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Geochronology of the basement rocks, Amazonas Territory, Venezuela and the tectonic evolution of the western Guiana Shield

Journal Article:

Abstract

The Amazonas Territory of Venezuela is a large area of Precambrian basement rocks overlain in some locales by the supracrustal sedimentary and volcanic rocks of the Roraima Formation. The basement rocks are medium to high grade gneisses with both igneous and sedimentary protoliths, plutonic rocks ranging in composition from granite to tonalite, and meta-volcanic rocks. Rb-Sr whole rock, and U-Pb isotopic analyses of zircons indicate a period of medium to high grade metamorphism and intrusion from 1860 to 1760 Ma. Post-tectonic plutonic activity continued to 1550 Ma. The volcanic rocks of the Roraima Formation in Venezuela give an age of 1746 Ma comparable to volcanic rocks of the Roraima Formation in other parts of the Guiana Shield. The ages and distribution of the basement rocks suggest the presence of a tectonic zone, approximately coincident with the Venezuelan-Colombian border, representing an active orogenic boundary between distinct tectonic provinces. The rocks to the northeast of this zone are part of the Trans-Amazonian of the Guiana Shield, while to the southwest and in adjacent Brazil and Colombia, new younger continental crust has been developed and cratonized. We suggest a model of collision and subduction followed by a chan0140n tectonic style to extensional-vertical to  More>>
Publication Date:
Jan 01, 1985
Product Type:
Journal Article
Reference Number:
AIX-18-054838; EDB-87-127652
Resource Relation:
Journal Name: Geol. Mijnbouw; (Netherlands); Journal Volume: 64:2
Subject:
58 GEOSCIENCES; 54 ENVIRONMENTAL SCIENCES; VENEZUELA; GEOLOGIC HISTORY; ISOTOPE DATING; GNEISSES; IGNEOUS ROCKS; ISOTOPE RATIO; LEAD; PLUTONIC ROCKS; RUBIDIUM; SEDIMENTARY ROCKS; STRONTIUM; TECTONICS; URANIUM; ZIRCON; ACTINIDES; AGE ESTIMATION; ALKALI METALS; ALKALINE EARTH METALS; DEVELOPING COUNTRIES; ELEMENTS; LATIN AMERICA; METALS; METAMORPHIC ROCKS; MINERALS; OXYGEN COMPOUNDS; ROCKS; SILICATE MINERALS; SILICATES; SILICON COMPOUNDS; SOUTH AMERICA; TRANSITION ELEMENT COMPOUNDS; ZIRCONIUM COMPOUNDS; ZIRCONIUM SILICATES; 580100* - Geology & Hydrology- (-1989); 510101 - Environment, Terrestrial- Basic Studies- Radiometric Techniques- (-1989)
OSTI ID:
6469659
Research Organizations:
New Hampshire Univ., Durham, USA. Dept. of Earth Sciences
Country of Origin:
Netherlands
Language:
English
Other Identifying Numbers:
Journal ID: CODEN: GEMIA
Submitting Site:
INIS
Size:
Pages: 131-143
Announcement Date:

Journal Article:

Citation Formats

Gaudette, H E, and Olszewski, Jr, W J. Geochronology of the basement rocks, Amazonas Territory, Venezuela and the tectonic evolution of the western Guiana Shield. Netherlands: N. p., 1985. Web.
Gaudette, H E, & Olszewski, Jr, W J. Geochronology of the basement rocks, Amazonas Territory, Venezuela and the tectonic evolution of the western Guiana Shield. Netherlands.
Gaudette, H E, and Olszewski, Jr, W J. 1985. "Geochronology of the basement rocks, Amazonas Territory, Venezuela and the tectonic evolution of the western Guiana Shield." Netherlands.
@misc{etde_6469659,
title = {Geochronology of the basement rocks, Amazonas Territory, Venezuela and the tectonic evolution of the western Guiana Shield}
author = {Gaudette, H E, and Olszewski, Jr, W J}
abstractNote = {The Amazonas Territory of Venezuela is a large area of Precambrian basement rocks overlain in some locales by the supracrustal sedimentary and volcanic rocks of the Roraima Formation. The basement rocks are medium to high grade gneisses with both igneous and sedimentary protoliths, plutonic rocks ranging in composition from granite to tonalite, and meta-volcanic rocks. Rb-Sr whole rock, and U-Pb isotopic analyses of zircons indicate a period of medium to high grade metamorphism and intrusion from 1860 to 1760 Ma. Post-tectonic plutonic activity continued to 1550 Ma. The volcanic rocks of the Roraima Formation in Venezuela give an age of 1746 Ma comparable to volcanic rocks of the Roraima Formation in other parts of the Guiana Shield. The ages and distribution of the basement rocks suggest the presence of a tectonic zone, approximately coincident with the Venezuelan-Colombian border, representing an active orogenic boundary between distinct tectonic provinces. The rocks to the northeast of this zone are part of the Trans-Amazonian of the Guiana Shield, while to the southwest and in adjacent Brazil and Colombia, new younger continental crust has been developed and cratonized. We suggest a model of collision and subduction followed by a chan0140n tectonic style to extensional-vertical to produce the basement rocks of the western Guiana Shield in the Amazonas Territory. (Auth.). 20 refs.; 13 figs.; 2 tabs.}
journal = {Geol. Mijnbouw; (Netherlands)}
volume = {64:2}
journal type = {AC}
place = {Netherlands}
year = {1985}
month = {Jan}
}