The document summarizes continental flood basalts (CFBs), which are large igneous provinces that form extensive basaltic lava flows on continents. It discusses the Columbia River Basalt Group as a classic example of CFBs. CFBs are often associated with continental hotspots or rifting, and form from massive eruptions of basaltic magma over short periods of time. The Columbia River Basalt Group originated from a hotspot located in present-day Washington State around 16-17 million years ago, erupting over 1.5 million cubic km of basaltic lava in a series of flows.

1. Chapter 15: Continental Flood Basalts
Large Igneous Provinces (LIPs)
 Oceanic plateaus
 Some rifts
 Continental flood basalts
(CFBs)
Figure 15.2. 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 Approximate Volume Age Locality
CRB (1.7x105
km3
) Miocene NW US
Keeweenawan (4x105
km3
) Precambrian Superior area
Deccan (8.6 x 106
km3
) Cret.-Eocene India
Parana (area > 106
km2
) early Cret. Brazil
Karroo (2x106
km3
?) early Jurassic S. Africa
Siberian (3-5 x 106
km3
) l. Permian - e. Triassic Siberia

2. Large Igneous Provinces (LIPs)
Figure 15.1. Map of the major large igneous provinces (LIPs) on Earth, including continental flood basalt
provinces, volcanic passive margins, oceanic plateaus, aseismic submarine ridges, ocean basin flood basalts,
and seamount groups. After Saunders et al. (1992) and Saunders (pers. comm.).

3. Tectonic Setting of CFBs
 Continental hot spots
 Continental rifting may be associated with hot
spots
 Successful rifts
 Failed rifts (aulacogens)

4. Figure 15.3. Flood basalt provinces of Gondwanaland prior to break-up and
separation. After Cox (1978) Nature, 274, 47-49.

5. Figure 15-4. Relationship of the Etendeka and Paraná plateau provinces to the
Tristan hot spot. After Wilson (1989), Igneous Petrogenesis. Kluwer.

6. Figure 15.5 Setting of the Columbia River Basalt Group in the Northwestern United States. Pink star is the location proposed by Camp and
Ross (2004) of the 16.6 Ma outbreak of the plume and plume-related basaltic volcanism. Yellow star is the location of the deep plume conduit
proposed by Jordan et al. (2004). Blue areas are Quaternary basalts and pink areas are rhyolite centers. Heavy dashed curves represent the
progressive younging of rhyolitic centers (with ages in Ma). Those on the east represent the proposed Yellowstone hotspot track (heavy arrow).
Those on the west are the opposing westward track leading to Newberry Volcano (N) with ages reported by Jordan et al. (2004). After Camp
and Ross (2004).

7. Figure 15.5 (continued). The cross-section is diagrammatic, generally across southern Oregon and Idaho (south of the main CRBG) and
illustrates the westward deflection of the plume head by the deep keel of the North American craton to beneath the thinner accreted terranes
and the migration of the hotspot tracks both east and west. After Jordan et al. (2004) © AGU with permission.

8. Sub- Magnetic K/Ar
group Polarity* Dates
Lower Monumental N 6 Ma
Ice Harbor N,R 8.5
Saddle Buford R
Elephant Mountain R,T 10.5
Mountains Pomona R 12
Esquatzel N
Basalt Weissenfels Ridge N
Asotin N 13
Wilbur Creek N
Umatilla N
Priest Rapids R 14.5
Wanapum Roza T,R
Basalt Frenchman Springs N
Eckler Mountain N
Grande See Reidel et al . N2 15.0
Ronde Picture (1989) for R2
Basalt Gorge Grande N1
Ronde Units R1
R1
Imnaha T
Basalt N0
R0 16.5
Lower Steens R0 !6.6
* N = normal, R = reversed, T = transitional
Formation Member
Clarkston
See Hooper et al .
(1984) for Imnaha Units
Data from Reidel et al . (1989); Hooper and Hawkesworth (1993),
Hooper(1997), Hooper et al. (2008).
Table 15.2. Stratigraphy of the Columbia River Basalt Group.

9. Figure 15.6. 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.

10. Figure 15.7 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).

11. Figure 15.8. 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.

12. Figure 15.9. 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.

13. Figure 15.10 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).

14. Figure 15.11. Ce/Zr vs. Ce/Nb (un-normalized) for the basalts of the Columbia River Basalt Group. After
Hooper and Hawkesworth (1993) J. Petrol., 34, 1203-1246.

15. Figure 15.12. 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).

16. Figure 15.13. 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).

17. Figure 15.14. A model for the origin of the Columbia River Basalt Group From Takahahshi et al. (1998) Earth Planet. Sci. Lett.,
162, 63-80.

18. Figure 15.15. 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.

19. Figure 15.6 Dewey and Burke model for the evolution of a continental rift by the concatenation of a series of 3-rift triple junctions, each
centered on a hotspot. Two arms of each hotspot link up to adjacent hotspots, although generally not perfectly. The third arm fails and becomes a
rift valley (aulacogen). The hotspots need not be coeval and different segments can form sequentially. From Dewey and Burke (1974)