scholarly journals Geochemistry and Sr, Nd isotopic composition of the Hronic Upper Paleozoic basic rocks (Western Carpathians, Slovakia)

2015 ◽  
Vol 66 (1) ◽  
pp. 3-17 ◽  
Author(s):  
Jozef Vozár ◽  
Ján Spišiak ◽  
Anna Vozárová ◽  
Jakub Bazarnik ◽  
Ján Krái
Keyword(s):  
Basaltic Andesite ◽  
Parental Magma ◽  
Crustal Material ◽  
Nd Isotope ◽  
Upper Paleozoic ◽  
Three Samples ◽  
Original Magma ◽  
Basic Rocks ◽  
Nd Isotopic Composition ◽  
Heterogeneous Source

Abstract The paper presents new major and trace element and first Sr-Nd isotope data from selected lavas among the Permian basaltic andesite and basalts of the Hronicum Unit and the dolerite dykes cutting mainly the Pennsylvanian strata. The basic rocks are characterized by small to moderate mg# numbers (30 to 54) and high SiO2 contents (51-57 wt. %). Low values of TiO2 (1.07-1.76 wt. %) span the low-Ti basalts. Ti/Y ratios in the dolerite dykes as well as the basaltic andesite and basalt of the 1st eruption phase are close to the recommended boundary 500 between high-Ti and low-Ti basalts. Ti/Y value from the 2nd eruption phase basalt is higher and inclined to the high-Ti basalts. In spite of this fact, in all studied Hronicum basic rocks Fe2O3* is lower than 12 wt. % and Nb/La ratios (0.3-0.6) are low, which is more characteristic of low-Ti basalts. The basic rocks are characterized by Nb/La ratios (0.56 to 0.33), and negative correlations between Nb/La and SiO2, which point to crustal assimilation and fraction crystallization. The intercept for Sr evolution lines of the 1st intrusive phase basalt is closest to the expected extrusions age (about 290 Ma) with an initial 87Sr/86Sr ratio of about 0.7054. Small differences in calculated values ISr document a partial Sr isotopic heterogeneity source (0.70435-0.70566), or possible contamination of the original magma by crustal material. For Nd analyses of the three samples, the calculated values εCHUR (285 Ma) are positive (from 1.75 to 3.97) for all samples with only subtle variation. Chemical and isotopic data permit us to assume that the parental magma for the Hronicum basic rocks was generated from an enriched heterogeneous source in the subcontinental lithospheric mantle.

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 The role of island-arc oceanic, collisional and intraplate magmatism in the formation of continental crust in the Mongolia-Trasnbaikalia region: geostructural, geochronological and Sm-Nd isotope data

2021 ◽  
Vol 12 (1) ◽  
pp. 1-47
Author(s):  
I. V. Gordienko
Keyword(s):  
Continental Crust ◽  
Early Stage ◽  
Island Arc ◽  
Published Data ◽  
Crustal Material ◽  
Tectonic Structures ◽  
Nd Isotope ◽  
Isotope Data ◽  
Intraplate Magmatism

The formation of continental crust in the Mongolia-Transbaikalia region is researched to identify the mechanisms of interactions between the crust and the mantle in the development of the Neoarchean, Proterozoic and Paleozoic magmatic and sedimentary complexes in the study area. Using the results of his own studies conducted for many years and other published data on this vast region of Central Asia, the author have analysed compositions, ages and conditions for the formation of Karelian, Baikalian, Caledonian and Hercynian structure-formational complexes in a variety of geodynamic settings. Based on the geostructural, petrological, geochemical, geochronological and Sm-Nd isotope data, he determines the crustal and mantle sources of magmatism, conducts the identification and mapping of isotopic provinces, and reveals the role of island-arc oceanic, accretion-collision and intraplate magmatism in the formation of continental crust. Considering the formation of the bulk continental crust, three main stages are distinguished: (1) Neoarchean and Paleoproterozoic (Karelian) (almost 30% of the crust volume), (2) Meso-Neoproterozoic (Baikalian) (50%), and (3) Paleozoic (Caledonian and Hercynian) (over 20%). This sequence of the evolution stages shows the predominance of the ancient crustal material in igneous rocks sources at the early stage. During the subsequent stages, tectonic structures created earlier were repeatedly reworked, and mixed crustal-mantle and juvenile sources were widely involved in the formation of the bulk continental crust in the study area.

