Chapter 19: Continental Alkaline
Magmatism
Alkaline rocks occur in all tectonic environments,
including the ocean basins
Conversely, Chapters 12, 15, 17, and 18 have shown
us that magmatism on the continents can be highly
varied, including tholeiitic and calc-alkaline varieties
Now focus on the alkaline rocks that compose an
extremely diverse spectrum of magmas occurring
predominantly in the anorogenic portions of
continental terranes
Chapter 19: Continental Alkaline Magmatism
Alkaline rocks generally have more alkalis than can be
accommodated by feldspars alone. The excess alkalis appear
in feldspathoids, sodic pyroxenes-amphiboles, or other
alkali-rich phases
In the most restricted sense, alkaline rocks are deficient in
SiO2 with respect to Na2O, K2O, and CaO to the extent that
they become “critically undersaturated” in SiO2, and
Nepheline or Acmite appears in the norm
Alternatively, some rocks may be deficient in Al2O3 (and not
necessarily SiO2) so that Al2O3 may not be able to
accommodate the alkalis in normative feldspars. Such rocks
are peralkaline (see Fig. 18-2) and may be either silica
undersaturated or oversaturated
Table 19.1. Nomenclature of some alkaline igneous rocks (mostly volcanic/hypabyssal)
Basanite
feldspathoid-bearing basalt. Usually contains nepheline, but may have leucite + olivine
Tephrite
olivine-free basanite
Leucitite
a volcanic rock that contains leucite + clinopyroxene  olivine. It typically lacks feldspar
Nephelinite a volcanic rock that contains nepheline + clinopyroxene  olivine. It typically lacks feldspar. Fig. 14-2
Urtite
plutonic nepheline-pyroxene (aegirine-augite) rock with over 70% nepheline and no feldspar
Ijolite
plutonic nepheline-pyroxene rock with 30-70% nepheline
Melilitite a predominantly melilite - clinopyroxene volcanic (if > 10% olivine they are called olivine melilitites)
Shoshonite K-rich basalt with K-feldspar ± leucite
Phonolite felsic alkaline volcanic with alkali feldspar + nepheline. See Fig. 14-2. (plutonic = nepheline syenite)
Comendite peralkaline rhyolite with molar (Na2O+K2O)/Al2O3 slightly > 1. May contain Na-pyroxene or amphibole
Pantellerite peralkaline rhyolite with molar (Na2O+K2O)/Al2O3 = 1.6 - 1.8. Contains Na-pyroxene or amphibole
Lamproite a group of peralkaline, volatile-rich, ultrapotassic, volcanic to hypabyssal rocks. The mineralogy is variable,
but most contain phenocrysts of olivine + phlogopite ± leucite ± K-richterite ± clinopyroxene ± sanidine. Table 19-6
Lamprophyre a diverse group of dark, porphyritic, mafic to ultramafic hypabyssal (or occasionally volcanic), commonly
highly potassic (K>Al) rocks. They are normally rich in alkalis, volatiles, Sr, Ba and Ti, with biotite-phlogopite and/or
amphibole phenocrysts. They typically occur as shallow dikes, sills, plugs, or stocks. Table 19-7
Kimberlite a complex group of hybrid volatile-rich (dominantly CO2), potassic, ultramafic rocks with a fine-grained
matrix and macrocrysts of olivine and several of the following: ilmenite, garnet, diopside, phlogopite, enstatite,
chromite. Xenocrysts and xenoliths are also common
Group I kimberlite is typically CO2-rich and less potassic than Group 2 kimberlite
Group II kimberlite (orangeite) is typically H2O-rich and has a mica-rich matrix (also with calcite, diopside, apatite)
Carbonatite an igneous rock composed principally of carbonate (most commonly calcite, ankerite, and/or dolomite), and
often with any of clinopyroxene alkalic amphibole, biotite, apatite, and magnetite. The Ca-Mg-rich carbonatites are
technically not alkaline, but are commonly associated with, and thus included with, the alkaline rocks. Table 19-3
For more details, see Sørensen (1974), Streckeisen (1978), and Woolley et al. (1996)
Chapter 19: Continental Alkaline Magmatism
Figure 19.1. Variations in alkali ratios (wt. %) for oceanic (a) and continental (b) alkaline series. The heavy dashed lines distinguish the
alkaline magma subdivisions from Figure 8-14 and the shaded area represents the range for the more common oceanic intraplate series.
