Textural maturity of cumulates; a record of chamber filling, liquidus assemblage cooling rate and large-scale convection in mafic layered intrusions

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doi: 10.1093/petrology/eg1057
Authors:Holness, Marian B.; Nielsen, Troels F.; Tegner, Christian
Author Affiliations:Primary:
University of Cambridge, Department of Earth Sciences, Cambridge, United Kingdom
Geological Survey of Denmark and Greenland, Denmark
University of Aarhus, Denmark
Volume Title:Journal of Petrology
Source:Journal of Petrology, 48(1), p.141-157. Publisher: Oxford University Press, Oxford, United Kingdom. ISSN: 0022-3530
Publication Date:2007
Note:In English. 73 refs.; illus., incl. charts, 2 plates, geol. sketch maps
Summary:Textural maturity describes how far a rock has evolved towards textural equilibrium with minimization of interfacial energy. Solidification in a magma chamber forms impingement textures. Orthocumulates have initial ophitic or intersertal textures which evolve to solid state equilibrium by rounding of grain boundaries and increase in the median dihedral angle subtended at the junctions of two primocrystic grains with the initial phase, especially just below the solidus temperature in kilometre-scale mafic plutons. Quantifying textural maturity by measurement of dihedral angle populations in troctolitic and gabbroic cumulates from the Rum Eastern Layered Intrusion and the Skaergaard Intrusion shows the preservation of a record of thermal events related to magma chamber replenishment and the onset of chamber-wide convection. Significant new information about the crystallization of these two bodies is detailed. Liquidus phase assemblages influence the thermal history and the textural maturity, e.g. the presence of clinopyroxene as an additional (to olivine and plagioclase) liquidus phase hinders maturity. [B.E.L.]
Subsections:Igneous petrology
Subjects:Convection; Cooling; Cumulates; Intrusions; Layered intrusions; Liquid phase; Mafic composition; Magma chambers; Magmas; Maturity; Phase equilibria; Textures; Arctic region; Greenland; Skaergaard Intrusion; Rum Eastern layered intrusion
Coordinates:N680800 N681300 W0313500 W0314500
Abstract Numbers:07M/255
Record ID:2007044638
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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