Revisiting the Australian‐Antarctic Ocean‐Continent Transition Zone Using Petrological and Geophysical Characterization of Exhumed Subcontinental Mantle
Revisiting the Australian‐Antarctic Ocean‐Continent Transition Zone Using Petrological and Geophysical Characterization of Exhumed Subcontinental Mantle
复制标题
利用挖掘出的次大陆地幔的岩石学和地球物理特征重新审视澳大利亚-南极洲海洋-大陆过渡带
DOI：
10.1029/2020gc009040
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发表时间：
2020
期刊：
影响因子：
3.7
通讯作者：
D. Green
中科院分区：
文献类型：
--
作者：
A. McCarthy;T. Falloon;I. Sauermilch;J. Whittaker;K. Niida;D. Green
由于洋陆过渡带（OCT）沿线的基底性质受到稀疏的地质限制，澳大利亚-南极裂谷系统的最终岩石圈破裂仍然存在争议。我们提出了多道地震反射横断面的新解释以及沿南极东部边缘（海山 B，阿德利近海）疏浚地幔岩石的新岩石学数据。通过结合这两个数据集，我们发现沿着贫岩浆的南极边缘挖掘出了一个 50-100 公里宽的寒冷而肥沃的次大陆地幔区域。这项研究仅代表第二个地点，即伊比利亚-纽芬兰边缘，可以清楚地识别沿 OCT 挖掘出的地幔域的重要性。挖出的橄榄岩保留了与澳大利亚边缘东端（维多利亚和塔斯马尼亚）同裂后火山活动中发现的地幔捕虏体相似的特征，表明澳大利亚和南极洲之间裂谷期间肥沃的次大陆地幔被折返。海山 B 代表裂谷期间冷次大陆岩石圈沿 OCT 折返的初始阶段。这个厚的地幔域可能受到高压（8 kbar）熔体浸渍的影响，导致斜长石-辉石岩的形成。大陆裂谷块体、大片贫火山地幔区域和（超）缓慢扩张的组合类似于侏罗纪西特提斯和伊比利亚-纽芬兰裂谷边缘的 OCT。此外，高压熔体停滞的证据表明，沿着澳大利亚-南极裂谷边缘的岩浆活动足以形成磁异常，尽管它们是在成熟、稳态洋壳之外的岩石圈中形成的，但可以用作等时线。
The final lithospheric breakup of the Australian‐Antarctic rift system remains controversial due to sparse geological constraints on the nature of the basement along the ocean‐continent transition (OCT) zones. We present new interpretations of multichannel seismic reflection transects and new petrological data of dredged mantle rocks along the East Antarctic margin (Seamount B, offshore Terre Adélie). By combining both data sets, we show that a 50–100 km wide domain of cold and fertile subcontinental mantle was exhumed along the magma‐poor Antarctic margin. This study represents only the second locality, along with the Iberia‐Newfoundland margins, where the importance of exhumed mantle domains along OCTs can be clearly identified. The dredged peridotites preserve characteristics similar to mantle xenoliths found in syn‐ to post‐rift volcanism at the eastern end of the Australian margin (Victoria and Tasmania), indicating the exhumation of fertile subcontinental mantle during rifting between Australia and Antarctica. Seamount B represents the initial stages of exhumation of cold subcontinental lithosphere along an OCT during rifting. This thick mantle domain was likely affected by melt impregnation at high pressure (8 kbar), leading to the formation of plagioclase‐pyroxenites. The combination of continental rifted blocks, a wide domain of volcanic‐poor subcontinental mantle and (ultra‐) slow spreading is analogous to OCTs from the Jurassic Western Tethys and Iberia‐Newfoundland rifted margins. Additionally, evidence of melt stagnation at high pressure suggests that magmatism along the Australian‐Antarctic rifted margins was sufficient to form magnetic anomalies that can be used as isochrons despite their formation in lithosphere other than mature, steady‐state ocean crust.
影响因子：
3.5
作者：
J. Warren
通讯作者：
J. Warren