Leg 173 Technical Report


The 453 m of recovered core consisted of sediment, breccia, and hard rock. Physical properties, magnetic properties, mineral and elemental properties, and structural properities were investigated on the core material. The technical staff carefully curated the material for the shipboard scientific participants as well as future investigators. The scientists and curator strategically planned the sampling of all core material to maximize the scientific return of core analysis. Two new ODP technicians sailed this leg, two temporary technicians, and the underway technician filled in as acting lab officer.

Chemistry Lab
A relatively small number of samples, three per hole, were taken for interstitial water analysis. Most of the holes were drilled to just above the acoustic basement before coring began. At this point the sediments were too lithified to contain a substantial quantity of interstitial water. The chemistry technicians analyzed the samples for salinity, chlorinity, sulphate, magnesium, calcium, potassium, sodium, lithium, and strontium. The chemistry technicians analyzed each core for its gas content using the headspace technique. An average of thirty-five samples per hole were analyzed for total carbon and inorganic carbon. The chemistry technicians extensively serviced the natural gas analyzer and performed routine maintenance on the other lab equipment.

The chemists assisted SEDCO to determine the magnitude of diesel fuel contamination in the potable water supply. The lab did not have the proper equipment to test potable water and the tests were inconclusive.

Computer Services
In addition to the regular two marine computer specialists (MCS), an ODP programmer sailed this leg to assist with the JANUS acceptance. The JANUS program ran smoothly for the majority of applications. The paleontologists required the most assistance because of the complexity of the application and documentation. The X-ray application did not work, apparently because of a lack of proper documentation. Other bugs were reported to ODP where a comprehensive bug checklist is being compiled. This was Chris Stephens' (MCS) first leg with ODP.

The network fiber connection between the underway lab and machine room was activated to bypass the troublesome bridge in the downhole measurements lab.

The MCSs provided routine computer support for the scientific, technical, and operations staff. Maintenance requirements were common but not abnormal for the harsh environment of the North Atlantic. The MCSs put five new Power Mac 7600/132 computers into service, replacing older machines.

Core Lab
The core material processed this leg was both lithified sediment and hard rock. The technicians split all the core sections with the supersaw. The hard-rock label program developed on Leg 172 made labeling these rocks less tedious. To complete the upgrade, we need to print the labels on label stock and avoid the very tedious job of cutting out the labels with scissors. The core lab technicians made use of the sometimes long waits between cores by performing maintenance on the core saws, drill presses, and cut-off saws.

AppleCore v0.7.5b was used for barrel sheets. Because the hard rock lithologies were so variable and complex, the standard ODP descriptions used for fine-grained or coarse-grained rocks did not apply. The petrologists used a slightly modified format for their descriptions.

A scientist brought a DMT color core scanner to use on this leg. The portable unit provided comprehensive digital core images of both split-half core and whole-round core. Core flow was altered to accommodate this nonroutine procedure. The whole-round pieces were removed from the liner before labeling; this is potentially dangerous because core pieces could be misplaced. The scientists scanned nearly all the core recovered this leg.

Curation on a low-recovery leg is usually problematic and this leg was no exception. The scientists had too little material to share and several of the sample requests overlapped. The co-chiefs, staff scientists, and curator spent many hours resolving the conflicts over sample requests. Early in the leg the scientific party decided to defer taking personal samples until the end of the leg. This approach made scientific sense. Practically speaking, waiting until the end delayed resolving sample conflicts and put a greater workload on the technical staff during the time when the emphasis was to prepare the labs for the next group of scientists. The new sample policy went into effect this leg. We still attempted to operate under the old policy in most cases unless justification was provided. We attempted to maintain one half the working section and limit hard rock samples to 100 per investigator. The Leg 149 archive sections were shipped from the east coast repository for use on this leg.

Downhole Measurements Lab
The lab was used exclusively by the logging scientists. There were no measurements taken using the ODP downhole measurement tools.

Electronics Services
The electronics technicians assisted in all laboratories with equipment repair and maintenance. They also repaired and then collected data from sensors in the derrick. This data will be used to model drill string movement and stresses for the diamond coring system. Larry St. John, electronics tech, sailed for the first time this leg.

Microscope/Paleontology Lab
The scientists used the microscopes for paleontology and petrology. Usage was normal except for a large number of photomicrographs.

Paleomagnetics Lab
This lab saw heavy use of the thermal demagnitizer unit as well as many passes through the cryo AF demagnitizer. The paleomagnetics technician performed tests on the cryo helium level gauge. He also configured the Windows NT computer to make file transfer of paleomagnetics data easier.

Photography Services
Normal photography services were required this leg. All core sections were photographed using color and black and white film and processed on board. A more than average number of closeup photographs were requested by the scientific staff. The photographer assisted the scientists with the setup and use of microscopes.

Physical Properties Lab
The physical properties scientists and technician measured magnetic susceptibility and natural gamma radiation using the multisensor track. They determined thermal conductivity by the half space method on split sections. Discrete velocity and index properties were taken at selected core intervals. An electronics technician built a pulse generator for the P-wave velocimeter.

Thin Section Lab
The scientists requested 195 thin sections from such diverse materials as sand, silt, clay, chalk, limestone, granite, gabbro, and periodite. The requests came from sedimentologists, petrologists, and paleontologists.

Underway Geophysics Lab
We received the first of four replacement thermal graphic line scanning recorders purchased for the underway lab. The EPC recorder was used with the 3.5 kHz depth profiling system. The underway technician wrote a LabVIEW program to control the recording parameters and interface to a GPS receiver for annotation. The 3.5 kHz record is annotated every five minutes with GPS time, latitude, longitude, course, and speed. The EPC signal quality was much improved compared to the old Raytheon line scan recorders. The electronics techs and underway tech tested the multichannel streamer system to diagnose the problems encountered on the previous leg. All the lab equipment tested satisfactorily. One of the ITI six channel streamers had a faulty channel and was returned for repair at the end of the leg. The other ITI streamer tested satifactorily during deck tests. A quick water test at the end of the leg indicated that this streamer was not being towed at a proper depth. Further tests are needed to establish the correct towing depth.

X-ray Lab
The scientists requested 213 bulk powder samples for X-ray diffraction analysis. The rocks recovered this leg were highly altered; therefore, the X-ray technician received a small number of samples for major and trace element identification on the X-ray flourescence unit.

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