An example of trondhjemite petrogenesis: the Blakes Ferry pluton, Alabama, U.S.A.

Defant, Marc J.; Drummond, Mark S.; Arthur, J.K.; Ragland, Paul C.

doi:10.1016/0024-4937(88)90007-2

Cited by 10 publications

(3 citation statements)

References 35 publications

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“…It is somewhat more mafic (down to 62 wt% SiO 2 , with more mafic hornblende + clinopyroxenebearing enclaves that are interpreted as cumulates), lacks muscovite, and is older (490-500 Ma) (Drummond et al, 1994). Other plutons that have been described (e.g., Rockford, Almond, and Blakes Ferry, Alabama; Spruce Pine, North Carolina) are similar to those described in this chapter in that they are felsic, peraluminous (generally muscovite-bearing), and low in potassium, ranging from trondhjemite to granodiorite in composition; coeval mafic rocks are absent and initial 87 Sr/ 86 Sr ratios are low (Defant et al, 1988;Drummond et al, 1986Drummond et al, , 1988Russell et al, 1987). Preliminary zircon U-Pb data, although not establishing precise ages, confirm previous interpretations that these plutons are Silurian-Devonian and have some Proterozoic inheritance (Russell et al, 1987).…”

Section: Relationship To Plutonism Elsewhere In the Blue Ridgementioning

confidence: 67%

Low-potassium, trondhjemitic to granodioritic plutonism in the eastern Blue Ridge, southwestern North Carolina-northeastern Georgia

Miller¹,

Fullagar²,

Sando³

et al. 1997

The Nature of Magmatism in the Appalachian Orogen

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Plutons and dikes of the eastern Blue Ridge, North Carolina and northeasternGeorgia, were emplaced syntectonically ca. 400 Ma in the evolving southern Appalachian orogen. These intrusive rocks are uniformly felsic and peraluminous, ranging continuously from trondhjemitic to granodioritic in composition with no associated mafic or intermediate rocks. The trondhjemites are very low in K and in incompatible and high field strength trace elements; are rich in Al, Na, and Sr; and have low 87 Sr/ 86 Sr and δ 18 O and high ε Nd . Granodiorites are less extreme, having elemental and isotopic compositions that are more typical of continent margin granitoids.Their compositions require that the rocks near the trondhjemitic end of the spectrum had a relatively mafic source that was young and derived from depleted mantle. Trace-element modeling and isotopic constraints suggest that this source had the geochemical characteristics of a primitive arc basalt, and that the residue of melting was garnet amphibolite. The granodiorite end of the compositional continuum was derived in large part from the Proterozoic continental basement of the region. The most plausible genetic model involves development of an early Paleozoic magmatic arc, underthrusting of arc rocks during subsequent orogeny, heating of the deep crust as a consequence of crustal thickening, and anatexis within a heterogeneous lower crust. Magmas generated within this crust ranged from trondhjemite to granodiorite, depending upon the source rock, and coalesced in the source region or during ascent to yield the observed compositional continuum.

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Section: Relationship To Plutonism Elsewhere In the Blue Ridgementioning

confidence: 67%

Low-potassium, trondhjemitic to granodioritic plutonism in the eastern Blue Ridge, southwestern North Carolina-northeastern Georgia

Miller¹,

Fullagar²,

Sando³

et al. 1997

The Nature of Magmatism in the Appalachian Orogen

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“…The origin of high-Sr/Y plutons is more controversial. For example, previous authors have argued that they may have originated from (1) partial melting of subducted oceanic crust (Defant et al, 1988), and/or (2) intracrustal melting (Sinha, et al, 1989;Miller et al, 1997;B.V. Miller et al, 2006).…”

Section: Timing and Significance Of Paired Magmatic Belt Constructionmentioning

confidence: 99%

Linking metamorphism, magma generation, and synorogenic sedimentation to crustal thickening during Southern Appalachian mountain building, USA

et al. 2019

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The nature of metamorphism, magma compositions, the spatial distribution of plutons, and foreland sediments reflect, in part, the character and thickness of continental crust. We utilized metamorphic pressure-temperature-time (P-T-t) paths, garnet Sm-Nd ages, zircon U-Pb ages, and pluton compositions to estimate paleocrustal thickness and temporal changes in crustal magma sources in the Blue Ridge of the southernmost Appalachians. Garnet Sm-Nd ages for amphibolite-facies metamorphic rocks range from 331 ± 4 to 320 ± 3 Ma. Low- and high-Sr/Y plutons that intruded these metamorphic rocks have zircon U-Pb ages of 390 ± 1 to 365 ± 1 Ma and 349 ± 2 to 335 ± 1 Ma, respectively. Therefore, garnet growth began during regional metamorphism synchronous with or shortly after intrusion of the youngest high-Sr/Y trondhjemite plutons. Phase diagram sections and thermobarometry indicate that garnet growth initiated at ∼5.8 kbar and 540 °C and grew during temperature increases of 60–100 °C and pressure increases of 2–3 kbar. The older, low-Sr/Y magmas are inferred to have been sourced in the crust at depths <∼30 km, insufficient for garnet to be stable. However, the younger, high-Sr/Y magmas are inferred to have been sourced at >30 km depths where garnet was stable. Hafnium isotopic compositions for all the plutons, but one, exhibit a range from negative initial εHf(i) to weakly positive initial εHf(i), indicating incomplete mixing of dominantly crustal sources. Our data require minimum crustal thicknesses of ∼33 km at 331 Ma; however, Alleghanian crustal thicknesses must have locally reached 39 km, based on crustal reconstruction adding the Alleghanian thrust sheet beneath the eastern Blue Ridge. We infer the presence of hot, tectonically thickened crust during intrusion of the early Alleghanian high-Sr/Y plutons and conclude that garnet growth and plutonism reflect a progressive increase in crustal thickness and depth of magma generation. The crustal thickening was synchronous with deposition of Mississippian to early Pennsylvanian sediments in the foreland basin of the Appalachian orogen between 350 and 320 Ma. This crustal thickening may have preceded emplacement of the Alleghanian thrust sheets onto the North American craton.

