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Geology and geochronology of Cardoso Island, in the southeastern coast of Sao Paulo State; Geologia e geocronologia da Ilha de Cardoso, sudeste do Estado de Sao Paulo

Abstract

This aim of work is the geological and geochronological study of rocks cropping out on Cardoso Island, on the southeastern coast of Sao Paulo States, close to be boundary with Parana State. The Island with an area of about 151 km{sup 2} is a protected area administered by the Forest Institute of Environment Secretariat of the State of Sao Paulo. It is mountanious, with a peak at 814 m, and is covered by dense Mata Atlantica vegetation. The terrains which compose the island are mainly an igneous complex with light grey leucocratic, inequigranular, medium - to coarse-grained syenites. The predominant Tres Irmaos Syenite (STI), composed of pyroxene, hornblende, and perthitic to mesoperthitic microcline, has a magmatic flow structures, and is cut by the Cambriu alkali-feldspar Granites (GC), which is pinkish grey, leucocratic and medium-grained. Geochemical analysis of STI and GC demonstrate their meta luminous alkaline nature and late-orogenic to an orogenic character. The geochronological results suggest that the bodies were formed between 620 and 570 My according to the U-Pb method in zircons, with cooling between 597 and 531 My (K-Ar in amphiboles). Whole rock Sm-Nd analysis yield T{sub DM} ages in the Meso and Paleoproterozoic (1.200 - 2.200 My).  More>>
Authors:
Publication Date:
Jul 01, 1998
Product Type:
Thesis/Dissertation
Report Number:
INIS-BR-3828
Resource Relation:
Other Information: TH: Dissertacao (M.Sc.); 89 refs., 33 figs., 24 photos; PBD: 1998
Subject:
58 GEOSCIENCES; ARGON ISOTOPES; BRAZIL; GEOCHEMICAL SURVEYS; IGNEOUS ROCKS; ISOTOPE DATING; ISOTOPE RATIO; LEAD ISOTOPES; MAPS; NEODYMIUM ISOTOPES; POTASSIUM; RARE EARTHS; RUBIDIUM ISOTOPES; SAMARIUM ISOTOPES; STRONTIUM ISOTOPES; URANIUM ISOTOPES
OSTI ID:
20399674
Research Organizations:
Sao Paulo Univ., SP (Brazil). Inst. de Geociencias
Country of Origin:
Brazil
Language:
Portuguese
Other Identifying Numbers:
TRN: BR0343051073709
Availability:
Available from INIS in electronic form
Submitting Site:
BRN
Size:
132 pages
Announcement Date:

Citation Formats

Weber, Werner. Geology and geochronology of Cardoso Island, in the southeastern coast of Sao Paulo State; Geologia e geocronologia da Ilha de Cardoso, sudeste do Estado de Sao Paulo. Brazil: N. p., 1998. Web.
Weber, Werner. Geology and geochronology of Cardoso Island, in the southeastern coast of Sao Paulo State; Geologia e geocronologia da Ilha de Cardoso, sudeste do Estado de Sao Paulo. Brazil.
Weber, Werner. 1998. "Geology and geochronology of Cardoso Island, in the southeastern coast of Sao Paulo State; Geologia e geocronologia da Ilha de Cardoso, sudeste do Estado de Sao Paulo." Brazil.
@misc{etde_20399674,
title = {Geology and geochronology of Cardoso Island, in the southeastern coast of Sao Paulo State; Geologia e geocronologia da Ilha de Cardoso, sudeste do Estado de Sao Paulo}
author = {Weber, Werner}
abstractNote = {This aim of work is the geological and geochronological study of rocks cropping out on Cardoso Island, on the southeastern coast of Sao Paulo States, close to be boundary with Parana State. The Island with an area of about 151 km{sup 2} is a protected area administered by the Forest Institute of Environment Secretariat of the State of Sao Paulo. It is mountanious, with a peak at 814 m, and is covered by dense Mata Atlantica vegetation. The terrains which compose the island are mainly an igneous complex with light grey leucocratic, inequigranular, medium - to coarse-grained syenites. The predominant Tres Irmaos Syenite (STI), composed of pyroxene, hornblende, and perthitic to mesoperthitic microcline, has a magmatic flow structures, and is cut by the Cambriu alkali-feldspar Granites (GC), which is pinkish grey, leucocratic and medium-grained. Geochemical analysis of STI and GC demonstrate their meta luminous alkaline nature and late-orogenic to an orogenic character. The geochronological results suggest that the bodies were formed between 620 and 570 My according to the U-Pb method in zircons, with cooling between 597 and 531 My (K-Ar in amphiboles). Whole rock Sm-Nd analysis yield T{sub DM} ages in the Meso and Paleoproterozoic (1.200 - 2.200 My). belt of low grade meta sedimentary rocks occurs in the northern part of the island. Quartz schist, quartz-mica schist and mica-quartz schist, often containing andaluzite and cordierite, predominate. The geochemical and geochronological data suggest that the sources of the metasediments were andesites of continental arc whose protolities separated from the mantle during the Paleoproterozoic, between 1.800 and 2.200 My. These metasediments probably continue on the continent in the Taquari region and extend southwards in narrow strips between the granitoids of the Paranagua Domain. Although quaternary deposits are expressive, they were not studied in details since they were not the objectives of this study. (author)}
place = {Brazil}
year = {1998}
month = {Jul}
}