Nd isotopic evidence for crustal recycling in the ca. 2.0 Ga subsurface of western Canada

1991 ◽  
Vol 28 (8) ◽  
pp. 1140-1147 ◽  
Author(s):  
R. J. Thériault ◽  
G. M. Ross
Keyword(s):  
Isotopic Data ◽  
Tectonic Zone ◽  
Isotopic Signatures ◽  
Crustal Recycling ◽  
The North ◽  
Tectonic History ◽  
Depleted Mantle ◽  
History Of ◽  
Mantle Component ◽  
Northern Alberta

Sm–Nd isotopic data are presented for 23 drill-core samples from five aeromagnetically and geochronologically (U–Pb zircon) distinct domains of the Precambrian basement of northern Alberta. The domains in question are the Taltson (1.96–1.94 Ga), Buffalo Head (2.32–1.99 Ga), Chinchaga (2.19–2.09 Ga), Ksituan (1.99–1.90 Ga), and Nova (2.81 Ga). These domains are truncated to the north and south by the Great Slave Lake shear zone and the Snowbird tectonic zone, respectively.Initial εNd values are −5.0 to −9.7 for the Taltson, +0.2 to −6.3 for the Buffalo Head, +0.6 to −1.8 for the Chinchaga, −1.8 to −2.1 for the Ksituan and +5.6 for the Nova. Crustal residence model ages fall in the 2.5–2.8 Ga range. The Nd isotopic signatures may be viewed in terms of mixing a minimum of 10% Archean continental crust with a depleted-mantle component. Speculations on the tectonic history of the basement domains in question involve the assembly of Archean crustal nuclei to form the Buffalo Head – Chinchaga composite domain. Arc magmatism resulting from plate subduction to the east and west of the Buffalo Head – Chinchaga composite domain would have generated the Taltson and Ksituan domains. The Nd isotopic data suggest that the basement of northern Alberta consists of crust of late Archean crustal residence age which has been extensively remobilized in the Early Proterozoic.

scholarly journals Ancient helium and tungsten isotopic signatures preserved in mantle domains least modified by crustal recycling

2020 ◽  
Vol 117 (49) ◽  
pp. 30993-31001
Author(s):  
Matthew G. Jackson ◽  
Janne Blichert-Toft ◽  
Saemundur A. Halldórsson ◽  
Andrea Mundl-Petermeier ◽  
Michael Bizimis ◽  
...  
Keyword(s):  
Isotopic Signature ◽  
Geochemical Data ◽  
Recycled Materials ◽  
Isotopic Signatures ◽  
Crustal Recycling ◽  
Ocean Island Basalts ◽  
Depleted Mantle ◽  
History Of ◽  
Earth’S Interior ◽  
Earth's Interior

Rare high-3He/4He signatures in ocean island basalts (OIB) erupted at volcanic hotspots derive from deep-seated domains preserved in Earth’s interior. Only high-3He/4He OIB exhibit anomalous182W—an isotopic signature inherited during the earliest history of Earth—supporting an ancient origin of high3He/4He. However, it is not understood why some OIB host anomalous182W while others do not. We provide geochemical data for the highest-3He/4He lavas from Iceland (up to 42.9 times atmospheric) with anomalous182W and examine how Sr-Nd-Hf-Pb isotopic variations—useful for tracing subducted, recycled crust—relate to high3He/4He and anomalous182W. These data, together with data on global OIB, show that the highest-3He/4He and the largest-magnitude182W anomalies are found only in geochemically depleted mantle domains—with high143Nd/144Nd and low206Pb/204Pb—lacking strong signatures of recycled materials. In contrast, OIB with the strongest signatures associated with recycled materials have low3He/4He and lack anomalous182W. These observations provide important clues regarding the survival of the ancient He and W signatures in Earth’s mantle. We show that high-3He/4He mantle domains with anomalous182W have low W and4He concentrations compared to recycled materials and are therefore highly susceptible to being overprinted with low3He/4He and normal (not anomalous)182W characteristic of subducted crust. Thus, high3He/4He and anomalous182W are preserved exclusively in mantle domains least modified by recycled crust. This model places the long-term preservation of ancient high3He/4He and anomalous182W in the geodynamic context of crustal subduction and recycling and informs on survival of other early-formed heterogeneities in Earth’s interior.

