Chemical and isotopic evidence for the nature of the fluid in CH4-containing sediments of the Håkon Mosby Mud Volcano

Abstract

 The pore waters of CH₄-containing sediments of the Håkon Mosby Mud Volcano were rich in NH⁺ ₄, Br^-, and I^-; exhibited a high total alkalinity; but were poor in Cl^-and SO^2- ₄. The geological evidence and our data suggest that organic matter decomposition in preglacial or early interglacial sediments took place during early diagenesis (bacterial processes) and during metamorphism (thermogenic processes under the 3100-m-thick layer of glacial sediments), accompanied by mud volcano fluid generation. It is argued that the CH₄of the mud volcano sediments has a mixed, biogenic and thermogenic, origin.