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Early trace of life from 3.95 Ga sedimentary rocks in Labrador, Canada

机译：来自加拿大拉布拉多3.95 Ga沉积岩的生命早期踪迹

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摘要

The vestiges of life in Eoarchean rocks have the potential to elucidate the origin of life. However, gathering evidence from many terrains is not always possible(1-3), and biogenic graphite has thus far been found only in the 3.7-3.8 Ga (gigayears ago) Isua supracrustal belt(4-7). Here we present the total organic carbon contents and carbon isotope values of graphite (d13Corg) and carbonate (delta(13)Ccarb) in the oldest metasedimentary rocks from northern Labrador(8,9). Some pelitic rocks have low delta(13)Corg values of -28.2, comparable to the lowest value in younger rocks. The consistency between crystallization temperatures of the graphite and metamorphic temperature of the host rocks establishes that the graphite does not originate from later contamination. A clear correlation between the delta(13)Corg values and metamorphic grade indicates that variations in the delta(13)Corg values are due to metamorphism, and that the pre-metamorphic value was lower than the minimum value. We concluded that the large fractionation between the delta(13)Ccarb and delta(13)Corg values, up to 25%, indicates the oldest evidence of organisms greater than 3.95 Ga. The discovery of the biogenic graphite enables geochemical study of the biogenic materials themselves, and will provide insight into early life not only on Earth but also on other planets.
机译：欧亚大陆岩石中的生命痕迹有可能阐明生命的起源。然而，并非总是能够从许多地形中收集证据（1-3），而迄今为止仅在3.7-3.8 Ga（千兆年前）Isua上壳带（4-7）中发现了生物成因石墨。在这里，我们介绍了拉布拉多北部最古老的沉积沉积岩中石墨（d13Corg）和碳酸盐（delta（13）Ccarb）的总有机碳含量和碳同位素值（8,9）。一些珠光体岩石的δ（13）Corg值较低，为-28.2，与年轻岩石中的最低值相当。石墨的结晶温度与基质岩石的变质温度之间的一致性确定了石墨不是源自后来的污染。 delta（13）Corg值与变质等级之间的明确相关性表明，delta（13）Corg值的变化是由于变质引起的，并且预变质值低于最小值。我们得出的结论是，delta（13）Ccarb和delta（13）Corg值之间的较大分馏（高达25％）表明了大于3.95 Ga的生物的最古老证据。生物石墨的发现使生物材料的地球化学研究成为可能。本身，并将不仅对地球上的早期生命提供洞察力，而且对其他行星也具有洞察力。

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  • 来源
    《Nature》 |2017年第7673期|516-518|共3页
  • 作者

    Tashiro Takayuki; Ishida Akizumi; Hori Masako; Igisu Motoko; Koike Mizuho; Mejean Pauline; Takahata Naoto; Sano Yuji; Komiya Tsuyoshi;

  • 作者单位

    Univ Tokyo, Grad Sch Arts & Sci, Dept Earth Sci & Astron, Tokyo 1538902, Japan;

    Univ Tokyo, Atmosphere & Ocean Res Inst, Chiba 2778564, Japan|Tohoku Univ, Inst Excellence Higher Educ, Sendai, Miyagi 9808576, Japan;

    Univ Tokyo, Atmosphere & Ocean Res Inst, Chiba 2778564, Japan|Osaka Kyoiku Univ, Dept Arts & Sci, Osaka 5828582, Japan;

    Japan Agcy Marine Earth Sci & Technol JAMSTEC, Lab Ocean Earth Life Evolut Res, Yokosuka, Kanagawa 2370061, Japan;

    Univ Tokyo, Atmosphere & Ocean Res Inst, Chiba 2778564, Japan;

    Univ Tokyo, Atmosphere & Ocean Res Inst, Chiba 2778564, Japan;

    Univ Tokyo, Atmosphere & Ocean Res Inst, Chiba 2778564, Japan;

    Univ Tokyo, Atmosphere & Ocean Res Inst, Chiba 2778564, Japan;

    Univ Tokyo, Grad Sch Arts & Sci, Dept Earth Sci & Astron, Tokyo 1538902, Japan;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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