scholarly journals Silicic volcanism in the Scottish Lower Carboniferous; lavas, intrusions and ignimbrites of the Garleton Hills Volcanic Formation, SE Scotland

2020 ◽  
Vol 56 (1) ◽  
pp. 63-79
Author(s):  
Brian G. J. Upton ◽  
Linda A. Kirstein ◽  
Nicholas Odling ◽  
John R. Underhill ◽  
Robert M. Ellam ◽  
...  
Keyword(s):  
Extensional Tectonics ◽  
Isotopic Data ◽  
Central Type ◽  
Lower Carboniferous ◽  
The North ◽  
Basaltic Magmatism ◽  
North Side ◽  
Volcanic Formation ◽  
History Of ◽  
Magmatic History

Extensional tectonics and incipient rifting on the north side of the Iapetus suture were associated with eruption of (mainly) mildly alkaline olivine basalts. Initially in the Tournaisian (Southern Uplands Terrane), magmatic activity migrated northwards producing the Garleton Hills Volcanic Formation (GHVF) across an anomalous sector of the Southern Uplands. The latter was followed by resumption of volcanism in the Midland Valley Terrane, yielding the Arthur's Seat Volcanic Formation. Later larger-scale activity generated the Clyde Plateau Volcanic Formation (CPVF) and the Kintyre lavas on the Grampian Highlands Terrane. Comparable volcanic successions occur in Limerick, Ireland. This short-lived (c. 30 myr) phase was unique in the magmatic history of the Phanerozoic of the British Isles in which mildly alkaline basaltic magmatism locally led to trachytic differentiates. The Bangly Member of the GHVF represents the largest area occupied by such silicic rocks. The most widespread lavas and intrusions are silica-saturated/oversaturated trachytes for which new whole-rock and isotopic data are presented. Previously unrecognized ignimbrites are described. Sparse data from the fiamme suggest that the magma responsible for the repetitive ignimbrite eruptions was a highly fluid rhyolite. The Bangly Member probably represents the remains of a central-type volcano, the details of which are enigmatic.

scholarly journals Cenozoic tectonic history of the North America-Caribbean plate boundary zone in western Cuba

1997 ◽  
Vol 102 (B5) ◽  
pp. 10055-10082 ◽  
Author(s):  
Mark B. Gordon ◽  
Paul Mann ◽  
Dámaso Cáceres ◽  
Raúl Flores
Keyword(s):  
North America ◽  
Plate Boundary ◽  
Boundary Zone ◽  
Caribbean Plate ◽  
The North ◽  
Tectonic History ◽  
History Of ◽  
Plate Boundary Zone

The Rhinns Complex: Proterozoic basement on Islay and Colonsay, Inner Hebrides, Scotland, and on Inishtrahull, NW Ireland

1994 ◽  
Vol 85 (1) ◽  
pp. 77-90 ◽  
Author(s):  
R. J. Muir ◽  
W. R. Fitches ◽  
A. J. Maltman
Keyword(s):  
Igneous Rocks ◽  
Mobile Belt ◽  
Precambrian Basement ◽  
Isotopic Data ◽  
Large Area ◽  
Isotopic Signatures ◽  
The North ◽  
North Side ◽  
Proterozoic Basement ◽  
Complex Forms

