Tectonic map of the southern and central Appalachians: A tale of three orogens and a complete Wilson cycle

Hatcher, Robert D.; Bream, Brendan R.; Merschat, Arthur J.

doi:10.1130/2007.1200(29)

Cited by 65 publications

(104 citation statements)

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“…The granitic rocks and their enclosing country rocks are part of the Spruce Pine thrust block, the structurally highest thrust sheet in the northern part of the Blue Ridge Belt of western North Carolina (Butler 1973;Stewart et al 1997). Rocks of the Spruce Pine thrust block are part of the Tugaloo Terrane of Hatcher et al (2005Hatcher et al ( , 2007, an exotic terrane composed of metasediments, interlayered amphibolite, small bodies of ultramafic rock and a few mafic-ultramafic complexes accreted to North America during the Taconic Orogeny. Schists and gneisses preserve a polyphase metamorphic history (Fig.…”

Section: Geological Backgroundmentioning

confidence: 99%

Mineralogy and petrogenesis of pegmatites in the Spruce Pine District, North Carolina, USA

Swanson¹,

Veal²

2012

J. Geosci.

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Granitic rocks (mainly granodiorites) of the Spruce Pine Plutonic Suite occur as small plutons and numerous pegmatite bodies intruded into amphibolite-grade schists and gneisses of the Ashe Formation. Intrusion ages range from 377 to 404 Ma and are near the peak of amphibolite-facies metamorphism in the country rocks. The granodiorites have a mortar texture with coarse (~ 1 cm) grains of feldspar, quartz and muscovite enclosed in a finer grained matrix of the same phases. Large (10-30 cm) crystals of perthitic K-feldspar and plagioclase occur in the granodiorite. Pegmatites occur within the granodiorite and as isolated intrusions within the country rocks. Contacts between pegmatites and host granodiorites range from sharp, cross-cutting to completely gradational. Some of the plutons contain up to 50 % pegmatite. Pegmatite mineralogy is similar to the granodiorites; major amounts of feldspars and quartz, accessory amounts of muscovite, garnet, and epidote. Secondary minerals, formed by subsolidus recrystallization, include epidote, muscovite, quartz, and grossular garnet. A few of the pegmatites are more fractionated and contain tourmaline and beryl. Compositions of feldspars, muscovite, and garnet show some regional variation, but are generally similar for pegmatites and associated granodiorite. About half of the pegmatites are unzoned. Zoning in the pegmatites is simple with a quartz core, an intermediate zone of graphic granite, plagioclase and muscovite and an outer finer grained zone that locally shows mineral layering parallel to the contact. The abundance of pegmatitic textures relative to granitoid textures in the Spruce Pine Plutonic Suite is related to the depth of crystallization. Spruce Pine granitoids crystallized at depths of 20-30 km (0.7 to 1.1 GPa ) based on feldspar thermobarometry and experimentally determined melting relations. Skeletal crystals of quartz and feldspar along with plumose muscovite clusters are common in the Spruce Pine pegmatites. Water content of magmas at such high pressures can be high. The subtle transition from granitic to pegmatitic texture so common at Spruce Pine (and in other deep-seated systems) was probably related to the development of zones of water-enriched magma and delayed nucleation in the hydrous melts. Deformation (evidenced by mortar texture) of the Spruce Pine Plutonic Suite was related to later regional deformation.

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Section: Geological Backgroundmentioning

confidence: 99%

Mineralogy and petrogenesis of pegmatites in the Spruce Pine District, North Carolina, USA

Swanson¹,

Veal²

2012

J. Geosci.

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“…The Southern Appalachians are the product of diachronous, largely oblique collision of the North American craton with Africa and a number of continental fragments and island arcs (Hatcher, , 2002(Hatcher, , 2010Hatcher et al, 2007). Closing of various ocean basins took place more or less continuously from the Early Ordovician to the Permian, but deformation was most intense during the Taconic (480-450 Ma), , and Alleghanian (330-260 Ma) orogenies.…”

Section: Geologic Settingmentioning

confidence: 99%

“…Along the southeast fl ank of the orogen, exposures of the Carolina terrane (the Carolina superterrane of Hibbard et al, 2002) have been interpreted as an island-arc sequence (Whitney et al, 1978) developed on basement of uncertain affi nity (Secor et al, 1986;Dallmeyer, 1989;Hatcher et al, 2007). The sequence was metamorphosed in the Cambrian (Dennis and Wright, 1997) and again in the Neoacadian (Hibbard et al, 2002).…”

