Oxygen-isotope exchange and mineral alteration in gabbros of the Lower Layered Series, Kap Edvard Holm Complex, East Greenland

Journal Article · Thu Aug 01 00:00:00 EDT 1991 · Geology; (United States)

DOI:https://doi.org/10.1130/0091-7613(1991)019<0819:OIEAMA>2.3.CO;2· OSTI ID:5963874

Fehlhaber, K; Bird, D K ^[1]

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1. Stanford Univ., CA (United States)

Multiple intrusions of gabbros, mafic dikes, and syenites in the Kap Edvard Holm Complex gave rise to prolonged circulation of meteoric hydrothermal solutions and extreme isotope exchange and mineral alteration in the 3,600-m-thick Lower Layered Series gabbros. In the Lower Layered Series, {delta}{sup 18}O of plagioclase varies from +0.3{per thousand} to {minus}5.8{per thousand}, and it decreases with an increase in the volume of secondary talc, chlorite, and actinolite. In the same gabbros, pyroxenes have a more restricted range in {delta}{sup 18}O, from 5.0{per thousand} to 3.8{per thousand}, and values of {delta}{sup 18}O{sub pyroxene} are independent of the abundance of secondary minerals, which ranges from 14% to 30%. These relations indicate that large amounts of water continued to flow through the rocks at temperatures of < 500-600C, altering the gabbros to assemblages of talc + chlorite + actinolite {plus minus}epidote {plus minus}albite and causing significant oxygen-isotope exchange in plagioclase, but not in pyroxene. The extensive low-temperature secondary mineralization and {sup 18}O depletion of plagioclase in the Lower Layered Series are associated with the later emplacement of dikes and gabbros and syenites, which created new fracture systems and provided heat sources for hydrothermal fluid circulation. This produced subsolidus mineral alteration and isotope exchange in the Lower Layered Series that are distinct from those in the Skaergaard and Cuillin gabbros of the North Atlantic Tertiary province, but are similar to those observed in some oceanic gabbros.

• OSTI ID: 5963874
• Journal Information: Geology; (United States), Vol. 19:8; ISSN 0091-7613
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
GABBROS
ISOTOPE RATIO
GEOLOGIC FORMATIONS
HYDROTHERMAL ALTERATION
GREENLAND
ANORTHOSITES
DIKES
GEOLOGY
ISOTOPIC EXCHANGE
METEORIC WATER
MINERALIZATION
MINERALS
OXYGEN 18
PYROXENES
RESERVOIR TEMPERATURE
EVEN-EVEN NUCLEI
GEOLOGIC STRUCTURES
GROUND WATER
HYDROGEN COMPOUNDS
IGNEOUS ROCKS
ISOTOPES
LIGHT NUCLEI
NUCLEI
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
PLUTONIC ROCKS
ROCKS
SILICATES
SILICON COMPOUNDS
STABLE ISOTOPES
WATER
580000* - Geosciences