ABSTRACTThe Precambrian basement on the islands of Islay, Colonsay and Inishtrahull comprises a deformed igneous association of mainly syenite and gabbro, with minor mafic and felsic intrusions. This association is collectively referred to as the Rhinns Complex. Isotopic data indicate that the complex represents new addition of material to the crust at c. 1·8 Ga. The igneous protolith was juvenile mantle-derived material, not reworked Archaean crust. Overall, the complex has an alkalic composition, with major and trace element patterns similar to igneous rocks generated in a subduction-related setting: high LILE/HFSE and LREE/HREE ratios, together with negative Nb, P and Ti anomalies.The formation of the Rhinns Complex was contemporaneous with the Laxfordian tectonothermal cycle in the Lewisian Complex. These Proterozoic events are most likely associated with an extensive 1·9–1·7 Ga mobile belt around the southern margin of Laurentia-Baltica. As part of this belt, the Rhinns Complex forms a link between the Ketilidian province of South Greenland and the Svecofennian of Scandinavia.Inherited isotopic signatures in the Caledonian granites on the north side of the Highland Boundary Fault may reflect the presence of a large area of Proterozoic basement (?Rhinns Complex) beneath Scotland and NW Ireland. Alternatively, the Proterozoic signature could be derived from the incorporation of Moine or Dalradian sediment into the granitic magmas.

On the nature of the crust in the vicinity of the southeast Newfoundland Ridge

1978 ◽  
Vol 15 (9) ◽  
pp. 1462-1471 ◽  
Author(s):  
K. D. Sullivan ◽  
C. E. Keen
Keyword(s):  
Focal Point ◽  
Magnetic Data ◽  
Seismic Structure ◽  
Grand Banks ◽  
The North ◽  
Tectonic History ◽  
History Of ◽  
Continental Origin ◽  
Magnetic Lineations ◽  
Gravity And Magnetic Data

This paper presents new seismic reflection, refraction, gravity, and magnetic data bearing on the nature of the crust in the vicinity of the Newfoundland Ridge and the J-anomaly Ridge, immediately south of the Grand Banks. This area experienced a complicated plate tectonic history being the focal point for interactions of the North American, African, and Iberian plates. New data have recently been published for this region and conflicting interpretations have been offered in relation to the oceanic or continental origin of the crust there. The data presented here show that the seismic structure and the most reasonable models for the magnetic anomalies are more consistent with an oceanic origin. The trends and offsets in the magnetic lineations and possible differences in subsidence, north and south of the Newfoundland Ridge, are discussed in relation to possible modes of formation of this feature. It is proposed that similar subsidence histories since mid-Cretaceous time on the Grand Banks and J-anomaly Ridge are related to a similarity in the thermal history of the lithosphere beneath these areas, as the ridge crest migrated eastwards, and do not require the same type of crust to underlie both areas.

Ancient DNA and Stable Isotopes

2016 ◽  
Author(s):  
Dennis O'Rourke ◽  
Justin Tackney ◽  
Joan Coltrain ◽  
Jennifer Raff
Keyword(s):  
Ancient Dna ◽  
Multidisciplinary Approach ◽  
Adaptive Strategies ◽  
Population History ◽  
Isotopic Signatures ◽  
Resource Information ◽  
The North ◽  
North American Arctic ◽  
History Of ◽  
Isotope Analyses

Genetic diversity in modern Arctic communities provides a baseline from which to assess population history. This is augmented by documenting patterns of genetic variation in prehistoric populations using ancient DNA methods, and inferring dietary resource information and adaptive strategies derived from stable isotope analyses. This chapter uses this multidisciplinary approach to examine population history and colonization events in the Aleutians of South Alaska, and the origin and population history of Paleoeskimo and Neoeskimo populations of the North American Arctic. The power to identify past demographic events relies on knowledge of both genetic and isotopic signatures of demographic events, and on acquisition of securely dated and well provenienced samples for analysis.

