Journal articles on the topic 'Sr-Nd-Sm isotopes'
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Huang, Chao, Yue-Heng Yang, Jin-Hui Yang, and Lie-Wen Xie. "In situ simultaneous measurement of Rb–Sr/Sm–Nd or Sm–Nd/Lu–Hf isotopes in natural minerals using laser ablation multi-collector ICP-MS." Journal of Analytical Atomic Spectrometry 30, no. 4 (2015): 994–1000. http://dx.doi.org/10.1039/c4ja00449c.
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This study presents a combined methodology of simultaneously measuring Rb–Sr/Sm–Nd or Sm–Nd/Lu–Hf isotopes in natural minerals by a means of two multiple collector inductively coupled plasma mass spectrometers connected to a 193 nm excimer laser ablation system.
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Armstrong, Richard Lee, Randall R. Parrish, Peter van der Heyden, Krista Scott, Dita Runkle, and Richard L. Brown. "Early Proterozoic basement exposures in the southern Canadian Cordillera: core gneiss of Frenchman Cap, Unit I of the Grand Forks Gneiss, and the Vaseaux Formation." Canadian Journal of Earth Sciences 28, no. 8 (August 1, 1991): 1169–201. http://dx.doi.org/10.1139/e91-107.
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The protolith age of high-grade metamorphic rocks exposed in structurally deep parts of the Omineca Crystalline Belt has been the subject of investigation and controversy for decades. We have applied multiple isotopic dating techniques to rocks of three structural culminations: the Monashee complex (which includes the Frenchman Cap and Thor–Odin gneiss domes), the Grand Forks horst, and the Vaseaux Formation, which lies in the footwall of the Okanagan Valley fault.Frenchman Cap core gneisses contain highly radiogenic Sr that scatters about a 2206 ± 117 Ma (1σ) Rb–Sr isochron with 87Sr/86Sr initial ratio of 0.700 ± 0.002. Monazite and zircon dates for the same rocks are 1851 ± 7 to 2103 ± 16 Ma (only U–Pb dates are given with 2σ errors), with lower intercepts from about 100 to 300 Ma. Sm–Nd whole-rock and crustal-residence (TDM) dates are 2.3 ± 0.2 Ga. Mafic–felsic layering in the core gneiss is also of Early Proterozoic age. There is no geochronometric evidence for Late Proterozoic or Mesozoic migmatization.Frenchman Cap mantling gneisses, including samples from above the Monashee décollement, have radiogenic Sr and unradiogenic Nd compositions that are not consistent with current inferences of a Late Proterozoic to Paleozoic depositional age. Two intrusive granitic rocks, which cut mantling gneiss, are either Early Proterozoic or Mesozoic–Cenozoic with a Proterozoic Sr isotopic signature acquired by assimilation of core gneiss. One other intrusive studied is probably Paleocene Ladybird granite. The age of the mantling gneiss is not yet consistently resolved.Grand Forks Gneiss Unit I paragneiss gives radiogenic whole-rock Sr, zircon U–Pb upper intercept, and Sm–Nd whole-rock crustal-residence dates of 1.7 ± 0.4 Ga, 1681 ± 3 Ma (2σ, but the apparent high precision is very dependent on the assumption made about the time of Pb loss), and 1.9 ± 0.3 Ga, respectively. Unit II and younger Grand Forks Gneiss units are Late Proterozoic or Phanerozoic. All isotope systems have been considerably reset on a centimetre to metre scale by Mesozoic–Cenozoic regional metamorphism. Grand Forks Sr, Pb, and Nd isotope data are much like those for Spokane area pre-Purcell basement.Vaseaux Formation micaceous schist and gneiss give radiogenic whole-rock Sr, zircon U–Pb upper intercept, and Sm–Nd crustal-residence dates of 2.1 ± 0.6 Ga, 1899 ± 49 Ma (2σ), and 2.2 ± 0.1 Ga, respectively. Hornblende-bearing schist and gneiss contain much less radiogenic Sr and more radiogenic Nd. The latter are either tectonic intercalations of Late Proterozoic to Paleozoic eugeosynclinal rocks or Mesozoic–Cenozoic mixtures of mantle-derived magma and older crustal rock. The Vaseaux Formation paragneiss is similar isotopically to paragneiss in the Frenchman Cap core gneiss. This may indicate a similar age, or that Vaseaux sedimentary rocks could be much younger and isochemically derived from a basement of Frenchman Cap character. The first alternative is favored because the three isotope systems are usually not preserved in unison through sedimentary processes. Sr isotopes, in particular, do not usually preserve a provenance age.In all three areas, late Mesozoic to early Cenozoic metamorphic monazite, hornblende, muscovite, and biotite dates provide a record of cooling from a Cretaceous to Paleocene culmination of regional metamorphism, with particularly rapid cooling during Paleocene to Eocene crustal extension and tectonic unroofing.The localities studied are tectonic windows on structural culminations that expose basement that we infer to be part of North America. Their ages fit the pattern of basement ages established for the stable craton. Their extent is consistent with the reconstruction of compressed miogeoclinal rocks. The eastern half of the Cordilleran region on both sides of the United States – Canada border is underlain by Early Proterozoic basement that was attenuated in Late Proterozoic time, compressed during Mesozoic–Cenozoic orogeny, and finally extended in early Cenozoic collapse of the thickened crust. During Mesozoic–Cenozoic orogeny the sedimentary cover of that basement was pushed approximately 200 km eastward and replaced by allochthonous terranes. The tectonic displacements documented in the southern Canadian Cordillera are truly exceptional.
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SHELLNUTT, J. GREGORY, TUNG-YI LEE, CHIH-CHENG YANG, SHIN-TAI HU, JONG-CHANG WU, KUO-LUNG WANG, and CHING-HUA LO. "Late Permian mafic rocks identified within the Doba basin of southern Chad and their relationship to the boundary of the Saharan Metacraton." Geological Magazine 152, no. 6 (May 6, 2015): 1073–84. http://dx.doi.org/10.1017/s0016756815000217.
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AbstractThe Doba gabbro was collected from an exploration well through the Cretaceous Doba basin of southern Chad. The gabbro is composed mostly of plagioclase, clinopyroxene and Fe–Ti oxide minerals and displays cumulus mineral textures. Whole-rock40Ar–39Ar step-heating geochronology yielded a Late Permian plateau age of 257 ± 1 Ma. The major and trace elemental geochemistry shows that the gabbro is tholeiitic in composition and has trace element ratios (i.e. La/YbN> 7; Sm/YbPM> 3.4; Nb/Y > 1; Zr/Y > 5) indicative of a basaltic melt derived from a garnet-bearing mantle source. The moderately enriched Sr–Nd isotopes (i.e. ISr= 0.70495 to 0.70839; ɛNd(T)= −1.0 to −1.3) fall within the mantle array (i.e. OIB-like) and are similar to other Late Permian plutonic rocks of North-Central Africa (i.e. ISr= 0.7040 to 0.7070). The enriched isotopic composition of the Doba gabbro contrasts with the more depleted compositions of the spatially associated Neoproterozoic post-Pan-African within-plate granites. The contrasting Nd isotope composition between the older within-plate granites and the younger Doba gabbro indicates that different mantle sources produced the rocks and thus may mark the southern boundary of the Saharan Metacraton.
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Ogasawara, Masatsugu, Mayuko Fukuyama, Rehanul Haq Siddiqui, and Ye Zhao. "Origin of the Ordovician Mansehra granite in the NW Himalaya, Pakistan: constraints from Sr–Nd isotopic data, zircon U–Pb age and Hf isotopes." Geological Society, London, Special Publications 481, no. 1 (October 23, 2018): 277–98. http://dx.doi.org/10.1144/sp481.5.
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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.
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Neumann, E. R., J. S. Marsh, C. Y. Galerne, S. Polteau, H. Svensen, and S. Planke. "Co-existing low-Ti and high-Ti dolerites in two large dykes in the Gap Dyke swarm, southeastern Karoo Basin (South Africa)." South African Journal of Geology 123, no. 1 (March 1, 2020): 19–34. http://dx.doi.org/10.25131/sajg.123.0003.
