scholarly journals Archean Rocks of the Diorite Window Block in the Southern Framing of the Monchegorsk (2.5 Ga) Layered Mafic-Ultramafic Complex (Kola Peninsula, Russia)

Minerals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 848
Author(s):  
Pavel Pripachkin ◽  
Tatiana Rundkvist ◽  
Nikolay Groshev ◽  
Aiya Bazai ◽  
Pavel Serov
Keyword(s):  
Kola Peninsula ◽  
Geochemical Data ◽  
Pb Isotope ◽  
Garnet Porphyroblasts ◽  
Isotope Data ◽  
Ultramafic Complex ◽  
Archean Basement ◽  
Monchegorsk Complex

The intermediate rocks classified as diorite-gneisses occur within the southern part of the Monchegorsk (2.5 Ga) layered mafic-ultramafic complex (Kola Peninsula, Russia). These diorite-gneisses belong to a block historically known as the diorite window (DW) block. The same rocks occur in a framing of the Monchegorsk complex. The DW block is predominantly composed of diorite-gneisses and, to a lesser degree, of amphibolites. Multi-ordinal banding, complex folding, boudinage and metamorphic transformations, garnet porphyroblasts, and tourmaline veinlets are typical of the diorite-gneisses. In accordance with the U-Pb isotope data, the age of the diorite-gneisses in the DW block is 2736.0 ± 4.6 Ma. The Sm-Nd mineral (garnet, biotite, and tourmaline) isochron for the DW rocks has yielded an age of 1806 ± 23 Ma (related to the processes of the Svecofennian orogeny). The DW diorite-gneisses are compared with the metadiorites of the Gabbro-10 massif. The latter is a part of the Monchegorsk complex, with U-Pb crystallization age of 2498 ± 6 Ma. On the basis of geological and isotope-geochemical data, it is shown that the DW rocks belong to the Archean basement while the Gabbro-10 metadiorites probably represent one of the late-magmatic phases of the Monchegorsk complex.

Textural evolution of perovskite in the Afrikanda alkaline–ultramafic complex, Kola Peninsula, Russia

2018 ◽  
Vol 173 (12) ◽  
Author(s):  
Naomi J. Potter ◽  
Matthew R. M. Ferguson ◽  
Vadim S. Kamenetsky ◽  
Anton R. Chakhmouradian ◽  
Victor V. Sharygin ◽  
...  
Keyword(s):  
Kola Peninsula ◽  
Textural Evolution ◽  
Ultramafic Complex

Origin of the Ordovician Mansehra granite in the NW Himalaya, Pakistan: constraints from Sr–Nd isotopic data, zircon U–Pb age and Hf isotopes

2018 ◽  
Vol 481 (1) ◽  
pp. 277-298 ◽  
Author(s):  
Masatsugu Ogasawara ◽  
Mayuko Fukuyama ◽  
Rehanul Haq Siddiqui ◽  
Ye Zhao
Keyword(s):  
Granitic Magma ◽  
Geochemical Data ◽  
Large Contribution ◽  
Crustal Material ◽  
Sr Isotope ◽  
Nw Himalaya ◽  
Nd Isotope ◽  
Isotope Data ◽  
Late Neoproterozoic ◽  
T Values

AbstractThe Mansehra granite in the NW Himalaya is a typical Lesser Himalayan granite. We present here new whole-rock geochemistry, Rb–Sr and Sm–Nd isotope data, together with zircon U–Pb ages and Hf isotope data, for the Mansehra granite. Geochemical data for the granite show typical S-type characteristics. Zircon U–Pb dating yields 206Pb/238U crystallization ages of 483–476 Ma. The zircon grains contain abundant inherited cores and some of these show a clear detrital origin. The 206Pb/238U ages of the inherited cores in the granite cluster in the ranges 889–664, 1862–1595 and 2029 Ma. An age of 664 Ma is considered to be the maximum age of the sedimentary protoliths. Thus the Late Neoproterozoic to Cambrian sedimentary rocks must be the protolith of the Mansehra granitic magma. The initial Sr isotope ratios are high, ranging from 0.7324 to 0.7444, whereas the εNd(t) values range from −9.2 to −8.6, which strongly suggests a large contribution of old crustal material to the protoliths. The two-stage Nd model ages and zircon Hf model ages are Paleoproterozoic, indicating that the protolith sediments were derived from Paleoproterozoic crustal components.

scholarly journals A database of Holocene nearshore marine mollusc shell geochemistry from the Northeast Pacific

2021 ◽  
Author(s):  
Hannah M. Palmer ◽  
Veronica Padilla Vriesman ◽  
Roxanne M. W. Banker ◽  
Jessica R. Bean
Keyword(s):  
Carbon Isotope ◽  
Heat Waves ◽  
Indigenous Communities ◽  
Geochemical Data ◽  
Shell Middens ◽  
Data Set ◽  
Oxygen And Carbon Isotope ◽  
Northeast Pacific ◽  
Isotope Data ◽  
Δ13c And Δ18o

