Grenville orogeny


The Grenville orogeny was a long-lived Mesoproterozoic mountain-building event associated with the assembly of the supercontinent Rodinia Its record is a prominent orogenic belt which spans a significant portion of the North American continent, from Labrador to Mexico, as well as to Scotland

Grenville orogenic crust of mid-late Mesoproterozoic age circa 1250–980 Ma is found worldwide, but generally, only events which occurred on the southern and eastern margins of Laurentia are recognized under the “Grenville” name1

These orogenic events are also known as the Kibaran orogeny in Africa and the Dalslandian orogeny in Western Europe

Extent orange regions of the Grenville orogeny, after Tollo et al 2004 and Darabi 2004

Contents

  • 1 Timescale
  • 2 General tectonics
  • 3 General lithology
  • 4 Regional variations
    • 41 Texas and Mexico
    • 42 Appalachians
    • 43 Adirondacks
    • 44 Grenville province
  • 5 See also
  • 6 References
  • 7 External links

Timescaleedit

The problem of timing the Grenville orogeny is an area of some contention today The timescale outlined in Toby Rivers’ recent work2 is derived from the well-preserved Grenville Province, and represents one of the most detailed records of the orogeny This classification considers the classical Grenville designation to cover two separate orogenic cycles; the Rigolet, Ottawan and Shawingian orogenies compose the Grenville Cycle, and the Elzevirian orogeny stands on its own Due to the great size of the area affected by Grenville events, there is some variance in timing across the orogenic belt1 Regional variations below discusses local deviations from Rivers’ timeline, presented here

Timeline of the Grenville orogeny, after Rivers 2002

Ages are approximated from the magmatic activity associated with the individual cycles of the orogeny The gaps in the ages of the compression cycles and isotope analysis of hornblende, biotite, and potassium feldspar suggest that extension was occurring when compression had momentarily ceased34

Rivers' 2008 paper has now examined the timing of the different periods of the orogeny and reconstructed the timeline based on the spatial and temporal metamorphism of the rocks present According to this newer version of the timeline which is a composite of Rivers 1997 and Gower and Krogh 2002, the Elzevirian orogeny occurs from 1240 to 1220 Ma, the Shawinigan occurs from 1190 to 1140 Ma and is no longer part of the Grenville cycle, the Ottawan now 1090–1020 Ma and Rigolet still 1010–980 Ma become phases which are grouped into the Grenvillian orogeny5

General tectonicsedit

Reconstruction of the events of the orogeny is ongoing, but the generally accepted view is that the eastern and southern margins of Laurentia were active convergent margins until the beginning of continental collision This type of subduction B-type tends to emplace magmatic arcs on or near the edge of the overriding plate in modern subduction zones, and evidence of contemporary ca 1300–1200 Ma island arcs can be found throughout the Grenville orogen The Andes of South America are considered a modern analogue1 From about ca 1190–980 Ma the actual timing varies by locality two separate continental blocks collided with Laurentia Both of these collision events are thought to be analogous to the collision driving modern-day growth of the Himalaya range16 For some time one of the blocks was believed to be the continent of Amazonia, but paleomagnetic evidence has now proven that this is not the case7

These periods of thrusting and metamorphism were not continuous, but rather interrupted by comparatively quiet periods, during which AMCG anorthosite/ mangerite/ charnockite/ granite plutons were intruded into the country rock1 Polarities of subduction which plate overrode which vary by region and time Some island arc remnants were emplaced on the Laurentian margin, and some were accreted during orogeny89 Timing of these events is constrained by cross-cutting relations observed in the field as well as SHRIMP sensitive high-resolution ion microprobe and TIMS thermal ionization mass spectrometry uranium- lead dating10

The first period of tectonic activity was the accretion of an island arc at some point during the Elzevirian Orogeny7 Before the accretion of the island arc took place, subduction between a continental plate and presumably an oceanic plate was taking place Slab pull and far-field drivers such as ridge push were aiding in closing the distance between the island arc and the continent Depending on the angle of subduction deformation of the continental crust was already taking place and thickening the lithosphere By 119 Ga the Elzevir back arc basin was closing3

From 118 to 114 Ga extension was occurring in the area3 Whether due to lithospheric cooling, also known as thermal subsidence, or the compressional activity in the area reactivated some extensional faults The extension is marked by the isotopic ages of the previously mentioned rocks Additionally there is the formation of sedimentary basins which means the margin was quiescent enough that sediments could accumulate However, in some areas from 116 to 113 Ga, coeval with extension, there is evidence there was still thrusting and emplacement of terranes occurring3

