Late Cretaceous to early Tertiary subduction history of the Antarctic Peninsula
Late Cretaceous to early Tertiary subduction history of the Antarctic Peninsula
复制标题
南极半岛晚白垩世至早第三纪俯冲历史
DOI：
10.1144/gsjgs.155.2.0255
复制
发表时间：
1998
影响因子：
2.7
通讯作者：
R. Larter
中科院分区：
文献类型：
--
作者：
J. J. McCarron;R. Larter
根据晚白垩世和早第三纪（83.0 ~ 67.7 Ma和61.1 ~ 53.4 Ma）两个时期的板块旋转计算，对凤凰板块与南极半岛的辐合速率和方位角进行了定量估计。已发表的海洋磁异常识别和重力异常图解释的“流动线”用于简单的球面几何计算，以获得凤凰-太平洋阶段的旋转。这些数据与已公布的太平洋-南极旋转数据相结合，以确定同期凤凰-南极阶段的旋转。结果表明，晚白垩世和早第三纪之间相对运动方位角发生了显著变化。晚白垩世或更早的斜向俯冲作用可能导致弧前碎屑岩沿边缘迁移，导致增生棱柱宽度的变化。将合成磁剖面与早第三纪在南极-凤凰脊产生的横跨海底的900公里长的磁剖面进行比较，确定了扩散速率主要下降的时间，因此也确定了收敛速率，如C23r （52.3 Ma）。俯冲动力学的相关变化可能导致了乔治六世海湾地区观测到的右旋张拉变形，并引发了史密斯岛目前暴露的蓝片岩相岩石的隆升。计算的辐合历史并不能简单地解释亚历山大岛上高镁安山岩熔岩的发生，这些熔岩是在南极-凤凰脊到达边缘之前20多Ma喷发的。这些熔岩的存在表明，要么是另一个山脊的早期俯冲，要么是亚历山大岛下面的板块断裂。
Quantitative estimates of the rates and azimuths of Phoenix plate convergence with the Antarctic Peninsula have been derived from plate rotation calculations for two periods in the Late Cretaceous and early Tertiary (83.0–67.7 and 61.1–53.4 Ma). Published marine magnetic anomaly identifications and ‘flow lines’ interpreted from gravity anomaly maps were used in simple spherical geometry calculations to derive Phoenix–Pacific stage rotations. These were combined with published Pacific–Antarctic rotation data to determine contemporaneous Phoenix–Antarctic stage rotations. The results indicate a significant change in azimuths of relative motion between the Late Cretaceous and early Tertiary. Late Cretaceous, and perhaps earlier, oblique subduction probably caused migration of fore-arc slivers along the margin, resulting in variations in width of the accretionary prism. Comparison between synthetic magnetic profiles and a 900 km long magnetic profile across ocean floor produced at the Antarctic–Phoenix ridge during the early Tertiary establishes the time of a major decrease in spreading rate, and hence also in convergence rate, as chron C23r (52.3 Ma). The associated change in subduction dynamics may have caused the dextral transtensional deformation observed in the George VI Sound region and initiated uplift of blueschist facies rocks now exposed on Smith Island. The calculated convergence history does not provide a simple explanation for the occurrence of high-Mg# andesite lavas on Alexander Island, which were erupted more than 20 Ma before the Antarctic–Phoenix ridge arrived at the margin. The existence of these lavas implies either earlier subduction of another ridge or slab break-up beneath Alexander Island.