Geochronology of Mesozoic tholeiitic magmatism in Antarctica: implications for the development of the failed Weddell Sea rift system
Geochronology of Mesozoic tholeiitic magmatism in Antarctica: implications for the development of the failed Weddell Sea rift system
复制标题
南极洲中生代拉斑斑岩岩浆作用的年代学：对失败的威德尔海裂谷系统发展的影响
DOI：
10.1144/gsl.sp.1996.108.01.04
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
C. Hawkesworth
中科院分区：
文献类型：
--
作者：
T. Brewer;D. Rex;P. Guise;C. Hawkesworth
摘要南极中生代拉斑玄武岩岩浆岩曾被划分为费拉尔岩浆区和德龙宁毛德地岩浆区。在这两个省，K-Ar地质年代学建立了一个光谱的侏罗纪时代，支持相对长寿的同生期岩浆事件在每个省。然而，最近的Ar-Ar年代学研究表明，Ferrar岩浆活动发生在一个很短的时间间隔（176.6 ± 1.8 Ma）。为了进一步确定两个省的年龄关系，新的Ar-Ar年代学研究得出了三个不同地区的如下年龄：（德龙宁毛德地）玄武岩172.4 ± 2.1Ma，粗玄岩182.1 ± 1.9Ma; Theron山（Coats Land）的10个辉长岩年龄为172.6 ± 1.7 ~ 181.9 ± 2.5Ma，而两个低K斜长石的辉长岩年龄为c. Dufek侵入体（横贯南极山脉）182.5 ± 2.4Ma。Dufek侵入体是一个非常大的层状辉长岩杂岩，它是Ferrar岩浆区的一个组成部分，但比该省的玄武岩稍老;这表明早期的侵入幕，随后是稍晚的火山幕。在NE Heimefrontfjella也发现了类似的年龄分布。新的Ar-Ar年龄证实了南极洲内一个短暂但广泛的中侏罗世岩浆幕。这一岩浆幕是C。比非洲和南极洲分离的最早证据早25 Ma，这表明导致德龙宁毛德地和南部非洲卡鲁省岩浆活动的地幔柱不是大陆分离的驱动力。然而，南极洲德龙宁毛德地和科茨地的岩浆活动以及羽流的假定位置与失败的威德尔海裂谷系的位置相关。地幔柱可能为这个裂谷系统提供了驱动力，但是，它没有足够的能量来驱动大陆分离。
Abstract In Antarctica, Mesozoic tholeiitic magmatic rocks have been divided previously into the Ferrar and Dronning Maud Land magmatic provinces. In both provinces, K-Ar geochronology has established a spectrum of Jurassic ages, which supported relatively long-lived coeval magmatic episodes within each province. However, recent Ar-Ar geochronology has indicated that the Ferrar magmatism occurred over a short interval (176.6 ± 1.8 Ma). To further constrain the age relationships within the two provinces, new Ar-Ar geochronology has yielded the following ages from three different regions: NE Heimefrontfjella (Dronning Maud Land), basaltic lava 172.4 ± 2.1 Ma, dolerite still 182.1 ± 1.9 Ma; 10 dolerites from the Theron Mountains (Coats Land), 172.6 ± 1.7 to 181.9 ± 2.5 Ma, although two dolerites with low K plagioclase gave ages of c. 190 Ma; Dufek Intrusion (Transantarctic Mountains) 182.5 ± 2.4 Ma. The Dufek intrusion is an extremely large layered gabbroic complex, which is an integral part of the Ferrar Magmatic Province, but is slightly older than the basalts in this province; suggesting an early intrusive episode followed by somewhat later volcanic episodes. A similar age distribution has also been demonstrated in NE Heimefrontfjella. The new Ar-Ar ages confirm a short-lived but widespread Mid-Jurassic magmatic episode within Antarctica. This magmatic episode is c. 25 Ma older than the earliest evidence for the separation of Africa and Antarctica, suggesting that the plume responsible for the magmatism in Dronning Maud Land and the Karoo province in southern Africa was not the driving force for continental separation. However, the magmatism in Dronning Maud Land and Coats Land in Antarctica and the postulated position of the plume correlate with the position of the failed Weddell Sea Rift System. The plume may have provided the driving force for this rift system, but, it did not possess sufficient energy to drive continental separation.