Upper-crustal cooling of the Wrangellia composite terrane in the northern St. Elias Mountains, western Canada
Upper-crustal cooling of the Wrangellia composite terrane in the northern St. Elias Mountains, western Canada
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DOI：
10.1130/l508.1
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发表时间：
2016-08-01
期刊：
影响因子：
2.4
通讯作者：
Enkelmann, Eva
中科院分区：
文献类型：
--
作者：
Falkowski, Sarah;Enkelmann, Eva
本研究提出了长期的挖掘历史的Wrangellia复合化石的偏远和冰雪覆盖的北方圣埃利亚斯山脉西南部育空地区，西北部不列颠哥伦比亚省，和邻近的阿拉斯加。给出了21个冰川流域碎屑锆石和磷灰石裂变径迹年龄分布。碎屑取样方法可用于大的空间覆盖范围（类似于30，000公里（2）），并可获取冰下侵蚀的物质。另外五个基岩样品的锆石裂变径迹分析与碎屑结果进行比较。我们新的热年代学数据记录了晚侏罗世-白垩纪中期的Wrangellia复合碎屑岩与前北美边缘的增生和岩浆活动，这重置了较旧的热记录。侏罗纪-白垩纪记录的良好保存表明新生代的侵蚀一定总体上是有限的。尽管如此，始新世扩展脊俯冲和渐新世-新近纪冷却在响应正在进行的雅库特平板俯冲是显而易见的，在研究区，尽管其内侧位置从活跃的板块边界。结果进一步表明，费尔韦瑟断层的北方末端有一个快速挖掘的区域。10-5这一区域由离散的、未映射的结构所限定。5 Ma后，快速折返区向西南方向板块边界和圣埃利亚斯结合带中心移动。整合新的数据与发表的碎屑热年代学从南部圣埃利亚斯山脉揭示了一个不断变化的变形和折返的浓度，可能在一个大规模的，transpressive结构提供了重要的制约因素的地质动力学模型的syntaxes。
This study presents the long-term exhumation history of the Wrangellia composite terrane of the remote and ice-covered northern St. Elias Mountains in southwest Yukon, northwest British Columbia, and adjacent Alaska. Detrital zircon and apatite fission-track age distributions are presented from 21 glacial catchments. The detrital sampling approach allows for a large spatial coverage (similar to 30,000 km(2)) and access to material eroded beneath the ice. An additional five bedrock samples were dated by zircon fission-track analysis for a comparison with detrital results. Our new thermochronology data record the Late Jurassic-mid-Cretaceous accretion of the Wrangellia composite terrane to the former North American margin and magmatism, which reset the older thermal record. The good preservation of the Jurassic-Cretaceous record suggests that Cenozoic erosion must have been limited overall. Nonetheless, Eocene spreading-ridge subduction and Oligocene-Neogene cooling in response to the ongoing Yakutat flat-slab subduction are evident in the study area despite its inboard position from the active plate boundary. The results further indicate an area of rapid exhumation at the northern end of the Fairweather fault ca. 10-5 Ma; this area is bounded by discrete, unmapped structures. The area of rapid exhumation shifted southwest toward the plate boundary and the center of the St. Elias syntaxis after 5 Ma. Integrating the new data with published detrital thermochronology from the southern St. Elias Mountains reveals an evolving concentration of deformation and exhumation, possibly within a large-scale, transpressional structure providing important constraints for geodynamic models of syntaxes.