Journal articles: 'Basement inlier'

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Heaman, L. M., Philippe Erdmer, and J. V. Owen. "U–Pb geochronologic constraints on the crustal evolution of the Long Range Inlier, Newfoundland." Canadian Journal of Earth Sciences 39, no. 5 (May 1, 2002): 845–65. http://dx.doi.org/10.1139/e02-015.

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The Long Range Mountains of Newfoundland expose the northeastern most basement inlier of the Appalachian Orogen. UPb results for two samples of basement gneiss reveal crustal formation ages of 1466 ± 10 Ma (Western Brook Pond charnockite) and 1530 ± 8 Ma (Cat Arm Road gneiss), indicating an affinity with Pinwarian magmatism (15101450 Ma) in Labrador. A third sample of basement gneiss from the Cat Arm Road dam site yielded a minimum formation age of 1631 Ma. These basement gneisses were intruded by granite plutons during two periods of Grenvillian magmatism; Group I at 10321022 Ma and Group II at 993985 Ma. Group I intrusions include the 1032.0 ± 1.5 Ma Lomond River granite and the 1022.0 ± 2.0 Ma Lake Michel igneous suite; Group II intrusions include the 999 ± 4 Ma Potato Hill charnockite, 993 ± 7 Ma Horse Chops granite, 984.9 ± 1.6 Ma Cloud River granite, and may include the Apsy granite. The metamorphic history of the Long Range Inlier is complex and three discrete Proterozoic metamorphic events can be delineated on the basis of field relationships and UPb dates for metamorphic minerals. M1 metamorphism is a regional high-grade event that occurred prior to 1032 Ma, the emplacement age for the unmetamorphosed Lomond River granite. M2 and M3 occurred at 1022 and 989 Ma, respectively; coinciding with the two main periods of Grenvillian magmatism. The Precambrian crustal evolution of the Long Range Inlier is very similar to the Pinware terrane of Labrador, consistent with a single contiguous terrane presently separated by the Gulf of St. Lawrence. A surprising discovery from this study is identification of the first known occurrence of Silurian mafic magmatism in the Long Range Inlier, the 430.5 ± 2.5 Ma Taylor Brook gabbro.

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ALESSIO, BRANDON L., MORGAN L. BLADES, GEORGE MURRAY, BENJAMIN THORPE, ALAN S. COLLINS, DAVID E. KELSEY, JOHN FODEN, JUSTIN PAYNE, SALAH AL-KHIRBASH, and FRED JOURDAN. "Origin and tectonic evolution of the NE basement of Oman: a window into the Neoproterozoic accretionary growth of India?" Geological Magazine 155, no. 5 (March 7, 2017): 1150–74. http://dx.doi.org/10.1017/s0016756817000061.

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AbstractThe Omani basement is located spatially distant from the dominantly juvenile Arabian–Nubian Shield (ANS) to its west, and its relationship to the amalgamation of those arc terranes has yet to be properly constrained. The Jebel Ja'alan (NE Oman) basement inlier provides an excellent opportunity to better understand the Neoproterozoic tectonic geography of Oman and its relationship to the ANS. To understand the origin of this basement inlier, we present new radiogenic isotopic data from igneous bodies in Jebel Ja'alan. U–Pb and 40Ar/39Ar geochronological data are used to constrain the timing of magmatism and metamorphism in the jebel. Positive εHf and εNd values indicate a juvenile origin for the igneous lithologies. Phase equilibria modelling is used to constrain the metamorphic conditions recorded by basement. Pressure–temperature (P–T) pseudosections show that basement schists followed a clockwise P–T path, reaching peak metamorphic conditions of c. 650–700°C at 4–7.5 kbar, corresponding to a thermal gradient of c. 90–160°C/kbar. From the calculated thermal gradient, in conjunction with collected trace-element data, we interpret that the Jebel Ja'alan basement formed in an arc environment. Geochronological data indicate that this juvenile arc formed during Tonian time and is older than basement further west in Oman. We argue that the difference in timing is related to westwards arc accretion and migration, which implies that the Omani basement represents its own tectonic domain separate to the ANS and may be the leading edge of the Neoproterozoic accretionary margin of India.

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Cooper, A. H., and S. G. Molyneux. "The age and correlation of Skiddaw Group (early Ordovician) sediments in the Cross Fell inlier (northern England)." Geological Magazine 127, no. 2 (March 1990): 147–57. http://dx.doi.org/10.1017/s0016756800013832.

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AbstractThe Skiddaw Group in the Cross Fell inlier comprises the Catterpallot Formation of latest Tremadoc or earliest Arenig age, the Murton Formation of Arenig age, and the Kirkland Formation of early Llanvirn age. Each of these formations can be correlated with formations in the Skiddaw Group of the Lake District. The faulted contact of the Catterpallot and Kirkland formations is the probable extension of the Causey Pike Fault (CPF), which separates two distinct sequences in the Skiddaw inlier of the northern Lake District. Contrasts across the CPF in the Cross Fell inlier reflect those seen in the Skiddaw inlier. The CPF is a major basement structure, separating markedly different successions in the Ordovician strata of northern England.

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Didenko, A. N., I. K. Kozakov, and A. V. Dvorova. "Paleomagnetism of granites from the Angara-Kan basement inlier, Siberian craton." Russian Geology and Geophysics 50, no. 1 (January 2009): 57–62. http://dx.doi.org/10.1016/j.rgg.2008.04.008.

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Van Baelen, Hervé, and Manuel Sintubin. "Kinematic consequences of an angular unconformity in simple shear: an example from the southern border of the Lower Palaeozoic Rocroi inlier (Naux, France)." Bulletin de la Société Géologique de France 179, no. 1 (January 1, 2008): 73–87. http://dx.doi.org/10.2113/gssgfbull.179.1.73.

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AbstractThe presence of an angular unconformity in combination with complex structures in the basement, lacking in the cover, is commonly seen as an indication for an orogenic event pre-dating the unconformity. The recognition of such an older orogenic event becomes, however, less evident in areas where both cover and basement were deformed together during an orogen post-dating the angular unconformity.The validity of this common interpretation has been evaluated at the southern border of the Lower Palaeozoic Rocroi basement inlier (Naux, northern France), where the basement-cover interface is very well exposed. This basement-cover interface, showing an angular unconformity, has classically been interpreted as evidence for an early Palaeozoic tectonometamorphic event, called the Ardennian orogeny, though only one penetrative cleavage, co-genetic with the structures present in both cover and basement, can be observed.A detailed geometrical study shows, however, that the presence of a tilted basement, involving the angular unconformity, provokes a rheological heterogeneity that causes a contrasting response of basement and cover with respect to the Variscan shortening. While Variscan progressive deformation gave rise to a rather regular cleavage refraction pattern in the subhorizontal multilayer cover sequence, a complex deformation, expressed by non-cylindrical folds, boudinage and shearing developed in the basement. The basement-cover interface itself played no rheological role, but has been passively sheared and folded as a consequence of the deformation of the basement. This study proves that the deformed basement-cover interface, allowing to link deformation in basement and cover, is a necessary tool to properly interpret complex deformation in the basement. With respect to the regional geodynamic evolution of the northern parts of the Central European Variscides, our kinematic model indeed demonstrates that this classical outcrop area bears no evidence for an early Palaeozoic orogenic event, and that the angular unconformity reflects the late Silurian – early Devonian onset of the Ardenne-Eifel basin development, rather than a middle Ordovician Ardennian orogeny.

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Skourtsos, E., H. Kranis, A. Zambetakis-Lekkas, R. Gawthorpe, and M. Leeder. "ALPINE BASEMENT OUTCROPS AT NORTHERN PELOPONNESUS: IMPLICATIONS FOR THE EARLY STAGES IN THE EVOLUTION OF THE CORINTH RIFT." Bulletin of the Geological Society of Greece 50, no. 1 (July 27, 2017): 153. http://dx.doi.org/10.12681/bgsg.11714.

