Formation And Evolution Of Mortar Micro-geomorphology In Laoshan Mountain

In recent years,a micro-geomorphology similar to mortar has attracted the attention of domestic and foreign scholars,the study of its origin and evolution has become one of the hot spots in the international academic community,the main existing terms are "tafoni","alveolar weathering","honeycomb weathering","moulin","pothale" and "mortar",this article uses "natural-mortar".In recent years,some scholars have considered the mortar micro-geomorphology in the eastern part of China as an important evidence for the existence of the Quaternary glaciers,initiate a new round of debates,and Laoshan also discovered this type of mortar micro-geomorphology,to better explore the issue of Quaternary glaciers in eastern China,it is very important to study the formation and evolution of the mortar micro-geomorphology(bubble-like caves and natural-mortar)in Laoshan Mountain.Aiming at the development of rocks around the large-scale bubble-like caves in Laoshan Mountain,there are Small-scale bubble-like caves,and the phenomenon of coexistence of miarolitic cavity(small bubble holes)and natural-mortar in the same rock mass.This article makes comprehensive use of interdisciplinary methods such as petrology,mineralogy,geochemistry,quaternary geology,geomorphology,and morphology.through the analysis of rock geochemistry and rock strength,the degree of weathering of bubble-like caves and natural-mortar has been clarified,according to the analysis of morphological characteristics,the connection between bubble-like caves and natural-mortar was clarified,and based on previous research,comprehensive analysis of surface morphology and rock geochemistry of rock,for the first time,the influencing factors of the mortar micro-geomorphology development in miarolitic granites,the system divides the stage of the development of the mortar micro-geomorphology.This paper comprehensively analyzes the rock mineral composition,major elements composition,rock surface macroscopic features,and rock surface stregth characteristics of mortar micro-geomorphology,the results show that:Natural-mortar wall roughness,the surface rock strength is lower than the inner wall of a large bubble-like caves,there are obvious K+ and Na+ migrations and enrichment of Fe3+,Chemical alteration index(CIA),quartz/feldspar,Loss on Ignition(LOI),and illite content were both higher than those of large bubble-like caves,the inner wall of the large bubble-like caves is fresh,and the degree of weathering from inside to outside gradually increases.The inner wall is basically not affected by external forces,and the degree of weathering of the rock inside the natural-mortar is much higher than that of the inner wall of the bubble-like caves.Field macroscopic data analysis results show:Small-scale bubble-like caves and Large-scale bubble-like caves are ellipsoidal macroscopically resembling bird eggs,and the natural-mortar are mostly flat semi-ellipsoids,some natural-mortar are similar to semi-ellipsoids formed by joint cutting bubble-like caves,both have the same origin,Weathering changes the shape of mortar,resulting in a slight difference in morphology between mortar and bubble-like caves.Comprehensive field geological survey results,relevant research data,lithological characteristics,and scanning electron microscope(SEM)analysis results,For the first time,there are three main factors influencing the development of mortar micro-geomorphology in Laoshan:1)The research area is high-silicon,low-aluminum,alkali-rich medium-granular alkaline granite,miarolitic cavity development,After the bubble-like caves(miarolitic cavity)are exposed,some opening up is the stone mortar,and some small miarolitic cavity will continue to be weathered,expanded,and deformed to become stone mortar;2)The semi-ellipsoidal cavity formed after the exposure of the bubble-like caves in the study area is one of the initial forms of natural-mortar,Natural-mortars weathering,deformation velocity arc affected by joints and directivity;3)The external forces caused by climatic conditions mainly include:chemical weathering,wind erosion,freezing and thawing,salt weathering,and biological weathering.Based on the field geological survey and previous data,this paper firstly classifies the mortar micro-geomorphology into the initial stage,growth stage,mature stage,and decline stage,and elaborates the morphological characteristics and formation mechanism of each stage.This paper provides new ideas for resolving the related disputes in the Quaternary environment in the Lushan Mountains.It is of great significance for studying the paleoclimate and paleoenvironment in the eastern part of China and for discussing the Quaternary glaciers in the eastern part of China.