According to one model westward thrusting occurred from 112 to 109 Ga and then extension was the primary tectonic activity until 105 Ga3 It was at this point that the Central Granulite Terrane was exhumed and minor magmatism occurred7

The precise reason for change from compression to extension is unknown but may be the result of gravitational collapse, mantle delamination, the formation of a plume underneath a supercontinent, changes in far-field drivers on the distribution of stress, or any combination of reasons originating from the fact that our planet is dynamic7 The cyclic compression and extension history of this area is similar to the Wilson Cycle In this area of the world the Wilson Cycle would be creating the basin for the proto-Atlantic Ocean Iapetus Ocean

General lithologyedit

Today, the Grenville orogen is marked by northwest verging fold-and-thrust belts and high pressure metamorphic regimes, as well as distinctive AMCG suite magmatism Metamorphism is commonly of amphibolite and granulite facies, that is, medium to high temperature and pressure alteration Eclogitized metagabbros very high pressure ultramafic metamorphic rocks are found in some localities, and likely represent areas of deepest burial and/or most intense collision11 Throughout the orogen, these sequences of high pressure metamorphic rocks are cut by intrusive AMCG suite plutons, generally interpreted as syn- or post-tectonic AMCG plutonism is generally associated with asthenospheric upwelling under thinned lithosphere112 This is derived from the theory that AMCG plutonism is driven by ponding of olivine tholeiite basalt at the base of the continental crust during tectonic extension3 The lithosphere may be thinned either convectively or by delamination, in which the bottom portion of the lithosphere is stripped off Both models have been proposed for the Grenville orogeny3

The Grenville orogeny can be categorized into three sections based on structure, lithology, and thermochronology The three sections, respectively called the Gneiss Belt, Metasedimentary Belt, and the Granulite terrane are all separated by shear zones47

The Gneiss Belt is made up of felsic gneisses and amphibolites that were metamorphosed in the upper amphibolite to granulite facies Thrusting in this section was low angle, but would have the potential to increase and rotate as it continued and evolved Shear in this area is referred to as ductile shear meaning the material was cooling and becoming solid, but still behaving viscously or plasticly

The age of this belt is approximately 18 to 118 Ga Regional metamorphism is believed to have deformed this area at approximately 14 Ga and metamorphic thrusting at approximately 116 to 112 Ga47

The Metasedimentary Belt is predominantly sedimentary and volcanic rocks which have undergone greenschist to granulite facies metamorphism Subdivisions of this belt include the Bancroft, Elzevir, Sharbot Lake, and Frontenac Domains and the Adirondack Lowlands In this belt magmatism is known to have occurred between 142 and 104 Ga depending on location As with the Gneiss Belt, metamorphism is believed to have occurred at approximately 116 Ga47

The Granulite Terrane is composed of meta-igneous gneisses including anorthosite massifs Anorthosites form in plutons and are composed mostly of plagioclase The rocks of the Grenville Province in Canada are included in this category The oldest magmatism known in this area dates to 132 Ga approximately Granulite facies metamorphism began around 115 Ga and continued for about 150 Ma after the onset, however the continuity of the metamorphism cannot be determined47

Regional variationsedit

See also: Sveconorwegian orogeny Proposed reconstruction of Rodinia for 750 Ma, with orogenic belts of 11 Ga age highlighted in green13 Red dots indicate 13–15 Ga A-type granites

It is important to separate local from large-scale tectonic history of the orogenic belt in order to understand the orogeny For this purpose, the Grenville orogen is generally broken into four localities: the southern extent in Texas and Mexico, the Appalachians, the Adirondacks and the well-studied Grenville Province of Canada A portion of the orogen can be found in Scotland, but due to Scotland’s proximity to the Grenville province prior to opening of the Iapetus Ocean modern day Atlantic Ocean, the two share largely the same history114

