Journal articles: 'Proterozoic crustal growth'

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McCulloch, M. T., L. P. Black, and R. W. Page. "Proterozoic crustal growth: Underplating and magmatism." Chemical Geology 70, no. 1-2 (August 1988): 71. http://dx.doi.org/10.1016/0009-2541(88)90396-8.

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Hall, Jeremy, Keith E. Louden, Thomas Funck, and Sharon Deemer. "Geophysical characteristics of the continental crust along the Lithoprobe Eastern Canadian Shield Onshore–Offshore Transect (ECSOOT): a review." Canadian Journal of Earth Sciences 39, no. 5 (May 1, 2002): 569–87. http://dx.doi.org/10.1139/e02-005.

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The Eastern Canadian Shield OnshoreOffshore Transect (ECSOOT) of the Lithoprobe program included 1200 km of normal-incidence seismic profiles and seven wide-angle seismic profiles across Archean and Proterozoic rocks of Labrador, northern Quebec, and the surrounding marine areas. Archean crust is 3344 km thick. P-wave velocity increases downwards from 6.0 to 6.9 km/s. There is moderate crustal reflectivity, but the reflection Moho is unclear. Archean crust that stabilized in the Proterozoic is similar except for greater reflectivity and a well-defined Moho. Proterozoic crust has similar or greater thickness, variable lower crustal velocities, and strong crustal reflectivity. Geodynamic processes of Paleoproterozoic growth of the Canadian Shield are similar to those observed in modern collisional orogens. The suturing of the Archean Core Zone and Superior provinces involved whole-crustal shearing (top to west) in the Core Zone, linked to thin-skinned deformation in the New Quebec Orogen. The Torngat Orogen sutures the Nain Province to the Core Zone and reveals a crustal root, in which Moho descends to 55 km. It formed by transpression and survived because of the lack of postorogenic heating. Accretion of the Makkovik Province to the Nain Province involves delamination at the Moho and distributed strain in the juvenile arcs. Delamination within the lower crust characterizes the accretion of Labradorian crust in the southeastern Grenville Province. Thinning of the crust northwards across the Grenville Front is accentuated by Mesozoic extension that reactivates Proterozoic shear zones. The intrusion of the Mesoproterozoic Nain Plutonic Suite is attributed to a mantle plume ponding at the base of the crust.

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Ross, Gerald M., and David W. Eaton. "Proterozoic tectonic accretion and growth of western Laurentia: results from Lithoprobe studies in northern Alberta." Canadian Journal of Earth Sciences 39, no. 3 (March 1, 2002): 313–29. http://dx.doi.org/10.1139/e01-081.

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The western Canadian Shield of northern Alberta is composed of a series of continental slivers that were accreted to the margin of the Archean Rae hinterland ca. 1.92.0 Ga., preserving a unique record of continental evolution for the interval 2.12.3 Ga. This part of Laurentia owes its preservation to the accretionary style of tectonic assembly south of the Great Slave Lake shear zone, which contrasts with indentationescape processes that dominate the Paleoproterozoic record farther north. The Buffalo Head and Chinchaga domains form the central core of this region, comprising a collage of ca. 23252045 Ma crustal elements formed on an Archean microcontinental edifice, and similar age crust is preserved as basement to the Taltson magmatic zone. The distribution of magmatic ages and inferred collision and subduction zone polarity are used to indicate closure of intervening oceanic basins that led to magmatism and emplacement of continental margin arc and collisional belts that formed from ca. 1998 to1900 Ma. Lithoprobe crustal seismic profiles complement the existing geochronologic and geologic databases for northern Alberta and elucidate the nature of late stages of the accretionary process. Crustal-scale imbrication occurred along shallow eastward-dipping shear zones, resulting in stacking of arc slivers that flanked the western Buffalo Head terrane. The seismic data suggest that strain is concentrated along the margins of these crustal slivers, with sparse evidence for internal penetrative deformation during assembly. Post-collisional mafic magmatism consisted of widespread intrusive sheets, spectacularly imaged as regionally continuous subhorizontal reflections, which are estimated to extend over a region of ca. 120 000 km2. The form of such mid-crustal magmatism, as subhorizontal sheets (versus vertical dykes), is interpreted to represent a style of magma emplacement within a confined block, for which a tectonic free face is unavailable.

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Clowes, R. M., F. A. Cook, A. G. Green, C. E. Keen, J. N. Ludden, J. A. Percival, G. M. Quinlan, and G. F. West. "Lithoprobe: new perspectives on crustal evolution." Canadian Journal of Earth Sciences 29, no. 9 (September 1, 1992): 1813–64. http://dx.doi.org/10.1139/e92-145.

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Lithoprobe is Canada's national, collaborative, multidisciplinary earth science research program directed toward an enhanced understanding of how the North American continent evolved. Research in its eight transects or study areas, which span the country from Vancouver Island to Newfoundland and geological time from 4 Ga to the present, is spearheaded by seismic reflection surveys. These, combined with many other studies, are providing new insight into the varied tectonic processes that have been active in forming the continent. Results from the Southern Cordillera transect show that Mesozoic crustal growth occurred in the central and eastern Cordillera by the accretion and amalgamation of exotic terranes, the collision of which resulted in the generation of crustal-scale antiforms and duplexes. After the principal periods of compression, this area was affected by a major episode of extension that led to the unroofing of the metamorphic core complexes. Farther to the west, past and present subduction processes have eroded the lower lithosphere of accreted terranes and left underplated sediments and oceanic lithosphere. The Lithoprobe East transect, covering the Paleozoic Newfoundland Appalachians and Mesozoic rifted Atlantic margin, reveals three lower crustal blocks, each with distinctive reflection signatures on marine seismic data. Structures of the geologically established tectono-stratigraphic domains, imaged clearly by new onshore reflection data, sole at upper crustal to mid-crustal levels, suggesting that much of the surface stratigraphy is allochthonous to the lower crustal blocks. At the ocean–continent transition, interpretations suggest underplating of thinned continental crust by basaltic melt during the rifting process.In Lake Superior, data from the Great Lakes International Multidisciplinary Program on Crustal Evolution (GLIMPCE) transect reveal the complex structures of the late Middle Proterozoic Keweenawan rift, which is up to 35 km deep, that almost split North America. The GLIMPCE data in Lake Huron show a spectacular series of east-dipping crustal-scale reflections that coincide with the Grenville front tectonic zone. These and other data have led to a two-stage model involving collision of an exotic terrane with the southern Superior cratonic margin in the late Early Proterozoic followed by stacking–crustal penetrating imbrication and ramping associated with the Middle Proterozoic Grenvillian orogeny. The Archean Kapuskasing structural zone, a prominent northeast-trending feature that cuts obliquely across the dominant east-west structures of the Superior Province, is interpreted as a thin thrust sheet, soled by a variably reflective décollement, above which about 70 km of crustal shortening has occurred to bring mid-crustal to lower crustal rocks to the surface, and below which the Moho deepens. The shortening may have been accomplished by brittle faulting and erosion at levels above 20 km and ductile folding or faulting in the lower crust. Preliminary studies in the Archean Abitibi greenstone belt indicate that two major fault zones, the Larder Lake–Cadillac and Porcupine–Destor, which host significant mineralization, were generated by crustal-scale thrust and (or) strike-slip tectonics. Archean crustal sections are as structurally diverse and complex as their Proterozoic and Phanerozoic counterparts. The reflection Moho has highly variable characteristics as imaged within transects and among different transects. Crustal and Moho reflectivity observed in the various transects is caused by a wide range of features, including fault–shear zones, lithologic contacts, compositional layering, fluids in zones of high porosity, and anisotropy.

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Samson, S. D., and P. J. Patchett. "The Canadian Cordillera as a modern analogue of Proterozoic crustal growth." Australian Journal of Earth Sciences 38, no. 5 (December 1991): 595–611. http://dx.doi.org/10.1080/08120099108727994.