Paleogeographic position of the central Dodecanese Islands, southeastern Greece: The push-pull of Pelagonia

2021 ◽  
Author(s):  
B. Grasemann ◽  
D.A. Schneider ◽  
K. Soukis ◽  
V. Roche ◽  
B. Hubmann
Keyword(s):  
Normal Fault ◽  
White Mica ◽  
The North ◽  
Tectonic History ◽  
Fold And Thrust Belt ◽  
Tectonic Position ◽  
History Of ◽  
Single Grain ◽  
Back Arc ◽  
Bottom To Top

The paleogeographic position of the central Dodecanese Islands at the transition between the Aegean and Anatolian plates plays a considerable role in understanding the link between both geologically unique domains. In this study, we investigate the tectonic history of the central Dodecanese Islands and the general correlation with the Aegean and western Anatolian and focus on the poorly studied islands of Kalymnos and Telendos. Three different major tectonic units were mapped on both islands from bottom to top: (1) The Kefala Unit consists of late Paleozoic, fossil-rich limestones, which have been deformed into a SE-vergent fold-and-thrust belt sealed by an up to 200-m-thick wildflysch-type olistostrome with marble and ultramafic blocks on a scale of tens of meters. (2) The Marina Basement Unit consists of a Variscan amphibolite facies basement with garnet mica schists, quartzites, and amphibolites. (3) Verrucano-type formation violet shales and Mesozoic unmetamorphosed limestones form the Marina Cover Unit. Correlation of these units with other units in the Aegean suggests that Kalymnos is paleogeographically located at the southern margin of the Pelagonian domain, and therefore it was in a structurally upper tectonic position during the Paleogene Alpine orogeny. New white mica 40Ar/39Ar ages confirm the Carboniferous deformation of the Marina Basement Unit followed by a weak Triassic thermal event. Single-grain white mica 40Ar/39Ar ages from pressure solution cleavage of the newly defined Telendos Thrust suggest that the Marina Basement Unit was thrusted toward the north on top of the Kefala Unit in the Paleocene. Located at a tectonically upper position, the units exposed in the central Dodecanese escaped subduction and the syn-orogenic, high-pressure metamorphism. However, these units were affected by post-orogenic extension, and the contact between the Marina Basement Unit and the non-metamorphic Marina Cover Unit has been reactivated by the cataclastic top-to-SSW, low-angle Kalymnos Detachment. Zircon (U-Th)/He ages from the Kefala and Marina Basement Units are ca. 30 Ma, which indicates that exhumation and cooling below the Kalymnos Detachment started in the Oligocene. Conjugate brittle high-angle normal fault systems, which resulted in the formation of four major WNW-ESE−trending graben systems on Kalymnos, localized mainly in the Marina Cover Unit and probably rooted in the mechanically linked Kalymnos Detachment. Since Oligo-Miocene deformation in the northern Dodecanese records top-to-NNE extension and the Kalymnos Detachment accommodated top-to-SSW extension, we suggest that back-arc extension in the whole Aegean realm and transition to the Anatolian plate is bivergent.

Seismic History of Minnesota and It’s Geological Significance: An Update

1989 ◽  
Vol 60 (2) ◽  
pp. 79-86 ◽  
Author(s):  
Val W. Chandler ◽  
G. B. Morey
Keyword(s):  
Seismic Reflection ◽  
Focal Plane ◽  
Large Earthquake ◽  
Aeromagnetic Data ◽  
Tectonic Zone ◽  
The North ◽  
History Of ◽  
Plane Solution ◽  
Stress Buildup

Abstract High-resolution aeromagnetic data have recently been acquired for most of Minnesota under the sponsorship of the Minnesota Future Resources Commission, which also provided funds for test drilling of selected anomalies. The new data show that northwest-trending dikes and fractures are much more common in the Archean terranes than previously believed, and several epicenters are near such faults. The northeast-trending Great Lakes tectonic zone (GLTZ) was thought to be the chief source of seismicity in the state, because several epicenters were aligned with it. However, more recent seismic reflection profiling has demonstrated that the GLTZ has a moderate dip to the north. This dip is not compatible with the previously favored focal plane solution for a relatively large earthquake, which apparently confirmed the seismogenic role of the GLTZ. The alternative focal plane solution for this earthquake, however, is compatible with some northwest-trending structures in the region. We propose that the apparent alignment of epicenters with the GLTZ is related to stress buildup at places where it is intersected by northwest-trending faults, with subsequent movement occurring upon release. A similar model may explain seismicity along the northeast-trending Colorado lineament to the southwest.

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