Colville II '15 (TAN1512) cruise report

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de Ronde, C.E.J.; Caratori Tontini, F.; Timm, C.; Merle, S.G. 2017 Colville II '15 (TAN1512) cruise report. Lower Hutt, N.Z.: GNS Science. GNS Science report 2016/73 20 p.; doi: 10.21420/G2C889


Abstract: This research cruise was successful in swath mapping the mid-part of the Colville Ridge and collecting underway-geophysical measurements as part of an ongoing project to survey the Colville Ridge within New Zealand’s Exclusive Economic Zone (EEZ). The main outcome of this expedition is providing fundamental base maps for future mineral exploration. The Colville Ridge is a prominent tectonic feature that marks the western boundary of the Kermadec Arc-Havre Trough backarc system. Very little is known about this large feature on the seafloor, which extends over 1000 km within NZ’s EEZ. It is thought to be at least 2 Myr old (and likely much older) and is possibly composed of various volcanic centres. EM 300 standard multi-beam data was largely missing for the Colville Ridge, with only single ship’s tracks crossing the ridge in a few areas. In 2013 a comprehensive survey of the southern portion of the Colville Ridge was completed during the 15 day OS2020 Colville ’13 cruise that included 12 days on station, with 11 days used for swath mapping and 1 day for dredging. This cruise was highly successful, having produced the first complete map of detailed bathymetry, backscatter, magnetics and gravity over a large part of the southern Colville Ridge. Rocks were also collected from 13 separate stations. The 21 day Colville II ’15 cruise was successful in acquiring gravity and magnetic measurements, along with bathymetry and backscatter data, during 17 days on station, over an area of ~21,320 km2. The datasets have 100% coverage of these parameters, enabling us to ‘stack’ the gravity and magnetic maps on top of the bathymetry and backscatter, enabling a multi-disciplinary approach to interpretation. Rock samples were collected from 20 dredge sites that covered the length of the ridge mapped during the survey, and which included a variety of bathymetric features. Together, the information collected are crucial in our ability to identify prospective sites to carry out more focused, follow-up surveys by AUVs, ROVs, and possibly manned submersibles along the Colville Ridge. The results from this survey will be published as maps and papers in international journals and will be publicly accessible online at GNS. (auth)