After McBirney (1993). Igneous Petrology (2nd ed.), Jones and Bartlett. Boston. Winter (2001) An Introduction to Igneous and
Metamorphic Petrology. Prentice Hall.
Chapter 19:
Continental Alkaline
Magmatism.
The East African Rift
Figure 19.2. Map of the East African Rift system (after
Kampunzu and Mohr, 1991), Magmatic evolution and
petrogenesis in the East African Rift system. In A. B.
Kampunzu and R. T. Lubala (eds.), Magmatism in
Extensional Settings, the Phanerozoic African Plate.
Springer-Verlag, Berlin, pp. 85-136. Winter (2001) An
Introduction to Igneous and Metamorphic Petrology.
Prentice Hall.
Table 19-2
Oxide
SiO 2
TiO
. Representative Chemical Analyses of East African Rift Volcanics
Series 1: Alkaline
1
2
45.6
51.7
Series 2: Ultra-alkaline
3
4
5
46.2
33.1
44.1
6
55.4
Series 3: Transitional Basalt-Rhyolite
7
8
9
10
47.6
61.8
70.3
72.5
Series 4
11
50.8
2.4
0.9
1.6
2.6
2.8
0.5
2.0
1.0
0.3
0.2
1.4
15.6
11.3
0.2
6.9
10.4
3.2
19.3
5.9
0.2
1.1
4.1
8.9
18.6
8.9
0.2
2.3
7.3
9.3
11.3
12.4
0.3
7.3
17.2
3.2
17.0
10.0
0.2
3.7
8.4
4.3
20.8
4.6
0.2
0.5
2.9
9.2
14.8
11.4
0.2
6.4
11.5
2.7
14.2
6.4
0.3
0.5
1.8
6.2
7.6
8.4
0.3
0.0
0.4
7.3
10.3
4.0
0.1
0.0
0.2
5.9
14.9
10.1
0.2
6.9
9.8
2.6
1.3
4.6
4.2
3.6
7.2
5.5
0.8
5.2
4.3
4.4
0.4
P2 O 5
0.6
Total
97.5
CIPW NORM
q
0.0
or
8.9
ab
31.4
an
28.3
lc
0.0
ne
0.0
di
14.2
hy
0.0
wo
0.0
ol
9.4
il
0.5
tn
4.7
ap
1.6
pf
1.0
ns
0.0
cs
0.0
0.3
97.0
0.5
99.1
1.9
92.9
1.2
98.9
0.1
99.7
0.3
97.7
0.2
97.6
0.0
98.8
97.6
0.4
97.4
0.0
29.8
28.6
0.0
0.0
28.3
6.5
0.0
3.9
0.0
0.5
0.0
0.8
1.3
0.4
0.0
0.0
27.5
8.0
0.0
0.0
39.1
13.7
0.0
5.7
0.0
0.5
0.0
1.3
2.6
1.7
0.0
0.0
0.0
0.0
7.3
20.7
18.2
15.0
0.0
0.0
10.9
0.8
0.0
5.5
4.8
0.0
16.8
0.0
31.0
0.0
6.5
13.2
22.2
16.7
0.0
0.0
1.8
0.5
0.0
3.1
4.9
0.0
0.0
0.0
34.2
30.2
0.0
0.0
27.1
2.8
0.0
4.1
0.0
0.4
0.0
0.2
0.5
0.4
0.0
2.1
5.5
26.5
30.0
0.0
0.0
20.8
8.8
0.0
0.0
0.5
5.0
0.8
0.0
0.0
0.0
9.0
33.7
48.3
0.0
0.0
0.0
2.9
0.0
0.9
0.0
0.7
1.8
0.5
0.0
2.1
0.0
41.7
28.1
16.7
0.0
0.0
0.0
0.1
0.0
0.6
0.0
0.6
0.1
0.1
0.0
12.0
0.0
35.8
27.8
30.4
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.5
0.0
0.0
5.3
0.0
9.1
2.6
25.2
31.9
0.0
0.0
12.7
13.8
0.0
0.0
0.5
3.3
1.0
0.0
0.0
0.0
2
Al 2 O 3
FeO*
MnO
MgO
CaO
Na 2 O
K2 O
1. Ave. 32 alkaline basalts, Kenya (B) 2. Ave. phonolite (B) 3. Ave. Kenyan nephelinite (B) 4. Melilitite, W. Rift (KM) 5. Leucitite, W. Rift (KM)
6. Ave. of 55 phonolites, Uganda (B) 7. Ave. of 31 transitional basalts (B) 8. Ave. 40 trachytes (B) 9. Pantellerite (KM) 10. Comendite (KM)
11. Ave. of 26 Tholeiitic basalts (KM).
KM = Kampunzu and Mohr (1991), B = Baker, 1987.
