Colville I '13 (TAN1313) cruise report

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de Ronde, C.E.J.; Caratori Tontini, F.; Timm, C.; Merle, S.G. 2017 Colville I '13 (TAN1313) cruise report. Lower Hutt, N.Z.: GNS Science. GNS Science report 2016/72 27 p.; doi: 10.21420/G2H014

Abstract: This research cruise (Figure 1) was the first of its kind in successfully assembling a geophysical data set from the southern portion of the Colville Ridge. This survey is the first in a series planned to map the entire Colville Ridge, which is part of a larger ongoing project to map and collect data from the Kermadec arc and backarc within New Zealand’s Exclusive Economic Zone (EEZ). The aim of this survey is delivering individual base maps of bathymetry, backscatter, gravity and magnetic data, which provide baseline information for scientific study and 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 feature, which extends over 1000 km within NZ’s EEZ. It is thought to be ~5 Myr old and possibly composed of various volcanic centres, consistent with results from the 2012 NIRVANA geophysics cruise that crossed the mid-part of the Ridge (Wysoczanski et al 2012). EM 302 standard multibeam data was practically non-existent for the Colville Ridge prior to this cruise, with only single ships tracks crossing the feature in a few areas (Figure 2). There had been no prior systematic mapping of this Ridge even though its southern end is situated only ~200 km offshore from Auckland. Our comprehensive survey of the southern portion of the Colville Ridge was completed over 15 days that included 12 days on station, with 11 days used for swath mapping and 1 day for dredging. This cruise produced the first complete maps of detailed bathymetry, backscatter, magnetics and gravity over a large part of the southern Colville Ridge. In total, 17,500 km2 of bathymetry and backscatter data were acquired, along with 3,200 line-km of magnetic and gravity data. Rocks were also collected from 13 separate dredge stations, resulting in 36 different samples of varying lithologies. The results from this cruise will be used for scientific purposes and mineral exploration; the data collected are essential for carrying out more focused future surveys by AUV, ROV and manned submersibles targeting prospective sites. It is our plan that future surveys will be undertaken to systematically map the mid- and northern-portions of the Colville Ridge, thus providing a complete data set of this significant feature. The results from this survey will be published as maps and papers in international journals and will be publically available. (auth)