Overblog
Suivre ce blog
Editer la page Administration Créer mon blog

Earth of fire

Actualité volcanique, Article de fond sur étude de volcan, tectonique, récits et photos de voyage

Between North island / New Zealand and the Fiji archipelago, various structures are parallel : the Colville and Kermadec ridges, separated by  Havre Trough, and the Kermadec Trench .

F1.large
Tectonic of the Pacific and Australian plates around New Zealand, now and in the past: 10 and 2 Ma
NVA : Northern Volcanic Arc ; TVZ :Taupo Vocanic Zone , CVZ: Coromandel Volvanic Area; CR: Corville ridge ; KR: Kermadec Ridge .


Colville ridge - GVP
General bathymetric image of Corville and Kermadec ridges, made ​​during the exploration of the Kermadec Ridge by NOAA in 2005 - doc . GVP

subduction sous dorsales Colville et Kermadec - seafriends
Subduction of the Pacific plate beneath the Australian plate and dive up to 600 km. deep - In sub-surface, from right to left : the Kermadec Trench , Raoul Island in the Kermadec arc, the Havre Trough, the Colville ridge and the South Fiji Basin - doc . GNS Science

Regional tectonics is related to the subduction of the Pacific plate beneath the Australian plate and the formation of marginal basins .

A thorough bathymetry of the Kermadec ridge was performed in the past, by cons the Colville parallel ridge has been little studied. Yet it is an important structure , with peaks dominate the floor on either side of 2,000 meters.

This has just been done by teams of GNS Science, in collaboration with NIWA - National Institute of Water and Atmospheric Research - and Oregon State University.

NZ - Colville ridge - NZ Herald
Localisation of the Colville ridge and first 3D picture - doc . GNS Science / in The New Zealand Herald

It validated the hypothesis that the Colville and Kermadec ridges were originally united before a rift, the Havre Trough, separates them there are a few million years ago .

Morphological differences were observed between the two ridges and interpreted as a reflection of collapse phenomena , lifting and significant erosion on the Kermadec Ridge, contrasting with lower uplift and erosion on the Colville ridge.

New data shows more than the Colville ridge is not exclusively volcanic , rocks found forming a mix of sedimentary and volcanic rocks .


Cornel-de-Ronde
Dr in marine geology Cornel de Ronde commenting on the new bathymetric map of the Colville ridge - photo GNS .

We found numerous faults crossing the area , most oriented NE-SW , and  deepening to the E . These issues suggest a presence of minerals on the ocean floor, reassembled along faults from hot fluids containing various metal compounds in solution . The search for these metals will be carried out by
Germans and Japanese research institutes, in collaboration with researchers of New Zealand , and through autonomous underwater vehicles in 2014-15.

 

 

Sources :

- The New Zealad Herald - Sea floor map result stuns experts - link

- GNS Science - Origin of seabed more complex than scientists first imagined - link

- Morphology and Evolution of the Remnant Colville and Active Kermadec Arc Ridges South of 33°30′ S  - by Ian C.Wright - link 

- Subductions et ouvertures océaniques dans le Sud-Ouest Pacifique - Oceanic subductions and active spreading in the Southwest Pacific - by

Etienne Ruellan and Yves Lagabrielle

Articles récents

Hébergé par Overblog