Chapter 19: Continental Alkaline Magmatism.
The East African Rift
Figure 19.3. 143Nd/144Nd vs. 87Sr/86Sr for East
African Rift lavas (solid outline) and
xenoliths (dashed). The “cross-hair”
intersects at Bulk Earth (after Kampunzu
and Mohr, 1991), Magmatic evolution and
petrogenesis in the East African Rift system.
In A. B. Kampunzu and R. T. Lubala (eds.),
Magmatism in Extensional Settings, the
Phanerozoic African Plate. Springer-Verlag,
Berlin, pp. 85-136. Winter (2001) An
Introduction to Igneous and Metamorphic
Petrology. Prentice Hall.
Chapter 19:
Continental Alkaline
Magmatism.
The East African Rift
Figure 19.4. 208Pb/204Pb vs. 206Pb/204Pb (a) and
207Pb/204Pb vs. 206Pb/204Pb (b) diagrams for some
lavas (solid outline) and mantle xenoliths (dashed)
from the East African Rift . The two distinct Virunga
trends in (a) reflect heterogeneity between two
different samples. After Kampunzu and Mohr, 1991),
Magmatic evolution and petrogenesis in the East
African Rift system. In A. B. Kampunzu and R. T.
Lubala (eds.), Magmatism in Extensional Settings, the
Phanerozoic African Plate. Springer-Verlag, Berlin,
pp. 85-136. Winter (2001) An Introduction to Igneous
and Metamorphic Petrology. Prentice Hall.
Chapter 19: Continental Alkaline Magmatism.
The East African Rift
Figure 19.5. Chondrite-normalized REE
variation diagram for examples of the four
magmatic series of the East African Rift
(after Kampunzu and Mohr, 1991),
Magmatic evolution and petrogenesis in the
East African Rift system. In A. B.
Kampunzu and R. T. Lubala (eds.),
Magmatism in Extensional Settings, the
Phanerozoic African Plate. Springer-Verlag,
Berlin, pp. 85-136. Winter (2001) An
Introduction to Igneous and Metamorphic
Petrology. Prentice Hall.
Chapter 19: Continental Alkaline Magmatism
Figure 19.6a. Ta vs. Tb for rocks of the Red Sea, Afar, and the Ethiopian Plateau. Rocks from a particular area show nearly constant
ratios of the two excluded elements, consistent with fractional crystallization of magmas with distinct Ta/Tb ratios produced either by
variable degrees of partial melting of a single source, or varied sources (after Treuil and Varet, 1973; Ferrara and Treuil, 1974).
Chapter 19: Continental Alkaline Magmatism
Figure 19.7. Phase diagram for the system SiO2-NaAlSiO4-KAlSiO4-H2O at 1 atm. pressure. Insert shows a T-X section from the silicaundersaturated thermal minimum (Mu) to the silica-oversaturated thermal minimum (Ms). that crosses the lowest point (M) on the
binary Ab-Or thermal barrier that separates the undersaturated and oversaturated zones. After Schairer and Bowen (1935) Trans. Amer.
Geophys. Union, 16th Ann. Meeting, and Schairer (1950), J. Geol., 58, 512-517. Winter (2001) An Introduction to Igneous and
Metamorphic Petrology. Prentice Hall.
Chapter 19: Continental Alkaline Magmatism
Figure 19.8. Part of the Ne-Ks-SiO2-H2O system at 1 atm, 0.1 GPa, and 0.2 GPa, illustrating the reduction in the leucite field with
increasing PH2O. At 0.2 GPa the Lc-liquid field crosses the Ab-Or join, and the system goes from peritectic to eutectic behavior. Also
shown are contours for analyses of 122 undersaturated volcanics. After Gittins, (1979), The feldspathoidal alkaline rocks. In H. S. Yoder
Jr. (ed.), The Evolution of Igneous Rocks Fiftieth Anniversary Perspectives. Princeton University Press. Winter (2001) An Introduction to
Igneous and Metamorphic Petrology. Prentice Hall.
