| Identifier | 2018-602-FA | ||||||||
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| Alternate names | Cruise RGR 1 | ||||||||
| Also known as | Rio Grande Rise (RGR 1), 2018 | ||||||||
| Purpose | Collect baseline information and samples of ferromanganese crusts and phosphorites from Rio Grande Rise to determine processes mineralization | ||||||||
| Location | Rio Grande Rise, SW Atlantic | ||||||||
| Summary | Jim Hein and his PhD student and USGS intern, Kira Mizell, PCMSC, participated in a research cruise from 28 January to 21 February to the Rio Grande Rise in the SW Atlantic Ocean aboard the University of São Paulo (Brazil) ship R/V Alpha Crucis (formally University of Hawaii’s ship, Moana Wave). The goals of the cruise were to better understand this enigmatic plateau and to collect samples to determine the genesis of the mineral deposits and processes of mineralization that have occurred on this flat-topped plateau. We had some ideas about the origin of the mineral deposits, ferromanganese (FeMn) crusts and phosphorite, based on huge slabs Jim saw in a warehouse some years ago collected by CPRM (Geological Survey of Brazil). Unfortunately, the Alpha Crucis did not have the capacity to collect such large samples, but using a variety of 1-meter wide dredges, we were able to collect abundant phosphorite and FeMn crust samples, mostly from the upper parts of the plateau, 600-900 m water depths. Another goal of the cruise was to train Kira, as well as the University of São Paulo researchers and ship’s crew, on dredging logistics and techniques, which they had not done previously, and to provide guidance on the techniques of study and current understanding of the geneses of these types of deep-ocean mineral deposits. Of the 22 days aboard ship, 15 days were packed full with various operations, rock and sediment sampling, multibeam and back-scatter mapping, water-column hydrography and sampling, and laboratory activities, during which Kira and Jim assisted in the completion of 17 dredges that recovered several hundred kilograms of rocks, of which more than 250 rock sample were cut on a diamond saw and described in detail. The rock samples proved very interesting with an amazing variety of phosphorites, FeMn crusts, volcanic rocks, limestones, and others, as well as some very curious rocks, such as granitic gneiss, which should not occur on this plateau; we guess that these rounded pebbles were ice rafted from perhaps Patagonia during the last ice age. The FeMn crusts are particularly unique in that they appear to be heavily phosphatized throughout, and their surfaces are smoothed and polished, indicating that they are not presently growing and that current activity has been vigorous in this region, which eroded the non-phosphatized parts of FeMn crusts found on the flat top of the plateau. In addition, very few of the volcanic rocks were broken from outcrop, which indicates that they were talus debris; follow-up studies using a ROV, cameras, and larger, heavier dredges will be important. This cruise was indispensable as a teaching tool for how to interpret the in situ context of rocks that are recovered by dredge alone and how to proceed with additional studies. | ||||||||
| Info derived | sample analysis of marine minerals to understand processes of mineralization | ||||||||
| Comments | While in Brazil, post-cruise briefings and lectures were given by Hein at the University of Sao Paulo. | ||||||||
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| Vehicles | None |
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| Organization |
2885 Mission Street
Santa Cruz, CA95060
(831) 460-7401
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| Principal investigators | James R HeinKira Mizell | ||||
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| Affiliate principal | Luigi Jovane, University of Sao Paulo, Brazil |
| Data category: | Biological Field Study, Electro-Magnetic, Environmental Data, Geochemical, Location-Elevation, Sampling, Seismics, Sonar, Time Series |
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| Data type: | Surveys (biological), Magnetics, Chlorophyll, Conductivity, CTD, Current, Density, Depth, Dissolved Oxygen, Fluorescence, Nutrients, pH, Sediment Properties, Temperature, Surveys (geochemical), Navigation, Biology, Chemistry, Geology, Sub Bottom Profiler, Multibeam, Sidescan, Sound Velocity, Mooring (physical oceanography) |
| Equipment | Usage description | Data types | Datasets |
|---|---|---|---|
| water bottle | Surveys (biological), Biology, Chemistry | (no data reported) | |
| magnetometer | Magnetics | (no data reported) | |
| Magnetometer | Magnetics | (no data reported) | |
| CTD | Surveys (geochemical), Experiments (geochemical), CTD | (no data reported) | |
| watersamples | Conductivity, CTD, Dissolved Oxygen, Fluorescence, Nitrate, pH, Temperature, Turbidity, Wave | (no data reported) | |
| temperature | Temperature | (no data reported) | |
| Other | Unknown, Meteorology, CTD, Temperature, pH, CO2, Radon, Conductivity, Current, Dissolved Oxygen, Turbidity, Fluorescence, Wave, ORP, Tide, Methane, Depth, Light, Nitrate, Gas Hydrates, Density, Sediment Properties, Osmometic Pressure, Chlorophyll, Nutrients, Pressure | (no data reported) | |
| salinity sensor | Conductivity | (no data reported) | |
| acousticdoppler | Current | (no data reported) | |
| current meter | Current | (no data reported) | |
| oxygenprofiler | Dissolved Oxygen | (no data reported) | |
| flourometer | Fluorescence | (no data reported) | |
| pressuregauge | Depth | (no data reported) | |
| Sensors - pressure | Depth | (no data reported) | |
| hydrometer | Density | (no data reported) | |
| Nutrient sampler | Chlorophyll, Nutrients | (no data reported) | |
| Other | Unknown, Surveys (geochemical), Experiments (geochemical) | (no data reported) | |
| GPS | Navigation | (no data reported) | |
| boxcore | Biology, Geology | (no data reported) | |
| corer | Geology | (no data reported) | |
| dredge | Geology | 1 | |
| Gravity Core | Geology | (no data reported) | |
| samples | Biology, Chemistry, Geology | (no data reported) | |
| 512 chirp-source | Sub Bottom Profiler | (no data reported) | |
| subbottomprofiler | Sub Bottom Profiler | (no data reported) | |
| multibeam | Multibeam | (no data reported) | |
| acousticbackscatter | Sidescan | (no data reported) | |
| computer | Sidescan | (no data reported) | |
| ADVF | Sound Velocity | (no data reported) | |
| instrumentmooring | Mooring (physical oceanography) | (no data reported) |
| Dataset name | Equipment | Description | Dataset contact |
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| Mineralogy, rare earth elements, and strontium isotopic composition of phosphorites and phosphatized rocks | dredge | The location (latitude, longitude, depth), mineralogy, concentrations of phosphorus and rare earth elements, and 87Sr/86Sr ratios of phosphorites and phosphatized FeMn crusts, ironstones, and carbonates from 10 dredge sites are presented here. | Kira Mizell |