DCO Project Summary

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Project Title
North Pole Dome, Australia
Start DateEnd Date
2014-06-17 2014-06-27
NameRoleInstitutionDCO ID
Related GrantsDCO ID
11121/4015-2040-1025-6363-CC
Description

The North Pole Dome in Western Australia is a small feature within the ancient Pilbara Complex, which represents a remarkable raft of virtually unaltered crust from Earth’s Archean Eon. It is a roughly circular ring of hills, approximately 12 kilometers in diameter, surrounding a relatively flat depression that represents a “caldera”—the collapsed center of a 3.5 billion-year-old volcano. Following the collapse, the caldera gradually filled with layers of sediments, some of which contain pristine microbial fossil mounds called “stromatolites,” as well as other features that point to a dynamic shallow water environment.  

The  North Pole Dome holds Earth’s oldest unambiguous fossils, as well as extensive carbon-bearing rocks and hints regarding Earth’s early geochemical environment. This study will include detailed mapping of North Pole Dome hydrothermal systems and will investigate distributions of organic carbon, the geochemistry of carbonate minerals, and the nature and extent of diagnostic detrital minerals in these ancient rocks.

Geological Context: Life may have arisen in a hydrothermal environment, in an alkaline, low-temperature (<100°C) system. Indeed, the oldest convincing evidence for life occurs in just such a system, within the exceptionally well-preserved volcanic caldera and associated hydrothermal vein system of the ~3.5 Ga North Pole Dome, Pilbara Craton, Western Australia. Previous work documented a variety of early life signatures in this area, but it remains unclear whether early life was exclusively linked to hydrothermal systems, or if it occupied a variety of niches that reflect diverse microbial environments.

This field study will entail detailed mapping of carbon-bearing zones of the North Pole Dome hydrothermal system. We will also leverage ongoing detailed geological mapping and laboratory analysis of the North Pole Dome to explore three topics tied to DCO Decadal Goals related to Deep Life, Reservoirs and Fluxes, and Deep Energy. First, we will characterize the composition and distribution of carbonaceous materials within the North Pole hydrothermal system, to search for co-variation with changes in fluid temperature, system chemistry, and depth. These studies will assist with discriminating between a biogenic vs. abiogenic origin for the stromatolites, microfossils, and carbonaceous materials preserved in hydrothermal veins, in footwall basalts, in bedded sedimentary rocks, and perhaps in sulfide minerals. Second, we will characterize trace elements in carbonate minerals, including stromatolites. We will test hypotheses on redox-sensitive element distributions and will include these geochemical data as part of the DCO-sponsored Mineral Evolution Database project to develop an open access data infrastructure to probe Earth’s changing C cycle through deep time. Third, we will collect and analyze heavy detrital grains. The study of ancient detrital zircon (and to a lesser extent monazite) grains has opened a new window on early Earth. However, other potentially revealing ancient detrital heavy minerals, such as ilmenite, rutile, cassiterite, and uraninite, have not received comparable attention. We propose to acquire and analyze suites of these heavy mineral separates from the most ancient sedimentary terrains of Western Australia. These studies will complement and amplify decades of field and analytical research, representing millions of dollars in grants for investigations of North Pole Dome geology.

Project UpdatesClick to add Project Update

Reporting Year 2014 Click to expand


  • RY2014-1 - submitted on Aug 31, 2014

    Update Details:

    4 July 2014 update

    A DCO-sponsored team led by Martin Van Kranendonk (University of New South Wales), with geochemist John Valley (University of Wisconsin), economic geologist Franco Pirajno (Geological Survey of Western Australia), and mineralogist Robert Hazen (Carnegie Institution), conducted field studies in the remote North Pole Dome area of the Pilbara Complex, Western Australia, from 17-27 June 2014. They were accompanied by several graduate students, as well as Emmy Award winning producer/director Doug Hamilton and his film crew from the celebrated NOVA TV series (WGBH, Boston).

    Van Kranendonk and colleagues focused on three DCO-related studies during the 11-day effort. First, they systematically collected samples of the oldest known unaltered primary carbonate formations, including biogenic carbonate stromatolites and abiogenic layers and cavity-filling masses of chemically precipitated carbonates. These specimens have been added to a growing collection of carbonates from around the world, spanning the past 3.5 billion years. Systematic studies of the trace and minor elements in these specimens are revealing changing near-surface environments, and associated evolution of the carbon cycle through deep time.