Figure 19.9. Hypothetical cross sections
(same vertical and horizontal scales)
showing a proposed model for the
progressive development of the East African
Rift System. a. Pre-rift stage, in which an
asthenospheric mantle diapir rises
(forcefully or passively) into the lithosphere.
Decompression melting (cross-hatch-green
indicate areas undergoing partial melting)
produces variably alkaline melts. Some
partial melting of the metasomatized subcontinental lithospheric mantle (SCLM) may
also occur. Reversed decollements (D1)
provide room for the diapir. b. Rift stage:
development of continental rifting, eruption
of alkaline magmas (red) mostly from a deep
asthenospheric source. Rise of hot
asthenosphere induces some crustal anatexis.
Rift valleys accumulate volcanics and
volcaniclastic material. c. Afar stage, in
which asthenospheric ascent reaches crustal
levels. This is transitional to the development
of oceanic crust. Successively higher
reversed decollements (D2 and D3)
accommodate space for the rising diapir.
After Kampunzu and Mohr (1991),
Magmatic evolution and petrogenesis in the
East African Rift system. In A. B.
Kampunzu and R. T. Lubala (eds.),
Magmatism in Extensional Settings, the
Phanerozoic African Plate. Springer-Verlag,
Berlin, pp. 85-136 and P. Mohr (personal
communication). Winter (2001) An
Introduction to Igneous and Metamorphic
Petrology. Prentice Hall.
Chapter 19: Continental Alkaline Magmatism.
Carbonatites
Table 19-4. Some Minerals in Carbonatites.
Table 19-3. Carbonatite Nomenclature
Name
Calcite-carbonatite
Dolomite-carbonatite
Ferrocarbonatite
Natrocarbonatite
Alternative
Coarse
Med.-Fine
sövite
alvikite
rauhaugite*
beforsite
* Rarely used, beforsite may be applied to any grain size.
Carbonates
Calcite
Dolomite
Ankerite
Siderite
Strontanite
Bastnäsite (Ce,La)FCO3)
* Nyerereite ((Na,K) 2Ca(CO3)2)
* Gregoryite ((Na,K) 2CO3)
Silicates
Pyroxene
Aegirine-augite
Diopside
Augite
Olivine
Monticellite
Alkali amphibole
Allanite
Andradite
Phlogopite
Zircon
Source: Heinrich (1966), Hogarth (1989)
Sulfides
Pyrrhotite
Pyrite
Galena
Sphalerite
Oxides-Hydroxides
Magnetite
Pyrochlore
Perovskite
Hematite
Ilmenite
Rutile
Baddeleyite
Pyrolusite
Halides
Fluorite
Phosphates
Apatite
Monazite
* only in natrocarbonatite
Chapter 19:
Continental Alkaline
Magmatism.
Carbonatites
Figure 19.10. African carbonatite
occurrences and approximate ages in Ma.
OL = Oldoinyo Lengai natrocarbonatite
volcano. After Woolley (1989) The spatial
and temporal distribution of carbonatites. In
K. Bell (ed.), Carbonatites: Genesis and
Evolution. Unwin Hyman, London, pp. 1537. Winter (2001) An Introduction to
Igneous and Metamorphic Petrology.
Prentice Hall.
Carbonatites
Figure 19.11. Idealized cross section of
a carbonatite-alkaline silicate complex
with early ijolite cut by more evolved
urtite. Carbonatite (most commonly
calcitic) intrudes the silicate plutons,
and is itself cut by later dikes or cone
sheets of carbonatite and
ferrocarbonatite. The last events in
many complexes are late pods of Fe
and REE-rich carbonatites. A fenite
aureole surrounds the carbonatite
phases and perhaps also the alkaline
silicate magmas. After Le Bas (1987)
Carbonatite magmas. Mineral. Mag.,
44, 133-40. Winter (2001) An
Introduction to Igneous and
Metamorphic Petrology. Prentice Hall.
Table 19-5. Representative Carbonatite Compositions
Chapter 19: Continental
Alkaline Magmatism.
