DIVERSE APPLICATIONS OF TRACE ELEMENTS IN QUARTZ FOR UNDERSTANDING SEDIMENT PROVENANCE

The ubiquity of quartz in modern and ancient clastic sedimentary rocks makes the mineral potentially useful for interpreting sediment provenance. The factors influencing the trace element content of quartz (particularly Ti and Al) are understood from observations in experimental studies and natural systems, and can be applied to interpreting the crystallization environment of individual quartz grains in sediments and sedimentary rocks.

A recent study by Ackerson et al., 2015¹utilized the trace element content of quartz in bedrock and sediments from the Bega River catchment in New South Wales, Australia to demonstrate that most of the sediments within the river catchment were derived from the catchment’s per-metaluminous (I-type) granitic bedrock. This case study was performed in a relatively simple natural environment— a small drainage basin with well-characterized bedrock lithology. However, the utility of quartz trace element provenance is not limited only to systems like the Bega River drainage. It can also be used to determine source lithologies of modern and ancient sedimentary systems with limited or no bedrock context.

Here we will expand on the methods of Ackerson et al., 2015 by utilizing trace elements in quartz from a modern sedimentary system (the eastern shore of Lake Michigan) where bedrock lithologies and sediment sources are complex and poorly constrained. We will also demonstrate the limits of quartz trace element provenance in ancient sedimentary rocks where the quartz has undergone post-depositional recrystallization. Finally, we will discuss the trace-element signatures imparted on quartz by metamorphic growth, and how metamorphic signatures will manifest in the trace element content of sedimentary quartz grains.

1. Ackerson, M. R., Tailby, N. D. & Watson, E. B. Trace elements in quartz shed light on sediment provenance. Geochem. Geophys. Geosystems 16, 1894–1904 (2015).