Cordilleran metamorphic core complexes: An overview

Coney, Peter J.

doi:10.1130/mem153-p7

Cited by 383 publications

(243 citation statements)

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“…Studies of metamorphic core complexes (e.g. Malavieille, 1987a,b;Coney, 1980;Hill et al, 1992) show that shallowly dipping gneissic foliations may develop during crustal extension. In such settings, shear fabrics along extensional detachments may overprint subhorizontal flattening foliations (e.g.…”

Section: Origin Of Shallowly Dipping Foliations In Highgrade Gneiss Tmentioning

confidence: 99%

Mechanisms for folding of high-grade rocks in extensional tectonic settings

Harris

Koyi

Fossen

2002

Earth-Science Reviews

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This review of structures developed in extensional high-grade terrains, combined with results of centrifuge analogue modelling, illustrates the range of fold styles and mechanisms for folding of amphibolite to granulite facies rocks during rifting or the collapse of a thrust-thickened orogen. Several extensional fold mechanisms (such as folding within detachment shear zones) are similar to those in contractional settings. The metamorphic P -T -t path, and not fold style or mode of formation, is therefore required to determine the tectonic setting in which some folds developed. Other mechanisms such as rollover above and folding between listric normal shear zones, and folding due to isostatic adjustments during crustal thinning, are unique to extensional tectonic settings. Several mechanisms for folding during crustal extension produce structures that could easily be misinterpreted as implying regional contraction and hence lead to errors in their tectonic interpretation. It is shown that isoclinal recumbent folds refolded by open, upright folds may develop during regional extension in the deep crust. Folds with a thrust sense of asymmetry can develop due to high shear strains within an extensional detachment, or from enhanced back-rotation of layers between normal shear zones. During back-rotation folding, layers rotated into the shortening field undergo further buckle folding, and all may rotate towards orthogonality to the maximum shortening direction. This mechanism explains the presence of many transposed folds, folds with axial planar pegmatites and folds with opposite vergence in extensional terrains. Examples of folds in high-grade rocks interpreted as forming during regional extension included in this paper are from the Grenville Province of Canada, Norwegian

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Section: Origin Of Shallowly Dipping Foliations In Highgrade Gneiss Tmentioning

confidence: 99%

Mechanisms for folding of high-grade rocks in extensional tectonic settings

Harris

Koyi

Fossen

2002

Earth-Science Reviews

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“…Although it is now widely agreed that core complexes are mainly the product of large-magnitude extension, exactly how core complexes form and evolve over time remains controversial. Perhaps the most contentious features of core complexes are the low-angle normal (detachment) faults that are thought to play a central role in their exhumation [e.g., Coney, 1980]. Many workers have suggested that these faults initiated and slipped at low angles and accumulated tens of km of slip at very high rates [e.g., Reynolds and Spencer, 1985;Davis et al, 1986;John, 1987;Scott and Lister, 1992;Wernicke, 1981Wernicke, , 1985.…”

Section: Introductionmentioning

confidence: 99%

“…[2] In the nearly 4 decades since the recognition of metamorphic core complexes as the product of extensional tectonism, these enigmatic features have played a prominent role in our understanding of both how the crust mechanically extends [e.g., Lister and Davis, 1989;Wernicke, 1992;Axen, 2007] as well as how the North American Cordillera has evolved during the Cenozoic as a whole [e.g., Coney, 1980;Burchfiel et al, 1992]. Although it is now widely agreed that core complexes are mainly the product of large-magnitude extension, exactly how core complexes form and evolve over time remains controversial.…”

Section: Introductionmentioning

confidence: 99%

“…[3] The Sierra Mazatán core complex, located $60 km east of Hermosillo in the state of Sonora, Mexico, is the southernmost core complex in the North American Cordillera [Coney, 1980] (Figure 1). This core complex was exhumed during the Tertiary by a major normal fault that presently dips 10 -15°WSW [Anderson et al, 1980;Nourse et al, 1994].…”

Section: Introductionmentioning

confidence: 99%

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Geologic, structural, and thermochronologic constraints on the tectonic evolution of the Sierra Mazatán core complex, Sonora, Mexico: New insights into metamorphic core complex formation

Wong

Gans

2008

Tectonics

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The Sierra Mazatán in northwestern Mexico is the southernmost metamorphic core complex in the North American Cordillera. Large‐magnitude Tertiary extension at Sierra Mazatán involved both ductile and brittle slip along a major normal fault that presently dips 10°–15° west. Extension was polyphase and involved an early period of extension from 25 to 23 Ma followed by major slip from 21 to 16 Ma. Total slip was ≤20 km and occurred at rates of 3–4 mm/a. This extension predated the plate boundary change to transtension at ∼12 Ma and was largely decoupled from relative Pacific–North American plate motion. Numerous lines of evidence suggest that the presently low‐angle normal fault initiated at a steep dip (50°–60°) and was rotated to lower angles during slip. When corrected for this tilting, fault corrugations at Sierra Mazatán had a similar geometry to the segmentation of many active normal faults, which is compatible with their origin as primary fault features. Many aspects of the Sierra Mazatán are comparable to large active normal faults, indicating that this core complex formed owing to prolonged extension on an otherwise typical high‐angle normal fault. Therefore, core complexes need not represent a fundamentally unique mode of crustal extension.

