The first Sm–Nd isotope–geochemical data on the Paleoproterozoic age of metamorphic rocks from the crystalline basement of the Yurovsk rise (Okhotsk massif)

2017 ◽  
Vol 472 (1) ◽  
pp. 11-15 ◽  
Author(s):  
V. K. Kuzmin ◽  
E. S. Bogomolov ◽  
V. A. Glebovitsky
Keyword(s):  
Crystalline Basement ◽  
Geochemical Data ◽  
Metamorphic Rocks ◽  
Nd Isotope ◽  
Okhotsk Massif

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 Investigation of Geology and Hydro-geophysical Features Using Electromagnetic and Vertical Sounding Methods for Abu Zabad Area, Western Kordofan State, Sudan

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
Ahmed Babeker Elhag
Keyword(s):  
Geophysical Methods ◽  
Structural Features ◽  
Groundwater Potential ◽  
Crystalline Basement ◽  
Metamorphic Rocks ◽  
Basement Rock ◽  
Basement Complex ◽  
Groundwater Aquifers ◽  
Electrical Sounding ◽  
Geophysical Features

The geology and hydro-geophysical features can aid in identifying borehole location. The study aims to investigate groundwater aquifers and best location of boreholes in the crystalline basement area of Abu Zabad near El Obeid Southwest, Sudan. The study area is underlain by two aquifers formations from Precambrian age. The oldest units of basement complex of area under investigation consist of metamorphic rocks including gneiss, schist, and quartzite.The geophysical methods electromagnetic (EM) and vertical electrical sounding (VES) surveys showed that best aquifers yield for construction of boreholes are in weathering and fractures formation. The EM results revealed that structural features are significant for groundwater potential and interpretation of the VES data also revealed four geo-electric layers, but generally two distinct lithologic layers, which include Superficial deposit and bedrock-basement respectively. The curves generated from the data revealed H curve and HK curve, and thickness of these layers varies from 15 m to 50 m in the area. The aquifer thickness range from 20 m to 30 m. The study concludes that these techniques are suitable for identifying borehole location in the basement rock in Abu Zabad Area Sudan.

Paleoproterozoic Granitoids of the Yurovka Swell Basement (Okhotsk Massif): First U–Pb SIMS Geochronological and Nd–Sr Isotope–Geochemical Data

2018 ◽  
Vol 478 (1) ◽  
pp. 31-35
Author(s):  
V. K. Kuzmin ◽  
V. A. Glebovitsky ◽  
V. F. Proskurnin ◽  
E. S. Bogomolov ◽  
V. N. Zelepugin ◽  
...  
Keyword(s):  
Geochemical Data ◽  
Sr Isotope ◽  
Okhotsk Massif

Geochronology, Petrogenesis and Oxidation State of the Northparkes Igneous Suite, New South Wales, Australia: Implications for Magma Fertility

2021 ◽  
Author(s):  
Hongda Hao ◽  
Ian H. Campbell ◽  
David R. Cooke ◽  
Eizo Nakamura ◽  
Chie Sakaguchi
Keyword(s):  
Water Content ◽  
Oxidation State ◽  
Geochemical Data ◽  
Island Arcs ◽  
Sulfide Saturation ◽  
Nd Isotope ◽  
Fluid Saturation ◽  
South Wales ◽  
Fluid Release ◽  
Water Contents

Abstract New geochronological and geochemical data for the barren and ore-associated suites from the Northparkes porphyry Cu-Au deposits, Australia, have implications for magma fertility. The Goonumbla and Wombin Volcanics and intrusions are barren in the Northparkes area. A sample from Wombin suite yielded a zircon U-Pb age of 433.8 ± 3.1 Ma, whereas the ore-associated porphyries yielded ages between 441.8 ± 3.7 and 436.3 ± 4.5 Ma. The bulk of the mineralization at Northparkes is associated with a K-feldspar-phyric quartz monzonite porphyry (K-QMP), which gave U-Pb zircon ages of 441.8 ± 3.7 and 441.1 ± 2.5 Ma. Whole-rock Sr-Nd isotope compositions of the Goonumbla, Wombin, and ore-associated suites are similar, with (87Sr/86Sr)i = 0.704112 to 0.704424 and εNd = 5.6 to 6.9, which is typical of primitive intraoceanic island arcs, and their Pb isotope values lie within the MORB array. Most of the zircons from the Wombin and ore-associated suites have arc mantle-like O-Hf isotope compositions, with δ18O values that vary from 6.13 to 4.95, and εHf(t) from 11.5 to 6. These results suggest that the Goonumbla, Wombin, and ore-associated suites originated from typical arc mantle. The magmas that produced the Goonumbla and Wombin suites were dominated by plagioclase-pyroxene fractionation, and the Wombin suite has a low oxidation state with ΔFMQ between ~0 and 1.5. They were relatively reduced and dry. This combination resulted in early sulfide saturation, probably without reaching fluid saturation. Trace element modeling shows that plagioclase-amphibole dominated the later stages of fractionation of the ore-associated suite, implying that it had a higher water content than the barren suites. It was also more oxidized (ΔFMQ from ~0 to 4). The result was late sulfide saturation, which was followed shortly thereafter by voluminous fluid release. As a consequence, the ore-forming fluid effectively transferred Cu and Au from the magma to the site of hydrothermal ore deposition. We suggest that the higher water content and oxidation state of the ore-associated suite was due to the deep underlying magma chamber, which was recharged by many more pulses of magma than the chamber that underlay the barren suites. This is more effective in raising the concentration of incompatible water and ferric iron in the residual melt than straight fractional crystallization. High oxygen fugacities and water contents played a significant role in determining the timing of sulfide and fluid saturation, respectively, and as a result, they had a critical influence on magma fertility.

