Strain fields and foliation trajectories around pre‐, syn‐, and post‐tectonic plutons in coaxially deformed terranes

Mandal, Nibir; Chakraborty, Chandan

doi:10.1002/gj.3350250103

Cited by 10 publications

(4 citation statements)

References 14 publications

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“…The pluton will grow into an elliptical shape because of the regional shortening, with faster expansion perpendicular to the regional shortening direction. The final axial ratio of the pluton is related to the ratio of intrusion-related strain to regional strain (see Mandal & Chakraborty, 1990). As the pluton grows, host-rocks ahead of the pluton ends deforming in the regional strain field will be subjected to a strongly non-coaxial deformation history as the pluton expands.…”

Section: Model Of Synkinematic Granitoid Emplacementmentioning

confidence: 99%

Inter-related plutonism and deformation in South Victoria Land, Antarctica

Cox

1993

Geol. Mag.

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The Lower Palaeozoic Bonney Pluton is a regionally extensive coarse-grained, variably megacrystic, monzodioritic to granitic body that crops out over 1000 km2 in South Victoria Land. It intruded upper amphibolite facies Koettlitz Group metasediments and interlayered orthogneisses. Magmatic fabrics are developed in the centre of the pluton by flow alignment of K-feldspars before the majority of phases had crystallized, whereas solid-state fabrics developed in the pluton margins by ductile–plastic deformation. Structures developed in the host-rocks vary around this elongate northwest–southeast-trending pluton. Upright, tight northwest–southeast-trending macroscopic folds are developed at the sides of the pluton, with axis-parallel stretching lineations and boudinage indicating strong northwest–southeast extension. Broad warps of tight macroscopic folds, and mesoscopic refolded folds, sheath folds and complicated interference patterns characterize areas at the ends of the pluton. Emplacement of the pluton involved radial expansion in a regional northeast–southwest compression, and growth predominantly in the northwest–southeast direction. Superposition of the radial expansion and regional compression resulted in an inhomogeneous strain field at a regional scale, with coaxial strain at the sides of the pluton and non-coaxial strain at the ends. Upright folds developed at the pluton's sides, and became tighter with continued coaxial deformation. Non-coaxial structures developed at the ends of the pluton and were pushed aside by the growing pluton into areas of coaxial deformation, resulting in complex folding, re-folding and sheath folds. Metamorphism of the host-rocks and migmatite development was more intense at the sides of the pluton than near the ends, possibly due to different P-T-t paths of host-rocks around syntectonic plutons.

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Section: Model Of Synkinematic Granitoid Emplacementmentioning

confidence: 99%

Inter-related plutonism and deformation in South Victoria Land, Antarctica

Cox

1993

Geol. Mag.

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“…While all kinds of modelling have tackled tectono-magmatic interaction, including analytical (e.g. Mandal and Chakraborty, 1990) and numerical modelling (e.g. Burov et al, 2003), analogue models where used in particular for the typically cross-scale and four-dimensional problems posed by tectono-magmatic processes (see e.g.…”

Section: Introductionmentioning

confidence: 99%

Shape of plutons in crustal shear zones: A tectono-magmatic guide based on analogue models

Michail¹,

Rudolf²,

Rosenau³

et al. 2022

Preprint

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Plutons in crustal shear zones may exploit inherited structures, interfere with strain localizing or be deformed passively. To constrain the relative timing of such tectono-magmatic constellations in natural settings is not always straightforward. We here present sandbox-type analogue model experiments simulating magma emplacement into simple and transtensional crustal shear zones to test the diagnostic potential of pluton shape with respect to timing and setting. Observations based on surface deformation and intrusion shape exemplify the interplay between evolving and inherited tectonic structures and magma uprising. We observe markedly asymmetric intrusions in association with dikes reflecting the regional stresses, fault pattern and finite strain field. At the same time, the presence of an intrusion modifies the tectonic evolution, but only transiently, resulting in short-lived faults, reactivation and inversion. Diagnostic attributes include the pluton's aspect ratio, its orientation and amplitude as well as dike association. Accordingly, syn-tectonic intrusions show the highest pluton amplitudes and intermediate elongation oriented parallel to between Riedel shears in simple shear, and compression in transtension. Post-tectonic intrusions are least elongated but relatively high and exploit Riedel shears. Pre-tectonic intrusions are characterized by low amplitudes and high aspect ratios parallel to the finite elongation direction. Intrusions in transtensional shear zones are generally of lower amplitude th an those in simple shear zones. Experimental results are tested against observations from natural examples validating the di agnostic potential of pluton shape for the timing and the tectonic setting of the emplacement.

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“…Modelling studies on tectono-magmatic interaction included analytical (e.g. Mandal and Chakraborty, 1990), numerical (e.g. Burov et al, 2003), and analogue approaches (see e.g.…”

Section: Introductionmentioning

confidence: 99%