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Abstract This paper presents major, trace element and Sr-Nd isotope data on two large, east-west trending dolerite dykes in the southeastern part of the Karoo Basin, the South Gap (155 km long, ≤275 m wide) and the North Gap (150 km long, ≤190 m wide) dykes. The Gap dykes represent a rare case in the Karoo Large Igneous Province (LIP) where low-Ti (Gap1: <1.7 wt% TiO2, <130 ppm Zr, 200 to 330 ppm Sr, 6 to 17 ppm La, 87Sr/86Sr183: 0.7045 to 0.7075, ɛNd183: +0.31 to -7.5, ΔNb: +0.4 to -0.2) and high-Ti rocks (Gap2: 2.4 to 3.1 wt% TiO2, 110 to 240 ppm Zr, 260 to 390 ppm Sr, 12 to 24 ppm La, 87Sr/86Sr183: 0.7066 to 0.7074, ɛNd183: -3.2 to -4.1, ΔNb: +0.2 to -0.4) alternate along the same dykes. The aim of the study is to unravel the origin and petrogenesis of the two rock groups. The sample groups show the chemical traces of fractional crystallization in increasing concentrations of incompatible trace elements with decreasing MgO, and pivot points where elements such as Ti, Ca, P, and Sc change from trends of increasing to decreasing concentrations with decreasing MgO. Trends of increasing 87Sr/86Sr183 with decreasing ɛNd183 ratios indicate crustal contamination. However, three Gap1 samples from the South Gap dyke with the least enriched Sr-Nd isotope ratios and highest ΔNb may be derived from uncontaminated plume-type mantle melts. Modelling of Sr-Nd isotopes indicate that the Gap1 samples were subjected to assimilation of crustal melts (≤8%) and fractional crystallization in deep crustal magma chambers. There are no restrictions on the mantle source for the Gap2 rocks. However, because both geochemical signatures occur at different localities along the two Gap dykes, we favor a SA (South African) type mantle source for the two groups. The Gap2 rocks appear to have a two-stage assimilation history with one stage in the SCLM (subcontinental lithospheric mantle) or deep crust (decreasing the ɛNd183, increasing the 87Sr/86Sr183 ratios, and inducing the high-Ti character), followed by a second stage of contamination and fractional crystallization in the upper crust (increasing Sr isotope and (Sm/Yb)N ratios, with only minor decrease in ɛNd183).
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Sakhno, V. G., and L. S. Tsurikova. "Isotopic and geochemical features of the genesis of igneous complexes and ore-magmatic systems in the Chukotka sector of the Russian Arctic coast." LITHOSPHERE (Russia) 20, no. 2 (April 25, 2020): 196–211. http://dx.doi.org/10.24930/1681-9004-2020-20-2-196-211.
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Research subject. The isotopic composition (Pb-Pb, Sm-Nd, Rb-Sr, Os/Os, Hf/Hf, 3 He/4 He, etc.) of magmatic complexes and ore-magmatic systems (OMS) of two ore clusters (Kupolsky and Ilirneysky) located in the subpolar Western Chukotka was studied. These ore clusters differ from each other both in their structural position and the age of their magmatic complexes, within which the largest deposits of Au-Ag type are known. Materials and methods. The Pb-Pb, Rb-Sr, SmNd, Re-Os, Lu-Hf, 3 He/4 He, 40Ar/36Ar and sulphur isotopic systems were studied at the VSEGEI centre for isotopic studies (St. Petersburg), as well as at the Institute of Geology, Geochemistry and Ore Deposits (IGEM, Moscow) and the Laboratory of Stable Isotopes of the Far Eastern Geological Institute (FEGI, Vladivostok). Re and Os were measured using an ELEMENT-2 inductively coupled plasma single-collector mass spectrometer. Sulphur isotopic ratios were measured using a Finnigan MAT 253 isotope mass spectrometer. Results and conclusions. On the basis of the isotope-geochemical data obtained, an assumption was made that various deep sources participated in the magma generation, and the differentiated composition of late melts may reflect the melting processes of the crust upper horizons. When comparing the data on the magmatism of the Ilirneysky and Kupolsky ore clusters, a different degree of crustal rock influence on melt generation was revealed. The Kupolsky ore cluster is characterised by a large influence of mantle sources in intraplate magmatism associated with ore formation processes. This is likely to have determined a greater amount of mineralisation in the Kupolsky cluster compared to the Ilirneysky ore cluster.
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Kinnaird, J. A. "Rb-Sr and Nd-Sm isotopes in fluorite related to the granites of the Bushveld Complex." South African Journal of Geology 107, no. 3 (September 1, 2004): 413–30. http://dx.doi.org/10.2113/107.3.413.
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Innocent, Christophe, Annie Michard, Catherine Guerrot, and Bruno Hamelin. "U-Pb zircon age of 548 Ma for the leptynites (high-grade felsic rocks) of the central part of the Maures Massif. Geodynamic significance of the so-called leptyno-amphibolitic complexes of the Variscan belt of western Europe." Bulletin de la Société Géologique de France 174, no. 6 (November 1, 2003): 585–94. http://dx.doi.org/10.2113/174.6.585.
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Abstract U-Pb zircon and Rb-Sr geochronological, and Sm-Nd isotopic studies have been carried out on the so-called leptyno-amphibolitic complex of the central part of the Maures Massif. The emplacement of the protolith of the felsic end-member (« leptynites ») has been dated at 548 Ma, an age much older than those (lower Ordovician) previously obtained on other leptyno-amphibolitic complexes. Rb-Sr data obtained on whole rocks and on mineral separates give an age of 348 Ma for the amphibolite-facies metamorphism. Nd isotopes indicate that the amphibolites display clear-cut mantle-derived signatures, whereas a significant crustal contribution is recorded in the three analyzed felsic facies. One of these acidic terms can be interpreted in terms of a simple mixing between two components, respectively similar to the amphibolites and to the two other felsic samples. These latter involve another mantle source, distinct from that of the amphibolites, and comparable to that of continental alkali basalts. These data indicate that the central part of the Maures Massif and the southern Massif Central were possibly part of the same pre-Variscan structural unit. The lack of evidence for a clear genetic relationship between the respective protoliths of the two end-members of the leptyno-amphibolitic complex raises once again the problem of the geodynamic significance of these formations.
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Sun, Xing Li, Xiao Huang Liu, Jiu Feng Liu, and Bai Nian Sun. "The Age and Origin of the Jinfosi Biotite Granite, North Qilian, NW China: Evidence from U–Pb Zircon Age Data, Geochemistry, and Nd–Sr–Pb Isotopes." Advanced Materials Research 616-618 (December 2012): 3–18. http://dx.doi.org/10.4028/www.scientific.net/amr.616-618.3.
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New geochemistry, Nd–Sr–Pb isotopes and U–Pb zircon data from the Jinfosi Biotite granite provide important constraints on the evolution of the crust in this part of the North Qilian, NW China. The Jinfosi Biotite granite have the following properties: SiO2 > 65%, A/CNK(Molar Al2O3/(CaO + Na2O + K2O) ratios generally > 1.1, Na2O generally < 3.2%, Sm/Nd values between 0.17 and 0.27, and high Rb/Sr values. A chondrite-normalized rare earth element (REE) pattern shows negative Eu anomalies and depletion in heavy REEs. 143Nd/144Nd values are relatively low, and values of εNd(t) and εSr(t) are indicative of continental lithosphere. (87Sr/86Sr)i values are between 0.69952 and 0.70962, corresponding to continental crust mixed with a minor component of mantle material. Values of 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb are 18.9–19.0, 15.59–15.85, and 38.00–and 39.00, respectively, corresponding to S-type collision-related granites. The Jinfosi Biotite granite yield a SHRIMP zircon U–Pb age of 416.7 ± 4.1 Ma. R1–R2 and Rb versus (Yb + Nb) discrimination diagrams indicate that the Jinfosi biotite granite was produced during continental collision following closure of the paleo-North Qilian Ocean.
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He, Xiaohu, Shucheng Tan, Zheng Liu, Zhongjie Bai, Xuance Wang, Yuchao Wang, and Hong Zhong. "Petrogenesis of the Early Cretaceous Aolunhua Adakitic Monzogranite Porphyries, Southern Great Xing’an Range, NE China: Implication for Geodynamic Setting of Mo Mineralization." Minerals 10, no. 4 (April 8, 2020): 332. http://dx.doi.org/10.3390/min10040332.
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This paper reports on whole-rock major- and trace-elemental and Sr–Nd isotopic compositions of the Aolunhua adakitic monzogranite porphyries from the Xilamulun district in the southern Great Xing’an Range, Northeast (NE) China. The high-K calc-alkaline Aolunhua monzogranite porphyries are characterized by high Sr/Y ratios (34.59–91.02), Sr (362–809 ppm), and low Y contents (7.66–10.5 ppm), respectively. These rocks also show slightly enriched Sr and Nd isotopes ((87Sr/86Sr)i = 0.7051–0.7058; εNd(t) = −2.98–0.92), with young two-stage model ages (T2DM = 0.84–1.16 Ga). Such a signature indicates that these rocks were most likely formed by partial melting of juvenile mafic lower crust. Based on equilibrium melting and batch-melting equations, we performed incompatible trace elements modeling. Low FeOT/(FeOT + MgO) values indirectly reflect these adakitic rocks were derived from an oxidizing source related to magnesian granitoids. The decreasing content of TiO2, Fe2O3, Nb/Ta ratio, and moderately negative Eu anomalies suggest that minimal fractionation of Fe–Ti oxides and plagioclase may have occurred in their evolutionary history. The result shows that the Aolunhua adakitic porphyries and coeval adakitic intrusive rocks in this area had not experienced extensive fractional crystallization and were derived from 20%–40% partial melting of lower continental crust, which was composed of ~25%–40% and 5%–20% garnet-bearing amphibolite, respectively. Integrating with rock assemblages and regional tectonic evolutionary history in this regime, high (Sm/Yb)SN (SN—source normalized data, normalized to mafic lower continental crust with Yb = 1.5 ppm and Sm/Yb = 1.87 for continental adakite) and low YbSN ratios suggest that these rocks were generated in an extensional environment related to lithospheric delamination without crustal thickening. The collision between North China and Siberian cratons around 160 Ma blocked the westward movement of the lithosphere as a result of the subduction of Pacific plate, which then led to lithospheric delamination induced by asthenospheric upwelling and underplating. Subsequently, partial melting of mafic lower crust caused by mantle upwelling resulted in the Early Cretaceous magmatic activities of adakitic rocks and associated Mo mineralization in the southern Great Xing’an Range.
