Late diagenetic dolomitization of Lower Ordovician, Upper Knox carbonates: A record of the hydrodynamic evolution of the southern Appalachian basin
- Univ. of California, Riverside, CA (United States)
Late diagenetic dolomitization of the Lower Ordovician, Upper Knox Group in the southern Appalachian basin was closely associated with widespread secondary porosity development, hydrocarbon migration, and local Mississippi Valley-type mineralization. Regionally extensive late diagenetic dolomites consist of replacement dolomites and zoned dolomite cements. Late diagenetic replacement dolomites comprise 15 to 50% of all Knox matrix dolomites. Rock buffering of initial dolomitizing fluids and extensive neomorphism of replacement dolomites by subsequent late diagenetic fluids occurred. Nonporous to sucrosic, late diagenetic dolomites have porosities and permeabilities significantly greater than those of early diagenetic replacement dolomites and host limestones. Five generations of dolomite cements can be correlated regionally; zone correlations are interpreted to have time significance and to record regionally extensive diagenetic events. Zoned dolomites, in conjunction with fluid inclusion data, indicate that late diagenetic dolomites precipitated from hot, saline basinal brines that underwent extensive fluid-rock interaction with clastics. Precipitation temperatures of late diagenetic dolomites record a regionally developed, prograde-to-retrograde thermal history. Knox late diagenetic dolomites are interpreted to record the spatial and temporal evolution of large-scale fluid flow systems that developed in response to different burial and tectonic stages of the southern Appalachian basin. The occurrence of zoned dolomite cements in tectonic fractures and breccias, and their close association with noncarbonate diagenetic minerals of Pennsylvanian to Early Permian ages, suggest that most Knox late diagenetic dolomites record deep subsurface fluid migration in response to late Paleozoic Alleghenian tectonism. Late diagenetic matrix dolomites served as long-lived conduits that focused and channeled diagenetic fluids in the deep subsurface. 156 refs., 8 figs., 2 tabs.
- OSTI ID:
- 6750203
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (United States), Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States) Vol. 78:8; ISSN 0149-1423; ISSN AABUD2
- Country of Publication:
- United States
- Language:
- English
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