Nicholas L. Swanson-Hysell
Mark D. Schmitz
James D. Miller
Margaret Susan Avery
Yiming Zhang
2021
<div class="article-section__content en main"><p>New geochronologic and paleomagnetic data from the North American Midcontinent Rift (MCR) reveal the synchronous emplacement of the Beaver River diabase, the anorthosite xenoliths within it, and the Greenstone Flow—one of the largest lava flows on Earth. A U-Pb zircon date of 1091.83 <img class="section_image" src="https://agupubs.onlinelibrary.wiley.com/cms/asset/835cc8ce-e5a1-4954-a6d6-c7b578c5e17c/ggge22632-math-0001.png" alt="urn:x-wiley:15252027:media:ggge22632:ggge22632-math-0001" data-mce-src="https://agupubs.onlinelibrary.wiley.com/cms/asset/835cc8ce-e5a1-4954-a6d6-c7b578c5e17c/ggge22632-math-0001.png"> 0.21 Ma (2<img class="section_image" src="https://agupubs.onlinelibrary.wiley.com/cms/asset/bb4c3fab-e424-4fdd-bd15-29863639a746/ggge22632-math-0002.png" alt="urn:x-wiley:15252027:media:ggge22632:ggge22632-math-0002" data-mce-src="https://agupubs.onlinelibrary.wiley.com/cms/asset/bb4c3fab-e424-4fdd-bd15-29863639a746/ggge22632-math-0002.png">) from one of the anorthosite xenoliths is consistent with the anorthosite cumulate forming as part of the MCR and provides a maximum age constraint for the Beaver River diabase. Paired with the minimum age constraint of a cross-cutting Silver Bay intrusion (1091.61 <img class="section_image" src="https://agupubs.onlinelibrary.wiley.com/cms/asset/b05c5aa4-956f-453e-ba10-381b109e0133/ggge22632-math-0003.png" alt="urn:x-wiley:15252027:media:ggge22632:ggge22632-math-0003" data-mce-src="https://agupubs.onlinelibrary.wiley.com/cms/asset/b05c5aa4-956f-453e-ba10-381b109e0133/ggge22632-math-0003.png"> 0.14 Ma; 2<img class="section_image" src="https://agupubs.onlinelibrary.wiley.com/cms/asset/74d8c674-e7c9-491f-8561-e29a40e5ad6a/ggge22632-math-0004.png" alt="urn:x-wiley:15252027:media:ggge22632:ggge22632-math-0004" data-mce-src="https://agupubs.onlinelibrary.wiley.com/cms/asset/74d8c674-e7c9-491f-8561-e29a40e5ad6a/ggge22632-math-0004.png">), these data tightly bracket the age of the Beaver River diabase to be 1091.7 <img class="section_image" src="https://agupubs.onlinelibrary.wiley.com/cms/asset/bfd7167e-2210-44f4-b9da-85fc7b8ffc11/ggge22632-math-0005.png" alt="urn:x-wiley:15252027:media:ggge22632:ggge22632-math-0005" data-mce-src="https://agupubs.onlinelibrary.wiley.com/cms/asset/bfd7167e-2210-44f4-b9da-85fc7b8ffc11/ggge22632-math-0005.png"> 0.2 Ma (95% CI), coeval with the eruption of the Greenstone Flow (1091.59 <img class="section_image" src="https://agupubs.onlinelibrary.wiley.com/cms/asset/58c6a54a-166d-44a3-bb92-1018e100d9ea/ggge22632-math-0006.png" alt="urn:x-wiley:15252027:media:ggge22632:ggge22632-math-0006" data-mce-src="https://agupubs.onlinelibrary.wiley.com/cms/asset/58c6a54a-166d-44a3-bb92-1018e100d9ea/ggge22632-math-0006.png"> 0.27 Ma; 2<img class="section_image" src="https://agupubs.onlinelibrary.wiley.com/cms/asset/d7ad8f69-09ad-43e2-8ce2-a25ebfb23bfc/ggge22632-math-0007.png" alt="urn:x-wiley:15252027:media:ggge22632:ggge22632-math-0007" data-mce-src="https://agupubs.onlinelibrary.wiley.com/cms/asset/d7ad8f69-09ad-43e2-8ce2-a25ebfb23bfc/ggge22632-math-0007.png">)—which is further supported by indistinguishable tilt-corrected paleomagnetic pole positions. Geochronological, paleomagnetic, mineralogical and geochemical data are consistent with a hypothesis that the Beaver River diabase was the feeder system for the Greenstone Flow. The large areal extent of the intrusives and large estimated volume of the volcanics suggest that they represent a rapid and voluminous ca. 1,092 Ma magmatic pulse near the end of the main stage of MCR magmatism.</p></div>
application/pdf
10.1029/2021GC009909
en
American Geophysical Union
Synchronous emplacement of the anorthosite xenolith-bearing Beaver River diabase and one of the largest lava flows on Earth
article