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Åhäll, Karl-Inge, and James N. Connelly. "Long-term convergence along SW fennoscandia: 330m.y. of proterozoic crustal growth." Precambrian Research 161, no. 3-4 (March 10, 2008): 452–74. http://dx.doi.org/10.1016/j.precamres.2007.09.007.

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7

BERHE, SEIFE M. "Ophiolites in Northeast and East Africa: implications for Proterozoic crustal growth." Journal of the Geological Society 147, no. 1 (January 1990): 41–57. http://dx.doi.org/10.1144/gsjgs.147.1.0041.

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8

Chamberlain, Kevin R., Carol D. Frost, and B. Ronald Frost. "Early Archean to Mesoproterozoic evolution of the Wyoming Province: Archean origins to modern lithospheric architecture." Canadian Journal of Earth Sciences 40, no. 10 (October 1, 2003): 1357–74. http://dx.doi.org/10.1139/e03-054.

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Local preservation of 3.63.0 Ga gneisses and widespread isotopic evidence for crust of this age incorporated into younger plutons indicates that the Wyoming Province was a [Formula: see text] 100 000 km2 middle Archean craton, which was modified by late Archean magmatism and tectonism and Proterozoic extension and rifting. On the basis of differences in late Archean histories, the Wyoming Province is subdivided into five subprovinces: three in the Archean core, (1) the Montana metasedimentary province, (2) the Bighorn subprovince, and (3) the Sweetwater subprovince, and two Archean terrains that may be allochthonous to the 3.0 Ga craton, (4) the Sierra Madre Medicine Bow block, and (5) the Black Hills Hartville block. A thick, fast lower crustal layer, imaged by Deep Probe, corresponds geographically with the Bighorn subprovince and may be an underplate associated with ca. 2.70 Ga mafic magmatism. The Sweetwater subprovince is characterized by an eastwest tectonic grain that was established by three or more temporally related, late Archean, pulses of basin development, shortening, and arc magmatism. This tectonic grain, including the 2.62 Ga Oregon Trail structure, controlled the locations and orientations of Proterozoic rifting and Laramide uplifts. The present-day lithospheric architecture of the Wyoming Province is the result of cumulative processes of crustal growth and tectonic modification; lithospheric contrasts have apparently persisted for billions of years. If there has been any net crustal growth of the Wyoming Province since 3.0 Ga, it has involved a combination of mafic underplating and arc magmatism.

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McLaren, Sandra, Mike Sandiford, and Roger Powell. "Contrasting styles of Proterozoic crustal evolution: A hot-plate tectonic model for Australian terranes." Geology 33, no. 8 (August 1, 2005): 673–76. http://dx.doi.org/10.1130/g21544ar.1.

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Abstract Proterozoic terranes in Australia record complex tectonic histories in the interval 1900– 1400 Ma that have previously been interpreted by means of simple intracratonic or plate-tectonic models. However, these models do not fully account for (1) repeated tectonic reactivation (both orogenesis and rifting), (2) mainly high-temperature–low-pressure metamorphism, (3) rifting and sag creating thick sedimentary basins, (4) the nature and timing of voluminous felsic magmatism, (5) relatively large aspect ratio orogenic belts, and (6) a general paucity of diagnostic plate-boundary features. A key to understanding these histories is the observation that Australian Proterozoic terranes are characterized by an extraordinary, but heterogeneous, enrichment of the heat-producing elements. This enrichment must contribute to long-term lithospheric weakening, and thus we advocate a hybrid lithospheric evolution model with two tectonic switches: plate-boundary–derived stresses and heat-producing-element–related lithospheric weakening. The Australian Proterozoic crustal growth record is therefore a function of the magnitude of these stresses, the way in which the heat-producing elements are distributed, and how both of these change with time.

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DOWNES, H., P. PELTONEN, I. MÄNTTÄRI, and E. V. SHARKOV. "Proterozoic zircon ages from lower crustal granulite xenoliths, Kola Peninsula, Russia: evidence for crustal growth and reworking." Journal of the Geological Society 159, no. 5 (September 2002): 485–88. http://dx.doi.org/10.1144/0016-764901-162.

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11

McLelland, James M. "Crustal growth associated with anorogenic, mid-Proterozoic anorthosite massifs in northeastern North America." Tectonophysics 161, no. 3-4 (April 1989): 331–41. http://dx.doi.org/10.1016/0040-1951(89)90163-7.

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12

Goodge, John W. "Crustal heat production and estimate of terrestrial heat flow in central East Antarctica, with implications for thermal input to the East Antarctic ice sheet." Cryosphere 12, no. 2 (February 8, 2018): 491–504. http://dx.doi.org/10.5194/tc-12-491-2018.

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Abstract. Terrestrial heat flow is a critical first-order factor governing the thermal condition and, therefore, mechanical stability of Antarctic ice sheets, yet heat flow across Antarctica is poorly known. Previous estimates of terrestrial heat flow in East Antarctica come from inversion of seismic and magnetic geophysical data, by modeling temperature profiles in ice boreholes, and by calculation from heat production values reported for exposed bedrock. Although accurate estimates of surface heat flow are important as an input parameter for ice-sheet growth and stability models, there are no direct measurements of terrestrial heat flow in East Antarctica coupled to either subglacial sediment or bedrock. As has been done with bedrock exposed along coastal margins and in rare inland outcrops, valuable estimates of heat flow in central East Antarctica can be extrapolated from heat production determined by the geochemical composition of glacial rock clasts eroded from the continental interior. In this study, U, Th, and K concentrations in a suite of Proterozoic (1.2–2.0 Ga) granitoids sourced within the Byrd and Nimrod glacial drainages of central East Antarctica indicate average upper crustal heat production (Ho) of about 2.6 ± 1.9 µW m−3. Assuming typical mantle and lower crustal heat flux for stable continental shields, and a length scale for the distribution of heat production in the upper crust, the heat production values determined for individual samples yield estimates of surface heat flow (qo) ranging from 33 to 84 mW m−2 and an average of 48.0 ± 13.6 mW m−2. Estimates of heat production obtained for this suite of glacially sourced granitoids therefore indicate that the interior of the East Antarctic ice sheet is underlain in part by Proterozoic continental lithosphere with an average surface heat flow, providing constraints on both geodynamic history and ice-sheet stability. The ages and geothermal characteristics of the granites indicate that crust in central East Antarctica resembles that in the Proterozoic Arunta and Tennant Creek inliers of Australia but is dissimilar to other areas like the Central Australian Heat Flow Province that are characterized by anomalously high heat flow. Age variation within the sample suite indicates that central East Antarctic lithosphere is heterogeneous, yet the average heat production and heat flow of four age subgroups cluster around the group mean, indicating minor variation in the thermal contribution to the overlying ice sheet from upper crustal heat production. Despite these minor differences, ice-sheet models may favor a geologically realistic input of crustal heat flow represented by the distribution of ages and geothermal characteristics found in these glacial clasts.

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Dia, Aline, Bernard Dupré, Clément Gariépy, and Claude J. Allègre. "Sm–Nd and trace-element characterization of shales from the Abitibi Belt, Labrador Trough, and Appalachian Belt: consequences for crustal evolution through time." Canadian Journal of Earth Sciences 27, no. 6 (June 1, 1990): 758–66. http://dx.doi.org/10.1139/e90-077.

