Location and geometry of Alleghanian dispersal-related strike-slip faults in the southern Appalachians

Bobyarchick, Andy R.

doi:10.1130/0091-7613(1988)016<0915:lagoad>2.3.co;2

Cited by 10 publications

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“…It may well be that actual rifting of a continent follows the transcurrent period, as envisaged by Jolivet & Huchon (1989) for the early opening of the Sea of Japan, and several recent studies indicate that transcurrent faulting characteristically occurs late in a collisional event, as in the Alleghenian orogeny of the southern Appalachians (Bobyarchick, 1988). Analysis of the role of fluids in high-grade metamorphism may introduce a new perspective in the study of tectonics which has so far been little exploited.…”

Section: Possible Tectonic Mechanismsmentioning

confidence: 97%

“…Consideration of the most likely source of volatiles (the upper mantle) for deep-crustal metamorphism possibly gives further weight to the mechanism of Katz (1976Katz ( , 1989, in which large-scale transcurrent fault motions, driven by lithospheric plate motions, tap deep-seated volatile sources. It may well be that actual rifting of a continent follows the transcurrent period, as envisaged by Jolivet & Huchon (1989) for the early opening of the Sea of Japan, and several recent studies indicate that transcurrent faulting characteristically occurs late in a collisional event, as in the Alleghenian orogeny of the southern Appalachians (Bobyarchick, 1988). Analysis of the role of fluids in high-grade metamorphism may introduce a new perspective in the study of tectonics which has so far been little exploited.…”

Section: Possible Tectonic Mechanismsmentioning

confidence: 99%

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Charnockitic alteration: evidence for CO₂ infiltration in granulite facies metamorphism

Newton

1992

Journal Metamorphic Geology

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Charnockitic alteration (arrested orthopyroxene formation in biotite-and amphibole-bearing rocks) occurs in high-grade terranes of all ages. Three criteria are used to show that this alteration was produced in many locations by a migrating fluid phase: (i) diffuseness of the alteration-the alteration zones are often quite unlike discrete migmatitic veins; (ii) relation to deformation-most occurrences show alteration closely associated with warping of foliation or dilation cracks; (iii) open-system alterationwhilst some occurrences represent nearly isochemical alteration, slight changes in bulk composition, often loss of mafic constituents and gain of Na and Si, are evident in detailed mass-balance analysis. Y and sometimes Rb are characteristically depleted. Partial melting sometimes accompanied volatile infiltration, as evidenced by more discrete veins and euhedral orthopyroxene. It is quite unlikely, however, that open-system alteration was produced by escape of viscous quartzo-feldspathic melts. Pervasive migration of low-T lamprophyric (mafic-alkaline, C0,-charged) interstitial liquids is a possibility by virtue of their extreme fluidity, but CO, infiltration was needed to generate these liquids. Vapour-deficient dehydration melting is another feasible mechanism of orthopyroxene formation which may have operated in conjunction with CO, infiltration.Characteristic development of charnockitic alteration in some prograde amphibolite to granulite facies transitions, as in the Dharwar Craton of South India, suggests that the alteration is a fundamental feature of the granulite facies metamorphism, implying active and causal participation of migrating fluids. In other high-grade terranes like the Adirondack Mountains of New York, this kind of alteration is rare, and fluid action does not seem to have been important in the metamorphism.A vapour phase participating in charnockitic metamorphism was necessarily one of relatively low H,O, therefore presumably rich in CO,. Consideration of possible large CO, sources leads to the conclusion that emanations from volatile-rich basalts emplaced in the lower crust are the most probable source of charnockitizing fluids. The ultimate source would therefore be enriched subcontinental lithosphere or asthenosphere. The Rb-depleted pyroxene gneiss (charnockitic) terranes may be characteristic of zones of large-scale transcurrent or oblique-motion faults which tap such great depths.

