Cryptic and partially buried calderas along a strike

317
CRYPTIC
CIND
Jose
1
German
CONICET
Ci enci as
Republica
-
BURIED CCILDERM
&LONG
CI
IN THE CENTRCIL CINDES.
PFIRTIFILLY
FAULT
STRIKE-SLIP
SYSTEM
Viramontea
Universidad
Natural
es
Argentina.
and
Ivan
Alejandro
National
de
Buenos
&ire5
Salta,
177
Petrinovic*
-
Facul
4.400
tad
de
Sal ta
Resumen.
Se
descr
parci al mente
lineamientos
Andes
Centrales.
Key
slip
words:
cal
i ben
una
soterradas,
tect6nicos
deras
-
serie
de
cal deras
cripticas
de edad
Cenozoica,
asoci
de orientacidn
NS y ONO-ESE
Central
(Sndes
-
ignimbrites
-
adas
en
Y/o
a
105
strike-
fault.
In
the
Central
Andes
(16°S-2G0S)
a major
calcalkaline
volcanic
province
(CVZ)
developed
from
lower
Miocene
to
the
Present
related
to the
subduction
of the Nazca
be1 ow
plate
the South
American
Plate.
One
of
the
1 argest
volumes
of ash-f
1 ow
sheet e.
the
in
world
is
exposed
in the Puna
-Altiplano
plateau
(CVZ)
; but
related
with
known
emission
few
of
them
are
evidently
<enters.
been
a lot
of ash-flow
field5
have
the
last
years,
In
Baker
1981;
tlarinovic
y Lahsen
1984;
described
(Guest,
1969;
Rami rez
1977;
Coira
y Paris
1981;
Gardeweg
y
Kussmaul
et al,
1985)
but
few sources
have
been
identified,
mainly
because
of
structures,
extensive
mantling
by
large
size
of such
the
interfingering
of different
sheets,
volcanic
units,
younger
the
lack
of precise
field
mapping
and tectonic
deformation.
sever al
More
available
Landsat
imagery
and
recent1
y,
detailed
regional
volcanological
field
studies
facilitated
to
Francis
et
al
few major
calderas
in the CVZ (
identify
a
“Cai 11 oma
Davi la,
1981
“Cerro
Gal An
Caldera”;
1978
Caldera”;
Noble
Noble
et al
1979 “Pampas
Gal eras
Cal dera”;
Ramirer,
1982 “Portugueza
Caldera”;
Gardeweg
and
McKee,
and
1985
Gonz al et
Ferran
et
al
“La
Pacana
Cal der a” ;
1907
1997
Coira
et al
1987;
Ort
et
al,
Caldera”;
“Wheelwright
“Pair i que
and
Panizos
Caldera”;
Seggiaro
et al
1986
“Cerro
Coranzuli
complex”;
Viramonte
et al.
1984a
“Ramadas
Caldera”
;
“Farall6n
Negro
complex”,
etc).
Llambias,
1971
Cenoz oi c
a close
relationship
betwFen
On the other
hand,
transcurrent
and major
N-S
structures
and WNW-ESE
volcani
5m
Vi ramonte
were
established
by
fault
system
between
2,305-2805
Ojos
al
(1984)
and
Gonzalez
Ferrdn
et
al.
(1985)
for
the
et
de1 Sal ado area.
FIGURE
la
REFERENCES
Yak are
Caldora rim
WNW-ESE
N-s hOId
Eati
mgcfmcturn
kctonlo
valcanlc ahain
Troavonal
VOIWIIC chair
3. La RJcom mIdem
4. Awas Colientcs c&era
s.Cdan
~ldrro
6. Cnro E4oncacoldcra
7.WMtigM
owucl
cdderci
8. Faral!on Negro cddcra
_.“__
.
-lcI”II..
319
This
relationship
produced:
a)
the
N-S
trend
main
magmatic
arc along the
Argentine-Chilean-Bolivian
boundary
(principal
volcanic
range),
b) the
secondary
volcanic
range,
located
on
the Puna-Western
Cordilleran
border
and
c)
the
WNW-ESE
Transversal
Volcanic
Chains that developed
to
the
east
of the first one (Viramonte
et al 1984b)
(fig
la) such
as:
1)
Liper
Megafracture,
related
to
Paniros-Coranruli
Transverse
Volcanic
Chain.
2)
Calama-Olacapato-El
Toro
(COT)
left
lateral
Transcurrent
fault with Puntas NegrasPuevar
volcanic
chain.
3)
Archibarca-Galan
megafractures
with
ArchibarcaBeltran-Galan
Volcanic
chain.
4)
Culampaja
tlegafracture
with
Carachipampa-Farall6n
Negro Volcanic
chain.
5)
Tucuman-Aconquija
megafracture
with Ojos de1
SaladoWheelwright
volcanic
chain.
A
volcano-tectonic
detailed
analysie
of
this
relationship,
suggest5
that
ignimbrite
the
main
5ources
(caldera complex)
in the CVZ, are in the transversal
volcanic
chain
system
and-or
in
NS-volcanic
arcs-Transversal
the
intersections
(figure
volcanic
chain
la).
Altough
the
Puna-Altiplano
region
is highly preserved
in its geology,
in
the
situation
produces
a
several
case5
above described
because
of the true ignimbrite
source structures,
darkening
deformation,
lack of caldera
rim, covering
by
of
beheading,
due
to
etc.,
the
volcanic
units,
avalanches,
younger
of the megafractures.
i.e.: strong deformation
in
movement5
the north end of the resurgent
La Pacana
dome and lack of it5
1987,
pp.
rim (see Gardeweg
and Ramirez,
northern
caldera
of the northern
rim and beheading
of
549, fig.2 and 9), lack
and
(figure
lb)
complex
Calientes
caldera
the
Aquas
complex
(see
the Acay subvolcanic
qranitic
deformation
in
movement
of
Llambias
et al, 1985 pp. 160), due to transurrent
the COT meqafracture.
cryptic
of
Keeping
this in mind, we found a good example
area
of
COT
buried calderas
in the central
and
partially
exist
5ource5
at least five ignimbrite
where
megafracture
Mot-t-o
complex
;El
Caldera
Calientes
Aquas
(figure
lb):
and
Ramada5
shield
caldera;
Rupasca
Organullo
caldera;
caldera.
should
An overview
of the CVZ reveals
that such examples
Considering
the large volumes
of iqnimbrites
be quite common.
hundred
one
over
that
the
Central
Andes,
we believe
in
Smith
associated
caldera
structures
must be present,
such a5
(1979) has showed for
western
United
States.
recognition
of the
At
last, we point out the importance
evolutive
history
type of caldera
complex
and its
this
of
and
Cu
ore
epi thermal
Au-Sb;Pb-Ag-Zn
large
because
many
deposits
are
Ref er ences
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Upper
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M.C.W.
(1981):
The
nature
centre5
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