Evaluation of volume of deep mantle outgassing during rifting. Final report, September 1987-February 1989

Technical Report · Fri Mar 01 04:00:00 EST 1991

OSTI ID:6846925

Buck, W R; Steckler, M S

It has been proposed that the major source of natural gas accumulations is inorganic methane outgassed from the mantle. However, for mantle methane to be incorporated into explorable hydrocarbon reservoirs, it must be transported upwards to the near-surface. Volatiles are strongly partitioned into melt phases and can be carried to the near surface by melts. Extensional rifts are sites of mantle partial melting, and thus perspective sites for outflow of mantle methane. The large-scale breaching of the lithosphere that occurs during rifting is a primary conduit for flow of deep mantle volatiles. Non-extension structures that do not breach the lithosphere and are non-volcanic, such as the Siljan ring, are unlikely to contain significant methane. However, not all continental extension leads to mantle melting. Rifts, such as the hydrocarbon-rich Gulf of Suez, that have had no significant mantle melting are unlikely to contain abiogenic hydrocarbons. To get significant mantle melt and volatile transport requires large extensional strain in localized areas, creating asthenospheric upwelling sufficient to induce decompression melting. There could be and probably are large volumes of methane liberated from some continental rifts where there has been melting.

• Research Organization: Columbia Univ., Palisades, NY (United States). Lamont-Doherty Geological Observatory
• OSTI ID: 6846925
• Report Number(s): PB-93-114452/XAB; CNN: GRI-5087-260-1546
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
030200* -- Natural Gas-- Reserves
Geology
& Exploration
ALKANES
EARTH CRUST
EARTH MANTLE
ENGINEERING
FRACTURED RESERVOIRS
GEOLOGIC STRUCTURES
HYDROCARBONS
METHANE
ORGANIC COMPOUNDS
PRODUCTION
RESERVOIR ENGINEERING
RIFT ZONES