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We focus on the central and eastern southern onshore parts of the Corinth Rift (CR), where basement outcrops are few and of limited extent, to study three key locations: a basement inlier east of Xylokastro, a new outcrop of the Tripolis Unit at the western edge of the Xylokastro horst, and a re-mapped and re-evaluated outcrop of the Pindos Unit northwest of Nemea. The results of this study show that there are elements which could help overcome the significant difficulties in our understanding of the structure and evolution of the rift, posed by the lack of basement outcrops in the central and eastern onshore parts of the Rift. This, in turn, calls for a reconsideration of the generally accepted idea that the broader onshore eastern sector of the CR lacks significant basement and intrabasinal faults.

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Becker, T. "The petrogenesis of the Alberta Complex within the Rehoboth Basement Inlier of Namibia." South African Journal of Geology 105, no. 2 (June 1, 2002): 147–62. http://dx.doi.org/10.2113/105.2.147.

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Hicks, N., D. J. C. Gold, M. Ncume, and L. Hoyer. "A new lithostratigraphic framework and unified nomenclature for the Nsuze Group of the Nkandla sub-basin, southern Kaapvaal Craton, South Africa." South African Journal of Geology 124, no. 3 (September 1, 2021): 699–716. http://dx.doi.org/10.25131/sajg.124.0027.

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Abstract During the early 20th century the term Insuzi Series, later reclassified as the Nsuze Group of the Pongola Supergroup, was proposed for a volcano-sedimentary succession exposed in the upper Nsuze River valley in central KwaZulu-Natal, South Africa. Subsequently, however, there has been little consensus on lithostratigraphic frameworks within the type area, and limited correlation with the exceptionally well-defined stratigraphy within the main Pongola basin. Recent mapping, combined with newly acquired high-resolution aeromagnetic data, satellite imagery, and available published geochronological data suggest that previously published schemes within the Nkandla sub-basin require revision. Utilising important regional marker units, as well as the stratigraphic positions of distinct sedimentary facies within the otherwise volcanic Nsuze Group, a working model is proposed. Lithostratigraphic units are well represented in the Mhlatuze and Nkandla inliers with examples from these areas given prominence. Where exposed, potential correlates within the Nsuze nappe complex are discussed. Within the proposed scheme the siliciclastic Mantonga Formation forms the base of the Nsuze Group, nonconformably overlying basement granitoids of the Kaapvaal Craton within the Mhaltuze Inlier. Mafic volcanics of the Nhlebela Formation overlie the Mantonga Formation in the inlier. These two lower units are, however, not exposed elsewhere in the sub-basin. The sedimentary White Mfolozi Formation forms the base of the succession in the Nkandla Inlier. Diamictites and stromatolite-bearing carbonate lithologies unique to this unit are utilised for regional third-order correlations with the type-area in the White Mfolozi Inlier. Mafic volcanics of the Agatha Formation overlie the White Mfolozi Formation in all exposures, but are most extensively developed within the Mdlelanga syncline of the Nkandla Inlier. Sedimentary and volcaniclastic lithologies of the Mkuzane Formation cap the Nsuze Group in the Mhlatuze and Nkandla inliers. Thickness of this formation is, however, highly variable having been subjected to pre-Vutshini Formation erosion. Through detailed reinterpretation of the stratigraphy of the Nkandla sub-basin we present a third order, (formation) scale, lithostratigraphic scheme encompassing all the formational units of the currently accepted stratigraphy within the main Pongola basin. This working model has the potential for lower-ranking units to be identified and be placed at their appropriate stratigraphic levels in future.

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Hofmann, A., H. Xie, L. Saha, and C. Reinke. "Granitoids and greenstones of the White Mfolozi Inlier, south-east Kaapvaal Craton." South African Journal of Geology 123, no. 3 (September 1, 2020): 263–76. http://dx.doi.org/10.25131/sajg.123.0019.

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Abstract A Palaeoarchaean greenstone fragment and associated granitoid gneisses from an area south of Ulundi in KwaZulu-Natal is described. The fragment consists of an association of garnetiferous amphibolite and calc-silicate that was intruded at 3388 ± 4 Ma by tonalite and at 3275 ± 4 Ma by trondhjemite. Strong ductile deformation of the greenstones and granitoids under amphibolite facies conditions (7 kbar and 600 to 650°C) took place prior to uplift and emplacement of a granite batholith at ~3.25 Ga ago in which the granitoid gneiss-greenstone domain is now found. Magmatism 3.27 to 3.25 Ga ago was a direct response to regional metamorphism and anataxis, and gave rise to stabilization of the southeastern Kaapvaal Craton at that time, earlier than other parts of the craton. Deposition of quartz-arenites on stable granitic basement took place <3.1 Ga ago. Contrasting ages in magmatic pulses and regional metamorphism reflect a different crustal growth history of the eastern and southeastern part of the Kaapvaal Craton.

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McConachie, B. A., M. G. Barlow, J. N. Dunster, R. A. Meaney, and A. O. Schaap. "THE MOUNT ISA BASIN—DEFINITION, STRUCTURE AND PETROLEUM GEOLOGY." APPEA Journal 33, no. 1 (1993): 237. http://dx.doi.org/10.1071/aj92018.

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The Mount Isa Basin is a new concept to describe the area of Palaeo- to Mesoproterozoic rocks south of the Murphy Inlier (not the Murphy Tectonic Ridge) and inappropriately described as the Mount Isa Inlier. The new basin concept presented in this paper allows the characterisation of basin-wide structural deformation and the recognition of areas with petroleum exploration potential.The northern depositional margin of the Mount Isa Basin is the metamorphic, intrusive and volcanic complex referred to as the Murphy Inlier. The eastern, southern and western boundaries of the basin are obscured by younger basins (Carpentaria, Eromanga and Georgina Basins). The Murphy Inlier rocks comprise the seismic basement to the Mount Isa Basin sequence. Evidence for the continuity of the Mount Isa Basin with the McArthur Basin to the northwest and the Willyama Block (Basin) at Broken Hill to the south is presented. These areas combined with several other areas of similar age are believed to have comprised the Carpentarian Superbasin.The application of seismic exploration within Authority to Prospect (ATP) 423P at the northern margin of the basin was critical to the recognition and definition of the Mount Isa Basin. The northern Mount Isa Basin is structurally analogous to the Palaeozoic Arkoma Basin of Oklahoma and Arkansas in the southern USA but as with all basins it contains unique characteristics, a function of its individual development history. The northern Mount Isa Basin is defined as the basin area northwest of the Mount Gordon Fault.

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Oummouch, Abdellah, Abderrahim Essaifi, Rachid Zayane, Othmane Maddi, Mohamed Zouhair, and Lhou Maacha. "Geology and Metallogenesis of the Sediment-Hosted Cu-Ag Deposit of Tizert (Igherm Inlier, Anti-Atlas Copperbelt, Morocco)." Geofluids 2017 (November 15, 2017): 1–19. http://dx.doi.org/10.1155/2017/7508484.

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The Tizert Cu-Ag deposit is the largest of a series of sediment-hosted copper deposits of the Anti-Atlas copper province in Morocco. Mineralized rocks in the deposit contain disseminated sulphides within a Late Ediacaran, dominantly siliciclastic sedimentary formation named the Basal Series. Isopach map of the Basal Series thickness shows that during the Late Ediacaran the area was composed of large subsiding zones separated by paleohighs. The ore-grade zones are well developed along basin margins adjacent to the basement paleohighs. These mineralized zones display a lateral sulphide zoning with central bornite-chalcocite zones grading outward to intermediate chalcopyrite and external pyrite zones. There is also a vertical sulphide zoning with evolution from bornite and chalcocite dominant mineralized rocks at the bottom to chalcopyrite and pyrite dominant mineralized rocks at the top of the lithostratigraphic succession. A second style of mineralization is represented by sulphide filled fractures and veins present in the Basal Series, as well as in the basement and the overlying dolomites. The similarity of the paragenetic sequences between the disseminated and the vein-hosted mineralization suggests that they may be related to the same mineralizing event, the disseminated style of mineralization being rapidly followed by the onset of the vein-style mineralization.

