Syn-rift volcanism (ca. 670 Ma) in the lower Windermere Supergroup, southern Canadian Cordillera: New constraints on the syn- to post-rift transition for northwestern Laurentia

IF 3.2 2区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Precambrian Research Pub Date : 2024-11-01 DOI:10.1016/j.precamres.2024.107604

Thomas Hadlari , N.M. Rayner , T.P. Poulton , R.W.C. Arnott

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Abstract

The southern Canadian Cordillera is considered the type area for the Windermere Supergroup, where it had long been assumed that the syn-rift basaltic lavas of the Irene Formation were co-genetic with the ca. 720 Ma Franklin LIP. Accordingly, the inferred age of the Irene volcanics is variously cited for either the breakup of Rodinia or for the base of Cryogenian strata in the southern Canadian Cordillera, and yet they have not been directly dated until now. Reported here are geochronological data from a volcanic sample of the Irene Formation yielding a U-Pb SHRIMP zircon age of 669.6 ± 6.7 Ma, which is significantly younger than the presumptive age. The Irene Formation is overlain by basin floor turbidite facies that correlate with the Horsethief Creek Group, which represent some of the oldest post-rift deposits in the study area and are interpreted as the earliest indication of a passive continental margin setting for northwestern Laurentia. The dated sample was collected from the upper portion of the Irene Formation and so the transition from syn-rift to post-rift is younger than ca. 670 Ma, which is estimated at approximately 660–650 Ma. Additionally, these new age data place the associated diamictites at the end of the Sturtian glaciation.

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加拿大科迪勒拉山系南部温德米尔超群下部的同步断裂火山活动（约 670 Ma）：劳伦提亚西北部从同步断裂向后断裂过渡的新制约因素

加拿大科迪勒拉山系南部被认为是温德米尔超群的类型区，长期以来，人们一直认为该地区艾琳地层的同步裂谷玄武岩熔岩与约 720 Ma 的富兰克林大裂谷同源。720 Ma富兰克林LIP。因此，艾琳火山岩的推断年龄被认为是罗迪尼亚断裂或加拿大科迪勒拉山系南部冷元古代地层的基底，但直到现在它们还没有被直接测定。本文报告的是艾琳地层火山岩样本的地质年代数据，其锆石U-Pb SHRIMP年龄为669.6 ± 6.7 Ma，比推测年龄年轻得多。艾琳地层被与马蹄溪组相关的盆地底浊积岩层所覆盖，这些浊积岩层代表了研究区域最古老的裂谷后沉积物，被解释为劳伦提亚西北部被动大陆边缘环境的最早迹象。年代样本取自艾琳地层的上部，因此从同步断裂向后断裂的过渡比约 670 Ma 的年代要早，估计约为 660-650 Ma。此外，这些新的年龄数据将相关的二长岩定位于斯图尔特冰川的末期。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Precambrian Research 地学-地球科学综合

CiteScore

7.20

自引率

28.90%

发文量

325

审稿时长

12 months

期刊介绍： Precambrian Research publishes studies on all aspects of the early stages of the composition, structure and evolution of the Earth and its planetary neighbours. With a focus on process-oriented and comparative studies, it covers, but is not restricted to, subjects such as: (1) Chemical, biological, biochemical and cosmochemical evolution; the origin of life; the evolution of the oceans and atmosphere; the early fossil record; palaeobiology; (2) Geochronology and isotope and elemental geochemistry; (3) Precambrian mineral deposits; (4) Geophysical aspects of the early Earth and Precambrian terrains; (5) Nature, formation and evolution of the Precambrian lithosphere and mantle including magmatic, depositional, metamorphic and tectonic processes. In addition, the editors particularly welcome integrated process-oriented studies that involve a combination of the above fields and comparative studies that demonstrate the effect of Precambrian evolution on Phanerozoic earth system processes. Regional and localised studies of Precambrian phenomena are considered appropriate only when the detail and quality allow illustration of a wider process, or when significant gaps in basic knowledge of a particular area can be filled.