TY - JOUR
T1 - The Alamos Metamorphic Complex, evidence of late Paleozoic collision between Laurentia and Gondwanan blocks in northwestern Mexico
AU - Vega-Granillo, Ricardo
AU - Bourjac-de-Anda, Angélica
AU - Vidal-Solano, Jesús Roberto
AU - Araux-Sánchez, Elizabeth
PY - 2019/4/1
Y1 - 2019/4/1
N2 - The Alamos Complex is a metamorphosed volcano-sedimentary sequence
exposed south of the late Paleozoic Ouachita-Marathon-Sonora orogen in
northwestern Mexico, which in turn, is regarded as a continuation of the
Alleghenian-Variscan mountain chain. Mineral assemblages in metavolcanic
rocks indicate greenschist facies metamorphism. Thermobarometric studies
yield an average metamorphic temperature of 380 °C, whereas
andalusite in metapelites indicates pressure less than 0.4 ± 0.05
GPa. The main deformation phase generated pervasive foliation, which in
turn was isoclinal to close folded and a second axial planar cleavage
was developed. Metavolcanic rocks of the Alamos Complex can be separated
in two suites: (1) an anorogenic suite, similar to enriched middle ocean
basalts (E-MORB) in the Tesia region, and (2) an orogenic suite,
characteristic of volcanic-arc setting in the Mocuzari region. U-Pb
detrital zircon geochronology of one sample from Tesia yielded a maximum
depositional age averaging 395 ± 28 Ma. One sample from the
Mocuzari region yielded a maximum depositional age averaging 1104
± 24 Ma, with the largest peak at 1428. A clastic sequence
correlated with the Middle Triassic-Lower Jurassic Barranca Group,
nonconformably cover the Alamos Complex. The basal conglomerate of that
group yields a maximum depositional age averaging 372 ± 23 Ma.
Accordingly, the Alamos Complex must be in part deposited after the
early Devonian time and before the Middle Triassic. The main sources of
detritus for the complex are the Meso- and Paleoproterozoic rocks of
southwestern Laurentia, whereas the main source of detritus for the
Barranca Group is the Rio Fuerte Formation exposed 100 km south of the
study area. The metamorphic event is ascribed to the late Paleozoic
collision of Gondwanan blocks against the southern margin of Laurentia.
AB - The Alamos Complex is a metamorphosed volcano-sedimentary sequence
exposed south of the late Paleozoic Ouachita-Marathon-Sonora orogen in
northwestern Mexico, which in turn, is regarded as a continuation of the
Alleghenian-Variscan mountain chain. Mineral assemblages in metavolcanic
rocks indicate greenschist facies metamorphism. Thermobarometric studies
yield an average metamorphic temperature of 380 °C, whereas
andalusite in metapelites indicates pressure less than 0.4 ± 0.05
GPa. The main deformation phase generated pervasive foliation, which in
turn was isoclinal to close folded and a second axial planar cleavage
was developed. Metavolcanic rocks of the Alamos Complex can be separated
in two suites: (1) an anorogenic suite, similar to enriched middle ocean
basalts (E-MORB) in the Tesia region, and (2) an orogenic suite,
characteristic of volcanic-arc setting in the Mocuzari region. U-Pb
detrital zircon geochronology of one sample from Tesia yielded a maximum
depositional age averaging 395 ± 28 Ma. One sample from the
Mocuzari region yielded a maximum depositional age averaging 1104
± 24 Ma, with the largest peak at 1428. A clastic sequence
correlated with the Middle Triassic-Lower Jurassic Barranca Group,
nonconformably cover the Alamos Complex. The basal conglomerate of that
group yields a maximum depositional age averaging 372 ± 23 Ma.
Accordingly, the Alamos Complex must be in part deposited after the
early Devonian time and before the Middle Triassic. The main sources of
detritus for the complex are the Meso- and Paleoproterozoic rocks of
southwestern Laurentia, whereas the main source of detritus for the
Barranca Group is the Rio Fuerte Formation exposed 100 km south of the
study area. The metamorphic event is ascribed to the late Paleozoic
collision of Gondwanan blocks against the southern margin of Laurentia.
KW - Alleghenian orogeny
KW - Pangea amalgamation
KW - Detrital zircon geochronology
KW - Paleozoic regional metamorphism
KW - Volcanic rock geochemistry
U2 - 10.1007/s00531-019-01693-y
DO - 10.1007/s00531-019-01693-y
M3 - Artículo
SN - 1437-3254
VL - 108
SP - 1013
EP - 1027
JO - International Journal of Earth Sciences
JF - International Journal of Earth Sciences
IS - 3
ER -