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Barr, Sandra M., Robert P. Raeside, and Otto van Breemen. "Grenvillian basement in the northern Cape Breton Highlands, Nova Scotia." Canadian Journal of Earth Sciences 24, no. 5 (May 1, 1987): 992–97. http://dx.doi.org/10.1139/e87-096.

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The northernmost Cape Breton Highlands are underlain by the Blair River Complex, a distinctive assemblage of basement rocks including felsic and mafic gneisses, foliated gabbroic to granitic rocks, anorthosite, and foliated and unfoliated varieties of syenite. Major faults and mylonite zones separate the complex from schists, gneisses, and granitoid rocks typical of the rest of the Cape Breton Highlands. U–Pb dating of zircon from the Lowland Brook syenite of the Blair River Complex indicates a metamorphic age of [Formula: see text] and an igneous age of 1100–1500 Ma. These ages and the distinctive rock assemblage allow the Blair River Complex to be correlated with the Grenvillian rocks in the Long Range Inlier and Indian Head Range Complex of western Newfoundland. This is the first confirmed report of Grenvillian basement in Cape Breton Island, and it places new constraints on correlations between Newfoundland and the northern mainland Appalachians.

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MILLER, ROBERT B. "The Mesozoic Rimrock Lake inlier, southern Washington Cascades: Implications for the basement to the Columbia Embayment." Geological Society of America Bulletin 101, no. 10 (October 1989): 1289–305. http://dx.doi.org/10.1130/0016-7606(1989)101<1289:tmrlis>2.3.co;2.

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van Schijndel, Valby, David H. Cornell, Dirk Frei, Siri Lene Simonsen, and Martin J. Whitehouse. "Crustal evolution of the Rehoboth Province from Archaean to Mesoproterozoic times: Insights from the Rehoboth Basement Inlier." Precambrian Research 240 (January 2014): 22–36. http://dx.doi.org/10.1016/j.precamres.2013.10.014.

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Guryanov, V. A., A. N. Didenko, A. Yu Peskov, G. V. Roganov, and V. A. Dymovich. "Early Precambrian granitoids of the Batomga inlier of the southeastern Siberian Platform basement: Age and geodynamic formation settings." Russian Journal of Pacific Geology 10, no. 3 (May 2016): 168–88. http://dx.doi.org/10.1134/s1819714016030039.

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STOREY, C. D., T. S. BREWER, and S. TEMPERLEY. "P–T conditions of Grenville-age eclogite facies metamorphism and amphibolite facies retrogression of the Glenelg–Attadale Inlier, NW Scotland." Geological Magazine 142, no. 5 (September 2005): 605–15. http://dx.doi.org/10.1017/s001675680500110x.

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Peak and retrograde P–T conditions of Grenville-age eclogites from the Glenelg–Attadale Inlier of the northwest Highlands of Scotland are presented. Peak conditions are estimated as c. 20 kbar and 750–780°C, in broad agreement with previous work. The eclogites subsequently followed a steep decompression path to c. 13 kbar and 650–700°C during amphibolite facies retrogression. Peak eclogite facies metamorphism occurred > 1080 Ma and retrogression at c. 995 Ma, suggesting fairly sluggish uplift rates of < 0.3 km/Ma and cooling rates of < 1.25°C/Ma, when compared with other parts of the Grenville orogeny and/or modern orogens. However, current poor constraints on the timing of peak metamorphism mean that these rates cannot be used to interpret the geodynamic evolution of this part of the orogen. The P–T–t data, together with petrology and the field relationships between the basement rocks of the Glenelg–Attadale Inlier and the overlying Moine Supergroup, mean that it is difficult to support the currently held view that an unconformable relationship exists between the two. It is suggested that more data are required in order to re-interpret the Neoproterozic tectonic evolution of the northwest Highlands of Scotland.

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Tucker, R. D., S. J. O'Brien, and B. H. O'Brien. "Age and implications of Early Ordovician (Arenig) plutonism in the type area of the Bay du Nord Group, Dunnage Zone, southern Newfoundland Appalachians." Canadian Journal of Earth Sciences 31, no. 2 (February 1, 1994): 351–57. http://dx.doi.org/10.1139/e94-032.

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In south Newfoundland, an extensive tract of metamorphosed Ordovician metavolcanic, metasedimentary, and granitoid rocks (Bay du Nord Group) lies north of a late Precambrian basement inlier of peri-Gondwanan affinity, separated from the latter by Silurian rocks. In the Bay du Nord Group type area, the metavolcanic and metasedimentary rocks were ductilely sheared and locally fault imbricated with metagabbro prior to emplacement of the Baggs Hill Granite, herein dated at 477.6 ± 1.8 Ma. Some of the volcano-sedimentary strata within this succession, however, contain foliated clasts of Baggs Hill Granite, and these strata must comprise a younger stratigraphic sequence which, in this area, is thrust northwestward over the older rocks.The pre-477.6 ± 1.8 Ma tectonic interleaving of the Dunnage Zone gabbro and stratified rocks is significantly earlier than the Llandovery (early Salinic) recumbent folding and thrusting of Middle Ordovician Exploits Subzone rocks in the east-central Hermitage Flexure. In both areas, the Dunnage Zone rocks were inhomogeneously thickened and tectonically telescoped north of a rigid block of late Precambrian peri-Gondwanan basement. The emplacement of the Baggs Hill Granite is coeval with intrusion of similar Ordovician granite into ophiolites obducted southeastward onto the Gondwanan margin during Arenigian (Penobscot) orogenesis.

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FLOWERDEW, M. J., D. M. CHEW, J. S. DALY, and I. L. MILLAR. "Hidden Archaean and Palaeoproterozoic crust in NW Ireland? Evidence from zircon Hf isotopic data from granitoid intrusions." Geological Magazine 146, no. 6 (September 7, 2009): 903–16. http://dx.doi.org/10.1017/s0016756809990227.

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AbstractThe presence of major crystalline basement provinces at depth in NW Ireland is inferred from in situ Hf isotope analysis of zircons from granitoid rocks that cut structurally overlying metasedimentary rocks. Granitoids in two of these units, the Slishwood Division and the Tyrone Central Inlier, contain complex zircons with core and rim structures. In both cases, cores have average ϵHf values that differ from the average ϵHf values of the rims at 470 Ma (the time of granitoid intrusion). The Hf data and similarity in U–Pb age between the inherited cores and detrital zircons from the host metasedimentary rocks suggests local contamination during intrusion rather than transport of the grains from the source region at depth. Rims from the Slishwood Division intrusions have average ϵHf470 values of −7.7, consistent with a derivation from juvenile Palaeoproterozoic crust, such as the Annagh Gneiss Complex or Rhinns Complex of NW Ireland, implying that the deep crust underlying the Slishwood Division is made of similar material. Rims from the Tyrone Central Inlier have extremely negative ϵHf470 values of approximately −39. This isotopic signature requires an Archaean source, suggesting rocks similar to the Lewisian Complex of Scotland, or sediment derived wholly from it, occurs at depth in NW Ireland.

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MILLER, B. V. "Petrology and Isotopic Composition of a Grenvillian Basement Fragment in the Northern Appalachian Orogen: Blair River Inlier, Nova Scotia, Canada." Journal of Petrology 41, no. 12 (December 1, 2000): 1777–804. http://dx.doi.org/10.1093/petrology/41.12.1777.

