Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

Journal of the Geological Society

This Article Full Text (PDF) References Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by BÉDARD, J. H. Articles by HALLWORTH, M. A. Search for Related Content GeoRef GeoRef Citation

Peridotite sills and metasomatic gabbros in the Eastern Layered Series of the Rhum complex

Department of Earth Sciences, Downing Street, Cambridge University, Cambridge CB2 3EQ, UK

Mapping of the Eastern Layered Series (ELS) of the Rhum ultrabasic complex on the northern flank of Hallival shows that peridotite and allivalite (troctolite or gabbro) layers are laterally discontinuous and vary both in thickness and lithology. Peridotite generally has sharp upper and lower contacts against the allivalites, which sometimes cut across the layering in the allivalite. Reaction, dissolution and hybridization effects between peridotite and allivalite are developed locally. Some troctolite layers terminate as isolated, fingered blocks in peridotite. There are many small peridotite bodies which are clearly intrusive into allivalite and have previously been identified as distinct peridotite sheets and plugs. They are petrographically almost identical to the major stratiform peridotites and in some cases are apophyses from them. We propose that many of the peridotite layers in the ELS formed as thick sills of picritic magma emplaced into a partly solidified, layered troctolite complex. The stratiform gabbros of the ELS are heterogeneous, layered rocks that commonly contain relicts of troctolite and anorthosite. Wavy (metre-scale) contacts between gabbro and troctolite cut across pre-existing grain-size, modal and rhythmic layering with little disruption. These metasomatic gabbros mimic the textures, grain-size and rhythmic layering of their troctolitic protoliths. We propose that many of the ELS gabbros formed as a result of interaction between porous troctolites and a low-temperature basaltic melt. Residual basaltic melt segregated from solidifying peridotite may have caused this metasomatism.

This article has been cited by other articles:

				M. B. HOLNESS and B. WINPENNY The Unit 12 allivalite, Eastern Layered Intrusion, Isle of Rum: a textural and geochemical study of an open-system magma chamber Geological Magazine, May 1, 2009; 146(3): 437 - 450. [Abstract] [Full Text] [PDF]

				J. H. J. Bedard, B. D. Marsh, T. G. Hersum, H. R. Naslund, and S. B. Mukasa Large-scale Mechanical Redistribution of Orthopyroxene and Plagioclase in the Basement Sill, Ferrar Dolerites, McMurdo Dry Valleys, Antarctica: Petrological, Mineral-chemical and Field Evidence for Channelized Movement of Crystals and Melt J. Petrology, December 1, 2007; 48(12): 2289 - 2326. [Abstract] [Full Text] [PDF]

				M. B. Holness, M. A. Hallworth, A. Woods, and R. E. Sides Infiltration Metasomatism of Cumulates by Intrusive Magma Replenishment: the Wavy Horizon, Isle of Rum, Scotland J. Petrology, March 1, 2007; 48(3): 563 - 587. [Abstract] [Full Text] [PDF]

				Y.-G. Xu and B. He Thick, high-velocity crust in the Emeishan large igneous province, southwestern China: Evidence for crustal growth by magmatic underplating or intraplating Geological Society of America Special Papers, January 1, 2007; 430(0): 841 - 858. [Abstract] [Full Text] [PDF]

				M. B. Holness, T. F. D. Nielsen, and C. Tegner Textural Maturity of Cumulates: a Record of Chamber Filling, Liquidus Assemblage, Cooling Rate and Large-scale Convection in Mafic Layered Intrusions J. Petrology, January 1, 2007; 48(1): 141 - 157. [Abstract] [Full Text] [PDF]

				M. B. HOLNESS Spatial Constraints on Magma Chamber Replenishment Events from Textural Observations of Cumulates: the Rum Layered Intrusion, Scotland J. Petrology, August 1, 2005; 46(8): 1585 - 1601. [Abstract] [Full Text] [PDF]

				M. E. Brandriss and D. K. Bird Effects of H2O on Phase Relations during Crystallization of Gabbros in the Kap Edvard Holm Complex, East Greenland J. Petrology, June 1, 1999; 40(6): 1037 - 1064. [Abstract] [Full Text] [PDF]

				M. Wilson Magmatic differentiation Geological Society, London, Memoirs, January 1, 1995; 16(1): 205 - 218. [Abstract] [PDF]

				W. J. Wadsworth The peridotite plugs of northern Rum Scottish Journal of Geology, November 1, 1994; 30(2): 167 - 174. [Abstract] [PDF]

				M. WILSON Magmatic differentiation Journal of the Geological Society, August 1, 1993; 150(4): 611 - 624. [Abstract] [PDF]