Geodynamic and metabolic cycles in the Hadean M. J. Russell, N. T. Arndt To cite this version: M. J. Russell, N. T. Arndt. Geodynamic and metabolic cycles in the Hadean. Biogeosciences Discus- sions, European Geosciences Union, 2004, 1 (1), pp.591-624. hal-00330217 HAL Id: hal-00330217 https://hal.archives-ouvertes.fr/hal-00330217 Submitted on 22 Sep 2004 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Biogeosciences Discussions, 1, 591–624, 2004 Biogeosciences BGD www.biogeosciences.net/bgd/1/591/ Discussions SRef-ID: 1810-6285/bgd/2004-1-591 1, 591–624, 2004 © European Geosciences Union 2004 Hadean geodynamic Biogeosciences Discussions is the access reviewed discussion forum of Biogeosciences and metabolic cycles M. J. Russell and N. T. Arndt Title Page Abstract Introduction Geodynamic and metabolic cycles in the Conclusions References Hadean Tables Figures M. J. Russell and N. T. Arndt J I LGCA, Universite´ de Grenoble 1, 1381, rue de la Piscine, 38400 St. Martin d’Heres, France J I Received: 26 July 2004 – Accepted: 30 August 2004 – Published: 22 September 2004 Back Close Correspondence to: N. T. Arndt ([email protected]) Full Screen / Esc Print Version Interactive Discussion © EGU 2004 591 Abstract BGD High-degree melting of hot dry Hadean mantle at ocean ridges and plumes resulted 1, 591–624, 2004 in a crust about 30 km thick, overlain in places by extensive and thick mafic volcanic plateaus. Continental crust, by contrast, was relatively thin and mostly submarine. At Hadean geodynamic 5 constructive and destructive plate boundaries, and above the many mantle plumes, and metabolic cycles acidic hydrothermal springs at ∼400◦C contributed Fe and other transition elements as well as P and H2 to the deep ocean made acidulous by dissolved CO2 and minor HCl M. J. Russell and N. T. derived from volcanoes. Away from ocean ridges, submarine hydrothermal fluids were Arndt ◦ cool (≤100 C), alkaline (pH ∼10), highly reduced and also H2-rich. Reaction of sol- 10 vents in this fluid with those in ocean water was catalyzed in a hydrothermal mound, a natural self-restoring flow reactor and fractionation column made up of carbonates and Title Page freshly precipitated Fe-Ni sulfide and greenrust pores and bubbles, developed above Abstract Introduction the alkaline spring. Acetate and the amino acetate glycine were the main products, much of which was eluted to the ocean. Other organic byproducts were retained, con- Conclusions References 15 centrated and reacted within the compartments. These compartments comprising the Tables Figures natural hydrothermal reactor consisted partly of greigite (Fe5NiS8). It was from reac- tions between organic modules confined within these inorganic compartments that the first prokaryotic organism evolved. These acetogenic precursors to the Bacteria diver- J I sified and migrated down the mound and into the ocean floor to inaugurate the ‘deep J I 20 biosphere’. Once there the Bacteria, and the recently differentiated Archaea, were pro- tected from cataclysmic heating events caused by large bolide impacts. Geodynamic Back Close forces led to the eventual obduction of the deep biosphere into the photic zone where, Full Screen / Esc initially protected by a thin veneer of sediment, the use of solar energy was mastered and photosynthesis emerged. The further evolution to oxygenic photosynthesis was 4+ Print Version 25 effected as catalytic [CaMn ]-bearing molecules that otherwise would have been in- terred in the mineral rancieite´ in the shallow marine manganiferous sediments, were Interactive Discussion sequestered and invaginated within the cyanobacterial precursor where, energized by light, they could oxidize water with greater efficiency. Thus, chemical sediments were © EGU 2004 592 required both for the emergence of chemosynthesis and of oxygenic photosynthesis, BGD the two innovations that did most to change the nature of our planet. 1, 591–624, 2004 1. Introduction Hadean geodynamic The Earth’s internal thermal energy is mainly degraded through convection. Heat is and metabolic cycles 5 transferred to the surface by a convecting mantle, to be discharged through volcanoes M. J. Russell and N. T. and hydrothermal springs into the ocean and atmosphere (the volatisphere). Chemical Arndt disequilibrium between reduced mantle and oxidized volatisphere is focused at springs and seepages on land or on the ocean floor. In turn this chemical energy is degraded through metabolism. Today metabolism relies on convection for supply of nutrients in Title Page 10 the ocean and on convection in the atmosphere for irrigation and chemical weathering of the land. The springs and seepages are oases of life in both realms. Abstract Introduction At a broader scale and at