Interconnected sills and inclined sheet intrusions control shallow magma transport in the Ferrar large igneous province, Antarctica

Abstract

Research Article| January 01, 2012 Interconnected sills and inclined sheet intrusions control shallow magma transport in the Ferrar large igneous province, Antarctica James D. Muirhead; James D. Muirhead † 1School of Environment, University of Auckland, Private Bag 92019, Auckland, New Zealand †E-mail: jmuirhead@ymail.com Search for other works by this author on: GSW Google Scholar Giulia Airoldi; Giulia Airoldi 2Geology Department, University of Otago, Leith Street, P.O. Box 56, Dunedin 9054, New Zealand Search for other works by this author on: GSW Google Scholar Julie V. Rowland; Julie V. Rowland 1School of Environment, University of Auckland, Private Bag 92019, Auckland, New Zealand Search for other works by this author on: GSW Google Scholar James D.L. White James D.L. White 2Geology Department, University of Otago, Leith Street, P.O. Box 56, Dunedin 9054, New Zealand Search for other works by this author on: GSW Google Scholar GSA Bulletin (2012) 124 (1-2): 162–180. https://doi.org/10.1130/B30455.1 Article history received: 20 Nov 2010 rev-recd: 25 Mar 2011 accepted: 06 Apr 2011 first online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation James D. Muirhead, Giulia Airoldi, Julie V. Rowland, James D.L. White; Interconnected sills and inclined sheet intrusions control shallow magma transport in the Ferrar large igneous province, Antarctica. GSA Bulletin 2012;; 124 (1-2): 162–180. doi: https://doi.org/10.1130/B30455.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Field observations and structural data from intrusive complexes at Allan Hills and Terra Cotta Mountain, South Victoria Land, Antarctica, demonstrate that interconnected sills and inclined sheets transported magma through the shallow subsurface. These sills and sheets represent the upper-crustal (top 4 km) plumbing system of the 183 Ma Ferrar large igneous province. The sheets are short in length (<1500 m), are moderately inclined (47° and 51° means), and show meter-scale variations in attitude; in places, they intruded bedding planes, resulting in stepped sheet-sill geometries. Sheet geometries and their relationship to the surrounding country rock are consistent with peripheral sheet intrusion under local magmatic stresses arising from roof-lift during sill injection. The sheet intrusions thus reflect the intrusive process itself rather than a far-field tectonic stress regime. The sills and sheets, together with local dolerite masses, formed the intrusive network that supplied magma to the Mawson Formation pyroclastic rocks in various parts of South Victoria Land and, by inference, the Kirkpatrick flood basalt lavas. The predominance of inclined sheets rather than steeply dipping dikes indicates a magmatic environment that is unlike the Jurassic rift arm inferred by previous authors. This could be explained using any of the following three scenarios. (1) The axis of the rift, and hence any rift-hosted dikes, lies beyond the current exposure area. (2) The regionally extensive Ferrar sills may have provided rheologically weak horizons that limited mechanical coupling of the basement rocks and overlying Beacon Supergroup, locally detaching the upper 4 km of the crust from possible synmagmatic basement extension below. (3) The Ferrar large igneous province was emplaced in a neutral tectonic setting. In this scenario, broad-scale distribution of magma through the province was controlled by preexisting structure in the basement, and local intrusion geometries reflect the physical interaction of intruding magma with bedding anisotropy of the Beacon Supergroup. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.