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Nd-isotopic compositions and Sm, Nd, Li, K, Rb, Sr, Ba, Ni, and Cr abundances are reported for 25 shale samples from the Canadian Shield (late Archean Abitibi greenstone belt and the mid-Proterozoic Labrador Trough) and from the Quebec Appalachians (lower Paleozoic Humber Zone). The chemical and isotopic characteristics of the samples are used to monitor the rate of generation and the compositional evolution of continental crust through time. The Nd crustal-residence ages record preferential time of continental growth around 2.7 and 1.7 Ga. The Nd model ages of the Appalachian shales do not record evidence for the formation of large crustal volumes through mantle extraction since 1.3 Ga. Consequently, crustal recycling was the dominant process taking place at their source areas in the Grenville Province.The trace-element distributions of shales show systematic trends as a function of time: Li, K, Ba, Sm, and Nd contents regularly increase in the post-Archean record; in comparison, the Cr and Ni contents reached a maximum towards the end of the Archean and regularly decreased thereafter. These observations could reflect two classes of processes: (a) the development of infracrustal K-rich granitoid magmatism at the expense of mantle-derived Na-rich magmatism, which dominated the Archean period; or (b) differential erosion effects, which reduced the sampling of the old, smooth crustal parts in comparison to the younger, recycled segments. In the latter case, (b), shale formation involved components whose nature and respective proportion changed after Archean time.

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Ibanez-Mejia, Mauricio, Alex Pullen, Jesse Arenstein, George E. Gehrels, John Valley, Mihai N. Ducea, Andres R. Mora, Mark Pecha, and Joaquin Ruiz. "Unraveling crustal growth and reworking processes in complex zircons from orogenic lower-crust: The Proterozoic Putumayo Orogen of Amazonia." Precambrian Research 267 (September 2015): 285–310. http://dx.doi.org/10.1016/j.precamres.2015.06.014.

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Cavosie, Aaron, and Jane Selverstone. "Early Proterozoic oceanic crust in the northern Colorado Front Range: Implications for crustal growth and initiation of basement faults." Tectonics 22, no. 2 (April 2003): n/a. http://dx.doi.org/10.1029/2001tc001325.

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Miller, Calvin F., John M. Hanchar, Joseph L. Wooden, Victoria C. Bennett, T. Mark Harrison, David A. Wark, and David A. Foster. "Source region of a granite batholith: evidence from lower crustal xenoliths and inherited accessory minerals." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 83, no. 1-2 (1992): 49–62. http://dx.doi.org/10.1017/s0263593300007744.

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ABSTRACTLike many granites, the Late Cretaceous intrusives of the eastern Mojave Desert, California, have heretofore provided useful but poorly focused images of their source regions. New studies of lower crustal xenoliths and inherited accessory minerals are sharpening these images.Xenoliths in Tertiary dykes in this region are the residues of an extensive partial melting event. Great diversity in their composition reflects initial heterogeneity (both igneous and sedimentary protoliths) and varying amounts of melt extraction (from <10% to >70%). Mineral assemblages and thermobarometry suggest that the melting event occurred at T ≥ 750°C at a depth of about 40 km. Present-day Sr, Nd, and Pb isotopic ratios indicate a Mojave Proterozoic heritage, but unrealistic model ages demonstrate the late Phanerozoic adjustment of parent/daughter ratios. A link between these xenoliths and the Late Cretaceous granites, though not fully documented, is probable; in any case, they provide invaluable clues concerning a crustal melting event, recording information about nature of source material (heterogeneous, supracrustal-rich), conditions of melting (moderately deep, moderately high T, accompanied by partial dehydration), and melt extraction (highly variable, locally extensive).The Old Woman-Piute granites contain a large fraction of inherited zircon and monazite. A SHRIMP ion probe investigation shows that these zircons record a Proterozoic history similar to that which affected the Mojave region. Zonation patterns in zircons, and to a lesser extent monazites and xenotimes, document multiple phases of igneous, metamorphic, and sedimentary growth and degradation, commonly several in a single grain. Low Y in portions of the cores of inherited zircons and monazites and in monazites and outer portions of zircons from the xenoliths appear to indicate growth in equilibrium with abundant garnet.

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SANTOS, EDILTON J., and VLADIMIR C. MEDEIROS. "CONSTRAINTS FROM GRANITIC PLUTONISM ON PROTEROZOIC CRUSTAL GROWTH OF THE TRANSVERSE ZONE, BORBOREMA PROVINCE, NE BRAZIL." Revista Brasileira de Geociências 29, no. 1 (March 1, 1999): 73–84. http://dx.doi.org/10.25249/0375-7536.1999297384.

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18

Martin, C., and A. P. Dickin. "Styles of Proterozoic crustal growth on the southeast margin of Laurentia: evidence from the central Grenville Province northwest of Lac St.-Jean, Quebec." Canadian Journal of Earth Sciences 42, no. 10 (October 1, 2005): 1643–52. http://dx.doi.org/10.1139/e05-052.

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The southeast margin of Laurentia was a very long lived active continental margin, part of whose history is recorded in the Grenville Province of the Canadian Shield. Within this province, Nd-isotope mapping can be used to define the boundaries between terranes with a variety of crustal formation ages and can also distinguish between crustal growth by oceanic and continental-arc magmatism. The former gives rise to large terranes with homogeneous Nd-isotope signatures and well-defined boundaries, whereas the latter leads to areas with heterogeneous Nd-isotope signatures. One of the best examples of continental-arc magmatism in the Grenville Province is provided by the region northwest of Lac St.-Jean, Quebec. Eighty new Nd-isotope analyses are used (along with aeromagnetic data) to divide this area into three blocks, bounded by abrupt changes in Nd model age. The western block consists almost exclusively of tonalitic grey gneisses with Archean model ages. The eastern block is composed almost exclusively of gneisses with Nd model ages of 1.61.5 Ga and tonalitetrondhjemitegranodiorite-type chemistry. In contrast, the central block has a wide range of Nd-isotope signatures and more alkaline major element chemistry characteristic of an ensialic arc. The εNd values in this block correlate with distance southeast of the Allochthon Boundary Thrust, suggesting that ensialic arc magmas suffered diminishing contamination in a southeastward direction by old Laurentian crust. A subduction-flip model is proposed, whereby north-dipping subduction under the continental margin followed the accretion of a Mesoproterozoic arc terrane to the Laurentian craton.

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Percival, John A., and Gordon F. West. "The Kapuskasing uplift: a geological and geophysical synthesis." Canadian Journal of Earth Sciences 31, no. 7 (July 1, 1994): 1256–86. http://dx.doi.org/10.1139/e94-110.

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Over the past decade, the Kapuskasing uplift has been the subject of intense geological and geophysical investigation as Lithoprobe's window on the deep-crustal structure of the Archean Superior Province. Enigmatic since its recognition as a positive gravity anomaly in 1950, the structure has been variably interpreted as a suture, rift, transcurrent shear zone, or intracratonic thrust. Diverse studies, including geochronology, geothermobarometry, and various geophysical probes, provide a comprehensive three-dimensional image of Archean (2.75–2.50 Ga) crustal evolution and Proterozoic (2.5–1.1 Ga) cooling and uplift. The data favour an interpretation of the structure as an intracratonic uplift related to Hudsonian collision.Eastward across the southern Kapuskasing uplift, erosion levels increase from < 10 km in the Michipicoten greenstone belt, through the Wawa gneiss domain (10–20 km), into granulites (20–30 km) of the Kapuskasing structural zone, juxtaposed against the low-grade Swayze greenstone belt along the Ivanhoe Lake fault zone. Most volcanic rocks in the greenstone belts erupted in the interval 2750–2700 Ma and were thrust, folded, and cut by late plutons and transcurrent faults before 2670 Ma. Wawa gneisses include major 2750–2660 and minor 2920 Ma tonalitic components, deformed in several events including prominent late subhorizontal extensional shear zones prior to 2645 Ma. Supracrustal rocks of the Kapuskasing zone have model Nd ages of 2750–2700 Ma, metamorphic zircon ages of 2696–2584 Ma, and titanite ages of 2600–2493 Ma, reflecting deposition, intrusion, complex deformation, recrystallization, and cooling during prolonged deep-crustal residence. Postorogenic unroofing rapidly cooled shallow (10–20 km) parts of the Superior Province, but metamorphism and local deformation continued in the ductile deep crust, overlapping the time of late gold deposition in shear zones in the shallow brittle regime.Elevation of granulites, expressed geophysically as positive gravity anomalies and a west-dipping zone of high refraction velocities, dates from a major episode of transpressive faulting. Analysis of deformation effects in Matachewan (2454 Ma), Biscotasing (2167 Ma), and Kapuskasing (2040 Ma) dykes, as well as the brittle nature of fault rocks and cooling patterns of granulites, constrains the time of uplift to ca, 1.9 Ga. Approximately 27 km of shortening was accommodated through brittle upper crustal thrusting and ductile growth of an 8 km thick root in the lower crust that has been maintained by relatively cool, strong mantle lithosphere. The present configuration of the uplift results from overall dextral displacement in which the block was broken and deformed by dextral, normal, and sinistral faults, and modified by later isostatic adjustment. Seismic reflection profiles display prominent northwest-dipping reflectors believed to image lithological contacts and ductile strain zones of Archean age; the indistinct reflection character of the Ivanhoe Lake fault is probably related to its brittle nature formed through brecciation and cataclasis at temperatures < 300 °C. The style and orientation of Proterozoic structures may have been influenced by the Archean crustal configuration.

