TDI-Brooks International, Inc.

Introduction To Surface Geochemical Exploration

Piston Coring for Surface Geochemical Exploration

In Surface Geochemical Exploration (SGE) studies, maximum core penetration, uncontaminated samples, and accurate core positioning are of highest importance. TDI-Brooks cores are obtained with a 1,000 kilogram piston corer, and every effort is made to achieve maximum penetration on each sample. Differential Global Positioning System (DGPS) navigation equipment accurate to +/- 5m is used to locate and record sample positions.

use buttons to control demo

A piston corer uses a "free fall" of the coring rig to achieve a greater initial force on impact than gravity coring, and a sliding piston inside the core barrel to reduce inside wall friction with the sediment and to assist in the evacuation of displaced water from the top of the corer.

The piston-coring rig is comprised of a trigger assembly, the coring weight assembly, core barrels, tip assembly, and piston. The core barrels are in lengths of 6 and 9 meters. Expendable (used only once) butyrate tubes line the core-barrel and contain the sample.

Oil Stained Core in Butyrate Liner

As soon as the core is retrieved on-deck, the core liner is divided and labeled into 20-cm sections. The core sections are then capped and taken to a "clean" laboratory for processing. Each core section is extruded and the top and bottom 1-cm of sediment is discarded. Generally, three core sections from near the bottom of the core are sampled for the various analytical requirements, and a fourth section is saved as an archive. The exact core sections sampled is dependent on the core recovery (see figure below). All samples are stored at -15 degrees to -20 degrees C. Detailed records are kept for each core, describing subsampling procedures and noting any unusual features in the sample (visible oil, hydrogen sulfide odor, etc). Water depth, date, time, and WGS 84 latitude and longitude are also recorded for each sample.

Sampling based on core length

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