Geochemistry Alkaline earth metals Bitumens Continental crust Crust Devonian Economic geology Energy sources Etive Complex Genesis Grabens Granites Igneous rocks Isotopes Kerogen Lead Lower crust Macerals Magmas Mantle Maturity Metals O-18/O-16 Old Red Sandstone Organic compounds Organic materials Oxygen Paleozoic Partial melting Pb-206/Pb-204