scholarly journals Age of monazite from metapelitic schists of Atomfjella and Mossel series, Western Ny Friesland, Spitsbergen according to the CHIME method

2021 ◽  
Vol 10 ◽  
pp. 16-24
Author(s):  
S. A. Akbarpuran Haiyatia ◽  
◽  
Yu. L. Gulbin ◽  
S. E. Borisovskiy ◽  
◽  
...  
Keyword(s):  
Crystalline Basement ◽  
Metamorphic Rocks ◽  
The West ◽  
The North ◽  
North Part ◽  
Caledonian Orogeny ◽  
West Spitsbergen ◽  
Age Estimates

The article presents the results of CHIME (chemical Th–U-total Pb isochron method) dating of monazite from metamorphic rocks of Precambrian complexes located in the north part of the West Spitsbergen Island. It is shown that for rocks of Atomfjella Series and Mossel Series, monazite ages are coeval within error (Atomfjella Series: 381 ± 18 Ma, Mossel Series: 377 ± 23 Ma). These age estimates show that metamorphism of the crystalline basement possibly took place during the Late Caledonian orogeny.

The Ludicovian of the Raahe–Ladoga Zone of the Fennoscandian Shield (Isotope-Geochemical Composition and Geodynamic Nature)

2021 ◽  
Vol 62 (10) ◽  
pp. 1089-1106
Author(s):  
A.B. Vrevskii
Keyword(s):  
Isotope Composition ◽  
Geochemical Data ◽  
Island Arcs ◽  
Karelian Craton ◽  
Geochemical Composition ◽  
Nd Isotope ◽  
Tectonic Model ◽  
Isotope System ◽  
Nd Isotope Composition

Abstract —In the northern Ladoga area, the age of the Sortavala Group rocks in the southeast of the Raahe–Ladoga zone of junction of the epi-Archean Fenno-Karelian Craton and the Paleoproterozoic Svecofennian province, their relationship with dome granitoids, the age of the provenances, and the time of metamorphic processes were estimated. The study was focused on the Nd isotope composition of rocks, the geochemical and isotope-geochronological parameters of zircon from the granite-gneisses of the Kirjavalakhti dome, the basal graywackes of the lower unit and the trachytes of the middle unit of the Sortavala Group, and the plagio- and diorite-porphyry dikes cutting the volcanosedimentary units of this group. The new isotope-geochemical data show a Neoarchean age of the granitoids of the Kirjavalakhti dome (2695 ± 13 Ma) and their juvenile nature (εNd(T) = +1.5). The granitoids underwent tectonometamorphic transformations (rheomorphism) in the Paleoproterozoic (Sumian) (2.50–2.45 Ga), which are recorded in the U–Th–Pb isotope system of the rims of the ancient cores of zircon crystals. The volcanosedimentary complex of the Sortavala Group formed on the heterogeneous polychronous (3.10–2.46 Ga) continental crust of the epi-Archean Fenno-Karelian Craton. With regard to the errors in determination of the age of clastic zircon, the minimum concordant U–Th–Pb ages of 1940–1990 Ma of detrital zircon from volcanomictic graywackes of the Pitkyaranta Formation can be taken as the upper age bound of terrigenous rocks, which agrees with the maximum age of the Sortavala Group rocks estimated from the U–Th–Pb (SIMS) age of 1922 ± 11 Ma of the Tervaoya diorites (Matrenichev et al., 2006). According to the proposed new tectonic model, the accumulation of the volcanosedimentary complex of the Sortavala Group, its metamorphism, erosion, and overlapping by the Ladoga Group turbidites had already occurred in the pericratonic part of the epi-Archean Fenno-Karelian Craton by the time of the Svecofennian continent–island arc collision, subduction, and formation of bimodal volcanoplutonic complexes of the young Pyhäsalmi island arcs and felsic volcanics of the Savo schist belt (1920–1890 Ma).

