Transcript A Consequence of Mantle Plume Magmatism

Tectonomagmatic Evolution of the
Midcontinent Rift
North America
(Laurentia)
at 1.1 Ga
Continental
RiftingThe creation of
ocean basins
Mantle
Plumes and
Flood
Basalts
Magmatic Underplating
of the Crust
A Consequence of Mantle
Plume Magmatism
LIPs-Large Igneous Provinces
Simple Tectonic
Model for the
MCR
Evidence of a Starting Mantle Plume
• Rapid early rates of
volcanism
• Large total volume
of mafic
magmatism (> 20
km volcanic edifice
in central axis of
rift)
• εNd of mafic rocks
= 0 to slightly +
Main Igneous
Units of the
MCR
Nipigon
Sills
Coldwell
Complex
Logan
Sills
Osler Group
Duluth
Complex
Isle Royale Fault
Beaver Bay
Complex
Michipichoten
Island
Volcanics
Portage Lake volcanics
Mamainse Pt Volcanics
Mellen
Complex Powdermill Group
Chengwatana volcanics
Geophysical
Evidence of
Underplating
Lo-P
Hi-P
Differentiated
Basalts of the NSVG
Primitive Ol Tholeiite
Geochronology of
the MCR
Hoaglund (2010)
Proposed Tectonomagmatic Model
for the Midcontinent Rift
Why Didn’t the MCR
Evolve to an Ocean Basin?
- Dissipation of the Plume
- Resurgence of Grenville Compression