    A second focus of the North Pole Dome field studies was systematic collection of black, carbon-bearing chert (a form of silica deposited as veins by warm to hot hydrothermal fluids). Black chert from this region is famous for holding possible fossil microbes preserved as microscopic black spheres and filaments. Several dozen specimens will be analyzed for total organic carbon content, as well as isotopic characteristics that might be used to distinguish biogenic versus abiogenic sources of carbon. Once these specimens are surveyed, subsequent analyses will attempt to characterize the detailed nature of the organic carbon residues that produce the distinctive black color.

    Finally, in an effort to understand Earth’s varied near-surface environments at the time of life’s origins, the field team collected sandstones from a distinctive sediment horizon of the 3.5 billion-year-old formations. Similar, somewhat younger, rocks in nearby regions of Western Australia have yielded a treasure trove of ancient grains of zircon, a sturdy mineral that survives billions of years as sediment grains in much younger rocks. Individual zircon grains can be dated—some as old as 4.4 billion years provide the oldest known surviving fragments of our planet. Extending this exciting work, the DCO team will search for other distinctive “heavy detrital minerals,” each of which might reveal clues about Earth’s earliest crustal formation and evolution.

Reporting Year 2015 Click to expand


  • Update 2015: North Pole Dome, Australia - submitted on Oct 01, 2015

    Update Details:

    Submitted by M. Van Kranendonk, August 2015

    Sloan DCO supported field studies by M. Van Kranendonk of the University of New South Wales’ (UNSW) Australian Centre for Astrobiology are focused on a better understanding of the geological setting and habitat of Earth’s oldest convincing evidence of life in the North Pole Dome of the Pilbara Craton in Western Australia. This evidence occurs in the form of macroscopic stromatolites and putative microfossils from the 3.48 Ga Dresser Formation, in addition to stable isotopic evidence from sulfur and carbon isotopes.

    Previously, the geological setting was interpreted as a shallow marine embayment, whereas more recent studies by our group have identified the setting as a low-eruptive volcanic caldera with high volumes of hydrothermal fluid flow, the conduits for which are preserved as a boxwork of 100’s of chert-barite hydrothermal veins.

    Sloan DCO support has been used to fund collaborative, international field trips to the study area (2014), undertake additional detailed field mapping (field seasons in the winter months of 2014 and 2015), and conduct detailed petrography, SEM analyses, and Boron isotopic measurements on collected samples. This research has been conducted by PI Van Kranendonk and by UNSW Masters student Tara Djokic, who submitted her thesis in March 2015. Additional research was carried out in collaboration with Prof. Joachim Reitner and Dr. Jan-Peter Duda from the University of Göttingen, Germany, Prof. Eizo Nakamura from the Institute for Study of the Earth’s Interior at Okayama University, Japan, and Prof. Kathy Campbell at the University of Auckland.

    Three significant findings have resulted from this work. First is the confirmation that the Dresser Formation chert consists of four distinctive lithostratigraphic assemblages, whose thickness varies rapidly across strike as a result of active growth faulting. Stromatolites occur in lithostratigraphic assemblage 2, discontinuously across a wide area, in rocks deposited under shallow water conditions. Stromatolites consist of a wide variety of morphology including coniform, planar, and domical.

    Second is a discovery by T. Djokic as part of her Masters thesis, of laminated geyserite, deposits from a geyser consisting of very finely bedded siliceous units (50 µm scale) with small domical structures and a distinctive layering composed of alternating black and white laminae. Laminated and domical portions are very fine-grained (<10 µm), with domes separated by small troughs consisting of a distinctive, homogeneous texture of equigranular, slightly coarser-grained silica (Fig. 1a). SEM analyses indicates that the black and white layering is defined by laminae with tiny crystals of anatase (low-temperature phase of TiO2 in black laminae) and small aggregates of kaolinite-illite (white laminae) (Fig. 1b), the latter mineralogy confirmed by X-Ray Diffraction. This is significant as it precludes formation of these distinctive units through replacements of prior units and supports an origin as a hydrothermal precipitate from an active geyser. The mineralogy is consistent with that from modern hotspring systems, such as at the Soufriere Hills volcano, Monserrat (West Indies) (Boudon et al., 1998), where alternating mineralogy relates to changes in pH.

    Third is a discovery of a 2 cm thick unit of finely-laminated tourmaline-bearing ferruginous crust developed on well rounded, riverine cobbles (Fig. 2a). This crust is finely laminated and packed with tiny, euhedral, randomly oriented tourmaline crystals (Fig. 2b). Tourmaline – a boron-bearing mineral - is ONLY found in this horizon throughout the whole of the North Pole Dome succession, identifying this as an extremely unusual deposit. Tourmaline was previously identified at the same stratigraphic level in the drillcore obtained through the Dresser Formation in 2004 (Van Kranendonk et al., 2008), where it was observed to lie within pyrite. The tourmaline-bearing crust is overlain by edgewise conglomerate in which fragments of geyserite have been identified (Fig. 2c).

