Formation of jasper and andradite during low-temperature hydrothermal seafloor metamorphism, Ongeluk Formation, South Africa

Gutzmer, Jens; Pack, Andreas; Lüders, Volker; Wilkinson, Jamie J.; Beukes, Nicolas J.; Niekerk, H.S. Van

doi:10.1007/s004100100270

Cited by 34 publications

(28 citation statements)

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“…The red layer consists of hematite and minor amounts of microquartz, magnetite, and pyrite, whereas the white layer comprises microquartz and larger subhedral andradite with subordinate hematite and disseminated calcite (Fig. 3d, e), as previously reported (Gutzmer et al 2001). As observed for the lavas, minor jaspilite samples exhibit deformation textures such as brecciation and/or calcite veining (Fig.…”

Section: Lavas and Hydrothermal Jaspilites In The Ongeluk Formationsupporting

confidence: 81%

“…The Ongeluk basaltic andesites are mostly undeformed, and igneous textures, such as intergranular, intersertal, and subophitic textures, are well preserved (Cornell et al 1996;Gutzmer et al 2001Gutzmer et al , 2003) (see also Fig. 3a).…”

Section: Lavas and Hydrothermal Jaspilites In The Ongeluk Formationmentioning

confidence: 98%

“…2). Metamorphism of the Ongeluk Formation does not exceed prehnite-pumpellyite facies, so that the effects of ancient passive subseafloor hydrothermal alteration are still plain to see (Gutzmer et al 2001). The age of the Ongeluk Formation had long been under debate because two possible depositional ages (2.2 and 2.4 Ga) were constrained by other formations stratigraphically close to the Ongeluk Formation (Bau et al 1999;Cornell et al 1996;Dorland 2004).…”

Section: The Ongeluk Formationmentioning

confidence: 99%

“…The Ongeluk pillow lavas still retain open drainage cavities and interpillow voids. These are filled with quartz and/or jaspilite, which was likely precipitated penecontemporaneously with the interbedded jaspilite (Grobler and Botha 1976;Gutzmer et al 2001Gutzmer et al , 2003. The precipitates in the drainage cavities have smooth, oval tubular shapes and are oriented parallel to the pillow tubes themselves or to the direction of lava flow.…”

Section: Lavas and Hydrothermal Jaspilites In The Ongeluk Formationmentioning

confidence: 99%

“…3f). The formation temperature of these hydrothermal precipitates was estimated to be 64-160°C from the homogenization temperature of fluid inclusions in the quartz (Gutzmer et al 2001(Gutzmer et al , 2003Saito et al 2016). …”

Section: Lavas and Hydrothermal Jaspilites In The Ongeluk Formationmentioning

confidence: 99%

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Weak hydrothermal carbonation of the Ongeluk volcanics: evidence for low CO2 concentrations in seawater and atmosphere during the Paleoproterozoic global glaciation

Shibuya

Komiya

Takai

et al. 2017

Prog Earth Planet Sci

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It was previously revealed that the total CO 2 concentration in seawater decreased during the Late Archean. In this paper, to assess the secular change of total CO 2 concentration in seawater, we focused on the Paleoproterozoic era when the Earth experienced its first recorded global glaciation. The 2.4 Ga Ongeluk Formation outcrops in the Kaapvaal Craton, South Africa. The formation consists mainly of submarine volcanic rocks that have erupted during the global glaciation. The undeformed lavas are mostly carbonate-free but contain rare disseminated calcites. The carbon isotope ratio of the disseminated calcite (δ 13 C cc vs. VPDB) ranges from − 31.9 to − 13.2 ‰. The relatively low δ 13 C cc values clearly indicate that the carbonation was partially contributed by 13 C-depleted CO 2 derived from decomposition of organic matter beneath the seafloor. The absence of δ 13 C cc higher than − 13.2‰ is consistent with the exceptionally 13 C-depleted CO 2 in the Ongeluk seawater during glaciation. The results suggest that carbonation occurred during subseafloor hydrothermal circulation just after the eruption of the lavas. Previously, it was reported that the carbonate content in the uppermost subseafloor crust decreased from 3.2 to 2.6 Ga, indicating a decrease in total CO 2 concentration in seawater during that time. However, the average CO 2 (as carbonate) content in the Ongeluk lavas (< 0.001 wt%) is much lower than those of 2.6 Ga representatives and even of modern equivalents. This finding suggests that the total CO 2 concentration in seawater further decreased during the period between 2.6 and 2.4 Ga. Thus, the very low content of carbonate in the Ongeluk lavas is probable evidence for the extremely low CO 2 concentration in seawater during the global glaciation. Considering that the carbonate content of the subseafloor crusts also shows a good correlation with independently estimated atmospheric pCO 2 levels through the Earth history, it seem highly likely that the low carbonate content in the Ongeluk lavas reflects the low atmospheric pCO 2 at that time. We conclude that the continuous decrease in CO 2 concentration of seawater/atm. from 3.2 Ga was one of the contributing factors to the Paleoproterozoic global glaciation.

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Section: Lavas and Hydrothermal Jaspilites In The Ongeluk Formationsupporting

confidence: 81%

Section: Lavas and Hydrothermal Jaspilites In The Ongeluk Formationmentioning

confidence: 98%

Section: The Ongeluk Formationmentioning

confidence: 99%

Section: Lavas and Hydrothermal Jaspilites In The Ongeluk Formationmentioning

confidence: 99%

Section: Lavas and Hydrothermal Jaspilites In The Ongeluk Formationmentioning

confidence: 99%

See 3 more Smart Citations

Weak hydrothermal carbonation of the Ongeluk volcanics: evidence for low CO2 concentrations in seawater and atmosphere during the Paleoproterozoic global glaciation

Shibuya

Komiya

Takai

et al. 2017

Prog Earth Planet Sci

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show abstract

Environmental Context

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From Suns to Life: A Chronological Approach to the History of Life on Earth

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Bedded jaspers of the Ordovician Løkken ophiolite, Norway: seafloor deposition and diagenetic maturation of hydrothermal plume-derived silica-iron gels

Grenne

Slack

2003

Miner Deposita

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Formation of jasper and andradite during low-temperature hydrothermal seafloor metamorphism, Ongeluk Formation, South Africa

Cited by 34 publications

References 0 publications

Weak hydrothermal carbonation of the Ongeluk volcanics: evidence for low CO2 concentrations in seawater and atmosphere during the Paleoproterozoic global glaciation

Weak hydrothermal carbonation of the Ongeluk volcanics: evidence for low CO2 concentrations in seawater and atmosphere during the Paleoproterozoic global glaciation

Environmental Context

Bedded jaspers of the Ordovician Løkken ophiolite, Norway: seafloor deposition and diagenetic maturation of hydrothermal plume-derived silica-iron gels

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