| Location | Inferred Duration
| Method | Comments | Ref. |
| Round Mountain, NV | ca. 100 ka
| 40Ar/39Ar | Difference in age between adularia
from early and late alteration types
associated with gold mineralization. | Henry et al.,
1995
|
| Arcata district, Peru | 300-
800 ka | K/Ar | Duration between adularia and
acid sulfate
alteration and host rock. | de los Rios et al., 1990
|
| Yellowstone, WY | ca. 600 ka
| K/Ar
| Still active. Hydrothermal activity postdates caldera
collapse. | Fournier, 1989
|
| Lake City, CO | 200-
800 ka | K/Ar | Acid sulfate alteration
indistinguishable from
early caldera collapse and post alteration lava flow.
| Larson et al., 1987
Mehnert et al., 1980
|
| Long Valley, CA | < 760 ka
| K/Ar
| Still Active. Hydrothermal system not driven by magma
body beneath resurgent
dome. Instead, system fed by lateral fluid flow from vicinity of
50 ka - 215 ka rhyodacite
dome and <40 ka rhyolite domes on caldera rim. Two episodes of
hydrothermal activity at
300 and 40 ka. | Bailey et al., 1976 Hill and Bailey,
1985
Sorey et al., 1991
van den Bogaard and Schirnick, 1995
|
| Tavua Caldera, Fiji | 860 ka
| 40Ar/39Ar | Duration between whole-rock analysis
of monzonite copper porphyry and
whole-rock altered absarokite associated with epithermal gold
deposit. | Setterfield et al., 1992
|
| Valles Caldera, New Mexico | >1000 ka
| K/Ar | Still active. U disequilibrium dating
suggests at least three
distinct hydrothermal systems existed during this period, each
lasting from 50 to 500 ka. | WoldeGabriel and Goff, 1992
Goff and Gardner, 1994
|
| Tonopah district, NV | < 1700 ka
| K/Ar | Interval of mineralization bounded by
well-dated young host rock and old
post-mineral tuff. | Silberman et al., 1979
|
| Panasqueira, Portugal | 4200 ka
| 40Ar/39Ar | Minimum age difference between two
distinct generations of muscovite,
each associated with tin-tungsten mineralization, and each
produced by thermal pulses that
were interpreted to have lasted < 1000 ka.
| Snee et al., 1988
|
| Butte, MT | 5300 ka | K/Ar
| Not well constrained by geochronologic data. Probably
much too long. | Woakes, 1969
Tilling et al., 1968
Meyer et al., 1968
|
| Location | Inferred Duration
| Method | Comments | Ref. |
| Cobre, Potrerillos district, Chile | <230 ka
| 40Ar/39Ar | Difference in age between hornblende
phenocrysts
and sericite from latest vein selvedges. | This study
|
| Divide district, NV | < 300 ka
| K/Ar | Well constrained by dates on both pre-
and post-mineral igneous rocks. | Silberman et al., 1979
|
| Koloula, Guadalcanal, Solomon Islands
| ca. 300 ka
ca. 250 ka | K/Ar | Two distinct
prophyry-related
hydrothermal
systems separated temporally by about 400 ka. Total duration for
both systems and
intervening hiatus is < 900 ka. | Chivas and
McDougall, 1978
|
| FSE-Lepanto | 300 ka | K/Ar
| Duration represents spread in ages of hydrothermal
biotite, illite, and alunite.
Documents contemporaneity of porphyry Cu-Au deposit and high
sulfidation epithermal Cu-Au deposit. | Arribas et al.,
1995
|
| Marte, Chile | 300 ka | K/Ar
| Duration between acid sulfate alteration and hornblende
phenocrysts in host rock. | Vila et al., 1991
|
| Yandera, PNG | ca. 250 ka
| K/Ar
| Duration reflects time required for thermally-reset
biotite in different host rocks
to cool below blocking temperature across an area of several
square kilometers following
emplacement of mineralizing porphyry. | Grant and
Nielson, 1975
|
| Ladolam, Lihir Island, PNG | >360 ka
| K/Ar | Indistinguishable ages of hydrothermal
and phenocryst biotite in a still-active hydrothermal system.
| Rytuba et al., 1993
|
| Nevado Portuguesa, Peru | 60-500 ka
| K/Ar | Post caldera-collapse rhyodacite dome is
indistinguishable
in age from sericite associated with Ag-Au mineralization.
| Noble and
McKee, 1982
|
| Questa, NM | 400-
500 ka | 40Ar/39Ar | Age difference between
primary
biotite phenocrysts and phlogopitic vein biotite with
molybdenite. Stocks emplaced up to
5000 ka later also supported hydrothermal systems that deposited
molybdenite. | Czamanske et al., 1990
|
| El Teniente, Chile | 330-
770 ka | K/Ar | Range of 10 dates on magmatic
and
hydrothermal alteration minerals associated with the Teniente
porphyry. Smaller duration
results from discarding one date on partially chloritized
biotite. | Cuadra, 1986
|
| Uasilau-Yau Yau, PNG | ca. 400 ka
| K/Ar | Duration between hornblende phenocryst
and primary and secondary
biotite ages. | Whalen and McDougall, 1980
|
| Goldfield, Nevada | 700-
900 ka | K/Ar | Demonstrates retentivity of
alunite. | Ashley and Silberman, 1976
|
| Copper Canyon, NV | < 1000 ka
| K/Ar | Difference in age between unaltered
biotite phenocrysts and very fine
grained hydrothermal orthoclase-biotite mixture.
