Carbon and Oxygen Stable Isotopes in Isochemical Contact Metamorphism (Case Study of the Kochumdek Aureole, East Siberia)

IF 1.2 4区地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY

Russian Geology and Geophysics Pub Date : 2023-12-08 DOI:10.2113/rgg20234545

E.V. Sokol, A. S. Deviatiiarova, A. Pyryaev, T. Bul’bak, A. Tomilenko, Yu.V. Seretkin, I.V. Pekov, A. V. Nekipelova, P. Khvorov

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Abstract

––Carbon and oxygen isotope compositions have been determined in (CO3)-groups of Ca carbonate–silicate minerals (spurrite, tilleyite, and scapolite) and calcite from samples of the Kochumdek contact aureole (East Siberia). The observed small δ13C and δ18O difference between the Kochumdek marbles and their protoliths (Δδ13C ≤ 1.5‰ and Δδ18O ≤ 2.0‰) is consistent with moderate high-temperature metamorphic decarbonation of the protolith (0.1–0.2) and with almost absent metasomatic alteration in the aureole. Significant 18O depletion was inferred only for vein scapolite (δ18O from +17.0 to +17.3‰ V-SMOW) and calcite from recrystallized limestone layers (δ18O from +18.9 to +20.6‰), which is evidence for limited infiltration of magmatic aqueous fluids from the cooling sill into the host sediments. The C and O isotope compositions of (CO3)-bearing spurrite and tilleyite show lower 18O depletion and insignificant 13C depletion relative to calcite, especially in highest-temperature merwinite marble (Δδ18OSpu–Cal = +3.3‰; Δδ13CSpu–Cal = –0.8‰). Gas chromatography-mass spectrometry (GC-MS) provided constraints on the relative percentages of H2O and CO2 in the fluid at highest-temperature spurrite-merwinite metamorphism. The fluid phase entrapped in calcite from merwinite marble is rich in CO2(XCO2=0.4−0.6).

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等化学接触变质作用中的碳和氧稳定同位素（东西伯利亚 Kochumdek Aureole 案例研究）

--测定了科楚姆德克接触弧（东西伯利亚）样品中碳酸钙硅酸盐矿物（尖晶石、钛铁矿和霞石）和方解石的（CO3）组碳和氧同位素组成。观测到的 Kochumdek 大理石与其原岩之间的 δ13C 和 δ18O 差异很小（Δδ13C ≤ 1.5‰，Δδ18O ≤ 2.0‰），这与原岩的中度高温变质脱碳（0.1-0.2）以及金口几乎不存在变质蚀变相吻合。只有脉闪长岩（δ18O从+17.0到+17.3‰ V-SMOW）和重结晶石灰岩层的方解石（δ18O从+18.9到+20.6‰）推断出了18O的显著损耗，这证明了岩浆水流从冷却的山体向主沉积物的有限渗透。与方解石相比，含（CO3）的尖晶石和透辉石的 C 和 O 同位素组成显示出较低的 18O 损耗和不明显的 13C 损耗，尤其是在温度最高的梅花石大理岩中（Δδ18OSpu-Cal = +3.3‰；Δδ13CSpu-Cal = -0.8‰）。气相色谱-质谱法（GC-MS）对最高温度尖晶石-闪长岩变质时流体中 H2O 和 CO2 的相对比例提供了约束。梅花石大理岩方解石中夹带的流体相富含二氧化碳（XCO2=0.4-0.6）。

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来源期刊

Russian Geology and Geophysics 地学-地球科学综合

CiteScore

2.00

自引率

18.20%

发文量

审稿时长

4-8 weeks

期刊介绍： The journal publishes original reports of theoretical and methodological nature in the fields of geology, geophysics, and geochemistry, which contain data on composition and structure of the Earth''s crust and mantle, describes processes of formation and general regularities of commercial mineral occurrences, investigations on development and application of geological-geophysical methods for their revealing. As to works of regional nature, accelerated publication are available for original papers on a variety of problems of comparative geology taking into account specific character of Siberia, adjacent Asian countries and water areas. The journal will also publish reviews, critical articles, chronicle of the most important scientific events, and advertisements.