Sean T. O’Hara, Patrick J. McGovern, Danielle vonLembke
{"title":"金星萨帕斯蒙斯岩浆室减压及同心地堑和晚期流动单元的形成","authors":"Sean T. O’Hara, Patrick J. McGovern, Danielle vonLembke","doi":"10.1029/2023JE008134","DOIUrl":null,"url":null,"abstract":"<p>Sapas Mons is a large shield volcano in Atla Regio on Venus. Its summit region is partially encircled by a system of pits and extensional faults (graben). The existence and configuration of this system have been attributed to stresses generated above the margin of a magma chamber spanning the region beneath the summit. The proposed stress-generating mechanism includes either withdrawal of magma from or solidification of magma within such a chamber (Keddie & Head, 1994, https://doi.org/10.1007/bf00644896). To explore these hypotheses, we calculate Finite Element Method models of stresses and deformations resulting from magma chamber depressurization beneath a Sapas Mons-sized edifice with axisymmetric geometry. For a range of magma chamber depths and vertical thicknesses, we determine the minimum under pressure that produces a stress state predicting failure in circumferential normal mode at the observed position of the graben system. We also determine maximum under pressure under two conditions: (1) no failure (thrust fault mode) predicted at the summit, and (2) predicted failure (thrust fault mode) limited to within 10 km of the summit. We find that successful models require sill-like chamber geometry with vertical thicknesses <1.5 km (diameter to thickness aspect ratios >66:1), and chamber depth <8 km beneath the summit. Calculated reductions in chamber volume are comparable to volumes of late-stage eruptive units mapped at Sapas Mons, favoring the magma withdrawal hypothesis for graben system formation. Evidence that unit 5 of Keddie and Head (1994, https://doi.org/10.1007/bf00644896) overlapped in time with, but largely postdated, the graben forming event renders it the most likely destination for magma removed from the chamber.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":null,"pages":null},"PeriodicalIF":3.9000,"publicationDate":"2024-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Magma Chamber Depressurization and the Creation of Concentric Graben and Late-Stage Flow Units at Sapas Mons, Venus\",\"authors\":\"Sean T. O’Hara, Patrick J. McGovern, Danielle vonLembke\",\"doi\":\"10.1029/2023JE008134\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p>Sapas Mons is a large shield volcano in Atla Regio on Venus. Its summit region is partially encircled by a system of pits and extensional faults (graben). The existence and configuration of this system have been attributed to stresses generated above the margin of a magma chamber spanning the region beneath the summit. The proposed stress-generating mechanism includes either withdrawal of magma from or solidification of magma within such a chamber (Keddie & Head, 1994, https://doi.org/10.1007/bf00644896). To explore these hypotheses, we calculate Finite Element Method models of stresses and deformations resulting from magma chamber depressurization beneath a Sapas Mons-sized edifice with axisymmetric geometry. For a range of magma chamber depths and vertical thicknesses, we determine the minimum under pressure that produces a stress state predicting failure in circumferential normal mode at the observed position of the graben system. We also determine maximum under pressure under two conditions: (1) no failure (thrust fault mode) predicted at the summit, and (2) predicted failure (thrust fault mode) limited to within 10 km of the summit. We find that successful models require sill-like chamber geometry with vertical thicknesses <1.5 km (diameter to thickness aspect ratios >66:1), and chamber depth <8 km beneath the summit. Calculated reductions in chamber volume are comparable to volumes of late-stage eruptive units mapped at Sapas Mons, favoring the magma withdrawal hypothesis for graben system formation. Evidence that unit 5 of Keddie and Head (1994, https://doi.org/10.1007/bf00644896) overlapped in time with, but largely postdated, the graben forming event renders it the most likely destination for magma removed from the chamber.</p>\",\"PeriodicalId\":16101,\"journal\":{\"name\":\"Journal of Geophysical Research: Planets\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":3.9000,\"publicationDate\":\"2024-06-22\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Geophysical Research: Planets\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://onlinelibrary.wiley.com/doi/10.1029/2023JE008134\",\"RegionNum\":1,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"GEOCHEMISTRY & GEOPHYSICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Geophysical Research: Planets","FirstCategoryId":"89","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1029/2023JE008134","RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
Magma Chamber Depressurization and the Creation of Concentric Graben and Late-Stage Flow Units at Sapas Mons, Venus
Sapas Mons is a large shield volcano in Atla Regio on Venus. Its summit region is partially encircled by a system of pits and extensional faults (graben). The existence and configuration of this system have been attributed to stresses generated above the margin of a magma chamber spanning the region beneath the summit. The proposed stress-generating mechanism includes either withdrawal of magma from or solidification of magma within such a chamber (Keddie & Head, 1994, https://doi.org/10.1007/bf00644896). To explore these hypotheses, we calculate Finite Element Method models of stresses and deformations resulting from magma chamber depressurization beneath a Sapas Mons-sized edifice with axisymmetric geometry. For a range of magma chamber depths and vertical thicknesses, we determine the minimum under pressure that produces a stress state predicting failure in circumferential normal mode at the observed position of the graben system. We also determine maximum under pressure under two conditions: (1) no failure (thrust fault mode) predicted at the summit, and (2) predicted failure (thrust fault mode) limited to within 10 km of the summit. We find that successful models require sill-like chamber geometry with vertical thicknesses <1.5 km (diameter to thickness aspect ratios >66:1), and chamber depth <8 km beneath the summit. Calculated reductions in chamber volume are comparable to volumes of late-stage eruptive units mapped at Sapas Mons, favoring the magma withdrawal hypothesis for graben system formation. Evidence that unit 5 of Keddie and Head (1994, https://doi.org/10.1007/bf00644896) overlapped in time with, but largely postdated, the graben forming event renders it the most likely destination for magma removed from the chamber.
期刊介绍:
The Journal of Geophysical Research Planets is dedicated to the publication of new and original research in the broad field of planetary science. Manuscripts concerning planetary geology, geophysics, geochemistry, atmospheres, and dynamics are appropriate for the journal when they increase knowledge about the processes that affect Solar System objects. Manuscripts concerning other planetary systems, exoplanets or Earth are welcome when presented in a comparative planetology perspective. Studies in the field of astrobiology will be considered when they have immediate consequences for the interpretation of planetary data. JGR: Planets does not publish manuscripts that deal with future missions and instrumentation, nor those that are primarily of an engineering interest. Instrument, calibration or data processing papers may be appropriate for the journal, but only when accompanied by scientific analysis and interpretation that increases understanding of the studied object. A manuscript that describes a new method or technique would be acceptable for JGR: Planets if it contained new and relevant scientific results obtained using the method. Review articles are generally not appropriate for JGR: Planets, but they may be considered if they form an integral part of a special issue.