Importance of iron-rich tholeiitic magmas at divergent plate margins; a reappraisal

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doi: 10.1130/0091-7613(1991)019<0269:IOIRTM>2.3.CO;2
Authors:Brooks, C. Kent; Larsen, Lotte Melchior; Nielsen, Troels F. D.
Author Affiliations:Primary:
Inst. Petrol., Copenhagen, Denmark
Geol. Surv. Greenland, Denmark
Volume Title:Geology (Boulder)
Source:Geology (Boulder), 19(3), p.269-272. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0091-7613
Publication Date:1991
Note:In English. 42 refs.; illus. incl. 1 table
Summary:When a tholeiitic liquid differentiates, it may give rise to either iron-poor, silica-rich (rhyolitic) differentiates or to iron-rich, silica-poor differentiates, as found in the Skaergaard intrusion. Iron-rich differentiated liquids are rare among erupted rocks, but are found in small quantities from several localities at divergent plate margins. Among the Tertiary basalts and intrusions in East Greenland, normal erupted basalts may be mixtures of primitive liquid and differentiated iron-rich liquid, which exists at depth but normally does not reach the surface because of its high density. The evolved liquids of the Skaergaard intrusion were of this kind. Data from mid-oceanic ridges confirm this view. We believe that iron-rich differentiated liquids, despite their scarcity on the surface, are much more voluminous at depth, as picrites, at the other side of the density minimum attained during liquid evolution, are thought to be. The trend toward iron enrichment develops when the tholeiitic magma differentiates in a closed system at a relatively low oxidation state, whereas the trend toward silica enrichment and iron depletion occurs when the magma has interacted with the oxidized and hydrated surroundings in the crust.
Subjects:Basalts; Cenozoic; Composition; Differentiation; Enrichment; Genesis; Geochemistry; Igneous rocks; Intrusions; Iron; Iron-rich composition; Layered intrusions; Magmas; Metals; Petrology; Picrite; Plate boundaries; Plate divergence; Plate tectonics; Processes; Sea-floor spreading; Tertiary; Tholeiitic composition; Ultramafic composition; Volcanic rocks; Arctic region; East Greenland; Greenland; Skaergaard Intrusion; Igneous activity
Abstract Numbers:91M/4715
Record ID:1991016927
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute.
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