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D’Lemos, R. S., J. D. Inglis, and S. D. Samson. "A newly discovered orogenic event in Morocco: Neoproterozic ages for supposed Eburnean basement of the Bou Azzer inlier, Anti-Atlas Mountains." Precambrian Research 147, no. 1-2 (June 2006): 65–78. http://dx.doi.org/10.1016/j.precamres.2006.02.003.

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Valladares, Claudia Sayão, Beatriz Paschoal Duarte, Hugo Tavares Machado, Samuel Magalhães Viana, and Pedro Lontra Costa de Figueiredo. "Genesis and evolution of a Paleoproterozoic basement inlier within West Gondwana addressed by Sm-Nd isotopic geochemistry and Zr saturation thermometry." Journal of South American Earth Sciences 80 (December 2017): 95–106. http://dx.doi.org/10.1016/j.jsames.2017.09.005.

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Winchester, J. A., C. R. van Staal, and J. P. Langton. "The Ordovician volcanics of the Elmtree–Belledune inlier and their relationship to volcanics of the northern Miramichi Highlands, New Brunswick." Canadian Journal of Earth Sciences 29, no. 7 (July 1, 1992): 1430–47. http://dx.doi.org/10.1139/e92-115.

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An investigation of the geology and chemistry of the basic igneous rocks in the Elmtree and Belledune inliers in northern New Brunswick shows that the bulk of the Middle Ordovician rocks of the ophiolitic Fournier Group are best interpreted as the products of volcanism and sedimentation in an extensive ensimatic back-arc basin southeast of a volcanic arc. The oceanic back-arc-basin igneous rocks form the basement to renewed arc-related basaltic volcanism in late Middle to Late Ordovician time. The Fournier Group is separated from the structurally-underlying, shale-dominated Elmtree Formation of the Tetagouche Group by an extensive tectonic melange, which incorporates lenses of serpentinite, mafic volcanic rocks, and sedimentary rocks of both the Tetagouche and Fournier groups. The mafic volcanic rocks in the Elmtree Formation correlate best with those intercalated with the lithologically similar sediments of the Llandeilian–Caradocian Boucher Brook Formation in the northern Miramichi Highlands. The melange and the present structural amalgamation of the Tetagouche and Fournier groups result from closure of the marginal basin by northward-directed subduction at the end of the Ordovician. Most mafic suites in the Elmtree and Belledune inliers can be chemically correlated with similar suites in the northern Miramichi Highlands, showing that the two areas are not separated by a terrane boundary.

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Forsyth, D. A., B. Milkereit, C. A. Zelt, D. J. White, R. M. Easton, and D. R. Hutchinson. "Deep structure beneath Lake Ontario: crustal-scale Grenville subdivisions." Canadian Journal of Earth Sciences 31, no. 2 (February 1, 1994): 255–70. http://dx.doi.org/10.1139/e94-025.

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Lake Ontario marine seismic data reveal major Grenville crustal subdivisions beneath central and southern Lake Ontario separated by interpreted shear zones that extend to the lower crust. A shear zone bounded transition between the Elzevir and Frontenac terranes exposed north of Lake Ontario is linked to a seismically defined shear zone beneath central Lake Ontario by prominent aeromagnetic and gravity anomalies, easterly dipping wide-angle reflections, and fractures in Paleozoic strata. We suggest the central Lake Ontario zone represents crustal-scale deformation along an Elzevir–Frontenac boundary zone that extends from outcrop to the south shore of Lake Ontario.Seismic images from Lake Ontario and the exposed western Central Metasedimentary Belt are dominated by crustal-scale shear zones and reflection geometries featuring arcuate reflections truncated at their bases by apparent east-dipping linear reflections. The images show that zones analogous to the interpreted Grenville Front Tectonic Zone are also present within the Central Metasedimentary Belt and support models of northwest-directed crustal shortening for Grenvillian deep crustal deformation beneath most of southeastern Ontario.A Precambrian basement high, the Iroquoian high, is defined by a thinning of generally horizontal Paleozoic strata over a crestal area above the basement shear zone beneath central Lake Ontario. The Iroquoian high helps explain the peninsular extension into Lake Ontario forming Prince Edward County, the occurrence of Precambrian inlier outcrops in Prince Edward County, and Paleozoic fractures forming the Clarendon–Linden structure in New York.

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Becker, T. "The Mesoproterozoic event within the Rehoboth Basement Inlier of Namibia: review and new aspects of stratigraphy, geochemistry, structure and plate tectonic setting." South African Journal of Geology 108, no. 4 (December 1, 2005): 465–92. http://dx.doi.org/10.2113/108.4.465.

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Reinhardt, J., M. A. Elburg, and T. Andersen. "Zircon U-PB Age Data and HF Isotopic Signature of Kaapvaal Basement Granitoids from the Archaean White Mfolozi Inlier, Northern Kwazulu-Natal." South African Journal of Geology 118, no. 4 (December 2015): 473–88. http://dx.doi.org/10.2113/gssajg.118.4.473.

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Crawford, Brenton L., Peter G. Betts, and Laurent Aillères. "An aeromagnetic approach to revealing buried basement structures and their role in the Proterozoic evolution of the Wernecke Inlier, Yukon Territory, Canada." Tectonophysics 490, no. 1-2 (July 2010): 28–46. http://dx.doi.org/10.1016/j.tecto.2010.04.025.

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O'dea, Mark G., and Gordon S. Lister. "The role of ductility contrast and basement architecture in the structural evolution of the Crystal Creek block, Mount Isa Inlier, NW Queensland, Australia." Journal of Structural Geology 17, no. 7 (July 1995): 949–60. http://dx.doi.org/10.1016/0191-8141(94)00117-i.

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Emon, K. A., V. A. Jackson, and G. R. Dunning. "Geology and U-Pb geochronology of rocks of the Eokuk Uplift: a pre-2.8 Ga basement inlier in the northwestern Slave Province, Nunavut, Canada." Canadian Journal of Earth Sciences 36, no. 7 (July 1, 1999): 1061–82. http://dx.doi.org/10.1139/e98-094.

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Rocks of the Eokuk Uplift have been mapped in detail along the coast of Coronation Gulf and 10 key units have been dated by U-Pb analysis of zircon, monazite, and titanite. The combined data indicate that this inlier of the Slave Province has a >3.2 Ga crustal component, evidence of a granulite-grade orogenic event predating 2.8 Ga and a lack of evidence for any significant orogenic activity corresponding to the 2.7-2.6 Ga events common in the rest of the Slave Province. The oldest rocks in the study area are a succession of granitoid and supracrustal gneisses that have been metamorphosed to amphibolite to granulite facies. From field relationships, the oldest rock is a granodiorite to tonalite orthogneiss, with a zircon crystallization age of 3254+13-6 Ma. A granite gneiss, which may be a small felsic intrusion or an anatectic melt of the tonalite gneiss, yields a zircon age of 3216+14-13 Ma. A K-feldspar megacrystic monzogranite gneiss contains old, discordant, possibly inherited zircons with 207Pb/206Pb ages ranging from 3103 to 3039 Ma, together with coexisting 2879 ± 3 Ma zircon and monazite. These high-grade gneisses are intruded by two megacrystic granite plutons, dated at 2887 ± 2 and 2881+4-3 Ma. The absence of extensive recrystallization and complex structures in these plutons indicates that this igneous event postdated the high-grade metamorphism. An amphibolite-grade synplutonic metamorphic event is dated at ~2880 Ma by new monazite in the older gneiss units. A series of variably deformed mafic to felsic dykes and pegmatites intrude both the granites and gneisses and constrain the end of penetrative deformation in the area. Of these, a boudinaged diorite dyke, with a strong internal foliation parallel to the regional fabric, is dated at 2877 ± 3 Ma. A younger granodiorite dyke that crosscuts the regional fabric at a high angle and has only a weak internal foliation yields an age of 2864+3-9 Ma. An undeformed syenogranite pegmatite, which represents a suite that intrudes all other units in the study area, has a combined zircon-monazite age of 2852 ± 3 Ma. The varying degrees of deformation in these minor intrusive rocks constrains the end of deformation in the study area to ca. 2850 Ma. This contrasts with data from the rest of the Slave Province, where the main phases of deformation, metamorphism, and synmetamorphic plutonism have been dated at ca. 2.62-2.59 Ga. Metamorphic titanite ages from the diorite and granodiorite dykes indicate two lower amphibolite to greenschist facies metamorphic events: one at ca. 2705 Ma and one at ca. 2646 Ma. The youngest Archean magmatic event in the area is represented by granite intrusions at 2594+3-2 Ma, coeval with crystallization of titanite at greenschist-grade conditions in some of the older gneissic and intrusive rocks.

