TY - JOUR

T1 - Evaluating the multiple sulfur isotope signature of Eoarchean rocks from the Isua Supracrustal Belt (Southwest-Greenland) by MC-ICP-MS

T2 - Volcanic nutrient sources for early life

AU - Macdonald, Jane E.

AU - Sugden, Patrick

AU - Dumont, Matthew

AU - Szilas, Kristoffer

AU - Glorie, Stijn

AU - Simpson, Alexander

AU - Gilbert, Sarah

AU - Burke, Andrea

AU - Stüeken, Eva E.

N1 - Publisher Copyright: © 2024 The Authors. Geobiology published by John Wiley & Sons Ltd.

PY - 2024/3/1

Y1 - 2024/3/1

N2 - On the anoxic Archean Earth, prior to the onset of oxidative weathering, electron acceptors were relatively scarce, perhaps limiting microbial productivity. An important metabolite may have been sulfate produced during the photolysis of volcanogenic SO2 gas. Multiple sulfur isotope data can be used to track this sulfur source, and indeed this record indicates SO2 photolysis dating back to at least 3.7 Ga, that is, as far back as proposed evidence of life on Earth. However, measurements of multiple sulfur isotopes in some key strata from that time can be challenging due to low sulfur concentrations. Some studies have overcome this challenge with NanoSIMS or optimized gas-source mass spectrometry techniques, but those instruments are not readily accessible. Here, we applied an aqua regia leaching protocol to extract small amounts of sulfur from whole rocks for analyses of multiple sulfur isotopes by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Measurements of standards and replicates demonstrate good precision and accuracy. We applied this technique to meta-sedimentary rocks with putative biosignatures from the Eoarchean Isua Supracrustal Belt (ISB, >3.7 Ga) and found positive ∆33S (1.40–1.80‰) in four meta-turbidites and negative ∆33S (−0.80‰ and −0.66‰) in two meta-carbonates. Two meta-basalts do not display significant mass-independent fractionation (MIF, −0.01‰ and 0.16‰). In situ Re–Os dating on a molybdenite vein hosted in the meta-turbidites identifies an early ca. 3.7 Ga hydrothermal phase, and in situ Rb–Sr dating of micas in the meta-carbonates suggests metamorphism affected the rocks at ca. 2.2 and 1.7 Ga. We discuss alteration mechanisms and conclude that there is most likely a primary MIF-bearing phase in these meta-sediments. Our new method is therefore a useful addition to the geochemical toolbox, and it confirms that organisms at that time, if present, may indeed have been fed by volcanic nutrients.

AB - On the anoxic Archean Earth, prior to the onset of oxidative weathering, electron acceptors were relatively scarce, perhaps limiting microbial productivity. An important metabolite may have been sulfate produced during the photolysis of volcanogenic SO2 gas. Multiple sulfur isotope data can be used to track this sulfur source, and indeed this record indicates SO2 photolysis dating back to at least 3.7 Ga, that is, as far back as proposed evidence of life on Earth. However, measurements of multiple sulfur isotopes in some key strata from that time can be challenging due to low sulfur concentrations. Some studies have overcome this challenge with NanoSIMS or optimized gas-source mass spectrometry techniques, but those instruments are not readily accessible. Here, we applied an aqua regia leaching protocol to extract small amounts of sulfur from whole rocks for analyses of multiple sulfur isotopes by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Measurements of standards and replicates demonstrate good precision and accuracy. We applied this technique to meta-sedimentary rocks with putative biosignatures from the Eoarchean Isua Supracrustal Belt (ISB, >3.7 Ga) and found positive ∆33S (1.40–1.80‰) in four meta-turbidites and negative ∆33S (−0.80‰ and −0.66‰) in two meta-carbonates. Two meta-basalts do not display significant mass-independent fractionation (MIF, −0.01‰ and 0.16‰). In situ Re–Os dating on a molybdenite vein hosted in the meta-turbidites identifies an early ca. 3.7 Ga hydrothermal phase, and in situ Rb–Sr dating of micas in the meta-carbonates suggests metamorphism affected the rocks at ca. 2.2 and 1.7 Ga. We discuss alteration mechanisms and conclude that there is most likely a primary MIF-bearing phase in these meta-sediments. Our new method is therefore a useful addition to the geochemical toolbox, and it confirms that organisms at that time, if present, may indeed have been fed by volcanic nutrients.

KW - Eoarchean

KW - fluid alteration

KW - in situ

KW - Isua

KW - MC-ICP-MS

KW - sulfur isotopes

UR - http://www.scopus.com/inward/record.url?scp=85189894737&partnerID=8YFLogxK

U2 - 10.1111/gbi.12595

DO - 10.1111/gbi.12595

M3 - Journal article

C2 - 38596869

AN - SCOPUS:85189894737

VL - 22

JO - Geobiology

JF - Geobiology

SN - 1472-4677

IS - 2

M1 - e12595

ER -