Provenance Analysis

Provenance: the lithological (and chemical, isotopic, age) characteristics of the source region for a sedimentary rock

Composition of sediments (mostly sandstones) can tell you about the location, tectonic setting, climate, etc. of the source area and the transport mechanism and pathway

Mechanical weathering

No changes to mineralogical composition of sediment produced from rock

Chemical weathering

Mineralogical composition of sediment differs from parent rock

Chemical weathering dominates in warm, wet climates

Mineral stability during weathering follows Bowen’s reaction series

Compositional Maturity: degree to which sediment contains only resistant grains (quartz and stable heavy minerals like magnetite, apatite, rutile, zircon)

Textural Maturity: based on presence of clay, sorting, and rounding

More transport leads to greater textural maturity

Rock particles can indicate the tectonic setting of the source

QFL diagram plots relative percentages of quartz, feldspar, and lithics

If chert or quartzite are abundant, treat them as lithics and plot monocrystalline quartz (Qm)

Qp = polycrystalline quartz (chert, quartzite)

Lvm = volcanic and metavolcanic lithics

Lsm = sedimentary and metased lithics

Lm = metamorphic lithics

Lv = volcanic lithics

Ls = sedimentary lithics

Other ternary plots (QpLvmLsm and LmLvLs) subdivide and plot just the lithic components for discrimination of tectonic settings

Sm/Nd isotopes

Negative εNd values found in continental crust (Nd system has been separated from Sm “enriched” mantle for long time)

Positive εNd values are commonly found in mantle derived melts

Strontium isotopes (87Sr/86Sr)

Rubidium (87Rb) strongly partitions into continental magmas and decays to 87Sr

Continental crust is enriched in 87Sr/86Sr

Primitive mantle and magma have low 87Sr/86Sr

Ratio tracks continental influence on source rocks

Detrital zircon U-Pb

Single-crystal age dates give age of rocks in source region