g eol 2312 i gneous and m etamorphic p etrology lecture 14 continental flood basalts with special...
TRANSCRIPT
GEOL 2312 IGNEOUS AND METAMORPHIC PETROLOGY
Lecture 14
Continental Flood Basalts
with special emphasis on the
Midcontinent Rift
February 25, 2009
LARGE IGNEOUS PROVINCESIMPACT SITES OF STARTING MANTLE
PLUMES
http://www.largeigneousprovinces.org
CONTINENTAL FLOOD BASALTSLARGE IGNEOUS PROVINCES IN CONTINENTAL SETTINGS
Winter (2001) Figure 15-1. Columbia River Basalts at Hat Point, Snake River area. Cover of Geol. Soc. Amer Special Paper 239. Photo courtesy Steve Reidel.
Table 15-1. Major Flood Basalt Provinces
Name Volume Age Locality
CRB (1.7x105 km3) Miocene NW US
Keeweenawan (4x105 km3) Precambrian Superior area
Deccan (106 km3) Cret.-Eocene India
Parana (area > 106 km2) early Cret. Brazil
Karroo (2x106 km3?) early Jurassic S. Africa
MAFIC DIKE SWARMSVESTIGES OF ANCIENT CONTINENTAL FLOOD
BASALTS
THE BREAK-UP OF GONDWANALAND
PARANA/KAROO/FERRAR/DECCAN
Ferrar
COLUMBIA RIVER BASALTS, SNAKE RIVER PLAIN BASALTS AND THE YELLOWSTONE PLUME
An Aborted, Mantle Plume-influenced, Intracontinental Rift (1110-1086 Ma)
The Midcontinent Rift
A. Rift Magmatism
Gabbro
MantlePlume
BasaltFlows
CrustMantle
B. Sediment Infilling Sandstone
C. Compression
1,115-1,086 Ma1,115-1,086 Ma
1,090-1,080Ma1,090-1,080Ma
1,080-1,040 Ma1,080-1,040 Ma
Main Evolutionary Stages of the Midcontinent Rift
Rifting and Plume-influenced Magmatism
Subsidence and Sedimentation
Compression and Rift Inversion
EVIDENCE FOR A STARTING MANTLE EVIDENCE FOR A STARTING MANTLE PLUMEPLUME Large Volume of Volcanic Fill (>1,500,000 kmLarge Volume of Volcanic Fill (>1,500,000 km33; Cannon, ; Cannon,
1992)1992) Extensive Intrusive Underplating (gravity modelling) Extensive Intrusive Underplating (gravity modelling) Potential Temperature of Source ~250Potential Temperature of Source ~250ooC > Normal C > Normal
Mantle (Hutchinson et al., 1990)Mantle (Hutchinson et al., 1990) Isotope Geochemistry Indicative of Enriched Mantle Isotope Geochemistry Indicative of Enriched Mantle
Source (Nicholson & Shirey, 1997)Source (Nicholson & Shirey, 1997) Evidence of Thermal Doming (subaerial basalts, early Evidence of Thermal Doming (subaerial basalts, early
volcanic-less intrusions)volcanic-less intrusions) Rapid Rates of Effusion (avg. ~0.15 km3/y; Cannon, Rapid Rates of Effusion (avg. ~0.15 km3/y; Cannon,
1992, Davis and Paces, 1990)1992, Davis and Paces, 1990) Radial Orientation of Dike Swarms in the Lake Superior Radial Orientation of Dike Swarms in the Lake Superior
Region (Green et al., 1987)Region (Green et al., 1987) Migration of Magmatism from East to West (eastward Migration of Magmatism from East to West (eastward
plate drift over fixed plume?)plate drift over fixed plume?)
Inconsistencies with a Mantle PlumeInconsistencies with a Mantle Plume Prolonged magmatism (>23 Ma)Prolonged magmatism (>23 Ma) Peak of volcanic activity at midpoint of magmatic Peak of volcanic activity at midpoint of magmatic
interval?interval?
Lutgens and Tarbuck, 2003
Midcontinent Rift MagmatismMidcontinent Rift Magmatism1115-1086 Ma1115-1086 Ma
Role of the Grenville
Midcontinent Rift InversionMidcontinent Rift Inversion~1080-1040 Ma*~1080-1040 Ma*
Rivers, 2008 (Fig. 3)
Rivers, 2008 (Fig. 1)
*Cannon, 1994
R
Exposed Exposed Geology of the Geology of the Midcontinent Midcontinent Rift in the Lake Rift in the Lake Superior Superior RegionRegion
Compilation by Green (2005)
LateLate
MainMainLatentLatentEarlyEarlyUplift?Uplift?
?
- ?
Geochronology of the Midcontinent Rift
Magmatic StagesMagmatic StagesMiller and Vervoort (1996), Nicholson et al. (1997)
Chemostratigraphic data mostly from Green (1986), Klewin & Berg (1991), Lightfoot et al. (1991), Shirey et al. (1994), Nicholson et al.(1997), Vervoort & Green (1997).
Halls (1982)
Evidence for Crustal Underplating
Modified from Thomas & Teskey (1994), Fig. 14; Includes interpretations of Trehu et al., (1991)
GLIMPCE Line A
Origin of Origin of Felsic Magmas Felsic Magmas Partial Melting of the Lower Crust
Origin of Origin of Anorthositic RocksAnorthositic RocksPlagioclase Flotation in the Lower Crust
Based on Kushiro (1980)
From Miller & Vervoort (1996)