Zircon Hf Isotopes and the Continental Evolution of Dronning Maud Land, East Antacrtica

对岩石中单个矿物颗粒的地球化学研究可以用来重建我们星球的历史。矿物锆石（ZrSiO 4）在这方面具有独特的重要性，因为它作为地质时钟的可靠性，这是由于它对风化，运输以及温度和压力变化的强大持久性。锆石颗粒的铀-铅（U-Pb）定年法也许是最常用的方法，用来提取形成大陆地壳的地质过程的时间信息，并已被用来限制大陆和山脉带的演化。此外，锆石中Hf元素的同位素组成被用来确定大陆地壳是由岩浆从下伏地幔中提取而形成的。地幔和陆壳深部岩石的熔融作用是大陆演化的关键过程，它们记录在锆石的Hf同位素特征中。虽然锆石U-Pb定年和Hf同位素分析方法已经成熟，但对锆石的生长过程及其与围岩或岩浆的元素和同位素交换的认识还不够深入。因此，这项研究的重点是揭示地球深处形成的岩石中锆石Hf同位素的演化。的地壳，更具体地说，应用这些同位素方法收集在德龙宁毛德地（DML），东南极洲的岩石。德龙宁毛德地（DML）在超大陆形成过程中占据了中心位置？由今天存在的所有大陆组成的大片陆地-超过5亿年前。目前认为，超级大陆在整个地球上形成和分裂了五到六次。的历史。DML区域是了解最后两个超级大陆形成历史的关键。合并形成这些超级大陆的大陆边界很可能隐藏在DML中。在这项研究中，从DML岩石中回收的锆石颗粒的同位素组成将被用来确定这些边界在整个地区的广泛部分。这些岩石样本是由研究人员在2007年南半球夏季对南极洲进行为期两个月的考察时收集的。2008.不同DML地壳域锆石定年和同位素分析结果将为东南极及其以前向非洲的北方延伸的区域地质提供重要的见解。这对超大陆的重建和在DML中确定大陆边界具有重要意义。

Geochemical studies of single mineral grains in rocks can be probed to reconstruct the history of our planet. The mineral zircon (ZrSiO4) is of unique importance in that respect because of its reliability as a geologic clock due to its strong persistence against weathering, transport and changes in temperature and pressure. Uranium-Lead (U-Pb) dating of zircon grains is, perhaps, the most frequently employed method of extracting time information on geologic processes that shaped the continental crust, and has been used to constrain the evolution of continents and mountain belts through time. In addition, the isotopic composition of the element Hafnium (Hf) in zircon is used to date when the continental crust was generated by extraction of magma from the underlying mantle. Melting of rocks in the mantle and deep in the continental crust are key processes in the evolution of the continents, and they are recorded in the Hf isotopic signatures of zircon. Although the analytical procedures for U-Pb dating and Hf isotope analyses of zircon are robust now, our understanding of zircon growth and its exchange of elements and isotopes with its surrounding rock or magma are still underdeveloped. The focus of the proposed study, therefore, is to unravel the evolution of zircon Hf isotopes in rocks that were formed deep in the Earth?s crust, and more specifically, to apply these isotopic methods to rocks collected in Dronning Maud Land (DML), East Antarctica. Dronning Maud Land (DML) occupied a central location during the formation of supercontinents ? large landmasses made up of all the continents that exist today - more than 500 million years ago. It is currently thought that supercontinents were formed and dismembered five or six times throughout Earth?s history. The area of DML is key for understanding the formation history of the last two supercontinents. The boundaries of continents that were merged to form those supercontinents are most likely hidden in DML. In this study, the isotopic composition of zircon grains recovered from DML rocks will be employed to identify these boundaries across an extensive section through the area. The rock samples were collected by the investigator during a two-month expedition to Antarctica in the austral summer of 2007?2008. The results of dating and isotope analyses of zircon of the different DML crustal domains will deliver significant insight into the regional geology of East Antarctica and its previous northern extension into Africa. This has significance for the reconstruction of the supercontinents and defining the continental boundaries in DML.