Phytane

Phytane is a diterpene molecule that plays a significant role in the field of geochemistry and biogeochemistry. It is a saturated 20-carbon hydrocarbon with the chemical formula C20H42. Phytane is considered an important biomarker in the study of ancient sedimentary rocks and petroleum because it is derived from the phytol side chain of chlorophyll, which suggests the presence of photosynthetic life at the time the sediment was deposited.

Structure and Properties

Phytane is a branched hydrocarbon, which contributes to its stability over geological timescales. Its structure is characterized by the lack of double bonds, making it less reactive and more resistant to oxidation processes. This stability is crucial for its preservation in geological samples.

Source and Formation

Phytane can originate from the diagenetic (post-depositional) alteration of phytol, a component of chlorophyll. During the decomposition of biomass in sediments, microorganisms can remove the phytol's double bond and its alcohol group, resulting in the formation of phytane. This process can occur under both oxic and anoxic conditions, making phytane a common component in a wide range of sedimentary environments.

Geochemical Significance

In geochemistry, phytane is used as a biomarker to infer past environmental conditions. The presence of phytane in sedimentary rocks can indicate the former presence of photosynthetic life, providing insights into the paleoenvironment. Additionally, the ratio of phytane to its isomer pristane (another biomarker derived from phytol) is often used to interpret the redox conditions of ancient depositional environments. A high phytane/pristane ratio can suggest anoxic conditions, which is valuable information for reconstructing past climates and oceanic conditions.

Applications

Beyond its use in paleoenvironmental reconstructions, phytane has applications in the petroleum industry. As a biomarker, it can help in correlating and characterizing oil and gas reservoirs. Understanding the distribution of phytane and other biomarkers in petroleum can aid in identifying potential sources of hydrocarbon deposits and in reconstructing the geological history of an area.

Research and Challenges

Research into phytane and other biomarkers continues to evolve, with new analytical techniques allowing for more precise interpretations of ancient environments. However, challenges remain in fully understanding the pathways of phytane formation and alteration over geological time, as well as in distinguishing between biogenic and abiogenic sources of phytane in geological samples.

See Also

• Biomarker (petroleum)
• Sedimentary rock
• Geochemistry
• Biogeochemistry
• Chlorophyll
• Pristane