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AGASHEV, Aleksey M., Teruo WATANABE, Sergey S. KULIGIN, Nikolai P. POKHILENKO, and Yuji ORIHASHI. "Rb-Sr and Sm-Nd isotopes in garnet pyroxenite xenoliths from Siberian kimberlites: an insight into lithospheric mantle." Journal of Mineralogical and Petrological Sciences 96, no. 1 (2001): 7–18. http://dx.doi.org/10.2465/jmps.96.7.
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Andreasen, Rasmus, and Mukul Sharma. "Mixing and Homogenization in the Early Solar System: Clues from Sr, Ba, Nd, and Sm Isotopes in Meteorites." Astrophysical Journal 665, no. 1 (August 10, 2007): 874–83. http://dx.doi.org/10.1086/518819.
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Zinner, Ernst, and Sachiko Amari. "Presolar grains from meteorites: AGB star matter in the laboratory." Symposium - International Astronomical Union 191 (1999): 59–68. http://dx.doi.org/10.1017/s0074180900202891.
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Primitive meteorites contain dust grains that predate the Solar System, formed in stellar atmospheres and thus represent samples of ancient Stardust. Among the presolar grain types identified so far, corundum (Al2O3) and silicon carbide (SiC) are inferred to originate from AGB stars. Corundum grains carry the signatures of core H burning in their O isotopes and of shell H burning during the AGB phase in the form of extinct 26Al. In presolar SiC, most of which originated from carbon stars, the C and N isotopes and 26Al reflect core and shell H burning and shell He burning. In addition, many elements that carry the isotopic signature of neutron capture have also been measured. Most individual grains show excesses in 29Si and 30Si, but the contribution from neutron capture is only a minor effect and the major effect is due to galactic heterogeneity. Noble gases and the elements Ba, Nd, Sm, and Dy are measured in ”bulk samples”, collections of many grains. Their measured isotopic patterns are well reproduced by models of the s-process in AGB stars. Recently, the isotopic analysis of Sr, Zr and Mo in single SiC grains has been made possible by resonance ionization mass spectrometry. These measurements also point to low-mass AGB stars as the most likely sources. Specifically, large 96Zr depletions in some grains indicate that the 22Ne(α, n) source was not active in the grains' parent stars.
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Huong, Tran Thi, and Nguyen Hoang. "Petrology, geochemistry, and Sr, Nd isotopes of mantle xenolith in Nghia Dan alkaline basalt (West Nghe An): implications for lithospheric mantle characteristics beneath the region." VIETNAM JOURNAL OF EARTH SCIENCES 40, no. 3 (June 4, 2018): 207–27. http://dx.doi.org/10.15625/0866-7187/40/3/12614.
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Study of petrological and geochemical characteristics of mantle peridotite xenoliths in Pliocene alkaline basalt in Nghia Dan (West Nghe An) was carried out. Rock-forming clinopyroxenes, the major trace element containers, were separated from the xenoliths to analyze for major, trace element and Sr-Nd isotopic compositions. The data were interpreted for source geochemical characteristics and geodynamic processes of the lithospheric mantle beneath the region. The peridotite xenoliths being mostly spinel-lherzolites in composition, are residual entities having been produced following partial melting events of ultramafic rocks in the asthenosphere. They are depleted in trace element abundance and Sr-Nd isotopic composition. Some are even more depleted as compared to mid-ocean ridge mantle xenoliths. Modelled calculation based on trace element abundances and their corresponding solid/liquid distribution coefficients showed that the Nghia Dan mantle xenoliths may be produced of melting degrees from 8 to 12%. Applying various methods for two-pyroxene temperature- pressure estimates, the Nghia Dan mantle xenoliths show ranges of crystallization temperature and pressure, respectively, of 1010-1044°C and 13-14.2 kbar, roughly about 43km. A geotherm constructed for the mantle xenoliths showed a higher geothermal gradient as compared to that of in the western Highlands (Vietnam) and a conductive model, implying a thermal perturbation under the region. The calculated Sm-Nd model ages for the clinopyroxenes yielded 127 and 122 Ma. 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Valui, G. A., and E. Yu Moskalenko. "First data on the isotopes of Sm—Nd and Sr for Cretaceous—Paleogene granitoids of primors’e and some problems of their genesis." Doklady Earth Sciences 435, no. 1 (November 2010): 1511–14. http://dx.doi.org/10.1134/s1028334x1011022x.
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Tistl, M., K. P. Burgath, A. Höhndorf, H. Kreuzer, R. Muñoz, and R. Salinas. "Origin and emplacement of Tertiary ultramafic complexes in northwest Colombia: Evidence from geochemistry and KAr, SmNd and RbSr isotopes." Earth and Planetary Science Letters 126, no. 1-3 (August 1994): 41–59. http://dx.doi.org/10.1016/0012-821x(94)90241-0.
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Sharma, Pranjal, Ankit Agarwal, and Bhawna Chaudhary. "Quantum Genetic Terrain Algorithm (Q-GTA): A Technique to Study the Evolution of the Earth Using Quantum Genetic Algorithm." Proceedings 46, no. 1 (November 17, 2019): 26. http://dx.doi.org/10.3390/ecea-5-06685.
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In recent years, geologists have put in a lot of effort trying to study the evolution of Earth using different techniques studying rocks, gases, and water at different channels like mantle, lithosphere, and atmosphere. Some of the methods include estimation of heat flux between the atmosphere and sea ice, modeling global temperature changes, and groundwater monitoring networks. That being said, algorithms involving the study of Earth’s evolution have been a debated topic for decades. In addition, there is distinct research on the mantle, lithosphere, and atmosphere using isotopic fractionation, which this paper will take into consideration to form genes at the former stage. This factor of isotopic fractionation could be molded in QGA to study the Earth’s evolution. We combined these factors because the gases containing these isotopes move from mantle to lithosphere or atmosphere through gaps or volcanic eruptions contributing to it. We are likely to use the Rb/Sr and Sm/Nd ratios to study the evolution of these channels. This paper, in general, provides the idea of gathering some information about temperature changes by using isotopic ratios as chromosomes, in QGA the chromosomes depict the characteristic of a generation. Here these ratios depict the temperature characteristic and other steps of QGA would be molded to study these ratios in the form of temperature changes, which would further signify the evolution of Earth based on the study that temperature changes with the change in isotopic ratios. This paper will collect these distinct studies and embed them into an upgraded quantum genetic algorithm called Quantum Genetic Terrain Algorithm or Quantum GTA.
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Shchukina, Elena V., Aleksey M. Agashev, Natalia G. Soloshenko, Mariya V. Streletskaya, and Dmitry A. Zedgenizov. "Origin of V. Grib pipe eclogites (Arkhangelsk region, NW Russia): geochemistry, Sm-Nd and Rb-Sr isotopes and relation to regional Precambrian tectonics." Mineralogy and Petrology 113, no. 5 (July 16, 2019): 593–612. http://dx.doi.org/10.1007/s00710-019-00679-7.
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Sun, Beilei, Joan S. Esterle, Grant K. W. Dawson, Sandra Rodrigues, Rhiannon Lord, Sue D. Golding, Yuexing Feng, and Fangui Zeng. "Evidence for an Early-Middle Jurassic fluid event constrained by Sm–Nd, Sr isotopes, rare earth elements and yttrium in the Bowen Basin, Australia." International Journal of Coal Geology 224 (May 2020): 103478. http://dx.doi.org/10.1016/j.coal.2020.103478.
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Xu, Rong, Ming-Guo Deng, Wen-Chang Li, Chun-Kit Lai, Khin Zaw, Zhi-Wu Gao, Yu-Hong Chen, Chun-Hui Niu, and Gang Liang. "Origin of the giant Luziyuan Zn-Pb-Fe(-Cu) distal skarn deposit, Baoshan block, SE Tibet: Constraints from Pb–Sr isotopes, calcite C–O isotopes, trace elements and Sm–Nd dating." Journal of Asian Earth Sciences 205 (January 2021): 104587. http://dx.doi.org/10.1016/j.jseaes.2020.104587.
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Hollings, Pete, Adam Richardson, Robert A. Creaser, and James M. Franklin. "Radiogenic isotope characteristics of the Mesoproterozoic intrusive rocks of the Nipigon Embayment, northwestern Ontario." Canadian Journal of Earth Sciences 44, no. 8 (August 1, 2007): 1111–29. http://dx.doi.org/10.1139/e06-128.
