Strain in an Archean greenstone belt of Minnesota

doi:10.1016/0040-1951(91)90432-R

Tectonophysics

Volume 190, Issues 2–4, 10 May 1991, Pages 233-268

https://doi.org/10.1016/0040-1951(91)90432-R Get rights and content

Abstract

We measured strain at more than 60 locations in metasedimentary and metavolcanic rocks of the Vermilion district, an E-W trending Archean greenstone belt in Minnesota. Strain ellipsoid orientations and shapes correlate strongly with N-S location in the belt, but magnitudes do not. Flattening strains occur near the present Vermilion fault (which bounds the greenstone belt to the north) with constrictional strains to the south. The observed strain patterns can be mathematically modeled by deformation paths which produce the flattening strains (with west plunging λ₁ axes) by dextral shear of the constrictional strains (with east plunging λ₁ axes). Using reasonable geologic constraints, the shear plane must dip to the north with a subhorizontal shear direction. Structures throughout the district also indicate dextral shear. A geometrical finite element program uses the measured strains to destrain the rocks and find the configuration which most closely satisfies strain compatibility equations. The linear E-W strain patterns and minor rotations about horizontal axes during the deformation preclude origin of the greenstone belt by infolding and shear off the flanks of a rising granitic diapir. By accounting for rotations which result in the (deformed) curvature of the original surface, a true estimate of 50% N-S shortening across the belt can be made. The data and deformation models favor the origin of the Vermilion district rocks at a convergent margin, most likely as a N-dipping subduction zone complex with shallow slab dip. The origin of the constrictional strains remains enigmatic.

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This can result in vertical lineations associated with horizontal shear sense indicators (Fossen and Tikoff, 1993). Such models cannot explain field observations of stretching lineations oriented between vertical, or down dip, and the shear direction (Schultz-Ela and Hudleston, 1991; Robin and Cruden, 1994; Goodwin and Williams, 1996; Dutton, 1997; Jones et al., 1997; Lin et al., 1998). Several updated models were developed to accommodate these observations (Robin and Cruden, 1994; Merle and Gapais, 1997; Jones et al., 1997; Jiang and Williams, 1998; Lin et al., 1998; Czeck and Hudleston, 2003).
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Research paperStrain in an Archean greenstone belt of Minnesota

Abstract

Tectonophysics

Tectonophysics

J. Struct. Geol.

Tectonophysics

Precambrian Res.

J. Struct. Geol.

Tectonophysics

J. Struct. Geol.

J. Struct. Geol.

J. Struct. Geol.

J. Struct. Geol.

J. Struct. Geol.

J. Struct. Geol.

Tectonophysics

Tectonophysics

Tectonophysics

Tectonophysics

Correlation of early recumbent and younger upright folding across the boundary between an Archean gneiss belt and greenstone terrane, northeastern Minnesota

Geology

Multiple folding and pluton emplacement in Archean migmatites of the southern Vermilion Granitic Complex, northeastern Minnesota

Can. J. Earth Sci.

Early recumbent folding across the boundary between the Vermilion Granitic Complex and the Vermilion district, NE Minnesota

Eos, Trans. Am. Geophys. Union

Model for late Mesozoic-early Tertiary tectonics of coastal California and western Mexico and speculations on the origin of the San Andreas fault

Tectonics

Strain analysis of passive elliptical markers: success of destraining methods

J. Struct. Geol.

Description and origin of banded deformation structures. I. Regional strain, local perturbations, and deformation bands

Can. J. Earth Sci.

Spatial integration of strains using finite elements

J. Struct. Geol.

Archaean deformation patterns in southern Africa

Philos. Trans. R. Soc. London, Ser. A

Complex strain patterns developed at the frontal and lateral tips to shear zones and thrust zones

J. Struct. Geol.

Patterns of total and incremental strain in subsiding troughs: experimental centrifuged models of inter-diapir synclines

Can. J. Earth Sci.

The Yilgarn Craton Western Australia: A tectonic synthesis: I

Geochronology in Minnesota

Lower Precambrian rocks of the Gabbro Lake quadrangle, northeastern Minnesota

Minn. Geol. Surv., Spec. Publ., SP-13

Tectonic transpression in Caledonian Spitsbergen

Geol. Mag.

Research paper
Strain in an Archean greenstone belt of Minnesota