Described herein are methods and techniques for utilizing a multiple metal isotope signature as an internal tracers for hydrocarbon source, alteration, and mixing. The multiple metal isotope signature may comprise a ratio of a at least two isotopes of a first metal, a ratio of at least two isotopes of a second metal, and a ratio of at least two isotopes of a third metal from a sample. The isotope ratios of the first, second, and third metal may be integrated to form the multiple metal isotope signature.