Leg 175 severely tested our staff, facilities, and equipment. Many "manual" core-processing tasks could be automated to relieve some of the workload. Handling hazardous core materials was a problem that we dealt with during the leg. Most of the sites had either high H2S levels (200+ ppm) or produced noxious organic gases.
A seismic survey was used to locate our first site, but the remaining sites were located using GPS coordinates only. Both the multichannel and single-channel streamers were used during the seismic survey, but because of technical difficulties, we were unable to process the multichannel data. These data will be returned to shore for further processing.
High-resolution IW sampling was performed on four out of 13 sites. It consisted of one IW per section for the first 60 m, then one per core until 100 m, and one every three cores thereafter. Around 350 analyses were done, leading to a heavy usage of the Dionex, AA, Cl titrator, and spectrophotometer.
Solid core samples were analyzed for inorganic and total carbon (using the coulometer and the carbon/nitrogen/sulfur analyzer [CNS]). Based on their organic carbon content, some samples were selected and analyzed by the Rock-Eval. The system was used to determine S1, S2, and S3. Gas chromatograph #3 and the natural gas analyzer were used to provide real-time monitoring of the volatile hydrocarbons and H2S.
High recovery and the resulting volume of data overwhelmed the capacity of the shipboard server's disk space, causing numerous problems throughout the leg. Problems with Macintosh systems surfaced almost daily, some requiring reinstallation of the operating system. The mail system was also very unreliable during this leg. Hardware problems on the VAX and software problems on the NetWare servers caused repeated losses of service. The Laroux virus was a frequent nuisance but never caused any serious problems.
With more than 8000 m of core passing through the lab during the leg, it was fortunate that everything ran smoothly and there were no complications that required any serious modifications to either procedures or instruments. H2S levels were monitored with sensors on the catwalk and with hand-held units on the splitting room. Cores were degassed on the catwalk and again in the splitting room until safe H2S levels were obtained.
Routine shipboard and investigator samples were taken from the first hole at all sites. Sampling frequency was quite high but was revised as the cruise continued to accumulate the tremendous amount of core recovered and to ease the workload at the sampling table.
Downhole Measurements Lab
In situ temperature measurements were made at all sites. The APC/Adara cutting shoe was used for these measurements with a 94% success rate.
No problems reported.
This leg saw heavy use of the cryogenic magnetometer. All of the cores were measured plus several hundred discrete samples. Fortunately, the magnetometer and the LabView software ran with few problems. All APC cores were oriented using the tensor tool.
No problems to report.
Physical Properties Lab
The MST and color reflectometry measurements were critical to the leg. Fortunately, there was only one minor problem with the P-wave logger that was solved by using the back up unit. The single-channel thermal conductivity unit was used throughout the leg and was more than able to keep up with the core flow.
Underway Geophysics Lab and Fantail
The starboard magnetometer was reheaded and is now working properly. The hydraulic motor for the starboard hose-bundle handler was repaired with a seal supplied by Sedco and with assistance from their mechanic.
With the captain's permission, the void space over the sonar dome was opened. Careful testing confirmed that our 12kHz transducer was bad, as well as the bulkhead connector installed in the cover plate. A new transducer and connector were ordered. During some upcoming port call, the sonar dome will have to be pulled to affect repairs.
In addition to the "standard" X-ray diffraction (XRD) bulk analyses, the sedimentologists requested clay separations for analysis by XRD and analysis of standard mixtures for quantitative XRD calculations. They also expressed an interest in X-ray fluorescence (XRF) analyses of sediments. None of these requests could be accommodated because of the anticipated high core recovery. Initially, it was agreed that one bulk XRD sample per core would be analyzed, but even this sampling rate proved to be impossible to maintain. After 411 bulk XRD samples, the X-ray lab was closed. No routine XRD samples were taken after Site 1082.
The lab equipment operated satisfactorily during the leg. Compared with previous legs, no major problems that were out of the ordinary occurred with the majority of the equipment. As always, the first two weeks were spent addressing minor problems that were discovered during start-up operations. A great deal of time was spent removing the TOTCO (drilling-rig instrument company) hardware from the derrick.
Software Developments and Upgrades
The MST software was upgraded to LabVIEW 4.1, and the natural gamma-ray data collection routine was modified to truncate the "garbage channels" from the spectrum data. The data server connect routine was modified to look for the DATA1 server.
VS software was upgraded to LabVIEW 4.1, and the data server connect routine was modified to look for the DATA1 server.
The Long Core software for the cryogenic magnetometer was upgraded to include a routine that displays the collected data in four plot formats: (1) intensity vs. decay, (2) vector demagnetization, (3) As-Zijiderveld, and (4) equal area.
The stand-alone weighing programs for the chemistry and X-ray labs' weighing stations were replaced with a new Windows 95 LabVIEW application. The application uses a new weighing algorithm and provides a high-frequency filter option. A version for the Mac OS will be provided in the future.
New versions of the MAD, T-TOOL, and COULOMETER software were installed during this leg.
A new version of Depth-O-Matic was developed to replace the slow JANUS depth utility. Unlike the JANUS depth utility, Depth-O-Matic will work with tabs, commas, or space delimited file formats. Also, it will work with data files that have multiple title lines. Depth-O Matic can work with single files or load and concatenate multiple files in nested directories. The depth-matching algorithm is more efficient than the routine used by the JANUS depth utility; for example, the JANUS depth utility will take 45 min to process a file of 24,000 data points, whereas Depth-O-Matic only takes 3 min.
New Thermal Conductivity software (V3.20) for the TK04 Thermal Conductivity Meter was brought to the ship and installed. The new software allows for the contact resistance of the probes and for the loss of heat into the probe half space. The quality of results is improved (can differ on the order of 1%), and an empirical correction of the thermal conductivity values obtained with half-space measurements is no longer necessary, even on samples with low thermal conductivity. The user interface and the appearance of the measuring and evaluation program remain the same. The changes are mainly internal.
To 175 Table of Contents