3 weeks 4 days
Strategy: The Name of the Game
Submitted by Nicole Kurtz on Wed, 01/30/2013 - 16:43
The gloves are coming off for these sample requests, and unfortunately it’s been terribly fun for me to watch. Because of the collaboration condition, people are strategizing and carefully selecting the perfect piece of core. The problem is that’s only half the battle. Odds are another group could be gunning for the same section. So what do you do then? Compromise? Give it up and move on? Or fight and persuade everyone else you deserve that section?
People are forming groups that aren’t necessarily specific to the groups they are working with while on board. In fact, it’s almost beneficial to have one person from each lab group so that each specialty is represented. The groups I am referring to are: Structural Geology, Metamorphic Petrology, Igneous Petrology, Paleomagnetism, Physical Properties, and Inorganic Chemistry. It’s taken me roughly 7 weeks to figure out the difference between the groups, so here’s the briefest descriptions I can muster:
The Structural Geology people are usually the first to see the core when it comes on deck which makes sense because their main job is to measure the observational structures of the rocks. They put together the overall sequence of what everyone sees. This group documents the history of the evolution of the rocks - from the lava state in the magma chamber to when it ends up as faults on the seafloor. The Structure group tries to determine the features that move the rocks around after they’ve been made. In short: They are big picture people.
The Metamorphic group is on board this expedition to find out about the water/rock interaction in this area. They observe the cores to figure out what the original mineral was that came to be altered. Sometimes it is visible to naked eyes, but sometimes it’s difficult and that’s when the microscope and thin sections come into play. Water/Rock interaction is a very local phenomenon, which is why thin sections are so important. Some minerals repress other minerals, and each mineral is stable at a certain temperature condition, so if we can understand the sequence of how the minerals were altered, we can understand the change of the rocks. This group tries to figure out what happened to get from A to B to C...but sometimes all they can see from the rocks is a lot of C, and trace parts of B. Not an easy task.
Igneous Petrologists…or IgPets from my understand work pretty closely with the Metamorphic group. They look at the quantity of certain minerals are present in a piece of core. This group is looking for the variations and the irregularities of these minerals as well. Sometimes the minerals have been stretched or elongated and this information helps them figure out the lithology variation. So, that means how much volume of a certain mineral is where. IgPets also use use thin sections to see the detail, but sometimes the thin section is a lot different than what they initially described. If that happens, they have to go back and recheck.
IgPets differ from the Metamorphic group because they look at the primary minerals: the A part of the A,B, C equation. Sometimes all of the primary minerals are gone, or they’ve been altered. The Metamorphic group looks at the alterations.
The Physical Properties group has the coolest sounding job (but don’t tell the others I said that): essentially they spend all day in the labs shooting things at the rocks to see how it reacts. They want to see how the rock responds to a stimulus.
They send P-waves through the rock at the speed of sound. Phys Props measure the amount of time it takes for the wave to pass through. They do the same thing with heat by sticking a needle in the rock, and measuring how the rock responds to the heat, and how long it takes to cool again.
This group also hits the sample with gamma rays to get the Gamma Ray Attenuation. All that means is that they shoot gamma rays at the one side and one would expect the same amount to come out the other side, but it doesn’t because the gamma ray is composed of particles that are not able to pass through depending on the material of the rock. So, this tells us about the density of the rock.
The data tells them the real physical properties of the rock (…hence the name), like the amount of pores it has or how compact the rock is. The amount of pores can tell the scientists about fluid flow…which is a main objective of this expedition. The scientists have standards that let them know exactly how the core should react, and then they compare the results from the tests.
Paleomagnetism is another cool sounding group: They’re responsible for finding out how magnetic the rocks are that we have recovered. The rocks became magnetized when they solidified from a magma and cooled down below about 600°C, and as they did so they trapped a record of the Earth’s magnetic field direction inside the rock that we can measure and interpret.
The direction of the magnetization acts like a compass inside the rocks that allows this group to work out how much they have been rotated during their history, as we know the direction in which the magnetization originally pointed. During the alteration that these rocks have suffered they have also picked up other magnetizations that are added to (or replace) their original one, and so we can also say something about the timing and temperature of these alteration events from our experiments.
Inorganic Chemistry gives the first real quantitative information on the composition. The other scientists in the labs describe the surface of the core. They say things like ‘this white stuff is probably this, and the other stuff over here could be that.’ But this group looks at the chemical makeup to find out exactly what elements are in the ‘white stuff’ and that ‘other stuff.’
This group attempts to understand the different elements that are in these cores. They can examine the minerals that build up the rocks and look for the concentration of isotopes. They do this by digesting the core. That doesn’t mean they eat it. Digest means that they bring it into a solution. They use machines like the Inductively Coupled Plasma Atomic Emission Spectrometer (that’s a mouth full). The problem is that the machines are built for liquid samples, but these rocks are solid. So, they make a solution out of the rock by first pounding it up into a powder, and then they cool the solution really fast to turn it into glass. Then they decompose the glass in acid, so that the machine can define the different elements that are in the core.
All of these individual groups analyze the samples we recover from the seafloor to find out the evolution of the ocean crust. An interesting aspect of this cruise, and one of the objectives, has been determining the cooling rates of the magma. That means how slow or fast the magma crystalized into the rocks we pull up. The cooling rates are affected by temperature and fluid flow. But there is a lot of debate over how the cool temperatures are able to reach the lower depths of the crust.
In just a few weeks this expedition will end and the JOIDES Resolution will return to port, but that doesn’t mean the research will end. The scientists on board will continue analyzing the rocks to complete their research. But that is why the sample requests are so important right now. Each group of scientists needs to pick their samples carefully because they won’t have access to everything on shore like they do on the boat right now. There is such overlap though between the lab groups, and with the minimal amount of core recovered this leg…it’s easy to understand why everyone has their game faces on to make sure they get the pieces they want. And that’s why strategy is the name of the game.