Chapter 15: Continental Flood Basalts

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Chapter 15 Continental Flood Basalts

• Large Igneous Provinces (LIPs)
• Oceanic plateaus
• Some rifts
• Continental flood basalts (CFBs)

Figure 15-1. Columbia River Basalts at Hat Point,
Snake River area. Cover of Geol. Soc. Amer
Special Paper 239. Photo courtesy Steve Reidel.
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Tectonic Setting of CFBs

• Continental hot spots
• Continental rifting may be associated with hot
  spots
• Successful rifts
• Failed rifts (aulacogens)

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Figure 15-2. Flood basalt provinces of
Gondwanaland prior to break-up and separation.
After Cox (1978) Nature, 274, 47-49.
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Figure 15-3. Relationship of the Etendeka and
Paraná plateau provinces to the Tristan hot spot.
After Wilson (1989), Igneous Petrogenesis. Kluwer.
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Present setting of the Columbia River Basalt
Group in the Northwestern United States. Winter
(2001). An Introduction to Igneous and
Metamorphic Petrology. Prentice Hall.
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Figure 15-5. Time-averaged extrusion rate of CRBG
basalts as a function of time, showing cumulative
volume. After Hooper (1988a) The Columbia River
Basalt. In J. D. Macdougall (ed.), Continental
Flood Basalts. Kluwer. 1-34.
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Figure 15-6. Variation in wt. of selected major
element oxides vs. Mg for units of the Columbia
River Basalt Group. Winter (2001). An
Introduction to Igneous and Metamorphic
Petrology. Prentice Hall. Data from BVTP (Table
1.2.3.3), Hooper (1988a), Hooper and Hawkesworth
(1993).
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Figure 15-7. Condrite-normalized rare earth
element patterns of some typical CRBG samples.
Winter (2001). An Introduction to Igneous and
Metamorphic Petrology. Prentice Hall. Data from
Hooper and Hawkesworth (1993) J. Petrol., 34,
1203-1246.
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Figure 15-8. N-MORB-normalized spider diagram for
some representative analyses from the CRBG.
Winter (2001). An Introduction to Igneous and
Metamorphic Petrology. Prentice Hall. Data from
Hooper and Hawkesworth (1993) J. Petrol., 34,
1203-1246. Picture Gorge from Bailey (1989) Geol.
Soc. Amer. Special Paper, 239, 67-84.
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Figure 15-9. OIB-normalized spider diagram for
some representative CRBG analyses. Winter (2001).
An Introduction to Igneous and Metamorphic
Petrology. Prentice Hall. (data as in Figure
15-8).
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Figure 15-10. Ce/Zr vs. Ce/Nb (unnormalized) for
the basalts of the Columbia River Basalt Group.
After Hooper and Hawkesworth (1993) J. Petrol.,
34, 1203-1246.
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Figure 15-11. 87Sr/86Sr vs. 143Nd/144Nd for the
CRBG. Winter (2001). An Introduction to Igneous
and Metamorphic Petrology. Prentice Hall. Data
from Hooper (1988a), Carlson et al. (1981),
Carlson (1984), McDougall (1976), Brandon et al.
(1993), Hooper and Hawkesworth (1993).
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Figure 15-11. 208Pb/204Pb vs. 206Pb/204Pb for the
basalts of the CRBG. Included for reference are
EMI, EMII, the DUPAL group, the MORB array, and
the NRHL (northern hemisphere reference line)
connecting DM and HIMU mantle reservoirs from
Figure 14-6. Winter (2001). An Introduction to
Igneous and Metamorphic Petrology. Prentice Hall.
Data from Hooper (1988a), Carlson et al. (1981),
Carlson (1984), McDougall (1976), Brandon et al.
(1993), Hooper and Hawkesworth (1993).
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Figure 15-4. Present setting of the Columbia
River Basalt Group in the Northwestern United
States. Winter (2001). An Introduction to Igneous
and Metamorphic Petrology. Prentice Hall. Also
shown is the Snake River Plain (SRP)
basalt-rhyolite province and proposed trace of
the Snake River-Yellowstone hot spot by Geist and
Richards (1993) Geology, 21, 789-792.
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Figure 15-13. A model for the origin of the
Columbia River Basalt Group From Takahahshi et
al. (1998) Earth Planet. Sci. Lett., 162, 63-80.
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Figure 15-14. Diagrammatic cross section
illustrating possible models for the development
of continental flood basalts. DM is the depleted
mantle (MORB source reservoir), and the area
below 660 km depth is the less depleted, or
enriched OIB source reservoir. Winter (20010 An
Introduction to Igneous and Metamorphic
Petrology. Prentice Hall.