Oxygen isotope geochemistry of the silicic volcanic rocks of the Etendeka-Parana province: Source constraints

Journal Article · Wed Oct 31 23:00:00 EST 1990 · Geology; (USA)

DOI:https://doi.org/10.1130/0091-7613(1990)018<1119:OIGOTS>2.3.CO;2· OSTI ID:5572867

Harris, C; Milner, S C; Armstrong, R A ^[1]; Whittingham, A M ^[2]

---

1. Univ. of Cape Town, Rondebosch (South Africa)
2. Univ. of Oxford (England)

Oxygen isotope ratios of pyroxene phenocrysts in the silicic volcanic rocks from the Cretaceous Etendeka-Parana flood basalt province (Namibia, South America) are believed to reflect the {delta}{sup 18}O values of the original magmas. The authors recognize a high {delta}{sup 18}O value type ({delta}{sup 18}O pyroxene {approximately} +10{per thousand}) found in the south of both regions, and a low {delta}{sup 18}O value type ({delta}{sup 18}O pyroxene {approximately} +6.5{per thousand}) found in the north. Other differences between thee two rhyolite types include higher concentrations of incompatible elements and lower initial {sup 87}Sr/{sup 86}Sr ratios in the low {delta}{sup 18}O value type. The authors suggest that the regional distribution of rhyolite types reflects differences in source composition, which can best be explained if the sources are lower crustal, Late Proterozoic mobile belt material (high {delta}{sup 18}O) and Archean lower crust (low {delta}{sup 18}O).

• OSTI ID: 5572867
• Journal Information: Geology; (USA), Journal Name: Geology; (USA) Vol. 18:11; ISSN GLGYB; ISSN 0091-7613
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
AFRICA
ALKALINE EARTH ISOTOPES
BETA DECAY RADIOISOTOPES
CHEMISTRY
CONTINENTAL CRUST
CRETACEOUS PERIOD
EARTH CRUST
ELECTRON CAPTURE RADIOISOTOPES
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
GEOCHEMISTRY
GEOLOGIC AGES
HOURS LIVING RADIOISOTOPES
IGNEOUS ROCKS
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
LIGHT NUCLEI
MAGMA
MEASURING METHODS
MESOZOIC ERA
MINERALS
NAMIBIA
NUCLEI
ORIGIN
OXYGEN 18
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
PYROXENES
RADIOISOTOPES
RHYOLITES
ROCKS
SAMPLING
SILICATES
SILICON COMPOUNDS
SOURCE ROCKS
STABLE ISOTOPES
STRONTIUM 86
STRONTIUM 87
STRONTIUM ISOTOPES
VOLCANIC REGIONS
VOLCANIC ROCKS