Formation And Occurrences Of Laumontite And Related Minerals In The Carolinas And Virginia, Middle Mesozoic Zeolite Facies Metamorphism Southern Appalachian Piedmont
Formation And Occurrences Of Laumontite And Related Minerals
In The Carolinas And Virginia, Middle Mesozoic Zeolite Facies
Metamorphism Southern Appalachian Piedmont
Donald R. Privett, P.G.
S.T.A. R. Environmental
1 Circle Street
Great Falls, SC 29055
A 175 -150 Ma hydrothermal zeolite grade metamorphic event altered most pre-Jurassic rocks in the southern
Appalachian Piedmont from south central Georgia to southern Virginia. Laumontite fills fractures and replaces
plagioclase in exposed and in drilled and cored subsurface rocks. A swarm of 200 Ma northwest/north striking
diabase dikes were injected and basalt flowed into into rift valleys during initial Atlantic rifting, followed by filling of
half grabens with immature clastic sediments. Fractures (joints and faults) served as conduits for calcium-saturated
warmed water that crystallized laumontite, prehnite, calcite and other zeolites. This period of zeolite grade thermal
alteration metamorphism is widespread.
Piedmont Neoproterozoic and Paleozoic igneous, metamorphic, and Triassic igneous and sedimentary
rocks of the Southern Appalachians were subjected to a period of zeolite grade thermal metamorphism about 175-
150 Ma evidenced by the widespread zeolite occurrences in older and younger intrusive and in older
metamorphosed (mostly diorites and granites) intrusive host rocks, Figure 1 is a tectonic map (Hatcher, et. al.,
2007) showing the area geologic structures.
Zeolite grade thermal metamorphism refers to the crystallization of fracture - filling and replacement
zeolites and prehnite in host rocks. The zeolite facies is considered to represent a transitional from hydrothermal
metamorphism and to encompass all mineral, textural, and chemical changes resulting from hot waters, steam
Laumontite and other zeolites have been the subject of theoretical considerations and experimental limit
determination (Coombs, 1952) ( Thompson, 1971, Frost, 1980, Loui, 1971) plus detailed paragenesis studies
(Boles and Coombs, 1977 and Suranam, 1973). Still there is considerable disparity between theoretical and
experimental temperature and pressure limits, and the independently determined substantially lower temperatures
of natural formation. Complex ever-changing variables lower and inhibit formation.
Zeolites occur in the geothermal areas of Iceland, (Kristmannedottir and Tomanson,1978), (Mehegan, Robinson
and Delaney, 1982) and in metamorphic rocks of California, (Madsen, and Murata, 1970) and New Zealand thermal
areas (Barnes, 1977).
Boles and Coombs (1977) summarized the parameters thought to control the temperature and pressures of
formation of zeolites. Experimentally determined temperatures are both higher and lower than values obtained
under natural conditions. Fluid pressure gradients, CO2 and H2O, activities of CO2, H20, ratio of water and CO2,
the permeability, nucleation and reaction kinetics, oxygen fugacity and presence of additional ions can alter the
temperatures of formation. Stability limits determined vary widely; Loui (1971) obtained upper limits of 230º – 325º
at 0.5 kb, while Thompson (1971) obtained values of 250º at 2.75 kb. The lower limit is in even greater conflict with
natural occurrences. Loui (1971) obtained values of 150º - 200º C at 1 kb where p f = p t the lowest recorded
temperature of formation is 43º C (McCulloh, 1981) for laumontite that crystallized on rocks exposed at the Suspe
Hot Springs, California. Temperatures of 50º C for laumontite, 90º C for prehnite (Boles and Coombs, 1977) and
104º C (Castino and Sparks, 1974) have been estimated for laumontite in buried sedimentary rocks. Siki, (1969)
reported 75º + 5° C for laumontite formed in hot springs. Using calcite fluid inclusions Meghan, Robinson and
Delaney (1982) determined that laumontite filled amygdules in lava flows in Iceland formed at 140º - 200º C.
Laumontite has been identified from over 100 separate locations in relatively unweathered outcrops and in
rock exposed in foundations, trenches, quarries, mined caverns, and in cores from borings for power plants and
cuttings from water wells and exploratory test wells. Table 1 and Figure 2 shows the general geographic area of
interest and earlier referenced laumontite occurrenses. The geographic distribution of additional laumontite in the
Carolinas, Georgia and Virginia is shown in Table 2 and Figure 3.
