Formation of native iron in sediment-contaminated magma: I. A. case study of the Hanekammen Complex on Disko Island, West Greenland

Journal Article · Mon Jan 01 00:00:00 EST 1990 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(90)90195-Q· OSTI ID:6702207

Ulff-Moller, F ^[1]

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1. Geologisk Museum, Kobenhaven (Denmark)

For the first time a compositional range of native iron bodies is described in a cogenetic series of sediment-contaminated volcanic rocks from the Tertiary West Greenland Basalt Province. The iron-bearing rocks occur in a high-level composite intrusion, the Hanekammen Complex. Reaction between a tholeiitic parent magma with >11% MgO and carbonaceous Al{sub 2}O{sub 3}-rich shale took place in a reservoir >3 km below the paleosurface and created magmatic layering with basaltic magma overlain by less dense andesitic magma. The contaminated rock series bears a strong imprint of assimilation but very little fractional crystallization, which implies that the two processes were not intimately coupled in the present in basalt and andesite form a general trend, defined by Co versus Ni concentrations, that reflects the degree of assimilation, the amount of immiscible sulfide liquid, and the degree of reduction (in order of decreasing importance). The zoning of single iron grains reflects the dynamics of their growth and, to some extent, subsequent homogenization and reaction with magma. Weakly zoned iron spherules in viscous andesite were formed and remained in situ, whereas iron grains in basalt settled through the layered magma and developed strong zoning. All iron types contain Co-rich domains (<1 mm in diameter); their conservation implies a residence time for the iron at magmatic temperatures on the order of a month or less before the emplacement in the subvolcanic intrusions.

• OSTI ID: 6702207
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Vol. 54:1; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
BASALT
CHEMICAL COMPOSITION
MINERALOGY
PETROGENESIS
MAGMA
DYNAMICS
FRACTIONATION
CONTAMINATION
CRYSTALLIZATION
GEOLOGIC MODELS
GREENLAND
IRON ORES
LAVA
SEDIMENTARY ROCKS
SEDIMENTS
IGNEOUS ROCKS
MECHANICS
ORES
PHASE TRANSFORMATIONS
ROCKS
SEPARATION PROCESSES
VOLCANIC ROCKS
580000* - Geosciences