Reference

The theory of hydrocarbons being generated in the Earth's mantle is supported by several pieces of evidence:

1. The presence of hydrocarbon inclusions in diamonds, carbonado, and kimberlites suggests that hydrocarbon fluids were involved in the formation of these minerals in the mantle.
2. Deep mantle xenoliths, found in various igneous rocks, contain hydrocarbon inclusions, indicating the presence of hydrocarbons in the upper mantle.
3. Laboratory experiments have shown that hydrocarbons can form under the high-pressure, high-temperature conditions of the upper mantle.
4. The process of serpentinization, which occurs in the upper mantle, produces hydrocarbons that are important for microorganisms at the seafloor.
5. Methane has been shown to form from diamond, graphite, or glassy carbon and hydrogen under conditions similar to the outer layers of the Earth's mantle.

These findings support the theory that hydrocarbons can be generated abiotically deep within the Earth and may contribute to petroleum reserves. For more detailed information, refer to the sources provided, such as the articles on InTechOpen, NCBI, and IOP Science.