Geochemical and mineralogical characteristics of beach sediments along the coast between Alanya and Silifke (southern Turkey)

Clay Minerals ◽  
2015 ◽  
Vol 50 (2) ◽  
pp. 233-248 ◽  
Author(s):  
M.G. Yalcin ◽  
M. Setti ◽  
F. Karakaya ◽  
E. Sacchi ◽  
N. Ilbeyli
Keyword(s):  
Grain Size ◽  
Trace Metals ◽  
Trace Metal ◽  
Water Content ◽  
Source Rocks ◽  
Geochemical Data ◽  
Metamorphic Rocks ◽  
Low Grade ◽  
Mineral Phases ◽  
Beach Sands

AbstractThe aim of this work was to determine the distribution of trace metals in the coastal sediments from the area between Silifke and Alanya (Turkey) and to investigate the sources of these elements, based on their mineralogical, petrographical and geochemical characteristics. Forty three samples were analysed for the determination of their water content, grain-size distribution, petrographical features and their chemical and mineralogical compositions. The samples had low water content, in agreement with the large sand grain size.The mineralogical composition reflects the complex geological setting of the area. The most abundant mineral phases are represented by calcite and dolomite, followed by quartz and mica. Chlorite, feldspar and other carbonates are present in lesser amounts, while kaolinite was detected in one sample only. All samples contain hematite, chromite, magnetite and goethite and one sample contained pyrite. Samples with high concentrations of trace metals, contained fragments of metamorphic rocks with pyroxene, amphibole, quartz and feldspar, whereas carbonates and opaque minerals were subordinate. Compared to literature data, the average concentrations of several elements and trace metals were great enough to be considered as possibly toxic, exceeding the Turkish higher acceptable limits. Geochemical data were treated statistically using Principal Component Analysis (PCA) to obtain evidence of their distribution and to identify any correlations.Based on the distribution of mineral phases, the area investigated was divided into different provinces, each characterized by the abundance of one, or more, tracer minerals. In the westernmost areas, between Alanya and Demirtas, the sediments indicate a provenance from dolomites or marbles. In the area between Demirtas and Gazipasa the provenance was from quartzites, clastic and metamorphic rocks and in the sector between Guney and Anamur, the sediments were derived mostly from low-grade metamorphic rocks, in particular metaschists and metabasites. The sediments in the area between Anamur and Ovacik, display variable source rocks and those between Ovacik and Silifke, were derived from limestones and, subordinately, clastic rocks.The trace-metal concentrations in beach sands appear to be related to the abundance of silicate minerals derived from weathering of the metamorphic-rock outcrops in the inland mountainous regions. In contrast, the trace-metal contents of the limestone- and dolomite-bearing beach sands were small.

The texture and composition of tourmaline in metasediments of the Sinai, Egypt: Implications for the tectono-metamorphic evolution of the Pan-African basement

2007 ◽  
Vol 71 (1) ◽  
pp. 17-40 ◽  
Author(s):  
M. M. Abu El-Enen ◽  
M. Okrusch
Keyword(s):  
Regional Metamorphism ◽  
Metamorphic Grade ◽  
Crystalline Basement ◽  
Amphibolite Facies ◽  
Metamorphic Rocks ◽  
Pan African ◽  
Chemical Signatures ◽  
Mineral Assemblages ◽  
The Matrix ◽  
Metamorphic Facies

AbstractAccessory tourmaline in metasediments from the Sinai crystalline basement exhibits textural and chemical signatures that relate to the evolution of regional metamorphism and deformation during the Pan-African orogeny and testifies to different P-T path segments. Tourmaline inclusions in various porphyroblasts were formed during the prograde phase of metamorphism; acicular to prismatic crystals in the matrix, oriented sub-parallel to, and enveloped by, the main foliation crystallized syntectonically under prograde and peak metamorphic conditions; tourmaline cross-cutting the main foliation may have formed just after the peak or during the retrograde phase of metamorphism. Some of the cores in tourmaline crystals, showing different colours, are interpreted as former detrital grains. The abundance of tourmaline decreases with increasing peak metamorphic conditions. The tourmaline investigated belongs to the schorl-dravitess group, generally with XMg of 0.42–0.73 and XCa = Ca/(Ca+Na+K+□) of 0.02–0.24, typical of tourmalines in metapelites and metapsammites; whereas detrital cores have been derived from various sources, including former tourmaline-quartz and pre-existing high-metamorphic rocks. Tourmaline of the Sinai metasediments was formed during metamorphism of the sedimentary precursors, essentially in a closed system, where clay minerals and organic matter, together with detrital tourmaline, served as the source of boron. Although a metamorphic facies should be defined by characteristic mineral assemblages present in metamorphic rocks, tourmaline chemistry is a good monitor of P-T conditions in the metapelites and semi-metapelites investigated, showing an increase in XMg with increasing metamorphic grade, where XturMg = 0.60 distinguishes between greenschist and lower-amphibolite facies, while XturMg = 0.65 could distinguish lower- from middle- to upper-amphibolite facies. The results of tourmaline-biotite geothermometry compare well with our former temperature estimates using conventional geothermometry and phase-diagram modelling.

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