Ion Microprobe Determination of Rare Earth Elements in Perovskite from Kimberlites and Alnöites

1988 ◽  
Vol 52 (366) ◽  
pp. 331-339 ◽  
Author(s):  
Roger H. Mitchell ◽  
Stephen J. B. Reed
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Accurate Determination ◽  
Parental Magma ◽  
Molecular Ions ◽  
Crustal Material ◽  
Ion Microprobe ◽  
Smooth Curves ◽  
Ion Probe

AbstractIon microprobe analysis ofperovskite from kimberlites and alnöites permits the accurate determination of La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er and Yb at the part per million level. Other rare earth elements (REE) are subject to interferences in the mass spectrum caused by matrix-derived molecular ions and cannot easily be determined with comparable precision. Chondrite-normalized plots of the ion probe REE data are smooth curves, confirming the superiority of this technique over electron microprobe methods at the levels of REE abundance found in these perovskites. The perovskites analysed contain between 2.8 and 7.1 wt. % REE oxides and are highly enriched in the light REE, having La/Yb ratios of 577–3229. These La/Yb ratios are not representative of the parental magmas but result from REE fractionation during crystallization of the perovskite. Parental magma La/Yb ratios are estimated to be of the order of 120–650. The lower La/Yb ratios (80–200) found for whole-rock kimberlites are considered to result from contamination by relatively heavy REE-enriched crustal material.

Petrological Features of Korsun'-Novomyrhorod Anorthosite-Rapakivi Granite Pluton

2021 ◽  
Vol 43 (4) ◽  
pp. 25-49
Author(s):  
S.G. KRYVDIK ◽  
O.V. DUBYNA ◽  
P.F. YAKUBENKO
Keyword(s):  
High Alumina ◽  
Crustal Material ◽  
Rapakivi Granite ◽  
Granite Pluton ◽  
Number Of Factors ◽  
Erosion Level ◽  
Granite Magmatism ◽  
Geochemical Studies ◽  
Lower Crustal ◽  
Basic Rocks

The Korsun’-Novomyrhorod pluton is the second after the Korosten one in terms of the scale of Proterozoic (1757-1748 Ma) anorthosite-rapakivi-granite magmatism in the Ukrainian Shield. According to geochronological data, pluton was formed as a result of multiple ascending and crystallization of basic to acidic melts. Differentiation of initial melts because to be responsible for gabbro-anorthosite and monzonites series crystallization. Whereas rapakivi granites, which are predominate in the modern erosion level, were formed from felsic magma not directly related with differentiation of basic melt. In view of the current level of mineralogical research, it is difficult to use modern geobarometry methods to reliably estimate the depth of rocks crystallization. At the same time, a number of factors (absence of volcanic and dike analogues of basic rocks, insignificant distribution of pegmatite bodies, predominance of high-Fe mafic minerals, absence of primary magnetite, etc.) indicate deeper conditions for rocks disclosed by modern erosional cut in comparition to similar Korosten pluton. Therefore, the liquid line of dissent, petrological and mineralogical features of the rocks can be explained by the reducing (low fO2) or abyssal conditions of their formation. It is possible that the deeper conditions of crystallization of parental melt are due to more distinctly developed syenitic trend of evolution with the appearance of high-Fe syenites during final stages. Preliminary data indicate on possibility of vertical layering of gabbro-anorthosite massifs, which manifested by increasing proportion of high-Fe basic rocks with depth. Available isotope-geochemical studies do not provide unambiguous data on regarding reservoirs of primary melts implaying both mantle and mixed mantle-crustal their origin. The evolution of the petrochemical features of basic rocks, in our opinion, is in better agreement with their formation as result of differentiation of the primary high-alumina tholeiitic melt, significantly contaminated by lower crustal material. This determined the subalkaline nature of basic rocks and a significant predominance of norites, in comparition to more typical gabbros, and monzonites. In contrast to the previously proposed hypotheses of the formation of intermediate rocks because of partial melting of felsic rocks by basic intrusions, or mingling of basic and acidic melts, some of petrochemical features and geological position can be satisfactorily explained by their crystallization from the residual melt.

Tin Enrichment in Magmatic-Hydrothermal Environments Associated with Cassiterite Mineralization at Ardlethan, Eastern Australia: Insights from Rb-Sr and Sm-Nd Isotope Compositions in Tourmaline

2020 ◽  
Author(s):  
Patrick Carr ◽  
Marc D. Norman ◽  
Vickie C. Bennett ◽  
Phillip L. Blevin
Keyword(s):  
Parental Magma ◽  
Nd Isotope ◽  
Chemical Leaching ◽  
Hydrothermal Processes ◽  
Eastern Australia ◽  
Type Granite ◽  
Hydrothermal Environments ◽  
Afc Process ◽  
Geologic Processes ◽  
Highly Evolved