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“…;DEFANT et al, 1988;CULLERS & GRAF op. If a high grade metamorphism had reset all Rb-Sr systems, the mylonitic fabric would also have recrystalized.…”

Section: Paleotectonic Settingmentioning

confidence: 99%

Trondhjemites in the Badajoz-Cordoba belt, Sw Spain. Geochemical interpretations and geological implications

Casquero

1990

Geol Rundsch

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ZusammenfassungMehrere geb~nderte GesteinskSrper innerhalb der Valencia de las Torres-Formation der Azuaga Gruppe (Badajoz-Cordoba-Achse) werden als Trondheimite interpretiert. Eine chemische Analyse der wichtigsten Elemente der Proben be-st~tigt, dab die Variabilit~it im Chemismus mit einem einzigen Differentiationsvorgang erkl~rbar ist. Die systematische petrographische und chemische Analyse deutet auf eine Trondheimite-Tonalit~t Abfolge, die hochmetamorphen Gtirtein zugeordnet wird. Ihre Entstehung wird auf teilweises Schmelzen eines Tholeites in einer Subduktionszone herzynischen Alters zu~ckgefiihrt. AbstractSeveral banded bodies of the Valencia de las Torres Formation in the Azuaga Group (Badajoz-Cordoba axis) are defined as trondhjemites. Principal component analysis of major elements shows that the chemical variability of the samples is compatible with a single differentiation process. Systematic study of their petrography and chemistry points to trondhjemite-tonalite series belonging to high grade metamorphic belts and their generation is postulated as being due to partial melting of a tholeite in a subduction zone, for which a hercynian age is suggested. ResumenDiversos cuerpos bandeados de la Formaci6n Valencia de las Torres en el Grupo de Azuaga (Eje Badajoz-Cdrdoba) se definen como trondhjemitas. Del Amilisis de Componentes Principales sobre elementos mayores se desprende que la variabilidad quimica de las muestras es compatible con un s61o proceso de diferenciaci6n. E1 estudio sistemfitico de sus caracteres petrogr~ificos y qu~micos pone de manifiesto su relaci6n con series trondhjemltico-tonaliticas propias de cinturones metamdrficos de alto grado y, coherentemente, se postula su generacidn por fusidn parcial de una thoMta en una zona de subducci6n, para la cual, de acuerdo con los datos geocronoldgicos disponibles se sugiere una edad herdnica. KpaTKOe co~epxanHeMHorHe no~ocqaT~ie Te~a nopo~ B qbopMaIg4n Valencia de la Torres Ha rpyrmbi Azuaga (oc~ Badajoz-Cordoba) nnTepnpeTHpym, KaK TpoH~,eMHThI. XmuH~tecrd~I~ aHaaH3 Ba~mefimrrx 3aeMe~lTOB rip06 nO~lTBep/IHJI, tlTO BapHaI~H XgMrI3ua MO:t~IO O6%~ctn~ITh C IIOMOmr~O o;~Horo e~rmcwBeaRoro npoi~ecca ~Hqbqbepem~aI~rrm IleTporpaqbrmecr, m~ n XUMUqecKrr~ aHa~H3, npoBo~r~-M~Ifi CHCTeMaTrNeCKH, yKa3/,maeT rm TO, qTO TporIIIbe-MIlT-TOHaJItlTOBa~I CBHTa MO)KeT 6blTb OTttecetIa K IIO~ICy BbrCOKOfI cTeneHH MeTaMopqbrr3Ma. OHa o6pa3oBaaac~ B pe3yJil,TaTe qacTia--qHoro pactIslaBneHll,q ToJIeI;ITOB B 3otte 3acact,iBaHI~ B nepHo;~ repIIvntcKoro Bo3pacTa.

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An example of trondhjemite petrogenesis: the Blakes Ferry pluton, Alabama, U.S.A.

Cited by 10 publications

References 35 publications

Low-potassium, trondhjemitic to granodioritic plutonism in the eastern Blue Ridge, southwestern North Carolina-northeastern Georgia

Low-potassium, trondhjemitic to granodioritic plutonism in the eastern Blue Ridge, southwestern North Carolina-northeastern Georgia

Linking metamorphism, magma generation, and synorogenic sedimentation to crustal thickening during Southern Appalachian mountain building, USA

Trondhjemites in the Badajoz-Cordoba belt, Sw Spain. Geochemical interpretations and geological implications

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