Petrographic and geochemical evidence for regional fluid and hydrocarbon migration associated with Late Paleozoic tectonism: Upper Knox Group, Appalachians

Conference · Tue May 01 00:00:00 EDT 1990 · AAPG Bulletin (American Association of Petroleum Geologists); (USA)

OSTI ID:6985597

Montanez, I P ^[1]; Read, J F ^[2]

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1. Univ. of California, Riverside (USA)
2. State Univ., Blacksburg, VA (USA)

Early Ordovician, upper Knox carbonates underwent regional dissolution, replacement dolomitization, and multiple episodes of dolomite cementation during basin-wide fluid migration associated with late Paleozoic tectonism in the central and southern Appalachians. Dolomite cathodoluminescent stratigraphy can be correlated throughout a 100,000-km{sup 2} region and defines a dolomite paragenesis that can be integrated with timing of Mississippi-Valley-type mineralization, authigenic feldspar precipitation, basin-wide illitization, and hydrocarbon migration. Dissolution and fracturing of Knox host, which immediately predated and was synchronous with pervasive replacement dolomitization, resulted in solution vugs, chalky microporosity, cement-supported fabrics, and solution-enlarged, paleokarstic intraformational breccias. Oxygen isotope values ({minus}12.9 to {minus}4.5 {per thousand}) of burial dolomites in conjunction with fluid inclusions define a prograde to retrograde sequence that began during onset of thrusting, peaked following maximum deformation, and continued throughout uplift and denudation. Burial dolomites precipitated from warm (135 to 200{degree}C), saline (13.5-22 wt. % NaCl equiv.) fluids with 180 (+2 to +13 {per thousand}) and trace element compositions typical of basinal brines. The {delta}{sup 13}C values ({minus}3.8 to +3.2 {per thousand}) of all dolomite zones record an input of organic carbon. Trace element and stable isotopic regional trends indicate a southeastern fluid source from the Appalachian orogenic belt and northwesterly fluid flow across the basin. Extensive microfracturing of the Knox host and fluid inclusion data indicate geopressured fluids during maximum deformation. Basin-wide migration of hydrocarbons and dolomitizing and mineralizing brines occurred in response to a large-scale, gravity-driven flow system associated with late Paleozoic deformation.

• OSTI ID: 6985597
• Report Number(s): CONF-900605--
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (USA), Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (USA) Vol. 74:5; ISSN AABUD; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
03 NATURAL GAS
030200 -- Natural Gas-- Reserves
Geology
& Exploration
58 GEOSCIENCES
580000 -- Geosciences
ALKALINE EARTH METAL COMPOUNDS
APPALACHIAN MOUNTAINS
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATE ROCKS
CARBONATES
DIAGENESIS
DISSOLUTION
DOLOMITE
GEOLOGIC DEPOSITS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
GEOLOGY
MAGNESIUM CARBONATES
MAGNESIUM COMPOUNDS
MINERAL RESOURCES
MINERALS
MOUNTAINS
OXYGEN COMPOUNDS
PERMEABILITY
PETROLEUM DEPOSITS
POROSITY
RESERVOIR ROCK
RESOURCES
ROCKS
SEDIMENTARY ROCKS
STRATIGRAPHY
TECTONICS
TRACE AMOUNTS