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The ca. 1110–1120 Ma diabase sills of the Nipigon Embayment represent the oldest phase of the Midcontinent Rift recognized to date. The sills can be subdivided into five geochemically distinct suites: Nipigon, McIntyre, Inspiration, Shillabeer, and Jackfish. Sm–Nd, Rb–Sr, and Pb–Pb isotope data for the sills can be used to evaluate the source regions and emplacement histories of these sills. The εNdT values for all the sill suites are consistently negative (–0.5 to –6.6) but show coherent variations both within and between suites. The negative εNdT values can be interpreted as the result of contamination of a plume-related mantle source by older crustal material. The initial strontium (Sri) values (0.7032–0.7068) for the sills indicate that at least two distinct contaminants are required: (1) a source with strongly negative εNdT and lower Sri, likely Archean metasediment or granite, and (2) one with elevated Sri, likely sedimentary rocks of the Proterozoic Sibley Group. The Pb data for the Nipigon and Inspiration sills form distinct linear arrays consistent with variable contamination of a source comparable to that of other igneous suites of the Midcontinent Rift. The radiogenic isotopes preserve a complex contamination history best interpreted as the result of <5% contamination by a variety of Archean and Proterozoic sources. The ultramafic Jackfish sill shows the least evidence of contamination and is interpreted to have been emplaced along a crustal-scale fault with little interaction with crustal material. In contrast, the other sill suites have undergone complex contamination histories requiring variable crustal residence times and assimilation of material both at depth in large magma chambers and during emplacement.
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Yuan, Mao-Wen, Lin Li, Sheng-Rong Li, M. Santosh, Cheng-Lu Li, Masroor Alam, and Zeng-Qian Hou. "Bitumen Sm-Nd, pyrite Rb-Sr and zircon U-Pb isotopes constrain timing of ore formation and hydrocarbon deposition in the Erdaokan Ag-Pb-Zn deposit, NE China." Ore Geology Reviews 134 (July 2021): 104161. http://dx.doi.org/10.1016/j.oregeorev.2021.104161.
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Rickers, Karen, Klaus Mezger, and Michael M. Raith. "Evolution of the Continental Crust in the Proterozoic Eastern Ghats Belt, India and new constraints for Rodinia reconstruction: implications from Sm–Nd, Rb–Sr and Pb–Pb isotopes." Precambrian Research 112, no. 3-4 (December 2001): 183–210. http://dx.doi.org/10.1016/s0301-9268(01)00146-2.
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Chervyakovskaya, M. V., and V. S. Chervyakovskiy. "Determination of Sm/Nd and Sr isotopic composition using an ICP-MS Neptune Plus equipped with an NWR 213 attachment for laser ablation." LITHOSPHERE (Russia) 21, no. 5 (October 31, 2021): 712–23. http://dx.doi.org/10.24930/1681-9004-2021-21-5-712-723.
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Research subject. The Sm/Nd isotope system was investigated using inter-laboratory natural samples of apatite, titanite, allanite, monazite, as well as intra-laboratory samples of apatite (from carbonatites, Ilmenogorsk massif, Ural), monazite (from pegmatites of the Aduy granite massif and its framing, Middle Urals) and titanite (from calcite veins, Saranov skoye chromite deposit, Middle Urals and from alkaline pegmatite, Shpat mine, Vishnevy mountains, South Urals). The Sr isotope system was investigated using inter-laboratory natural apatite samples and intra-laboratory apatite samples (from the apatite-carbonate vein, Slyudyanogorskoe deposit, Irkutsk region and from carbonatites, Ilmenogorsk massif, Ural).Methods. The research was carried using a Neptune Plus multicollector mass spectrometer with inductively coupled plasma (ThermoFisher) equipped with an NWR 213 (ESI) laser ablation attachment, located in a room of ISO class 7 at the “Geoanalyst” Center for Collective Use (IGG Ural Branch of the Russian Academy of Sciences, Ekaterinburg). Results. The article describes methodological approaches for studying Sm/Nd and Sr isotope systems in natural phosphate and silicate minerals by inductively coupled plasma mass spectrometry with laser ablation, implemented on the equipment of the Center for Collective Use “Geoanalyst” (IGG Ural Branch of the Russian Academy of Sciences, Ekaterinburg). A comparative analysis of the obtained results with those reported in literature showed their satisfactory agreement. The developed analytical approaches were used to study apatite samples (analysis of the Sr isotope system) and those of apatite, monazite, titanite (analysis of the Sr isotope system). Conclusions. The developed approaches to the analysis of Sm/Nd and Sr isotopic systems can be recommended for investigating such minerals, as apatite, titanite, allanite, monazite (analysis of the Sm/Nd isotope system); apatite (analysis of the Sr isotope system). The achieved analysis errors allow the results to be used for interpreting various geochemical processes.
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Dempsey, C. S., A. N. Halliday, and I. G. Meighan. "Combined Sm-Nd and Rb-Sr isotope systematics in the Donegal granitoids and their petrogenetic implications." Geological Magazine 127, no. 1 (January 1990): 75–80. http://dx.doi.org/10.1017/s0016756800014175.
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AbstractThe metaluminous to peraluminous granitoids of the Donegal batholith, northwest Ireland, were emplaced at c. 400 Ma into greenschist-amphibolite facies metasediments of the Dalradian Supergroup. Sm-Nd and Rb-Sr isotopic data are provided for eleven granitoid samples from six of the plutons and one specimen from the northeast granodiorite pluton of the Newry complex, Co. Down; the Donegal results reveal essentially similar initial Sr isotope ratios (0.7051–0.7068) but highly variable initial eNd values, −1.2 to −8.3 (and −0.5 for Newry). Certain granitoids have distinctive Nd isotopic compositions characteristic of the involvement of old, LREE-enriched continental crust in some cases or young crust and/or mantle-derived magmas in others. The Nd and Sr isotopic variations can be explained by a variety of mixing hypotheses.
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Larsen, Lotte Melchior, and Marie-Claude Williamson. "Depleted and ultradepleted basalt and picrite in the Davis Strait: Paleocene volcanism associated with a transform continental margin." Geological Magazine 157, no. 12 (April 1, 2020): 1983–2003. http://dx.doi.org/10.1017/s0016756820000175.
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AbstractVolcanic rocks from the Davis Strait were studied to elucidate the tectonomagmatic processes during rifting and the start of seafloor spreading, and the formation of the Ungava transform zone between Canada and Greenland. The rocks are from the wells Hekja O-71, Gjoa G-37, Nukik-2 and Hellefisk-1, and from dredges on the northern Davis Strait High. Ages range from Danian to Thanetian (dinocyst palynozones P2 to P5, 62.5–57.2 Ma). The rocks are predominantly basaltic, but include picrites on the Davis Strait High. Calculated mantle potential temperatures for the Davis Strait High are c. 1500°C, suggesting the volume of magma generated was large; this is consistent with geophysical evidence for magmatic underplating in the region. The rare earth element patterns indicate residual mantle lithologies of spinel peridotite and, together with Sr–Nd isotopes, indicate melting beneath regionally extensive, depleted asthenosphere beneath a lithosphere of thickness similar to, or thinner than, beneath Baffin Island and distinctly thinner than beneath West Greenland. Some sites include basalts with more enriched compositions. Depleted and enriched basalts in the Hellefisk well show contemporaneous melting of depleted and enriched mantle components in the asthenosphere. The Hekja and Davis Strait High basalts and picrites have unique, ultradepleted compositions with (La/Sm)N < 0.5, (Tb/Lu)N < 1 and Nb/Zr = 0.013–0.027. We interpret these compositions as a product of the melting regime within the Ungava transform zone, where the melting column would be steep-sided in cross-section and not triangular as expected at normal spreading ridges. Magmatism along the transform stopped when the tectonic regime changed from transtension to transpression during earliest Eocene time.
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Collerson, Kenneth D., Malcolm T. McCulloch, and Allan P. Nutman. "Sr and Nd isotope systematics of polymetamorphic Archean gneisses from southern West Greenland and northern Labrador." Canadian Journal of Earth Sciences 26, no. 3 (March 1, 1989): 446–66. http://dx.doi.org/10.1139/e89-039.
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Sr and Nd isotopic data for middle to late Archean polymetamorphic felsic gneisses from localities in the Nuuk area, West Greenland, are compared and contrasted with new isotopic results for early Archean Amîtsoq gneisses and with data for isotopically reworked Kiyuktok gneisses from the Saglek area, Labrador. Sr isotopic data for individual suites of felsic gneisses record the time-integrated effect of variable Rb–Sr fractionation during prograde and retrograde events as well as the effect of source inhomogeneity.Contrasting petrologic and Sr–Nd isotopic characteristics are the result of differences in level of exposure, caused partially by juxtaposition of terranes of different metamorphic character by movement on ductile shear zones and post-shearing folding deformation. Sm–Nd systematics of felsic gneisses from Nordafar, Ikerasakitsup akornga, Tinissaq, and Kangimut sammisoq – Qasigianguit define a geologically meaningless ca. 3280 Ma Nd "isochron", which is the result of mixing of samples from unrelated suites and the effect of open-system behaviour. Gneisses lying on this pseudoisochron were variably affected by ca. 2800–2900 Ma prograde granulite-facies metamorphism and structurally controlled retrogression under amphibolite- to greenschist-facies conditions.The study shows that Sr–Nd isotope systematics of geologically identifiable units may be modified by open-system behaviour during prograde and retrograde metamorphism. Isotopic data from gneiss complexes metamorphosed under granulite-facies conditions may therefore yield equivocal information concerning isochron interpretation, significance of model ages, and estimates of crustal residence time.
