Ferrar Rocks, Deep Freeze Range: Possible Key to Jurassic Evolution of North Victoria Land

费拉尔岩石，深冰区：北维多利亚土地侏罗纪演化的可能关键

• 批准号: 0000185
• 负责人: David Elliot
• 金额: $ 3万
• 依托单位: Ohio State University Research Foundation -DO NOT USE
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-11-15 至 2002-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0000185&HistoricalAwards=false
• 关键词: Ferrar; Rocks; Deep; Freeze; Range

This award, provided by the Office of Polar Programs, allows a US investigator to join an Italian Antarctic Program geological field team in northern Victoria Land, Antarctica, in order to study volcanic and intrusive magmatic rocks that are believed to be important to detailed understanding of the initial phase of breakup of the Gondwanaland supercontinent. Mesozoic break-up of Gondwanaland was marked by a major magmatic event during which voluminous basaltic magmas were both erupted at the surface and emplaced as intrusive sills and dikes at depth within the Permian and Triassic sedimentary sequence of the Transantarctic Mountains. The volcanic rocks were erupted at the surface mainly as quiescent flood basalt lava flows but also explosively, as a result of subsurface magma/water interaction. In contrast to southern Africa, the basaltic magmatism in Antarctica was preceded by an episode of explosive silica-rich eruptions. These silicic rocks are recorded throughout the Transantarctic Mountains. The silicic eruptions were associated with crustal extension and the formation of a rift zone, which then controlled the transport and dispersal of the basaltic magmas associated with supercontinent break-up. The rift zone is documented in the Beardmore Glacier region, but in Victoria Land the current evidence is equivocal.In north Victoria Land no complete stratigraphic section is known that encompasses the Triassic strata and overlying volcanic units. There are isolated occurrences of sedimentary rocks with silicic volcanic debris but their stratigraphic relations are unclear; silicic debris is also incorporated in the basaltic pyroclastic rocks but its source is unknown. The accumulation of basaltic extrusive rocks in a rift has been inferred but without evidence for contemporaneous faulting. In the adjacent Deep Freeze Range, which is postulated to be part of the Jurassic rift shoulder, there is a continuous section from the basement rocks to the flood basalts, thus spanning the interval in which silicic magmatism should be recorded. Rocks reported in this interval include sedimentary strata variously regarded as Triassic or Middle Jurassic, basaltic pyroclastic rocks, and Middle Jurassic quartzose sandstones and basaltic lavas. The Deep Freeze Range offers an opportunity to resolve questions about silicic volcanism and tectonic setting during Jurassic evolution of north Victoria Land and to test the hypothesis that Early Jurassic rifting and associated silicic volcanism preceded basaltic magmatism and controlled the transport and emplacement of Gondwanaland break-up magmas.The results of this study are expected to have implications for understanding the tectonic setting of the silicic and basaltic magmatism that marks the initial stages of break-up in Antarctica. The paleovolcanologic and tectonic setting of north Victoria Land will be developed. In addition, results are anticipated to address the point source and long-distance transport model versus the local derivation model for Ferrar magmas. Understanding of Gondwanaland break-up processes will be advanced by results of this study.

该奖项由极地计划办公室提供，允许一名美国调查员加入意大利南极计划地质实地考察队，在南极洲北方维多利亚地，以研究火山和侵入岩浆岩，据信这对详细了解冈瓦纳超大陆分裂的初始阶段非常重要。中生代冈瓦纳大陆的解体是一个重大的岩浆事件，在此期间，大量的玄武质岩浆在地表喷发，并作为侵入岩床和侵入岩脉在深度内的二叠纪和三叠纪的沉积序列的横贯南极山脉。火山岩在地表喷发，主要是静止的溢流玄武岩熔岩流，但由于地下岩浆/水的相互作用，也有爆炸性的。与南部非洲相反，南极洲的玄武岩岩浆活动之前是一段富含二氧化硅的爆炸性喷发。这些岩石记录在整个横贯南极山脉。火山喷发与地壳伸展和裂谷带的形成有关，裂谷带控制了与超大陆裂解有关的玄武质岩浆的运移和扩散。在比尔德莫尔冰川地区有裂谷带的记载，但在维多利亚地，目前的证据是模棱两可的。在北维多利亚地，没有完整的地层剖面，包括三叠纪地层和上覆的火山单位。有孤立出现的沉积岩与火山碎屑，但它们的地层关系不清楚;玄武岩火山碎屑岩中也有火山碎屑，但其来源不明。有人推测裂谷中有玄武质喷出岩的堆积，但没有同生断层的证据。在邻近的深冻结山脉，这是假定为侏罗纪裂谷肩的一部分，有一个连续的部分，从基岩的溢流玄武岩，从而跨越间隔，在其中应记录的岩浆活动。在这段时间内报告的岩石包括各种认为是三叠纪或中侏罗世的沉积地层，玄武质火山碎屑岩，中侏罗世石英砂岩和玄武质熔岩。深冻岭为解决北维多利亚陆侏罗纪演化过程中的火山作用和构造背景问题提供了一个机会，并为检验早侏罗世裂谷作用和相关的火山作用先于玄武岩浆作用并控制冈瓦纳大陆断裂的搬运和就位的假设提供了一个机会。本研究的结果有望对理解标志着断裂初始阶段的玄武岩浆活动的构造背景产生影响。在南极洲将研究北维多利亚地的古火山和构造背景。此外，预计结果将解决点源和长距离运输模型与当地的推导模型Ferrar岩浆。这一研究结果将促进对冈瓦纳大陆裂解过程的认识。