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“…Within El Jaralito batholith, Laramide magmatism is represented by dioritic to granitic plutons, including two-mica peraluminous granites, that range in age from ~70 to ~50 Ma (González-León et al, 2011), whereas in its flanks there are Oligocene-Miocene metamorphic core complexes of Sierra Mazatán, Sierra El Jaralito and Sierra Aconchi (Coney, 1980;Anderson et al, 1980;Nourse et al, 1994; Vega-Granillo Figure 1. Digital elevation map (taken from GeoMapApp at www.geomapapp.…”

Section: Introductionmentioning

confidence: 99%

Laramide to Miocene syn-extensional plutonism in the Puerta del Sol area, central Sonora, Mexico

González-Becuar¹,

Pérez-Segura²,

Vega-Granillo³

et al. 2017

revmexcg

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González-Becuar, E., Pérez-Segura, E., Vega-Granillo, R., Solari, L., González-León, C.M., Solé, J., López Martínez, M., 2017, Laramide to Miocene syn-extensional plutonism in the Puerta del Sol area, central Sonora, Mexico: Revista Mexicana de Ciencias Geológicas, v. 34, núm. 1, p. 45-61. ABSTRACTPlutonic rocks of the Puerta del Sol area, in central Sonora, represent the extension to the south of the El Jaralito batholith, and are part of the footwall of the Sierra Mazatán metamorphic core complex, whose low-angle detachment fault bounds the outcrops of plutonic rocks to the west. Plutons in the area record the magmatic evolution of the Laramide arc and the Oligo-Miocene syn-extensional plutonism in Sonora. The basement of the area is composed by the ca. 1.68 Ga El Palofierral orthogneiss that is part of the Caborca block. The Laramide plutons include the El Gato diorite (71.29 ± 0.45 Ma, U-Pb), the El Pajarito granite (67.9 ± 0.43 Ma, U-Pb), and the Puerta del Sol granodiorite (49.1 ± 0.46 Ma, U-Pb). The younger El Oquimonis granite (41.78 ± 0.32 Ma, U-Pb) is considered part of the scarce magmatism that in Sonora records a transition to the Sierra Madre Occidental magmatic event. The syn-extensional plutons are the El Garambullo gabbro (19.83 ± 0.18 Ma, U-Pb) and the Las Mayitas granodiorite (19.2 ± 1.2 Ma, K-Ar). A migmatitic event that affected the El Palofierral orthogneiss, El Gato diorite, and El Pajarito granite between ca. 68 and 59 Ma might be related to the emplacement of the El Pajarito granite. The plutons are metaluminous to slightly peraluminous, with the exception of El Oquimonis granite, which is a peraluminous twomica, garnet-bearing granite. They are mostly high-K calc-alkaline with nearly uniform chondrite-normalized REE and primitivemantle normalized multielemental patterns that are characteristic of continental margin arcs and resemble patterns reported for other Laramide granites of Sonora. The Laramide and syn-extensional plutons also have Sr, Nd and Pb isotopic ratios that plot within the fields reported for Laramide granites emplaced in the Caborca terrane in northwestern and central Sonora. Nevertheless, and despite their geochemical affinity to continental magmatic arcs, the El Garambullo gabbro and Las Mayitas granodiorite are syn-extensional plutons that were emplaced at ca. 20 Ma during development of the Sierra Mazatán metamorphic core complex. The 40 Ar/ 39 Ar and K-Ar ages obtained for the El Palofierral orthogneiss, the Puerta del Sol granodiorite, the El Oquimonis granite, and the El Garambullo gabbro range from 26.3 ± 0.6 to 17.4 ± 1.0 Ma and are considered cooling ages associated with the exhumation of the metamorphic core complex.Key words: Laramide magmatism; syn-extensional plutonism; geochronology; geochemistry; Sr-Nd-Pb isotopes; Sonora; Mexico. Gato (71.29 ± 0.45 Ma, el granito El Pajarito (67.9 ± 0.43 Ma, RESUMEN

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Cordilleran metamorphic core complexes: An overview

Cited by 383 publications

References 38 publications

Mechanisms for folding of high-grade rocks in extensional tectonic settings

Mechanisms for folding of high-grade rocks in extensional tectonic settings

Geologic, structural, and thermochronologic constraints on the tectonic evolution of the Sierra Mazatán core complex, Sonora, Mexico: New insights into metamorphic core complex formation

Laramide to Miocene syn-extensional plutonism in the Puerta del Sol area, central Sonora, Mexico

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