Emplacement of sills into wet sediments at Grunehogna, western Dronning Maud Land, Antarctica

Abstract

The mid-Proterozoic Ritscherflya Supergroup, Antarctica, is intruded by numerous mafic to intermediate sills and small layered bodies. Contact relations are well exposed where the Grunehogna and Kullen sills intruded argillaceous and arenaceous sedimentary rocks of the Schumacherfjellet and Hogfonna Formations of the Ahlmannryggen Group. A 3 m thick peripheral zone above the upper contact of the Grunehogna sill consists of reconstituted sedimentary rocks which have been fluidized and recrystallized due to the intrusion. Local melting and crystallization of the sediments, under hydrous conditions and pressures below 312 bars, have produced zones of granite and granophyre, which grade into arenites where primary sedimentary structures are preserved. The sedimentary rocks have been deformed into large disharmonic folds where the sill transgresses the Schumacherfjellet Formation. The contact relations suggest that emplacement of the mafic sills and sheets at Grunehogna occurred when the sediments were still water-saturated and only partially lithified.

Carbonate melting and peperite formation at the intrusive contact between large mafic dykes and clastic sediments of the upper Palaeozoic Saint‐Jules Formation, New‐Carlisle, Quebec

“…The study supports the conclusions of Lentz (1999) that carbonatites may not be exclusively derived from mantle melts. Finally, contrary to most documented peperites, which are located along the sides of sills (Brooks et al 1982;Hanson and Schweickert 1982;Busby-Spera and White 1987;Branney and Suthren 1988;Krynauw et al 1988;Boulter 1993;Brooks 1995;Coira and Pérez 2002;Dadd and van Wagoner 2002;Squire and McPhie 2002), the sides of dykes (Leat and Thompson 1988;Kano 1989;Goto and McPhie 1996;Hooten and Ort 2002;McClintock and White 2002) or above laccoliths (Coira and Pérez 2002), the New-Carlisle occurrences are located at the termination of dykes and were seemingly more thoroughly invaded by hydrothermal fluids than previously reported peperite occurrences.…”

“…Mingling of glassy and non-glassy clasts is also commonly observed in other peperites, although the two types of clasts are thought to form at different stages of peperite formation (Hanson and Schweickert 1982;Skilling et al 2002). The New-Carlisle peperites also show evidence of melting, a far less common feature that has been documented in only a few examples (Schminke 1967;Ito et al 1984;Krynauw et al 1988;Yamamoto et al 1991;McPhie and Hunns 1995;WoldeGabriel et al 1999;Martin and White 2002). Because the Acadian unconformity dips westward and eastward from the New-Carlisle inlier (Figures 1 and 7), exposure of the basal peperite pinches out towards the inlier due to erosion, and eventually disappears below sea-level away from it.…”

Peperite: a review of magma–sediment mingling

“…Several authors record softsediment deformation of the host sediment along or close to the contact with peperite and/or the intrusion (Brooks et al, 1982;Hanson and Schweickert, 1982;Kokelaar, 1982;Lorenz, 1984;Du⁄eld et al, 1986;Walker and Francis, 1986;Krynauw et al, 1988;Kano, 1989;Brooks, 1995). Such deformation could be due to many processes, including sediment £uidisation, liquefaction, shear liqui¢cation and di¡erential compaction, forceful intrusion (Du⁄eld et al, 1986;Krynauw et al, 1988;Kano, 1989), explosions, and seismic or eruptive activity. Brooks (1995) attributed the origin of folds in host sediments adjacent to peperite to dispersal during peperite genesis of large juvenile lithic blocks near the contact, rather than to forceful intrusion of magma.…”

“…Peperite involving ma¢c intrusions or lava is described by Lacroix and Blondel (1927), Macdonald (1939), Smedes (1956), Wilshire and Hobbs (1962), Snyder and Fraser (1963), Schmincke (1967), Korsch (1984), Walker and Francis (1986), Busby-Spera and White (1987), White and Busby-Spera (1987), Krynauw et al (1988), Leat andThompson (1988), Sanders andJohnston (1989), Godchaux et al (1992), Rawlings (1993), Assorgia and Gimeno (1994), Brooks (1995), Goto and McPhie (1996), , Skilling (1998), Rawlings et al (1999), Doyle (2000), Mueller et al (2000), Corsaro and Mazzoleni (2002, this volume), Hooten and Ort (2002, this volume), Jerram and Stollhofen (2002, this volume), Lorenz and Bu « ttner (2002, this volume) and Squire and McPhie (2002, this volume). Papers providing extended discussion of the physical mechanisms of magma mingling with wet sediment include Kokelaar (1982), White (1996), Hanson and Hargrove (1999), Lorenz and Bu « ttner (2002, this volume), Wohletz (2002, this volume) and Zimanowski and Bu « ttner (2002, this volume).…”

Coastal Evolution, Hydrothermal Migration Pathways and Soft Deformation along the Campania Continental Shelf (Southern Tyrrhenian Sea): Insights from High-Resolution Seismic Profiles

“…The main trending direction of this front is similar to the one observed for the buried volcanic body [37,60], resulting in an E-W-trending flat-topped edifice. Magmatic bodies trigger thermal effects on the hosting sedimentary sequences and produce the expulsion of pore-water volumes [86][87][88]. This observation suggests that the observed fluid front is a hydrothermal-related feature.…”