Geochemical, petrographic, and stratigraphic analyses of the Portage Lake Volcanics of the Keweenawan CFBP: implications for the evolution of main stage volcanism in continental flood basalt provinces

William Ray Davis, M. A. Collins, T. O. Rooney, E. L. Brown, C. A. Stein, S. Stein, R. Moucha

Research output: Chapter in Book/Report/Conference proceedingChapter

1 Scopus citations

Abstract

Continental flood basalt provinces (CFBPs) are large igneous features formed by the extrusion of massive amounts of lavas that require significant evolution within the lithosphere. Although sequential lava flows are effective probes of magmatic systems, CFBPs are typically poorly preserved. We focus on lava flows from the well-preserved 1.1 Ga Keweenawan CFBP that erupted within the Midcontinent Rift System. We present a new geochemical, petrographic, and stratigraphic synthesis from the Main stage Portage Lake Volcanics (PLV). Flow-by-flow analysis of the PLV reveals that major element behaviour is decoupled from trace element behaviour; MgO exhibits limited variability, while compatible and incompatible trace elements deviate from high to low concentrations throughout the sequence. The concentrations of incompatible trace elements slightly decrease from the base of the sequence to the top. We investigate these observations by applying a recharge, evacuation, assimilation and fractional crystallization model to geochemical and petrographic data. Our modelling demonstrates a magmatic system experiencing increased evacuation rates while fractionation and assimilation rates decrease, indicating an increase in magmatic flux. The outcome of this modelling is a progressively more efficient magma system within the PLV. This study highlights the utility of joint petrographic and geochemical interpretation in constraining CFBP magma evolution.

Original languageEnglish (US)
Title of host publicationGeological Society Special Publication
PublisherGeological Society of London
Pages67-100
Number of pages34
Edition1
DOIs
StatePublished - 2022

Publication series

NameGeological Society Special Publication
Number1
Volume518
ISSN (Print)0305-8719

ASJC Scopus subject areas

  • Water Science and Technology
  • Ocean Engineering
  • Geology

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