Manual Information

Contents 

Introduction

Method Overview

Core specimens for moisture and density (MAD) analysis are extruded from a section half for:

• Mass: measured using a motion-compensating dual analytical balance system and a drying oven.
• Volume: measured using a caliper or by a helium displacement pycnometer that employs Archimedes’ principle of fluid displacement to determine the volume of solid objects.

The MAD properties of interest are:

• Water content
• Bulk density
• Dry density
  • Porosity
  • Void ratio

  These properties are calculated based on three out of four measured values:

  • Wet mass
  • Dry mass
  • Wet volume
  • Dry volume

  Method Theory

  Phase relationships of mineral density, porosity, void ratio, and water content are basic sediment and rock properties that are found most accurately through mass and volume determinations. The mass or volume of the bulk (wet) material, the dried material, and the extracted water (assumed to be interstitial pore fluid) is corrected for the mass and volume of salt evaporated during the drying process. The mass and volume of the evaporated pore water salts are calculated for standard seawater salinity, seawater density at laboratory conditions, and an average seawater salt density.

  Soils can be either 2-phase or 3-phase compositions (i.e., completely dry or partially saturated). For MAD measurements the analyst determines whether the sample contains a 2- or 3-phase system:

  • Completely dry soil contains 2 phases: solid soil particles and pore air.
  • Fully saturated soil also contains 2 phases: solid soil particles and pore water.
  • Partially saturated soil contains 3 phases: solid soil particles, pore water, and pore air.

  MAD data provide a direct estimate of porosity and void ratio and the average density of constituent minerals. Porosity variations are controlled by consolidation and lithification, composition, alteration, and deformation of the sediments or rocks. MAD data can be used to calibrate high-resolution gamma ray attenuation (GRA) bulk density data, which are sampled at a much higher resolution than is possible with the MAD method. If mineral density can be defined with sufficient precision, GRA bulk density can be expressed as porosity.

  Selecting the Appropriate Analysis Sub-method

  The user needs to decide which sub-method (A, B, C, or D) should be used for the MAD analysis. The choice depends primarily on the type of sample material to be measured. In addition, Sub-methods A and B are not recommended from an analytical quality point of view. Therefore, the choice is generally limited to Sub-methods C and D based on the following criteria:

  • Fine-grained, saturated sediments or fine-grained igneous material: Sub-method C
  • Porous rocks (e.g., vesicular basalt and limestone) that cannot be confidently saturated: Sub-method D

Definition of LIMS Analyses

Analyses in the context of the Laboratory Information Management System (LIMS) are defined based on the data acquisition systems that provide sets of data. The MADMax software application captures the data from all three types of analysis. For the MAD group of analyses, these are as follows.

Caliper analyses (CALIPER)

Volume is calculated after measuring the sample’s geometric dimensions using micrometer calipers.

Pycnometer analysis (PYC)

Sample volume is measured using a helium pycnometer.

MAD mass analysis (MAD_MASS)

Wet or dry mass is measured using the motion-compensating dual balance system.

• “Wet” refers to the saturated (undrained) state of a sediment or rock sample
• “Dry” refers to the state after drying 24 hr at 105°C and holding in the desiccator 2–3 hr.

MAD analysis (MAD)

This set of calculations is applied as appropriate for each sub-method.

Apparatus, Reagents, & Materials

• Dual balance system
• Hexapycnometer system
• Caliper
• Sample drying equipment
• Sampling tools and sampling containers

Hardware

Dual balance system

Two Mettler-Toledo XS204 analytical balances compensate for ship’s motion while weighing samples (see the Shipboard Analytical Balance User Guide for a detailed description of the mass determination system). In Figure 1 note that the left balance is the REFERENCE balance and the right balance is the UNKNOWN balance.