The ratio of 18O to 16O in cherts and other chemical sediments has increased by about 15‰ over geological time, but the cause of this increase is debated. Here, we provide a 1D sediment-column model designed to investigate the role of diagenesis, and specifically the heat flow through marine sediments, in setting the chert oxygen isotope ratios. The model simulates the transformation of amorphous silica (opal-A) to crystalline quartz via an intermediate phase by using a silicon mass balance that is driven by the kinetics and thermodynamics of silica phase dissolution and (re)precipitation. The model demonstrates that heat flow through marine sediments influences the rate, and therefore depths, temperatures, and oxygen isotope compositions, at which cherts form. The implication is that because global heat flow from the solid Earth has decreased through geological time, heat flow is an important contributing factor to the long-term trend in chert oxygen isotope composition.
The model is provided as a set of Matlab scripts (".m" files) and assorted input datasets provided as standard plain text files. The model is described in full in the manuscript "Chert oxygen isotope ratios are driven by Earth's thermal evolution" by Michael Tatzel, Patrick J. Frings, Marcus Oelze, Daniel Herwartz, Nils K. Lünsdorf, and Michael Wiedenbeck, and in the online Supporting Information associated with the manuscript. Once downloaded and unzipped, the files should be added to the local Matlab search path. The parameters of interest can be changed in the first few lines of 'chertKineticModel.m'. No other files need to be opened or modified. These files have been tested in Matlab R2020a running on Mac OS X 12.2.1 and in Matlab R2022b on Mac OS X 12.6.1.
The Kupferschiefer districts in Central Europe contain some of the world’s highest-grade sediment-hosted stratiform Cu (SSC) deposits (see Borg et al., 2012). The high-grade sulfide mineralization in the organic matter-rich marine mudstones of the Kupferschiefer (T1), and also in the underlying continental sandstones of the uppermost Rotliegend (S1) and overlying Zechstein Limestone (Ca1), in the Saale subbasin (Eastern Germany) are dominantly formed as a replacement of calcite cement (Mohammedyasin et al., 2023).
We provide carbonate major element chemistry, carbon isotope composition of organic matter, and calcite carbon and oxygen isotope microanalysis datasets of drill core samples from the Saale subbasin in Eastern Germany. The samples include the uppermost Rotliegend sandstone (S1), Kupferschiefer (T1) mudstones and lowermost Zechstein Limestone (Ca1), referred as the Kupferschiefer system, from three drill cores (Sangerhausen, Allstedt and Wallendorf).
For further details, see Mohammedyasin et al. (Chemical Geology, when available).