Stratigraphy and metamorphism of the Wedowee Group; a reconnaissance

Neathery, Thornton L.; Reynolds, John W.

doi:10.2475/ajs.273.8.723

Cited by 14 publications

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“…Ratios from the Little Bob and Swift mines, which occur in rocks correlative with eastern Blue Ridge lithologles (Cook, 1970;Hurst, 1973) the Wedowee Group of late Precambrian (?) age that is often correlated with the Ashland Supergroup, the host sequence of the Stone Hill deposit, Alabama (Espenshade, 1963;Whittington, 1980;Neathery and Reynolds, 1973;Tull, 1978). LeHuray (1982) discussed the lead isotope ratios of Stone Hill in relation to massive sulfide deposits of the Piedmont geologic province because of isotopic similarities, but pointed out that geologically the Ashland seems to be related to the eastern Blue Ridge, both lithologically and in tectonic position.…”

Section: Syngenetic Deposition Of Ducktown Ores In a Rift Basin Implimentioning

confidence: 97%

Lead and sulfur isotopes and a model for the origin of the Ducktown Deposit, Tennessee

LeHuray¹

1984

Economic Geology

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Strata-bound sulfide deposits at Ducktown, Tennessee, have many characteristics of volcanogenie exhalative deposits but occur in an overwhelmingly sedimentary environment. Lead isotope ratios of galenas and massive pyritic and pyrrhotitic ores fall into three distinct groups that are not related to wall-rock type, type of ore, or to orebody. A positive correlation between the lead and sulfur isotope ratios of galena indicates a relation between sulfur and lead that does not seem to be an effect of metamorphism but is rather an original feature of the ore. The groupings of lead isotope ratios and a possible bimodality of sulfur isotope compositions, as well as the above-mentioned positive correlation, suggest that Ducktown lead and sulfur represent the mixing of two sources. The dominant source of lead was probably U/Pb-enriched clastic sediments. Seawater sulfate may have dominated sulfur contributions from this source. The second source could have been a deep-seated, mafic igneous source tapped by a deep fault associated with late Precambrian rift basin development. The deep source could have provided heat to drive the hydrothermal cell in the sediments, a relatively nonradiogenic component of lead, sulfur with/i34Sz -• 0 per mil, a considerable amount of Cu and Zn, as well as the small amphibolite pods at Ducktown and along strike. Lead isotope studies of contemporaneous rift volcanics, the Mount Rogers Formation, indicate that lead in Ducktown ores could not have been derived from a similar source. Mount Rogers felsic volcanics contain lead derived from a relatively U/Pb-poor, Th/Pbenriched source that appears to have been (granulitized?) Grenville-age basement.Lead-isotope ratios of galenas from the Gossan Lead are similar to those at Ducktown. Other Blue Ridge massive sulfide deposits have less radiogenic 2ø6Pb/2ø4Pb values, but none contain any discernable basement component similar to that of Mount Rogers. Reconnaissance sulfur isotope ratios from other Blue Ridge massive sulfides suggest a tendency toward heavier values than those at Ducktown.

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Section: Syngenetic Deposition Of Ducktown Ores In a Rift Basin Implimentioning

confidence: 97%

Lead and sulfur isotopes and a model for the origin of the Ducktown Deposit, Tennessee

LeHuray¹

1984

Economic Geology

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“…This is surprising because the Alexander City fault zone is restricted to the eastern Blue Ridge, and it is generally not considered a "fundamental" southern Appalachian fault zone. The geometry and kinematics of the Alexander City fault zone has not been examined in detail and movement sense has been suggested as reverse slip (Bentley and Neathery, 1970;Neathery and Reynolds, 1973;Osborne et al, 1988), right slip (Guthrie, 1995), and normal slip (Drummond, 1986;Drummond et al 1994Drummond et al , 1997. Our observations are that it dips steeply to the southeast and exhibits oblique-normal but predominantly dextral shear, and it is cut by later (Mesozoic?)…”

Section: Discussion and Directions For Future Studiesmentioning

confidence: 64%

“…These faults may be a suture equivalent to the Allatoona-Hayesville-Soque River fault system farther northeast. The Goodwater-Enitachopco fault (Neathery and Reynolds, 1973;Tull, 1978;McConnell and Costello, 1980;Raymond et al, 1988;Tull and Holm, 2005) has cut the frontal edge of the eastern Blue Ridge thrust sheet, leaving two "marooned" structural salients that are partitioned by the Millerville reentrant and contain correlative sequences of migmatitic Ashland Supergroup (i.e., northern salient is Mad Indian above Poe Bridge Mountain Groups, and southern salient is Hatchet Creek above Higgins Ferry Groups; Fig. 2).…”

