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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: Evaporites, Sulfides, and Petroleum
By
Many ancient evaporite deposits exhibit features which
are difficult to explain in the framework of a shallow-water saline or sabkha genetic model. Most of these difficulties can
be overcome by postulating evaporite deposition in a deep-barred
basin filled to sill depth with salt-saturated brine. Such
a deep-basin model appears oceanographically and geologically
reasonable, even though no such basin is known today.
The deep-basin hypothesis has been applied primarily to
the study of ancient "saline giants," but it has geologic
implications which are of almost greater interest. A period of
stagnation and euxinic sedimentation must develop in the
basin prior to inception of salt deposition. During this
period, large, quantities of organic material may settle to the
basin floor where reducing conditions ensure their preservation,
providing a potential petroleum source bed. Sulfate
reduction and proteolytic decay in the anoxic bottom water
yields hydrogen sulfide which chemically will "strip" the
overlying water of dissolved base metals, precipitation extremely insoluble
sulfide of copper, lead, zinc, and iron. Because the volume of seawater which
must be concentrated in the basin by evaporation before salt precipitation can
begin must be at least ten times the volume of the basin, this chemical
stripping action may produce an economically significant deposit of sulfide
minerals. The salts in a deep evaporite basin thus may provide the seal above a petroleum
source bed or the cap over an important ore deposit.
This paragenetic model is shown to conform closely to several well-known sedimentary basins in which salt,
petroleum, and sulfide ores are associated, and offers an essential guide in exploration for new
reserves of petroleum, natural gas, and base-metal ores. End_of_Record - Last_Page 3---------------