| Antarctica is located at the southernmost tip of the earth and covers an area of about 14 million square kilometers.The entire continent is located south of 60°S and is basically covered by snow and ice.There are many large sedimentary basins on the continental margin,and the resources are extremely abundant.The southern ocean surrounds the Antarctic,and the surrounding ocean current activity is a very important part of the global climate change.The Gondwana paleo-colon split,after two stages of rift,formed the Antarctic rift system and eventually formed the Ross Sea.The Ross Sea experienced a transition from diffusion to concentrated tectonic activity.Based on the existing geological and geophysical data of the Ross Sea and its surrounding areas,this paper expounds the viewpoints and evidences of the predecessors,and expounds the regional topography,gravity and magnetic anomalies,fault structures and magmatic activity distribution characteristics and tectonic dynamic evolution of the Ross Sea.By calculating the first-order directional derivative of gravity and magnetic anomalies in the Ross Sea area,the location of the existing faults is verified,and the first-order directional derivative of gravity and magnetic anomalies is used to infer the trend of the fault structure in the Ross sea area.Mesh seismic profiles for verification and control.Secondly,through the analysis of the Gravity anomaly total gradient mode and the Magnetic analysis signal anomalies,combined with the study of the regional geological tectonic background,the boundary of the eastern basin is refined.And through the Magnetic analysis of signal anomalies,scope activity magma around the Ross Island and Melbourne in Cenozoic era.In order to further understand the basin structure in the Ross Sea area from the longitudinal direction,and to verify the existing inferences,three gravity and magnetic model sections were established along the latitude direction,and Explanation the gravity,magnetic and thermal anomalies of the Ross Sea.The Ross Sea overpass structure is very obvious.The terrain is mainly affected by glaciers.In the eastern basin,the central trough basin and the northern basin,the land is strip-shaped and perpendicular to the edge of the shelf,and it is characterized by deep inside and shallow outside.These features on the terrain suggest that Rose Bay is affected by the advance and retreat of the Ross Ice Shelf and the Victorian Ice Shelf The sedimentary basement direction is similar to the north-south direction.Except for the uplift in the eastern part of the central trough basin,the remaining basins exhibit obvious characteristics of the extensional basin.The base undulating direction is oblique to the topography.The Free-air gravity anomaly and the Bouguer gravity anomaly coincide with the trend of the basement in the interior of the basin.However,there is a positive Free-air and Bouguer gravity anomaly in the large stretch basin of the Ross Sea,and a negative anomaly occurs when the basement is raised.The magnetic anomalies are mainly manifested by large fluctuations in the Ross Island and the Cullman Heights and the northeastern margin of Victoria,corresponding to the active area of the magma in the west of Ross Sea.The relatively flat areas of magnetic anomalies include the Victoria Basin,the central trough except for a small part of the eastern part,and the central part of the eastern basin.The eastern part and the central part of the central trough basin show great differences in gravity and magnetic anomalies.Compared with other basin areas,the consistency of gravity and magnetic anomalies shows obvious differences.Using the obtained gravity and magnetic data in the Ross Sea area,the conversion processing of the gravity and magnetic anomalies is performed to find an abnormal processing method suitable for the structure of the region.The first derivative in different directions is calculated for the gravity and magnetic anomaly data,and the total gradient of the abnormal data and the analytical signal of the geomagnetic anomaly are calculated.From the first-order derivative results in all directions,the first-order derivatives in the 45-degree and 135-degree directions are more able to reflect the actual situation of the fault structure in the Ross Sea region,and the gravity anomalies are better than the results of the magnetic anomaly calculation in the Victoria Basin and the Central Trough Basin,but in other areas of the Ross Sea,the gravity direction derivative appears as a block distribution,and the effect on the fracture identification is limited,and the first-order derivative of the magnetic force is superior to the first-order derivative of the gravity.The total gradient mode of gravity anomaly has a qualitative improvement in most areas of the Ross Sea compared to the first-order directional derivative,especially in the Victoria Basin,the Central Trough Basin and the West Ross Sea area,but in the eastern basin,it is possible The 45-degree,90-degree first-order derivative is better,which is not the result of the lower resolution of the total gradient data itself,but the balance of the mapping effect.The geomagnetic anomaly analysis signal calculation results can clearly identify the magma active area in the Ross Sea area,and compared with the predecessors,the Ross Sea fault is dominated by NW-SE,and the geomagnetic anomaly analysis signal can identify multiple NE-NW anomalous bands.Based on the understanding of topography,gravity anomaly,magnetic anomaly,fault structure and magmatic activity distribution,the Parker-oldenburg field iterative inversion method and power spectrum method were used to invert Moho surface and the Curie.By comparing the fluctuations of the two,the deep structural information of the Ross Sea area is provided.Based on the inversion of the Curie,the heat flow anomalies in the Ross Sea area were inferred,and anomaly of heat flow more clearly shows the intensity change of the magma in the deep mantle.The results show that the average heat flow value of the West Ross Sea is higher than the average heat flow value of the East Ross Sea,and the high heat flow area is especially concentrated in the Victoria Basin.The thermal conditions in the Ross Sea reflect an active cracking environment with high heat flow values.This high heat flow may be a direct indication of the anomaly of the upper mantle and is also a typical feature of the crustal tension reduction in the rift basin.The high heat flow value also coincides with the location of the rift magma in the West Ross Sea area.There are three types of heat flow anomalies in the Ross Sea area:the first is the low heat flow region in the eastern basin and the northern basin.Although they belong to the same low heat flow area,their geological structures are different.The geothermal flow in the northern basin is greatly affected by the northern ocean basin while the geothermal flow value in the eastern basin is relatively independent,showing structural inactivity.The second type is the high heat flow anomaly area,mainly the central highland and Victoria area.The high heat flow in the central highlands may be a heat residue in the active period of the structure.The Victoria Basin is a contemporary active tectonic basin,and there is a large-scale magmatic intrusion in the northern Cullman Highlands and the Southern Ross Island region,resulting in extremely high heat flux values in the Victoria Basin.The third type is the sub-high heat flow area of the central trough basin.The central trough basin is a geologically inactive area,similar to the eastern basin,However,due to the location between the two high heat flow areas in the central highlands and the Victoria Basin,lateral heat transfer may result in a greater heat flow value in the central trough basin than in the eastern basin.Finally,The tensile structure environment and high heat flow distribution in Ross Sea provide favorable conditions for the occurrence of natural gas hydrates.Combined with the previous research results,it is speculated that there is a huge amount of natural gas hydrate in the Ross Sea area,and the amount of methane in the basin of the Ross Sea area is estimated to be 2.77×1011 m3. |
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