Section: Geologic Settingmentioning

confidence: 97%

Untitled

et al. 2013

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We dedicate this paper to the memory of coauthor Isidore (Izzy) Zietz, who died at age 93 while this paper was in review. After contributing to the early theoretical foundation for analysis of airborne magnetic surveys, Izzy became a leading advocate for aeromagnetic survey acquisition and interpretation throughout the U.S., combining surveys into regional, state, and national maps, and working with regional geologists in interpreting geophysical anomalies. Like many geologists, we have been energized by Izzy's contagious enthusiasm for using magnetic and gravity anomalies to delineate and characterize major tectonic features. Lessons from working with him on data from Alabama and elsewhere over the years will continue to infl uence our appreciation and understanding of aeromagnetic and gravity anomalies for interpreting the Earth's upper crust."Magnetics is never good, and gravity is even worse!" "…all of it can just be dashed." -Isidore Zietz ABSTRACT Aeromagnetic and gravity data sets obtained for Alabama (United States) have been digitally merged and fi ltered to enhance upper-crustal anomalies. Beneath the Appalachian Basin in northwestern Alabama, broad deep-crustal anomalies of the continental interior include the Grenville front and New York-Alabama lineament (dextral fault). Toward the east and south, high-angle discordance between the northeast-trending Appalachians and the east-west-trending wedge of overlapping Mesozoic and Cenozoic Gulf Coastal Plain sediments reveals how bedrock geophysical signatures progressively change with deeper burial. Highfrequency magnetic anomalies in the Appalachian deformed domain (ADD) correspond to amphibolites and mylonites outlining terranes, while broader, lower-amplitude domains include Paleozoic intrusive bodies and Grenville basement gneiss. Fundamental ADD structures (e.g., the Alexander City, Towaliga, and Goat Rock-Bartletts Ferry faults) can be traced southward beneath the Gulf Coastal Plain to the suture with Gondwanan crust of the Suwannee terrane. Within the ADD, there is clear magnetic distinction between Laurentian crust and the strongly linear, high-frequency magnetic highs of peri-Gondwanan (Carolina-Uchee) arc terranes. The contact (Central Piedmont suture) corresponds to surface exposures of the Bartletts Ferry fault. ADD magnetic and gravity signatures are truncated by the eastwest-trending Altamaha magnetic low associated with the Suwannee suture. Arcuate northeast-trending magnetic linears of the Suwannee terrane refl ect internal structure and Mesozoic failed-rift trends. Geophysical data can be used to make inferences on surface and subsurface geology and vice versa, which has applicability anywhere that bedrock is exposed or concealed beneath essentially non-magnetic sedimentary cover.

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“…The protolith consisted of tholeiitic basaltic pyroclas-tics and lavas intermixed with lesser amounts (~25%) of calc-alkaline dacitic ash fl ows up to 150 m thick. The base of the unit, previously thought to be a stratigraphic boundary (Neathery and Reynolds, 1973;Tull and Stow, 1980), is a cryptic thrust overlying units of the middle Paleozoic Laurentian shelf (McClellan et al, 2007;Tull et al, 2007: Barineau, 2009. This tectonically emplaced metavolcanic complex is contained within a major postmetamorphic footwall thrust duplex (Hollins Line thrust system) that emplaced medium-to high-grade rocks of the eastern Blue Ridge's Ashland Supergroup above the Hillabee (Tull et al, 2007;Barineau, 2009;.…”

Section: Hillabee Greenstonementioning

confidence: 99%

“…2; Adams, 1926;Neathery and Reynolds 1973) is considered to be the oldest preserved sequence within the Wedowee-Emuckfaw-Dahlonega basin, and it consists of a several-kilometerthick monotonous sequence of predominantly thinly laminated, locally highly carbonaceous psammo-pelitic schist, intercalated and locally rhythmically interbedded with minor metapsammites and micaceous quartzite in layers a few meters thick, with rare calc-silicate layers. Orthoamphibolite layers (<5% of the unit), 10 to >100 m thick, occur in the medial and upper parts of the unit.…”

Section: Wedowee Groupmentioning

confidence: 99%

Early to Middle Ordovician back-arc basin in the southern Appalachian Blue Ridge: Characteristics, extent, and tectonic significance

Tull¹,

Holm-Denoma²,

Barineau³

2014

Geological Society of America Bulletin

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Fault-dismembered segments of a distinctive, extensive, highly allochthonous, and tectonically signifi cant Ordovician (ca. 480-460 Ma) basin, which contains suites of bimodal metavolcanic rocks, associated base metal deposits, and thick immature deepwater (turbiditic) metasediments, occur in parts of the southern Appalachian Talladega belt, eastern Blue Ridge, and Inner Piedmont of Alabama, Georgia, and North and South Carolina. The basin's predominantly metasedi mentary strata display geochemical and isotopic evidence of a mixed provenance, including an adjacent active volcanic arc and a provenance of mica (clay)-rich sedimentary and felsic plutonic rocks consistent with Laurentian (Grenvillian) upper-crustal continental rocks and their passive-margin cover sequences. Geochemical characteristics of the subordinate intercalated bimodal meta volcanic rocks indicate formation in a supra subduction environment, most likely a back-arc basin, whereas characteristics of metasedimentary units suggest deposition above Neoproterozoic rift and outer-margin lower Paleozoic slope and rise sediments within a marginal basin along Ordovician Laurentia's Iapetus margin. This tectonic setting indicates that southernmost Appalachian Ordovician orogenesis (Taconic orogeny) began as an extensional accretionary orogen along the outer margin of Laurentia, rather than in an exotic (non-Laurentian) arc collisional setting. B-type subduction polarity requires that the associated arc-trench system formed southeast of the palinspastic position of the backarc basin. This scenario can explain several unique features of the southern Appalachian Taconic orogen, including: the palinspastic geographic ordering of key tectonic elements (i.e., back-arc, arc, etc.), and a lack of (1) an obducted arc sensu stricto on the Laurentian margin, (2) widespread Ordovician regional metamorphism, and (3) Taconic klippen to supply detritus to the Taconic foreland basin.

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Stratigraphy and metamorphism of the Wedowee Group; a reconnaissance

Cited by 14 publications

References 0 publications

Lead and sulfur isotopes and a model for the origin of the Ducktown Deposit, Tennessee

Lead and sulfur isotopes and a model for the origin of the Ducktown Deposit, Tennessee

Untitled

Early to Middle Ordovician back-arc basin in the southern Appalachian Blue Ridge: Characteristics, extent, and tectonic significance

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