Trace elements in natural metallic iron from Disko Island, Greenland

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Authors:Klöck, W.; Palme, H.; Tobschall, H. J.
Author Affiliations:Primary:
Max-Planck-Inst. Chem., Abt. Kosmochem., D-6500 Mainz, Federal Republic of Germany
Volume Title:Contributions to Mineralogy and Petrology
Source:Contributions to Mineralogy and Petrology, 93(3), p.273-282. Publisher: Springer International, Heidelberg-New York, International. ISSN: 0010-7999
Publication Date:1986
Note:In English. 43 refs.; illus. incl. 5 tables, geol. sketch map
Summary:The largest occurrence of natural metallic Fe on Earth is on Disko Island. Three different types of metallic Fe were studied: 1) metal spherules <300 mu m in basaltic magma; 2) metal grains, 300 mu m-3 mm, often composed of aggregates of smaller particles, in similar host rocks; and 3) massive Fe lumps = or < several tonnes. Analytical data for 13 siderophile elements are presented. All three types show distinctly crustal patterns, high Co/Ni, Re/Ir or W/Ir ratios, demonstrating that a meteoritic origin for the metallic Fe must be excluded. Since the Co/Ni and Re/Ir ratios are approx chondritic in the upper mantle, a mantle origin for the Disko metals can also be ruled out. This supports earlier petrological and geological evidence that the metallic Fe was formed through reduction of basaltic magma by C derived from Tertiary shales and coals. Significant differences in absolute and relative abundances of siderophile elements occur among the three kinds of Fe. Strongly siderophile elements, e.g. Ir, Re, Ni increase in concentration from the small metal spherules through the larger grains to the massive Fe lumps. The contents of less strongly siderophile elements (P, W, Ga) decrease in the same sequence. It is concluded that the small spherules are formed in situ. Larger grains and lumps are composed of small spherules, accumulated by gravitational settling in a magma reservoir. The metal cumulates have extracted highly siderophile elements from a larger volume of basaltic melt. Analyses of 11 minerals associated with metal particles, major- and trace-element analyses of 3 metal-bearing Disko andesites, average trace-element abundances in 3 metals, and averages of C, S and P data of Disko metals and silicates are presented. [P.Br.]
Subjects:Geochemistry; Iron; Major elements; Metals; Native elements; Trace elements; Arctic region; Disko Island; Greenland
Abstract Numbers:87M/2619
Record ID:1988002740
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom, Reference includes data from Geoline, Bundesanstalt fur Geowissenschaften und Rohstoffe
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