Published January 1989 | Version v1
Journal article Metadata-only

Petrological and geochemical studies of alkaline rocks from continental Brazil. 8. The syenitic intrusion of Morro Redondo, RJ

Creators

  • 1. Napoli Univ. (Italy). Dipt. di Scienze della Terra
  • 2. Ferrara Univ. (Italy). Ist. di Mineralogia

Description

The alkaline complex of Morro Redondo is mainly composed of syenites, alkali syenites and nepheline syenites. The age of the intrusion, utilizing eleven newly available K/Ar data, is about 73 Ma. Petrography, mineral chemistry and geochemistry strongly support cogeneticity among the various lithotypes, linked by fractional crystallisation of the observed phases and crystal accumulation, preferentially of alkali feldspar. Initial Sr isotopic ratios indicate a mantle parental magma, probably generated in the subcontinental lithosphere, like other Brazilian alkaline complexes (e.g. Fortaleza, Juquia, Piratini, Tunas). (author)

Abstract (Portuguese)

O complexo alcalino de Morro Redondo e constituido essencialmente de sienitos, alcali sienitos e nefelina sienitos. Onze determinacoes K/Ar recentemente obtidas indicam para a intrusao idade de 73 Ma. Evidencias petrograficas, de quimica mineral e geoquimicas sao fortemente indicativas do carater cogenetico dos varios tipos litologicos encontrados, com a sua formacao se dando por cristalizacao fracionada das fases observadas e acumulacao de cristais, preferencialmente de feldspato alcalino. Razoes isotopicas iniciais de Sr apontam para a natureza mantelica do magma parental dessas rochas, provavelmente gerado na litosfera subcontinental, a exemplo do sucedido com outros complexos alcalinos brasileiros (Fortaleza, Juquia, Piratini, Tunas)

Additional details

Publishing Information

Journal Title
Geochimica Brasiliensis
Journal Volume
3
Journal Issue
1
Series
Geochim. Bras.
Journal Page Range
63-80
ISSN
0102-9800
CODEN
GEBRE

INIS

Country of Publication
Brazil
Country of Input or Organization
Brazil
INIS RN
21039562
Subject category
S54: ENVIRONMENTAL SCIENCES; S37: INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY;
Resource subtype / Literary indicator
Numerical Data
Descriptors DEI
AGE ESTIMATION; ARGON; BRAZIL; GEOCHEMISTRY; ISOTOPE DATING; ISOTOPE RATIO; NUMERICAL DATA; PETROLOGY; POTASSIUM; STRONTIUM; SYENITES
Descriptors DEC
ALKALI METALS; ALKALINE EARTH METALS; DATA; DEVELOPING COUNTRIES; ELEMENTS; IGNEOUS ROCKS; INFORMATION; LATIN AMERICA; METALS; NONMETALS; PLUTONIC ROCKS; RARE GASES; ROCKS; SOUTH AMERICA