Section: Geologic Settingmentioning

confidence: 99%

“…Higher-grade (amphibolite facies) rocks of the western Carolina superterrane and Kiokee belt alternate with greenschist and lower-grade rocks of the central and easternmost portions of the superterrane. The whole assembly docked with Laurentia in a transpressional event during the Neoacadian and experienced additional northwest-directed thrusting during the Alleghanian orogeny (Hibbard et al, 2002;Hatcher et al, 2007).…”

Section: Geologic Settingmentioning

confidence: 99%

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Isostatic compensation for a portion of the Southern Appalachians: Evidence from a reconnaissance study using wide-angle, three-component seismic soundings

Hawman

Khalifa

Baker

2011

Geological Society of America Bulletin

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Wide-angle refl ections generated by fi ve controlled blasts and over 110 timed quarry blasts in the Southern Appalachians were used to test models for isostatic compensation of topog raphy. The profi les cross the Appa lachian gravity gradient and gravity low and sample the highest elevations within the orogen. Migration of P, SV, and SH refl ections suggests that crustal thickness varies from 35 to 39 km within the coastal plain and 37-39 km within the Carolina terrane. It increases northwestward from 40 to 45 km across the Inner Piedmont, and then thickens to 50-52 km along the southeastern fl ank of the Blue Ridge Mountains. Crustal thickness within the Blue Ridge Mountains ranges from 47 to 56 km. Receiver functions for broadband stations GOGA and MYNC show a similar pattern in crustal thickness. Assuming Airy compensation, the correlation between elevation and Moho depth suggests a range of 50-150 kg/m 3 for the density contrast between the crustal root and mantle. The greatest Moho depths are associated not with the tallest peaks, but rather with the broadest portions of the mountain chain. This observation is consistent with regional bending of the lithosphere. However, the planar basement surface suggests that the root either predates Alleghanian thrusting, and therefore is unrelated to the present topography, or formed in response to some other mechanism. Bounds on curvature of the basement surface suggest a lower bound of 30-40 km for the effective elastic thickness of the lithosphere. This is consistent with previous estimates for the southern Appalachians based on analysis of gravity data.

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“…In that position, fl uvial strata of the Ionia Formation could have been deposited by northern tributaries but not by southern tributaries of the paleoriver system. Accreted Neoproterozoic terranes of peri-Gondwanan origin form a wide and prominent belt in the central and southern Appalachian region (Hatcher et al, 2007). Where uplifted along Atlantic rift highlands, they could have contributed signifi cant amounts of detritus to the headwaters and southern tributaries of the transcontinental paleoriver.…”

Section: Provenance Relationsmentioning

confidence: 99%

Detrital zircons from fluvial Jurassic strata of the Michigan basin: Implications for the transcontinental Jurassic paleoriver hypothesis

Dickinson¹,

Gehrels²,

Marzolf³

2010

Geology

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The U-Pb age spectrum of detrital zircons in sandstone of the fl uvial Middle Jurassic Ionia Formation in the Michigan basin, United States, resembles the age spectra in Jurassic eolianites of the Colorado Plateau, except that a Neoproterozoic (725-510 Ma) subpopulation present in the eolianites is absent from the Michigan basin strata. The detrital zircon data are compatible with the hypothesis that the Ionia Formation was deposited by northern tributaries of a transcontinental Jurassic paleoriver system that transported detritus from headwaters in Atlantic rift highlands of the Appalachian region to fl oodplains and deltas in the present northern Rocky Mountains region. Previous detrital zircon studies have indicated that sedimented lowlands in that paleogeographic position were defl ated by paleowinds to feed eolian sand southward (in present coordinates) into the Colorado Plateau ergs (sand seas).

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Tectonic map of the southern and central Appalachians: A tale of three orogens and a complete Wilson cycle

Cited by 65 publications

References 0 publications

Mineralogy and petrogenesis of pegmatites in the Spruce Pine District, North Carolina, USA

Mineralogy and petrogenesis of pegmatites in the Spruce Pine District, North Carolina, USA

Isostatic compensation for a portion of the Southern Appalachians: Evidence from a reconnaissance study using wide-angle, three-component seismic soundings

Detrital zircons from fluvial Jurassic strata of the Michigan basin: Implications for the transcontinental Jurassic paleoriver hypothesis

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