The relationships between volcanism and extension in the Mesa Central: the case of Pinos, Zacatecas, Mexico
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| Format: | Artículo científico |
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Universidad Nacional Autónoma de México
2007
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| author | Roberto Molina Garza |
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| contents | The relationships between volcanism and extension in the Mesa Central: the case of Pinos, Zacatecas, Mexico Roberto Molina Garza Luis Fernando Vassallo Morales María Amabel Ortega Rivera José Gregorio Solorio Munguía José Jorge Aranda Gómez Fred W. McDowell Alfredo Aguillón Robles Ciencias de la Tierra Pinos Mexico red beds Extension volcanism Pinos volcanic complex is an uplifted area that exposes Mesozoic strata and mid-Tertiary volcanicand sedimentary rocks. Its stratigraphy, deformation style, and volcanism are characteristic of the MesaCentral region of central Mexico and the southeastern segment of the Sierra Madre Occidental (SMO)volcanic province. The oldest rocks in Pinos are marine carbonate sedimentary and siliciclastic rocksthat underlie a red bed sequence (Pinos red beds) interlayered with felsic volcanic rocks, in turn partiallycovered by a voluminous lava dome complex. The Pinos red bed sequence is at least 900 m thick andit is formed by well-lithifi ed conglomeratic sandstone and matrix-supported, generally fi ne-grained tomedium-grained, polymictic conglomerate. Clasts in the Pinos red beds were derived from the Mesozoicbasement, subaerial felsic volcanic rocks of unknown provenance, and tourmaline-bearing muscovitegranite. Interlayered volcanic rocks include ash-fall tuffs, a densely welded ash-fl ow tuff, and water-laidor reworked pyroclastic material. The main components of the dome complex are a dark-red, porphyriticpotassium-rich trachyte, and a buff-colored, porphyritic rhyolite, for which we report lava mingling (thefirst one in the SMO volcanic province). Field relations at the Pinos volcanic complex demonstrate aclose temporal relationship between felsic volcanism and extension. Faulting in Pinos is complex as itincludes arrays of Cenozoic normal faults with NS, NW, and NE trends, for which cross-cutting relationsare ambiguous. A combination of mapping, K-Ar geochronology, petrographic work and interpretationof the magnetic polarity of the volcanic units allow us to establish that repeated pulses of synextensionalvolcanism occurred during the period between ~32 and 27 Ma. These data demonstrate that extensionin the Mesa Central is older than 2927 Ma, the oldest previously recognized episode of extension.The earliest (≥ 32 Ma) pulse of extension may be related to a regional (~250 km long) NW-trendingfault system that divides the Mesa Central into two domains with contrasting stratigraphy and differentgeomorphic aspect. The Pinos red bed sequence includes clasts of the Peñón Blanco granite (40Ar/39Ar= 50.94 ± 0.47 Ma), that in addition to providing a minimum age for the end of the Laramide orogenyin the Mesa Central, offers evidence of uplift and denudation of the granite before or synchronous withred bed deposition 2007 artículo científico 1026-8774 https://www.redalyc.org/articulo.oa?id=57224207 en http://www.redalyc.org/revista.oa?id=572 Revista Mexicana de Ciencias Geológicas application/pdf Universidad Nacional Autónoma de México Revista Mexicana de Ciencias Geológicas (México) Num.2 Vol.24 |
| format | Artículo científico |
| id | redalyc_57224207 |
| institution | Redalyc |
| language | en |
| publishDate | 2007 |
| publisher | Universidad Nacional Autónoma de México |
| spellingShingle | The relationships between volcanism and extension in the Mesa Central: the case of Pinos, Zacatecas, Mexico Roberto Molina Garza Ciencias de la Tierra Pinos Mexico red beds Extension volcanism The relationships between volcanism and extension in the Mesa Central: the case of Pinos, Zacatecas, Mexico Roberto Molina Garza Luis Fernando Vassallo Morales María Amabel Ortega Rivera José Gregorio Solorio Munguía José Jorge Aranda Gómez Fred W. McDowell Alfredo Aguillón Robles Ciencias de la Tierra Pinos Mexico red beds Extension volcanism Pinos volcanic complex is an uplifted area that exposes Mesozoic strata and mid-Tertiary volcanicand sedimentary rocks. Its stratigraphy, deformation style, and volcanism are characteristic of the MesaCentral region of central Mexico and the southeastern segment of the Sierra Madre Occidental (SMO)volcanic province. The oldest rocks in Pinos are marine carbonate sedimentary and siliciclastic rocksthat underlie a red bed sequence (Pinos red beds) interlayered with felsic volcanic rocks, in turn partiallycovered by a voluminous lava dome complex. The Pinos red bed sequence is at least 900 m thick andit is formed by well-lithifi ed conglomeratic sandstone and matrix-supported, generally fi ne-grained tomedium-grained, polymictic conglomerate. Clasts in the Pinos red beds were derived from the Mesozoicbasement, subaerial felsic volcanic rocks of unknown provenance, and tourmaline-bearing muscovitegranite. Interlayered volcanic rocks include ash-fall tuffs, a densely welded ash-fl ow tuff, and water-laidor reworked pyroclastic material. The main components of the dome complex are a dark-red, porphyriticpotassium-rich trachyte, and a buff-colored, porphyritic rhyolite, for which we report lava mingling (thefirst one in the SMO volcanic province). Field relations at the Pinos volcanic complex demonstrate aclose temporal relationship between felsic volcanism and extension. Faulting in Pinos is complex as itincludes arrays of Cenozoic normal faults with NS, NW, and NE trends, for which cross-cutting relationsare ambiguous. A combination of mapping, K-Ar geochronology, petrographic work and interpretationof the magnetic polarity of the volcanic units allow us to establish that repeated pulses of synextensionalvolcanism occurred during the period between ~32 and 27 Ma. These data demonstrate that extensionin the Mesa Central is older than 2927 Ma, the oldest previously recognized episode of extension.The earliest (≥ 32 Ma) pulse of extension may be related to a regional (~250 km long) NW-trendingfault system that divides the Mesa Central into two domains with contrasting stratigraphy and differentgeomorphic aspect. The Pinos red bed sequence includes clasts of the Peñón Blanco granite (40Ar/39Ar= 50.94 ± 0.47 Ma), that in addition to providing a minimum age for the end of the Laramide orogenyin the Mesa Central, offers evidence of uplift and denudation of the granite before or synchronous withred bed deposition 2007 artículo científico 1026-8774 https://www.redalyc.org/articulo.oa?id=57224207 en http://www.redalyc.org/revista.oa?id=572 Revista Mexicana de Ciencias Geológicas application/pdf Universidad Nacional Autónoma de México Revista Mexicana de Ciencias Geológicas (México) Num.2 Vol.24 |
| title | The relationships between volcanism and extension in the Mesa Central: the case of Pinos, Zacatecas, Mexico |
| topic | Ciencias de la Tierra Pinos Mexico red beds Extension volcanism |
| url | https://www.redalyc.org/articulo.oa?id=57224207 |