Laumontite is present in the majority of rock exposed in the Piedmont region. Table 1 shows the previously
reported occurrences. It occurs in gneisses of the Inner Piedmont; metamorphosed and unmetamorphosed
igneous rock and metasedimentary rocks of the Charlotte Belt (Privett, 1974a) and the Kings Mountain Belt;
metavolcanic and metasedimentary rock of the Carolina Slate Belt and Triassic - Jurassic sedimentary and
The discovery of laumontite in the buried Triassic rocks and in cored basement below the Triassic of South
Carolina and south central Georgia suggest that laumonatization is even more extensive, here, laumontite fills
amygdules and replaces plagioclase in a 184 +/- 3 my basalt from Dorchester county, S.C. (Gotten et.al.,1983)
and is present in Triassic sedimentary and older igneous rocks from South Central Georgia (Chowns and
Laumontite occurs as: (1) single pink and white euhedral crystals in druses and incompletely filled veins
where it crystallized on host rock, prehnite, epidote and quartz (Figure 4), (2) veinlets of matted interpenetrating
crystal aggregates filling single and multiple narrow fractures and joints (Figure 5) and (3) common replacement
of plagioclase forming partial to complete "mosaic pseudomorphs" of laumontite after plagioclase which are
composed of minute laumontite crystals and albite (Figures 6 ). Laumontite is identified by microscopic study; in
diffuse plane light laumontized plagioclase (Figure 7A and B) displays a mottled texture (Figure 8 A and B )) and
polysynthetic twinning of plagioclase is destroyed; partly replaced plagioclase retains its twinning; however, it is
Laumontite imparts a pinkish color to the altered and replaced plagioclase. This color change is a good indication
and appears to be directly proportional to the intensity of laumonatization. The sequence is shown by partly
replaced laumontite; calcite fills the interior of the vein. Coarse grained microscopic crystals of laumontite under
crossed polars (Figure 9) display a somewhat wavy extinction. Rock cores (Figures 10 and 11) contain
replacement and fracture filling laumontite.Intenesly altered rocks are sometimes veined with laumonitite-calcite
(Figure 12 and 13).
Fine grained replacement and fracture filling laumontite (Figure 14) in outcrop and on an exposed weathered
surface of saprolite. (Figure15). Coarsly crystallized white laumontie (Figure 16) on broken rock surface.
The x-ray reflections (Table 3) vary with the relative humidity; therefore. the material is best described as
laumontite-leonhardite. It is mottled. Laumontite readily dehydrates to leonhardite unless the sample is kept under
conditions of 100% relative humidity. Partial re-hydration of leonardadite to laumontite can be observed under the
polarizing microscope when a sample is placed in water.
Tectonic activity about 175 -150 my, in the Triassic and Jurassic consisted of the separation of the
continents following the breakup of Pangea. This tectonism fractured old weaker shears, formed new joints and
faults. Siliceous cataclasite bodies and quartz mylonites formed in stressed rocks. Immature clastics were
deposited in subsiding half grabens and [generation of basaltic magmas and intrusion of diabase dikes and basaltic
to diabase sills. Basalt flows are present in Triassic sedimentary rock. Heated circulating groundwaters probably
mixed with hydrothermal solutions fluids reacted with plagioclase to form prehnite and laumontite. The excessive
calcium reacted with silica to produce the fracture filling laumontite and calcite with lower temperatures other
zeolites crystalllized. Two generations of diabase dikes are evident; suggesting that igneous activity persisted as
the stress changed. As temperatures subsided, other zeolites crystallized. This period of zeolite grade thermal
alteration metamorphism is widespread in rocks of the southern Appalachians especially Charlotte Terrane.
I thank Dr. Robert D. Hatcher, Jr.,UT Distinguished Scientist and Professor of Geology, Department of Geological
Sciences, University of Tennessee Knoxville, Tennessee for his insightful and complete review of my manuscript
and preparation of Figures 1, 2 and 3.
Table I SUMMARY OF PREVIOUSLY REPORTED LAUMONTITE OCCURRENCES
Location Host Rocks types of
Other zeolites Other Secondary
FF R D
Near Durham, NC Metamorphosed greenstone
and crystal tuffs
x Furbish, 1965
Foote mine Cleveland
Spodumene pegmatites and
x x prehnite and about 80
Nello Teer Quarry,
x x Furbish, 1972
Near Great Falls,
meta-adamellite x x epidote Privett, 1973a
Western Rowan Co.,NC
Diorite intruded by 300 ma.
x x x stilbite,
prehnite, calcite epidote,
Southern Fairfield Co.,
almandine amphibolite ? (no
Probe) and granodiorite
x chlorite South Carolina
Gas and Electric,
Near Apex, Wake Co.,
Diabase dikes and Triassic
x x harmontone
barite and saponite Ragland, 1977
Eastern Cherokee Co.,
Rhyolites and felsic gneiss x x x calcite,
Eastern Fairfield Co.,
Granite and hornblende
gneiss and 300 m.y. adamellite
x x epidote, calcite chlorite Law Engineering,
Near Tirzah North
Central York Co.,SC
Metadiorite, diorite, mafic dikes
and Triassic diabase dikes
x x stilbite prehnite, epidote Butler, 1976
North Central York Co.,
metamorphosed mafic dikes
calcite, epidote, chlorite,
prehnite Privett, 1977(a)
Center off US 58
Granite, gneiss, hornblende
x x x stilbite quartz, flourite, Privett, 1977(b)
Hylas zone - central
Sheared gneiss, schist and
x x x heulandite quartz Bobyarchick and Glover,
6 km. south of V.C.