Texas and Mexicoedit

Texas and Mexico represent the southern margin of Laurentia, and likely collided with a different continent than that involved in the eastern collision6 The Zapotecan Orogeny of Mexico is coeval with the later stages of the Grenville orogeny, and they are generally considered to be one and the same15 Mesoproterozoic igneous protoliths metamorphosed to granulite facies during the orogeny fall into two age groups in Mexico; ca 1235–1115 Ma and ca 1035–1010 Ma Rocks of the former group bear geochemical signatures implying island arc and back-arc basin provenance The latter group represents AMCG magmatism These AMCG rocks are somewhat anomalous throughout the Grenville orogen, there is no known orogenic event which immediately predates their emplacement15 It is suggested that the regime of subduction under the Laurentian margin currently in Texas, north of the accreted Mexican terrane ended around 1230 Ma, and that subduction polarity reversed to bring the colliding continent north, since the Llano uplift, which records the history of the Grenville in Texas, bears no evidence of arc magmatism after this time9

Appalachiansedit

The Appalachian Mountains contain small, isolated exposures of the Grenville orogen The largest of these, the Long Range Inlier, comprises the Long Range Mountains of Newfoundland Other exposures include the Shenandoah and French Broad massifs, which comprise the Blue Ridge province of Virginia Blue Ridge rocks consist of various gneisses of upper amphibolite and granulite facies, intruded by charnockites and granitoid rocks These igneous rocks were intruded in three intervals: ca 1160–1140  Ma, ca 1112 Ma, and ca 1080–1050 Ma, and are massive to weakly foliated in texture1

Adirondacksedit

This region consists of a massive dome of Proterozoic rock on the New York-Canada border Both the Elzevirian ca 1250–1190 Ma and Ottawan ca 1080–1020 Ma orogenic pulses are recorded in the Adirondacks, producing high-grade metamorphic rock A northwest-trending high-strain shear zone separates the dome into the Highlands to the southeast and the Lowlands to the northwest It is believed716 that the shear zone the Carthage-Colton was a transpressional boundary during the Ottawan, when the Highlands were thrust over the Lowlands1

Grenville provinceedit

The Grenville province is named for the village of Grenville in Quebec, and constitutes the youngest portion of the Canadian Shield Since the area has not undergone any regional metamorphic overprinting since the orogeny, it is considered an ideal study area for Grenville and pre-Grenville age tectonics Hence, most of what is known about the orogeny and its processes is derived from the Grenville Province1

See alsoedit

  • Adirondack Mountains in New York State
  • Blue Ridge Mountains in Appalachia
  • Laurentian Mountains in Quebec
  • Llano Uplift in Central Texas
  • Supercontinent cycle