Abstract Primary cassiterite mineralization is often associated with highly evolved granites, but the magmatic and hydrothermal processes that produce these deposits are often difficult to decipher. In this study, we employed the chemical and Sr-Nd isotope compositions of tourmaline to monitor processes of Sn enrichment in the magmatic and hydrothermal stages of the Ardlethan granite (Australia) and its associated Sn deposits. Initial 87Sr/86Sr (0.710–0.717) and ɛNd (–5.0 to –1.0) values of late magmatic tourmalines indicate derivation of the Ardlethan granite via an assimilation-fractional crystallization (AFC) process in which incorporation of Ordovician sediment into an I-type granitic parental magma produced an enrichment of Sn at least 30 times over that of the assumed mafic-dominated igneous source of the granite. The rare earth element and Sn concentrations of tourmaline in the greisen deposits together with δ18O of coprecipitated quartz indicate that exsolution of a late-stage, Cl-rich fluid from the Ardlethan granite led to cassiterite mineralization in these deposits. In contrast the Fe/(Fe + Mg) and initial εNd (–9.2 to –12.9) compositions of tourmaline that coprecipitated with cassiterite in the large breccia pipes adjacent to the Ardlethan granite suggest that granite-derived fluids scavenged Sn by chemical leaching of an older S-type granite that hosts the pipes. This study shows that tourmaline can act as a robust monitor of key geologic processes in complex and dynamic magmatic-hydrothermal Sn systems and that its 87Sr/86Sr and ɛNd isotope compositions are especially useful for constraining the nature of magmatic and hydrothermal sources that contributed to these deposits.

Petrology and geochemistry of post-obduction dykes of the Ballantrae complex, SW Scotland

1984 ◽  
Vol 75 (2) ◽  
pp. 211-223 ◽  
Author(s):  
F. V. Holub ◽  
H. Klápová ◽  
B. J. Bluck ◽  
D. R. Bowes
Keyword(s):  
Source Region ◽  
Parental Magma ◽  
Virtual Absence ◽  
Ti Oxides ◽  
Depleted Mantle ◽  
Show Evidence ◽  
Petrology And Geochemistry ◽  
Original Magma ◽  
Metamorphic Facies ◽  
Plate Type

ABSTRACTDoleritic intrusions known to post-date the obduction of the Ballantrae complex during Arenig times record changing magma provenance during the cooling and serpentinisation of obducted peridotite. There are two groups of dolerites with different petrographical and geochemical characteristics.The earlier emplaced group, which is subordinate, is characterised by amphibole formed under low metamorphic facies conditions and the virtual absence of Fe–Ti oxides. Chemically these rocks are of primitive tholeiitic character and are similar to modern island-arc basalts. They were derived from a strongly depleted mantle source region. The source region of the later emplaced group, which is predominant, was much less depleted. Clinopyroxene and plagioclase, much of it albitised, are the dominant minerals. Fe–Ti oxides also are common and there are pronounced chilled margins and well-preserved ophitic textures. Although showing mildly alkaline tendencies, these rocks originated from a tholeiitic parental magma of “within-plate” type.Both groups show evidence of rodingitisation and associated alteration related to serpentinisation of the peridotite. During the metasomatic activity, only some elements were mobile, while Al2O3, total Fe, MgO, TiO2, Cr, Ni, Nb, Y and Zr remained almost constant. Assessment of original magma type and geotectonic environment, and demonstration that both groups of doleritic rocks show the products of fractionation, has relied heavily on data for the apparently immobile elements and on petrographical study which identified those rocks least affected by alteration.

Permian lamprophyres from the Western Carpathians: a review

2021 ◽  
pp. SP513-2020-237
Author(s):  
Ján Spišiak ◽  
Lucia Vetráková ◽  
David Chew ◽  
Štefan Ferenc ◽  
Viera Šimonová ◽  
...  
Keyword(s):  
Hydrothermal Fluid ◽  
Mineralogical Composition ◽  
Western Carpathians ◽  
Crustal Material ◽  
Calc Alkaline ◽  
Geochemical Composition ◽  
Nd Isotope ◽  
Icp Ms ◽  
Compositional Variations ◽  
Alkaline Lamprophyres

AbstractCalc-alkaline lamprophyres from the Western Carpathians occur as dykes and sills in the crystalline complexes (predominantly granites and gneisses) of the Tatric Unit. Some of the lamprophyre dykes have been strongly overprinted by tectonism and hydrothermal fluid ingress. They have a similar mineralogical composition, and they are comprised of clinopyroxene, amphibole, biotite and plagioclase. Based on their modal composition, they can be classified as spessartites and kersantites, and based on their geochemical composition, most of them are of calc-alkali type. Lamprophyres from individual core complexes (e.g. the Malá Fatra Mountains and Nízke Tatry Mountains) exhibit variable Nb, Ta and Sr–Nd isotope signatures. These differences are probably due to compositional variations in the mantle source and/or the lower crust at the site of lamprophyre melt generation, or variable incorporation of crustal material. The age of the lamprophyres is Permian (c. 265 Ma) based on U–Pb LA-ICP-MS dating of apatite micro-phenocrysts.