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Grochowski, Julia, Matheus Kuchenbecker, Danilo Barbuena, and Tiago Novo. "Disclosing Rhyacian/Orosirian orogenic magmatism within the Guanhães basement inlier, Araçuaí Orogen, Brazil: A new piece on the assembly of the São Francisco-Congo paleocontinent." Precambrian Research 363 (September 2021): 106329. http://dx.doi.org/10.1016/j.precamres.2021.106329.

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Ballivián Justiniano, Carlos A., Miguel A. S. Basei, Ana M. Sato, Pablo D. González, Manuela E. Benítez, and Mabel E. Lanfranchini. "The Neoproterozoic basement of the Sauce Chico Inlier (Ventania System): Geochemistry and U–Pb geochronology of igneous rocks with African lineage in central-eastern Argentina." Journal of South American Earth Sciences 98 (March 2020): 102391. http://dx.doi.org/10.1016/j.jsames.2019.102391.

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El Janati, M’hamed, Abderrahmane Soulaimani, Hassan Admou, Nasrrddine Youbi, Ahmid Hafid, and Kevin Patrick Hefferan. "Application of ASTER remote sensing data to geological mapping of basement domains in arid regions: a case study from the Central Anti-Atlas, Iguerda inlier, Morocco." Arabian Journal of Geosciences 7, no. 6 (May 16, 2013): 2407–22. http://dx.doi.org/10.1007/s12517-013-0945-y.

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Benjmel, Khalid, Fouad Amraoui, Ali Aydda, Amine Tahiri, Mohamed Yousif, Biswajeet Pradhan, Kamal Abdelrahman, Mohammed S. Fnais, and Mohamed Abioui. "A Multidisciplinary Approach for Groundwater Potential Mapping in a Fractured Semi-Arid Terrain (Kerdous Inlier, Western Anti-Atlas, Morocco)." Water 14, no. 10 (May 12, 2022): 1553. http://dx.doi.org/10.3390/w14101553.

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This study is focused on developing an approach for spatial mapping of groundwater by considering four types of factors (geological, topographical, hydrological, and climatic factors), and by using different bivariate statistical models, such as frequency ratio (FR) and Shannon’s entropy (SE). The developed approach was applied in a fractured aquifer basin (Ameln Basin, Western Anti-Atlas, Morocco), to map the spatial variation of groundwater potential. Fifteen factors (15) influencing groundwater were considered in this study, including slope degree, slope aspect, elevation, topographic wetness index (TWI), slope length (LS), topographic position index (TPI), plane curvature, profile curvature, drainage density, lineament density, distance to rivers and fault network, normalized difference vegetation index (NDVI), lithology, and land surface temperature (LST). The potential maps produced were then classified into five classes to illustrate the spatial view of each potential class obtained. The predictive capacity of the frequency ratio and Shannon’s entropy models was determined using two different methods, the first one based on the use of flow data from 49 boreholes drilled in the study area, to test and statistically calibrate the predictive capacity of each model. The results show that the percentage of positive water points corresponds to the most productive areas (high water flow) (42.86% and 30.61% for the FR and SE models, respectively). On the other hand, the low water flows are consistent with the predicted unfavorable areas for hydrogeological prospecting (4.08% for the FR model and 6.12% for the SE model). Additionally, the second validation method involves the integration of 7200 Hz apparent resistivity data to identify conductive zones that are groundwater circulation zones. The interpretation of the geophysical results shows that the high-potential zones match with low apparent resistivity zones, and therefore promising targets for hydrogeological investigation. The FR and SE models have proved very efficient for hydrogeological mapping at a fractured basement area and suggest that the northern and southern part of the study area, specifically the two major fault zones (Ameln Valley in the north, and the Tighmi-Tifermit Valley in the south) has an adequate availability of groundwater, whereas the central part, covering the localities of Tarçouat, Boutabi, Tililan, and Ighalen, presents a scarcity of groundwater. The trend histogram of the evolution of positive water points according to each potentiality class obtained suggests that the FR model was more accurate than the SE model in predicting the potential groundwater areas. The results suggest that the proposed approach is very important for hydrogeological mapping of fractured aquifers, and the resulting maps can be helpful to managers and planners to generate groundwater development plans and attenuate the consequences of future drought.

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RING, UWE, ARNE P. WILLNER, PAUL W. LAYER, and PETER P. RICHTER. "Jurassic to Early Cretaceous postaccretional sinistral transpression in north-central Chile (latitudes 31–32°S)." Geological Magazine 149, no. 2 (August 16, 2011): 208–20. http://dx.doi.org/10.1017/s0016756811000653.

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AbstractWe describe the geometry and kinematics of a Jurassic to Early Cretaceous transpressive sinistral strike-slip system within a metamorphic basement inlier of the Mesozoic magmatic arc near Bahia Agua Dulce at latitudes 31–32°S in north-central Chile and discuss possible relations with the Atacama Fault System further north. Sinistral transpression overprints structures of an accretionary system that is represented by the metamorphic basement. Sub-vertical semi-ductile NNW-striking strike-slip shear zones are the most conspicuous structures. Chlorite and sericite grew, and white mica and quartz dynamically recrystallized, suggesting low-grade metamorphic conditions during semi-ductile deformation. Folds at the 10–100 metre scale developed before and during strike-slip shearing. The folds are deforming a former sub-horizontal transposition foliation that originated during prior accretion processes. The folds have axes sub-parallel to the strike-slip shear zones and sub-vertical axial surfaces indicating a component of shortening parallel to the shear-zone boundaries, suggesting an overall transpressive deformation regime. Transpressive strike-slip deformation also affects Middle Triassic (Anisian) basal breccias of the El Quereo Formation.40Ar–39Ar laser ablation ages of synkinematically recrystallized white mica in one of the shear zones provide an age of 174–165 Ma for the waning stages of semi-ductile strike-slip shearing. The semi-ductile shear zones are cut by mafic and rhyolite dykes. Two rhyolite dykes yield40Ar–39Ar ages of 160.5 ± 1.7 Ma and 131.9 ± 1.7 Ma, respectively. The latter dyke has been affected by brittle faulting. Fault-slip analysis shows that the kinematics of the faulting event is similar to the one of the semi-ductile shearing event, suggesting that sinistral transpression continued after ~130 Ma. Timing, kinematics and geographic position suggest that the shear zones at Bahia Agua Dulce represent a southern continuation of the prominent Atacama Fault System that affected the Jurassic/Early Cretaceous arc over its ~1400 km length.

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BIERLEIN, F., L. BLACK, J. HERGT, and G. MARK. "Evolution of Pre-1.8Ga basement rocks in the western Mt Isa Inlier, northeastern Australia—Insights from SHRIMP U–Pb dating and in-situ Lu–Hf analysis of zircons." Precambrian Research 163, no. 1-2 (May 20, 2008): 159–73. http://dx.doi.org/10.1016/j.precamres.2007.08.017.