Abstract. The shells of marine invertebrates can serve as high-resolution records of oceanographic and atmospheric change through time. In particular, oxygen and carbon isotope analyses of nearshore marine calcifiers that grow by accretion over their lifespans provide seasonal records of environmental and oceanographic conditions. Archaeological shell middens generated by Indigenous communities along the Northeast Pacific coast contain shells harvested over multiple seasons for millennia. These shell middens, as well as analyses of archival and modern shells, have the potential to provide multi-site, seasonal archives of nearshore conditions throughout the Holocene. A significant volume of oxygen and carbon isotope data from archaeological shells exists, yet is separately published in archaeological, geochemical, and paleoceanographic journals and has not been comprehensively analyzed to examine oceanographic change over time. Here, we compiled a database of previously published oxygen and carbon isotope data from archaeological, archival, and modern marine molluscs from the North American coast of the Northeast Pacific (32° N to 50° N). This database includes oxygen and carbon isotope data from over 550 modern, archaeological, and sub-fossil shells from 8880 years before present (BP) to the present, from which there are 4,845 total δ13C and 5,071 total δ18O measurements. Shell dating and sampling strategies vary among studies (1–118 samples per shell) and vary significantly by journal discipline. Data are from various bivalves and gastropod species, with Mytilus spp. being the most commonly analyzed taxon. This novel database can be used to investigate changes in nearshore sea surface conditions including warm-cool oscillations, heat waves, and upwelling intensity, and provides nearshore calcite δ13C and δ18O values that can be compared to the vast collections of offshore foraminifera calcite δ13C and δ18O data from marine sediment cores. By utilizing previously published geochemical data from midden and museum shells rather than sampling new specimens, future scientific research can reduce or omit the alteration or destruction of culturally valued specimens and sites. The data set is publicly available through PANGAEA at https://doi.org/10.1594/PANGAEA.932671 (Palmer et al., 2021).

scholarly journals Supplemental Material: Interplay of Cretaceous transpressional deformation and continental arc magmatism in a long-lived crustal boundary, central Fiordland, New Zealand

2020 ◽  
Author(s):  
H.J. Blatchford ◽  
et al.
Keyword(s):  
New Zealand ◽  
Cross Sections ◽  
Geochemical Data ◽  
Arc Magmatism ◽  
Sample Collection ◽  
Pb Isotope ◽  
Continental Arc ◽  
Geologic Map ◽  
Backscattered Electron ◽  
Continental Arc Magmatism

Analytical methods used are described in Supplemental Text. Sample collection locations shown in Figure 3 are detailed in Table S1. Isotopic and geochemical data are presented in Tables S2–S4. U-Pb isotope data and geochemistry data for the sample are presented in Tables S5 and S6, respectively. A series of cross sections and a geologic map of the study area including field stations and associated structural measurements are presented in Figure S1. Cathodoluminescence images of zircon grains are shown in Figures S2 and S3. Backscattered electron images of analyzed titanite grains are presented in Figure S4.<br>

Nd and Pb isotope mapping of crustal domains within the Makkovik Province, Labrador

2018 ◽  
Vol 156 (5) ◽  
pp. 833-848 ◽  
Author(s):  
R. M. MOUMBLOW ◽  
G. A. ARCURI ◽  
A. P. DICKIN ◽  
C. F. GOWER
Keyword(s):  
Early Stage ◽  
Foreland Basin ◽  
Mobile Belt ◽  
South American ◽  
Pb Isotope ◽  
Volcanic Arc ◽  
Nd Isotope ◽  
North American Cordillera ◽  
Tectonic Model ◽  
Isotope Data

AbstractThe Makkovik Province of eastern Labrador represents part of an accretionary orogen active during an early stage in the development of the Palaeoproterozoic southern Laurentian continental margin. New Nd isotope data for the eastern Makkovik Province suggest that accreted juvenile Makkovik crust was generated in the Cape Harrison domain during a single crust-forming event at c. 2.0 Ga. Pb isotope data support this model, and show a strong similarity to radiogenic crustal signatures in the juvenile Palaeoproterozoic crust of the Ketilidian mobile belt of southern Greenland. As previously proposed, an arc accretion event at c. 1.9 Ga triggered subduction-zone reversal and the development of an ensialic arc on the composite margin. After the subduction flip, a temporary release of compressive stress at c. 1.87 Ga led to the development of a retro-arc foreland basin on the downloaded Archean continental edge, forming the Aillik Group. Unlike previous models, a second arc is not envisaged. Instead, a compressive regime at c. 1.82 Ga is attributed to continued ensialic arc plutonism on the existing margin. The tectonic model for the Makkovikian orogeny proposed here is similar to that for the Ketilidian orogeny. Major- and trace-element analyses suggest that much of the magmatism in the Makkovik orogen results from post-accretionary ensialic arc activity, and that few vestiges remain of the original accreted volcanic arc. This pattern of arc accretion and intense post-accretion reworking is common to many accretionary orogens, such as the South American Andes and North American Cordillera.

Pb-isotope evidence on the origin of the West Shropsh orefield, England

1996 ◽  
Vol 133 (5) ◽  
pp. 611-617 ◽  
Author(s):  
R. Haggerty ◽  
B. M. Rohl ◽  
P. D. Budd ◽  
N. H. Gale
Keyword(s):  
Sea Water ◽  
Multiple Sources ◽  
Pb Isotope ◽  
The West ◽  
Minor Variation ◽  
Isotope Data ◽  
Water Origin ◽  
Isotope Evidence ◽  
Significant Spread ◽  
Isotope Variation

AbstractPb-isotope data on ore galenas from the West Shropshire orefield show a significant spread of 20pb/204pb values, with minor variation in 207Pb/204Pb and 208Pb/204Pb ratios. These indicate that lead was derived from multiple sources, some of them uranium-enriched and incompletely mixed prior to ore deposition. Four possible mineralizing agents are considered: circulating sea-water, metamorphic waters, basinal brines and convecting formation waters. Pb-isotope data exclude a circulating sea-water origin for the mineralization, and best support a convecting formation water mineralizing agent. A model involving a single fluid tapping multiple lead sources is proposed to explain the observed Pb-isotope variation.

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