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Section: Possible Tectonic Mechanismsmentioning

confidence: 97%

Section: Possible Tectonic Mechanismsmentioning

confidence: 99%

Charnockitic alteration: evidence for CO₂ infiltration in granulite facies metamorphism

Newton

1992

Journal Metamorphic Geology

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“…Because geologic evidence supports the idea that the Appalachians were an active plate boundary with a component of strike-slip deformation during the middle to late Paleozoic, it is useful to look at modern analogs to see if similar fault geometries can be found at plate boundaries today. Comparisons have been made between the northern Appalachians and the San Andreas fault system (Wilson, 1962;Bobyarchick, 1988;Nance, 1987), which is perhaps the best-studied example of an active transcurrent plate boundary.…”

Section: Discussionmentioning

confidence: 99%

“…Recent work in the central and southern Appalachians has revealed the presence of many major dextral zones in these regions (Fig. 4) (Hill, 1991;Valentino et al, 1994;Bobyarchick, 1988;Vauchez et al, 1993). For example, Valentino et al presented evidence for a minimum of 150 km of late Paleozoic, dextral displacement along the Pleasant Grove-Huntingdon Valley shear system of the central Appalachians.…”

Section: Other Transcurrent Zones Of the Appalachiansmentioning

confidence: 93%

Norumbega fault zone: Part of an orogen-parallel strike-slip system, northern Appalachians

Hubbard¹

1999

Norumbega Fault System of the Northern Appalachians

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The Norumbega fault zone has received much recent attention as a major orogenparallel, dextral fault of late Paleozoic age in the northern Appalachians. The role of this fault in the development of the Appalachian orogen is best understood as part of a transcurrent system that was active in the northern Appalachians or, more likely, in the entire Appalachian orogen. When major fault zones of the northern Appalachians are examined it becomes clear that there are many subparallel, dextral faults that were active between Silurian and Permian time. In the Gaspé peninsula of Quebec there are several major dextral faults, some that were active in the Devonian, the displacements of which may total 150 km. In Maine and New Brunswick dextral transcurrent faults may have accumulated ~150-500 km of displacement. The Cobequid-Chedabucto fault system in Nova Scotia may have had ~540-640 km of dextral displacement. Details of exact amounts of displacement and the precise timing of movement of each fault are not well known, but there are enough data to suggest that the total of dextral transcurrent fault displacement was significant in the late Paleozoic. Data from the central and southern Appalachians also suggest that transcurrent tectonics were an important component of Appalachian orogenesis. The amounts of displacement and even the fault geometries are similar to those found at active transcurrent plate boundaries such as along the San Andreas system. Hubbard, M. S., 1999, Norumbega fault zone: Part of an orogen-parallel strike-slip system, northern Appalachians, in Ludman, A.

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“…Such a mechanism has been invoked to explain deformation around the Brevard zone (Bobyarchick, 1988) and the Kiokee belt (Snoke and Frost, 1990) elsewhere in the southern Appalachians. In both cases, reactivation of old Taconian thrust surfaces and the mechanically weak lithologies within them during Alleghanian deformation was invoked.…”

Section: Tectonic Model For the Maryland Piedmontmentioning

confidence: 99%

Alleghanian transpressional orogenic float in the Baltimore terrane, central Appalachian Piedmont

Gates

Muller²,

Krol³

1999

The Mid-Atlantic Piedmont: Tectonic Missing Link of the Appalachians

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Location and geometry of Alleghanian dispersal-related strike-slip faults in the southern Appalachians

Cited by 10 publications

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Charnockitic alteration: evidence for CO₂ infiltration in granulite facies metamorphism

Charnockitic alteration: evidence for CO₂ infiltration in granulite facies metamorphism

Norumbega fault zone: Part of an orogen-parallel strike-slip system, northern Appalachians

Alleghanian transpressional orogenic float in the Baltimore terrane, central Appalachian Piedmont

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Location and geometry of Alleghanian dispersal-related strike-slip faults in the southern Appalachians

Cited by 10 publications

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Charnockitic alteration: evidence for CO2 infiltration in granulite facies metamorphism

Charnockitic alteration: evidence for CO2 infiltration in granulite facies metamorphism

Norumbega fault zone: Part of an orogen-parallel strike-slip system, northern Appalachians

Alleghanian transpressional orogenic float in the Baltimore terrane, central Appalachian Piedmont

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Charnockitic alteration: evidence for CO₂ infiltration in granulite facies metamorphism

Charnockitic alteration: evidence for CO₂ infiltration in granulite facies metamorphism