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Teachers
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Expedition 309
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Journal
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Week 5
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"Rock on" |
6 August 2005
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Expedition 309 rock with vein mineral infilling and alteration halo (IODP close-up).
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Whole thin section scan of a 27 mm x 46 mm slide of massive aphyric fine-grained basalt with iron oxyhydroxide and saponite (a magnesium-rich clay mineral) infilling vein.
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Whole thin section scan of a 50 mm x 75 mm slide of aphyric fine-grained basalt with interstitial saponite (a magnesium-rich clay mineral).
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I spent the evening with the metamorphic petrologists (also known as alteration specialists) as they described thin sections (30 micron thick slices of rock glued to a glass slide). Metamorphic petrologists are interested in the alteration of rock, and on this cruise they are mainly looking for changes in mineralogy (via replacement of primary minerals with secondary minerals), vein mineralization and halo formation. It was interesting to learn about the processes of vein and halo formation. Veins are open fractures that are filled with secondary minerals precipitated from fluids that once flowed in the cracks. Halos are an area of discoloration caused by fluids infiltrating the rock adjacent to the crack.
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7 August 2005 |
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Bernardino Alemeida, Steward (Portugal), preparing lunch on the grill. *
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Yongjun Gao, Geochemist (US); Laura Galli, Metamorphic Petrologist (Italy); Akram Belghoul, Logging Trainee (France); Javier Espinosa, Schlumberger Engineer (US); Carole Cordier, Igneous Petrologist (France); and Tetsuya Sakuyama, Geochemist (Japan) enjoying the food and the company at a barbeque. ** |
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Provided the weather cooperates, this Sunday we’ll have a barbecue on deck for the midday meal. Due to inclement weather this will be only the second time we have been able to have a barbeque.
Even though meals cooked by our excellent catering staff, Catermar, far exceed my pre-cruise expectations, the barbeque is a welcome change from eating in the galley. The barbeque grill was made on the ship from a 20 inch piece of casing (or steel pipe). Casing is used to line a hole to prevent collapse, erosion or to isolate the hole from fluids or pressure. The grill is huge so lots of items can be cooked simultaneously. The fare usually consists of chicken, spareribs, hamburgers, fish and sausage done the way you like them. There are also a wide variety of salads, vegetables, other entrees and desserts.
We eat at the picnic tables on deck and there is a festive atmosphere. This break from the routine allows for more mingling of personnel, and the change of scenery helps to develop camaraderie between the different groups on the ship including Catermar, TransOcean, the Science Party and IODP Technicians. The Sunday barbeque is a treat looked forward to by all.
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8 August 2005 |
Today I joined the structural geology group working on core descriptions. Structural geologists study deformation in rocks, which includes fracturing, faulting and folding. They check the core for joints (cracks with no movement), veins, shear veins (caused by stresses in opposite directions), faults, breccia (angular fragments), and cataclastic zones (areas where stress induced structures are found). Although they look at many of the same features as the metamorphic petrologists, they focus on the causes of the features rather than changes in mineralogy. Details such as size, strike (direction) and dip (steepness) of veins and joints are measured. The descriptions from the structural group will eventually provide the science party with the overall picture of the stress field, and deformation of the oceanic crust, at this superfast spreading ridge.
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9 August 2005
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Approved samples for shorebased studies.
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The second round of sampling for shorebased studies (a sampling party) was held. Again I was amazed by how communicative and cooperative the scientists were when they were making their choices of samples. Stickers for approved requests were placed on marked pieces by the science party. The samples will be cut tomorrow by the technical staff.
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10 August 2005
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Florence Einaudi, Logging Staff Scientist (France); Akram Belghoul, Logging Trainee (France); and Javier Espinosa, Schlumberger Engineer (US) after a successful calibration of the Ultrasonic Borehole Instrument (UBI).
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I spent the day working in the Core Lab helping to bag and distribute the cut samples from the sampling party. The samples come in all shapes and sizes. Here are a few examples:
Thin section billet: 35 mm X 25 mm billet 0.5 to 0.75 cm thick from which a thin section is cut.
Slab: an area across the entire face of a core that is about 0.75 cm thick.
Quarter round: half of a working section of core.
Cube: a perfect 2 cm x 2 cm x 2 cm cube cut with a double bladed saw.
Minicore: 2.5 cm diameter core drilled from the center of a piece of rock with a water-cooled drill bit.
The Logging team of Florence Einaudi, Logging Staff Scientist (France); Akram Belghoul, Logging Trainee (France); and Javier Espinosa, Schlumberger Engineer (US) are beginning to assemble and calibrate the equipment they will use for the logging of Hole 1256D when we finish drilling. I was able to observe the set-up and calibration of the Ultrasonic Borehole Instrument (UBI). The UBI is a small rotating transducer that sends an acoustic signal into the hole as the device is being slowly raised. From the returned acoustic energy the UBI allows a 360° image of the hole to be assembled. Upon completion of the logging procedure at the end of this cruise, this image will be combined and compared with other data.
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11 August 2005
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It’s only the end of week five, but Susumu Umino, Co-Chief Scientist (Japan); Damon Teagle, Co-Chief Scienitst (UK); and Neil Banerjee, IODP/TAMU Staff Scientist (US) have given the science party a set of objectives that need to be met by the end of the cruise. It’s not too early to begin the important task of completing the Expedition 309 reports.
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12 August 2005 |
As the drill string was being lowered for a bit change and re-entry, the pump pressure readings were below normal. In an effort to determine the cause of the low pump pressures, the subsea camera was deployed, and drilling mud was pumped down the drill string. Sure enough, a jet of mud was observed shooting out of a crack in the drill pipe. The pipe was brought back to the surface, the cracked pipe was switched out, and soon the bit was headed once again toward the ocean floor. The ever-observant TransOcean team was on the ball again, heading off another potential disaster.
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| Next Installment: "Rock bottom " |
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* Photo by Shannon Housley, Imaging Specialist, IODP/TAMU (USA)
** Photo by Christopher Smith-Duque, Metamorphic Petrologist (UK). |
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