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Musacchio, Gemma, and Walter D. Mooney. "Seismic evidence for a mantle source for mid-Proterozoic anorthosites and implications for models of crustal growth." Geological Society, London, Special Publications 199, no. 1 (2002): 125–34. http://dx.doi.org/10.1144/gsl.sp.2002.199.01.07.

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Heaman, L. M., and D. E. Moser. "Proterozoic zircon growth in Archean lower crustal xenoliths, southern Superior craton - a consequence of Matachewan ocean opening." Contributions to Mineralogy and Petrology 128, no. 2-3 (July 25, 1997): 164–75. http://dx.doi.org/10.1007/s004100050301.

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Bikramaditya, R. K., A. Krishnakanta Singh, Sun-Lin Chung, Rajesh Sharma, and Hao-Yang Lee. "Zircon U–Pb ages and Lu–Hf isotopes of metagranitoids from the Subansiri region, Eastern Himalaya: implications for crustal evolution along the northern Indian passive margin in the early Paleozoic." Geological Society, London, Special Publications 481, no. 1 (November 22, 2018): 299–318. http://dx.doi.org/10.1144/sp481.7.

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AbstractWe studied the zircon U–Pb ages, Hf isotopes, and whole-rock and mineral chemistry of metagranitoids from the Subansiri region of the Eastern Himalaya to constrain their emplacement age, origin and geodynamic evolution. The investigated metagranitoids have high SiO2, Na2O + K2O, Rb, Zr and low Fe2O3, Nb, Ga/Al ratios with fractionated rare earth element patterns [(Ce/Yb)N = 6.46–42.15] and strong negative Eu anomalies (Eu/Eu* = 0.16–0.44). They are peraluminous (molar A/CNK = 1.04–1.27) and calc-alkaline in nature, with normative corundum (1.04–3.61) and relatively high FeOt/MgO ratios in biotite (c. 3.38), indicating their affinity with S-type granites. The time of emplacement of the Subansiri metagranitoids is constrained by zircon U–Pb ages between 516 and 486 Ma. The zircon grains have negative εHf(t) values ranging from −1.4 to −12.7 and yield crustal Hf model ages from 1.5 to 2.2 Ga, suggesting the occurrence of a major crustal growth event in the Proterozoic and re-melting of the crust during the early Paleozoic. The geochemical data in conjunction with the U–Pb ages and Hf isotope data suggest that the Subansiri metagranitoids were produced by partial melting of older metasedimentary rocks in the Indian passive margin.Supplementary material: Hf isotope results for the Mud Tank zircon standard acquired during the experimental period are available at https://doi.org/10.6084/m9.figshare.c.4299830

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CHEN, BIN, and BOR-MING JAHN. "Geochemical and isotopic studies of the sedimentary and granitic rocks of the Altai orogen of northwest China and their tectonic implications." Geological Magazine 139, no. 1 (January 2002): 1–13. http://dx.doi.org/10.1017/s0016756801006100.

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The Altai orogen (northwest China) represents the southwestern margin of the Central Asian Orogenic Belt. Geochemical and Nd–Sr isotope analyses were carried out on the Palaeozoic sedimentary and granitic rocks in order to trace their sources and to evaluate the pattern of continental growth of the orogen. Nd isotopic data for both the granites and sediments suggest a significant proportion of middle Proterozoic crust beneath the Altai orogen. However, addition of juvenile material (arc/back-arc oceanic crust) during Palaeozoic times is also significant. Trace elements and isotopic data of sediments suggest their sources were immature. They represent mixtures between a Palaeozoic juvenile component and an evolved continental crust. The early Palaeozoic sediments show εNd(T) = −3.4 to −5.0, TDM = 1.5–1.8 Ga, and ISr = 0.710–0.712. They represent a passive margin setting, with a predominance of evolved crustal material in the source. The Devonian sequences, however, might have been deposited in a back-arc basin setting, produced by subduction of the Junggar oceanic crust along the Irtysh fault. A significant addition of arc material into the sedimentary basin is responsible for the highly variable εNd values (−6 to 0) and ISr (0.711–0.706). The Carboniferous rocks were also deposited in a back-arc basin setting but with predominantly arc material in the source as suggested by an abrupt increase in εNd(T) (+6 to +3) and decrease in ISr (0.7045–0.7051). Voluminous syn-orogenic granitoids have εNd(T) = +2.1 to −4.3, ISr = 0.705–0.714 and TDM = 0.7–1.6 Ga. They were not derived by melting of local metasedimentary rocks as suggested by previous workers, but by melting of a more juvenile source at depth. Post-orogenic granites have higher εNd(T) (∼ +4.4) than the syn-orogenic granitoids, indicating their derivation from a deeper crustal level where juvenile crust may predominate.

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Åhäll, Karl-Inge, and James N. Connelly. "Long-term convergence along SW Fennoscandia: 330 m.y. of Proterozoic crustal growth [Precam Res 161 (2008) 452–472]." Precambrian Research 163, no. 3-4 (June 2008): 402–21. http://dx.doi.org/10.1016/j.precamres.2008.02.002.

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Huang, Xiao-Long, Simon A. Wilde, and Jun-Wei Zhong. "Episodic crustal growth in the southern segment of the Trans-North China Orogen across the Archean-Proterozoic boundary." Precambrian Research 233 (August 2013): 337–57. http://dx.doi.org/10.1016/j.precamres.2013.05.016.

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Reinhardt, J. "Low-pressure, high-temperature metamorphism in a compressional tectonic setting: Mary Kathleen Fold Belt, northeastern Australia." Geological Magazine 129, no. 1 (January 1992): 41–57. http://dx.doi.org/10.1017/s0016756800008116.

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AbstractThe Mary Kathleen Fold Belt in northeastern Australia consists of highly deformed, Mid-Proterozoic sedimentary and volcanic sequences as well as intrusives, which were metamorphosed under low-pressure, high-temperature conditions. In the light of current controversy on tectono-thermal settings of low-pressure metamorphic terrains, the interrelations of progressive deformation and metamorphism have been closely examined. Remarkably, there is no direct evidence for syn-metamorphic extensional deformation nor is any significant intrusive activity recorded.Syn-metamorphic structures indicate lateral, bulk coaxial shortening of at least 50–60%. Tight upright folds, pervasive axial planar fabrics, undulating fold axes, and a vertical mineral lineation characterize this deformation. The metamorphic textures, particularly those in andalusite- and/or cordierite-bearing schists, reveal the sequential growth of metamorphic minerals that was synchronous with progressively increasing bulk rock strain. The corresponding metamorphic reactions constrain a prograde P–T path segment that crossed the andalusite and sillimanite stability fields while temperature and pressure increased. After reaching the metamorphic peak, the region cooled down near-isobarically, before major decompression occurred. The prograde–retrograde P–T path forms a complete anticlockwise loop.Due to the lack of evidence for crustal thinning and large-scale magmatism in the upper crust, alternative models are discussed in order to explain the transient high geothermal gradient. These are in particular convective thinning of the lithospheric mantle and fast decompression of crustal sections, possibly linked to tectonic processes preceeding the low-pressure/high-temperature orogenic event.