    Edgewise conglomerate is one in which thin fragments are packed vertically together, and they result from high energy (generally storm) events. Critically, the edgewise conglomerate clasts in the southern Dresser Formation reach dimensions of 40 cm x 10 cm x 1 cm (Fig. 3a), and some were clearly slightly soft when ripped up (Fig. 3b), suggestive of partly silicified microbial mats.

    Major-element abundances of tourmaline in the crusts were determined by using JEOL JSM-7001FL, low-vacuum FE-SEM, with Oxford INCAx-act (EDS) system at Okayama University. Elemental maps of the thin-section were obtained by using JEOL JXA-8530F, FE-EPMA. Boron isotope analysis of tourmaline was conducted according to Nakano and Nakamura (2001).

    Tourmaline compositions lie within the field of metamorphosed sedimentary rocks (pelites = metamorphosed mudstones; psammites = metamorphosed sandstones) and have remarkably homogeneous boron isotopic compositions across observed core to rim zoning of the crystals (Fig. 4).

    Boron concentration may arise from either weathering and erosion of a continental (i.e. granitic) source, or concentration within radiogenic hotsprings. Given the lack of exposed continental crust in the Pilbara older than the rocks studied here, a hotspring origin is most likely. The occurrence of the tourmaline bearing crust immediately beneath geyserite-bearing edgewise conglomerate suggests the latter and confirms the hotspring nature of the deposits at this level in the Dresser Formation stratigraphy.

    The key point with the discovery of geyserite and tourmaline-bearing hotspring crusts is that they indicate, beyond any doubt, that the Dresser Formation was actually an exposed land surface, the oldest in the world. Significantly, the Dresser Formation stromatolites occur immediately beneath this interval and suggest that they flourished exclusively in shallow water conditions and associated with hydrothermal processes.

    This is a radical departure from ideas that the origins of life originated in the deep oceans, near hydrothermal vents. Rather, the new findings from the Dresser Formation are in concert with recent studies that show that hydration (condensation) - dehydration cycles are critical for polymerization and amino acid formation in the pre-RNA world (e.g. Deamer, 2011; Walker et al., 2012), such that life most likely originated ON LAND!!!!!  

    This provides a whole new impetus and context for further studies on the Dresser Formation, particularly the distribution and concentration of elements necessary for life processes. After decades of mapping the geology and getting a handle on the complexities of that aspect, we are now refining our studies to understand the processes and reactions involved to liberate and concentrate elements required for early life processes.

     

    Figure Legends:

    Figure 1: A) Thin section view (plane polarised light) of laminated geyserite from the 3.48 Ga Dresser Formation; B) SEM analysis of geyserite, showing alternating layers defined by concentrations of Ti and of K-Al (clays). X-Ray Diffraction analysis of the Ti-bearing phase identified the mineral Anatase (low-T polymorph), whereas the clays were identified kaolinite and illite.

    Figure 2: A) Outcrop view of thinly laminated ferruginous crust on rounded riverine cobbles. B) Cross-polarised thin section view of randomly oriented tourmaline crystals from the ferruginous crust. C) Plane polarised light thin section view of tourmaline-bearing crusts overlain by edgewise conglomerate that includes ripped up clasts of laminated geyserite.

    Figure 3: Outcrop bedding plane views of A) coarse edgewise conglomerate, and B) gentle folding of soft clast.

    Figure 4: Major-element and B-isotope abundances from texturally-variable tourmalines; core (gold), sector-zoned rim (blue), and oscillatory-zoned rim (green). (a) Al-Mg-Fe ternary plot. Numbers show compositional fields of tourmalines defined by Henry and Guidotti (1985); 1, 2: Li-rich or Li-poor granitoid pegmatites and aplites. 3: Ferric ion-rich quartz tourmaline rocks (hydrothermally-altered granites). 4, 5: Metapelites and metapsammites with or without an Al-saturating phase. 6: Ferric ion-rich quartz tourmaline rocks, calc-silicate rocks and metapelites. 7: low-Ca metaultramafics and Cr,V-rich metasediments. 8: Metacarbonates and metapyroxenites.  (b) δ11B - Mg/(Fe+Mg) plot. Error bars on δ11B values correspond to reproducibilities on reference tourmaline analysis during the session (~1.2‰ in 1σ).

    Figure 5: Boron isotopic composition of Dresser Formation tourmalines, including core and texturally distinct rim zones.

