Petrology of the Cerro Morado basic magmatism in the Ischigualasto-Villa Unión triassic basin (NW Argentine)

Studies carried out in Cerro Morado, situated in the Ischigualasto - Vale de la Luna Provincial Park (northernmost San Juan Province - Argentina), have allowed the identification and characterization of silica undersaturated hypabyssal alkaline basic rocks. This magmatism is probably related to an e...

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Detalles Bibliográficos
Autores principales: Alexandre, F.M., Sommer, C.A., De Lima, E.F., Chemale Jr., F., Marsicano, C.A., Mancuso, A.C., Brod, J.A.
Formato: JOUR
Materias:
NW Argentine
Petrology
Sill
Undersaturated rocks
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_15182398_v36_n3_p295_Alexandre
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id todo:paper_15182398_v36_n3_p295_Alexandre
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spelling todo:paper_15182398_v36_n3_p295_Alexandre2023-10-03T16:19:54Z Petrology of the Cerro Morado basic magmatism in the Ischigualasto-Villa Unión triassic basin (NW Argentine) Alexandre, F.M. Sommer, C.A. De Lima, E.F. Chemale Jr., F. Marsicano, C.A. Mancuso, A.C. Brod, J.A. NW Argentine Petrology Sill Undersaturated rocks Studies carried out in Cerro Morado, situated in the Ischigualasto - Vale de la Luna Provincial Park (northernmost San Juan Province - Argentina), have allowed the identification and characterization of silica undersaturated hypabyssal alkaline basic rocks. This magmatism is probably related to an extensional reactivation of Paleozoic lineaments due to the breakup of the Gondwana supercontinent. The Cerro Morado hypabyssal rocks occur as a conformable body intrusive in sedimentary rocks of the Chãares Formation (Middle Triassic) of the Ischigualasto - Villa Unión Triassic Basin. The basal portion of the sill is formed by olivinebearing, dominantly porphyritic diabase, where plagioclase, clinopyroxene, and rare olivine phenocrysts are set in a hypocrystalline, fine-grained matrix of the same composition, plus opaque minerals, apatite and glass. Trachytic, intergranular and ophitic textures are also common. The intermediate and upper portions comprise mainly porphyritic tephrytic rocks, with plagioclase, feldspathoid, and clino-pyroxene phenocrysts set in a fine-grained matrix of the same composition. Chemical classifica-tions of the Cerro Morado rocks must be applied with care, due to their high L.O.I values. The behavior of major and trace elements suggests that mineral fractionation was the main magmatic differentiation process. The LILE, HFSE and REE contents are very similar to those of intra-plate alkaline basalts. The high LILE and HFSE contents, associated to incompatible element-ratios suggest a heterogeneous and enriched mantle source. The enrichment in Sr, K, Rb, and Ba may result from modification of a mantle source by aqueous fluids driven off the subducted oceanic crust. Rb-Sr and Sm-Nd preliminary data suggest mantle sources, including a HIMU isotopic reservoir, and minor influence of an enriched-mantle component. Fil:Marsicano, C.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Mancuso, A.C. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_15182398_v36_n3_p295_Alexandre
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic NW Argentine
Petrology
Sill
Undersaturated rocks
spellingShingle NW Argentine
Petrology
Sill
Undersaturated rocks
Alexandre, F.M.
Sommer, C.A.
De Lima, E.F.
Chemale Jr., F.
Marsicano, C.A.
Mancuso, A.C.
Brod, J.A.
Petrology of the Cerro Morado basic magmatism in the Ischigualasto-Villa Unión triassic basin (NW Argentine)
topic_facet NW Argentine
Petrology
Sill
Undersaturated rocks
description Studies carried out in Cerro Morado, situated in the Ischigualasto - Vale de la Luna Provincial Park (northernmost San Juan Province - Argentina), have allowed the identification and characterization of silica undersaturated hypabyssal alkaline basic rocks. This magmatism is probably related to an extensional reactivation of Paleozoic lineaments due to the breakup of the Gondwana supercontinent. The Cerro Morado hypabyssal rocks occur as a conformable body intrusive in sedimentary rocks of the Chãares Formation (Middle Triassic) of the Ischigualasto - Villa Unión Triassic Basin. The basal portion of the sill is formed by olivinebearing, dominantly porphyritic diabase, where plagioclase, clinopyroxene, and rare olivine phenocrysts are set in a hypocrystalline, fine-grained matrix of the same composition, plus opaque minerals, apatite and glass. Trachytic, intergranular and ophitic textures are also common. The intermediate and upper portions comprise mainly porphyritic tephrytic rocks, with plagioclase, feldspathoid, and clino-pyroxene phenocrysts set in a fine-grained matrix of the same composition. Chemical classifica-tions of the Cerro Morado rocks must be applied with care, due to their high L.O.I values. The behavior of major and trace elements suggests that mineral fractionation was the main magmatic differentiation process. The LILE, HFSE and REE contents are very similar to those of intra-plate alkaline basalts. The high LILE and HFSE contents, associated to incompatible element-ratios suggest a heterogeneous and enriched mantle source. The enrichment in Sr, K, Rb, and Ba may result from modification of a mantle source by aqueous fluids driven off the subducted oceanic crust. Rb-Sr and Sm-Nd preliminary data suggest mantle sources, including a HIMU isotopic reservoir, and minor influence of an enriched-mantle component.
format JOUR
author Alexandre, F.M.
Sommer, C.A.
De Lima, E.F.
Chemale Jr., F.
Marsicano, C.A.
Mancuso, A.C.
Brod, J.A.
author_facet Alexandre, F.M.
Sommer, C.A.
De Lima, E.F.
Chemale Jr., F.
Marsicano, C.A.
Mancuso, A.C.
Brod, J.A.
author_sort Alexandre, F.M.
title Petrology of the Cerro Morado basic magmatism in the Ischigualasto-Villa Unión triassic basin (NW Argentine)
title_short Petrology of the Cerro Morado basic magmatism in the Ischigualasto-Villa Unión triassic basin (NW Argentine)
title_full Petrology of the Cerro Morado basic magmatism in the Ischigualasto-Villa Unión triassic basin (NW Argentine)
title_fullStr Petrology of the Cerro Morado basic magmatism in the Ischigualasto-Villa Unión triassic basin (NW Argentine)
title_full_unstemmed Petrology of the Cerro Morado basic magmatism in the Ischigualasto-Villa Unión triassic basin (NW Argentine)
title_sort petrology of the cerro morado basic magmatism in the ischigualasto-villa unión triassic basin (nw argentine)
url http://hdl.handle.net/20.500.12110/paper_15182398_v36_n3_p295_Alexandre
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