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Kepezhinskas, Pavel K., Glenn M. D. Eriksen, and Nikita P. Kepezhinskas. "Geochemistry of Ultramafic to Mafic Rocks in the Norwegian Lapland: Inferences on Mantle Sources and Implications for Diamond Exploration." Earth Science Research 5, no. 2 (July 28, 2016): 148. http://dx.doi.org/10.5539/esr.v5n2p148.

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Geology of the Norwegian Lapland is dominated by diverse Archean crystalline basement complexes superimposed with Proterozoic greenstone belts. Isotopic dating of detrital zircons from basement gneisses in the Kirkenes area establishes presence of Early Archean (3.69 Ga) crustal component as well as three major episodes of crustal growth at 3.2 Ga, 2.7-2.9 Ga and 2.5 Ga. Precambrian terranes are intruded by ultramafic-mafic dikes and sills that range in composition from komatiites and ultramafic-mafic lamprophyres to high-Mg basalts and low-Ti subalkaline basalts. Geochemical characteristics of these rocks fall into three principal groups: 1) enriched compositions with high Nd, Nb, Hf, Zr and Th concentrations and elevated La/Th and Nb/Th coupled with low La/Nb, Ba/Nb and U/Nb ratios; 2) compositions depleted in Th, Hf and Nb together with low LREE/HFSE (such as La/Nb) and LILE/HFSE (such as Ba/Nb and U/Nb) ratios; 3) transitional group clearly identified by marked depletions in Ti, Nb and Ta contents coupled with enrichment in Th and U and other large-ion lithophile elements (LILE). These geochemical characteristics are interpreted within the framework of two principal source models: 1) derivation of parental ultramafic-mafic melts from multiple mantle sources (depleted to enriched) inherited from Archaean lithospheric tectonics and 2) a single primitive mantle source which underwent several depletion and enrichment episodes, at least partially associated with subduction zone processes. Subduction modification of depleted lithospheric mantle was assisted by accretion of subducted sediment to depleted mantle source at Archean, Proterozoic or Early Paleozoic convergent margin. Alkaline ultramafic rocks such as lamprophyres and mica picrites display geochemical characteristics supportive of their origin within stability field of diamond in a deep mantle beneath Norwegian Arctic margin which, together with other lithospheric characteristics, suggests its high potential for hosting economic diamond mineralization.

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Alekseev, N. L., I. A. Kamenev, E. V. Mikhalskyd, A. N. Larionov, I. N. Kapitonov, E. S. Bogomolov, and M. S. Egorov. "Multistage Evolution of Proterozoic Crust of East Antarctica by the Example of the Filla Terrane (Rauer Islands): New Geological and Isotope Data." Russian Geology and Geophysics 62, no. 5 (May 1, 2021): 557–75. http://dx.doi.org/10.2113/rgg20194068.

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Abstract —The paper presents new data on the Rauer Islands, one of the unique objects of the East Antarctic Shield. The interest in this area is triggered by its complex geologic structure, including both Archean and Proterozoic fragments of the Earth’s crust, and by its multiphase formation. A detailed scheme of the geologic structure of the area is proposed, new petrologic complexes are revealed, and the stages of tectonomagmatic activity at ~1400–1320 Ma and 1150 Ma are reliably dated. This serves as a factual basis for comparison the study area with other regions of East Antarctica. Based on the geological and isotope data obtained, the Meso–Neoproterozoic Filla Terrane in the area of the Rauer Islands is recognized. It is composed of metamorphic and primarily intrusive rocks, whose protoliths formed in the time interval 1400–950 Ma. Three periods of tectonothermal activity have been established in the Filla Terrane: Mid-Mesoproterozoic (1400–1320 Ma), Meso–Neoproterozoic (1150–886 Ma), and early Cambrian (536–504 Ma). The first period is the formation time of Mesoproterozoic crust, and it is time-correlated with the tectonogenesis phase in the adjacent Rayner province. The second period corresponds to the later phase of tectonothermal activity in the Rayner province. In the Filla Terrane, this period can be divided into two intervals, 1150–1100 Ma and 1010–886 Ma. The former interval is treated as intense crustal growth in the course of granitoid and mantle magmatism. The latter interval is a period of tectonothermal processes accompanied by intense deformations, high-temperature metamorphism, and intrusion of porphyritic granitoids. Apparently, the gap between the first and the second intervals is the time of deposition of the sedimentary protolith of paragneisses, which, together with the surrounding rocks, underwent high-temperature metamorphism and deformations at 950–914 Ma. The synchronous evolution of the Archean block and the Filla Terrane began at least within 1100–1000 Ma. The youngest, early Cambrian period of tectonic activity coincides with the development of local low-temperature mylonite zones and the intrusion of synkinematic pegmatite veins. Thus, the tectonothermal evolution of the Filla Terrane includes almost the same main phases of crustal growth and transformation as the Rayner province. This indicates that the Filla Terrane is a fragment of the Rayner province, which accreted to the Archean terrane at least in the late Mesoproterozoic.

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29

Swain, G., K. Barovich, M. Hand, G. Ferris, and M. Schwarz. "Petrogenesis of the St Peter Suite, southern Australia: Arc magmatism and Proterozoic crustal growth of the South Australian Craton." Precambrian Research 166, no. 1-4 (October 2008): 283–96. http://dx.doi.org/10.1016/j.precamres.2007.07.028.

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30

Mueller, P. A., and C. D. Frost. "The Wyoming Province: a distinctive Archean craton in Laurentian North America." Canadian Journal of Earth Sciences 43, no. 10 (October 1, 2006): 1391–97. http://dx.doi.org/10.1139/e06-075.

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The Wyoming Province is a distinctive Archean craton in the northwestern United States that can be subdivided into three subprovinces, namely, from oldest to youngest, the Montana metasedimentary province, the Beartooth–Bighorn magmatic zone, and the Southern accreted terranes. Archean rocks of the Montana metasedimentary province and the Beartooth–Bighorn magmatic zone are characterized by (1) their antiquity (rock ages to 3.5 Ga, detrital zircon ages up to 4.0 Ga, and Nd model ages exceeding 4.0 Ga); (2) a distinctly enriched 207Pb/204Pb isotopic signature, which suggests that this part of the province was not produced by the amalgamation of exotic terranes; and (3) a distinctively thick (15–20 km), mafic lower crust. The Montana metasedimentary province and Beartooth–Bighorn magmatic zone were cratonized by about 3.0–2.8 Ga. Crustal growth occurred via continental-arc magmatism and terrane accretion in the Southern accreted terranes along the southern margin of the province at 2.68–2.50 Ga. By the end of the Archean, the three subprovinces were joined as part of what is now the Wyoming Province. Subsequent to amalgamation of the Wyoming crust to Laurentia at ca. 1.8–1.9 Ga, Paleoproterozoic crust (1.7–2.4 Ga) was juxtaposed along the southern and western boundaries of the province. Subsequent tectonism and magmatism in the Wyoming region are concentrated in the areas underlain by these Proterozoic mobile belts.

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Kozakov, I. K., T. I. Kirnozova, M. M. Fugzan, and Yu V. Plotkina. "Stages of the Early Proterozoic Lower Crustal Growth in the Central Asian Orogenic Belt with Reference to the Baidarik Terrane." Petrology 30, no. 2 (March 12, 2022): 133–46. http://dx.doi.org/10.1134/s0869591122020035.

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32

Maboko, M. A. H., and E. Nakamura. "Nd and Sr isotopic mapping of the Archaean-Proterozoic boundary in southeastern Tanzania using granites as probes for crustal growth." Precambrian Research 77, no. 1-2 (March 1996): 105–15. http://dx.doi.org/10.1016/0301-9268(95)00048-8.