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35

Ousaid, Lahcen, Youssef Hahou, Hassan Admou, El Moustafa Mouguina, Khadija Diani, Rachid Ziadi, Zineb Aafir, Said Courba, and Aziza Lamchaimech. "The Cu-Ag-Pb Polymetallic Mineralization of Agdim-Ait Elfersi Sector, North-Eastern Part of the Saghro Massif, Morocco: Geological Setting, Ore Petrography and Geochemistry." Iraqi Geological Journal 55, no. 1A (January 31, 2022): 1–20. http://dx.doi.org/10.46717/igj.55.1a.1ms-2022-01-20.

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The Cu-Ag-Pb polymetallic mineralization of the Agdim-Ait Elfersi sector is situated in the eastern Anti Atlas Moroccan belt, the northeastern part of the Saghro inlier. The mineralization is hosted in the volcanic rocks of late Neoproterozoic and the detrital sedimentary rocks of the Lower Cambrian. A network of faults has affected this area; it is a brutalizing deformation with NW-SE, NE-SW, E-W, and NNE-SSW directions. NW-SE and NE-SW structures have a metallogenic significance. This tectonic canvas was used as a target of a mineralization vein with Cu, Ag, and Pb in this area. By combining geological, structural, and metallogenic characteristics, it can be assumed that the Cu-Ag-Pb mineralization of the Agdim-Ait Elfersi sector is linked to two major events. A late Pan-African event linked to the extensional tectonics of the late Neoproterozoic, responsible for the establishment of mineralization at the level of the basement, and then a late Hercynian-Atlasic event, which manifests by the remobilization of metals in NE-SW oriented structures. Geochemical analysis shows the polymetallic character of this mineralization. The high contents of silver and mercury observed indicate the presence of similarities of an Ag-Hg epithermal type of mineralization in this area. Geological context, as well as mineralogical and textural characters of the Agdim-Ait Elfersi sector are reminiscent of epithermal-type mineralization as in the Imiter and Zgounder deposit.

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Carr, Lidena, Russell Korsch, Wolfgang Preiss, Sandra Menpes, Josef Holzschuh, and Ross Costelloe. "Structural and stratigraphic architecture of Australia's frontier onshore sedimentary basins: the Arckaringa, Officer, Amadeus, and Georgina basins." APPEA Journal 51, no. 2 (2011): 703. http://dx.doi.org/10.1071/aj10083.

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The Onshore Energy Security Program—funded by the Australian Government and conducted by Geoscience Australia—has acquired deep seismic reflection data in conjunction with state and territory geological surveys, across several frontier sedimentary basins to stimulate petroleum exploration in onshore Australia. Here, we present data from two seismic lines collected in SA and NT. Seismic line 08GA-OM1 crossed the Arckaringa and Officer basins in SA and the southern-most Amadeus Basin in NT. Seismic line 09GA-GA1 crossed the northeastern part of the Amadeus Basin and the complete width of the southern Georgina Basin in NT. Structural and sequence stratigraphic interpretations of the seismic lines will be presented here, followed by an assessment of the petroleum potential of the basins. Seismic line 08GA-OM1 also crosses the Neoproterozoic to Devonian eastern Officer Basin. The basin is structurally complex in this area, being dominated by south-directed thrust faults and fault-related folds—providing potential for underthrust petroleum plays. The northern margin of the basin is overthrust to the south by the Mesoproterozoic Musgrave Province. To the north, the Moorilyanna Trough of the Officer Basin is a major depocentre of up to 7,000 m deep. Both seismic lines cross parts of the eastern Amadeus Basin. Seismic line 08GA-OM1 shows that the southern margin of the basin is overthrust to the north by the Musgrave Province with the main movement during the Petermann Orogeny. In the northeast, seismic line 09GA-GA1 crosses two parts of the basin separated by the Paleoproteroozic to Mesoproterozoic Casey Inlier (part of the Arunta Region). The northern margin of the basin is imaged seismically as a southward-verging, thinned-skinned thrust belt, showing considerable structural thickening of the stratigraphic succession. Seismic line 09GA-GA1 was positioned to cross that part of the southern Georgina Basin that was considered previously to be in the oil window. Here, the basin has a complex southern margin, with Neoproterozoic stratigraphy being thrust interleaved with basement rocks of the Arunta Region. The main part of the basin, containing a Neoproterozoic to Devonian succession, is asymmetric, thinning to the north where it overlies the Paleoproterozoic Davenport Province. The well, Phillip–2, drilled adjacent to the seismic line, intersected basement at a depth of 1,489 m, and has been used to map the stratigraphic sequences across the basin.

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HERBOSCH, Alain. "Stratigraphic correlations between the Brabant Massif and the Stavelot, Rocroi and Givonne inliers (Belgium) and geological implications." Geologica Belgica 24, no. 3-4 (November 26, 2021): 137–57. http://dx.doi.org/10.20341/gb.2021.004.

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The Caledonian basement crops out in the middle and southern part of Belgium in two major tectonic units: the Brabant Massif in the Brabant Parautochthon and the Stavelot-Venn, Rocroi, Givonne and Serpont inliers in the Ardenne Allochthon. The main aim of this work is to achieve a chronostratigraphic correlation between the Brabant Massif and the Ardenne inliers, from the lower Cambrian to the Middle Ordovician. Throughout his career, Michel Vanguestaine established an informal acritarch biozonation for this basement, which is only linked to the international stratigraphic scale in vigour at that time. Our first step was to correlate these informal biozones with the trilobite (Cambrian) and graptolite (Ordovician) biozonations which are currently well correlated with the chronostratigraphy. Then, compilation of the literature concerning each of these sedimentary units makes it possible to assign a chronostratigraphic position to their constituent formations. This work has permitted the establishment of a complete chart of the stratigraphic correlations between the Brabant Massif and the three main Ardenne inliers (Stavelot-Venn, Rocroi and Givonne). Geological implications are discussed: the Brabant Massif and the Ardenne inliers formed a single sedimentation basin with different and rheologically contrasting basements (rift and shoulder). New arguments confirm the presence of a Caledonian orogeny in the Ardenne.

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38

Brugger, J., J. Ogierman, A. Pring, H. Waldron, and U. Kolitsch. "Origin of the secondary REE-minerals at the Paratoo copper deposit near Yunta, South Australia." Mineralogical Magazine 70, no. 6 (December 2006): 609–27. http://dx.doi.org/10.1180/0026461067060361.

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AbstractThe Paratoo copper deposit, located in the Neoproterozoic to Cambrian Adelaide Geosyncline, South Australia, produced around 360 tons of Cu between 1888 and 1967 from oxidized ores. The deposit is located in the core of a breached, doubly plunging anticline, near a zone of disruption containing brecciated Adelaidean sedimentary rocks and dolerite (‘Paratoo Diapir’), and hosted in dolomitic shales of the Neoproterozoic Burra Formation. Near the surface, the mineralization resides mainly in deeply weathered quartz-magnetite-sulphide (pyrite, chalcopyrite) veins (⩽10 cm wide). At depth, drill cores reveal disseminated magnetite, pyrite, chalcopyrite, copper sulphide and native copper associated with extensive potassic alteration. K-Na-rich fluids also affected the dolerite in the ‘Paratoo diapir’, resulting in the precipitation of K-feldspar, dravite and K-bearing chabazite-Na. The most likely scenario for the genesis of the Paratoo deposit involves circulation of basinal fluids, focusing into the ‘Paratoo Diapir’, and ore precipitation through neutralization by fluid-rock interaction with the dolomitic shales hosting the mineralization.The Paratoo deposit is deeply weathered, with malachite and chrysocolla (± tenorite and cuprite) containing the bulk of the copper recovered from the shallow workings. A diverse assemblage of secondary REE-bearing carbonate minerals, including the new species decrespignyite-(Y) and paratooite-(La), is associated with the weathered base metal and magnetite ores. Whole-rock geochemical analyses of fresh and mineralized host rock and of vein material reveals that the mineralization is associated with a strong, albeit highly variable, enrichment in light rare earth elements (LREE). This association indicates that REE and base metals were introduced by the same hydrothermal fluid. The strong negative Ce anomaly found in secondary REE minerals and mineralized rock samples suggests an upgrade of the REE contents in the weathering zone, insoluble Ce4+ being left behind.The Fe-oxide-REE-base metal association at Paratoo is also characteristic of the giant Mesoproterozoic Fe oxide copper gold deposit of Olympic Dam, located 350 km to the NW. A similar association is found in the Palaeozoic deposits of the Mt Painter Inlier, 300 km to the NNE. The widespread occurrence of this elemental association in the Province probably reflects the geochemistry of the basement, which contains numerous Mesoproterozoic granites enriched in REE and U.

