Structures within greenschist facies Alpine Schist, central Southern Alps, New Zealand

Abstract

Ductile structures in the greenschist facies rocks of the Alpine Schist that lie in the headwaters of the Whataroa, Callery, and Balfour valleys formed during Mesozoic deformation, similar to those in the Otago Schist to the south. A general westward increase in metamorphic grade is locally disrupted and repeated by several late metamorphic faults. The first appearance of biotite occurs at tectonic boundaries in the Callery and Balfour sections. Metagreywackes are juxtaposed against a greenschistmetapelite-metachert sequence by a synmetamorphic ductile high strain zone in the lower Balfour valley. A prominent quartz rodding lineation in the high strain zone defines a stretching direction that plunges about 30° southwest. Structures in the high strain zone are locally cut by quartz (±biotite) veins, which have been weakly deformed. Fluid inclusions in quartz veins indicate that the veins formed about 8-10 km deep and that uplift was initially nearly isothermal. Pervasive foliation that formed during Mesozoic deformation was deformed into upright, open, kilometrescale folds, with some foliation-parallel boudinage, associated with the Miocene inception of the Alpine Fault. The resultant north to northeast trending folds plunge gently southwards. Deformation associated with Alpine Fault movement was only minor in the Alpine Schist greenschist facies and resulted in passive differential uplift of deeper parts of the schist pile in the west.

Penetration of deformation‐driven meteoric water into ductile rocks: Isotopic and model observations from the Southern Alps, New Zealand

“…These early structures are overprinted by a set of kilometre-scale open folds, generally known as the Alpine folds, with a NNE trend. They are associated with the onset of Cenozoic deformation (Lillie et al 1957;Findlay 1987;Cooper et al 1987;Craw et al 1994). The quartz veins analysed in this study (Fig.…”

“…Early synmetamorphic structures are associated with peak metamorphic conditions during the Mesozoic (Lillie et al 1957;Grindley 1963;Cooper 1974;Findlay 1985Findlay , 1987Craw et al 1994). These early structures are overprinted by a set of kilometre-scale open folds, generally known as the Alpine folds, with a NNE trend.…”

The approach to steady-state thermochronological distribution following orogenic development in the Southern Alps of New Zealand

“…This style of dynamically perturbed thermal structure is well documented for the Southern Alps. Both direct borehole measurements (Shi, Allis, and Davey, 1996) and indirect geological and geophysical evidence (Craw, 1988;Holm, Norris, and Craw, 1989;Craw, Rattenbury, and Johnstone, 1994;Ingham, 1995) indicate anomalously high near-surface temperatures and geothermal gradients throughout the orogen.…”

Nephrite and metagabbro in the Haast Schist at Muddy Creek, northwest Otago, New Zealand

“…8) showed thin horizons of both Aspiring Terrane rocks and the Pounamu Ultramafic basement to the Torlesse Terrane, tectonically emplaced into Torlessederived, metasedimentary sequences along imbricate thrusts, commonly parallel to the lower limbs of recumbent nappes. Support for a similar tectonic origin for some of the quantitatively minor metabasite horizons in the Torlesse Terrane has come from recent mapping in the central Southern Alps (Craw et al 1994). The Muddy Creek maficultramafic pod is interpreted to have a similar, tectonically emplaced origin, probably with an important component of diapirism.…”