Some modern filamentous oxygenic photosynthetic bacteria (cyanobacteria) form macroscopic tufts, laminated cones and ridges that are very similar to some Archean and Proterozoic stromatolites. However, it remains unclear whether microbes that constructed Archean clumps, tufts, cones and ridges also produced oxygen. Here, we address this question by examining the physiology of cyanobacterial clu...

We do not have a detailed knowledge of the processes that led to the appearance of life on Earth. In this review we bring together some of the most important results that have provided insights into the cosmic and primitive Earth environments, particularly those environments in which life is thought to have originated. To do so, we first discuss the evidence bearing on the antiquity of life o...

The evolution of O(2)-producing cyanobacteria that use water as terminal reductant transformed Earth's atmosphere to one suitable for the evolution of aerobic metabolism and complex life. The innovation of water oxidation freed photosynthesis to invade new environments and visibly changed the face of the Earth. We offer a new hypothesis for how this process evolved, which identifies two critica...

The Isua Supracrustal Belt, Greenland, of Early Archean age (3.81-3.70 Ga) represents the oldest crustal segment on Earth. Its complex lithology comprises an ophiolite-like unit and volcanic rocks reminiscent of boninites, which tie Isua supracrustals to an island arc environment. We here present zinc (Zn) isotope compositions measured on serpentinites and other rocks from the Isua supracrustal...

The Paleoproterozoic Lomagundi Event is an interval of 130-250 million years, ca. 2.3-2.1 billion years ago, in which extraordinarily (13)C enriched (>10‰) limestones and dolostones occur globally. The high levels of organic carbon burial implied by the positive δ(13)C values suggest the production of vast quantities of O2 as well as an alkalinity imbalance demanding extremely low levels of wea...

It has been hypothesized that before the emergence of modern DNA-RNA-protein life, biology evolved from an "RNA world." However, synthesizing RNA and other organophosphates under plausible early Earth conditions has proved difficult, with the incorporation of phosphorus (P) causing a particular problem because phosphate, where most environmental P resides, is relatively insoluble and unreactive...

25 26 The Tropicana gold deposit is located adjacent to the margin of the Yilgarn craton in 27 the Albany–Fraser orogen, Western Australia. The deposit is hosted in granulite facies 28 quartzo-feldspathic gneisses of the Archean Tropicana Gneiss. Ore bodies comprise 29 biotite-pyrite alteration concentrated in shear zones that formed during NE-SW 30 shortening in the late Archean, and clearly p...

Single zircon dating of the Rampur metabasalts of the Larji–Kullu–Rampur window in the Lesser Himalayas yielded an evaporation age of 1800913 Ma. The zircon age is considerably younger than the previously published whole rock Sm–Nd age of 2510990 Ma, suggesting that the Sm–Nd age may be geologically meaningless and that the Sm–Nd whole rock array may have resulted from mixing. In the NW Himalay...

The behavior of C, H, and S in the solid Earth depends on their oxidation states, which are related to oxygen fugacity (fO2). Volcanic degassing is a source of these elements to Earth's surface; therefore, variations in mantle fO2 may influence the fO2 at Earth's surface. However, degassing can impact magmatic fO2 before or during eruption, potentially obscuring relationships between the fO2 of...