Mesozoic Break-up of Gondwanaland: Geochronology of Antarctic Tholeiites

该奖项支持一个研究与冈瓦纳大陆超大陆分裂有关的火成岩的项目。冈瓦纳大陆在中生代的初始分裂与一次大型岩浆活动有关，在这次岩浆活动中形成了大量的喷出熔岩流和侵入岩脉。研究这些与大规模大陆分裂过程有关的火成岩产物，对于限制大陆分裂的时空性质具有重要意义。这种岩浆作用表现在非洲南部的Karoo拉斑岩和南极洲Dronning Maud地的相关岩石，以及横贯南极山脉的Ferrar拉斑岩。将在南极洲两个不同的地区研究岩浆侵入和挤压事件的地质年代学：在Dronning Maud地和在横贯南极山脉的罗斯海地区。前者与分离非洲和南极洲的初始裂谷直接相关，而后者，费拉，与之关系不太直接，但仍然是火成岩活动初始阶段的一部分。研究的目的是：(1)确定该区中生代岩浆活动的侵位时间和持续时间；(2)应用U/Pb锆石定年和40Ar/39Ar定年对费拉群的年代学进行了细化；(3)确定了Dronning Maud地次生矿物记录的Vestfjella熔岩蚀变及其他结晶后事件的时间；(4)评价Dronning Maud地块岩浆活动和蚀变与南部非洲Lebombo单斜以及与Gondwanaland分裂相关的Ferrar群等岩浆活动的可能关系。矿物样品将使用40Ar/39Ar， U-Pb和Rb-Sr方法来确定事件的年代。这些矿物包括：原生火成岩相（长石、黑云母、锆石），它们将成为确定岩浆事件时间的重点；其次是次生相（斑岩、层状硅酸盐），以确定蚀变事件的时间。根据最近相关研究的经验和成功，预期结果不仅对处理该地区的具体问题，而且对构造模型和地质年代学方法具有广泛的意义。结果将解决：冈瓦纳大陆解体；南极洲岩浆活动的时空关系；洪水玄武岩省形成的构造模式地质年代学方法的应用，特别是蚀变基性火成岩的应用。

Elliot and Foland OPP 9527816 Abstract This award supports a project to investigate igneous rocks associated with the break-up of the Gondwanaland supercontinent. The initial break-up of Gondwanaland during the Mesozoic was associated with a major magmatic event during which voluminous extrusive lava flows and intrusive sills and dikes were formed. Study of these igneous products which are related to large-scale processes of continental disruption is important in constraining the temporal and spatial nature of break-up. This magmatism is expressed by the Karoo tholeiites of southern Africa and related rocks in Dronning Maud Land, Antarctica, and by Ferrar tholeiites of the Transantarctic Mountains. The geochronology of mafic igneous intrusive and extrusive events will be examined in Antarctica in two distinct areas: in Dronning Maud Land and in the Ross Sea sector of the Transantarctic Mountains. The former is directly associated with the initial rifting which separated Africa from Antarctica while the latter, the Ferrar, has a less direct relationship but nevertheless is part of the initial phase of igneous activity. The objectives of the research are to: (1) establish the time of emplacement and duration of the Mesozoic magmatism in Dronning Maud Land; (2) refine the geochronology of the Ferrar Group with the application of U/Pb zircon dating as well as 40Ar/39Ar dating; (3) establish the timing of alteration of the Vestfjella lavas and other post-crystallization events recorded by secondary minerals in Dronning Maud Land; and (4) evaluate possible relationships of Dronning Maud Land magmatism and alteration to the Lebombo Monocline in southern Africa and to the Ferrar Group and other magmatism associated with Gondwanaland break-up. Mineral samples will be used to date the events using the 40Ar/39Ar, U-Pb, and Rb-Sr methods. The minerals include: primary igneous phases (feldspar, biotite, zircon) that will be the focus for establishing timing of ma gmatic events; and, secondary phases (apophyllite, phyllosilicate) to address timing of alteration events. Based upon recent experience and success in related studies, the results are expected to have broad implications not only for specific questions dealing with the region but also for tectonic models and geochronologic methods. The results will address: Gondwanaland break-up; spatial and temporal relations of magmatism in Antarctica; tectonic models for the generation of flood basalt provinces; and, application of geochronologic methods, especially to altered basic igneous rocks.