slower rates, global geodynamic processes generate fresh, Conclusions References reduced rock surfaces that provide energy and supply nutrients to life. This coupling of metabolism to convection was directly implicated in the onset of life, which probably Tables Figures 15 emerged at least 4 Ga ago at moderate temperature seepages (Russell et al., 1988, 1994). J I Reconstruction of the conditions that drove life to emerge and evolve its metabolic cycles is the main task of this paper. We begin by considering what present-day pro- J I cesses offer to the understanding of the conditions on the surface and in the interior Back Close 20 of the Hadean/Archaean Earth, then suggest a scenario for the onset of life and its colonization of the ocean floor. This journey from geodynamics, through geochem- Full Screen / Esc istry to biochemistry leads us to conclude that obduction of oceanic crust facilitated the evolutionary jump to photosynthesis. Print Version Interactive Discussion © EGU 2004 593 2. The modern oceanic crust BGD 2.1. Birth and death of oceanic crust 1, 591–624, 2004 A complete plate tectonic cycle starts with the formation of crust at a ridge and ends with its recycling to the mantle at a subduction zone. Continental crust forms above Hadean geodynamic and metabolic cycles 5 subduction zones, a direct result of the dehydration of subducting oceanic crust which triggers partial melting in the overlying mantle and the development of hydrous mag- M. J. Russell and N. T. mas. Superimposed on the plate tectonic cycle is the formation of oceanic islands and Arndt oceanic plateaus, which are generated by partial melting in mantle plumes. 2.2. Modern hydrothermal systems – how they work Title Page 10 Five main types of hydrothermal fluids circulate through modern oceanic crust. Three Abstract Introduction high temperature types (≤4◦C) operate at oceanic ridges, above plumes or in back arc basins; an intermediate type occurs on ridge flanks (≤75◦C); and the last, far cooler, on Conclusions References the deep ocean floor (Anderson et al., 1977; Von Damm, 1990, Cathles, 1990; Sedwick Tables Figures et al., 1994; Kelley et al., 2001; Wheat et al., 2002) (Table 1). 15 The temperature of the very hot springs, driven by magmatic intrusion, is controlled J I largely by the two-phase boundary of water and its critical point (Bischoff and Rosen- bauer, 1984). Temperatures in modern hydrothermal convective systems, which bot- J I tom at an overall water column depth of 4 km or so, tend to peak at ∼4◦C. The fluids in Back Close the downdrafts become acidic (pH ∼3) through the release of protons as Mg2+ is fixed 20 as serpentine and brucite (Janecky and Seyfried, 1983; Douville et al., 2002). These Full Screen / Esc acidic solutions dissolve, transport and exhale the transition metals, some phosphate, H2S and H2, at black smokers (Table 1) (Von Damm, 1990; Kakegawa et al., 2002). Print Version The temperatures and compositions of intermediate-temperature hydrothermal con- vection cells are controlled by exothermic reactions and the rheology of the newly ser- Interactive Discussion 25 pentinized mafic to ultramafic rock of the conduits. So far the fluid from only one entirely submarine example of ultramafic interaction has been sampled, the “Lost City” field, 15 © EGU 2004 594 km from the Mid Atlantic Ridge (Kelley et al., 2001). The pH of this water approaches − ◦ BGD 10 as Ca(OH)2, HCO3 and H2 are eluted, and the temperature is 70–75 C (Table 1) (Kelley et al., 2001). A cooler (72◦C) alkaline (pH 10) fresh-water submarine spring in 1, 591–624, 2004 a fjord off the north coast of Iceland (Marteinsson et al., 2001; Geptner et al., 2002) 5 is characterized by porous cones of Mg-rich clay (saponite) some tens of metres high Hadean geodynamic (Table 1). and metabolic cycles Still farther from ridges, even cooler circulation is driven by heat within the uppermost crust. Small closed convection cells are evenly spaced with a periodicity of about 7 km, M. J. Russell and N. T. with thermal cusps around 20◦C (Anderson et al., 1977). Arndt 10 Data for columns 1 to 4 from Von Damm (1990), Douville et al. (2002), Kelley et al. (2001) and Marteinsson et al. (2001). Elemental and molecular concentrations are in millimoles. Temperatures at the base of the convection cells developed at oceanic Title Page ◦ ◦ spreading centres and the off-ridge systems are presumed to be ∼400 C and ∼100 C, Abstract Introduction respectively. Conclusions References 15 3. Hadean/Archaean ocean/atmosphere, oceanic crust and global dynamics Tables Figures 3.1. The volatisphere J I According to oxygen isotope analysis of the oldest known zircons, an ocean is assumed J I to have condensed on Earth by 4.4 Ga (Wilde et al., 2001).