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Nedosekova, I. L., V. A. Koroteev, T. B. Bayanova, P. A. Serov, V. I. Popova, and M. V. Chervyakovskaya. "On the age of pyrochlore carbonatites from the Ilmeno-Vishnevogorsky Alkaline Complex, the Southern Urals (insights from Rb-Sr and Sm-Nd isotopic data)." LITHOSPHERE (Russia) 20, no. 4 (August 31, 2020): 486–98. http://dx.doi.org/10.24930/1681-9004-2020-20-4-486-498.
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Research subject. In this research, we carried out Sm-Nd- и Rb-Sr-dating of pyrochlore carbonatite from the Vishnevogorsky niobium deposit, Ilmeno-Vishnevogorsky Alkaline Complex, Southern Urals. IVC is located in the Ural fold region and is a carbonatite complex of the linear type. Rare metal (Nb-Zr-TR) deposits and occurrences are related to IVC. The age and the duration of IVC deposits formation remains a matter of debate. To determine the age of IVC carbonatites and related niobium ore, we measured Sm-Nd and Rb-Sr isotopic compositions and concentrations of the elements in the minerals (pyrochlore, calcite, apatite, biotite) and bulk sample of pyrochlore carbonatite. Materials and methods. The Sm and Nd isotopic compositions and concentrations were determined on a Finnigan MAT-262L (RPQ) seven-collector mass spectrometer in the static regime at the Geological Institute of the Kola Scientific Center, Apatity, Russia. The Sr and Rb isotopic compositions and concentrations were determined on thermos-ionization mass spectrometer Triton Plus (“Geoanalitik”, IGG UD RAN, Ekaterinburg, Russia). Results. Age of pyrochlore carbonatites from ore zone 140 (Vishnevogorsky deposit, IVC) defined by Sm-Nd and Rb-Sr isotopic methods. Mineral Sm-Nd-isochron (5 points) indicated age 229 ± 16 Ma, mineral Rb-Sr-isochron (5 points) showed similar age 250.5 ± 1.2 Ma. Conclusions. Results Sm-Nd и Rb-Sr dating indicate that the pyrochlore сarbonatites of ore zone 140 crystallized ≈ 250 Ma ago, at the stage of the postcollisional extension, possibly, in connection with exhumation complex, which was accompanied by decompression, partial melting of rocks, involving fluids, dissolution and precipitation of Ordovician-Silurian alkaline-carbonatitе complex. Thus, the formation of the IVC carbonatites and related Nb-ore, which began in Silurian (S), continued in Permian (P) and Triassic (T1-2) and was associated with the post-collision stage of tectonic activity in the Ural Fold Belt.
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Castorina, F., F. Stoppa, A. Cundari, and M. Barbieri. "An enriched mantle source for Italy's melilitite-carbonatite association as inferred by its Nd-Sr isotope signature." Mineralogical Magazine 64, no. 4 (August 2000): 625–39. http://dx.doi.org/10.1180/002646100549652.
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AbstractNew Sr-Nd isotope data were obtained from Late Pleistocene carbonatite-kamafugite associations from the Umbria-Latium Ultra-Alkaline District of Italy (ULUD) with the aim of constraining their origin and possible mantle source(s). This is relevant to the origin and evolution of ultrapotassic (K/Na ≫2) and associated rocks generally, notably the occurrences from Ugandan kamafugites,Western Australian lamproites and South African orangeites. The selected ULUD samples yielded 87Sr/86Sr and 143Nd/144Nd ranging from 0.7100 to 0.7112 and from 0.5119 to 0.5121 respectively, similar to cratonic potassic volcanic rocks with higher Rb/Sr and lower Sm/Nd ratios than Bulk Earth. Silicate and carbonate fractions separated from melilitite are in isotopic equilibrium, supporting the view that they are cogenetic. The ULUD carbonatites yielded the highest radiogenic Sr so far reported for carbonatites. In contrast, sedimentary limestones from ULUD basement formations are lower in radiogenic Sr, i.e. 87Sr/86Sr = 0.70745–0.70735. The variation trend of ULUD isotopic compositions is similar to that reported for Ugandan kamafugites and Western Australian lamproites and overlaps the values for South African orangeites in the εSr-εNd diagram. A poor correlation between Sr/Nd and 87Sr/86Sr ratios in ULUD rocks is inconsistent with a mantle source generated by subduction-driven processes, while the negligible Sr and LREE in sedimentary limestones from the ULUD region fail to account for a hypothetical limestone assimilation process. The Nd model ages of 1.5–1.9 Ga have been inferred for a possible metasomatic event, allowing further radiogenic evolution of the source, a process which may have occurred in isolation until eruption time. While the origin of this component remains speculative, the Sr-Nd isotope trend is consistent with a simple mixing process involving an OIB-type mantle and a component with low εNd and high εSr.
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Carlson, Richard W., Lars E. Borg, Amy M. Gaffney, and Maud Boyet. "Rb-Sr, Sm-Nd and Lu-Hf isotope systematics of the lunar Mg-suite: the age of the lunar crust and its relation to the time of Moon formation." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 372, no. 2024 (September 13, 2014): 20130246. http://dx.doi.org/10.1098/rsta.2013.0246.
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New Rb-Sr, 146,147 Sm- 142,143 Nd and Lu-Hf isotopic analyses of Mg-suite lunar crustal rocks 67667, 76335, 77215 and 78238, including an internal isochron for norite 77215, were undertaken to better define the time and duration of lunar crust formation and the history of the source materials of the Mg-suite. Isochron ages determined in this study for 77215 are: Rb-Sr=4450±270 Ma, 147 Sm- 143 Nd=4283±23 Ma and Lu-Hf=4421±68 Ma. The data define an initial 146 Sm/ 144 Sm ratio of 0.00193±0.00092 corresponding to ages between 4348 and 4413 Ma depending on the half-life and initial abundance used for 146 Sm. The initial Nd and Hf isotopic compositions of all samples indicate a source region with slight enrichment in the incompatible elements in accord with previous suggestions that the Mg-suite crustal rocks contain a component of KREEP. The Sm/Nd— 142 Nd/ 144 Nd correlation shown by both ferroan anorthosite and Mg-suite rocks is coincident with the trend defined by mare and KREEP basalts, the slope of which corresponds to ages between 4.35 and 4.45 Ga. These data, along with similar ages for various early Earth differentiation events, are in accord with the model of lunar formation via giant impact into Earth at ca 4.4 Ga.
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Kalsbeek, F. "Use of Rb-Sr isotope data to constrain the time of deposition of Precambrian metasediments: an example from Hamborgerland, West Greenland." Rapport Grønlands Geologiske Undersøgelse 159 (January 1, 1993): 95–100. http://dx.doi.org/10.34194/rapggu.v159.8216.
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In high-grade metamorphic terrains it is often not possible to determine the relative age of metasedimentary units by field investigation. However, the time of deposition of the original sediment can be constrained by consideration of the Sr-isotopic evolution of the rocks on the scale of an outcrop. An outline of the method is given, and Rb-Sr data for high-grade (granulite facies) metasediments from HamborgerIand, West Greenland, are discussed as an example. Sm-Nd model age data indicate that these rocks were derived by erosion of a 3000–3200 Ma basement. Deposition took place not long before 2700 Ma ago, and closure of the Rb-Sr isotope system after high-grade metamorphism occurred at about 2600 Ma.
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Zhang, Zhiyuan, Guiqing Xie, Jingwen Mao, Wengang Liu, Paul Olin, and Wei Li. "Sm-Nd Dating and In-Situ LA-ICP-MS Trace Element Analyses of Scheelite from the Longshan Sb-Au Deposit, Xiangzhong Metallogenic Province, South China." Minerals 9, no. 2 (January 30, 2019): 87. http://dx.doi.org/10.3390/min9020087.