Summer N. P.
quartz monzonite x Secor, 1982
Dorchester Co, SC
early Jurassic basalt x x Gotfried, 1983
South central Georgia diabase, sandstone and felsic
x x x prehnite, epidote
Chones and Williams,
Old Pineville Quarry,
York Co. SC
metagabbro x heulandite
calcite prehnite epidote Butler, 1983
Iredell Co., NC between
I- 40 and US 64/70.
schist x quartz
prehnite Milton, 1981
Brevard Zone near
Tunnel, Cobb County,
amphibolite grade gneiss and
schist crosscuts regional
x x (1).quartz-calcite-chlorite
prehnite, calcite and
(2).orange staining of
albite and replacement
of biotite by chlorite.
Burnley, P.C. , et.al.,
Keystone Blue quarry,
Elberton fine-grained biotite
granite cut by dikes of
pegmatitic granite and diabase.
chabazite and the
radiating zeolite ?
crystals 0.1 to 1.0
quartz, and calcite
Bulger, Dan, et.al., 2008
*FF = Fracture filling R=Replacement D= Druse
Table 2. Summary of Additional Laumontite Occurrences
Other Zeolites and
Host Rock FF R D
McGuire Nuclear Sta. and Cowans Ford Dam
Foundation borings northwestern Mecklenburg and
Lincoln Co., NC, Duke Power core repository.
Metadiorite x x epidote
Pineville Quarry southern Mecklenburg Co., NC off
Hwy. 51 rock core. Duke Power core repository.
Gabbro metagabbro x x prehnite, calcite
Boring, N.E. Gaston Co. NC .2 mi. east of US 16 on
the Catawba River (Riverbend) Duke Power core
x x prehnite
Arrowood Quarry 0.4 mi; east I-77 Mecklenburg Co.
NC, Duke Power core repository
Metagabbro x x epidote calcite
Hyco Reservoir, Person Co. NC (road below dam) hornblende schist cut by
x x x
Whitnel Quarry near Lenior, Caldwell Co., NC Hornblende gneiss x Epidote calcite
Hickory Quarry 0.5 mi. north US 321, 0.8 mi. East
County Road 1536, Catawba Co. NC
Augen granite gneiss and
x epidote calcite
Quarry off SC 901, northeastern Fairfield Co. biotite gneiss and porphyry
x x epidote
Borrow Pit off SC 72, S.W. Chester Co. SC also in
roadcuts for new bridge 2007.
Metagranite and mafic dikes x x prehnite epidote
Borings North Cabarrus, Northeastern Rowan,
Davidson, Davie, Guilford, Stokes and Alamance
counties,NC 52 occurrences, Duke Power core
Granite, diorite sheared
x x x prehnite, calcite,
South Boston, VA. hornblende gneiss cut by
x x stilbite, epidote,
Boring Rock Hill Printing, White St. Rock Hill, SC,
Duke Power core repository.
Metadiorite x x epidote
Apt. Complex off SC 161,Rock Hill, SC. Metadiorite x epidote
Great Falls, SC, Chester County Rd. borrow pit. metagranite x x
North Quarry, west of Winston-Salem, Forsythe
Foliated granite to
x x calcite, epidote
Stokesdale Quarry 1 mile west NC 158 Guilford
cut by mafic dikes
x chabazite, stilbite,
Jamestown Quarry, off County road 1147, 1.5
miles east of I-85. Guilford Co. NC.
Hornblende gneiss and
X x x stilbite, heulandite,
Lexington Quarry off county Road 1646, 0.7 mi.
east US 52 Davidson Co. NC.
x x x prehnite, epidote,
Churchland pluton-Davie and
Davidson Counties, NC Duke Power core
Albite granite - (300 m.y.)