     

    References

    Boudon, G., Villemant, B., Komorowski, J-C., Ildefonse, P., Semet, M.P., 1998. The hydrothermal system at Soufriere Hills, Montserrat (West Indies): Characterisation and role in the ongoing eruption. Geophysical Research Letters, v. 25, p. 3693-3696.

    Deamer, D., 2011. First Life. University of California Press, California, USA, 272p.

    Henry, D.J. and Guidotti, C.V., 1985. Tourmaline as a petrogenetic indicator mineral - an example from the staurolite-grade metapelites of NW Maine. American Mineralogist, 70(1-2), 1–15.

    Nakano, T. and Nakamura, E. (2001). Boron isotope geochemistry of metasedimentary rocks and tourmalines in the subduction-zone metamorphism. Physics of Earth Planetary Interiors, 127, 233–252.

    Van Kranendonk, M.J., Philippot, P., Lepot, K., Bodorkos, S., Pirajno, F., 2008. Geological setting of Earth’s oldest fossils in the c. 3.5 Ga Dresser Formation, Pilbara Craton, Western Australia. Precambrian Research 167, 93-124. doi. 10.1016/j.precamres.2008.07.003.

    Walker, S.I., Grover, M.A., Hud, N.V., 2012. Universal Sequence Replication, Reversible Polymerization and Early Functional Biopolymers: A Model for the Initiation of Prebiotic Sequence Evolution. PLOS One, DOI: 10.1371/journal.pone.0034166

Reporting Year 2016 Click to expand


  • Update 2016: North Pole Dome, Australia - submitted on ,

    Update Details:

    Sloan DCO support has been used to undertake detailed field mapping of the study area (field seasons in the winter months of 2015 and 2016), and conduct detailed petrography, SEM analyses, and Boron isotopic measurements on collected samples. We discovered a variety of new hotspring facies deposits from throughout the Dresser Formation. Detailed mapping of the orientation of hydrothermal veins S. Tadbiri has shown that the vein array is composed of six different sets, five of which were emplaced during periods of surface uplift and subsidence during sediment accumulation, and the last of which was active during collapse of the surface environment during the last stages of sedimentation and continuing on into the overlying period of basaltic volcanism. We discovered a new form of microbialites in the Dresser Formation, consisting of hematitic dendrites in a layer only 3 cm thick, lying directly above the mineralised remnants of a hotspring pool and interbedded with siliceous sinter and geyserite. We completed and published a detailed study of organic matter found in the hydrothermal veins and bedded cherts, using in situ Secondary-Ion Mass Spectrometry (Morag et al., 2016). And, we collected a suite of samples from along the length of a 1 km deep hydrothermal vein, as well as across its width in several places.
    Sloan funds were also used to travel to New Zealand in February 2016 to participate in a fieldtrip to see the active hotsprings of New Zealand, guided by Prof. Kathy Campbell, a world expert on hotsprings. On this trip was Dr Steve Ruff (Arizona State University), the key proposer of a landing site for Mars 2020 at the opaline silica hotspring deposits of Columbia Hills, discovered by the Spirit Rover. He is using our work on Dresser Formation to guide thinking of the landing site group, and we have been invited to actively participate in this process. Van Kranendonk was invited to speak at a NASA Biosignatures Mars workshop held in Lake Tahoe in May 2016, where he presented the results of or work on the Dresser Formation and the implications this had for the search for life on Mars.
    Two new peer-reviewed papers were published or submitted on related research over the past year, together with a Scientific American article on origin of life in geothermal hot springs, which is in review. 
    In-kind support, via personnel efforts not funded by Sloan, provided about 7:1 leverage on the Sloan grant funds for this Field Site.
  • Life on Land Dates Back to 3.5 Billion Year Old Hot Springs - submitted on ,

    Update Details:

    The Dresser Formation in Western Australia contains evidence of some of the earliest signs of life, dating back almost 3.5 billion years. In the 1970s, scientists discovered the remains of layered microbial mats called stromatolites there, which they thought had formed within an ancient volcanic caldera, submerged under seawater. New research, however, suggests that these early cells thrived not under the ocean, but rather on land, within hot springs.

    Martin Van Kranendonk, a member of DCO’s Deep Life and Extreme Physics and Chemistry Communities, Tara Djokic, a member of the Deep Life Community (both of University of New South Wales, Australia), and colleagues discovered microbial biosignatures and minerals matching modern hot spring environments within the Dresser Formation. These findings, which researchers report in a new paper in the journal Nature Communications, suggest that microbial life in hot springs existed about 3 billion years earlier than previously known.

    Read more.

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