Figure 6. Measured pore-water (open hexagons) compositions and hydrate meltwater compositions for samples from depths shallower than 3.5 mbsf (filled squares) and greater than 32 mbsf (open squares). Curves labeled 1, 2, and 3 are FRI-curves determined with lower boundary conditions, with [Cl^-] and ²H of 1400 and -5.6, 1220 and -5.6, and 1220 and -6.0, respectively. The principle for determination of hydrate amount (see "Appendix B" in Chap. 22, this volume) is demonstrated by vector V, which shows how the composition of a pore-water sample with an initial composition on FRI-curve 2 will change when mixed with hydrate meltwater. The slope of vector V can be calculated from the initial composition of the pore water ("Appendix B" in Chap. 22, this volume). Hydrate amount is determined by decomposition of the vector V that intersects a particular pore-water or hydrate meltwater composition into vectors V₁ and V₂. Vector V_a was used to determine the composition of the shallow hydrate samples. The composition of the deepest hydrate sample was determined by the means of vector V_b.