The influence of deformation partitioning on dissolution and solution transfer in low‐grade tectonic mélange

Hammond, R. L.

doi:10.1111/j.1525-1314.1987.tb00379.x

Cited by 33 publications

(5 citation statements)

References 55 publications

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“…See Karig, 1980 for a complete review). Moreover, mélanges formed in fault or shear zones, also known as "sheared mélanges" (sensu Needham, 1995) and/or "asymmetric mélanges" (sensu Hammond, 1987;Fisher and Byrne, 1987), have been described from the Shimanto belt and southern Scotland (see Needham, 1995 andShibata and and reference therein; Fig. 1 and Table 2).…”

Section: Mélange and Olistostrome Occurrence In Orogenic Belts And Ac...mentioning

confidence: 99%

Mélanges and mélange-forming processes: a historical overview and new concepts

Festa

Pini

Dilek

et al. 2010

International Geology Review

293

177

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Mélanges represent a significant component of collisional and accretionary orogenic belts and occur widely around the world. Since its first introduction and use, the term has evolved to cover both processes (tectonic, sedimentary, and diapiric) and tectonic settings of mélange formation. The meaning and significance of various terms referring to the origin of ‘block-in-matrix chaotic rocks’ are still subject to debate. This study presents a historical overview of the evolving mélange concept and investigates the relationships between mélange types and their tectonic settings of formation. We investigate the contribution of mass-transport versus contractional deformation processes at the onset of mélange formation and throughout the evolution of different mélange types, and the nature of the continuum and transition from broken formations to true tectonic mélanges. A mélange is a mappable chaotic body of mixed rocks with a block-in-matrix fabric whose internal structure and evolution are intimately linked to the structural, sedimentary, magmatic, and metamorphic processes attending its origin. On the basis of a comparative analysis of exhumed, ancient on-land mélanges and modern tectonic environments, where mélange-forming processes are at work, such units are classified into those related to extensional tectonics, passive margin evolution, strike-slip tectonics, subduction zones, collisional tectonics, and intracontinental deformation. Sedimentation and contractional deformation contribute significantly to mélange formation in all these tectonic environments, although the internal structure of deposits is strongly controlled and overprinted by processes that prevail during the last stages of mélange formation in a single tectonic setting. Tectonic mélanges are commonly subordinate to broken formations and are restricted to narrow, elongated-to-coalescent fault zones, large-scale fault zones, and plate boundaries

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Section: Mélange and Olistostrome Occurrence In Orogenic Belts And Ac...mentioning

confidence: 99%

Mélanges and mélange-forming processes: a historical overview and new concepts

Festa

Pini

Dilek

et al. 2010

International Geology Review

293

177

View full text Add to dashboard Cite

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“…Extensive carbonate and quartz veins from accretionary prisms require large volumes of fluid flow through limited crack volumes [Vrolijk et al, 1988;Fisher and Byrne, 1990;Orange et al, 1992]. Additionally, extensive solution in the interior of subduction zones is attributed to leaching of silica from strongly cleaved rocks [Hammond, 1987]. Vein mineralogy and alteration indicate enhanced mobilities of Si, Na, K, Ca, and trace elements in the Cataline Schist of the Franciscan Complex [Bebout and Barton, 1989].…”

Section: Water-rock Interactionsmentioning

confidence: 99%

Fluids in accretionary prisms

Moore¹,

Vrolijk²

1992

Reviews of Geophysics

535

349

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Accretionary prisms are composed of initially saturated sediments caught in subduction zone tectonism. As sediments deform, fluid pressures rise and fluid is expelled, resembling a saturated sponge being tectonically squeezed. Fluid flow from the accretionary prism feeds surface biological cases, precipitates and dissolves minerals, and causes temperature and geochemical anomalies. Structural and metamorphic features are affected at all scales by fluid pressures or fluid flow in accretionary prisms. Accordingly, this dynamic tectonic environment provides an accessible model for fluid/rock interactions occurring at greater crustal depths. Porosity reduction and to a lesser degree mineral dehydration and the breakdown of sedimentary organic matter provide the fluids expelled from accretionary prisms. Mature hydrocarbons expulsed along prism faults indicate deep sources and many tens of kilometers of lateral transport of fluids. Many faults cutting accretionary prisms expel fluids fresher than seawater, presumably generated by dehydration of clay minerals at depth. Models of fluid flow from accretionary prisms use Darcy's law with matrix and fractures/faults being assigned different permeabilities. Fluid pressures in accretionary prisms are commonly high but range from hydrostatic to lithostatic. Matrix or intergranular permeability ranges from less than 10−20 m² to 10−13 m². Fracture permeability probably exceeds 10−12 m². A global estimate of fluid flux into accretionary prisms suggests they recycle the oceans every 500 m.y. Fluid flow out of accretionary prisms occurs by distributed flow through intergranular permeability and along zones of focused flow, typically faults. Focused fluid flow is 3 to 4 orders of magnitude faster than distributed flow, probably representing the mean differences in permeability along these respective expulsion paths. During the geological evolution of accretionary prisms, distributed flow through pore spaces decreases as a result of consolidation and cementation, whereas flow along fracture systems becomes dominant. Although thrust faults are most common in the compressional environment of accretionary prisms, normal and strike‐slip faults are efficient fluid drains, because they are easier to dilate. Observations from both modern and ancient prisms suggest episodic fluid flow which is probably coupled to episodic fault displacement and ultimately to the earthquake cycle.

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“…This resulted in formation of extensive zones of composite S,-S 4 and S 2 -S 4 foliations in an axial planar orientation, without production of a new syn-D 4 cleavage. Bell, 1981;Hammond, 1987). Similarly, Figures 3 and 4, respectively, show relationships for folds of S, and S 2 .…”

Section: D the Fourth Deformation Dmentioning

confidence: 75%

Biotite porphyroblast nucleation and growth: control by microfracture of pre-existing foliations in schists in the Robertson River Metamorphics, Australia

Davis

1996

Geol. Mag.

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A macroscopic fold formed during the fourth deformation, D 4 , in the Robertson River Metamorphics, north Queensland, Australia. Growth of biotite, garnet, staurolite and andalusite porphyroblasts also occurred synchronous with D 4 . Only biotite porphyroblasts have formed preferred alignments across the fold, and they define two dominant orientations. The more common is parallel to D 4 fold axes, which is also parallel to D r D 2 and D 4 intersection lineations. The other varies up to 90° from this within the D 4 axial plane. Mineral elongation lineations do not reflect the extension direction of the deformation in which they formed (D 4 ), but are a function of pre-existing anisotropies in the rock parallel to intersection lineations. Porphyroblast growth is inferred to be a result of microfracturing along favourably oriented linear anisotropies formed by multiple intersection of foliations, as well as parting of the the S, and S 2 foliations.

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The influence of deformation partitioning on dissolution and solution transfer in low‐grade tectonic mélange

Cited by 33 publications

References 55 publications

Mélanges and mélange-forming processes: a historical overview and new concepts

Mélanges and mélange-forming processes: a historical overview and new concepts

Fluids in accretionary prisms

Biotite porphyroblast nucleation and growth: control by microfracture of pre-existing foliations in schists in the Robertson River Metamorphics, Australia

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