Insights into past tectonism from authigenic quartz

Abstract

Authigenic quartz grains carry information that is diagnostic for the thermal history and thereby the burial depth and uplift of sediments. Recycled quartz grains with embayed or rounded authigenic remnants have been observed globally, but the value of these grains in unravelling past tectonism is presently underexplored. In this study, we launch a new method to demonstrate that cathodoluminescence (CL) in combination with fluid inclusion data and textural characteristics of authigenic quartz can provide important information about past tectonic activity. Vital in the method is the realisation that recycled quartz grains can be distinguished from other quartz grains by their geochemical CL fingerprint, allowing tracking of uplifted source terrains in a direction towards higher fractions of the recycled grains. Furthermore, regional mapping can reveal both intra-basinal recycling as well as recycled grains transported into the basin from external sources. The new proposed method is simple and does not require more than a standard Scanning Electron Microscope equipped with a CL detector, available at many geoscientific institutions worldwide. This innovative approach applies to a wide section of geoscientific disciplines, and complement and supplement other conventional methods used for unravelling past tectonism.