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33

Zhai, Mingguo, and Brian F. Windley. "The Archaean and early Proterozoic banded iron formations of North China: their characteristics, geotectonic relations, chemistry and implications for crustal growth." Precambrian Research 48, no. 3 (October 1990): 267–86. http://dx.doi.org/10.1016/0301-9268(90)90012-f.

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34

Robinson, F. A., J. Toro, and V. Pease. "U-Pb and oxygen isotope characteristics of Timanian- and Caledonian-age detrital zircons from the Brooks Range, Arctic Alaska, USA." GSA Bulletin 131, no. 9-10 (February 15, 2019): 1459–79. http://dx.doi.org/10.1130/b35036.1.

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AbstractThe Devonian connection between the Brooks Range of Alaska, USA, with the continental margin of Arctic Canada and its subsequent Jurassic–Cretaceous counterclockwise rotation to form the Amerasian Basin, is a highly debated topic in Arctic tectonics. This resource-rich region was assembled from terranes that formed part of Laurentia or Baltica, or were juvenile oceanic arcs in the early Paleozoic that were brought together during Caledonian Orogenesis and the subsequent collision that formed Pangea (Uralide Orogeny). Elements of these orogens, as well as older ones, are predicted to occur in the Brooks Range of Arctic Alaska. This study presents the first combined zircon U-Pb and oxygen data from six Brooks Range metasedimentary units with assumed Neoproterozoic to Devonian ages. Three distinct detrital zircon patterns are identified in these units: (1) those with Neoproterozoic maximum depositional ages characteristic of the Timanide Orogen of northern Baltica and adjacent parts of Siberia, (2) an almost unimodal Siluro–Ordovician (443.5 ± 2.3 Ma) detrital zircon population consistent with the oceanic Apoon arc believed to have existed off shore of northern Laurentia and to have accreted to the North Slope subterrane during the Caledonian event, and (3) those with Middle Devonian maximum depositional ages consistent with post-accretion extension during the final (Scandian) phase of Caledonian Orogenesis. Oxygen isotopes from the same zircons reveal minor to significant crustal contamination with approximately two thirds (n = 255/405) having δ18O values >5.9‰ (above the mantle field of 5.3 ± 0.6‰). Pattern 1 units exhibit a progressive increase in δ18O values throughout the Proterozoic (5.99 to 9.29‰) indicative of increasing crustal growth and Timanide age zircons yield average δ18O values of 7.18 ± 0.64‰ (n = 26) suggestive of more crustal influence than Caledonian age zircons, possibly reflecting northern Baltica signatures. The unimodal population in Pattern 2 yields average δ18O values of 5.49 ± 0.66‰ (n = 17) and 6.02 ± 0.27‰ (n = 23) prior to and during, respectively, the main Caledonian event and suggest derivation from Devonian juvenile arc sources possibly representing the initiation of the collision between Laurentia and Baltica. Similar to Pattern 1, the δ18O values associated with Pattern 3 show a progressive increase in δ18O values throughout the Proterozoic (5.00 to 9.39‰). However, Pattern 3 also exhibits a distinct juvenile fingerprint (6.13 ± 0.24‰, n = 51) during the main Caledonian event and a slight increase to 7.12 ± 1‰ (n = 7) in post-Caledonian zircons possibly suggest correlating with a post-accretion phase in which proximally sourced zircon-bearing detritus was deposited in extension-related basins marking the joining of Laurentia and Baltica.

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35

Böhm, Christian O., Larry M. Heaman, and M. Timothy Corkery. "Archean crustal evolution of the northwestern Superior craton margin: U-Pb zircon results from the Split Lake Block." Canadian Journal of Earth Sciences 36, no. 12 (December 1, 1999): 1973–87. http://dx.doi.org/10.1139/e99-088.

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The Split Lake Block forms a partly retrogressed, granulite-grade basement segment located at the northwestern margin of the Superior Province in Manitoba. Unlike other segments along the craton margin, the effects of Proterozoic tectonism are relatively minor in the Split Lake Block, making it amenable to establishing firm temporal constraints for the Archean magmatic and metamorphic history of the northwestern Superior Province margin. Consequently, samples from the main lithological units within the Split Lake Block were selected for precise single-grain U-Pb zircon geochronology. Heterogeneous zircon populations isolated from representative enderbite, tonalite, and granodiorite samples reveal a complex growth history with pre-2.8 Ga protolith ages (e.g., 2841 ± 2 Ma tonalite), possibly as old as 3.35 Ga as indicated in a granodiorite sample. The youngest Archean granitic magmatism identified in the eastern Split Lake Block is represented by the 2708 ± 3 Ma Gull Lake granite. A U-Pb zircon age of 2695+4-1 Ma obtained for leucosome in mafic granulite is interpreted to reflect the timing of granulite-grade metamorphism in the Split Lake Block, supported by polyphase zircon growth and (or) lead loss at ca. 2.7 Ga in the enderbite sample. A younger phase of metamorphic zircon growth at ca. 2.62 Ga is documented in the tonalite and granodiorite zircon populations. The 2.70-2.71 Ga crust formation, the occurrence of ca. 2695 Ma high-grade metamorphism, and broadly contemporaneous Paleoproterozoic mafic dykes in both the Split Lake Block and Pikwitonei Granulite Domain imply a common evolution of these high-grade terrains along the northwestern Superior craton margin since the late Archean.

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Wade, B. P., K. M. Barovich, M. Hand, I. R. Scrimgeour, and D. F. Close. "Evidence for Early Mesoproterozoic Arc Magmatism in the Musgrave Block, Central Australia: Implications for Proterozoic Crustal Growth and Tectonic Reconstructions of Australia." Journal of Geology 114, no. 1 (January 2006): 43–63. http://dx.doi.org/10.1086/498099.

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37

Lachhana Dora, M., Dewashish Upadhyay, Vivek P. Malviya, Tushar Meshram, Srinivas R. Baswani, Kirtikumar Randive, Rajkumar Meshram, G. Suresh, Rashmi Naik, and S. Ranjan. "Neoarchaean and Proterozoic crustal growth and reworking in the Western Bastar Craton, Central India: Constraints from zircon, monazite geochronology and whole-rock geochemistry." Precambrian Research 362 (August 2021): 106284. http://dx.doi.org/10.1016/j.precamres.2021.106284.

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38

Bell, Keith, John Blenkinsop, S. T. Kwon, G. R. Tilton, and R. P. Sage. "Age and radiogenic isotopic systematics of the Borden carbonatite complex, Ontario, Canada." Canadian Journal of Earth Sciences 24, no. 1 (January 1, 1987): 24–30. http://dx.doi.org/10.1139/e87-003.

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Rb–Sr and U–Pb data from the Borden complex of northern Ontario, a carbonatite associated with the Kapuskasing Structural Zone, indicate a mid-Proterozoic age. A 207Pb/206Pb age of 1872 ± 13 Ma is interpreted as the emplacement age of this body, grouping it with other ca. 1900 Ma complexes that are the oldest known carbonatites associated with the Kapuskasing structure. A 206Pb–238U age of 1894 ± 29 Ma agrees with the Pb–Pb age but has a high mean square of weighted deviates (MSWD) of 42. A Rb–Sr apatite–carbonate–mica whole-rock isochron date of 1807 ± 13 Ma probably indicates later resetting of the Rb–Sr system.An εSr(T) value of −6.2 ± 0.5 (87Sr/86Sr = 0.70184 ± 0.00003) and an εNd(T) value of +2.8 ± 0.4 for Borden indicate derivation of the Sr and Nd from a source with a time-integrated depletion in the large-ion lithophile (LIL) elements. These closely resemble the ε values for Sr and Nd from the Cargill and Spanish River complexes, two other 1900 Ma plutons. The estimated initial 207Pb/204Pb and 206Pb/204Pb ratios from Borden calcites plot significantly below growth curves for average continental crust in isotope correlation diagrams, a pattern similar to those found in mid-ocean ridge basalts (MORB) and most ocean-island volcanic rocks, again suggesting a source depleted in LIL elements. The combined Nd and Sr, and probably Pb, data strongly favour a mantle origin for the Borden complex with little or no crustal contamination and support the model of Bell et al. that many carbonatites intruded into the Canadian Shield were derived from an ancient, LIL-depleted subcontinental upper mantle.

