Study of two carbonate seepages from Lower to Upper Miocene Hikurangi active margin (New Zealand, North Island) - Normandie Université Accéder directement au contenu
Communication Dans Un Congrès Année : 2023

Study of two carbonate seepages from Lower to Upper Miocene Hikurangi active margin (New Zealand, North Island)

Résumé

The study focuses on the analysis of tubular carbonate concretions outcropping in two areas in the New Zealand Hikurangi active margin: the Akitio syncline and Cape Turnagain. This work intends to enlighten the role of pipes involved in fluids circulation and to compare them from two former basins having evolved from lower/ middle Miocene (Akitio) and upper Miocene (Cape Turnagain). In both cases, the host rock is composed of very fine-grained muddy sediments (calcareous mudstones) containing a lot of framboidal pyrites, quartz, feldspar and very few and poorly diversified fauna indicating paleoenvironmental stressed depositional settings. Con- cerning the tubes themselves, they differ drastically on a morphological point of view: They are cylindrical and very large in Cape Turnagain, whereas they are rugose and far smaller in Akitio. In the Akitio syncline, the biggest tubes are characterized by a lot of late cross-cutting fracturation and brecciation stages, filled by softly deformed monomict fluidized muds. More-over, association of framboidal pyrite, authigenic quartz and bitumen lining was observed in pre-fracturation/pre-injection sequence. In the case of Cape Turnagain, diagenesis sequence is highlighted by complex dissolution/cementation stages (early calcite/dolomite cemen- tation, framboidal pyrite, aragonitic crust). Neither late fluidized infills were observed nor late fracturing. 80 stable isotope (δ18O/δ13C) analysis were carried on micro-samples. All these data are completed by cathodolu- minescence analysis associated to major and minor chemical analysis (SEM/EDS elemental measurements) In Akitio basin, two main origins of carbonate cements and mud infilling were revealed: anaerobic oxidation of microbial CH4 and temperature increasing in the later stages. The building of tube framework took place in early reducing environment followed by later infilling of the tubes, using the pre-existing “plumbing system”. In Cape Turnagain, early dissociation of gas hydrates below the sea floor and reduction of CO2 as a by-product of methanogenesis are involved (Nyman, 2009). Finally, tube formation differs strongly between these two areas: they were both differently early built and they moreover experienced hotter late fluid circulation in Akitio than those of Cape Turnagain.
Fichier non déposé

Dates et versions

hal-04165284 , version 1 (16-04-2024)

Identifiants

  • HAL Id : hal-04165284 , version 1

Citer

Renaud Toullec, Julien Bailleul, Vincent Caron, Geoffroy Mahieux, Franck Chanier, et al.. Study of two carbonate seepages from Lower to Upper Miocene Hikurangi active margin (New Zealand, North Island). 36th International Meeting of Sedimentology, Jun 2023, Dubrovnik, Croatia. ⟨hal-04165284⟩
0 Consultations
4 Téléchargements

Partager

Gmail Facebook X LinkedIn More