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Longshan is an important Sb-Au ore deposit (3.7 Mt @4.5 wt. % Sb and 4.6 g/t Au) in the Xiangzhong metallogenic province (XZMP), South China. In the present work, trace element composition, Sm-Nd isotope dating, and Sr isotope of scheelite from the Longshan Sb-Au deposit are used to constrain the genesis of the deposit. Based on mineral assemblages and geological characteristics, two types of scheelites can be distinguished (Sch1 and Sch2). Sch1 is granular and cemented by stibnite, while Sch2 is commonly present in stibnite, pyrite, calcite, and quartz veins, indicating that Sch2 is later than Sch1. The Sm-Nd isochron age defined by Sch1 is 210 ± 2 Ma (MSWD = 1.0, n = 4). This age is interpreted as the age of Sb-Au mineralization and overlaps with the 201–228 Ma granitic rocks in the XZMP. Sch1 exhibits high ΣREE + Y contents (43.5 to 104 ppm), low Sr values (2687 to 6318 ppm, average of 4018 ppm), and a narrow range of 87Sr/86Sr values (0.7209 to 0.7210, average of 0.7209). In contrast, the elevated Sr abundance (4525 to 11,040 ppm, average of 6874 ppm) and wide 87Sr/86Sr ratios (0.7209 to 0.7228, average of 0.7214) in Sch2 were possibly caused by fluid-rock interaction mixing with Sr-enriched basement rocks. Sulfides have a narrow range of δ34S values of −1.8‰ to 3.2‰, with an average value of 1.1‰ (n = 7). Geochronological, geochemical and isotopic data suggest that the Longshan Sb-Au deposit is possible genetically related to the Late Triassic granitic intrusion in the XZMP.
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Goodrich, Cyrena Anne, P. Jonathan Patchett, Gunter W. Lugmair, and Michael J. Drake. "Sm-Nd and Rb-Sr isotopic systematics of ureilites." Geochimica et Cosmochimica Acta 55, no. 3 (March 1991): 829–48. http://dx.doi.org/10.1016/0016-7037(91)90345-6.
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THOMAS, R. J., F. HENJES-KUNST, and J. JACOBS. "Pre-lamprophyre mafic dykes of the Cape Meredith Complex, West Falkland." Geological Magazine 135, no. 4 (July 1998): 495–500. http://dx.doi.org/10.1017/s0016756898001216.
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New field, petrographic, geochemical and Rb–Sr/Sm–Nd isotope data are presented from early mafic dykes which intrude the Mesoproterozoic Cape Meredith Complex, West Falkland. The dykes, which have been previously regarded as being Ordovician in age, are seen in the field to cut a suite of lamprophyre sheets. New K–Ar data from biotite separates from two lamprophyres suggest a miminum age of emplacement of ∼520 Ma, confirming previous work. The Rb–Sr and Sm–Nd analyses of the pre-lamprophyre mafic dykes suggests that they were probably intruded during the late Neoproterozoic at ∼600 Ma. This new data has considerable implications for the previously published estimates of the longevity of intracontinental extension events in this part of Gondwana.
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Bast, R., E. E. Scherer, P. Sprung, M. Fischer-Gödde, A. Stracke, and K. Mezger. "Correction: A rapid and efficient ion-exchange chromatography for Lu–Hf, Sm–Nd, and Rb–Sr geochronology and the routine isotope analysis of sub-ng amounts of Hf by MC-ICP-MS." Journal of Analytical Atomic Spectrometry 30, no. 12 (2015): 2554. http://dx.doi.org/10.1039/c5ja90054a.
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Correction for ‘A rapid and efficient ion-exchange chromatography for Lu–Hf, Sm–Nd, and Rb–Sr geochronology and the routine isotope analysis of sub-ng amounts of Hf by MC-ICP-MS’ by R. Bast et al., J. Anal. At. Spectrom., 2015, 30, 2323–2333.
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Burwash, R. A., J. Krupicka, A. R. Basu, and P. A. Wagner. "Resetting of Nd and Sr whole-rock isochrons from polymetamorphic granulites, northeastern Alberta." Canadian Journal of Earth Sciences 22, no. 7 (July 1, 1985): 992–1000. http://dx.doi.org/10.1139/e85-104.
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At Mountain Rapids on the Slave River, mafic xenoliths are enclosed by a granodiorite host, which is, in turn, surrounded by a granitic migmatite complex. The mafic and granodioritic rocks are both metamorphosed to the hornblende granulite facies, and the migmatite has been metamorphosed to the upper amphibolite facies. The banding of the mafic granulites is truncated by sharply defined boundaries with the felsic granulites. The felsic granulites contain K-feldspar, the mafic rocks almost none. The mineral assemblages are otherwise identical: plagioclase–hypersthene–quartz–biotite–magnetite.A whole-rock Sm–Nd isochron of one felsic and six mafic granulites gives 2436 ± 44 Ma [Formula: see text]. This time is significantly younger than the Sm–Nd model ages. The same mafic samples give a Rb–Sr age of 1898 ± 5 Ma. These are interpreted as the times of reequilibration and closure of the Rb–Sr isotopic systems within the Mountain Rapids Granulite enclave. From cordierite–garnet barometry the indicated pressure of the younger event is 5.5 ± 0.7 kbar (550 ± 70 MPa). By analogy with hornblende granulite assemblages elsewhere, the older event probably occurred in the intermediate crust (~25–30 km depth). This event apparently effectively reset the Sm–Nd isotopic system; subsequent cooling closed it. Once established this system withstood the later, lower pressure event that reset the Rb–Sr geochronometer on a regional scale.
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ZHU, YONGFENG, BO CHEN, and TIAN QIU. "Geology and geochemistry of the Baijiantan–Baikouquan ophiolitic mélanges: implications for geological evolution of west Junggar, Xinjiang, NW China." Geological Magazine 152, no. 1 (April 23, 2014): 41–69. http://dx.doi.org/10.1017/s0016756814000168.
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AbstractWe report two newly identified Ordovician ophiolite belts in west Junggar, NW China: Tajin–Tarbahatai–Kujibai–Honguleleng (TTKH) and Tangbale–Baijiantan–Baikouquan (TBB) ophiolitic belts. These two ophiolitic belts provide constraints for the Palaeozoic reconstruction of Central Asia and the geological evolution of this region. The TTKH and TBB ophiolitic belts are dismembered parts of different ophiolitic belts which represent relics of Ordovician oceanic floor; they subducted to the north under the Chingiz–Tarbahatai arc and to the south under the Junggar plate, respectively. The Baijiantan–Baikouquan ophiolite mélanges comprise the major part of the TBB. Flat rare Earth element (REE) patterns with positive Eu anomalies and insignificant depletion of high-field-strength elements (HFSE) relative to melts of primitive mantle suggest a mid-ocean-ridge basalt (MORB) origin for the metagabbro. Lherzolite samples define a Sm–Nd isotopic isochron with age of 474 Ma andɛNd(t)of +8.9. Lherzolite samples with positiveɛNd(t)values of +8.8 to +9.1 and initial87Sr/86Sr ratios of 0.7037–0.7040 are rather homogeneous in Sr–Nd isotopic composition, whereas metagabbro samples show wider Sr–Nd isotopic compositional ranges withɛNd(t)of +5.9 to +11.0. The Sm–Nd isotopic isochron age (c.380 Ma) for garnet amphibolite samples, consistent with a zircon U–Pb age (c.385 Ma) for metagabbro, represents a magmatic event prior to subduction. Thermodynamic calculations for garnet amphibolite yield a clockwise pressure–temperature path with peak metamorphic condition ofc.15 kbar and 520–560°C at 342 Ma, indicating a subduction-channel setting. The Rb–Sr isochron ages (335 Ma, 333 Ma) for metagabbro represent a metamorphic event during exhumation.
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Dickin, A. P., and D. R. Bowes. "Isotopic evidence for the extent of early Proterozoic basement in Scotland and northwest Ireland." Geological Magazine 128, no. 4 (July 1991): 385–88. http://dx.doi.org/10.1017/s0016756800017647.
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AbstractTightly clustered Sm–Nd model ages, with an average of 1.96±0.02Ga, for the gneiss complex of Inishtrahull indicate coeval development with the earlyProterozoic gneiss terrane of Islay. The extent of this terrane, largely beneath the Dalradian Supergroup, is argued to be 100×600 km, from northeast Scotland to western Ireland. This is based on the distribution of dated basement in conjunction with Pb, Sr and Nd isotope systematics and inherited zircons in Caledonian granites of the region.
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Pagel, Maurice, Annie Michard, Martine Juteau, and Laurent Turpin. "Sm–Nd, Pb–Pb, and Rb–Sr systematics of the basement in the Cigar Lake area, Saskatchewan, Canada." Canadian Journal of Earth Sciences 30, no. 4 (April 1, 1993): 731–42. http://dx.doi.org/10.1139/e93-059.
