Jurassic magmatism in Dronning Maud Land: synthesis of results of the MAMOG project

Abstract

Abstract:The distribution and geochemical relationships of the Early Jurassic Ferrar large igneous province (LIP) are examined and it is concluded that they support the lateral flow model for the emplacement of the province, with a source along the strongly magmatic Early Jurassic Antarctica-Africa rifted margin. Published data and new analyses from the Pensacola Range are used to show that the dominant magma type in the Ferrar, the Mount Fazio chemical type (MFCT) occurs in the Theron Mountains, Shackleton Range, Whichaway Nunataks, Pensacola Mountains (all Antarctica), and South Africa, as well as well-known outcrops in Victoria Land, Antarctica, southeast Australia and New Zealand. Chemical compositions are shown to be somewhat varied, but similar enough for them to be considered as representing closely related magmas. Examination of geochemical trends with distance from the interpreted magma source indicates that Mg# and MgO abundances decline with distance travelled, and it is argued that this is consistent with the lateral flow model. The Scarab Peak chemical type (SPCT) occurs as sills in the Theron Mountains and Whichaway Nunataks, and as lavas in Victoria Land, is geochemically very homogeneous. Despite this, Mg#, MgO, Ti/Y and Ti/Zr all fall with distance from the interpreted source, consistent with fractional crystallisation occurring during the lateral flow of the magmas. Flow took place in dykes or (more likely) sills. No feeder dyke swarm has been identified. The distances flowed, at least 4 100 km for MFCT and 3 700 km for SPCT are the longest interpreted lateral magma flows on Earth.End of abstract

Origin, Distribution and Evolution of Plume Magmatism in East Antarctica

“…Nevertheless, it should be noted that the Karoo-Maud plume probably was different in some respects from what is considered to be a typical mantle plume (Courtillot et al, 2003): the volume of magmatic material supplied to the surface is minor, no higher than 60 000 km 3 , even if the partly overlain volcanics of the Karoo basin with accompanying dikes, sills, and small intrusions are accounted for; the plume-lithosphere interaction occurred in several stages over a long time interval, in contrast to the short-term (1-4 Ma) magmatism that usually accompanies the penetration of mantle plumes into the lithosphere (White & McKenzie, 1989). The investigation of the character of flood basalt magmatism in Antarctica, which was performed within the MAMOG Project (Leat et al, 2007), confirmed that it lasted for at least 20-30 Ma, when a series of dikes and flows were formed around the plume center over an area of about 145 000 km 2 along the Antarctic coast (DML). The eastward spreading of the Karoo-Maud plume can be indirectly supported by the existence of a large basic intrusion, which extends along the DML coast and is marked by a high-amplitude (×100 nT) magnetic anomaly (Golynsky et al, 2002(Golynsky et al, , 2006.…”

“…The spatial distribution of the dikes indicates the eastward spreading of the plume material from DML to the Schirmacher Oasis within at least 10 Ma (up to ~35 Ma, taking into account the uncertainty of age determination). On the other hand, the considerable duration and multistage character of plume magmatism related to the activity of the Karoo-Maud plume in Antarctica and Africa (Leat et al, 2007;Luttinen et al, 2002) may indicate that the Mesozoic dikes of the oasis correspond to a single stage of plume magmatism. In such a case, the rate of eastward plume propagation can be considered only as a rough estimate, and the time of 10 Ma, as the upper limit.…”

“…Transantarctic Mountains and Indian Ocean coast (Elliot et al, 1999;Leat et al, 2007;White & McKenzie, 1989). The westernmost occurrences of this magmatism are basalts and dolerites from the western part of the Dronning Maud Land (DML), which have tholeiitic compositions and are geochemically enriched to a varying degree (Harris et al, 1990;Luttinen & Furnes, 2000;Vuori & Luttinen 2003).…”

The geochemistry of Middle Jurassic dykes associated with the Straumsvola–Tvora alkaline plutons, Dronning Maud Land, Antarctica and their association with the Karoo large igneous province

“…The linear magnetic low along the axis of the rift is interpreted to image sediments within the rift structure (Ferraccioli et al, 2005b). No lavas at similar or higher structural levels as the Jurassic intrusive complexes are imaged by the aeromagnetic data and the rift is therefore interpreted to be magmatically 'dry', with Jurassic magmatism restricted to the alkaline complexes and limited dyke swarms (Ferraccioli et al, 2005b;Leat et al, 2007;Curtis et al, 2008).…”

“…This paper is one of a series which describes the results of the British Antarctic Survey 'Magmatism as a monitor of Gondwana breakup' project that investigates the volcanic history of the Dronning Maud Land area and its relationship to the Karoo LIP (Riley et al, 2005;Ferraccioli et al, 2005a,b;Leat et al, 2007;Curtis et al, 2008).…”