Glacial diamictite may provide important information on paleoenvironment and average composition of the upper continental crust(UCC).In this study,we report sedimentary facies,petrological and geochemical characterist...Glacial diamictite may provide important information on paleoenvironment and average composition of the upper continental crust(UCC).In this study,we report sedimentary facies,petrological and geochemical characteristics of Neoproterozoic diamictite from a profile of the Luoquan Formation on the southern margin of the North China Block(NCB).Upwards the sampling profile,lithostratigraphic strata vary from massive diamictite with poorly sorted carbonate gravels to laminated diamictite with small gravels of terrestrial detrital materials.Along the profile,CaO-MgO-LOI-Sr values decrease with the increase of SiO_(2)-Al2O_(3)-K2O contents.All these petrological and geochemical variations indicate a change from lodgement till deposition in the proximal of ice sheet to ice-rafting deposition in glacial-marine environment with less dolomite to supply their source.Together with previous studies on diamictite from other outcrops on the NCB,the deposition of Luoquan diamictite reflects that the glaciation on the NCB vanished and the ice-rafting effect weakened with glacial transgression process.In addition,significant co-variations of various elements with La and Al2O_(3)confirm the significant conservation of most analyzed elements during the sedimentary processes to produce diamictite.展开更多
The Late Precambrian Luoquan Formation occurring on the southern margin of the North China platform is of important significance for the study of the tectonics, palaeogeography, palaeoclimatology and regional stratigr...The Late Precambrian Luoquan Formation occurring on the southern margin of the North China platform is of important significance for the study of the tectonics, palaeogeography, palaeoclimatology and regional stratigraphy of the North China and Yangtze platforms. The origin of diamictites of the formation has long been a subject of controversy. Recently a certain type of cross bedding structure has been recognized in the massive diamictite. Analysis of the process of deposition indicates that the structure was formed by the basal melt-out process of the glacier and, to some extent, its form is the manifestation of the primary structure of basal debris-rich glacial ice. The discovery of this sedimentary structure is inducive to the understanding and reconstruction of the features and environmental conditions for the development of the glaciers in the Luoquan Glacial Epoch.展开更多
基金supported by the National Natural Science Foundation of China (Mos.41776069 and 41572047 to Yuanyuan Xiao)Strategic Priority Research Program of the Chinese Academy of Sciences (No.XDB42020302)+1 种基金the Taishan Scholar Program of Shandong (No.ts201712075)Aoshan Scholar Program of the Pilot National Laboratory for Marine Science and Technology (Qingdao) to Weidong Sun。
文摘Glacial diamictite may provide important information on paleoenvironment and average composition of the upper continental crust(UCC).In this study,we report sedimentary facies,petrological and geochemical characteristics of Neoproterozoic diamictite from a profile of the Luoquan Formation on the southern margin of the North China Block(NCB).Upwards the sampling profile,lithostratigraphic strata vary from massive diamictite with poorly sorted carbonate gravels to laminated diamictite with small gravels of terrestrial detrital materials.Along the profile,CaO-MgO-LOI-Sr values decrease with the increase of SiO_(2)-Al2O_(3)-K2O contents.All these petrological and geochemical variations indicate a change from lodgement till deposition in the proximal of ice sheet to ice-rafting deposition in glacial-marine environment with less dolomite to supply their source.Together with previous studies on diamictite from other outcrops on the NCB,the deposition of Luoquan diamictite reflects that the glaciation on the NCB vanished and the ice-rafting effect weakened with glacial transgression process.In addition,significant co-variations of various elements with La and Al2O_(3)confirm the significant conservation of most analyzed elements during the sedimentary processes to produce diamictite.
基金This research(Project No.4917013)was supported by the National Natural Science Foundation of China
文摘The Late Precambrian Luoquan Formation occurring on the southern margin of the North China platform is of important significance for the study of the tectonics, palaeogeography, palaeoclimatology and regional stratigraphy of the North China and Yangtze platforms. The origin of diamictites of the formation has long been a subject of controversy. Recently a certain type of cross bedding structure has been recognized in the massive diamictite. Analysis of the process of deposition indicates that the structure was formed by the basal melt-out process of the glacier and, to some extent, its form is the manifestation of the primary structure of basal debris-rich glacial ice. The discovery of this sedimentary structure is inducive to the understanding and reconstruction of the features and environmental conditions for the development of the glaciers in the Luoquan Glacial Epoch.
