The Role of Fluids in Crustal Processes (1990) / Chapter Skim
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8. COCORP and Fluids in the Crust
8. COCORP and Fluids in the Crust
Pages 128-139
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From page 128... ...
Third, new insights into structures suggest that tectonic models include inferences about the role of fluids in the crust. For example, fluids expelled tectonically from sediments buried in erogenic belts may play a role in migration of hydrocarbons, transport of minerals, diagenesis, crustal rheology, chemical Demagnetization, and a variety of other phenomena.
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From page 129... ...
Later, while profiling in Death Valley, COCORP detected a strong reflection that in many ways resembles that type example from beneath the Rio Grande Rift. The Death Valley reflector is at about the same depth, is nearly horizontal, and is in a similar extensional tectonic environment.
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From page 130... ...
These strong mid-crustal reflectors, coupled with additional observations by COCORP and by others on various aspects of the buried continental crust, are prompting new speculation about the formation and evolution of the deep crust and its role in the evolution of modern surface geology. The subject of the structure, composition, evolution, and tectonics of the deep continental crust and uppermost mantle is a particularly important and exciting one at present.
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From page 131... ...
It would be risky, for example, to base hydrologic or geochemical studies of the crust on the concept that all basement reflectors necessar 131 fly indicate fluid-filled fractures of the crust, but it would also be risky to ignore the possibility that many of them do. A SYNTHESIS OF INFORMATION ON CRUSTAL STRUCTURE, TECTONICS, AND FLUIDS IN THE CRUST The COCORP data provide information on the structure and evolution of the continental crust.
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From page 132... ...
Put another way, the margin of one landmass is commonly buried beneath the accretionary wedge on the leading edge of the other. According to the hypothesis, fluids from the sediments of the buried continental margin are expelled and travel toward the interior of the partially subducted continent carrying heat, minerals, and organic compounds (Figure 8.3~.
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From page 133... ...
In other words, dolomitization is apparently related to MVT ores in some cases because of related origin of both as a consequence of mineralizing migrating brines that may have originated in erogenic belts. Thus, brines producing the MVT deposits of Missouri likely originated during the Ouachita orogeny to the south, although the possibility of some effects from the Appalachian orogen to the east must also be kept in mind.
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From page 134... ...
Much evidence from fluid inclusion studies supports the concept of tectonic expulsion of fluids from erogenic belts. Certain aspects of diagenesis, a term used here in its general sense to include epigenesis, of sediments may be a consequence of migrating tectonic fluids.
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From page 135... ...
Gas in the Ouachita hydrocarbon province tends to occur near the orogen, oil farther away. The hypothesis suggests that some hydrocarbons of this province have not migrated much, but others have traveled as organics or hydrocarbons long distances from where the former continental margin lies buried beneath the Ouachita orogen.
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From page 136... ...
. He called upon burial of a foreland basin delta, with source to the east, beneath thrust Appalachians, Alberta, the Cordilleran province, the West TexasOklahoma-Kansas province, and possibly the Illinois basin are in part a consequence of fluid migration from nearby erogenic belts according to the hypothesis discussed here.
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From page 137... ...
The hydrocarbons of the Middle East, as was pointed out by Dickinson (1974) in one of the first and most important early attempts to relate hydrocarbon accumulations to plate tectonics, likely migrated updip to the west from the Zagros erogenic belt as a consequence of subduction of the leading edge of the African continent, which then included the Arabian peninsula, to the east beneath the overriding Asian plate.
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From page 138... ...
BeLkin (1985~. Evidence for Alleghenian brine migration in the central and southern Appalachians: Implications for Mississippi Valleytype sulfide mineralization, Geological Society of America Abstracts with Programs 17, 606.
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From page 139... ...
(1985~. Rb-Sr dating of diagenesis and source age of clays in Upper Devonian black shales of Texas, Geological Society of America Bulletin 96, 1043-1049.
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