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39

Tella, S., and K. E. Eade. "Occurrence and possible tectonic significance of high-pressure granulite fragments in the Tulemalu fault zone, District of Keewatin, N.W.T., Canada." Canadian Journal of Earth Sciences 23, no. 12 (December 1, 1986): 1950–62. http://dx.doi.org/10.1139/e86-181.

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Fragments of garnet–clinopyroxene granulite with corona textures in ductilely deformed lower-amphibolite-grade quartzofeldspathic granitoid gneiss are exposed within the northeast-trending Tulemalu fault zone. The mineral association of the fragments is garnet–clinopyroxene–plagioclase(An20–An22)–quartz–opaques–hornblende–biotite. Textural evidence suggests that hornblende and biotite are late overgrowth minerals. Garnet and clinopyroxene and (or) hornblende are separated by a narrow rim of plagioclase. Pressure–temperature estimates based on currently used geothermobarometers are of the order of 715–789 °C and 10.2–11.4 kbar (1 kbar = 100 MPa) for the garnet–clinopyroxene–plagioclase–quartz assemblage. The fragments are interpreted as relicts of deep-crustal materials, uplifted to higher levels probably as xenolithic rafts in a granitic melt along the fault zone during late Archean or Early Proterozoic ductile displacements. The growth of hornblende and the development of plagioclase reaction rims around garnet are believed to be due to isothermal decompression reactions during uplift.On the basis of limited geological data, paired gravity anomaly patterns, and aeromagnetic interpolation, the Tulemalu fault zone is postulated as representing the northeasterly extension of the Virgin River – Black Lake fault zones of Saskatchewan and represents an approximately 5 km wide ductile deformation zone that separates an Archean granulite terrane to the west from a relatively lower grade terrane composed of Archean supracrustal rocks to the east.

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40

Moscati, Richard J., Wayne R. Premo, Ed H. DeWitt, and Joseph L. Wooden. "U-Pb ages and geochemistry of zircon from Proterozoic plutons of the Sawatch and Mosquito ranges, Colorado, U.S.A.: Implications for crustal growth of the central Colorado province." Rocky Mountain Geology 52, no. 1 (2017): 17–106. http://dx.doi.org/10.24872/rmgjournal.52.1.17.

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41

Kerr, Andrew, and Brian J. Fryer. "The importance of late- and post-orogenic crustal growth in the early Proterozoic: evidence from SmNd isotopic studies of igneous rocks in the Makkovik Province, Canada." Earth and Planetary Science Letters 125, no. 1-4 (July 1994): 71–88. http://dx.doi.org/10.1016/0012-821x(94)90207-0.

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42

Corfu, F., and G. M. Stott. "U–Pb geochronology of the central Uchi Subprovince, Superior Province." Canadian Journal of Earth Sciences 30, no. 6 (June 1, 1993): 1179–96. http://dx.doi.org/10.1139/e93-100.

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U–Pb zircon and titanite ages for rocks of the central Uchi Subprovince in northwestern Ontario indicate a late Archean magmatic and tectonic development spanning over 200 Ma. An early period at 2900–2800 Ma formed volcano-plutonic complexes, presumably linked to 3.1–2.8 Ga terrains of the northwestern Superior Province. A later period of southward growth by magmatic and tectonic accretion occurred at 2750–2710 Ma and was concluded by large scale compression and plutonism at 2700 Ma.The oldest 2890–2860 and 2840–2820 Ma components occur in the Pickle Lake and Meen–Dempster greenstone belts and as gneisses in the Seach–Achapi and the Lake St. Joseph batholiths in northern and central sectors of the region. Together with distinct 2750–2740 Ma volcano-plutonic complexes they form a collage assembled by multiple episodes of tectonic juxtaposition and magmatic accretion. Plutons of 2730–2710 Ma age are intrusive into these older, northern domains, whereas their volcanic counterparts compose the Lake St. Joseph and Miminiska – Fort Hope greenstone belts to the south. Late-tectonic to posttectonic granitoid rocks intruded a region extending from the northern Berens River Subprovince to the southern English River Subprovince at 2700 Ma. These plutons were cut by regional scale faults formed by residual north-northwest directed shortening. The timing of this movement seems to be recorded by titanite ages of 2690–2670 Ma. Reactivation of the same faults may account for Proterozoic Pb loss observed in some of the zircon populations. The age patterns are consistent with crustal growth along a continental margin in a north-dipping subduction environment.

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Bertrand, Jean-Michel, J. Christopher Roddick, Martin J. van Kranendonk, and Ingo Ermanovics. "U–Pb geochronology of deformation and metamorphism across a central transect of the Early Proterozoic Torngat Orogen, North River map area, Labrador." Canadian Journal of Earth Sciences 30, no. 7 (July 1, 1993): 1470–89. http://dx.doi.org/10.1139/e93-127.

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The Early Proterozoic Torngat Orogen resulted from the oblique collision of the Archean Nain and southeastern Rae provinces and evolved in four stages: (0) deposition of platformal supracrustal assemblages followed by subduction-related arc magmatism in the margin of the Rae Province; (I) crustal thickening and nappe tectonics; (II) sinistral transpression and formation of the Abloviak shear zone; (III) uplift on steeply dipping, east-verging mylonites along the eastern orogenic front.U–Pb geochronology on zircon and monazite from major rock units and syntectonic intrusions indicates that arc magmatism at ca. 1880 Ma was followed by 40 Ma. of deformation and high-grade metamorphism from ca. 1860 to 1820. Subsequent uplift and final cooling occurred ca. 1795 – 1770 Ma. Several ages of mineral growth that correspond to distinct structural and metamorphic events have been recognized: (1) 1858 – 1853 Ma zircon and monazite dates are interpreted as the minimum age of stage I and peak metamorphic conditions; (2) 1844 Ma zircons from anatectic granitoids in the Tasiuyak gneiss complex (TGC), syntectonic with stage II deformation, are interpreted to date the formation of the Abloviak shear zone; (3) 1837 Ma magmatic zircons from an intrusive granite vein deformed along the western contact of the TGC represent a discrete intrusive event; (4) 1825 – 1822 Ma metamorphic overgrowths and newly grown zircons in granitic veins from the western portion of the orogen (Lac Lomier complex) represent a period of renewed transpressional deformation; (5) 1806 Ma magmatic zircons from a post-stage II granite emplaced along the eastern edge of the Abloviak shear zone defines the transition between stage II and stage III events; (6) 1794 – 1773 Ma zircons from leucogranites and pegmatites that are associated with uplift of the orogen (stage III). 1780 – 1740 Ma dates for monazite and a 40Ar/39Ar hornblende age correspond to the latest stages of uplift and cooling of the orogen.

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44

Dunlop, David J. "Grenvillia and Laurentia — a Precambrian Wilson cycle?" Canadian Journal of Earth Sciences 51, no. 3 (March 2014): 187–96. http://dx.doi.org/10.1139/cjes-2013-0101.

