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Helium is generated in Earth's crust through the natural radioactive decay of heavy elements, primarily uranium and thorium. This process, known as alpha decay, produces alpha particles, which are helium nuclei (two protons and two neutrons). Over time, these nuclei capture electrons from their surroundings, forming stable helium-4 atoms. Below is a concise explanation of where and how helium is generated in the Earth:1. Primary Generation Process: Radioactive DecaySource Elements: Uranium-238, uranium-235, and thorium-232 undergo alpha decay, releasing helium nuclei as a byproduct.
Location: This occurs in the Earth's crust and mantle, particularly in rocks rich in uranium and thorium, such as:Granitic rocks: High in uranium and thorium content.
Sedimentary rocks: Contain trace amounts of radioactive minerals.
Ore deposits: Uranium and thorium-rich minerals like pitchblende or monazite.
Timescale: Helium accumulates over millions to billions of years in geological formations.
- Accumulation in Geological TrapsTrapping Mechanism: Helium atoms migrate through the Earth's crust and become trapped in porous rock formations alongside natural gas (mostly methane). These formations are typically sealed by impermeable layers (e.g., shale or salt domes) that prevent helium from escaping to the surface.
Key Locations:Natural Gas Fields: Helium is found in economically viable concentrations (0.3–8%) in certain natural gas deposits. Major helium-rich fields include:United States: Hugoton-Panhandle field (Texas, Oklahoma, Kansas).
Qatar: North Dome/South Pars field.
Russia: Siberian gas fields (e.g., Amur region).
Algeria: Hassi R’Mel field.
Geothermal Reservoirs: Some geothermal fields release helium, but extraction is less common.
Concentration: Helium is only economically extractable when concentrated in gas reservoirs. Most helium escapes to the atmosphere and is lost to space due to its light weight.
