Kinematic analysis of mélange fabrics: examples and applications from the McHugh Complex, Kenai Peninsula, Alaska

Kusky, Timothy M.; Bradley, Dwight C.

doi:10.1016/s0191-8141(99)00105-4

Cited by 127 publications

(94 citation statements)

References 75 publications

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“…Deformational features include structures formed in extensional and compressive environments during steady-state convergence (arc or back-arc v. accretionary prism) that are overprinted by short regional compressive orogenic events (Kusky & Bradley 1999;Collins 2002a).…”

Section: Characteristics Of Accretionary Orogensmentioning

confidence: 99%

Accretionary orogens through Earth history

et al. 2009

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Accretionary orogens form at intraoceanic and continental margin convergent plate boundaries. They include the supra-subduction zone forearc, magmatic arc and back-arc components. Accretionary orogens can be grouped into retreating and advancing types, based on their kinematic framework and resulting geological character. Retreating orogens (e.g. modern western Pacific) are undergoing long-term extension in response to the site of subduction of the lower plate retreating with respect to the overriding plate and are characterized by back-arc basins. Advancing orogens (e.g. Andes) develop in an environment in which the overriding plate is advancing towards the downgoing plate, resulting in the development of foreland fold and thrust belts and crustal thickening. Cratonization of accretionary orogens occurs during continuing plate convergence and requires transient coupling across the plate boundary with strain concentrated in zones of mechanical and thermal weakening such as the magmatic arc and back-arc region. Potential driving mechanisms for coupling include accretion of buoyant lithosphere (terrane accretion), flat-slab subduction, and rapid absolute upper plate motion overriding the downgoing plate. Accretionary orogens have been active throughout Earth history, extending back until at least 3.2 Ga, and potentially earlier, and provide an important constraint on the initiation of horizontal motion of lithospheric plates on Earth. They have been responsible for major growth of the continental lithosphere through the addition of juvenile magmatic products but are also major sites of consumption and reworking of continental crust through time, through sediment subduction and subduction erosion. It is probable that the rates of crustal growth and destruction are roughly equal, implying that net growth since the Archaean is effectively zero.Classic models of orogens involve a Wilson cycle of ocean opening and closing with orogenesis related to continent-continent collision. These imply that mountain building occurs at the end of a cycle of ocean opening and closing, and marks the termination of subduction, and that the mountain belt should occupy an internal location within an assembled continent (supercontinent). The modern Alpine -Himalayan chain exemplifies the features of this model, lying between the Eurasian and colliding African and Indian plates (Fig.

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Section: Characteristics Of Accretionary Orogensmentioning

confidence: 99%

Accretionary orogens through Earth history

et al. 2009

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“…About 300 m north along the beach, a prominent seastack exposes an argillite-matrix melange containing blocks of greenstone, limestone, pebbly graywacke, and chert. This particular limestone is undated but is typical of the limestone blocks in the McHugh Complex that have yielded Permian fossils of Tethyan affinity (Bradley et al, 1999). Still farther north, at the beginning of a long section of cliffs that continues to the end of the beach, is a belt of melange containing blocks of sandstone and pebbly sandstone that are reminiscent of the Valdez Group (moderately sorted, dominant quartz and feldspar framework grains), and quite different from typical sandstones of the McHugh Complex (poorly sorted, matrix-rich, dominant chert and volcanic framework grains).…”

Section: Description Of Rock Exposuresmentioning

confidence: 97%

“…2). Based on our mapping (Bradley et al, 1999(Bradley et al, ,2000 we subdivide the belt into three main lithological segments, including a fragmental volcaniclastic unit in the east (Fig. 3G-H), a metacarbonate unit in the west, and a mixed metapelitic and volcaniclastic unit between the two (Fig.…”

Section: Seldovia Blueschist Beltmentioning

confidence: 99%

“…The presence of free water in the subduction channel triggers the partial melting of the mantle wedge above the subduction 60' 55 ' ". Kusky et al (1997b) Prehnite-pumpellyite metamorphic facies assemblages are typical (Bradley et al, 1999). The primary melange foliation, ductile shear zones, and metamorphism are all suggested to have formed during subduction-accretion.…”

Section: Introductionmentioning

confidence: 99%

“…to Maastrichtian) age flanks the McHugh Complex on its seaward side. It consists of medium-and thin-bedded graywacke turbidites, black argillite, and minor pebble to cobble conglomerate (Bradley et al, 1999). These strata were probably deposited on the downgoing plate in a deep-sea trench (Nilsen and Zuffa, 1982), and accreted shortly thereafter.…”

Section: Introductionmentioning

confidence: 99%

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P–T and structural constraints of lawsonite and epidote blueschists from Liberty Creek and Seldovia: Tectonic implications for early stages of subduction along the southern Alaska convergent margin

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Ophiolitic mélanges in crustal-scale fault zones: Implications for the Late Palaeozoic tectonic evolution in West Junggar, China

et al. 2014

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The Baijiantan and Darbut ophiolites in West Junggar are exposed in steep fault zones (>70°) containing serpentinite mélange, in contact on either side with regionally distributed Upper Devonian-Lower Carboniferous ocean floor peperitic basalts and overlying sedimentary successions. The ophiolitic mélanges show classic structural features created by strike-slip faulting and consistent shear sense indicators of left-slip kinematics. Sandstone blocks within the mélanges resemble the surrounding sediments in lithology and age, indicating that the ophiolitic mélanges consist of locally derived rocks. The ophiolitic mélanges therefore originated from left-slip fault zones within a remnant basin and are not plate boundaries nor subduction suture zones. Sandstone is the youngest lithology involved in the mélange and provides a maximum age for the mélange of 322 Ma, whereas stitching plutons are younger than 302 Ma. Multiple clusters in zircon ages from single gabbro blocks in the mélange at~375,~360,~354, and~340 Ma are inconsistent with accretionary incorporation of subducting ocean crust but rather suggest that episodic movement of the faults provided pathways for magma from the mantle into magma chambers. Late Paleozoic tectonic evolution of West Junggar involved Late Devonian to Carboniferous relative motion between the Junggar block and West Junggar ocean basin, which triggered the left-slip fault zones within a remnant ocean basin, along which the oceanic crust was disrupted to form linear ophiolitic mélanges. Final filling of this remnant ocean basin and its dismemberment by strike-slip faulting occurred in the late Carboniferous, followed by crustal thickening by juvenile granites at the Carboniferous-Permian boundary.

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Kinematic analysis of mélange fabrics: examples and applications from the McHugh Complex, Kenai Peninsula, Alaska

Cited by 127 publications

References 75 publications

Accretionary orogens through Earth history

Accretionary orogens through Earth history

P–T and structural constraints of lawsonite and epidote blueschists from Liberty Creek and Seldovia: Tectonic implications for early stages of subduction along the southern Alaska convergent margin

Ophiolitic mélanges in crustal-scale fault zones: Implications for the Late Palaeozoic tectonic evolution in West Junggar, China

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