary structures,and the biotite gneiss group is volcanic-sedimentary construction,and the garnet-biotite gneiss group is a fine debris deposition of complex mineral sandstone,mainly greywacke,mudstone and continental clay rock.The garnet-leucoleptite group is the coarse debris deposition of miscellaneous sandstone;and the marble rock group is constructed by chemical deposition.The sedimentary cycle of volcanic debris deposition-chemical deposition is shown.