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doi:10.2204/iodp.sp.311.2005

SAMPLING STRATEGY

General

Shipboard and shore-based researchers should refer to the interim IODP Sample, Data, and Obligations policy posted on the Web at iodp.org/data_samples.html. This document outlines the policy for distributing IODP samples and data to research scientists, curators, and educators. The document also defines the obligations that sample and data recipients incur. Access to data and core sampling during Expedition 311, or within the 1 y moratorium, must be approved by the Sample Allocation Committee (SAC). The SAC (composed of Co-Chief Scientists, Staff Scientist, and IODP Curator on shore and curatorial representative on board ship) will work with the Shipboard Scientific Party to formulate a formal expedition-specific sampling plan for shipboard and post cruise sampling.

Shipboard scientists are expected to submit sample requests 3 months before the beginning of the expedition. Sample requests may be submitted at iodp.tamu.edu/curation/samples.html. Based on sample requests (shore based and shipboard), the SAC and Shipboard Scientific Party will prepare a working cruise sampling plan. This plan will be subject to modification depending upon the actual material recovered and collaborations that may evolve between scientists during the expedition. Modifications to the sampling plan during the expedition require the approval of the SAC.

All sample frequencies and sizes must be justified on a scientific basis and will depend on core recovery, the full spectrum of other requests, and the cruise objectives. Some redundancy of measurement is unavoidable, but minimizing the duplication of measurements among the shipboard party and identified shore-based collaborators will be a factor in evaluating sample requests.

Cruise-Specific Sampling Plan

Because the main focus of this expedition is gas hydrates, special protocols regarding sampling and measurement strategies will be required in addition to routine analyses and procedures. Modifications to core and sample handling, based on experience gained from previous ODP and other hydrate drilling programs, will be required to quickly identify intervals containing gas hydrates. Summarized below is the anticipated measurement and sampling scheme and special hydrate sampling plan and protocol:

  • Infrared (IR) imaging will be conducted via continuous scan systems and by handheld cameras for immediate hydrate identification on the catwalk.
  • Organic geochemistry samples will be collected by routine headspace and void gas sampling.
  • Inorganic geochemistry samples will be collected for interstitial water geochemistry.
  • Physical properties will include thermal conductivity, multisensor track (MST; P-wave velocity, non-contact resistivity, gamma ray attenuation bulk density, and magnetic susceptibility), moisture and density, split core velocity, shear strength, and resistivity.
  • Sedimentology will include core description, smear slides, color reflectance, and digital core imaging.
  • Biostratigraphy.
  • Paleomagnetic analyses will support sediment age determination and gas hydrate-related mineralization.
  • Microbiology sampling will be integrated with the organic and inorganic chemistry sampling program; existing microbiological sampling protocols will be employed including analyses of sample contamination.
  • Downhole logging data including conventional wireline and LWD will be acquired.
  • Downhole tool-derived data (APCT, DVTPP, and APCM) will be recorded.
  • Additional sampling requests specified by shipboard and shore-based participants will be accommodated when possible.

    Special Hydrate Sampling

    It is expected that gas hydrate–bearing core material will be recovered during conventional APC/XCB coring operations. It is also planned that PCS/HYACINTH coring will be employed to analyze the in situ occurrence of gas hydrate and to recover gas hydrate samples under in situ conditions. Special procedures for sampling gas hydrate–bearing cores follow:

  • Sampling on the catwalk or from pressure cores will be based on an integrated sample plan, which will be developed from individual shipboard and shore-based sample requests.
  • Gas hydrate sampling will be monitored by digital video and voice recording for immediate sample description.
  • Specialized dissociation tests will be conducted on gas hydrate samples for volumetric and geochemical analyses.
  • Recovered gas hydrate samples will be stored in liquid N2 and/or in a repressurized sample vessel. PCS cores will be processed shipboard. HYACINTH recovered pressure cores will be maintained at pressurized conditions for shipboard and shore-based analyses.
  • Special laboratory equipment designed to transfer and measure gas hydrate properties under controlled pressure conditions will be used. Specific laboratory equipment being considered includes the Geotek vertical logger, Georgia Tech MST-P, and Lawrence-Berkley X-ray computing tomography (CT) scanner (depending on funding availability).
  • Because of the proximity and appropriate facilities, the Pacific Geoscience Centre (located in Sidney, British Columbia, Canada) is proposed as a clearinghouse for gas hydrate samples collected under the integrated sample plan.
  • Gas hydrate samples will be distributed to approved investigators after inventory according to approved sampling requests.

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