Patterns of transformations in the compositions and properties of Icelandic hyaloclastites during lithogenesis

In Iceland, hyaloclastites form thick masses generated as a result of subglacial eruptions during Pliocene-Pleistocene surface glaciations. The formation of hyaloclastites and features of their alterations during lithogenesis were investigated. Hyaloclastites are extremely heterogeneous in their physical and physical-mechanical properties. A sequence of hyaloclastites secondary transformations was established from virgin, only slightly palagonitized hyaloclastites with contact-type cement to thoroughly transformed rocks with secondary minerals forming porous cement and partially substituting volcanic glass. A general tendency towards an increase in elasticity, density, strength, and thermal characteristics and towards a decrease in porosity and permeability has been observed with progression of secondary alterations, with the growth of age, from newer to more ancient deposits, and the depth of hyaloclastite burial.