Carbonatites
Table 19-5. Representative Carbonatite Compositions
%
SiO2
CalciteDolomiteFerroNatrocarbonatite carbonatite carbonatite carbonatite
2.72
3.63
4.7
0.16
TIO2
0.15
0.33
0.42
0.02
Al2O3
1.06
0.99
1.46
0.01
Fe2O3
FeO
MnO
MgO
CaO
Na2O
2.25
1.01
0.52
1.80
49.1
0.29
2.41
3.93
0.96
15.06
30.1
0.29
7.44
5.28
1.65
6.05
32.8
0.39
0.05
0.23
0.38
0.38
14.0
32.2
K2O
0.26
0.28
0.39
8.38
P2O5
2.10
1.90
1.97
0.85
H2O+
0.76
1.20
1.25
0.56
CO2
BaO
SrO
F
Cl
S
SO3
36.6
0.34
0.86
0.29
0.08
0.41
0.88
36.8
0.64
0.69
0.31
0.07
0.35
1.08
30.7
3.25
0.88
0.45
0.02
0.96
4.14
31.6
1.66
1.42
2.50
3.40
3.72
%
ppm
Li
Be
Sc
V
Cr
Co
Ni
Cu
Zn
Ga
Rb
Y
Zr
Nb
Mo
Ag
Cs
Hf
Ta
W
Au
Pb
Th
U
La
Ce
Pr
Nd
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
CalciteDolomiteFerroNatrocarbonatite carbonatite carbonatite carbonatite
0.1
2
7
80
13
11
18
24
188
<5
14
119
189
1204
20
5
56
52
9
608
1687
219
883
130
39
105
9
34
6
4
1
5
1
<5
14
89
55
17
33
27
251
5
31
61
165
569*
12
3
1
3
21
10
89
93
13
764
2183
560
634
45
12
5
10
0
10
12
10
191
62
26
26
16
606
12
204
127
1292
71
4
1
1
20
12
217
276
7
2666
5125
550
1618
128
34
130
16
52
6
17
2
16
-
116
0
0
88
<20
178
7
0
28
125
6
0
0
49
4
11
545
645
102
8
2
2
0
Wooley & Kempe (1989), natrocarb. from Keller & Spettel (1995).
* one excluded analysis contained 16,780 ppm Nb.
Chapter 19:
Continental Alkaline
Magmatism.
Carbonatites
Figure 19.12. Initial 143Nd/144Nd vs. 87Sr/86Sr diagrams
for young carbonatites (dark shaded), and the East
African Carbonatite Line (EACL), plus the HIMU and
EMI mantle reservoirs. From Bell and Blenkinsop
(1987, Geology, 15, 99-102), (1989, in K. Bell (ed.),
Carbonatites: Genesis and Evolution. Unwin Hyman,
London, pp. 278-300 ). Also included are the data for
Oldoinyo Lengai natrocarbonatites and alkali silicate
rocks (from Bell and Dawson, 1995, in Bell, K. and J.
Keller (eds.), (1995). Carbonatite Volcanism: Oldoinyo
Lengai and the Petrogenesis of Natrocarbonatites.
Springer-Verlag. Berlin, pp. 100-112 ). MORB values
and the Mantle Array are from Figure 10-15. Winter
(2001) An Introduction to Igneous and Metamorphic
Petrology. Prentice Hall.
Chapter 19:
Continental Alkaline
Magmatism.
Carbonatites
Figure 19.13. Solidus curve (purple) for
lherzolite-CO2-H2O with a defined ratio of
CO2 : H2O = 0.8. Red curves = H2O-saturated
and volatile-free peridotite solidi. Approximate
shield geotherm in dashed green. After Wyllie
(1989) Origin of carbonatites: Evidence from
phase equilibrium studies. In K. Bell (ed.),
Carbonatites: Genesis and Evolution. Unwin
Hyman, London. pp. 500-545. Winter (2001)
An Introduction to Igneous and Metamorphic
Petrology. Prentice Hall.
Chapter 19: Continental Alkaline Magmatism
Figure 19.14. Grid showing the melting products as a function of pressure and % partial melting of model pyrolite mantle with 0.1%
H2O. Dashed curves are the stability limits of the minerals indicated. After Green (1970), Phys. Earth Planet. Inter., 3, 221-235. Winter
(2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.
Chapter 19: Continental Alkaline Magmatism.
