Precambrian Geology of the Lake Superior Region

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Precambrian Geology of the Lake Superior
Region THE MAKING OF LAURENTIA Jim
Miller University of Minnesota Duluth
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The Geologic Record in Minnesota
LAURENTIA
KENORALAND
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Precambrian Geology of Minnesota
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Direct Evidence OUTCROP
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More Direct Evidence DRILL CORE
Image from Dale Setterholm, MGS
Location of core hole
Drill core
Drill hole locations provided by Minnesota
Department of Natural Resources, Division of
Lands and Minerals, Hibbing 2002
1st vertical derivative of aeromagnetic data
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Indirect Evidence GEOPHYSICAL DATA
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Supporting Evidence GEOCHRONOLOGY AND
GEOCHEMISTRY
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Geologic Paradigms and Principles
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Terrane 1 The Minnesota River Valley Gneiss
Terrane gt3.0 Ga
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THE MINNESOTA RIVER VALLEY
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GRANITIC GNEISS Early Continent Formation
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Geochronology of the MRV
Benson block
3,500 Primary crystallization of both
gneisses 3370-3385 Granodiorite intrusions
3300-3050 Metamorphic event 3140-3080 Mafic
intrusions in Montevideo Gneiss
metamorphic event 2620-2590 Granite intrusions
(Sacred Heart and Ortonville), deformation,
metamorphism, and shearing and
mafic intrusions along YMSZ
Montevideo block
YMSZ
Morton block
Dates from Bickford et al., 2006 and Schmitz et
al., 2006
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Terrane 2 The Superior Province
(Granite- Greenstone Terrane) 2.7-2.5 Ga
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GREENSTONE Metamorphosed Basalt Pillowed
Structures indicative of submarine eruption
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SEDIMENTARY ROCKS
BANDED IRON FORMATION
GRAYWACKE
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GRANITE BATHOLITHS Partially-melted Crust
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( 2.6 Ga)
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The Superior Province Multiple Accreted Terranes
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TECTONIC MODEL FOR THE SUPERIOR
PROVINCE Accretion of Island Arcs, Oceanic
Plateaus, and Protocontinents
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SUPERIOR PROVINCE A major episode of continental
growth creating KENORALAND, the core of North
America
Kenoraland
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Terrane 3 The Penokean (and Yavapi and
Mazatzal) Orogen 1.9-1.6 Ga Making Laurentia
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Prelude to the Penokean2060-80 Ma Rifting of
Kenoraland and Formation of the Animikie Sea and
the Becker Embayment
(Holm et al., 2008)
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Paleoproterozoic Sedimentary Rocks of the Lake
Superior Region
Animikie Group Menominee Group Huronian
Supergroup Archean
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Huronian Supergroup Sedimentary Rocks
TILLITES
U-bearing Matinenda Fm
Carbonates of the Espanola Fm
Gowganda Fm
Ramsey Lake Fm
Bruce Fm
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(No Transcript)
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MESABI-TYPE IRON FORMATION Geologic Marker of a
Major Evolutionary Event
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STROMATOLITES (Fossilized Algal Mats) A Key to
the Origin of Mesabi-type Iron Formation
Mary Ellen Mine
LTV Mine
Shark Bay, Australia
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(No Transcript)
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The 1.875 Ga Sudbury Impact The First Major
Extinction Event ??
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Penokean Orogeny 1.85 Ga
Thomson Dam
Eveleth
St. Cloud
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(No Transcript)
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Penokean Mountains (1.85 -1.75 Ga)
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The Amazing Shrinking Penokean
(From Holm et al., 2008)
NICE (Northern Interior Continental Evolution)
Working Group R. Anderson, T. Boerboom,W.
Cannon, V. Chandler, D. Holm, M. Jirsa, J.
Miller, D. Schneider, K. Schulz, W.R. Van Schmus,
and L. Woodruff.
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DENUDATION OF A MOUNTAIN BELT
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SIOUX QUARTZITE and Related 1.7 Ga Mature
Sandstones
Flambeau
Rib Mtn
Sioux
Baraboo
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Tectonic Evolution of Paleoproterozoic
Terranes- Growing Laurentia
From Holm et al. (2008)
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GRENVILLE OROGENY 1150-950 Ma Adding Laurentia to
the Supercontinent Rodinia
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Terrane 4 The Midcontinent Rift 1.1 Ga An
Attempt at Unmaking Laurentia
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Initiation of the MCR by the impact of a starting
mantle plume
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MIDCONTINENT RIFT A 1.1 Ga attempt at continental
separation
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(No Transcript)
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Geochronology of Midcontinent Rift Rocks
From Green (2005)
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from Trehu et al., 1994
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BASALT The Rock of Oceanic Crust
NORTH SHORE
Continental Flood Basalts
ICELAND
HAWAII
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(No Transcript)
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Massive Basalt
Amygdaloidal Basalt
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AGATES Gemstone of Minnesota
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Formation of Lake Superior Agates
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AA
BASALT FLOW SURFACES
AA
Pahoehoe
HAWAII
Pahoehoe
NORTH SHORE
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Shovel Point
High Falls on the Baptism River
RHYOLITE The other volcanic rock type
Palisade Head
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(No Transcript)
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GABBROIC ROCKS of the Duluth Complex
Present-day Erosion Surface
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A NEW MINING DISTRICT? The Cu-Ni-PGE Deposits of
the Duluth Complex
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SEDIMENTARY ROCKS of the Midcontinent Rift
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LATE-STAGE FAULTING The Douglas Fault at Amnicon
Falls State Park
Basalt
Fault
Sandstone
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Why isnt Duluth a Sea-side Resort?
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FINALLY, THE STABLE CONTINENTAL INTERIOR OF NORTH
AMERICA
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The Precambrian Research Center at UMD