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Late Cretaceous to Paleocene Tectonometamorphic Evolution of the Blanchard River Assemblage, Southwest Yukon: New Insight into the Terminal Accretion of Insular Terranes in the Northern Cordillera
Lithosphere ( IF 2.4 ) Pub Date : 2020-09-21 , DOI: 10.2113/2020/2298288
Lianna Vice 1 , H. Daniel Gibson 1 , Steve Israel 2
Affiliation  

The Intermontane-Insular terrane boundary stretches over 2000 kilometers from British Columbia to Alaska in the western Cordillera. Juxtaposed between these terranes is a series of Jura-Cretaceous basinal and arc assemblages that record a complicated and contested tectonic evolution related to the Mesozoic-Paleocene accretionary history of northwestern North America. In southwest Yukon, west-verging thrust faults facilitated structural stacking of the Yukon-Tanana terrane over these basinal assemblages, including the Early Cretaceous Blanchard River assemblage. These previously undated compressional structures are thought to be related to the final collapse of the Jura-Cretaceous basins and the tectonic burial of the Blanchard River assemblage resulting in amphibolite facies metamorphism. New in situ U-Th-Pb monazite ages record at least three tectonic events: (1) the tectonic burial of the Blanchard River assemblage to amphibolite facies conditions between 83 and 76Ma; (2) peak burial was followed by regional exhumation at ca. 70-68Ma; and (3) intense heating and ca. 63-61Ma low-pressure contact metamorphism attributed to the intrusion of the voluminous Ruby Range suite, which is part of the northern Coast Mountains batholith. The tectonometamorphic evolution recorded in the Blanchard River assemblage can be correlated to tectonism within southwest Yukon and along the length of the Insular-Intermontane boundary from western British Columbia through southwestern Yukon and Alaska. In southwest Yukon, these results suggest an asymmetric final collapse of Jura-Cretaceous basins during the Late Cretaceous, which relates to the terminal accretion of the Insular terranes as they moved northward.

中文翻译:

育空西南部布兰查德河组合晚白垩世至古新世构造变质演化:对北科迪勒拉岛地体末端增生的新见解

Intermontane-Insular terrane 边界从不列颠哥伦比亚省延伸到西科迪勒拉山脉的阿拉斯加超过 2000 公里。并列在这些地体之间的是一系列侏罗纪-白垩纪盆地和弧形组合,它们记录了与北美西北部中生代-古新世增生历史相关的复杂且有争议的构造演化。在育空西南部,向西的逆冲断层促进了育空-塔纳纳地体在这些盆地组合上的构造堆积,包括早白垩世布兰查德河组合。这些先前未注明日期的挤压构造被认为与侏罗-白垩纪盆地的最终坍塌和布兰查德河组合的构造掩埋导致角闪岩相变质有关。新的原位 U-Th-Pb 独居石年龄至少记录了三个构造事件:(1)Blanchard 河组合的构造掩埋到角闪岩相条件在 83-76Ma 之间;(2) 高峰埋葬之后是大约在 2000 年的区域挖掘。70-68Ma;(3) 剧烈加热和大约。63-61Ma 低压接触变质作用归因于大量红宝石山脉套件的侵入,该套件是北部海岸山脉基岩的一部分。在布兰查德河组合中记录的构造变质演化可以与育空地区西南部以及从不列颠哥伦比亚省西部到育空地区西南部和阿拉斯加的岛屿-山间边界沿线的构造活动相关联。在育空西南部,这些结果表明晚白垩世侏罗-白垩纪盆地发生了不对称的最终坍塌,
更新日期:2020-09-21
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