Mineralogy and geochemistry of sands along the Manzanillo and El Carrizal beach areas, southern Mexico: implications for palaeoweathering, provenance and tectonic setting
Por:
Armstrong-Altrin J.S., Lee Y.I., Kasper-Zubillaga J.J., Trejo-Ramírez E.
Publicada:
1 jul 2017
Categoría:
Geology
Resumen:
The provenance of sands from the Manzanillo (MN) and El Carrizal (CAR)
beach areas along the Mexican Pacific coast (southern Mexico) was
investigated based on their modal composition, mineralogy and
geochemical data. The average quartz, feldspar and lithic fragment (QFL)
ratios revealed that the proportion of quartz is higher in CAR sands
than in MN sands. In comparison with MN, the CAR sands are enriched in
SiO2 content with higher SiO2/Al2O3 ratio indicating that sediment
recycling is greatest for the CAR sands. The variation in K2O/Al2O3 and
Na2O/K2O ratios between the MN and CAR sands specified a difference in
the relative proportion of plagioclase. The chemical index of alteration
(CIA) and Plagioclase Index of Alteration (PIA) values revealed a
moderate weathering intensity in the source areas. The MN sands are
characterized by a low degree of rare earth element (REE) fractionation
(La-CN/Yb-CN=similar to 6-7), whereas the CAR sands define fractionated
REE patterns (La-CN/Yb-CN=similar to 8.8-16.8). The fractionated REE
pattern with elevated total low REE (Sigma LREE) content of the CAR
sands suggested that sediment sorting is higher for the CAR than MN
sands. Small negative and positive Eu anomalies (Eu/Eu-*=similar to
0.91-1.23) of MN sands indicated the derivation of sediments from
felsic-intermediate source rocks. The CAR sands showed higher
concentration of Sigma LREE than total heavy REE (Sigma HREE) and
characterized by a significant negative Eu anomaly (Eu/Eu-*=similar to
0.46-0.78), suggested that the source rock is felsic type. The result
obtained by the comparison of REE patterns of the beach sands to the
probable source rocks is also consistent with this observation. The
compositional differences identified between the MN and CAR beach areas
suggested that longshore current in the mixing and homogenization of
sands is not significant. The new tectonic discriminant-function-based
multidimensional diagrams showed an arc setting (active) for the MN
sands and a rift setting (passive) for the CAR sands, which is
consistent with the regional geology of southern Mexico. Copyright (c)
2016 John Wiley & Sons, Ltd.
Filiaciones:
Armstrong-Altrin J.S.:
Univ Nacl Autonoma Mexico, Inst Ciencias Mar & Limnol, Unidad Proc Ocean & Costeros, Circuito Exterior S-N, Mexico City 04510, DF, Mexico
Instituto de Ciencias del Mar y Limnología, Unidad de Procesos Oceánicos y Costeros, Universidad Nacional Autónoma de México, Mexico D.F., Mexico
Lee Y.I.:
Seoul Natl Univ, Sch Earth & Environm Sci, Seoul, South Korea
School of Earth and Environmental Sciences, Seoul National University, Seoul, South Korea
Kasper-Zubillaga J.J.:
Univ Nacl Autonoma Mexico, Inst Ciencias Mar & Limnol, Unidad Proc Ocean & Costeros, Circuito Exterior S-N, Mexico City 04510, DF, Mexico
Instituto de Ciencias del Mar y Limnología, Unidad de Procesos Oceánicos y Costeros, Universidad Nacional Autónoma de México, Mexico D.F., Mexico
Trejo-Ramírez E.:
Univ Autonoma Estado Hidalgo, Area Acad Ciencias Tierra & Mat, Ingn Geol Ambiental, Pachuca, Mexico
Licenciatura en Ingeniería en Geología Ambiental, Área Académica de Ciencias de la Tierra y Materiales, Universidad Autónoma del Estado de Hidalgo, Pachuca, Mexico
|