Item talk:Q310924

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   "@type": "Article",
   "additionalType": "Journal Article",
   "name": "Effects of interaction between ultramafic tectonite and mafic magma on Nd-Pb-Sr isotopic systems in the Neoproterozoic Chaya Massif, Baikal-Muya ophiolite belt",
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       "value": "10.1016/S0012-821X(97)00046-0",
       "url": "https://doi.org/10.1016/S0012-821X(97)00046-0"
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   "journal": {
     "@type": "Periodical",
     "name": "Earth and Planetary Science Letters",
     "volumeNumber": "148",
     "issueNumber": "1-2"
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   "inLanguage": "en",
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       "name": "Earth and Planetary Science Letters"
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   "datePublished": "1997",
   "dateModified": "2020-01-14",
   "abstract": "Sm-Nd, Rb-Sr and U-Pb isotopic systems have been studied in minerals and whole rocks of harzburgites and mafic cumulates from the Chaya Massif, Baikal-Muya ophiolite belt, eastern Siberia, in order to determine the relationship between mantle ultramafic and crustal mafic sections. Geological relations in the Chaya Massif indicate that the mafic magmas were emplaced into, and interacted with older solid peridotite. Hand picked, acid-leached, primary rock-forming and accessory minerals (olivine, orthopyroxene, clinopyroxene and plagioclase) from the two harzburgite samples show coherent behavior and yield\u00a0147Sm/144Nd-143Nd/144Nd and\u00a0238U/204Pb-206Pb/204Pb mineral isochrons, corresponding to ages of 640 \u00b1 58 Ma (95% confidence level) and 620 \u00b1 71 Ma, respectively. These values are indistinguishable from the crystallization age of the Chaya mafic units of 627 \u00b1 25 Ma (a weighted average of internal isochron Sm-Nd ages of four mafic cumulates). The Rb-Sr and Sm-Nd isotopic systems in the harzburgite whole-rock samples were disturbed by hydrothermal alteration. These alteration-related isotopic shifts mimic the trend of variations in primary isotopic compositions in the mafic sequence, thus emphasizing that isotopic data for ultramafic rocks should be interpreted with great caution.On the basis of initial Sr and Nd values, ultramafic and mafic rocks of the Chaya Massif can be divided into two groups: (1) harzburgites and the lower mafic unit gabbronorites with\u03b5Nd\u00a0= +6.6 to +7.1 and\u03b5Sr\u00a0= \u221211 to \u221216; and (2) websterite of the lower unit and gabbronorites of the upper mafic unit:\u03b5Nd\u00a0= +4.6 to +6.1 and\u03b5Sr\u00a0= \u22128 to \u22129. Initial Pb isotopic ratios are identical in all rocks studied, with mean values of\u00a0206Pb/204Pb= 16.994 \u00b1 0.023 and\u00a0207Pb/204Pb= 15.363 \u00b1 0.015. The similarity of ages and initial isotopic ratios within the first group indicates that the isotopic systems in the pre-existing depleted peridotite were reset by extensive interaction with basaltic magma during formation of the mafic crustal sequence. The isotopic data agree with a hypothesized formation of the Chaya Massif in a suprasubduction-zone environment.",
   "description": "18 p.",
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     "@type": "Organization",
     "name": "Elsevier"
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   "author": [
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       "@type": "Person",
       "name": "Amelin, Y. V.",
       "givenName": "Y. V.",
       "familyName": "Amelin"
     },
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       "@type": "Person",
       "name": "Ritsk, E. Yu",
       "givenName": "E. Yu",
       "familyName": "Ritsk"
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       "name": "Neymark, L.A.",
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       "name": "Geology, Geophysics, and Geochemistry Science Center",
       "url": "https://www.usgs.gov/centers/gggsc"
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