Abstract
The Eyre Creek Mélange, a north–northwest trending 0.5–1 km-wide zone within Caples Terrane rocks in northern Southland, New Zealand, is composed of phyllonite and mylonitic rocks, and includes lenses of spilite, chert and altered microgabbro. This shear-zone mélange (SZM) is enclosed within undifferentiated textural zone IIA Caples Terrane sandstones (Q10F14L76) that are metamorphosed to pumpellyite–actinolite grade. The sandstones correlate with Caples Terrane Bold Peak Formation, and display features consistent with deposition as proximal through distal turbidity current deposits, including pelitic and olistostromal material. Altered microgabbros within the SZM contain relict clinopyroxenes that provide an alkali basalt signature, and display within-plate affinities. Banded red and white chert lenses include recrystallized radiolarian tests, and provided a conodont remnant, resembling Carboniferous Idiognathodontinae Taphrognathus varians. The SZM probably developed in multiple stages during subduction accretion within the Eastern Province. The finer-grained sediments were disrupted within a shear-zone, and fragments of seamount-derived intrusive and volcanic rock were incorporated into the SZM, together with banded cherts derived from the subducting slab. The SZM probably extends south along strike to a similar zone of disruption in Caples Terrane rocks at Mid Dome. Clinopyroxene geochemistry and location of the SZM indicate that both it and the mélange at Mid Dome are lateral correlatives of the Greenstone Mélange; these mélanges mark the position of an anastomosing, throughgoing shear-zone within the Caples portion of the evolving Jurassic–Cretaceous accretionary wedge. The SZM provides an example of the product of accretionary prism processes that record both sedimentation and deformation during subduction accretion.
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call