Fault-controlled dolomitization in a rift basin
Faculty Advisor
Date
2017
Keywords
dolomitization
Abstract (summary)
There are numerous examples of fault-controlled, so-called hydrothermal dolomite (HTD),
many of which host economic mineral deposits or hydrocarbons, but there remains a lack of
consensus as to how they form. In particular, multiple phases of diagenetic overprinting can
obscure geochemical fingerprints. Study of a Cenozoic succession with a relatively simple
burial history here provides new insights into the development of differentially dolomitized
beds. The Hammam Faraun fault (HFF) block within the Suez Rift, Egypt, hosts both massive and stratabound dolostone bodies. Non-fabric-selective massive dolostone is limited to
the damage zone of the fault, while fabric-selective stratabound dolostone bodies penetrate
nearly 2 km into the footwall. Oligo-Miocene seawater is interpreted to have been drawn
down discrete faults into a deep aquifer and convected upwards along the HFF. Escape of
fluids from the incipient HFF into the lower Thebes Formation led to differential, stratabound
dolomitization. Once the HFF breached the surface, fluid circulation focused along the fault
plane to form younger, massive dolostone bodies. This study provides a snapshot of dolomitization during the earliest phases of extension, unobscured by subsequent recrystallization
and geochemical modification. Contrary to many models, stratabound dolomitization preceded non-stratabound dolomitization. Fluids were hydrothermal, but with little evidence
for rapid cooling and brecciation common to many HTD bodies. These results suggest that
many of the features used to interpret and predict the geometry of HTD in the subsurface
form during later phases of structural deformation, perhaps overprinting less structurally
complex dolomite bodies.
Publication Information
Hollis, Cathy, Eivind Bastesen, Adrian Boyce, Hilary Corlett, Robert Gawthorpe, Jesal Hirani, Atle Rotevatn, and Fiona Whitaker. "Fault-controlled dolomitization in a rift basin." Geology 45, no. 3 (2017): 219-222.
Notes
Item Type
Article
Language
English
Rights
Attribution (CC BY)