| Theodore, et al., 1973
|
| Urad-Henderson, Colorado | 600-
1200 ka | 40Ar/39Ar | Duration represents spread
in ages of
orthoclase, biotite, and sericite from three intrusive centers,
with one disturbed age spectrum
from data set removed. Seedorff (1988) infers that twelve
distinct intrusive stocks in the
three centers that were dated had been emplaced before the
earliest-emplaced stock could cool
sufficiently to permit the formation of low temperature
alteration. Each intrusive stock was
accompanied by high temperature hydrothermal alteration and
molybdenum mineralization,
that would have lasted, on average, at least 50 to 100 ka.
| Geissman et al.,
1992
Seedorf, 1988
Carten and Snee, 1995
|
| Tombulilato district, Indonesia | 150 - 1400
ka | K/Ar | Two spatially and temporally
separated centers, one Cu
porphyry and one high sulfidation state epithermal deposit.
Close temporal relation between
host rocks and alteration. Total duration of district 2000 ka.
| Perello, 1994
|
| Orcopampa district, Peru | 0-1500 ka
| K/Ar | Barren acid sulfate alteration
indistinguishable in age from
its host rock. Ag-Au mineralization 1000 to 1500 ka younger than
host rock. | McKee et al., 1994
|
| Yerington, NV | ca. 1000 ka
| U/Pb
| Difference in age between earliest and latest of four
quartz monzonite porphyry
stocks. Most copper mineralization and potassic alteration, but
no sericitic alteration,
completed before the emplacement of the last porphyry stock.
| Dilles and
Wright, 1988
|
| Porgera, Papua New Guinea | ca. 1000 ka
| 40Ar/39Ar | Duration between igneous hornblende
and biotite
from multiple intrusive bodies and hydrothermal illite and
roscoelite associated with gold-bearing veins. Interpretation
complicated by excess Ar in many samples. | Richards and
McDougall, 1990
|
| Summitville, Colorado | 600-
2800 ka | K/Ar | Well constrained by dates on
both pre- and
post-mineral igneous rocks. Demonstrates retentivity of alunite.
| Mehnert, et al.,
1973
|
| Nevados del Famatina, Argentina | 1200 ka
| 40Ar/39Ar | Duration between Cu porphyry-style
alteration and
later sericitic and alunitic alteration interpreted to be parts
of the same 2.5 kilometer-wide
hydrothermal system. | Losada-CalderĒn et al., 1994
|
| Bodie, CA | 1500 ka | K/Ar
| Duration based on age difference between two temporally
distinct sets of
adularia-bearing vein systems. | Silberman, 1983
|
| El Salvador, Chile | 1200-3000 ka
| K/Ar | Total duration of X, K, and L feldspar
porphyries ca. 3000 ka. Duration
of L porphyry (youngest) hydrothermal system constrained to about
1200 ka by age difference
between sericite in K porphyry and fresh hornblende in L
porphyry. | Gustafson and Hunt, 1975
|
| Geysers, CA | >1400 ka | K/Ar
| Still-active vapor-dominated geothermal system related
to a 100 cubic kilometer
felsite intrusion dated at 1.3 to 1.4 Ma. Hydrothermal system
was water-dominated for about
700 ka, based on 0.69 Ma age of adularia veins.
| Donnelly-Nolan et al., 1993
|
| Sleeper, NV | 2000 ka | 40Ar/39Ar
| Extremely low radiogenic yields on large, impure
adularia samples resulted in
low quality results. Probable duration of hydrothermal activity
< 500 ka. | Conrad et al., 1993
|
| Bingham, UT | 2100 ka | K/Ar
| Complex results suggest a duration of at least 1000 ka
and perhaps as much as
3200 ka. Well constrained sequence of porphyry intrusions
requires most mineralization
between equigranular quartz monzonite (mean of 6 K-Ar biotite and
1 K-Ar plagioclase of
39.8+/-0.4 my) and the Andy Dike (mean of 3 K-Ar biotite of
37.7+/-0.5 my). Alteration and
metal zoning show close correlation to quartz monzonite porphyry
(no date on unaltered
minerals). | Warnaars et al., 1978
|
| Los Bronces, Chile | 300-
2500 ka | K/Ar | Mineralized breccias emplaced
during 300 ka
period between pre-ore sericite and post-ore dacite. Long
duration estimate depends on a
sample whose age is inconsistent with geologic constraints
| Warnaars et al.,
1985
|
| La Escondida, Chile | 2700 ka
| K/Ar | Difference in age beween hydrothermal
biotite and younger sericite. The low
resolution dates are also compatible with a much shorter
duration. | Alpers
and Brimhall, 1988
|
| Toquepala, Peru | 3900 ka
| 40Ar/39Ar | Total duration of hydrothermal
activity, extended by the emplacement of
voluminous post-ore dacite and latite stocks. All economic Cu
and Mo was emplaced within
1000 ka. | Clark, 1993
|
| Chuquicamata, Chile | 600-
4500 ka | 40Ar/39Ar
K/Ar | Difference in age
between early
hydrothermal biotite and latest sericitic alteration. Smaller
figure is difference in age between
40Ar/39Ar age of biotite from Maksaev et al, (1988) and K/Ar age
of sericite from Ambrus
(1977). | Quirt et al., 1971 Ambrus, 1977
Maksaev et al., 1988
|