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The Sm–Nd, Pb–Pb, and Rb–Sr isotope geochemistry of graphitic metapelitic gneisses and their altered equivalents from the Cigar Lake area (Saskatchewan, Canada) has been investigated. Some granitic gneisses were also analyzed for Pb–Pb and Rb–Sr. Sm–Nd data show that the metapelitic gneisses are composed of detritus from heterogeneous, mainly mantle-derived Archean rocks (2.5–2.6 Ga) and that the Sm–Nd system has not been significantly perturbed during subsequent alteration and metamorphic events. The Pb–Pb age for samples of the less altered graphitic metapelitic gneisses is 1.77 ± 0.03 Ga. The crustal common Pb is located on the Pb–Pb isochron, but there are different zones with high and variable U/Pb ratios (μ = 15–280). The Pb–Pb age for the granitic gneisses is 1.79 ± 0.11 Ma. The Pb isotope data show that there has been no major uranium redistribution in the basement after the Hudsonian orogeny. However, there has been a strong perturbation of the U–Pb system in the regolithic zone beneath the Athabasca cover. In some samples, uranium was added during the mineralizing event. The Rb–Sr system in the graphitic metapelitic gneisses was also affected.The 87Sr/86Sr ratio in pitchblende is 0.709. At 1.3 Ga, there is a strong contrast between the 87Sr/86Sr ratio in the Athabasca sandstones (0.706–0.710) and the 87Sr/86Sr ratio in the metapelitic gneisses from the basement (0.725–0.775). The upper zone of the regolith is characterized by a low 87Sr/86Sr ratio (0.705–0.707). The Pb–Pb and Rb–Sr data are consistent with the circulation of a fluid with a low 87Sr/86Sr ratio, derived from the sedimentary cover; this fluid passed through the most permeable zones of the basement rocks, especially the regolith. The mineralizing fluid had a 87Sr/86Sr value typical of a fluid in equilibrium with the Athabasca sandstones.
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Steshenko, Ekaterina N., Tamara B. Bayanova, and Pavel A. Serov. "The Paleoproterozoic Kandalaksha-Kolvitsa Gabbro-Anorthosite Complex (Fennoscandian Shield): New U–Pb, Sm–Nd, and Nd–Sr (ID-TIMS) Isotope Data on the Age of Formation, Metamorphism, and Geochemical Features of Zircon (LA-ICP-MS)." Minerals 10, no. 3 (March 10, 2020): 254. http://dx.doi.org/10.3390/min10030254.
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The paper provides new U–Pb, Sm–Nd, and Nd–Sr isotope-geochronological data on rocks of the Paleoproterozoic Kandalaksha-Kolvitsa gabbro-anorthosite complex. Rare earth element (REE) contents in zircons from basic rock varieties of the Kandalaksha-Kolvitsa area were analyzed in situ using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Plots of REE distribution were constructed, confirming the magmatic origin of zircon. Temperatures of zircon crystallization were estimated using a Ti-in-zircon geochronometer. The U–Pb method with a 205Pb artificial tracer was first applied to date single zircon grains (2448 ± 5 Ma) from metagabbro of the Kolvitsa massif. The U–Pb analysis of zircon from anorthosites of the Kandalaksha massif dated the early stage of the granulite metamorphism at 2230 ± 10 Ma. The Sm–Nd isotope age was estimated on metamorphic minerals (apatite, garnet, sulfides) and whole rock at 1985 ± 17 Ma (granulite metamorphism) for the Kolvitsa massif and at 1887 ± 37 Ma (high-temperature metasomatic transformations) and 1692 ± 71 Ma (regional fluid reworking) for the Kandalaksha massif. The Sm–Nd model age of metagabbro was 3.3 Ga with a negative value of εNd = 4.6, which corresponds with either processes of crustal contamination or primary enriched mantle reservoir of primary magmas.
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Jahn, Bor-ming, Fuyuan Wu, and Bin Chen. "Granitoids of the Central Asian Orogenic Belt and continental growth in the Phanerozoic." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 91, no. 1-2 (2000): 181–93. http://dx.doi.org/10.1017/s0263593300007367.
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The Central Asian Orogenic Belt (CAOB), also known as the Altaid Tectonic Collage, is characterised by a vast distribution of Paleozoic and Mesozoic granitic intrusions. The granitoids have a wide range of compositions and roughly show a temporal evolution from calcalkaline to alkaline to peralkaline series. The emplacement times for most granitic plutons fall between 500 Ma and 100 Ma, but only a small proportion of plutons have been precisely dated. The Nd-Sr isotopic compositions of these granitoids suggest their juvenile characteristics, hence implying a massive addition of new continental crust in the Phanerozoic. In this paper we document the available isotopic data to support this conclusion.Most Phanerozoic granitoids of Central Asia are characterised by low initial Sr isotopic ratios, positive εNd(T) values and young Sm—Nd model ages (TDM) of 300-1200 Ma. This is in strong contrast with the coeval granitoids emplaced in the European Caledonides and Hercynides. The isotope data indicate their ‘juvenile’ character and suggest their derivation from source rocks or magmas separated shortly before from the upper mantle. Granitoids with negative εNd(T) values also exist, but they occur in the environs of Precambrian microcontinental blocks and their isotope compositions may reflect contamination by the older crust in the magma generation processes.The evolution of the CAOB is probably related to accretion of young arc complexes and old terranes (microcontinents). However, the emplacement of large volumes of post-tectonic granites requires another mechanism, probably through a series of processes including underplating of massive basaltic magma, intercalation of basaltic magma with lower crustal granulites, partial melting of the mixed lithologic assemblages leading to generation of granitic liquids, followed by extensive fractional crystallisation. The proportions of the juvenile or mantle component for most granitoids of Central Asia are estimated to vary from 70% to 100%.
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Fridovsky, V. Yu, A. E. Vernikovskaya, K. Yu Yakovleva, N. V. Rodionov, A. V. Travin, N. Yu Matushkin, and P. I. Kadilnikov. "Geodynamic Formation Conditions and Age of Granitoids from Small Intrusions in the West of the Yana–Kolyma Gold Belt (Northeast Asia)." Russian Geology and Geophysics 63, no. 4 (April 1, 2022): 483–502. http://dx.doi.org/10.2113/rgg20214442.
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Abstract We report results of geological, mineralogical-petrographic, geochemical, isotope-geochemical (Sm–Nd, Rb–Sr), and geochronological (U–Pb, 40Ar/39Ar) studies of acid and intermediate intrusive rocks (granodiorites, leucocratic granites, subalkaline granites, and subalkaline leucocratic granites, diorites, and quartz diorites) of the Bukeschen and Samyr small plutons in the western part of the Yana–Kolyma gold belt (northeast Asia). These rocks are combined with Late Jurassic (151–145 Ma) dikes of basic, intermediate, and acid compositions into a single complex of small intrusions. They intrude the Upper Triassic–Middle Jurassic terrigenous deposits of continental margin blocks in the eastern part of the Verkhoyansk–Kolyma folded area. Our new U–Pb data for zircon (SHRIMP-II) indicate that the Bukeschen and Samyr pluton granitoids formed in the Berriasian, at 144.5 and 143 Ma, respectively. The small-intrusion granitoids have geochemical and isotope (Sm–Nd and Rb–Sr) characteristics similar to those of Late Jurassic dikes of varying composition. Therefore, they can be united into a single complex of small intrusions generated from a mixed source with the participation of mantle (OIB- and E-MORB type), lower crust, and subduction components and with Paleoproterozoic–Mesoproterozoic Sm–Nd model age estimates for the magma sources. Late Jurassic–Early Cretaceous magmatic and postmagmatic events and cooling of the intrusions played an important role in the processes of gold localization in the western part of the Yana–Kolyma gold belt. This is reflected in two tectonothermal stages (accounting for closing temperatures of the U–Pb, 40Ar/39Ar, and Re–Os isotope systems for different minerals) estimated at 151–141 and 138–137 Ma. These results for the small-intrusion complex agree with the tectonic model of the evolution of an active continental margin (northeastern Siberia) in the Mesozoic era, whose final development stage in the Berriasian age saw the formation of mostly small granitoid plutons.
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Der-Chuen, Lee, Alex N. Halliday, Robert H. Hunter, Peter Holden, and Brian G. J. Upton. "Rb-Sr and Sm-Nd isotopic variations in dissected crustal xenoliths." Geochimica et Cosmochimica Acta 57, no. 1 (January 1993): 219–30. http://dx.doi.org/10.1016/0016-7037(93)90480-k.
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Lee, Hyo Min, Seung-Gu Lee, Hyeoncheol Kim, Jong Ik Lee, and Mi Jung Lee. "REE Tetrad Effect and Sr-Nd Isotope Systematics of A-Type Pirrit Hills Granite from West Antarctica." Minerals 11, no. 8 (July 22, 2021): 792. http://dx.doi.org/10.3390/min11080792.
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The Pirrit Hills are located in the Ellsworth–Whitmore Mountains of West Antarctica. The Pirrit Hills granite exhibits significant negative Eu anomalies (Eu/Eu* = 0.01~0.25) and a REE tetrad effect indicating intensive magmatic differentiation. Whole-rock Rb-Sr and Sm-Nd geochronologic analysis of the Pirrit Hills granite gave respective ages of 172.8 ± 2.4 Ma with initial 87Sr/86Sr = 0.7065 ± 0.0087 Ma and 169 ± 12 Ma with initial 144Nd/143Nd = 0.512207 ± 0.000017. The isotopic ratio data indicate that the Pirrit Hills granite formed by the remelting of Mesoproterozoic mantle-derived crustal materials. Both chondrite-normalized REE patterns and Sr-Nd isotopic data indicate that the Pirrit Hills granite has geochemical features of chondrite-normalized REE patterns indicating that REE tetrad effects and negative Eu anomalies in the highly fractionated granites were produced from magmatic differentiation under the magmatic-hydrothermal transition system.
