Mineralogy and geochemistry of the Lower Cretaceous siliciclastic rocks of the Morita Formation, Sierra San Jose section, Sonora, Mexico
Por:
Madhavaraju, J., Pacheco-Olivas, S. A., Gonzalez-Leon, Carlos M., Espinoza-Maldonado, Inocente G., Sanchez-Medrano, P. A., Villanueva-Amadoz, U., Monreal, Rogelio, Pi-Puig, T., Ramirez-Montoya, Erik, Grijalva-Noriega, Francisco J.
Publicada:
1 jul 2017
Resumen:
Clay mineralogy and geochemical studies were carried out on sandstone
and shale samples collected from the Sierra San Jose section of the
Morita Formation to infer the paleoclimate and paleoweathering
conditions that prevailed in the source region during the deposition of
these sediments. The clay mineral assemblages (fraction < 2 mu m) of the
Sierra San Jose section are composed of chlorite and illite. The
abundance of illite and chlorite in the studied samples suggest that the
physical weathering conditions were dominant over chemical weathering.
Additionally, the illite and chlorite assemblages reflect arid or
semi-arid climatic conditions in the source regions. K2O/Al2O3 ratio of
shales vary between 0.15 and 0.26, which lie in the range of values for
clay minerals, particularly illite composition. Likewise, sandstones
vary between 0.06 and 0.13, suggesting that the clay minerals are mostly
kaolinte and illite types. On the chondrite-normalized diagrams,
sandstone and shale samples show enriched light rare earth elements
(LREE), flat heavy rare earth elements (HREE) patterns and negative Eu
anomalies. The CIA and PIA values and A-CN-K plot of shales indicate low
to moderate degree of weathering in the source regions. However, the
sandstones have moderate to high values of CIA and PIA suggesting a
moderate to intense weathering in the source regions. The SiO2/Al2O3
ratios, bivariate and ternary plots, discriminant function diagram and
elemental ratios indicate the felsic source rocks for sandstone and
shale of the Morita Formation. (C) 2017 Elsevier Ltd. All rights
reserved.
Filiaciones:
Madhavaraju, J.:
Univ Nacl Autonoma Mexico, Inst Geol, Estn Reg Noroeste, Hermosillo, Sonora 83000, Mexico
Pacheco-Olivas, S. A.:
Univ Sonora, Dept Geol, Hermosillo, Sonora 83000, Mexico
Gonzalez-Leon, Carlos M.:
Univ Nacl Autonoma Mexico, Inst Geol, Estn Reg Noroeste, Hermosillo, Sonora 83000, Mexico
Espinoza-Maldonado, Inocente G.:
Univ Sonora, Dept Geol, Hermosillo, Sonora 83000, Mexico
Sanchez-Medrano, P. A.:
Univ Sonora, Dept Geol, Hermosillo, Sonora 83000, Mexico
Villanueva-Amadoz, U.:
Univ Nacl Autonoma Mexico, Inst Geol, Estn Reg Noroeste, Hermosillo, Sonora 83000, Mexico
Monreal, Rogelio:
Univ Sonora, Dept Geol, Hermosillo, Sonora 83000, Mexico
Pi-Puig, T.:
Univ Nacl Autonoma Mexico, Inst Geol, Mexico City 04510, DF, Mexico
Ramirez-Montoya, Erik:
Univ Sonora, Dept Geol, Hermosillo, Sonora 83000, Mexico
Grijalva-Noriega, Francisco J.:
Univ Sonora, Dept Geol, Hermosillo, Sonora 83000, Mexico
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