The evolution of the marine Si cycle in the Archean-Palaeozoic - an overlooked Si source?

Abstract

Marine siliceous deposits of cherts are known to have formed since the Archean and reflect the biogeochemical Si cycle, comprising the burial of Si in sediments during diagenesis. The actualistic assumption of biological control over the Si cycle was outlined in the seminal models of Si evolution in Earth history sketched by Maliva et al. (1989), Maliva and Siever, 1989a, Maliva and Siever, 1989b and Siever, 1991, Siever, 1992. Their assumptions were treated as the dominant paradigm in subsequent geological studies and outlined the approach to be taken towards the relationship between the productivity of silicifiers and the formation of siliceous rocks. In light of new paleontological studies of evolution of silicifers, as well as chert facies distribution analysis in combination with geochemical (REE + Y, Y/Ho, Eu/Eu⁎, Al-Fe-Mn, Hg) and isotopic (δ30Si) studies of siliceous rocks, the biological control of siliceous sponges and radiolarians over the Palaeozoic Si cycle is a phenomenon which is difficult to understand. This review provides a critical discussion of the seminal model of Si evolution presented over a quarter of a century ago and, based on new studies, considers the endogenous source of dSi (volcanic and hydrothermal activity, weathering of freshly erupted basalts) as an overlooked controlling factor of Si cycling in the Archean-Palaeozoic.