Spectral and geochemical characterization of onshore hydrocarbon seep-induced alteration in the Dezful embayment, southwest Iran

Detection of Alteration Induced by Onshore Gas Seeps from ASTER and WorldView-2 Data

“…Thomas [22] mentioned that the Gach-e-tursh represents an association of oxidizing petroleum seep, gypsum, jarosite, sulphuric acid and sulphur. Salati et al [23] proposed generalized models of spectral and geochemical alterations in the Dezful Embayment. In this petroleum basin, hydrocarbon seeps and their associated alterations are spatially associated with the Gachsaran cap rock and the Mishan Formation [20].…”

“…In the present study, an area within the Mishan Formation (the Mamatin area) that was affected by macro gas seeps was chosen to be investigated by multispectral ASTER and WV-2 remote sensing. The alteration zone studied by Salati et al [23] covers an area of about 55 m × 20 m within the marly limestone formation (Figure 2). Within this formation, gas-induced alterations have distinctive spectral and geochemical signatures [23].…”

“…The alteration zone studied by Salati et al [23] covers an area of about 55 m × 20 m within the marly limestone formation (Figure 2). Within this formation, gas-induced alterations have distinctive spectral and geochemical signatures [23]. The reaction between H 2 S and calcite lead to the precipitation of gypsum and native sulphur.…”

“…The H 2 S originates from bacterial reductions of sulphate minerals in the Gachsaran cap rock underlying the Mishan Formation. Gas-induced alterations were spectrally characterized by the presence of gypsum, while unaltered marly limestones showed spectra that are typical of calcite [23].…”

“…Field samples were collected from the alteration zone and the surrounding unaltered rock, previously described by [23]. Reflectance spectra from rock samples were measured in the laboratory using an ASD FieldSpec with a 450-to 2500-nm wavelength range at 3-10-nm resolution and a contact probe as the fore-optic.…”