HR: 16:50h
AN: U54A-03    [Abstracts]
TI: U-Pb zircon geochronology of Paleozoic units in Western and Central Guatemala: insights into the tectonic evolution of Middle America
AU: * Solari, L A
EM: solari@servidor.unam.mx
AF: Centro de Geociencias, UNAM, Campus Juriquilla, Queretaro, QRO 76001, Mexico
AU: Ortega-Gutierrez, F
EM: fortega@servidor.unam.mx
AF: Instituto de Geologia, UNAM, Ciudad Universitaria, Delegacion Coyoacan, Mexico City, DF 04510, Mexico
AU: Elias-Herrera, M
EM: melias@servidor.unam.mx
AF: Instituto de Geologia, UNAM, Ciudad Universitaria, Delegacion Coyoacan, Mexico City, DF 04510, Mexico
AU: Schaaf, P
EM: pschaaf@geofisica.unam.mx
AF: Instituto de Geofisica, UNAM, Ciudad Universitaria, Delegacion Coyoacan, Mexico City, DF 04510, Mexico
AU: Norman, M
EM: Marc.Norman@anu.edu.au
AF: Research School of Earth Sciences, ANU, Mills Road, Building 61, Canberra, ACT 0200, Australia
AU: Torres de Leon, R
EM: torresdeleonr@yahoo.com.mx
AF: Instituto de Geologia, UNAM, Ciudad Universitaria, Delegacion Coyoacan, Mexico City, DF 04510, Mexico
AU: Ortega-Obregon, C
EM: carloo45@gmail.com
AF: Instituto de Geologia, UNAM, Ciudad Universitaria, Delegacion Coyoacan, Mexico City, DF 04510, Mexico
AU: Moran Ical, S
EM: sergiomical@yahoo.com
AF: Centro Universitario del Norte, Universidad de San Carlos, Coban, BV , Guatemala
AU: Chiquin, M
EM: mchiquin@yahoo.com
AF: Centro Universitario del Norte, Universidad de San Carlos, Coban, BV , Guatemala
AB: Precambrian and Paleozoic basements are present in southern Mexico and Central America, where several crustal blocks are recognized by their different geologic record, and juxtaposed along lateral faults. Some of those crustal blocks are currently located between southernmost north America (the Maya block) and Central America (Chortis block).To better understand the geology of these crustal blocks, and to establish comparisons between their geologic history, U-Pb ages of both igneous and metasedimentary key units cropping out in central and western Guatemala are presented here. In the Altos Cuchumatanes (Maya block) granites yield both Permian (269 +/- 29 Ma) and Early Devonian (391 +/- 7.4 Ma) U-Pb ages. LA-ICPMS detrital zircon ages from rocks of the San Gabriel sequence, interpreted as the oldest metasedimentary unit of the Maya block, and overlain by the Late Paleozoic Upper Santa Rosa Group, yield Precambrian detrital zircons bracketed between 920 Ma and 1,000 Ma. The presence of these metasedimentary units, as well as Early Devonian to Silurian granites in the Mayan continental margin, from west (Altos Cuchumatanes), to east (Maya Mountains of Belize) indicate a more or less continuous belt of Lower Paleozoic igneous activity, also suggesting that the continental margin of the Maya block can be extended south of the Polochic fault, up to the Baja Verapaz shear zone. A metasedimentary sample belonging to the Chuacus Complex yielded detrital zircons with ages between 440 Ma and 1,325 Ma. The younger ages are similar to the igneous ages reported from the entire southern Maya continental margin, and show proximity of the Complex in the Middle-Late Palaeozoic. The S. Diego Phyllite, which overlies high-grade basement units of the Chortis block, contains zircons that are Lower Cambrian (538 Ma), Mesoproterozoic (980 to 1,150 Ma) and even Paleoproterozoic (1,820 Ma). Absence of younger igneous zircons in the San Diego Phyllite indicates that either its sedimentation took place in a close range of time, during the Late Cambrian, or absence of connection between Chortis and Maya blocks during the Early-Mid Palaeozoic. The Precambrian zircons could have come from southern Mexico (Oaxaca and Guichicovi Complexes), or from Mesoprterozoic Massifs exposed in Laurentia and Gondwana. Paleogeographic models for Middle America are limited to post-Jurassic time. The data presented here shed light on Paleozoic and, possibly, Precambrian relationships. They indicate that Maya and the Chortis did not interact directly until the Mesozoic or Cenozoic, as they approached their current position.
DE: 1100 GEOCHRONOLOGY
DE: 3660 Metamorphic petrology
DE: 8104 Continental margins: convergent
DE: 8110 Continental tectonics: general (0905)
DE: 8157 Plate motions: past (3040)
SC: Union [U]
MN: 2007 Joint Assembly