Referencesedit

  1. ^ a b c d e f g h i j Tollo, Richard P; Louise Corriveau; James McLelland; Mervin J Bartholomew 2004 "Proterozoic tectonic evolution of the Grenville orogen in North America: An introduction" In Tollo, Richard P; Corriveau, Louise; McLelland, James; et al Proterozoic tectonic evolution of the Grenville orogen in North America Geological Society of America Memoir 197 :Boulder, CO pp 1–18 ISBN 978-0-8137-1197-3 
  2. ^ Rivers, T; et al 2002 "The High Pressure belt in the Grenville Province: Architecture, timing, and exhumation" Canadian Journal of Earth Sciences 39 5: 867–893 Bibcode:2002CaJES39867R doi:101139/e02-025 
  3. ^ a b c d e f g Corrigan, D; Hanmer, S 1997 "Anorthosites and related granitoids in the Grenville orogen: A product of convective thinning of the lithosphere" Geology 25: 61–64 Bibcode:1997Geo2561C doi:101130/0091-76131997025<0061:AARGIT>23CO;2 
  4. ^ a b c d e DeWolf, C; Mezger, K 1994 "Lead isotope analysis of leached feldspars: Constraints on the early crustal history of the Grenville Orogen" Geochimica et Cosmochimica Acta 58 24: 5537–5550 Bibcode:1994GeCoA585537D doi:101016/0016-70379490248-8 hdl:202742/31183 
  5. ^ Rivers, T; et al 2008 "Assembly and Preservation of lower, mid, and upper orogenic crust in the Grenville Province-Implications for the evolution of large hot long-duration orogens" Precambrian Research 167 3–4: 237–259 doi:101016/jprecamres200808005 
  6. ^ a b Mosher, Sharon; April M Hoh; Jostin A Zumbro; Joseph F Reese 2004 "Tectonic evolution of the eastern Llano Uplift, central Texas: A record of Grenville orogenesis along the southern Laurentian margin" In Tollo, Richard P; Corriveau, Louise; McLelland, James; et al Proterozoic tectonic evolution of the Grenville orogen in North America Geological Society of America Memoir 197 :Boulder, CO pp 783–798 ISBN 978-0-8137-1197-3 
  7. ^ a b c d e f g h i Margaret MStreepey, Carolina Lithgow-Bertelloni, Ben A van der Pluijm, Eric J Essene, and Jerry F Magloughlin 2004 "Exhumation of a collisional orogen: a perspective from the North American Grenville Province" In Tollo, Richard P; Corriveau, Louise; McLelland, James; et al Proterozoic tectonic evolution of the Grenville orogen in North America PDF Geological Society of America Memoir 197 :Boulder, CO pp 391–410 ISBN 978-0-8137-1197-3 CS1 maint: Uses authors parameter link
  8. ^ Corriveau, Louise 1990 "Proterozoic subduction and terrane amalgamation in the southwestern Grenville province, Canada: Evidence from ultrapotassic to shoshonitic plutonism" Geology 14 7: 614–617 Bibcode:1990Geo18614C doi:101130/0091-76131990018<0614:PSATAI>23CO;2 
  9. ^ a b Mosher, S; et al 2008 "Mesoproterozoic plate tectonics: A collisional model for the Grenville-aged orogenic belt in the Llano uplift, central Texas" Geology 36: 55–58 doi:101130/G24049A1 
  10. ^ Tollo, Richard P; John N Aleinikoff; Elizabeth A Borduas; Paul C Hackley; C Mark Fanning 2004 "Petrologic and geochronologic evolution of the Grenville orogen, northern Blue Ridge province, Virginia" In Tollo, Richard P; Corriveau, Louise; McLelland, James; et al Proterozoic tectonic evolution of the Grenville orogen in North America Geological Society of America Memoir 197 :Boulder, CO pp 647–677 ISBN 978-0-8137-1197-3 
  11. ^ Indares, Aphrodite; Rivers, Toby February 1995 "Textures, metamorphic reactions and thermobarometry of eclogitized metagabbros: a Proterozoic example" European Journal of Mineralogy 7 1: 43–56 doi:101127/ejm/7/1/0043 ISSN 0935-1221 
  12. ^ Emslie, R F 1978 "Anorthosite massifs, rapakivi granites, and Late Proterozoic rifting of North America" Precambrian Research 7: 61–98 doi:101016/0301-92687890005-0 
  13. ^ "Research paper suggests East Antarctica and North America once linked" The Antarctic Sun United States Antarctic Program 26 August 2011 Retrieved 15 November 2012 
  14. ^ Darabi, M H; Piper, J D A 2004 "Palaeomagnetism of the Late Mesoproterozoic Stoer Group, northwest Scotland: implications for diagenesis, age and relationship to the Grenville Orogeny" Geology Magazine 141: 15–39 doi:101017/S0016756803008148 
  15. ^ a b Cameron, Kenneth L; Robert Lopez; Fernando Ortega-Gutiérrez; Luigi A Solari; J Duncan Keppie; Carlos Schulze 2004 "U-Pb geochronology and Pb isotopic compositions of leached feldspars: Constraints on the origin and evolution of Grenville rocks from eastern and southern Mexico" In Tollo, Richard P; Corriveau, Louise; McLelland, James; et al Proterozoic tectonic evolution of the Grenville orogen in North America Geological Society of America Memoir 197 :Boulder, CO pp 755–769 ISBN 978-0-8137-1197-3 
  16. ^ Johnson, Eric L; Eric T Goergen; Benjamin L Fruchey 2004 Tollo, Richard P; Corriveau, Louise; McLelland, James; et al, eds "Right lateral oblique slip movements followed by post-Ottawan 1050-1020 Ma orogenic collapse along the Carthage-Colton shear zone: Data from the Dana Hill metagabbro body, Adirondack Mountains, New York" Proterozoic tectonic evolution of the Grenville orogen in North America Geological Society of America Memoir Boulder, CO 197: 357–378 ISBN 978-0-8137-1197-3 

External linksedit

  • The Grenville
  • "Prospective Metallogenic Settings of the Grenville Province" Geological Survey of Canada 
  • The Crustal Structure of The Grenville Front
  • Himalia-type syntaxis in the Grenville orogen
  • Tectonic evolution of the southern Laurentian Grenville orogen
  • THE FIRST SUPERCONTINENT
  • Metamorphaism of the Grenville Orogeny


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