27 separate borings[
x x prehnite, epidote
Boring Marshall Steam Station off Hwy. 150
eastern Catawba Co. NC, Duke Power core
Metadiorite x x prehnite, epidote
Smith Grove Quarry, Davie Co. NC Gabbro-diorite x x prehnite, epidote
Central Rock Products Quarry, east 421. central
Guilford Co. NC
Pomona Quarry south 1-40 at end of Co. Road
Chlorite schist and granite
x stilbite, calcite
Inactive quarry, Kings Creek, western York, Co.,
metadiorite x epidote
4 borings near Kings Creek eastern Cherokee
Co. , SC (across creek from above), Duke Power
metadiorite x x prehnite, calcite
*FF = Fracture filling R=Replacement D= Druse
X-Ray Diffraction Powder Data laumontite-leonhardite
I II III IV w
hkl(s) dA I dA I dA I dA I dA I
110 9.52 84 9.50 100 9.46 100 9.44 100 9.43 78
200 6.98 80 6.84 90 6.84 80 6.83 75 6.83 s6
201 6.23 w 6.19 10 6.20 W 6.18 10 6.18 w
111 5.05 18 5.04 10 5.04 10 5.04 20 5.04 18
220 4.74 30 4.73 30 4.72 30 4.72 14 4.72 16
221 4.52 25 4.49 27 4.49 15 4.49 22 4.49 32
130 4.17 100 4.16 95 4.16 100 4.15 100 4.15 100
131 3.77 w 3.78 w 3.77 w 3.77 18 3.76 w
401 3.67 28 3.66 40 3.56 30 3.65 56 3.66 42
002 3.52 56 3.51 55 3.51 40 3.50 60 3.51 94
131 3.41 16 3.41 10 3.41 10 3.41 16 3.40 26
312 3.37 w 3.35 w W 3.36 40 3.36 34
040 3.27 50 3.28 50 3:27 50 3.27 60 3.27 63
311 3.20 18 3.21 38 3.20 25 3.19 60 3,20 45
330 3.16 32 3.17 20 3.15 25 3.15 32
402 3.07 15 3.09 w
420 3.04 46 3.03 40 3.03 40 3.03 40 3.03 45
240 2.97 W 2.96 W 2.95 W 2.95 w
511 2.88 24 2.89 30 2.88 25 2.87 25 2.88 38
422 2.80 12 2.79 12 2.80 W 2.79 22 2.80 w
331.512 2.63 w 2.60 25 2.63 w 2.64 W 2.64 w
241 2.58 28 2.57 w 2.57 20 2.57 30 2.57 34
132 2.54 w
222,203 2.52 14 2.52 w 2.52 w
601,441 2.44 26 2.45 30 2.44 25 2.44 43
403 2.39 16 2.39 w
151 2.36 24 2.36 w 2.36 15 2.36 23
250 2.27 12 2.29 w 2.27 10 2.27 w
622 2.22 w 2.21 w 2.22 w 2.22 w
060 2.18 14 2.19 25 2.18 w
333,620 2.16 30 2.15 15 2.15 20 2.15 28
I. Euhedral white crystal on diorite. Woodleaf (luarry. Rowan County
II Pink asicular crystals, Lexin9ton Quarry, Davidson County, North Carolina
III. Laumontite, pink asicular crystals from -790 feet in well drilled in East Spencer,
Rowan County, NC, Isenhour Brick and Tile Company.
IW Leonhardite. Madsen and Murata, 1970, p. 193
W Laumontite, LIou, 1971, p. 386.
(s) after Liou, 1971, p. 386.
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Figure 1. Geologic Provinces SC, NC, Va., and Ga. Hatcher, Tectonic index map, 2007.
Figure 4. Carse-grained white laumontite on fracture in diorite, Woodleaf Quarry, Rowan County, NC.
Figure 5. Brecciated diorite with vein filled by white calcite and pink laumontite.
Lexington Quarry, Davidson County, NC
Figure 6A and B “Pseudomorph” of laumontite after plagioclase, displaying the typical mottled mosaic
texture seen in plane light.
Figure 7 Texture of partly laumonitized plagioclase in quartz monzonite, mottled texture, center unaltered. Plane light.
Lexington Quarry, Davidson County, NC
Figure 8 A and B. Texture of partly laumontized plagioclase in quartz monzonite, Lexington Quarry Davidson County,
NC. The plagioclase crystal in the center bottom still retains twinning while twinning is nearly destroyed in the
more completely altered crystal at the right. A. plane light. B. crossed polars
Figure 9. Coarse grained laumontite crystals crossed polars. Lexington Quarry, Davidson County, NC
Figure 10.. Coarse Laumontite - calcite. Small calcite crystals at margins. Crossed polars.
Figure 11. Pink fracture filling – replacement laumontite in core. Churchland Granite. Davie Co, NC. Duke Energy
Figure 12. Rock core containing fracture filling veinlets of acicular laumontite. Duke Energy core.
Cherokee County, SC.
Figure 13. Intensely altered rock, with fracture filling laumontite-calcite, crossed polars.
Figure 14. Fracture filling laumontite veinlets,crossed polars scale 1 cm 0.5 mm. Lexington Quarry, Davidson
Figure 15. Intensely altered metadiorite? With replacement and fracture filling laumontite - leonhardite.
Compass left scale.
Figure 16. Coarse grained white laumontite, Cherokee County, SC Cherokee Nuclear Site. .
Duke Energy 1 cm equals 1 cm.