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John Tuzo Wilson coined the term “plate” in plate tectonics. He is famous for inventing transform boundaries, hot spot tracks, and the Wilson cycle of ocean birth, growth, and decline. Less well remembered is his work in the 1950s on tectonic and radiometric age provinces of the Canadian Shield, as part of which he fathered U/Pb geochronology in Canada. This work gave strong support to the notion of continental growth through accretion of successively younger terranes onto an ancient cratonic core. The present paper reviews how paleomagnetism can trace the motions of continents to test Wilson’s ideas. Continental accretion often involves deep burial of one of the colliding elements through subduction or crustal underplating; such was the case with the Grenville orogen and its subprovinces in their Proterozoic accretion onto the Laurentian craton. The resulting heating and metamorphism erases most pre-collisional magnetic information but adds something new: the possibility of following the post-metamorphic uplift and cooling history, in time and space. The time element is provided by a new form of isotopic geochronology, thermochronometry, which provides dates for specific minerals together with the temperatures at which they became closed to isotopic migration. U/Pb dating of sphene is one method used; another is the 40Ar/39Ar variant of K/Ar dating applied to hornblende, micas, and feldspars, which have a wide range of Ar closure temperatures. The two specific Grenville studies described deal with parallel uplift histories determined by 40Ar/39Ar dating and by magnetics for the accreted terranes of the Central Metasedimentary Belt in Ontario and with the paleomagnetic detection of the post-1240 Ma closing of a small ocean between the Elsevir terrane and Laurentia during the Grenvillian orogeny.

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45

Stevens, R. A., P. Erdmer, R. A. Creaser, and S. L. Grant. "Mississippian assembly of the Nisutlin assemblage: evidence from primary contact relationships and Mississippian magmatism in the Teslin tectonic zone, part of the Yukon–Tanana terrane of south-central Yukon." Canadian Journal of Earth Sciences 33, no. 1 (January 1, 1996): 103–16. http://dx.doi.org/10.1139/e96-011.

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Metamorphosed and ductilely deformed sedimentary, plutonic, and volcanic rocks of the Nisutlin and Anvil assemblages make up the Yukon–Tanana terrane in the Teslin tectonic zone study area. The Nisutlin assemblage consists of siliceous schist–quartzite and graphitic phyllite that share a primary depositional contact, and Early Mississippian tonalite to quartz diorite that intrudes the siliceous schist–quartzite and possibly the graphitic phyllite. The Anvil assemblage includes metagabbro and mafic schist–greenstone that share an intrusive contact relationship. Tonalite to quartz diorite of the Nisutlin assemblage is characterized by minor zircon inheritance with an average Proterozoic age, εNd(350 Ma) values of −2.5 to −6.2, and Nd model ages of 1.50–1.79 Ga. These data suggest that the magmatic bodies have inherited a component of continentally derived material. Primary contact relationships and age data indicate that the Nisutlin assemblage had formed by Mississippian time, and regional correlations show that this assemblage makes up a large part of the Yukon–Tanana terrane of southern Yukon. Assembly of the Nisutlin assemblage by Mississippian time indicates that it did not form as a late Paleozoic and early Mesozoic subduction melange, and it suggests that its tectonic fabrics did not result from the progressive growth of a Permo-Triassic subduction complex. We suggest that the Nisutlin assemblage was part of a crustal block that lay outboard of North America in Mississippian time, and that it lay in the hanging-wall plate of a Permo-Triassic subduction zone as a relatively coherent assemblage, rather than forming within the zone as a subduction complex.

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Scandolara, Jaime E., Pedro S. E. Ribeiro, Antônio A. S. Frasca, Reinhardt A. Fuck, and Joseneusa B. Rodrigues. "Geochemistry and geochronology of mafic rocks from the Vespor suite in the Juruena arc, Roosevelt-Juruena terrain, Brazil: Implications for Proterozoic crustal growth and geodynamic setting of the SW Amazonian craton." Journal of South American Earth Sciences 53 (August 2014): 20–49. http://dx.doi.org/10.1016/j.jsames.2014.04.001.

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47

Sesha Sai, V. V. "Proterozoic granite magmatism along the terrane boundary tectonic zone to the east of Cuddapah basin, Andhra Pradesh — petrotectonic implications for precambrian crustal growth in Nellore schist belt of eastern Dharwar craton." Journal of the Geological Society of India 81, no. 2 (February 2013): 167–82. http://dx.doi.org/10.1007/s12594-013-0020-z.

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Kretz, R., R. Hartree, D. Garrett, and C. Cermignani. "Petrology of the Grenville swarm of gabbro dikes, Canadian Precambrian Shield." Canadian Journal of Earth Sciences 22, no. 1 (January 1, 1985): 53–71. http://dx.doi.org/10.1139/e85-005.

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The Grenville tholeiitic dikes of Late Proterozoic or early Paleozoic age cut marbles and gneisses of the Grenville Province within and adjacent to the Ottawa rift structure. Where traversed the swarm consists of about 40 large dikes (up to 100 m wide) representing a crustal extension of 1 km. The principal minerals are olivine, augite, pigeonite, plagioclase, magnetite, ilmenite, K-feldspar, and quartz. Crystals of pigeonite around olivine and complex augite–pigeonite composite grains suggest that the reactions olivine + melt → pigeonite and pigeonite + melt → augite have taken place. Conspicuous zoning and grain to grain variation in the composition of augite are consistent with fractional crystallization, but crystal – melt equilibrium during crystal growth is indicated by a restricted range in pyroxene paleotemperatures of 1180–1060 °C. Rock textures (subophitic, combined ophitic–subophitic, and equigranular) in dike centres are related to dike width and are determined principally by the influence of cooling rate on the nucleation of augite. The K2O content of the gabbro (centres of 15 dikes, 3–100 mm wide) ranges from 0.2 to 1.2% and is closely correlated with other elements, positively with Ti, Na, P, Rb, Sr, Y, Zr, and Ba, and negatively with Mg, Ca, and Cr. Relatively minor within-dike variation exists in the form of local (centimetre-scale) inhomogeneity, slight enrichment in K and Na, and depletion in Ca and Mg in the centre of one large dike and complex rhythmic variation in K, Na, Ca, and Fe across one small dike. Centre–margin comparisons in several large dikes indicate minor residence con tamination (Ca, Mg) in the margins of some dikes cutting marble. Of the various possible causes for variation in composition, those favoured at present are Fractional crystallization at depth (separation of augite and plagioclase), the partial preservation of compositional heterogeneity during intrusion, and the gravitational sinking of early formed crystals (with the upward displacement of K-enriched melt) in the central regions of large dikes.

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Huhma, H., S. Claesson, P. D. Kinny, and I. S. Williams. "The growth of Early Proterozoic crust: new evidence from Svecofennian detrital zircons." Terra Nova 3, no. 2 (March 1991): 175–78. http://dx.doi.org/10.1111/j.1365-3121.1991.tb00870.x.

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Dhuime, Bruno, Chris J. Hawkesworth, Hélène Delavault, and Peter A. Cawood. "Rates of generation and destruction of the continental crust: implications for continental growth." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 376, no. 2132 (October 2018): 20170403. http://dx.doi.org/10.1098/rsta.2017.0403.

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Less than 25% of the volume of the juvenile continental crust preserved today is older than 3 Ga, there are no known rocks older than approximately 4 Ga, and yet a number of recent models of continental growth suggest that at least 60–80% of the present volume of the continental crust had been generated by 3 Ga. Such models require that large volumes of pre-3 Ga crust were destroyed and replaced by younger crust since the late Archaean. To address this issue, we evaluate the influence on the rock record of changing the rates of generation and destruction of the continental crust at different times in Earth's history. We adopted a box model approach in a numerical model constrained by the estimated volumes of continental crust at 3 Ga and the present day, and by the distribution of crust formation ages in the present-day crust. The data generated by the model suggest that new continental crust was generated continuously, but with a marked decrease in the net growth rate at approximately 3 Ga resulting in a temporary reduction in the volume of continental crust at that time. Destruction rates increased dramatically around 3 billion years ago, which may be linked to the widespread development of subduction zones. The volume of continental crust may have exceeded its present value by the mid/late Proterozoic. In this model, about 2.6–2.3 times of the present volume of continental crust has been generated since Earth's formation, and approximately 1.6–1.3 times of this volume has been destroyed and recycled back into the mantle. This article is part of a discussion meeting issue ‘Earth dynamics and the development of plate tectonics'.

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Journal articles on the topic 'Proterozoic crustal growth'

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