168 Prospectus

Site: PP-4A

Priority: 1
Position: 47°45.41´N; 127°43.85´W
Water Depth: 2683 m
Sediment Thickness: 565 m
Total Penetration: 575 mbsf
Seismic Coverage: Line 95-26, SP 430 (Fig. 6B, Appendix 1B)

Objectives: At the Permeable Penetrators site relatively rugged relief of the igneous crust is buried by sediment everywhere, except at three small volcanic edifices where fluids vent through the seafloor. Holes spanning the primary basement relief will allow determination of the lateral thermal and chemical gradients in the upper igneous crust, and the buoyancy forces that drive fluid flow. The holes will also extend the overall drilling transect to 3.5 Ma. This CORK reentry hole is situated in a structurally similar location to Site PP-1A; along with those made at Site PP-5A, observations will allow the degree of thermal and chemical homogeneity of basement fluids and the pressure gradient driving fluid flow to be determined.

Drilling Program: RCB only, with approximately 40 m of basement penetration

Logging and Downhole: Approximately six temperature probe trips, packer/flowmeter testing, Quad-combo logging run, CORK installation

Nature of Rock Anticipated: Turbidite sediments, altered basalt

To Site PP-5A

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