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Brito Neves, Benjamim Bley de, Reinhardt A. Fuck, and Ginaldo Ademar da Cruz Campanha. "Basement inliers of the Brasiliano structural provinces of South America." Journal of South American Earth Sciences 110 (October 2021): 103392. http://dx.doi.org/10.1016/j.jsames.2021.103392.

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40

Strachan, R. A., T. E. Johnson, C. L. Kirkland, P. D. Kinny, and T. Kusky. "A Baltic heritage in Scotland: Basement terrane transfer during the Grenvillian orogeny." Geology 48, no. 11 (July 21, 2020): 1094–98. http://dx.doi.org/10.1130/g47615.1.

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Abstract Archean basement inliers within the Northern Highland terrane (NHT), Scottish Caledonides, have been correlated with the Lewisian Gneiss Complex of the Laurentian foreland. New zircon U-Pb ages indicate that the NHT basement contains evidence for magmatism at 2823–2687 Ma and 1772–1655 Ma. The first group compares with crystallization ages of the foreland Archean gneisses. However, the second group, and a supracrustal unit, formed ∼100–250 m.y. after the youngest major phase of juvenile magmatism and sedimentation in the foreland. Also, there is no indication within the NHT basement of the Paleoproterozoic mafic and felsic intrusions common within the foreland, leading us to conclude that there is no firm basis for correlation of the two crustal blocks. The Caledonian Moine thrust, which separates the foreland and the NHT basement, is thought to have reworked a Grenvillian suture indicated by the presence of the ca. 1100–1000 Ma Eastern Glenelg eclogites. On the basis of the new isotopic data, we propose that the NHT basement was a fragment of Baltica that was emplaced onto Laurentia during the Grenvillian orogeny, representing a further example of basement terrane transfer in the circum–North Atlantic orogens.

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Sibila Borojević, Šoštarić, Neubauer Franz, Handler Robert, and Palinkaš Ladislav A. "Tectonothermal history of the basement rocks within the NW Dinarides: new40 Ar/39 Ar ages and synthesis." Geologica Carpathica 63, no. 6 (December 1, 2012): 441–52. http://dx.doi.org/10.2478/v10096-012-0034-2.

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Abstract Very low-grade and low-grade metamorphosed basement rocks from distinct inliers of the Africa-derived northwestern Dinarides (Medvednica Mts and Paleozoic Sana-Una Unit, respectively) have been studied with the multigrain step-heating 40Ar/39Ar technique in order to compare and reveal their tectonothermal history. 40Ar/39Ar ages from detrital white mica of the very low-grade basement rocks of the Paleozoic Sana-Una Unit gave a Variscan age of ~335 Ma. The new age is in agreement with 40Ar/39Ar ages from the very low-grade basement exposed at Petrova and Trgovska Gora of the NW Dinarides. Within low-grade metamorphic basement rocks from the Medvednica Mts, we found no Variscan ages. White mica from phyllitic basement rocks of the Medvednica Mts gives predominantly early Alpine ages ranging between 135 and 122 Ma and younger Alpine ages of ~80 Ma. The early Alpine ages of 135 and 122 Ma are interpreted as the date to the onset of ductile nappe stacking predating the formation of Gosau-type collapse basins. The late early Alpine event of ~80 Ma can be traced in the entire Cretaceous-aged orogen of the Circum- Pannonian Region and is synchronous with subsidence of the Gosau-type basins and opening and closure of the neighbouring Sava-Vardar Zone.

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42

Riley, T. R., M. J. Flowerdew, and M. J. Whitehouse. "U–Pb ion-microprobe zircon geochronology from the basement inliers of eastern Graham Land, Antarctic Peninsula." Journal of the Geological Society 169, no. 4 (July 2012): 381–93. http://dx.doi.org/10.1144/0016-76492011-142.

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43

Martin, Erin L., William J. Collins, and Christopher J. Spencer. "Laurentian origin of the Cuyania suspect terrane, western Argentina, confirmed by Hf isotopes in zircon." GSA Bulletin 132, no. 1-2 (June 12, 2019): 273–90. http://dx.doi.org/10.1130/b35150.1.

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Abstract The proto-Andean margin of Argentina consists of several suspect terranes, the origins of which are disputed. The Cuyania (greater Precordillera) suspect terrane was originally interpreted to be of southeast Laurentian affinity, but more recently a southwestern Gondwanan provenance has been argued. Both potential source regions comprise Mesoproterozoic rocks, but we show they are isotopically distinct, using previously published zircon Lu-Hf data. Detrital zircon εHf data from southwestern Gondwana (Namaqua-Natal belt) show no correlation with new zircon U-Pb and Lu-Hf data from Cuyania, suggesting that Gondwana was not the source of these sediments. Rather, detrital zircons from Cambrian strata in Cuyania yield Mesoproterozoic zircons with depleted εHf that correlate to the Grenville margin of Laurentia, and a ca. 535 Ma zircon population sourced directly from rift-related rocks of the Ouachita Embayment, thus recording rifting and drifting of Cuyania from Laurentia. By contrast, zircons from Middle to Late Ordovician strata of Cuyania record a larger range of εHf values, correlated with Western Sierras Pampeanas Mesoproterozoic basement inliers of Argentina. These synorogenic clastic deposits record the Ordovician arrival of Cuyania at the proto-Andean margin of Gondwana. The new data require the terrane boundaries of Cuyania to be redefined, thereby excluding Western Sierras Pampeanas basement inliers. The results verify the Laurentian microcontinent model for the origin of Cuyania.

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Goscombe, B., R. Armstrong, and J. M. Barton. "Tectonometamorphic Evolution of the Chewore Inliers: Partial Re-equilibration of High-grade Basement during the Pan-African Orogeny." Journal of Petrology 39, no. 7 (July 1, 1998): 1347–84. http://dx.doi.org/10.1093/petroj/39.7.1347.

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45

Cordani, U. G., A. Cardona, D. M. Jimenez, D. Liu, and A. P. Nutman. "Geochronology of Proterozoic basement inliers in the Colombian Andes: tectonic history of remnants of a fragmented Grenville belt." Geological Society, London, Special Publications 246, no. 1 (2005): 329–46. http://dx.doi.org/10.1144/gsl.sp.2005.246.01.13.

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FRIEND, C. R. L., R. A. STRACHAN, and P. D. KINNY. "U–Pb zircon dating of basement inliers within the Moine Supergroup, Scottish Caledonides: implications of Archaean protolith ages." Journal of the Geological Society 165, no. 4 (July 2008): 807–15. http://dx.doi.org/10.1144/0016-76492007-125.

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47

Friderichsen, J. D., R. E. Holdsworth, H. F. Jepsen, and R. A. Strachan. "Caledonian and pre-Caledonian geology of Dronning Louise Land, North-East Greenland." Rapport Grønlands Geologiske Undersøgelse 148 (January 1, 1990): 133–41. http://dx.doi.org/10.34194/rapggu.v148.8133.

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The western border of the East Greenland Caledonides is exposed in Dronning Louise Land, where it is marked by a N–S trending thrust Imbricate Zone. The autochthonous crystalline basement to the west of the Imbricate Zone is dominated by orthogneisses, and unconformably overlain by two metasedimentary sequences (Zebra Series and Trekant Series). These metasedimentary units can be recognised in the Caledonian thrust slices of the Imbricate Zone and also as folded inliers in the gneiss complexes to the east, and witness to a progressive increase in Caledonian deformation and metamorphism.

