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

这项由极地计划办公室提供的奖励，允许一名美国调查员加入意大利南极计划在南极洲维多利亚地北部的地质实地小组，以研究火山和侵入岩浆岩，这些岩石被认为对详细了解冈瓦纳兰超大陆分裂的初始阶段很重要。在横贯南极山脉的二叠纪和三叠纪沉积序列中，大量玄武岩岩浆在地表喷发，并在深部形成侵入岩和岩脉，标志着冈瓦纳大陆中生代的破裂。这些火山岩主要以静止的玄武岩流的形式在地表喷发，但也有由于地下岩浆/水相互作用而发生的爆炸性喷发。与非洲南部不同的是，南极洲的玄武岩岩浆活动发生在富含硅的爆炸性喷发之前。这些硅质岩石遍布南极横贯山脉。硅质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分裂有关的玄武岩岩浆的运输和扩散。裂谷带记录在比尔德莫尔冰川地区，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。硅质火山碎屑沉积岩的孤立产状，但地层关系尚不清楚；玄武质火山碎屑岩中也含有硅屑，但其来源不详。玄武岩挤压岩在裂谷中的聚集已被推断出来，但没有同生断裂作用的证据。在邻近的深冻岭，假定是侏罗纪裂谷肩的一部分，从基底岩到洪水玄武岩是一个连续的剖面，因此跨越了应该记录硅质岩浆活动的区间。在这段地层中发现的岩石包括三叠纪或中侏罗统的沉积地层、玄武质火山碎屑岩、中侏罗统石英砂岩和玄武质熔岩。深冻山脉为解决北维多利亚地侏罗纪演化中的硅火山作用和构造背景问题提供了机会，并验证了早侏罗世裂陷和相关硅火山作用先于玄武岩岩浆作用并控制冈瓦纳大陆破碎岩浆的搬运和侵位的假设。这项研究的结果有望对理解标志着南极洲分裂初始阶段的硅质和玄武岩岩浆活动的构造环境产生影响。将发育北维多利亚陆的古火山和构造背景。此外，研究结果有望解决费拉尔岩浆的点源和长距离输运模型与局部衍生模型的矛盾。本研究的结果将促进对冈瓦纳大陆破碎过程的理解。

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.