After the bathymetrists introduced their work in the latest blog entry, we, the petrologists now like to do the same and give a brief introduction to our work on board.<\/em><\/p>\n The working cycle of the petrologists begins when a good dredge position is found. The search for a good position is based on the bathymetrists work. Good dredge positions are steep slopes with a tilt of more than 25\u00b0, as less sediment accumulates there and dredging upslope as well as potential rock edges increase the chance to recover samples. In addition, areas with strong backscatter signals are preferred, as they are a sign for hard rock and less sediment, which could indicate the basalts we are looking after during this cruise.<\/em><\/p>\n In communication with the bridge we determine the most suited dredge direction (against wind and swell is best) and after they brought the ship in position, the dredge is released into the water. We use a \u00a0so called chain-bag dredge, which is comparable to a fishnet made of steel installed beneath a metal box without top and teethlike edges on the rims. With this tool rock samples can be collected from the seafloor.<\/em><\/p>\n In coordination with the winch driver and the deckscrew we lower the dredge to the seafloor, pull it over the seafloor and afterwards bring it back on deck. When the dredge has bottom contact the ship navigates to the endpoint of the dredging procedure while laying out more cable.<\/em><\/p>\n When pulling the dredge over the seafloor, the rope tension needs to be watched carefully when the dredge \u201ebites\u201c into the rocks. If it gets stuck, a solution has to be found in arrangement with the bridge, e.g. the dredge will be pulled loose backward or sideward.<\/em><\/p>\n If the dreding went without issues (which is the common case), the device is back on deck after a total of three to four hours. This is the most exciting part for all \u2013 what rock samples did the dredge bring up?<\/em><\/p>\n Afterwards, all samples have to be cleaned, labelled and photographed. A closer look on the inside of the rocks leads to the decision whether and which geochemical analysis should be done with the pieces and the rocks are subsequently prepared for those by sawing blocks. Finally, the samples are packed and stored for the journey back to Kiel.<\/em><\/p>\n Depending on the number of samples such a working cycle may last up to ten hours. So, the different teams are communicating a lot about what kind of work needs to be done in their shifts and when the next dredge is scheduled.<\/em><\/p>\n Sometimes in this organized process there are some unexpected surprises, for example a dredge full of manganese nodules two days ago.<\/em><\/p>\n With best regards from board,<\/em> Unsere Petrologen mit einem unerwarteten “Fang”. Auch wenn Manganknollen nicht unbedingt auf ihrer Wunschliste stehen ist dieser Fund aus der Guinea Transformstr\u00f6rung durchaus interessant. Nachdem sich in dem letzten Blogeintrag die Bathymetriker vorgestellt haben, m\u00f6chten nun auch wir Petrologen einen detaillierteren Eindruck unserer Arbeit geben. Der Arbeitszyklus der Petrologen beginnt, sobald in Zusammenarbeit mit der Bathymetrie ein geeigneter Bereich zum Probennehmen gefunden wurde. Geeignet bedeutet in diesem Fall Hangsteigungen von mehr als 25%, da sich an solchen H\u00e4ngen meist […]<\/p>\n","protected":false},"author":188,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[9],"tags":[],"class_list":["post-59","post","type-post","status-publish","format-standard","hentry","category-deep-sea"],"_links":{"self":[{"href":"https:\/\/www.oceanblogs.org\/msm70\/wp-json\/wp\/v2\/posts\/59","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.oceanblogs.org\/msm70\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.oceanblogs.org\/msm70\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.oceanblogs.org\/msm70\/wp-json\/wp\/v2\/users\/188"}],"replies":[{"embeddable":true,"href":"https:\/\/www.oceanblogs.org\/msm70\/wp-json\/wp\/v2\/comments?post=59"}],"version-history":[{"count":3,"href":"https:\/\/www.oceanblogs.org\/msm70\/wp-json\/wp\/v2\/posts\/59\/revisions"}],"predecessor-version":[{"id":66,"href":"https:\/\/www.oceanblogs.org\/msm70\/wp-json\/wp\/v2\/posts\/59\/revisions\/66"}],"wp:attachment":[{"href":"https:\/\/www.oceanblogs.org\/msm70\/wp-json\/wp\/v2\/media?parent=59"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.oceanblogs.org\/msm70\/wp-json\/wp\/v2\/categories?post=59"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.oceanblogs.org\/msm70\/wp-json\/wp\/v2\/tags?post=59"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
\nLouisa Krach & J\u00f6rg Follmann<\/em>
\nCAU<\/em><\/p>\n![\"\"](\"http:\/\/www.oceanblogs.org\/msm70\/wp-content\/uploads\/sites\/55\/2018\/01\/Petro_01-OK.jpg\")
\nDie Kettensackdredge geht zu Wasser.
\nA chain-bag dredge station is starting.<\/em><\/p>\n![\"\"](\"http:\/\/www.oceanblogs.org\/msm70\/wp-content\/uploads\/sites\/55\/2018\/01\/Petro_02-OK.jpg\")
<\/p>\n
\nOur petrologists with an unexpected “catch”. Eventhough manganese nodules are not the objective of this expedition, this finding from the Guinea fracture zone is still interesting.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"