Carbonatites
Figure 19.15. Silicate-carbonate liquid
immiscibility in the system Na2OCaO-SiO2-Al2O3-CO2 (modified by
Freestone and Hamilton, 1980, to
incorporate K2O, MgO, FeO, and
TiO2). The system is projected from
CO2 for CO2-saturated conditions.
The dark shaded liquids enclose the
miscibility gap of Kjarsgaard and
Hamilton (1988, 1989) at 0.5 GPa,
that extends to the alkali-free side (AA). The lighter shaded liquids enclose
the smaller gap (B) of Lee and Wyllie
(1994) at 2.5 GPa. C-C is the revised
gap of Kjarsgaard and Hamilton.
Dashed tie-lines connect some of the
conjugate silicate-carbonate liquid
pairs found to coexist in the system.
After Lee and Wyllie (1996)
International Geology Review, 36, 797819. Winter (2001) An Introduction to
Igneous and Metamorphic Petrology.
Prentice Hall.
Chapter 19: Continental Alkaline Magmatism.
Carbonatites
Figure 19.16. Schematic cross
section of an asthenospheric
mantle plume beneath a
continental rift environment, and
the genesis of nephelinitecarbonatites and kimberlitecarbonatites. Numbers
correspond to Figure 19-13. After
Wyllie (1989, Origin of
carbonatites: Evidence from
phase equilibrium studies. In K.
Bell (ed.), Carbonatites: Genesis
and Evolution. Unwin Hyman,
London. pp. 500-545) and Wyllie
et al., (1990, Lithos, 26, 3-19).
Winter (2001) An Introduction to
Igneous and Metamorphic
Petrology. Prentice Hall.
Chapter 19:
Continental
Alkaline
Magmatism.
Lamproites
Figure 19.17. Chondrite-normalized rare earth element
diagram showing the range of patterns for olivine-,
phlogopite-, and madupitic-lamproites from Mitchell
and Bergman (1991) Petrology of Lamproites. Plenum.
New York. Typical MORB and OIB from Figure 10-13
for comparison. Winter (2001) An Introduction to
Igneous and Metamorphic Petrology. Prentice Hall.
Chapter 19: Continental Alkaline Magmatism.
Lamproites
Table 19-6. Lamproite Nomenclature
Old Nomenclature
Recommended by IUGS
wyomingite
orendite
madupite
cedricite
mamilite
wolgidite
fitzroyite
verite
jumillite
fortunite
cancalite
diopside-leucite-phlogopite lamproite
diopside-sanidine-phlogopite lamproite
diopside madupidic lamproite
diopside-leucite lamproite
leucite-richterite lamproite
diopside-leucite-richterite madupidic lamproite
leucite-phlogopite lamproite
hyalo-olivine-diopside-phlogopite lamproite
olivine diopside-richterite madupidic lamproite
hyalo-enstatite-phlogopite lamproite
enstatite-sanidine-phlogopite lamproite
From Mitchell and Bergman (1991).
Chapter 19: Continental Alkaline Magmatism.
Lamproites
Figure 19.18a. Initial 87Sr/86Sr vs. 143Nd/144Nd for lamproites (red-brown) and kimberlites (red). MORB and the Mantle Array are
included for reference. After Mitchell and Bergman (1991) Petrology of Lamproites. Plenum. New York. Typical MORB and OIB from
Figure 10-13 for comparison. Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.
Chapter 19: Continental Alkaline Magmatism.
Lamproites
Figure 19.18b. 207Pb/204Pb vs. 206Pb/204Pb for lamproites and kimberlites. After Mitchell and Bergman (1991). Mitchell and Bergman
(1991) Petrology of Lamproites. Plenum. New York. Typical MORB and OIB from Figure 10-13 for comparison. Winter (2001) An
Introduction to Igneous and Metamorphic Petrology. Prentice Hall.
Chapter 19: Continental Alkaline Magmatism.
Lamprophyres
Table 19-7. Lamprophyre Nomenclature
Light-colored
constituents
Predominant mafic minerals
biotite,
hornblende,
Na- Ti- amphib., melilite, biotite,
feldspar
foid
diopsidic augite, diopsidic augite,
Ti-augite,
± Ti-augite
(± olivine)
(± olivine)
olivine, biotite ± olivine ± calcite
or > pl
-minette
vogesite
pl > or
-kersantite
spessartite
or > pl
feld > foid
sannaite
pl > or
feld > foid
camptonite
-glass or foid
monchiquite
polzenite
--alnöite
Lamprophyre branch:
Calc-alkaline
Alkaline
Melilitic
After Le Maitre (1989), Table B.3, p. 11.
