Overblog Suivre ce blog
Editer la page Administration Créer mon blog

Earth of fire

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


South island - Banks peninsula

  NZ South Island - central portion of the island with the Banks Peninsula on the east coast - Nasa

Akaroa Volcanic Group :

It includes all volcanic eruptions products of central, flanks, and parasites vents localized in two-thirds southeast of Banks Peninsula .
A fieldwork shows that the lavas and pyroclastic which form the Akaroa volcano can be divided into two phases, described as preliminary and main .

akaroa-harbour-nature - tripadvisor
                                               Akaroa Harbour - photo Tripadvisor

Phase I / preliminary - 11 ? to 9 Ma
Rocks produced during this preliminary phase are visible on the inner coastline of Akaroa harbor. Oldest - Preliminary Phase 1 - are basaltic lava flows. The preliminary phase 2 comes in trachytic tuffs, breccias , agglomerates, flows, sills and a large dome which marks the end of the construction of the proto- Akaroa. The preliminary phase 3 includes basaltic flows, tuffs, lahar deposits, cinder cones and pyroclastic breccias

Phase II / Main - 9 - 8 Ma
A prolonged period of weathering and erosion separates the two phases . The main cone of Akaroa is built on a base of predominantly lava flows hawaiite type 
and pyroclastics, and rarer mugéarite, benmoréite and trachyte lava flows. Volcanic activity can be classified as Hawaiian to moderately Strombolian .

Elephant Rock, Akaroa Harbour, Banks Peninsula - Christchur           
Banks Peninsula , Akaroa Harbour - "Elephant Rock " - photo Christchurhnz

Onawe Peninsula, 2007 - J Oswald
                               Akaroa Volcano - the Onawe peninsula - photo J.Oswald

Akaroa harbour - Te Ara - McLinv1010The eruptive activity of Akaroa is marked by the intrusion of dykes, predominance trachytic, and building of five large domes of trachyte . Dykes radiate from a central area, S / SE of the peninsula Onawe (a plug, localized in Akaroa ), which coincides with the presumed site of the main eruption pipe.

Map of Akaroa harbor and location of the peninsula Onawe - doc . Te Ara NZ

Gravimetric analysis reveals an intrusive complex in subsurface equivalent to more than 615 km³ of intrusive materials.

                             Dyke in Akaroa Harbour - photo Tripadvisor

The Lyttelton Volcanic Complex , located north - west of Banks Peninsula , includes five overlapping cones. Centers of activity of the volcano Lyttelton arrange around Quail Island, which is considered close to the original vent .

                                      Lyttelton Harbour  - photo pan5v3

Lyttleton harbour - Stuff NZ
                                   Lyttelton Harbour - photo Stuff NZ

We assume that two different magmatic systems fueled the intraplate basaltic volcanism on Banks Peninsula , with simultaneous activity in the N0 and SE thereof, to form the two volcanic complexes Lyttelton and Akaroa .

New Zealand - Banks Peninsular, Arkada c1865
Old engraving of the Akaroa bay / Banks Peninsula  - 1865 c - prints of Ancient Australia & Pacific . / New Zealand - Banks Peninsular, Arkada



Sources :

- University of Canterbury / Geological sciences - The geology and geochemistry of Akaroa volcano, Banks peninsula , NZ - by C.J.Dorsey - link

- The basal beds of the Akaroa volcano - by R.Speight - link

- University of Canterbury / Geological sciences - Growth, Structure and Evolution the Lyttelton Volcanic Complex, Banks Peninsula, New Zealand - by S.J Hampton -  link

Articles récents

Hébergé par Overblog