期刊
GEOLOGICAL JOURNAL
卷 46, 期 1, 页码 1-9出版社
WILEY
DOI: 10.1002/gj.1226
关键词
dolomitization; evaporation; Iran; Martin; oil-field brine chemistry; seawater; stable isotopes
资金
- National Iranian South Oil Company
Cation and anion concentrations and oxygen and hydrogen isotopic ratios of brines in the Asmari Formation (Oligocene-early Miocene) from the Martin oil field of southwest Iran were measured to identify the origin of these brines (e.g. salt dissolution vs. seawater evaporation) as well as the involvement of water rock reaction processes in their evolution. Marun brines are characterized by having higher concentrations of calcium (11 000-20 000 mg/L), chlorine (120 000-160 000 mg/L) and bromide (600-1000 mg/L) compared to modern seawater. Samples are also enriched in O-18 relative to seawater, fall to the right of the Global Meteoric Water Line and local rain water, and plot close to the halite brine trajectory on the delta D versus delta O-18 diagram. Geochemical characteristics of Marun brines are inconsistent with a meteoric origin, but instead correspond to residual evaporated seawater modified by water rock interaction, most significantly dolomitization. In addition, anhydrite precipitation or sulphate reduction appears to be important in chemical modification of the Martin brines, as indicated by lower sulphate contents relative to evaporated seawater. Extensive dolomitization, the presence of anhydrite nodules and hid salinity fluid inclusions in the upper parts of the Asmari Formation fit a model whereby the Marun brines likely originated from the seepage reflux of concentrated seawater during the deposition of the overlying Gachsaran Formation evaporites in the Miocene. Copyright (C) 2010 John Wiley & Sons, Ltd.
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