Compressional and extensional tectonics in low-medium pressure granulites from the Larsemann Hills, east Antarctica

• Published in: Geological Magazine
• Main Authors: Carson, C., Dirks, P., Hand, M., Sims, J., Wilson, C.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press 1995
• Subjects: East Antarctica; Larsemann Hills; Antarc*; Antarctica
• Online Access: http://hdl.handle.net/2440/13710; https://doi.org/10.1017/S0016756800011729

<jats:title>Abstract</jats:title><jats:p>Meta-sediments in the Larsemann Hills that preserve a coherent stratigraphy, form a cover sequence deposited upon basement of mafic–felsic granulite. Their outcrop pattern defines a 10 kilometre wide east–west trending synclinal trough structure in which basement–cover contacts differ in the north and the south, suggesting tectonic interleaving during a prograde, D<jats:sub>1</jats:sub> thickening event. Subsequent conditions reached low-medium pressure granulite grade, and structures can be divided into two groups, D<jats:sub>2</jats:sub> and D<jats:sub>3</jats:sub>, each defined by a unique lineation direction and shear sense. D<jats:sub>2</jats:sub> structures which are associated with the dominant gneissic foliation in much of the Larsemann Hills, contain a moderately east-plunging lineation indicative of west-directed thrusting. D<jats:sub>2</jats:sub> comprises a colinear fold sequence that evolved from early intrafolial folds to late upright folds. D<jats:sub>3</jats:sub> structures are associated with a high-strain zone, to the south of the Larsemann Hills, where S<jats:sub>3</jats:sub> is the dominant gneissic layering and folds sequences resemble D<jats:sub>2</jats:sub> folding. Outside the D<jats:sub>3</jats:sub> high-strain zone occurs a low-strain D<jats:sub>3</jats:sub> window, preserving low-strain D<jats:sub>3</jats:sub> structures (minor shear bands and upright folds) that partly re-orient D<jats:sub>2</jats:sub> structures. All structures are truncated by a series of planar pegmatites and parallel D<jats:sub>4</jats:sub> mylonite zones, recording extensional dextral displacements.</jats:p><jats:p>D<jats:sub>2</jats:sub> assemblages include coexisting garnet–orthopyroxene pairs recording peak conditions of ∼ 7 kbar and ∼ 780°C. Subsequent retrograde ...