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

这一奖项由极地计划办公室提供，允许一名美国研究员加入意大利南极计划在南极洲维多利亚州北部的地质野外小组，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瓦兰超大陆解体的初始阶段非常重要。冈瓦朗中生代的解体标志着一次重大的岩浆事件，在此期间，大量玄武岩岩浆在地表喷发，并在横贯北极山脉的二叠纪和三叠纪沉积序列中以侵入岩床和深部岩脉的形式侵位。火山岩在地表主要以静止的洪水玄武岩熔岩流动的形式喷发，但也有爆炸，这是地下岩浆/水相互作用的结果。与南部非洲不同的是，南极洲的玄武岩岩浆活动之前发生了一次富含二氧化硅的爆炸性喷发。这些硅质岩被记录在整个横跨北极的山脉中。硅质喷发与地壳伸展和裂谷带的形成有关，裂谷带控制着与超大陆解体有关的玄武岩岩浆的运移和扩散。裂谷带被记录在比尔德莫尔冰川地区，但在维多利亚州，目前的证据是模棱两可的。在维多利亚州北部，没有已知的完整的地层剖面，包括三叠纪地层和上覆的火山单元。沉积岩中有硅质火山碎屑的孤立产出，但其地层关系尚不清楚；玄武岩火山碎屑中也含有硅质碎屑，但其来源不明。已经推断出玄武岩喷出岩在裂谷中的堆积，但没有证据表明同时代的断裂作用。在邻近的深冻山脉，推测为侏罗纪裂谷肩部的一部分，从基岩到溢流玄武岩有一段连续的剖面，因此跨越了硅质岩浆活动的记录区间。报告的岩石包括被认为是三叠纪或中侏罗世的沉积地层、玄武岩火山碎屑岩、中侏罗世石英砂岩和玄武岩熔岩。深冻山脉为解决北维多利亚大陆侏罗纪演化中的硅质火山作用和构造环境问题提供了机会，并验证了早侏罗世裂谷作用和伴生的硅质火山作用先于玄武岩岩浆作用并控制了冈瓦瓦兰德裂解岩浆的运移和侵位的假说。这一研究结果有望对理解标志着南极洲解体初期阶段的硅质和玄武岩岩浆作用的构造环境产生影响。将开发维多利亚州北部的古火山和构造环境。此外，预计结果将解决费拉尔岩浆的点源和长距离运移模型与局部派生模型的问题。这项研究的结果将促进对冈瓦瓦兰崩解过程的理解。

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.