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Machado, N., N. Goulet, and C. Gariépy. "U–Pb geochronology of reactivated Archean basement and of Hudsonian metamorphism in the northern Labrador Trough." Canadian Journal of Earth Sciences 26, no. 1 (January 1, 1989): 1–15. http://dx.doi.org/10.1139/e89-001.

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The Labrador Trough is a Proterozoic orogenic belt bordering the eastern margin of the Archean Superior Province. The volcano-sedimentary sequences of the trough were deformed and metamorphosed during the Hudsonian Orogeny (ca. 1800 Ma). The eastern basement, present as domal inliers, was remobilized during this orogeny, whereas the western basement remained unaffected.In this study we present U–Pb ages of the western and eastern basement of the Proterozoic Labrador Trough orogen between Leaf River and Koksoak River and of the northernmost extension of the DePas batholithic complex farther east. From the western basement, the Leaf Bay granodiorite has an age of 2721 ± 3 Ma (zircon). From the gneiss domes of the eastern basement the ages are as follows: Lac Moyer—2883 ± 6 Ma (zircon), 1793 ± 5 Ma (monazite), and 1746 Ma (minimum age, rutile); Lac Boulder—an upper-intercept age of 2868 ± 8 Ma and a lower-intercept age of 1783 ± 11 Ma (zircon–titanite regression) and an age of 1740 ± 5 Ma (rutile); Lac Olmstead Lake—2721 ± 4 Ma (zircon) and 1774 ± 5 Ma (titanite); Leaf Strait—2719 ± 7 Ma (zircon) and 1783 ± 2 Ma (monazite). The DePas Batholith contains four generations of zircon: the minimum ages of the three oldest are 2688, 2779, and 2922 Ma; we also obtained a monazite age of 1808 ± 2 Ma.These results lead us to the following conclusions: (i) The age of the Leaf Bay granodiorite, 2721 ± 3 Ma, is a minimum age of the gneisses of the Minto Subprovince, (ii) The westernmost gneiss domes of the eastern basement (Lac Moyer and Lac Boulder), bounded by two major faults, contain zircon formed during metamorphic events dated at 2868 ± 8 and 2883 ± 6 Ma and may be part of an allochthon. (iii) The Lac Olmstead and Leaf Strait domes contain metamorphic zircon dated at 2719–2721 Ma. (iv) The minimum age of migmatization of the DePas complex is 2688 Ma. (v) The monazite ages date the latest phase of metamorphism in the area, (vi) The titanite ages probably represent post-deformational cooling, whereas the rutile ages could represent late-metamorphic hydrothermal activity, (vi) The available data suggest the presence of continuous Archean basement—remobilized during the Hudsonian Orogeny—between the Labrador Trough and the DePas Batholith, which could represent a collision zone. The final stages of this collision could be slightly older (1808 Ma) than the equivalent activity in the Labrador Trough. These speculations raise the possibility that the evolution of the Labrador Trough is closely related in time and space to events occurring in its "hinterland".

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49

Doig, Ronald. "Rb–Sr geochronology and metamorphic history of Proterozoic to early Archean rocks north of the Cape Smith Fold Belt, Quebec." Canadian Journal of Earth Sciences 24, no. 4 (April 1, 1987): 813–25. http://dx.doi.org/10.1139/e87-079.

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The Churchill Province north of the Proterozoic Cape Smith volcanic fold belt of Quebec may be divided into two parts. The first is a broad antiform of migmatitic gneisses (Deception gneisses) extending north from the fold belt ~50 km to Sugluk Inlet. The second is a 20 km wide zone of high-grade metasedimentary rocks northwest of Sugluk Inlet. The Deception gneisses yield Rb–Sr isochron ages of 2600–2900 Ma and initial ratios of 0.701–0.703, showing that they are Archean basement to the Cape Smith Belt. The evidence that the basement rocks have been isoclinally refolded in the Proterozoic is clear at the contact with the fold belt. However, the gneisses also contain ubiquitous synclinal keels of metasiltstone with minor metapelite and marble that give isochron ages less than 2150 Ma. These ages, combined with low initial ratios of 0.7036, show that they are not part of the basement, as the average 87Sr/86Sr ratio for the basement rocks was about 0.718 at that time.The rocks west of Sugluk Inlet consist mainly of quartzo-feldspathic sediments, quartzites, para-amphibolites, marbles, and some pelite and iron formation. In contrast to the Proterozoic sediments in the Deception gneisses, these rocks yield dates of 3000–3200 Ma, with high initial ratios of 0.707–0.714. These initial ratios point to an age (or a provenance) much greater than that of the Archean Deception gneisses. The rocks of the Sugluk terrain are intruded by highly deformed sills of granitic rocks with ages of about 1830 Ma, demonstrating again the extent and severity of the Proterozoic overprint. The eastern margin of this possibly early Archean Sugluk block is a discontinuity in age, lithology, and geophysical character that could be a suture between two Archean cratons. It is not known if such a suturing event is of Archean age, or if it is related to the deformation of the Cape Smith Fold Belt.Models of evolution incorporating both the Cape Smith Belt and the Archean rocks to the north need to account for the internal structure of the fold belt, the continental affinity of many of the volcanic rocks, the continuity of basement around the eastern end of the belt, and the increase in metamorphism through the northern part of the belt into a broad area to the north. The Cape Smith volcanic rocks may have been extruded along a continental rift, parallel to a continental margin at Sugluk. Continental collison at Sugluk would have thrust the older and higher grade Sugluk rocks over the Deception gneisses, produced the broad Deception antiform, and displaced the Cape Smith rocks to the south in a series of north-dipping thrust slices.

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50

Kerr, Andrew, George A. Jenner, and Brian J. Fryer. "Sm–Nd isotopic geochemistry of Precambrian to Paleozoic granitoid suites and the deep-crustal structure of the southeast margin of the Newfoundland Appalachians." Canadian Journal of Earth Sciences 32, no. 2 (February 1, 1995): 224–45. http://dx.doi.org/10.1139/e95-019.

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In the Eastern Central Mobile Belt of the Newfoundland Appalachians, late Precambrian basement inliers have εNd from −3 to +2, but Cambro-Ordovician metasedimentary rocks have initial εNd below −7. This region is inferred to have an "inverted" crustal residence structure, which influenced subsequent Appalachian-cycle magmatism. Ordovician and Silurian granitoid suites have εNd of −8 to −2, bracketing both basement and cover, but peraluminous, "S-type" granites have the lowest εNd. Devonian granites have initial εNd values from −5 to +1, and low εNd is associated with peraluminous character. These Paleozoic granites show geographic trends, with lowest εNd values in areas where metasedimentary rocks are abundant. They are suggested to contain anatectic material from both Precambrian basement and metasedimentary cover, but some "I-type" suites probably also include a mantle-derived component. In the adjacent Avalon Zone, Precambrian plutonic suites mostly have εNd from +1 to +6, but there are negative εNd values (−8 to −4) in the westernmost Avalon Zone. Devonian plutonic suites mostly have εNd from +2 to +5. Thus, the Precambrian crust of the Avalon Zone is largely "juvenile," except at its westernmost edge. Contrasts across the Eastern Central Mobile Belt–Avalon Zone boundary, defined by the Dover–Hermitage Bay fault system, indicate a major, crustal-scale structure, and suggest an isotopically distinct "central block" beneath the central Appalachian Orogen, rather than a simple extension of "Avalonian" crust. Similar geographic–isotopic patterns have been reported in Nova Scotia and New Brunswick, suggesting that this pattern represents a first-order deep-crustal subdivision of the northern Appalachian Orogen.

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Journal articles on the topic 'Basement inlier'

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