Chapter 19:
Continental Alkaline
Magmatism.
Kimberlites
Figure 19.19. Model of an idealized kimberlite
system, illustrating the hypabyssal dike-sill complex
leading to a diatreme and tuff ring explosive crater.
This model is not to scale, as the diatreme portion is
expanded to illustrate it better. From Mitchell
(1986) Kimberlites: Mineralogy, Geochemistry, and
Petrology. Plenum. New York. Winter (2001) An
Introduction to Igneous and Metamorphic
Petrology. Prentice Hall.
Chapter 19:
Continental Alkaline
Magmatism.
Kimberlites
Table 19-8. Average Analyses and Compositional Ranges
of Kimberlites, Orangeites, and Lamproites.
SiO2
Kimberlite
33.0
27.8-37.5
Orangeite
35.0
27.6-41.9
Lamproite*
45.5
TiO2
1.3
0.4-2.8
1.1
0.4-2.5
2.3
Al2O3
FeO*
MnO
MgO
CaO
Na2O
2.0
7.6
0.14
34.0
6.7
0.12
1.0-5.1
5.9-12.2
0.1-0.17
17.0-38.6
2.1-21.3
0.03-0.48
2.9
7.1
0.19
27.
7.5
0.17
0.9-6.0
4.6-9.3
0.1-0.6
10.4-39.8
2.9-24.5
0.01-0.7
8.9
6.0
11.2
11.8
0.8
K2O
0.8
0.4-2.1
3.0
0.5-6.7
7.8
P2O5
LOI
1.3
10.9
0.5-1.9
7.4-13.9
1.0
11.7
0.1-3.3
5.2-21.5
2.1
3.5
Sc
V
Cr
Ni
Co
Cu
Zn
Ba
Sr
Zr
Hf
Nb
Ta
Th
U
La
Yb
14
100
893
965
65
93
69
885
847
263
5
171
12
20
4
150
1
20
95
1722
1227
77
28
65
3164
1263
268
7
120
9
28
5
186
1
Data from Mitchell (1995), Mitchell and Bergman (1991)
* Leucite Hills madupidic lamproite
19
66
430
152
41
9831
3860
1302
42
99
6
37
9
297
1
Chapter 19:
Continental Alkaline
Magmatism.
Kimberlites
Figure 19.20a. Chondrite-normalized REE diagram
for kimberlites, unevolved orangeites, and
phlogopite lamproites (with typical OIB and
MORB). After Mitchell (1995) Kimberlites,
Orangeites, and Related Rocks. Plenum. New York.
and Mitchell and Bergman (1991) Petrology of
Lamproites. Plenum. New York. Winter (2001) An
Introduction to Igneous and Metamorphic
Petrology. Prentice Hall.
Chapter 19:
Continental Alkaline
Magmatism.
Kimberlites
Figure 19.20b. Chondrite-normalized spider
diagram for kimberlites, unevolved orangeites, and
phlogopite lamproites (with typical OIB and
MORB). After Mitchell (1995) Kimberlites,
Orangeites, and Related Rocks. Plenum. New York.
and Mitchell and Bergman (1991) Petrology of
Lamproites. Plenum. New York. Winter (2001) An
Introduction to Igneous and Metamorphic
Petrology. Prentice Hall.
Chapter 19: Continental Alkaline Magmatism.
Kimberlites
Figure 19.21. Hypothetical cross section of an Archean craton with an extinct ancient mobile belt (once associated with subduction) and a
young rift. The low cratonal geotherm causes the graphite-diamond transition to rise in the central portion. Lithospheric diamonds
therefore occur only in the peridotites and eclogites of the deep cratonal root, where they are then incorporated by rising magmas (mostly
kimberlitic- “K”). Lithospheric orangeites (“O”) and some lamproites (“L”) may also scavenge diamonds. Melilitites (“M”) are generated
by more extensive partial melting of the asthenosphere. Depending on the depth of segregation they may contain diamonds. Nephelinites
(“N”) and associated carbonatites develop from extensive partial melting at shallow depths in rift areas. After Mitchell (1995) Kimberlites,
Orangeites, and Related Rocks. Plenum. New York. Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.