scholarly journals O–H–Sr–Nd isotope constraints on the origin of the Famatinian magmatic arc, NW Argentina

2020 ◽  
Vol 157 (12) ◽  
pp. 2067-2080 ◽  
Author(s):  
P. Alasino ◽  
C. Casquet ◽  
C. Galindo ◽  
R. Pankhurst ◽  
C. Rapela ◽  
...  
Keyword(s):  
Metamorphic Rocks ◽  
Crustal Material ◽  
Nd Isotopes ◽  
Nd Isotope ◽  
Sierras Pampeanas ◽  
Mafic Rocks ◽  
Oxygen Isotope Exchange ◽  
Magmatic Arc ◽  
Zircon Crystallization ◽  
Major Process

AbstractWe report a study of whole-rock O–H–Sr–Nd isotopes of Ordovician igneous and metamorphic rocks exposed at different crustal palaeodepths along c. 750 km in the Sierras Pampeanas, NW Argentina. The isotope compositions preserved in the intermediate rocks (mostly tonalite) (average δ18O = +8.7 ± 0.5‰, δD = −73 ± 14‰, 87Sr/86Srt = 0.7088 ± 0.0001 and εNdt = −4.5 ± 0.6) show no major difference from those of most of the mafic rocks (average δ18O = +8 ± 0.8‰, δD = −84 ± 18‰, 87Sr/86Srt = 0.7082 ± 0.0016 and εNdt = −4 ± 1.1), suggesting that most of their magmas acquired their crustal characteristics in the mantle. The estimate of assimilation of crustal material (δ18O = +12.2 ± 1.7‰, δD = −89 ± 21‰, 87Sr/86Srt = 0.7146 ± 0.0034 and εNdt = −6.9 ± 0.7) by the tonalite is in most samples within the range 10–20%. Felsic magmas that reached upper crustal levels had isotope values (δ18O = +9.9 ± 1.5‰, δD= −76 ± 5‰, 87Sr/86Srt = 0.7067 ± 0.0010, εNdt = −3.5 ± 1.4) suggesting that they were not derived by fractionation of the contaminated intermediate magmas, but evolved from different magma batches. Some rocks of the arc, both igneous (mostly gabbro and tonalite) and metamorphic, underwent restricted interaction with meteoric fluids. Reported values of δ18O of magmatic zircons from the Famatinian arc rocks (+6 to +9‰) are comparable to our δ18O whole-rock data, indicating that pervasive oxygen isotope exchange in the lower crust was not a major process after zircon crystallization.

Geochemistry of the Little Dal basalts: continental tholeiites from the Mackenzie Mountains, Northwest Territories, Canada

1997 ◽  
Vol 34 (1) ◽  
pp. 50-58 ◽  
Author(s):  
Francis Ö. Dudás ◽  
Rigel L. Lustwerk
Keyword(s):  
Northwest Territories ◽  
Fractional Crystallization ◽  
Source Region ◽  
Sedimentary Rocks ◽  
Crustal Component ◽  
Lava Sequence ◽  
Original Magma ◽  
Geochemical Variation ◽  
Mackenzie Mountains ◽  
Nd Isotopic Composition

Analyses of the Little Dal lavas and the 779 Ma Tsezotene sills, both of the Mackenzie Mountains Supergroup, Northwest Territories, Canada, show them to be continental tholeiites that are geochemically related. The plagioclase- and clinopyroxene-phyric lavas are geochemically evolved and enriched in iron (up to 20.2 wt.% as Fe2O3). Two magmatic lineages are identifiable and may represent different degrees of partial melting in the same source region, but cannot be related by fractional crystallization. Within each lineage, geochemical variation can be explained by fractional crystallization involving up to 60% crystallization of the original magma. The most evolved lavas occur at the base of the pile; less fractionated lavas occur toward the top of the sequence. The Nd isotopic composition of the Little Dal lavas averages ε = 1.4 at 780 Ma. Trace element and isotopic compositions are permissive of contamination by continental crust, but do not require a crustal component. The preserved volume of the Little Dal basalts is anomalously low (−100 km3) compared with other Proterozoic continental tholeiites. There is considerable basaltic detritus in the sedimentary rocks of the overlying Coates Lake and Rapitan groups, and much of the original lava sequence may have been eroded. The Little Dal magmatic event is interpreted to be an early manifestation of rifting of North America from Australia.

Sign in / Sign up

Export Citation Format

Share Document