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Sun, Jinheng, Ni Li, Cheng Dong, and Yanhong Ren. "Geochemical Features of Volcanic Rocks from the Shaerbuti Mountain Complex, West Junggar, Xinjiang, China: Implications for Recycling of Materials." Minerals 13, no. 1 (January 3, 2023): 75. http://dx.doi.org/10.3390/min13010075.
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In this paper, we focus on the geological features of volcanic edifices and the geochemistry of intermediate–basic volcanic rocks of Shaerbuti Mountain, which offer a new perspective on recycled materials in the study area. The Shaerbuti volcanic rocks consist of calc-alkali basalt and andesite formed in an arc setting. The porphyroclastic texture of basalt, explosive breccia rock, and the distribution of both breccia and agglomerate provide robust evidence that a volcanic edifice exists in Shaerbuti Mountain. Based on geochemical features, the Shaerbuti volcanic rocks have been identified as being of two types. Type I volcanic rocks have light rare earth element (LREE)-enriched patterns, with La/Sm ratios of 2.27–4.03, Th/Yb ratios of 0.50–1.46, and Nb/Yb ratios of 1.11–2.28. Type II volcanic rocks display a flat rare earth element (REE) pattern, with La/Sm ratios ranging from 1.83 to 2.43, Th/Yb ratios ranging from 0.24 to 0.45, and Nb/Yb ratios ranging from 0.87 to 0.93. In the studied rocks, MgO-Cr, MgO-Ni and MgO-CaO present a positive relationship, which indicates clinopyroxenes crystallized. The Sr-Nd-Pb isotopic compositions of these basalts present values of 0.7045 to 0.7063 ((87Sr/86Sr)i), 6.4 to 6.6 (εNd(t)), and 17.1300 to 18.3477 ((206Pb/204Pb)i), respectively. According to Sr-Nd-Pb isotope features, we argue that melts of altered oceanic crust and sediments were incorporated into the source. We also evaluate the water content (0.55%–6.72%) of the studied volcanic rocks.
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Filina, M. I., E. S. Sorokina, M. A. Rassomakhin, N. N. Kononkova, Yu A. Kostitsyn, and A. V. Somsikova. "Genetic linkage of corundum plagioclasites–kyshtymites and miaskites of the Ilmenogorsky–Vishnevogorsky complex, South Urals, Russia: new Rb–Sr and Sm–Nd isotopic, geochemical and mineralogical data." Геохимия 64, no. 7 (July 16, 2019): 742–49. http://dx.doi.org/10.31857/s0016-7525647742-749.
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New geochemical, mineralogical, and Rb–Sr and Sm–Nd isotopic data have been obtained on corundum plagioclasites–kyshtymites from the 5th Versta deposit (South Urals, Russia). The genetic link of miaskites and kyshtymites is shown. The formation of the kyshtymites is associated with the redistribution and accumulation of aluminum, calcium, HFSE, and LIL-elements at the stage of tectonic-metamorphic deformations of the Ilmenogorsky–Vishnevogorsky alkaline complex.
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SHEN, Weizhou. "Sm-Nd dating and Nd-Sr isotopic characteristics of the Shimian ophiolite suite, Sichuan Province." Chinese Science Bulletin 47, no. 22 (2002): 1897. http://dx.doi.org/10.1360/02tb9415.
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Barrie, C. Tucker, and Steven B. Shirey. "Nd- and Sr-isotope systematics for the Kamiskotia–Montcalm area: implications for the formation of late Archean crust in the western Abitibi Subprovince, Canada." Canadian Journal of Earth Sciences 28, no. 1 (January 1, 1991): 58–76. http://dx.doi.org/10.1139/e91-006.
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Geochemistry and Nd isotopic compositions are used to characterize mantle and crustal sources and to provide constraints on petrogenetic models for tholeiitic, calc-alkalic, and lamprophyric suites in the Kamiskotia–Montcalm area. The Kamiskotia gabbroic complex (KGC) and cogenetic, bimodal volcanic rocks have εNd(t) = +2.2 to +2.6, consistent with a direct derivation from a long-term, light rare-earth element (LREE)-depleted mantle. The Montcalm gabbroic complex has decreasing εNd(t) upsection from +2.8 to +1.0, consistent with contamination by long-term, LREE-enriched (with respect to the long-term, LREE-depleted Abitibi mantle) crust during fractionation. Two calc-alkalic lamprophyre samples, characterized by large-ion lithophile element (LILE) and LREE enrichment and high MgO, Ni, and Cr contents, have εNd(t) of +2.5 and +2.8, indicating a derivation from a depleted mantle source that had undergone recent trace-element enrichment. A different lamprophyre suite is extremely LILE and LREE enriched and has an εNd(t) of +1.0, indicating a derivation from a slightly different source that had earlier LREE enrichment. Granitoid rocks internal and external to greenstone belt rocks have εNd(t) = +2.5 to +3.8 and +0.6 to −0.4, respectively. The lower values provide additional evidence for the existence of LREE-enriched crust in this area.Considering these data along with other radiogenic isotope studies, a petrogenetic and tectonic model is suggested for the crustal development of the southern Abitibi Subprovince. From >2740 to 2698 Ma—the major period of volcanic activity—komatiitic and tholeiitic suites and one lamprophyre suite were derived from a uniformly LREE-depleted mantle reservoir with εNd(t) = +2 to +3. Calc-alkalic granitoids were emplaced generally after 2700 Ma. Their long-term, LREE-depleted and LREE-enriched Nd isotopic signatures are similar to signatures in continental-arc settings (e.g., the Coastal Batholith of Peru). Form 2690 to 2670 Ma, when transpressional tectonism prevailed, mantle-derived magmatism was represented by long-term, LREE-enriched (εNd(t) = +1 to +2) lamprophyric and alkalic volcanic suites.The Kamiskotia suite has a seven-point, whole-rock – mineral isochron Sm–Nd age of 2710 ± 30 Ma, identical to U–Pb zircon ages for the suite, indicating closed-system behavior. An Rb–Sr mineral – whole-rock isochron age from one KGC sample is 2450 ± 30 Ma, identical to U–Pb ages for the Hearst–Matachewan dike swarm, a prominent feature in the KGC area. Regression of whole-rock and mineral-isotope data for one granitoid sample with a U–Pb zircon age of 2696 ± 1.5 Ma gives identical ages of 2530 ± 30 Ma in the Sm–Nd and Rb–Sr systems. The latter data add to an increasing body of evidence for cryptic, late thermal events after granitoid–greenstone belt development in the southern Abitibi Subprovince.
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Le, Phuc Duc. "GRANITOID PETROLOGY OF HAI VAN MASSIF." Science and Technology Development Journal 12, no. 5 (March 15, 2009): 46–54. http://dx.doi.org/10.32508/stdj.v12i5.2243.
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The granitoid formations of Hai Van massif with petrographical components consist of biotite granite, two mica granite. Chemical components of rocks are: SiO2: 69,34=73,92%, Na2O+KO: 6,11-8,11%, K2O/Na20>1. Content of Ba, Sr is low but Rb is higher. From results of Nd-Sm isotopic analysic shows that they are nearly same with stable crust material. Age of source region formation is 1,33 billion years (model of homogeneous chondrite source region), or 1,95 billion years (model of poor mantle source region). U-Pb isotopic age: 241,9+ 2 and 241,4+2.1 million years.
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Dia, Aline, Bernard Dupré, Clément Gariépy, and Claude J. Allègre. "Sm–Nd and trace-element characterization of shales from the Abitibi Belt, Labrador Trough, and Appalachian Belt: consequences for crustal evolution through time." Canadian Journal of Earth Sciences 27, no. 6 (June 1, 1990): 758–66. http://dx.doi.org/10.1139/e90-077.
Full textAbstract:
Nd-isotopic compositions and Sm, Nd, Li, K, Rb, Sr, Ba, Ni, and Cr abundances are reported for 25 shale samples from the Canadian Shield (late Archean Abitibi greenstone belt and the mid-Proterozoic Labrador Trough) and from the Quebec Appalachians (lower Paleozoic Humber Zone). The chemical and isotopic characteristics of the samples are used to monitor the rate of generation and the compositional evolution of continental crust through time. The Nd crustal-residence ages record preferential time of continental growth around 2.7 and 1.7 Ga. The Nd model ages of the Appalachian shales do not record evidence for the formation of large crustal volumes through mantle extraction since 1.3 Ga. Consequently, crustal recycling was the dominant process taking place at their source areas in the Grenville Province.The trace-element distributions of shales show systematic trends as a function of time: Li, K, Ba, Sm, and Nd contents regularly increase in the post-Archean record; in comparison, the Cr and Ni contents reached a maximum towards the end of the Archean and regularly decreased thereafter. These observations could reflect two classes of processes: (a) the development of infracrustal K-rich granitoid magmatism at the expense of mantle-derived Na-rich magmatism, which dominated the Archean period; or (b) differential erosion effects, which reduced the sampling of the old, smooth crustal parts in comparison to the younger, recycled segments. In the latter case, (b), shale formation involved components whose nature and respective proportion changed after Archean time.